Elevator systems require robust operation monitoring to ensure safety, performance, and effective fault detection, particularly in environments where sensor configurations may evolve over time. Traditional approaches often rely heavily on expert knowledge and rule-based systems, limiting scalability and responsiveness. With the advent of IoT technologies, real-time data collection and intelligent fault analysis have become both feasible and effective. To address these limitations, we present ElevatorTalk-M, an IoT-based elevator operation monitoring system that introduces a novel finite state machine (FSM)-based framework capable of dynamically generating operational models for arbitrary sensor configurations. Building on the earlier ElevatorTalk platform, ElevatorTalk-M enables sensors to be added or removed transparently while maintaining accurate and consistent operational modeling, a capability that is not available in existing smart elevator solutions and is particularly beneficial for legacy elevators. Experimental results show that all door obstruction events are successfully detected with an average detection time of 0.1 seconds. We further provide a formal correctness proof of the proposed fault detection algorithm. By integrating an auxiliary vibration sensor, the system can significantly enhance detection reliability, reducing the detection error from 0.18% to 0.0054%. These results demonstrate that ElevatorTalk-M offers a scalable, interpretable, and resilient solution that reduces reliance on domain experts while improving real-time elevator operation monitoring.

Ensuring clean water availability is critical for sustainability and health. Conventional water quality assessments are limited by manual sampling, poor temporal resolution, and centralized data processing. This study proposes HydroFedNet, a multisource water quality monitoring framework that uses Federated Learning (FL) to integrate diverse data sources, including LANDSAT satellite imagery, RGB pond images, and Internet of Things (IoT) sensor streams. The spatio-spectral transfer learning network (Spatio-Spectral TLNet), the color transfer learning network (Color TLNet) and the sensor convolutional neural network - temporal convolutional network (Sensor CNN - TCN) are fundamental models for HydroFedNet. Spatio-Spectral TLNet and Color TLNet leverage EfficientNetB3 for optimized, low-cost training, while Sensor CNN–TCN exploits improved temporal modeling. Models are trained locally and share weight updates with a central server, which builds a global model using the chosen FL strategy. FL strategies such as Federated Averaging (FedAvg), FL with Temporally Aware aggregation (FedLTA), and Federated Optimization (FedOpt) are evaluated with six objectives, including energy efficiency, fault tolerance, and handling of non-independent and identically distributed (non-IID) data. FedLTA surpasses the 90% accuracy across all three models with less communication overhead, whereas FedOpt effectively handles non-IID data. HydroFedNet allows an optimal selection of an intent-aware FL strategy, allowing robust, scalable, and efficient water quality monitoring across heterogeneous environments.

Millimeter-wave (mmWave) small base stations (SBSs) enhance indoor 5G heterogeneous network by delivering high-speed wireless access and offloading macro base station (MBS) traffic. Due to the limited range of mmWave signals, dense yet often noncontinuous SBS deployments are required, leading to energy inefficiencies—especially during low-traffic periods—because of high-power consumption. To address this, traffic-aware sleep strategies dynamically switch SBSs between active and sleep modes. However, most analytical models assume continuous coverage, limiting their real-world applicability. This article proposes an analytical model tailored to noncontinuous mmWave SBS deployments, evaluating three metrics: 1) the proportion of SBSs in sleep mode; 2) the traffic offloading ratio; and 3) the frequency of discovery broadcasts during sleep. Simulation results validate the model under varying deployment and traffic scenarios, demonstrating its value in supporting energy-efficient design for indoor 5G networks.

In organizations adopting Internet of Things (IoT) solutions, managing diverse systems with incompatible APIs poses significant challenges to sustainability and social responsibility. To address this, we introduce AUtalk, an artificial intelligence (AI)-enhanced integrated operations center (IOC) framework for centralized management of heterogeneous IoT systems. AUtalk offers a low-code, no-code environment for seamless IoT integration, enabling applications that support sustainable development goals (SDGs). Deployed in smart campuses, it optimizes resources, conserves energy, and reduces waste through AI-driven insights. Its predictive capabilities enhance maintenance efficiency and minimize resource consumption (SDG 12). Beyond sustainability, AUtalk enhances social responsibility by improving workplace safety, system transparency, and accountability. Its advanced analytics ensure over 99% message delivery accuracy, reducing downtime and resource waste. A case study of an AUtalk-managed IOC with two IoT systems highlights its effectiveness in promoting sustainability and responsible IoT operations.

Existing non-image-based solutions for detecting Phalaenopsis orchid diseases rely on time domain analysis of environmental conditions. These solutions are suitable for loosely controlled open farm fields. Conversely, the diseases are infrequent events in Internet of Things (IoT)-based smart orchid greenhouses, where environmental conditions are well-controlled. In tightly controlled settings, standard time domain methods fall short in detecting subtle changes in environmental conditions during rare orchid disease events. We observed that the influence of the time series of temperature and humidity on orchid fungus within the well-controlled greenhouse is not readily apparent, and the time-frequency coefficients of temperature and humidity must be used to detect orchid disease in this rare event case. In order to address this challenge, we propose OrchidTalk, an IoT-based deep learning platform, which employs a time-frequency domain analysis using the Continuous Wavelet Transform (CWT) filter, for the purpose of detecting rare events of orchid diseases. Through a non-trivial process, we select the Gaussian wavelet with four derivatives to serve as the mother wavelet of the CWT in the data extraction phase, and invent the CWT IoT device to translate the time-domain IoT raw data to the time-frequency domain IoT data. The resulting CWT features are used as inputs to the Orchid-3D model (three-dimension ConvLSTM), which significantly outperforms the previously proposed Orchid-1D (CNN and LSTM) and Orchid-2D (two-dimension ConvLSTM) models. For the rare event detection of 0.2% of sick orchid plants, OrchidTalk achieves a recall of 0.902, precision of 0.92, accuracy of 0.99, and an F1-score of 0.911. To the best of our knowledge, this represents the highest prediction performance achieved for a well-controlled orchid greenhouse.

This article proposes StrawberryTalk, an Internet of Things (IoT) platform for image-based strawberry disease detection. StrawberryTalk reuses the wall-mounted monitoring cameras without extra hardware cost. The contributions of StrawberryTalk are the utilization of IoT for automatic photo shoot and the wind detection mechanism to eliminate the obscure photos due to the wind effects. Also, the data preprocessing and the infection detection models are manipulated as IoT devices to simplify the implementation of the multicascade artificial intelligence (AI) models. We derive the relationship between the camera zoom factor and the distance between the camera and the strawberries for optimal disease detection. Accuracy of detection may be affected by obscure photos. In terms of eliminating obscure photos due to wind effect, we analytically derive the relationship between the wind alert delay and the number of obscure photos that must be retaken. For the greenhouses in the Bao Mountain, we only need to retake one photo. Based on the experiments, the mean average precision (mAP) of StrawberryTalk (to detect exact spots in a leaf) can be up to 92.37%, which is better than the previous approaches. To detect if a pot has infected leaves, the accuracy of StrawberryTalk can be up to 97.92% at the zoom factor$30\times $. In commercial operation, it is important to detect all infected strawberry pots. StrawberryTalk is able to detect all infected pots (i.e., recall is 100%) with a camera of zoom factor of$12\times $. The accuracy is 96.88%.

The Bacillus genus is one of the most commercially exploited bacteria in the agro-biotechnology industry, and the Bacillus information is very useful for crop growth. Most existing studies on the analysis of the amount of Bacillus were conducted in laboratories. Performing such a task on open field farming is difficult because only a small data set is available during a long observation period for the soil analysis of Bacillus. For example, turmeric growth takes nine months with one soil sample per month, and we found that increasing the frequency of soil analysis for turmeric growth is not practically useful. Therefore, we can only collect a very small data set for AI training. This article proposes the AgriTalk approach that predicts the amount of Bacillus based on novel IoT and machine learning technologies. AgriTalk uses a small data set (five data items) per farm for training and performs prediction for the subsequent four months. Good results are obtained. Specifically, the inference mean absolute percentage errors (MAPEs) range from 6.73% to 19.76%. In the experiments of five farm fields, we have correctly captured the trends for the number of changes of Bacillus. Such prediction provides useful information for fertilization management. Our prediction is more accurate for farms covered by peanut shells (the average MAPE is 13.24%) than for farms covered by rice husks (the average MAPE is 15.43%).

All six papers in this special section engage in different streams but extremely relevant domain vectors of Cognitive Cyber-Physical Systems (CCPS) with artificial intelligence (AI) based solutions in medical informatics. Highlights recent trends in the scientific community and presents emergent technologies, implementations, applications concerning the CPSS. CPSS is witnessing rapid transformation as an interdisciplinary technology that blends physical components and computing devices to enable AI-based solutions. CCPS will be playing a significant role that integrates machine learning/AI techniques and resulting in dramatic improvements for medical informatics and the future of human-augmentation. CPHMS coordinates supervisory medical systems and medical resources everywhere; there is a great scope towards health consciousness and healthy society. Medical Cyber-Physical Systems (MCPS) in healthcare towards critical integration in network of medical devices. MCPS is the next generation computing that is comprised of tightly coupled computational and communication components of medical automation systems such as clinical decision, early detection of health infectious, disease prevention, rapid analysis of health hazards and so on. CCPS and MCPS research would be created new models, new design, and integration models for large scale systems in comprehensive, holistic medical automation systems. With recent enlargements in the big data processing, cognitive data science and AI, it is now possible to create even more realistic digital twins that properly model different operating situations and characteristics to process the medical intelligence systems.

Federated learning (FL) provides a promising way to train a machine learning model among mobile devices without collecting their raw data to a central node. During training, proper devices are selected to participate in the training process to avoid model unfairness. In a mobile edge network, participant selection must be considered together with three factors: non-iid datasets possessed by devices, tunable local iterations on devices, and radio resource allocation to counter the impact of time-varying channel conditions on parameter transmissions. Since datasets of devices are given, to ensure model fairness and achieve fast convergence in the FL training process, participants, local iterations, and radio resources must be scheduled jointly in each iteration of FL training. In this paper, the joint scheduling problem is analyzed and formulated. Since it is NP-hard, a heuristic scheduling method called PALORA is designed to conduct joint scheduling of participants, local iterations, and radio resources. PALORA consists of three sequentially interactive function blocks: 1) a pointer network embedded deep reinforcement learning method to select participants, 2) an estimation algorithm to determine the numbers of local iterations, and 3) a breadth-first search method to allocate radio resources to the selected participants. PALORA is evaluated via extensive simulations based on real-world datasets. Results show that it significantly outperforms benchmark approaches.

The voice-based Internet of Multimedia Things (IoMT) is the combination of IoT interfaces and protocols with associated voice-related information, which enables advanced applications based on human-to-device interactions. An example is Automatic Speech Recognition (ASR) for live captioning and voice translation. Three major issues of ASR for IoMT are IoT development cost, speech recognition accuracy, and execution time complexity. For the first issue, most non-voice IoT applications are upgraded with the ASR feature through hard coding, which are error prone. For the second issue, recognition accuracy must be improved for ASR. For the third issue, many multimedia IoT services are real-time applications and, therefore, the ASR delay must be short. This article elaborates on the above issues based on an IoT platform called VoiceTalk. We built the largest Taiwanese spoken corpus to train VoiceTalk ASR (VT-ASR) and show how the VT-ASR mechanism can be transparently integrated with existing IoT applications. We consider two performance measures for VoiceTalk: speech recognition accuracy and VT-ASR delay. For the acoustic tests of PAL-Labs, VT-ASR's accuracy is 96.47%, while Google's accuracy is 94.28%. We are the first to develop an analytic model to investigate the probability that the VT-ASR delay for the first speaker is complete before the second speaker starts talking. From the measurements and analytic modeling, we show that the VT-ASR delay is short enough to result in a very good user experience. Our solution has won several important government and commercial TV contracts in Taiwan. VT-ASR has demonstrated better Taiwanese Mandarin speech recognition accuracy than famous commercial products (including Google and Iflytek) in Formosa Speech Recognition Challenge 2018 (FSR-2018) and was the best among all participating ASR systems for Taiwanese recognition accuracy in FSR-2020.

Air and soil sensors are used in smart agriculture to autonomously collect the soil-related data. It is important that the measurements of the sensors are accurate. This article uses electrical conductivity (EC) as an example to show how to avoid the inaccuracy due to EC sensor aging. We consider a promising solution that packagesIredundant EC sensors in one device (${I}>{1}$) called${I}$-redundant EC sensor package. The redundant-sensor package outputs the measured data based on a voting process among${I}$sensors, which makes soil measurement more accurate and reliable. Based on the${I}$-redundant EC sensor package, this article invents the first out-of-the-laboratory automatic calibration procedure in the farm field. We also propose the SensorTalk mechanism to extend the life of the${I}$-redundant EC sensor package through calibration. Most people have the illusion that the life of a redundant-sensor package is longer than a nonredundant sensor. This article proves that the life of a redundant-sensor package is shorter than its nonredundant counterpart. Then, we propose the self-calibration process of the redundant-sensor package to extend its operation life. For example, if the life of a sensor in the${I}$-redundant package is six months with the aging-after-calibration factor${\gamma }={0}.{9}$, then SensorTalk may extend its life to 52.2 months for${I}={9}$. We also shed some nontrivial insights. In many smart farming solutions, the sensors typically report the measured data with a frequency lower than one per 10 min. Our study indicates that by increasing the sampling frequency up to one per 20 s, calibration for an EC value can be sped up by 19 times. Our study also suggests that an oddInumber should be chosen. If we add one more sensor to make an even${I}$number, the life of the redundant-sensor package is actually shortened.

This article proposes EduTalk, an out-of-the-box Internet of Things (IoT)-based smart learning environment for programming education. In particular, EduTalk enables the students to write VPython programs that render 3-D animations in the browser without installing extra software or using any specific (and typically expensive) hardware. EduTalk takes the user’s smartphone as a controller for cyber–physical interaction, which nicely integrates with learning of other core courses such as physics and mathematics. EduTalk allows building science exhibition projects by writing VPython programs to show 3-D animation, where the cost for EduTalk’s cyber–physical interaction is low and is almost maintenance free. The major contribution of this article is the IoT-based EduTalk proposal that subtly utilizes an IoT platform IoTtalk to conveniently generate cyber–physical interaction for learning how to program as well as learning core courses such as physics. The programming exercises can be easily extended to science exhibition projects and then the development of digital twin applications. A mechanism is provided to easily integrate GlowScript animation demos with EduTalk, which significantly simplifies the effort for teachers to prepare the lecturers. Finally, we show how data collected from EduTalk can be analyzed to improve learning design for cyber–physical interactive animation.

As car hire and sharing service is popular in the transportation market, secure driver identity verification is attracting more attention. However, the current verification mechanism focuses on performing authentication operations in the cloud server before drivers get access to the car, which results in potential privacy security issues. In this article, we present a privacy-aware architecture, MobiDIV, which is a client-only scheme, where all sensitive data are processed locally on the driver’s smartphone. To achieve real-time and robust driver identification during the driving life cycle, an efficient face feature extractor is proposed in MobiDIV. Specifically, two three-stream neural networks using the proposed efficient SqueezeNet structure are trained on our synthesized data set for different in-car uncertainties (pose, motion blur, nonalignment and low illumination). During authentication, only an adaptable embedding model is selected and conducted on phone for continuous feature extraction. The anomaly operation monitoring algorithm is then applied to the optical signal generated by phone flash for secure identity reidentification and verification failure message transmission. This allows us to further ensure the privacy of driver facial images without compromising on the real-time identity verification. We perform extensive experiments on various data sets. Compared to most SOTA deep neural networks on real-world open data sets, we achieve similar verification accuracy with fewer parameters and floating-point calculations. On the challenging synthetic test data sets, we even achieve a higher average verification accuracy. To assess the MobiDIV in-depth, the proposed model is integrated in car-sharing platform ICICV-E100 and the obtained results show the feasibility of our system.

Real-time control solutions for unmanned aerial vehicles (UAVs) have attracted great interest in recent years. Most existing control methods use Wi-Fi technology. While Wi-Fi is inexpensive and easy to use, it has only a limited transmission range. Thus, 4G/5G cellular networks have been proposed as an alternative enabling technology. This study focuses on the problem of improving the appropriateness of the control commands sent by the ground control station (GCS) to the UAV over the control and nonpayload communication (CNPC) link of the UAV through the cellular network. To satisfy the low-latency requirement of the CNPC link, multiaccess edge computing (MEC) technology is leveraged to collocate the GCS and base station. The effectiveness of the proposed edge-based approach is demonstrated by conducting experiments on two LTE platforms with different MEC deployment methods. An edge-enabled UAV control solution is proposed in which each end-to-end control delay in the UAV-GCS system is estimated based on the preceding delay such that the location of the UAV at the moment it receives the control command from the GCS can be predicted in advance and taken into consideration by the GCS when formulating an appropriate control decision. To this end, an analytical modeling method is proposed for estimating the expected error range of each control delay based on a bimodal distribution approximation of the empirical control delays observed at the UAV. Finally, an event-driven simulator is developed to confirm the accuracy of the analytical predictions of the control delay based on the expected error between consecutive delays.

With the rapid increase of the industrial data and the development of the industrial Internet of Things (IIoT) paradigm, the efficiency and the quality of service of the emerging applications have been improved. However, the contradiction between data sharing and privacy preserving is still an obstacle in the IIoT. To this end, in this article, we propose a privacy-preserving and publicly auditable multiparty computation scheme for industrial data sharing and computing, which avoids privacy leakage and computation misbehavior by separating the data ownership, data use, and data verification. Using the blockchain technology, a transparent management platform is provided to recognize and trace the illegal data and computation behavior. Moreover, we integrate the noninteractive zero-knowledge proof in the multiparty interaction mechanism, wherein the verification of data consistency and computation validity is executed publicly on the blockchain. Finally, we implement experiment to evaluate the performance of the computation latency, communication overhead and the influence of encryption parameter, and the numerical results illustrate the efficiency and feasibility of our scheme.

At present, drone delivery systems usually function only in global positioning system (GPS)-friendly environments and thus cannot deliver goods into customers’ houses, which is an element of urban last-mile delivery. In this study, we investigated solutions for enabling drones to fly autonomously in mixed indoor–outdoor environments. We propose a novel Internet of Things (IoT)-based drone delivery system, namely DroneTalk, for mail delivery. DroneTalk combines a GPS, an inertial measurement unit, and visual information to achieve mixed indoor–outdoor autopilot operation. Furthermore, DroneTalk integrates an autonomous drone control system with an IoT device management platform to enable a drone to achieve automatic online weather awareness. Most importantly, DroneTalk is a novel work considering communication, processing, and control latencies simultaneously during autopilot operation to avoid problems related to drone collisions. These problems have always existed but become more serious when drones are flying close to buildings. Simulation results indicate that the proposed system can attain a high user-defined flight success rate (i.e., 99% in our simulations) without any collisions; thus, the proposed system can be feasibly used in real-world environments.

Sensor failure detection and calibration is an important issue for Internet of Things applications. Many smart applications fail due to inaccurate data produced by their sensors. To solve this issue, we propose the CalibrationTalk mechanism. We use smart agriculture as an example to show how CalibrationTalk automatically fixes the sensing accuracy problems in commercial farm operations. Besides manufacturing variation, hardware malfunction and aging, sensing inaccuracy may be caused by soil erosion of rain or irrigation, which changes the positions and the angles of the sensors inserted in the soil. The above sensor failure problems can be detected by CalibrationTalk. In this article, we first extend our previous work to detect sensor failures. If the sensors become inaccurate due to aging or similar reasons, CalibrationTalk automatically calibrates the sensors in the farm fields. We conduct measurements and analytic modeling to investigate the performance of CalibrationTalk, which suggests that to detect a potential moisture sensor failure, it is appropriate to set the detection time as 30 min for moisture sensors. With this setup, true failure is detected while false detections rarely occur. For a detected sensor failure due to aging, CalibrationTalk can automatically build a calibration table. During the calibration table establishment period, the sensors still produce correct measured data and do not interfere with the normal operation of smart farming. The value of CalibrationTalk lies in its power of automation for sensor failure detection and calibration processes developed in this article.

Multisensor data fusion combines various information sources to produce a more accurate or complete description of the environment. This article studies an object identification (OID) system using multiple distributed cameras and Internet-of-Things (IoT) devices for better visualizability and reconfigurability. We first propose a data processing and fusing method to merge the detection results of different IoT devices and video cameras, in order to locate, identify, and track target objects in the monitored area. Then, we develop the FusionTalk system by integrating the data fusion techniques with IoTtalk, an IoT device management platform. FusionTalk is designed with flexibility, modularity, and expansibility, where cameras, IoT devices, and network applications are modularized and can be conveniently plugged in/out, reconfigured, and reused through graphical user interfaces. In FusionTalk, the scope and the target of surveillance can be flexibly configured and associated, and administrators can be warned and easily visualize the movement and behavior of specific objects. Our experimental evaluation of the data fusion algorithm in various scenarios shows an identification accuracy above 95%. Finally, theoretical and numerical analyses on the failure probability of pairing IoT devices with video objects by FusionTalk are presented. Extensive experiments are performed to demonstrate the pairing effectiveness in real-world scenarios with failure probability less than 0.01%.

On pig farms, many piglets die because they are crushed when sows roll from side to side or lie down. On average, 1.2 piglets are crushed by sows every day. To resolve the piglet mortality issue, this article proposes PigTalk, an artificial intelligence (AI) based Internet of Things (IoT) platform for detecting and mitigating piglet crushing. Through real-time analysis of the voice data collected in a farrowing house, PigTalk detects if any piglet screaming occurs, and automatically activates sow-alert actuators for emergency handling of the crushing event. We propose an audio clip transform approach to pre-process the raw voice data, and utilizes min-max scaling in machine learning (ML) to detect piglet screams. In our first contribution, the above data preprocessing method together with subtle parameter setups of the machine learning model improve the piglet scream detection accuracy up to 99.4%, which is better than the previous solutions (up to 92.8%). In our second contribution, we show how to design two cyber IoT devices, i.e., DataBank for data pre-processing and ML_device for real-time AI to automatically trigger actuators such as floor vibration and water drop to force a sow to stand up. We conduct analytic analysis and simulation to investigate how the detection delay affects the critical time period to save crushed piglets. Our study indicates that PigTalk can save piglets within 0.05 s with 99.93% of the successful rate. Such results are validated in a commercial farrowing house. PigTalk is a new approach that automatically mitigates piglet crushing, which could not be achieved in the past.

The new frontier research era and convergence of cognitive data science methods and models with reference to the Internet of Things (IoT) and big data systems have brought about various challenges in industrial systems that need to be addressed in the current scenario. Cognitive science will lead to a high level of fluidity to analytics. This special section aims to explore the domain knowledge and reasoning of data science technologies and cognitive methods with the IoT over the big data systems. Data science techniques have been adopted to improve the IoT in terms of data throughput, optimization, and management, and to have a major impact on the future of IoT networking systems. The main focus is the design of best cognitive embedded data science technologies to process and analyze the large amount of data collected through industrial IoT systems and help for good decision making.

Graphical Internet of Things (IoT) device management platforms, such as IoTtalk, make it easy to describe interactions between IoT devices. Applications are defined by dragging-and-dropping devices and specifying how they are connected, e.g., a door sensor controlling a light. While this allows simple and rapid development, it remains possible to specify unwanted device configurations, such as using the same device to drive a motor up and down simultaneously, risking damaging the motor. We propose BigraphTalk, a verification framework for IoTtalk that utilizes formal techniques, based on bigraphs, to statically guarantee that unwanted configurations do not arise. In particular, we check for invalid connections between devices, as well as type errors, e.g., passing a float to a Boolean switch. To the best of our knowledge, BigraphTalk is the first platform to support the graphical specification of correct-by-design IoT applications. BigraphTalk provides fully automated verification and feedback without end-users ever needing to specify a bigraph. This means that any application, specifiable in IoTtalk, is guaranteed, so long as verification succeeds, not to violate the given configuration constraints when deployed; with no extra cost to the user.

Rice blast is one of the most serious plant diseases. Many rice blast management approaches require know-how of experienced farmers or agronomists. Monitoring the farm for disease detection is labor intensive and time consuming. By using the Internet of Things (IoT) and artificial intelligence (AI), we are able to detect plant diseases more efficiently. Existing AI and IoT studies detect plant diseases by images or nonimage hyperspectral data, which require manual operations to obtain the photographs or data for analysis. Also, image detection typically is too late as rice blast may already spread to other plants. Based on an IoT platform for soil cultivation, we develop the RiceTalk project that utilizes nonimage IoT devices to detect rice blast. Unlike the image-based plant disease detection approaches, our agriculture sensors generate nonimage data that can be automatically trained and analyzed by the AI mechanism in real time. The beauty of RiceTalk is that the AI model is treated as an IoT device and is managed like other IoT devices. In this way, our approach significantly reduces the platform management cost to provide real-time training and predictions. We also propose an innovative spore germination mechanism as a new feature extraction model for agriculture. In the current implementation, the accuracy of the RiceTalk prediction on rice blast is 89.4%.

Internet of Things (IoT) has been widely utilized with artificial intelligence (AI). However, it requires substantial effort to integrate AI and big data with IoT. To mitigate this problem, AItalk was proposed. By treating AI as a cyber IoT device, we do not need to write code of the AI mechanism in the network applications, as traditional AI-based IoT applications did. This article describes how the AI tools such as scikit-learn and TensorLayer are accommodated as cyber IoT devices in AItalk, and extends AItalk for non-IoT applications. We use house valuation as an example to show how AItalk can flexibly include the factors that have significant impact on the house price. We show that by adding extra features other than housing profile features, the accuracy for the prediction (valuation) can be improved by 38%. We also investigated the communication overhead of the distributed AItalk structure, which is 3.7% for the computation of one house price valuation.

Metering the traffic of a flow and dropping the portion of traffic that exceeds the target rate set by the meter is very important to provide quality of service (QoS) in a network. Most existing switches on the market provide the meter function. Although these meters regulate the traffic of a UDP flow very well, according to our tests, they are not TCP-friendly. For example, we found that a TCP flow passing the meter of a commercial switch can only achieve about 10% of the target rate. Based on our studies, we found that this poor performance is due to the bad interactions between the TCP congestion control and the meter function. In this paper, we design and implement a TCP-friendly meter in the packet processing pipelines of a P4 switch. Experimental results show that our meter regulates a TCP flow very well and can maintain its achieved rate within 5% of the target rate. Compared with the meters in several hardware switches, our meter improves the achieved rate of a TCP flow by almost 85% of the target rate.

Tracking the rules matched by the packets of a flow when they traverse multiple switches in a network is very important and useful. In this paper, we design and implement a bandwidth- efficient In-Band Network Telemetry (INT) system that can track the rules matched by the packets of a flow in real time or in the past. We have evaluated the real performance of our system on a testbed composed of several hardware P4 switches. Our experimental results show that the system works correctly and its traffic reduction scheme can reduce the rate of generated INT reports by a factor of 39, 394, 2,055, or even up to 12,500, depending on the type of network states monitored and the threshold used to filter out less important INT reports.

This paper proposes AgriTalk, an inexpensive Internet of Things (IoT) platform for precision farming of soil cultivation. We conduct experiments on turmeric cultivation, which indicates that the turmeric quality is significantly enhanced through AgriTalk. Specifically, the curcumin concentration is up to 4500-5500 mg/100 g, which is five times more than existing products. We demonstrate how to intuitively configure the connections between the sensors and the actuators with the desired farming intelligence, and to effectively maintain AgriTalk for precision farming. We conduct measurement, analytic analysis, and simulation experiments to investigate the IoT message delays of AgriTalk. This paper indicates that the delays for automatic control and automatic-manual control switching with long distances (more than 30 km) are very short (less than 0.2 s) and AgriTalk can easily respond to quick and dynamic change of the field environment conditions in soil cultivation.

Narrowband Internet of Things (NB-IoT) is considered as a promising wireless communications technology for Internet of Things (IoT) especially for the outdoor environment. Many outdoor IoT applications involve large numbers of homogeneous NB-IoT devices. It is tedious to specify and accommodate these devices during application development. To resolve this issue, this paper proposes a service platform for fast development of NB-IoT applications called NB-IoTtalk. This platform utilizes a tag mechanism to provide an easy-to-manipulate graphical user interface to accommodate a large number of NB-IoT devices in an application and transparently show them in a visual map. Our approach automatically creates and parses the device profile used to interpret the payload of an NB-IoT message. We then use a smart parking lot application as an example to investigate the event-triggered reporting of NB-IoT in terms of the time-to-live (TTL) report frequency and the outage detection accuracy. This paper provides the guidelines to set the TTL interval for event-triggered NB-IoT applications.

To avoid distributed denial-of-service (DDoS) attacks or real-time transmission control protocol (TCP) incast in the software-defined networking (SDN) environment, the HashPipe algorithm was developed following the space-saving approach. Unfortunately, HashPipe implemented in the behavioral model (bmv2) cannot be directly executed at a real programming protocol-independent packet processor (P4) switch due to P4 pipeline limitation. Based on the Banzai machine model, this paper shows how to smartly utilize the Banzai atoms to develop HashPipe as a soft computing application in a real P4 switch. Then we propose an enhanced HashPipe algorithm that significantly improves the accuracy of the original HashPipe. The proposed heavy hitter detection is executed at the line-rate of the Tofino P4 switch with the highest process rate in the world.

Multi-sensorial effect or four-dimensional (4-D) effect is considered in the niche arena of film playing but has become a growing business quickly. Installation of 4-D effects are typically expensive, and 4-D films are most often presented in custom-built theaters at special venues. This paper proposes a novel integration of existing video service platform and commercial smart home solution to generate 4-D effects for any non-4-D film (i.e., a 3-D or a 2-D film). Specifically, we describe how the designer can use home appliances to create the effects for a 4-D experience theater at home. Instead of using an expensive and special 4-D movie effect system, we use a low-cost off-the-shelf IoT platform for a smart home to create the 4-D movie effects for any non-4-D film. Therefore, the viewer can enjoy 4-D movies at home without special equipment other than home appliances. In our solution, an IoT device-management system called IoTtalk is utilized to integrate the video service system and the smart home system. Since these systems may be located in distant places, the delays for video streaming and triggering of 4-D effects must be synchronized. We have conducted measurements to indicate that in our design, the synchronization issue can be ignored without affecting the user experience.

Software Defined Network separates the control plane from network equipment and has great advantage in network management as compared with traditional approaches. With this paradigm, the security issues persist to exist and could become even worse because of the flexibility on handling the packets. In this paper we propose an effective framework by integrating SDN and machine learning to detect and categorize P2P network traffics. This work provides experimental evidence showing that our approach can automatically analyze network traffic and flexibly change flow entries in OpenFlow switches through the SDN controller. This can effectively help the network administrators manage related security problems.

As physical obstacles, vehicles have a significant impact on the efficient propagation of safety-related information in vehicular ad hoc networks (VANETs) by frequently obstructing the LOS link between the source and receivers. Obstructing effect of vehicles will diminish the effective coverage of broadcast as part of vehicles can not decode the broadcast successfully and incur severe impact on road safety. However, this impact has not been addressed by existing protocols. In this paper, we first present the definition of broadcast efficiency (BE) as the metric for measuring the obstructing effect and conclude the optimization issue of propagation. We further propose a distributed algorithm for mitigating this impact that can be embedded in VANETs. This algorithm maximizes the effective coverage of the broadcast of safety-related information and meanwhile satisfies the constraints on both link state and delay by selecting relay according to BE and referential propagation distance. Simulation results demonstrate that the proposed algorithm promotes the efficiency of propagation in dynamic multilane VANETs with varying vehicular distribution.

To promote smart campus, National Chiao Tung University is deploying several location-based IoT applications based on wireless communications technologies including LoRa and NB-IoT. The applications are indoor/outdoor environment conditions monitoring (such as PM2.5, temperature, and humidity), emergency buttons, and so on. This paper uses PM2.5 measurement application as an example to present the performance of LoRa when it is used on campus. We investigated the LoRa transmission performance from LoRa end-devices to the LoRa gateway. We show how packet losses were affected by the distance between the end-device and the gateway, the transmit power, the payload length, the antenna angle, the time of day, and the weather conditions. The pattern of LoRa packet losses were also measured and we found that in our long-term PM2.5 monitoring application, more than 99\% of LoRa packet losses occurred with three or less consecutive packet losses.

IoTtalk is a platform for Internet of Things (IoT) device interaction, which nicely integrates a reconfigurable multi-sensor device called MorSensor with the proposed IoT management platform in the network domain. The sensors can be dynamically plugged in/out of a MorSensor device without being turned off, and IoTtalk automatically generates/reuses the application software for these sensors. We propose a dynamic ranging concept that automatically specifies the value range of a sensor so that it can send “meaningful” data to any connected output IoT device. Therefore, a MorSensor device can “talk” to other IoT devices, such as a light bulb or an electric fan. We also show that IoTtalk is a simple yet almost free solution for automatic sensor calibration. Finally, we illustrate that IoTtalk is a powerful tool for developing interactive science experiments.

Almost half of all Americans either own smart home technology or plan to invest in it. Therefore, many commercial smart IoT solutions aim for home automation, and try to live up with high expectation for smart home. A major problem of these smart home solutions is that they cannot flexibly accommodate the existing remotely controlled aftermarket appliances. This paper proposes IoTtalk remote control (IoTtalk-RC), a mechanism that utilizes sensors as universal software-defined remote control for aftermarket home appliances. Our solution replaces the infrared remote controller of cheap aftermarket home appliances and provides extra intelligence of sensors that can be manipulated by the homeowners. We conduct measurements, analytic analysis and simulation experiments to investigate the time complexity of IoTtalk-RC. This paper indicates that the extra transmission delays of remote control incurred by IoTtalk-RC are small even if the IoTtalk server is remotely located at a virtual machine of a cloud. In other words, IoTtalk-RC is feasible and can be effectively operated with the IoT technology.

The small cell technology is proposed to provide wireless transmission services in the indoor environment and offload the traffic from a macro cell. Because of the small coverage of a small cell, there are usually a large number of small cells deployed in the mobile network, and it is likely that there are no User Equipments (UEs) in a small cell. A small cell may be idle most of the time and waste energy. In this paper, we propose a Connection-Driven (CD) mechanism for energy saving of small cells, where a small cell in the sleep mode is woken up when there are UEs (that have ongoing dedicated bearers) within its service area. We propose an analytical model and simulation experiments to investigate the performance of the CD mechanism.

Abstract A web album service allows a user to publish photo albums on the web and view albums of other users. Through broadband mobile telecom, users can enjoy watching contents of web albums at any place in real time. User experience on mobile web album is affected by the transmission delay of mobile network, which determines whether the user needs to wait to view the images. We propose a prefetching mechanism that enhances user experience on accessing mobile web albums. A transmission control protocol‐like sliding window protocol (of sizeN) is exercised, and when the buffer for the sliding window at the user equipment is full, prefetching is suspended. The buffer sizeNaffects the prefetching performance. The larger theNvalue, the better the user experience. However, a largeNvalue means that many images will be prefetched. If they are not actually viewed by the user, the network resources for transmitting these images are wasted. This paper proposes both analytic and simulation models to select the smallestN(the optimalNvalue) so that the expected user experience can be achieved. Copyright © 2014 John Wiley & Sons, Ltd.

In this paper, we study on the price comparison between shared plan and non-shared plan for mobile service. A non-shared data plan is a traditional data plan for a single user with a limited monthly data allowance. A shared data plan allows a user to add different devices to one inclusive plan and receive one bill at the end of every month, which the monthly data allowance is shared by a group of users across multiple devices. Each data plan is charged by a fixed price for a monthly data allowance and there will be an extra charge if a user consumes more than the monthly data allowance. Therefore, the charged price is affected by the user's behaviors. We study the users' behaviors by observing the measured data from Chunghwa Telecom and derive stochastic models for shared plan and non-shared plan to evaluate monthly prices based on different users' behaviors. We recommend the most appropriate plan for a group of users based on users' behaviors. On the other hand, mobile operators can attract more customers and earn more profit. We show that the shared plan is a `win-win' plan for users and operators.

The comprehensive analysis on historical and real-time big data delivers huge business value, explores business intelligence, and assists in developing marketing strategies. This talk uses traffic information cloud as an example to show how big data is used to improve the accuracy and coverage of traffic information. Taiwan government is investing Traffic Info. cloud services to bring new business opportunities. It is proved that the Traffic Info. Cloud can effectively provide traffic information in terms of accuracy and large information coverage area. However, to execute the plan of Traffic Info. cloud service, our government is facing the challenges of big data: to extract traffic information from high-velocity data, and to store and analyze high-volume historical data. We show how these issues can be addressed through cloud computing platform and describe the Lin-Chang-Huangfu (LCH) Scheme that takes the advantage of the standard statistics available in mobile switching centers for vehicle speed analysis. We also show how cloud computing techniques are utilized for animation visual effect and passenger movement prediction.

Many Internet of Things (IoT) technologies have been used in applications for money flow, logistics flow, people flow, interactive art design, and so on. To manage these increasing disparate devices and connectivity options, ETSI has specified end-to-end machine-to-machine (M2M) system architecture for IoT applications. Based on this architecture, we develop an IoT EasyConnect system to manage IoT devices. In our approach, an IoT device is characterized by its “features” (e.g., temperature, vibration, and display) that are manipulated by the network applications. If a network application handles the individual device features independently, then we can write a software module for each device feature, and the network application can be simply constructed by including these brick-like device feature modules. Based on the concept of device feature, brick-like software modules can provide simple and efficient mechanism to develop IoT device applications and interactions.

In-home Smart Grid (SG), the integration of Renewable Power Systems (RPSs) with Conventional Power Systems (CPSs), calls for cost-effective management for the electricity usages of end users' household appliances. In this paper, by taking the charging process of RPSs and multiple types of household appliances in to consideration, we have developed analytical models to characterize the electricity cost in the in-home smart grid. Based on these models, we formulate the electricity cost minimization problem as a finite-horizon continuous-time Markov decision process (CTMDP), from which we obtain a threshold policy to minimize the cost. Numerical results show that the threshold policy can manage the electricity usage very effectively.

Abstract The control signals of cellular networks have been used to infer the traffic conditions of the road network. In particular, consecutive handover events are being used to estimate the traffic speed. During traffic congestion, consecutive handover events may be rare because vehicles move slowly, and thus very few or no speed reports would be generated from the congested area.However, the traffic speed report rate during traffic congestion has not been investigated in the literature. In this paper, we present an analytic model to estimate the speed report rate from cellular network signaling in steady traffic conditions, that is, the traffic speed and flow are assumed constant. Real field trial data were used to validate our analytic model. In addition, computer simulations were conducted to study how speed reports are generated in dynamic traffic conditions when traffic speed and flow change rapidly. Our study indicates that in a typical cell of length 1.5 km with a typical expected call holding time of 1 min, no speed report was generated from a congested three‐lane highway. Our study demonstrates that the lack of speed reports from consecutive handover events during rush hours indicates severe traffic congestion, and new methods that can estimate traffic speed from cellular network data during severe traffic congestion need to be developed. Copyright © 2013 John Wiley & Sons, Ltd.

In long-term evolution, the service area is partitioned into several tracking areas TAs, which comprise one or more cells the radio coverages of base stations. The TAs are grouped into TA list TAL. When an incoming call arrives, the network attempts to connect to the user equipment UE by paging the cells in the UE's TAL, which may incur large paging traffic that significantly consumes the limited radio resources. To resolve this issue, this paper proposes a dynamic paging scheme that determines the paging sequence of cells in real time according to the UE movement and call behavior. We compare the performance of the dynamic paging with that of the previously proposed Cell-TA-TAL CTT paging. Our study indicates that the dynamic paging outperforms the CTT paging when movement pattern is regular and the UE moves frequently. Copyright © 2013 John Wiley & Sons, Ltd.

A ticket dispenser (TD) is used to assist customers for the waiting process in, e.g., a shop. This paper deploys a mobile ticket dispenser system (MTDS) with waiting time prediction to enhance user experience in waiting. For example, the MTDS for a restaurant allows a customer to remotely draw a ticket for meal order anywhere through a smart phone before she/he arrives at the restaurant and therefore reduces her/his waiting time. We propose an output indicator and develop a discrete event simulation model to investigate the performance of the MTDS. Our study indicates that the waiting times can be more accurately predicted without consuming much wireless network resources and power consumption of mobile devices.

In Long Term Evolution (LTE), Voice over Internet Protocol (VoIP) is used for the delivery of the voice data. One of the major challenges for VoIP over LTE is to guarantee the Quality of Experience (QoE) of the VoIP calls. This paper uses an LTE base station emulator and a radio channel emulator to evaluate the impacts of different User Equipment (UE) velocities and Radio Link Control (RLC) parameter values on the QoE of the calls in the vehicular environment. Our study shows that LTE can provide acceptable VoIP quality in the high-speed scenarios (e.g., high-speed train). This paper provides the guidelines for the telecommunications operators to select the appropriate parameter values when deploying their VoIP services in LTE.

Provisioning commercial mobile telecommunications service on a high-speed train (HST) faces several challenges. In particular, when an HST quickly passes through the radio coverage of the base stations, frequent handovers may result in serious communication interruption. Methods such as the hierarchical two-hop network and the seamless dual-link handover scheme were proposed to address these challenges. This paper proposes the multiple radio access technology (multi-RAT) to resolve the HST handover issue, which allows the HST to simultaneously connect to two or more heterogeneous mobile networks (e.g., the Universal Mobile Telecommunications System and Long Term Evolution). With this approach, the handover process can be improved by keeping multiple heterogeneous network links of the HST at the same time and maintaining the connection through one link during the handover process of the other link. We show that multi-RAT can effectively enhance HST communications by reducing the impact of handover failure. This approach can work together with other solutions such as the dual-link scheme to further enhance the performance of the HST communications.

Long Term Evolution (LTE) evolved from Universal Mobile Telecommunications System (UMTS), which utilizes IP Multimedia Core Network Subsystem (IMS) to provide voice service. In most existing commercial operations, the LTE networks provide zonal coverage as compared with UMTS networks which provide full service coverage. A User Equipment (UE) can initiate or receive an IMS call in either LTE or UMTS. The UE uses LTE whenever it is available. If LTE is out of service, then the UE is transferred to UMTS. To support access transfer between LTE and UMTS during an IMS call, 3rd Generation Partnership Project (3GPP) proposed Enhanced Single Radio Voice Call Continuity (eSRVCC). If the UE frequently moves back and forth between LTE and UMTS during an IMS call, it may incur large access transfer traffic. To resolve this issue, we propose the limited access transfer algorithm that limits the number of access transfers in an eSRVCC call (referred to as the transfer limit) to reduce the transfer traffic. An analytic model is proposed to investigate the performance of the limited access transfer algorithm. Our study indicates that the selection of the transfer limit is not a trivial issue, and an appropriate transfer limit effectively reduces the access transfer traffic to enhance the LTE call control performance.

In the broadband era, narrowband short message service (SMS) is still the most popular wireless data service. Many studies have been conducted to investigate the performance of SMS based on the arrival rates of short messages. From Chunghwa Telecom's commercial SMS call data records, we observed that even if the SMS arrival rates are the same, the distributions for the number of SMS arrivals per half hour are quite different for various observed days. We further identify that for the SMS traffic in a specific day, there are non-burst and burst periods. This paper investigates the SMS behaviors on weekdays, weekends, and holidays (specifically, new years' days and eves). With the assistance of kernel-based fitting method, we derive the SMS arrival number distributions of various traffic types and observed days. Our approach fits each SMS arrival number distribution by three cubic polynomial functions that can accurately capture the SMS behaviors. On the basis of the SMS arrival number distributions derived from our model, the mobile operators have better understanding about the volumes of short messages in different times and days, which can be used to design more flexible short message charging rates. Copyright © 2012 John Wiley & Sons, Ltd.

Legacy networks, both fixed and mobile, which were originally designed for voice communications, are progressively migrating to new infrastructures that promise to revolutionize the services offered. In this paper, we will cover this new generation of personal communication services, with an emphasis on the family of Internet protocol (IP)-based multimedia subsystem (IMS)-aided infrastructure that relies on the session initiation protocol (SIP). As a benefit, the end users will enjoy a new generation of personal communications services that are accessible anywhere and anytime. These services are directly related to the end users rather than to their diverse devices. It is anticipated that the new deployments of next-generation networks (all-IP based) will accelerate the adoption of the IMS technology.

Vehicle speeds are often measured by intelligent transportation systems (ITSs) by utilizing sensors or software solutions. Our previous work proposed the Lin-Chang-Huangfu (LCH) scheme to compute the cell residence times by the standard counter values in mobile telecommunications switches. In this paper, we use mathematical and statistical developments to investigate the accuracy of the LCH scheme by deriving the bias of the cell residence times computed in this scheme. Then, we extend the LCH scheme with some filtering and compensation techniques for vehicle speed estimation and validate our approach with vehicle detector (VD) measurements at National Highway 3, Longtan Township, Taoyuan County, Taiwan. Our study indicates that the LCH scheme is an effective approach to vehicle speed estimation.

Femtocell technology has been proposed to offload user data traffic from the macrocell to the femtocell and extend the limited coverage of the macrocell in mobile communications networks. In existing commercial femtocell/macrocell networks, a widely accepted solution to configure the location areas (LAs) is to partition the femtocells overlapped with a macrocell into small groups and to assign each group with a unique LA ID different from that of the macrocell. Such configuration can reduce the paging cost in the mobility management, but increases registration signaling overhead due to discontinuous coverage of femtocells. To reduce signaling overhead in the femtocell/macrocell network, we propose a delay registration (DR) algorithm that postpones the registration until the delay timer expires when the mobile station (MS) moves into the overlapped femtocell. Analytical models and simulation experiments are proposed to investigate the performance of the DR algorithm. Our analytical models are generally enough to accommodate various MS mobility behaviors. Our study can provide guidelines for the operators to set up a delay timer to reduce signaling overhead while sustaining the traffic offloading capability of the femtocell.

Investigating human movement behavior is important for studying issues such as prediction of vehicle traffic and spread of contagious diseases. Since mobile telecom network can efficiently monitor the movement of mobile users, the telecom's mobility management is an ideal mechanism for studying human movement issues. The problem can be abstracted as follows: What is the probability that a person at location A will move to location B after T hours. The answer cannot be directly obtained because commercial telecom networks do not exactly trace the movement history of every mobile user. In this paper, we show how to use the standard outputs (handover rates, call arrival rates, call holding time, and call traffic) measured in a mobile telecom network to derive the answer for this problem.

Mobility management in Long Term Evolution (LTE) is different from that in the third generation mobile telecom networks. In LTE, the Mobility Management Entity (MME) is responsible for the mobility management function. The MME is connected to a large number of evolved Node Bs (cells) that are grouped into the Tracking Areas (TAs). The TAs are further grouped into TA Lists (TALs). When a User Equipment (UE) moves out of the current TAL, it reports its new location to the MME. If the LTE network attempts to connect to the UE, the MME asks the cells in the TAL to page the UE. In LTE paging, the MME may sequentially page a cell, the TA of the cell, and/or the TAL of the cell. This paper investigates the performance of LTE paging, and provides the guidelines for the best paging sequence of cells.

ABSTRACT Call forwarding is a traditional telecom service that allows a user to forward incoming calls to another telephone number. This service requires the user to manually activate and deactivate the feature and therefore may not be very convenient. This paper proposes an automatic call‐forwarding algorithm (CFA) for mobile phones. By installing a software in a smartphone, call forwarding is automatically triggered (e.g., when the phone is plugged in a charger or is turned off) or disabled (e.g., when the phone is unplugged from the charger or is turned on). We investigate the performance of the CFA through analytic analysis, simulation, and measurement. Our study indicates that CFA is very feasible for commercial usage. Copyright © 2011 John Wiley & Sons, Ltd.

Abstract A Next Generation Network (NGN) has been developed in Taiwan, where IP Multimedia Subsystem (IMS) plays an important role to offer IP‐based multimedia services. Such NGN/IMS networks have also been deployed worldwide. However, details of commercial‐grade NGN service implementations are seldom reported in public. In this paper, we show how existing video phone service can be enhanced through Chunghwa Telecom's NGN/IMS. Specifically, we illustrate three examples including Multimedia on Demand (MOD) TV, Multimedia Ringback Tone (MRBT), and Easy Go (EzGo). We also measure the delay times for accessing these services. The measurements indicate that performance for these IMS‐based services is satisfactory. Copyright © 2010 John Wiley & Sons, Ltd.

Abstract Voice over IP (VoIP) is a promising low‐cost voice communication over the wireless IP network. To provide satisfactory VoIP services, the Quality of Service (QoS) of the wireless network should be guaranteed. This paper proposes a VoIP performance measurement freeware called NCTU VoIP Testing Tool (NCTU‐VT). We compare NCTU‐VT with two commercial tools SmartVoIPQoS and IxChariot in terms of packet loss, latency, and Mean Opinion Score (MOS) of the VoIP sessions in Wi‐Fi network. Our study indicates that these three tools can accurately measure VoIP performance in Wi‐Fi environment. Copyright © 2010 John Wiley & Sons, Ltd.

Today, charging stations (CSs) for electric vehicles (EVs) are much less popular than gas stations. Therefore, searching and selecting CSs is an important issue for the drivers of EVs. This paper investigates the EV charging problem. We propose two types of CS-selection algorithms. The first type only utilizes local information of an EV. The second type utilizes the global information obtained from mobile computing. Specifically, the EVs interact with a Global CS-selection (GCS) server through the mobile telecommunications network. Our study indicates that by using the global information (specifically the workload status of each CS), the EVs can be effectively charged with short waiting times at the CSs.

Facebook platform offers rich APIs and has a huge number of users and user-generated contents. This paper presents our mobile Facebook application on Android, called DEFAC, which turns Facebook contents into an ePub file step by step. Users can therefore bring contents with them for offline-reading. We expect that the interactions of e-reader's users and social reading services may become new important applications for both social-network services and e-book industry in the near future.

In Next Generation Network (NGN), IP Multimedia Subsystem (IMS) plays an important role to offer IP-based multimedia services. Based on Chunghwa Telecom's NGN/IMS, we develop linear-type data transmission applications such as Bulletin Board System (BBS) or forum-based websites to deliver new articles to the mobile users. We propose the push-N method that pushes every N articles from the BBS server to the user. When the user actually connects to the BBS, the not-yet-pushed messages are pulled by the user. Our study indicates that by selecting appropriate N values, push-N can balance against the push and the pull operations, and therefore improves the user access experience without wasting too much network resources.

In mobile telecommunications, the residence times of users at a cell or a location area are an important input parameter for network planning and performance evaluation of a mobile network. However, measurement of cell residence times in a commercially operated mobile network is not trivial, which typically requires tracing the movement of individual users. In this paper, we show how to use the standard counter values (number of handovers and call traffic) measured in a mobile telecommunications network to derive the cell residence times. These counter values can be obtained directly from telecommunications switches. Therefore, we can provide a quick and simple solution to compute cell residence times.

Today's mobile service providers allow their users to receive telecom services when they roam to other countries. However, international roaming is very expensive. In the standard mobile call setup procedure, a call from the visited country to a roaming user in that country results in two international calls. This phenomenon is referred to as the tromboning effect. Several third-party solutions have been proposed to resolve the tromboning problem by replacing two international calls with two local calls. These solutions require one or more gateways for call re-routing. This paper proposes a handset-based solution that does not need to add/modify network nodes in the existing mobile telecom systems. Analytic modeling and simulation experiments indicate that our solution is effective in international trunk elimination and call setup signaling.

Android is an open mobile phone platform. To accommodate value-added services such as selling wallpapers, ringtones, applications, and games on Android phones, it is essential to ensure copyright protection on these products. This paper studies how the Android source code to implement the Open Mobile Alliance (OMA) Digital Right Management (DRM) 1.0, software installation and protection. We also identify potential leaks of Android DRM and software protection in this study.

In Wireless Access in Vehicular Environment (WAVE), the WAVE Short Messages (WSMs) are broadcasted from the Roadside Unit (RSU) to the Onboard Units (OBUs). On the other hand, WAVE does not specify how to provide WSM-based unicast service to an OBU. In this paper, we devise location tracking procedure so that an OBU can be tracked and receive unicast messages. We also investigate the effect of vehicle traffic on the location tracking mechanism.

Improving cellular backhaul capacity in the Universal Mobile Telecommunications System (UMTS) has long been desired, and is even demanding now due to the ever-advancing access technologies. Considering the pricy traditional leased line solution, it is tempting to devise a cost-effective alternative. In this work, we propose an offloading technology in order to divert a major part of the backhaul traffic to links that are more cost affordable. An experimental system is prototyped and tested. Measurements indicate good performance of our approach.

In the past, although mobile devices were equipped with multiple radio interfaces, for the sake of power saving, only one was activated for data transmission. The idea of concurrent transmission via multiple radio interfaces has not been seriously studied. However, nowadays, power consumption no longer is a problem in many application scenarios, e.g. VANETs. In this work, we investigate the performance improvement of concurrent file transfer over two heterogeneous radio networks, e.g. WiFi and 3G. The traditional File Transfer Protocol is modified to utilize two heterogeneous radio connections and experiments are executed over the Internet and a 3G data network to measure the latency and average bandwidth. Our results show that it is possible to integrate the bandwidth of both radio networks.

Considering voice as a dominant telecommunication service, the performance of Voice over IP (VoIP) plays a critical role in deployment of worldwide interoperability for microwave access (WiMAX) technology providing all-IP network services. To that effect, in this study, the authors investigate the performance of a WiMAX-based VoIP established under the mobile Taiwan (M-Taiwan) field-trial funded program. To achieve the objectives of the trial the measurement results expressed in the form of mean opinion score (MOS), packet loss, packet delay and jitters. For the worst-case scenario, the tests were conducted under a stringent condition of both communicating devices, wirelessly connected to the same WiMAX base station under a heavy background traffic and interference, were experiencing simultaneous handovers during the communication. Upon their analysis, the field measurements confirm an excellent performance when both communicating devices kept stationary and show an acceptable quality for the service when both communicating devices are on the move at a speed of 50 km/h.

Short message service (SMS) is the most popular mobile data service today. In Taiwan, a subscriber sends more than 200 short messages per year on average. The huge demand for SMS significantly increases network traffic, and it is essential that mobile operators should provide efficient SMS delivery mechanism. In this paper, we study the short message retransmission policies and derive some facts about these policies. Then, we propose an analytic model to investigate the short message retransmission performance. The analytic model is validated against simulation experiments. We also collect SMS statistics from a commercial mobile telecommunications network. Our study indicates that the performance trends for the analytic/simulation models and the measured data are consistent.

Online Charging System (OCS) supports multiple prepaid and postpaid sessions simultaneously. Through credit reservation, the OCS assigns some credit units to a session. These credit units are decremented based on the traffic volume or the duration time. If the assigned credit units are consumed before the session is completed, an reserve units (RU) operation is executed to obtain more credit units from the OCS. If the credit at the OCS is depleted, the prepaid session is forced to terminate. During the RU operation, packet delivery is suspended until extra credit units are granted from the OCS. To avoid session suspension during credit reservation, we propose the credit pre-reservation mechanism (CPM) that reserves credit earlier before the credit at the GGSN is actually depleted. Analysis and simulation experiments are conducted to investigate the performance of the mechanism. Our study indicates that the CPM can significantly improve the performance of the OCS prepaid mechanism.

Femtocell is an effective solution to improve indoor coverage for cellular networks, where short-range and low-power Base Stations (BSs) called Femto BSs are deployed in small areas (e.g., buildings). We propose the Femto Private Branch Exchange (FPBX) to concentrate the traffic of the Femto BSs in a specific area, such as a campus or an enterprise with central or distributed locations. Through the FPBX, a normal cellular call between two Femto users can be replaced by a low-cost extension call. Therefore, the call routing cost can be significantly reduced. In this approach, the existing mobile network nodes are not modified. We analytically analyze the call routing performance for the FPBX approach, and develop simulation experiments to validate against the analytic model. Our study indicates that the FPBX approach can effectively reduces the call setup costs and the voice trunk costs among Femto users by slightly increasing the normal cellular call setup costs.

Abstract The WiMAX Forum certifies and promotes the compatibility and interoperability of broadband wireless products where many testcases need to be developed for WiMAX procedures. In this paper, we develop a conformance test tool called ITRI‐WiMAXT based on the TTCN‐3 specifications. Then we show how WiMAX procedures are tested in ITRI‐WiMAXT. Based on ITRI‐WiMAXT, we have proposed several test procedures accepted by the WiMAX Forum. Copyright © 2009 John Wiley & Sons, Ltd.

The IP multimedia core network subsystem (IMS) provides multimedia services for Universal Mobile Telecommunications System (UMTS). In IMS, an emergency call is established by an emergency call session control function (ECSCF). The E-CSCF dispatches the call to the nearest public safety answering point (PSAP) according to the location of the caller. After emergency call setup, the caller's location is tracked by the PSAP through location polling. This paper investigates the performance of location tracking. Then we propose the active location reporting scheme to improve the performance of location tracking. Our study indicates that the active location reporting scheme may significantly outperform the location polling scheme.

IP multimedia core network subsystem (IMS) provides presence service for universal mobile telecommunications system (UMTS). In IMS, the presence server is responsible for notifying an authorized watcher of the updated presence information. If the updates occur more frequently than the accesses of the watcher, the presence server will generate many notifications. This paper uses a weakly consistent scheme (called delayed update) to reduce the notification traffic. In this scheme, a delayed timer is defined to control the notification rate. We propose an analytic model and simulation experiments to investigate the performance of delayed update. The study indicates that delayed update can effectively reduce the notification traffic without significantly degrading the valid access probability.

Existing mobile service providers allow their customers to receive telecommunications services when they roam to other countries. However, in the standard mobile call setup procedure, a call from the visited country to a roaming customer at that country results in two international calls. This phenomenon is referred to as the tromboning effect. In this paper, we propose a third-party solution that resolves the tromboning problem by replacing two international calls with two local calls. Besides huge saving in voice/data path, analytic modeling and simulation experiments indicate that our solution is effective in call setup signaling. Also, our solution does not need to modify the existing mobile telecommunications systems.

Universal Mobile Telecommunications System (UMTS), the core network consists of two service domains: the circuit-switched (CS) and the packet-switched (PS) domains. A UMTS handset can initiate or receive a call in either the CS or the PS domain. During the call, the user may switch from one domain to another. The switching overhead is an important concern of domain transfer. In this paper, we propose the Bearer Reservation with Preemption (BRP) scheme to support fast domain transfer, and present both analytic model and simulation experiments to investigate the BRP performance. Our study indicates that when user behavior is irregular (i.e., either the variance of the domain residence times or the variance of the call holding times is large), the advantage of the BRP scheme becomes significant.

TheIP Multimedia Core Network Subsystem(IMS) provides multimedia services for Universal Mobile Telecommunications System (UMTS). In IMS, an emergency call is established by anEmergency-Call Session Control Function(ECSCF). The E-CSCF dispatches the call to the nearestPublic Safety Answering Point(PSAP) according to the location of the caller. After emergency call setup, the callers location is tracked by the PSAP through Location Polling. This paper investigates the performance of location tracking. Then we propose the Active Location Reporting Scheme to improve the performance of location tracking. Our study indicates that the Active Location Reporting Scheme may significantly outperform the Location Polling Scheme.

During an online charging general packet radio service (GPRS) session, a number of mid-session events, such as changes of quality of service (QoS), could dynamically affect the rating of the in-progress service. When such events occur, the GPRS support node needs to re-authorize the granted credit units with the online charging system (OCS). This paper proposes a threshold-based scheme that utilizes a threshold parameter delta to reduce the signaling traffic for the credit re-authorization procedure. By selecting an appropriate delta value, the signaling overhead in the OCS can be significantly reduced while the inaccuracy of the credit information insignificantly increases. The mobile operator can choose appropriate parameter values in the threshold-based scheme based on our study.

Push-to-talk over cellular (PoC) is a ldquowalkie- talkie-likerdquo service designed for mobile networks. In this service, the speak permission is arbitrated through the talk burst control (TBC) mechanism. This paper proposes an analytic model to study the performance of the TBC mechanism with queueing and without queueing. This analytic model is validated against simulation experiments. Through numerical examples, our study provides guidelines to set up the parameters for PoC service.

Abstract The 3rd Generation Partnership Project (3GPP) defines IP Multimedia Core Network Subsystem (IMS) to support IP‐based multimedia services. IMS utilizes protocols such as IP version 6 (IPv6), Session Initiation Protocol (SIP), and Real‐time Transport Protocol (RTP) to deliver the multimedia content. This paper proposes an analysis tool referred to as SIPv6 Analyzer to investigate the IMS‐related protocols during IMS service deployment. The SIPv6 Analyzer not only dissects the protocol headers but also provides user‐friendly functions such as message flow generation and audio/video replay for IPv6, SIP, and RTP. We describe the design of the SIPv6 Analyzer and use examples to illustrate how it works. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract In wireless local area network (WLAN), a station (STA) accesses the Internet through an access point (AP). When switching from one AP to another, the STA executes the transition process, which may incur long delay and result in force‐termination for real‐time applications. The IEEE 802.11r proposes the fast basic service set (BSS) transition to speed up the transiti on process for a STA moving within the same mobility domain (MD). This scheme requires unique MD assignment so that the STA knows whether it should conduct fast BSS transition process (for intra‐MD scenario) or the expensive initial MD association process (for inter‐MD scenario). However, how to guarantee unique MD identifier (MDID) assignment is not mentioned in the specification. This paper proposes a mechanism for IEEE 802.11r fast transition without using MDID, and therefore eliminates the cost for MDID management. Copyright © 2007 John Wiley & Sons, Ltd.

Abstract This paper describes a conformance test tool for push‐to‐talk over cellular network developed on an Open Mobile Alliance Service Interoperability Test Platform. Based on the TTCN‐3 specifications, we show how PoC test cases can be efficiently implemented on the test platform. Copyright © 2007 John Wiley & Sons, Ltd.

Push to talk (PTT) is a walkie-talkie like service. In this service, several predefined group members participate in one PTT session. At any time, only one group member is allowed to speak. Therefore, a mechanism is required to determine the member that is permitted to speak. In Open Mobile Alliance (OMA), a central arbitrator coordinates the permission to speak among the group members. In the Intelligent Transportation System (ITS) environment, the centralized OMA approach is not appropriate. This paper proposes a distributed PTT mechanism for the ITS environment, which does not require any central arbitrator. The group member permitted to speak is automatically determined through distributed learning interaction. We also explore the properties and model the performance of the proposed PTT mechanism.

The Universal Mobile Telecommunications System (UMTS) provides high bandwidth packet data services to mobile users. To support mobility management, an MM context is established for every mobile station in its corresponding Serving GPRS Support Node (SGSN). When the SGSN fails, all MM contexts in the SGSN are corrupted. These MM contexts must be recovered or data delivery to the mobile stations will fail. This paper describes a broadcast approach that allows the MS to detect lost MM context in SGSN and therefore speeds up the process for SGSN recovery. We propose an analytic model to evaluate the performance of the broadcast approach. The analytic model is validated against simulation experiments. Based on our study, the network operator can select the appropriate parameter values in the broadcast approach for various traffic conditions.

This paper studies IEEE 802.1X authentication for WLAN and cellular integration. In the IEEE 802.1X standard, several timeout timers are defined for message exchanges in the EAPOL protocol, where the same fixed value is suggested for these timeout timers. We observe that the delays for the EAPOL message exchanges may significantly vary. A modeling study is performed to tune the values of individual timers to yield better performance than that for the identical timeout period setting. Our study provides guidelines to select appropriate timeout values for IEEE 802.1X operation.

The IP multimedia core network subsystem (IMS) provides real-time multimedia services for Universal Mobile Telecommunications System (UMTS). Through recharge threshold-based credit reservation (RTCR) mechanism, prepaid IMS services can be supported by the online charging system (OCS) in UMTS. In RTCR, when the remaining amount of prepaid credit is below a threshold, the OCS reminds the user to recharge the prepaid account. It is essential to choose an appropriate recharge threshold to reduce the probability that the in-progress service sessions are forced-terminated. An analytic model is developed to investigate the performance of RTCR for the OCS. Based on our study, the network operator can select the appropriate parameter values for various traffic conditions.

This paper studies checkpointing and failure restoration of mobility database for Universal Mobile Telecommunications System (UMTS). By utilizing per-user checkpointing technique, individual home location register (HLR) records are saved into non-volatile backup storage form time to time. When a failure occurs, the backup record is restored back to the mobility database. We consider three per-user checkpoint schemes for the HLR. An analytic model is developed to investigate these schemes in terms of the probability that a HLR backup record is obsolete and the expected checkpoint interval. This model is validated against simulation experiments. Our study provides guidelines for selecting an appropriate checkpoint scheme and parameters for various traffic conditions

In Universal Mobile Telecommunication System (UMTS), the security function provides mutual authenticity and key agreement between the core network and the Mobile Station (MS). Specifically, the Serving GPRS Support Node (SGSN) in the core network obtains an array of Authentication Vectors (AVs) from the Home Subscriber Server/Authentication Center (HSS/AuC), and consumes one AV for each mutual authentication. After the departure of the MS, the SGSN may keep the unused AVs for a time interval called the Reservation Timeout (RT) period. If the MS returns within the RT period, the SGSN uses the stored AVs for mutual authentication instead of obtaining new AVs from the HSS/AuC. Note that a long RT period results in fewer accesses to the HSS/AuC at the cost of extra AV storage in the SGSN. In this paper, we propose an analytic model to investigate the impact of the RT period on the system performance. Our study provides the guidelines for the mobile operators to select an appropriate RT period.

Abstract In universal mobile telecommunications system (UMTS), session management (SM) maintains a communication session between a user equipment (UE) and the core network. 3GPP TS 24.008 specifies the SM functions and the communication protocols between the UE and the core network. However, the interaction between the SM and other entities in the UE are not specified in detail. This paper designs and implements the SM software. We use a finite state machine (FSM) to model the SM functions. Based on the FSM and the primitives, we describe how to set up the development steps to implement the SM at the UE. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract This paper proposes a client architecture for the push to talk over cellular (PoC) service based on the open mobile alliance (OMA) PoC specifications v1.0 release. We show that most standard VoIP modules can be reused for the PoC client, and the VoIP software can be easily extended to support PoC service. Then we present the detailed message flows between the PoC client and other network entities in the PoC system. A PoC client prototype has been implemented in the Industrial Technology Research Institute (ITRI) and National Chiao‐Tung University (NCTU) Joint Research Center. Copyright © 2006 John Wiley & Sons, Ltd.

In Universal Mobile Telecommunications System (UMTS), the extension of GPRS tunneling protocol called GTP' is utilized to transfer the charging data records (CDRs) from GPRS support nodes (GSNs) to charging gateways (CGs). To ensure that the mobile operator receives the charging information, availability for the GTP' transmission is essential. One important issue on GTP' availability is connection failure detection. It is desirable to select appropriate parameter values to avoid false failure detections (e.g., temporary network congestions) while to detect the true failures quickly. We propose an analytic model to compute the false failure detection probability and the expected true failure detection time. Based on our study, the network operator can select the appropriate parameter values for various traffic conditions to reduce the probability of false failure detection and/or true failure detection time.

In the next generation mobile telecommunications, any third party that provides wireless data services (e.g., mobile banking) must have its own solution for end-to-end security. Existing mobile security mechanisms are based on public-key cryptosystem. The main concern in a public-key setting is the authenticity of the public key. This issue can be resolved by identity-based (ID-based) cryptography where the public key of a user can be derived from public information that uniquely identifies the user. This paper proposes an efficient ID-based encryption algorithm. We actually implement the ID-based encryption schemes and compare the performance to show the advantage of our approach. Our study indicates that our solution outperforms a previously proposed algorithm by 20 - 35%.

Abstract-The IP multimedia core network subsystem (IMS) provides multimedia services for Universal Mobile Telecommunications System (UMTS). In IMS, any incoming call will first arrive at the interrogating call session control function (I-CSCF). The I-CSCF queries the home subscriber server (HSS) to identify the serving CSCF (S-CSCF) of the called mobile user. The S-CSCF then sets up the call to the called mobile user. This paper investigates the performance of the IMS incoming call setup. We also propose cache schemes with fault tolerance to speed up the incoming-call-setup process. Our study indicates that the I-CSCF cache can significantly reduce the incoming-call-setup delay, and checkpointing can effectively enhance the availability of I-CSCF.

Abstract This paper proposes iMobile, a proxy‐based platform for developing mobile services for various mobile devices and wireless access technologies. iMobile acts as a message gateway that allows mobile devices to relay messages to each other through various protocols on different access networks. It allows mobile devices to access internet services, corporate databases and to control various network devices. iMobile implements three key abstractions: dev‐let, info‐let and app‐let. An info‐let provides abstract view of information space. An app‐let implements service or application logic by processing information from various info‐lets. A dev‐let receives and sends messages through any particular protocols for mobile devices. The let engine supports user and device profiles for personalization and transcoding, and invokes proper app‐lets and info‐lets to answer requests from a dev‐let. The iMobile modular architecture allows developers to write device drivers, information access methods and application logic independently from each other. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract In the Universal Mobile Telecommunications System (UMTS), session initiation protocol (SIP) and IPv6 are the default protocols for IP multimedia core network subsystem (IMS). However, a user equipment (UE) may not be allowed to roam or hand off from UMTS to a private‐IPv4 GPRS network. In this paper, we utilize SIP mobility and an automatic IPv6 tunneling mechanism, called Teredo, to support roaming/handoff of a UE between different networks. We have developed the first non‐commercial Linux‐based Teredo mechanism, and compared our solution with other Teredo implementations in the public domain. Our study indicates that our solution can reduce the tunneling overhead and transmission delay over two other implementations by 44–74%. Copyright © 2006 John Wiley & Sons, Ltd.

Teredo is a service that enables hosts located behind one or more IPv4 NATs to obtain IPv6 connectivity by tunneling packets over IPv4 UDP. Under the national IPv6 deployment project in Taiwan, we developed the first Linux-based Teredo service in 2003. In this paper, we explain how IPv6 candidates located behind NATs can enlist the help of "Teredo servers" and "Teredo relays" to learn their "global addresses" and to obtain connectivity, and how clients, servers and relays can be organized in Teredo networks. We also describe in details our strategies for implementing Teredo server and Teredo relay under Linux, and show the performance of different Teredo implementations in public domain.

Both IPv6 and session initiation protocol (SIP) are default protocols for Universal Mobile Telecommunications System (UMTS) all-Internet protocol (IP) network. In the existing mobile telecommunications environments, an IPv6-based UMTS all-IP network needs to interwork with other Internet protocol version 4 (IPv4)-based SIP networks. Therefore, mobile SIP applications are typically offered through an overlay structure over the IPv4-Internet protocol version 6 (IPv6) interworking environments. Based on 3GPP 23.228, we propose an IPv4-IPv6 translation mechanism (i.e., SIPv6 translator) that integrates different IP infrastructures (i.e., IPv4 and IPv6) to provide an overlay network for transparent SIP application deployment. In this paper, we present the architecture and the call flows of the SIPv6 translator. An analytic model is proposed to investigate the fault tolerance issue of our approach. Our study provides guidelines to select appropriate number of processors for fault tolerance.

Universal Mobile Telecommunications System (UMTS) supports Internet protocol (IP) multimedia services through IP multimedia core network subsystem (IMS). Since the IMS information is delivered through the general packet radio service (GPRS) transport network, a UMTS mobile station (MS) must activate GPRS packet data protocol (PDP) context before it can register to the IMS network. In the Third-Generation Partnership Project (3GPP) specifications, authentication is performed at both the GPRS and the IMS networks before an MS can access the IMS services. We observe that many steps in this 3GPP "two-pass" authentication procedure are identical. Based on our observation, this paper proposes an one-pass authentication procedure that only needs to perform GPRS authentication. At the IMS level, authentication is implicitly performed in IMS registration. Our approach may save up to 50% of the IMS registration/authentication traffic, as compared with the 3GPP two-pass procedure. We formally prove that the one-pass procedure correctly authenticate the IMS users.

This paper studies the failure restoration of mobility database for Universal Mobile Telecommunications System (UMTS). We consider a per-user checkpointing approach for the home location register (HLR) database. In this approach, individual HLR records are saved into a backup database from time to time. When a failure occurs, the backup record is restored back to the mobility database. We first describe a commonly used basic checkpoint algorithm. Then, we propose a new checkpoint algorithm. An analytic model is developed to compare these two algorithms in terms of the checkpoint cost and the probability that an HLR backup record is obsolete. This analytic model is validated against simulation experiments. Numerical examples indicate that our new algorithm may significantly outperform the basic algorithm in terms of both performance measures.

General packet radio service (GPRS) is a global system for mobile communications (GSM) packet data service. In order to efficiently accommodate GPRS traffic while maintaining the desired service quality of GSM calls, we propose a GPRS bandwidth-allocation strategy called the bandwidth-on-demand (BoD) strategy. The BoD strategy is adaptive to the change of traffic conditions, and thus can dynamically adjust the number of channels for GSM and GPRS traffic. Taking the effect of packet dropping due to movements of mobile stations into account, this paper develops an analytical model to study the BoD performance in terms of GSM-call-blocking probability and GPRS-packet-dropping probability.

In a cellular telecommunications network, the call blocking, forced termination, and call incompletion probabilities are major output measures of system performance. Most previous analytic studies assumed that the handover traffic to a cell is a fixed-rate Poisson process. Such assumption may cause significant inaccuracy in modeling. This paper shows that the handover traffic to a cell depends on the workloads of the neighboring cells. Based on this observation, we derive the exact equation for the handover force-termination probability when the mobile station (MS) cell residence times are exponentially distributed. Then, we propose an approximate model with general MS cell residence time distributions. The results are compared with a previously proposed model. Our comparison study indicates that the new model can capture the handover behavior much better than the old one for small-scale cellular networks.

This paper investigates the discontinuous reception (DRX) mechanism of universal mobile telecommunications system (UMTS). DRX is exercised between the network and a mobile station (MS) to save the power of the MS. The DRX mechanism is controlled by two parameters: the inactivity timer threshold and the DRX cycle. Analytic and simulation models are proposed to study the effects of these two parameters on output measures including the expected queue length, the expected packet waiting time, and the power saving factor. Our study quantitatively shows how to select appropriate inactivity timer and DRX cycle values for various traffic patterns.

This paper describes the mobility management mechanisms for mobile telecommunications networks. There are two major types of mobility: radio network mobility and core network mobility. Radio network mobility supports radio link switching of a mobile user during conversation, and core network mobility provides roaming and tunnel-related management for packet re-routing due to user movement. Impact of mobility on both the radio and the core networks is addressed in this paper. Also, potential research issues on these topics are discussed. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract This paper describes NCTUns, an innovative network simulator and emulator for wireless and mobile networks. Effects of various radio resource management and quality of service (QoS) schemes on higher‐layer protocols and real‐world applications can be easily studied using NCTUns. In this paper, we elaborate on NCTUns simulation methodology, architecture, design, functionalities, performance, and applications. NCTUns simulation for wireless ad hoc, sensor, inter‐vehicle communication networks, GPRS cellular networks, and wireless mesh networks are also illustrated. More details about this tool can be found in http://NSL.csie.nctu.edu.tw/nctuns.html . Copyright © 2005 John Wiley & Sons, Ltd.

To support real-time multimedia services in UMTS all-IP network, 3GPP TR 25.936 proposed two approaches to support real-time serving radio network controller (SRNC) switching, which require packet duplication during SRNC relocation. These approaches significantly consume extra system resources. This paper proposes the fast SRNC relocation (FSR) approach that does not duplicate packets. In FSR, a packet buffering mechanism is implemented to avoid packet loss at the target RNC. We propose an analytic model to investigate the performance of FSR. The numerical results show that packet loss at the source RNC can be ignored. Furthermore, the expected number of packets buffered at the target RNC is small, which does not prolong packet delay.

This paper proposes wireless LAN (WLAN)-based GPRS Support Node (WGSN), as a solution for integrating Third Generation (3G) and WLAN services. We show that the 3G mechanisms can be re-used for WLAN user authentication and network access without introducing new procedures and without modifying the existing 3G network components. We describe the WGSN features and show how they are designed and implemented. To reduce the power consumption and computation complexity of a mobile station (MS), the WGSN applications may not be activated in the MS if they are not used. For an MS-terminated application, a push mechanism is implemented in WGSN, which automatically activates the application at the MS side. An analytic model is proposed to investigate the requirements on the WGSN transmission delay of the push operation. A WGSN prototype has been implemented in the Industrial Technology Research Institute and National Chiao-Tung University Joint Research Center.

To support real-time multimedia services in UMTS all-IP network, Third-Generation Partnership Project TR 25.936 proposed two approaches to support real-time serving radio network controller (SRNC) switching, which require packet duplication during SRNC relocation. These approaches significantly consume extra system resources. This paper proposes the fast SRNC relocation (FSR) approach that does not duplicate packets. In FSR, a packet buffering mechanism is implemented to avoid packet loss at the target RNC. We propose an analytic model to investigate the performance of FSR. The numerical results show that packet loss at the source RNC can be ignored. Furthermore, the expected number of packets buffered at the target RNC is small, which does not prolong packet delay.

Short Message Service (SMS) is one of the most popular mobile data services. This paper develops a Web-based short message system and analyzes the short message transmission delays based on 40 000 measured data collected from commercial operation. We investigate the distributions of SMS round-trip transmission delays. These distributions are roughly approximated by truncated normal, gamma, log-normal, and Weibull distributions with various parameters, which can be utilized in theoretical analysis. Furthermore, with the nonparametric fitting approach, we use the rejection method to develop random number generators for these delays, which can be used in any simulation models that employ SMS transmission delays.

This paper proposes a radio channel assignment scheme called repacking on demand (RoD) for two-tier wireless local loop (WLL) networks. A two-tier WLL overlays a macrocell with several microcells. When a new call arrives at a two-tier WLL with RoD, if no idle channel is available in both the microcell and the macrocell, repacking is performed (i.e., a call in the macrocell is moved to its corresponding microcell), and then the reclaimed macrocell channel is used to serve the new call. An analytic model is proposed to compute the call blocking probability of the two-tier WLL with repacking. This analytic model is validated against simulation experiments. We prove that the blocking probability is not affected by the call holding time distributions, but is only dependent on the mean of the call holding times. Compared with some previous proposed schemes, RoD has low blocking probability and significantly reduces repacking rate.

This paper proposes overflow control schemes to support high-speed downlink packet access (HSDPA) mechanism in the universal mobile telecommunication system (UMTS). To access the UMTS services, a user equipment (UE) communicates with all cells (base stations) in an active set. However, multiple links between the UE and the cells in the active set may reduce the transmission speed due to interference. Third-Generation Partnership Project specification TR 25.950 proposes HSDPA. In this mechanism, the UE only selects one cell (referred to as the serving cell) in the active set for high-speed downlink transmission. In HSDPA, the radio network controller sends the packet frames to the cells in the active set. For the serving cell, the packet frames are forwarded to the UE. On the other hand, every nonserving cell in the active set queues the packet frames in a buffer. If the link quality between the serving cell and the UE degrades below some threshold, the UE selects the best cell in the active set as the new serving cell. Since the nonserving cells do not send packet frames to the UE, their buffers may overflow. In this paper, we propose schemes to address the buffer overflow issue. Our schemes guarantee that when the buffer of a nonserving cell is full, the previously received packet frames in the buffer can be safely dropped, and after the UE has switched wireless link to the new serving cell, no packet frames are lost.

In a 3G cellular network, the visitor location registers (VLRs), the gateway location registers (GLRs), and the home location registers (HLRs) from a three-level mobility database structure. When users leave a GLR/VLR service area, deregistration with GLR/VLR is required. Deregistration may create significant traffic in the network, especially the traffic between GLR and a HLR, which is the remote/international traffic. In this paper, we propose a hierarchical implicit deregistration scheme with a first/subsequent registration in 3G cellular networks to effectively eliminate deregistration traffic. An analytic model is proposed to carry out the performance of the proposed scheme. Our study shows that the proposed scheme not only reduces the local deregistration traffic between the GLR and the VLR, but also reduces the remote/international deregistration traffic between the HLR and the GLR. This is especially true when the ratio of the cost of the remote/international traffic between the GLR and the HLR to the cost of local traffic between the VLR and the GLR is high.

In mobile telecommunications operation, radio channels are scarce resources and should be carefully assigned. One possibility is to deploy the hierarchical cellular network (HCN). We study a HCN channel assignment scheme called repacking on demand (RoD). RoD was originally proposed for wireless local loop networks. We expend this work to accommodate mobile HCN. A simulation model is proposed to study the performance of HCN with RoD and some previously proposed schemes. Our study quantitatively indicates that RoD may significantly outperform the previous proposed schemes.

WIRELESS communications have made spectacular progress in recent years. In particular, the merge of various wireless communication systems and the Internet has become more critical so that users can enjoy all kinds of services in the Internet while owning mobility. For example, modern wireless networks can support Internet applications for web accessing and multimedia services. Many issues need to be addressed for such combinations. Host mobility adds a new dimension to many research issues, such as network protocols, resource managements, Web access, and multimedia transmission. For different applications, diverse traffic types should be supported. Lightweight mobile computing devices, such as PDAs and Bluetooth, will be attached to the Internet. Various wireless communication devices, such as Bluetooth and wireless LANs, will be hooked up to the Internet. All these issues bring new challenges. This special section is targeted at the related issues in wireless Internet. More than 50 submissions were received, and 10 papers were accepted in this special issue. The first five papers cover the service issues in wireless Internet. The paper by B. Emako, R. Glitho, and S. Pierre discusses the design, implementation, and evaluation issues of wireless Internet telephony. Y. Lee and I.F. Akyildiz present a new scheme to reduce the link and signaling costs in Mobile IP. The paper by P. McKinley, U.I. Padmanabhan, N. Ancha, and S.M. Sadjadi describes a composable proxy infrastructure that enables mobile Internet users to collaborate via heterogeneous devices and network connections. V.A. Chitre and J.N. Daigle present an analytical model to assess GPRS’s capability of supporting IP-based Internet services. Performance optimization of VoIP calls over wireless links using H.323 protocol is proposed by S.K. Das, E. Lee, K. Basu, and S.K. Sen. Thenextsetof threepaperscovers issuesrelatedtowireless LANs and sensor networks. The important coverage issue concerning the deployment of sensors in a wireless ad hoc sensor network is addressed in the first paper by X.-Y. Li, P.-J. Wan, and O. Frieder. A polling mechanism to support QoS in IEEE 802.11 wireless LANs is proposed by S.-C. Lo, G. Lee, and W.-T. Chen. Formation of scatternets for Bluetooth-based wireless networks is discussed in the paper by C. Petrioli, S. Basagni, and I. Chlamtac. The last set of two papers covers management issues in mobile networks. An analysis for movement-based mobility management in mobile networks is discussed in the first paper by Y. Fang, who makes a thorough numerical analysis for finding the optimal mobility management under various network operation scenarios possible. Admission control for schedulingbursty traffic inCDMAsystems isdiscussed in the paper by Y.-K. Kwok and V.K.N. Lau, where six efficient rate allocation schemes are proposed. Finally, wewould like to take the opportunity to thank the contributingauthors, reviewers, theAreaEditor,Dr. S.L.Min, and the Editor-in-Chief, Professor J.-L. Gaudiot. Without their support, this special section would not be possible.

In the Universal Mobile Telecommunication System (UMTS), authentication functions are utilized to identify and authenticate a mobile station (MS) and validate the service request type to ensure that the user is authorized to use the particular network services. The authenticating parties are the authentication center (AuC) in the home network and the MS. In the UMTS, the serving general packet radio service support node (SGSN) accesses the AuC to obtain the authentication data, and delegates the AuC to perform mutual authentication with the MS. Since the cost for accessing AuC is expensive, the SGSN may obtain an array of authentication vectors (AVs) at a time so that the number of accesses can be reduced. On the other hand, if the size K of the AV array is large, the AV array transmission from the AuC to the SGSN may be expensive. Thus, it is desirable to select an appropriate K value to minimize the authentication network signaling cost. We propose an analytic model to investigate the impact of K on the network signaling traffic, which is validated by simulation experiments. Then, we propose an automatic K-selection mechanism that dynamically selects the size of the AV array to reduce the network signaling cost. Our study indicates that the automatic K-selection mechanism effectively identifies appropriate size of the authentication vector array.

In wireless data transmission, the capacity of wireless links is typically limited. Since many applications exhibit temporal locality for data access, the cache mechanism can be built in a wireless terminal to effectively reduce the data access time. This paper studies the cache performance of the wireless terminal by considering a business-card application. We investigate the least-recently used replacement policy and two strongly consistent data access algorithms called poll-each-read and callback. An analytic model is proposed to derive the effective hit ratio of data access, which is used to validate against simulation experiments. Our study reports how the data access rate and the data update distribution affect the cache performance in a wireless terminal.

In general packet radio service (GPRS), a mobile station (MS) is tracked at the cell level during packet transmission, and is tracked at the routing-area (RA) level when no packet is delivered. A READY timer (RT) mechanism was proposed in 3GPP 23.060 to determine when to switch from cell tracking to RA tracking. In this mechanism, a threshold interval T is defined. If no packet is delivered within T, the MS is tracked at the RA level. When a packet arrives, the MS is tracked at the cell level again. However, the RT mechanism has a major fallacy in that the RTs in both the MS and the serving GPRS support node may lose synchronization. This paper considers another mechanism called READY counter (RC) to resolve this problem. In this approach, a threshold K is used. Like the RT approach, the MS is tracked at the cell level during packet transmission. If no packets are delivered after the MS has made K cell crossings, the MS is tracked at the RA level. We also devise an adaptive algorithm called dynamic RC (DRC). This algorithm dynamically adjusts the K value to reduce the location update and paging costs. We propose analytic and simulation models to investigate RC, RT, and DRC. Our study indicates that RC may outperform RT. We also show that DRC nicely captures the traffic-mobility patterns and always adjusts the K threshold close to the optimal values.

This paper proposes overflow control scheme to support high-speed downlink packet access (HSDPA) mechanism in the Universal Mobile Telecommunication System (UMTS). To access the UMTS services, a user equipment (UE) communicates with all cells (base stations) in an active set. However, multiple links between the UE and the cells in the active set may reduce the transmission speed due to interference. 3GPP specification TR 25.950 proposes HSDPA. In HSDPA, the UE only selects one cell (referred to as the serving cell) in the active set for high-speed downlink transmission. In this mechanism, the radio network controller sends the packet frames to the cells in the active set. For the serving cell, the packet frames are forwarded to the UE. On the other hand, every non-serving cell in the active set queues the packet frames in a buffer. If the link quality between the serving cell and the UE degrades below some threshold, the UE selects the best cell in the active set as the new serving cell. Since the non-serving cells do not send packet frames to the UE, their buffers may overflow. In this paper, we propose the scheme to address the buffer overflow issue. Our scheme guarantees that when the buffer of a non-serving cell is full, the previously received packet frames in the buffer can be safely dropped, and after the UE has switched wireless link to the new serving cell, no packet frames are lost.

Personal Number (PN) service or Follow-me service allows a user to access telecommunication services with any terminal (e.g., fixed telephones or mobile phones) in any location within the service area. To provide this feature, the PN user needs to manually register with a phone number every time he/she enters a new location. If the user forgets to register the new phone number, the incoming calls will be misrouted. To provide user-friendly follow-me service, this paper proposes an automatic follow-me service (AFS) approach that automatically updates the PN records in the Follow-me database. The significance of our approach is that AFS can be integrated with existing Follow-me databases to automate PIN services offered by different PSTN service providers. We show how AFS can be implemented by using the Voice over IP and Bluetooth technologies. Then, we propose an analytic model to investigate the performance of AFS. The analytic results are validated by simulation experiments. Our study suggests how to select polling frequency to optimize the AFS performance.

This paper proposes an analytic model to compute the loss probability for wireless local loop (WLL) with a finite number of subscribers. The number of trunks between the WLL concentrator and the base station controller is less than the total number of radio links in the WLL. This model is validated against the simulation results. The execution of our model is efficient compared with simulation. However, its time complexity is higher than several existing analytic models that approximate the loss probability for WLL. Therefore, we design an efficient WLL network planning procedure (in terms of time complexity and accuracy) that utilizes the approximate analytic models to provide small ranges for selecting the values of system parameters. Our model is then used to accurately search the operation points of WLL within the small ranges of the system parameter values. This paper proves that the performance of WLL with limited trunk capacity and finite subscriber population is not affected by the call holding time distributions. Based on our model, we illustrate WLL design guidelines with several numerical examples.

This paper investigates the fraudulent usage of mobile telecommunications services due to cloned subscriber identity modules (SIMs). In GSM or the Universal Mobile Telecommunication System (UMTS), a mobile phone or mobile station uses its SIM to gain network access through authentication. If the SIM of a legal user is cloned, then the cloned SIM can be used for GSM/UMTS authentication and fraudulent usage may occur. Under the existing GSM/UMTS mobility management and call setup procedures, we show how quickly the fraudulent usage can be detected. We also propose a simple solution to speed up the detection of potential fraudulent usage.

This paper presents a new adaptive bandwidth allocation scheme to prevent handoff failure in wireless cellular networks, known as the measurement-based preassignment (MPr) technique. This technique is particularly useful in micro/pico cellular networks which offers quality-of-service (QoS) guarantee against call dropping. The proposed MPr scheme distinguishes itself from the well-known guarded channel (GC) based schemes in that it allows the handoff calls to utilize a prereserved channel pool before competing for the shared channels with new call arrivals. The key advantage of the proposed MPr scheme is that it enables easy derivation of the number of channels that needs to be reserved for handoff based on a predetermined handoff dropping probability, without the need for solving the often complex Markov chain required in GC schemes, thus, making the proposed MPr scheme simple and efficient for implementation. This is essential in handling multiple traffic types with potentially different QoS requirements. In addition, the MPr scheme is adaptive in that it can dynamically adjust the number of reserved channels for the handoff according to the periodical measurement of the traffic status within a local cell, thus completely eliminating the signaling overhead for status information exchange among cells mandated in most existing channel allocation schemes. Numerical results and comparisons are given to illustrate the tradeoff.

Abstract General packet radio service (GPRS) provides efficient access to the integrated services Internet from wireless networks. When the GPRS‐attached mobile station attempts to send or receive data, a packet data protocol (PDP) context shall be established. The GPRS session management (SM) supports the PDP context handling, which consists of PDP context activation, deactivation, and modification procedures. In this paper, we propose an SM software architecture for the serving GPRS support node. Our design goals are to achieve compatibility, modularity, and flexibility. More importantly, our approach can accommodate the design of the SM software architecture for third‐generation wireless networks. Copyright © 2001 John Wiley & Sons, Ltd.

In a personal communications service (PCS) network, mobility databases called visitor location registers (VLRs) are utilized to temporarily store the subscription data and the location information for the roaming users. Because of user mobility, it is possible that the VLR is full when a mobile user arrives. Under such a circumstance, the incoming user has no VLR record and thus cannot receive PCS services. This issue is called VLR overflow. To resolve the VLR overflow problem, a VLR record can be selected for replacement when the VLR is full and then the reclaimed storage is used to hold the record of the requesting user. This paper considers the most idle replacement policy to provide services to mobile users without VLR records. In this policy, the record with the longest idle time is selected for replacement. We propose an analytic model to investigate the performance of this replacement policy. The analytic results are validated against simulation experiments. The results indicate that our approach effectively resolves the VLR overflow problem.

As wireless technology advances, wireless products are integrated with enterprise networking to offer cordless terminal mobility. Most corporations have deployed wireless PBXs at the departmental level. However, the mobility management mechanism that integrates these facilities at the corporation level may not be available. This paper describes a mobility management mechanism for an enterprise wireless telephone network. We show how, to modify the call model of the private branch exchange (PBX) to accommodate mobility management for an enterprise network. Our design was implemented on a commercial PBX product called Jupiter. An analytical model is proposed to evaluate the performance of the implemented system. Our study shows that with a large number of WPBXs and long Internet message delays, the misrouting probability can be limited to within 1%. This performance result is considered satisfactory.

In a cellular phone system, mobility databases called visitor location registers (VLRs) are used to temporarily hold the subscription information of the roaming users who visit the service area of the VLR. When the users leave the VLR area, the corresponding records in the VLR are deleted. Due to user mobility, the capacity of the VLR may not be large enough to hold information for all visitors in the VLR area at some time periods. This issue is called VLR overflow. This paper describes a record replacement policy to allow mobile users to receive services in the VLR overflow situation. We utilize analytic modeling to investigate the performance of the replacement policy. The study indicates that our approach effectively eliminates the VLR overflow problem with insignificant extra overhead.

Wireless communications have made spectacular progress in recent years. In particular, the merge of various wireless communication systems and the data networks has become more critical so that users can enjoy all kinds of data services while owning mobility. For example, modern wireless networks can support Internet applications such as voice over IP (VoIP), web accessing and multimedia services. In this environment, a customer may use a wireless handheld device to access data services from the application server through the mobile network. To support the novel services mentioned above, service platforms and resource management mechanisms for existing mobile networks must be re-evaluated and enhanced. This special issue concentrates on wireless network applications and modeling. Five papers have been selected to address two major topics for supporting advanced mobile services. The first two papers investigate call admission control schemes that support users requesting various types of applications. The remaining four papers address how wireless and mobile network architectures can support Internet-based data applications. In the first paper, Bartolini and Chlamtac describe how to improve call admission control policies procedures by using handoff rate information in a wireless network. A general Markov Decision Process (MDP) model is used as an instrument to analytically compare the behavior of call admission control policies. If the handoff rate arriving to a cell is proportional to the occupancy level of the adjacent cells, then this approach allows a wide class of policies to explicitly incorporate the dependency between the handoff rate and the system state. Based on this model, some well known non-preemptive prioritization schemes are analyzed. In the second paper, Hou and Fang propose mobility-based call admission control schemes for wireless mobile networks. Multiple classes of mobile users (i.e. pedestrians and vehicular travelers) are considered in this study. The concept of influence curve is introduced to characterize the influence an ongoing call exerts on the adjacent cells for future resource usage. Based on this concept, the channel reservation can be dynamically adjusted. To overcome potential congestion, the authors also propose a new call bounding scheme to place a direct limitation on the number of new calls admitted to a cell. Four CAC schemes are proposed and analyzed by both analytical and simulation study. The results indicate that the new schemes are more effective in providing QoS than other previously known schemes. In the third paper, Pang et al. integrate the existing GSM service with Voice over IP (VoIP) features based on media gateway control protocol (MGCP). With the signaling protocol translation mechanism provided by the MGCP signaling gateway, the authors demonstrate how to interwork the MGCP elements with the home location register, visitor location register and mobile switching center in the GSM network. The message flows for GSM-IP registration, call origination, call delivery, call release and inter-system handoff procedures are implemented. The authors show the feasibility of integrating GSM with the MGCP-based VoIP network without modifying the GSM network. Performance enhancing proxies have drawn considerable interests from the network community as an effective approach to improve user experience in cellular networks. In the fourth paper, Jiang et al.. incorporate performance enhancing proxies into cellular IP networks. In this paper, the authors study the placement of proxy servers, especially the approach of incorporating proxies into cellular networks, which allows better, faster, and more secure proxy services. Various factors are discussed, including when to place proxies inside cellular networks, the information requirements of the proxies, the network requirements for supporting the proxy functions, and mobility management. Using GPRS as an example, the authors lay out a procedure for adding proxies into data transmission path in cellular networks. In the fifth paper, Misra et al.. provide application-centric analysis of IP-based mobility management techniques. The authors consider three applications: VoIP, mobile Web access and mobile server-based data transfers. Based on these applications, the authors evaluate the applicability of various IP-based mobility management mechanisms. The study indicates that diversity in the mobility-related requirements ensures that no single mobility solution is universally applicable, and the authors recommend a hierarchical mobility architecture based on Dynamic Mobility Agent (DMA). The proposed architecture efficiently manages intra-domain mobility and multiple application-based binding protocols for supporting inter-domain mobility. In the last paper, David Lee and William Lee share their experience in integrating global wireless systems with IP. They propose a standard-based all-IP wireless network architecture to support both data and voice. This architecture is wireless technology independent (can be applied for CDMA, GSM and TDMA) and can be deployed with minimum efforts with the combination of existing IETF and telecom standards. The mapping of PLMN and IP based addressing will be done through HLR to translate phone number based address (MIN) to IP based address. Vocoder issue can be resolved by using end to end solution or by providing an universal vocoder gateway in the inter-system network to minimize delay and improve performance. A trial hosted by Vodafone with Cisco, Hyundai and Telos was conducted in Reno, Nevada, USA. The trial reveals encouraging results on system integration time and performance. We would like to express our sincere thanks to all the authors who submitted papers, and the reviewers who provided revision reports for this special issue. Also, we would like to thank Mohsen Guizani, the Editor-in-Chief, and Mark Hammond, the Publishing Editor, for their assistance in editing this special issue. The work of Yi-Bing Lin was supported in part by MOE Program of Excellence Research under contract 89-E-FA04-4, CCL/ITRI, Ericsson, InterVideo, FarEastone, National Science Council under contract NSC 89-2213-E-009-203, the Lee and MTI Center for Networking Research, NCTU.

Abstract This paper describes mobility management for the third‐generation mobile networks. We focus on the evolution from General Packet Radio Service (GPRS) to Universal Mobile Telecommunication System (UMTS). In this evolution, the radio access network UTRAN has been introduced, and radio‐related management is moved from the core network to UTRAN. We elaborate on how this architecture change affects the mobility management functionality, including the attach and detach procedures, location update, serving radio network controller relocation and intersystem change between GPRS and UMTS. Copyright © 2001 John Wiley & Sons, Ltd.

This article provides an overview of General Packet Radio Service (GPRS). GPRS reuses the existing GSM infrastructure to provide end-to-end packet-switched services. Benefits of GPRS include efficient radio usage, fast set-up/access time and high bandwidth with multiple timeslots. GPRS also provides a smooth path for GSM evolution to the third generation mobile network. Specifically, a third generation network can continue to utilize the GPRS IP backbone network. We describe the GPRS network nodes and the interfaces among these nodes. Deployment issues for GPRS are also elaborated. Copyright © 2001 John Wiley & Sons, Ltd.

Abstract Based on media gateway control protocol (MGCP), this paper describes GSM‐IP, a voice over IP service for GSM mobile network. With the signaling protocol translation mechanism provided by the MGCP signaling gateway, we demonstrate how to interwork the MGCP elements with the home location register, visitor location register and mobile switching center in the GSM network. Then we present the message flows for GSM‐IP registration, call origination, call delivery, call release and inter‐system handoff procedures. We show the feasibility of integrating GSM with the MGCP‐based VoIP network without modifying the GSM network. Furthermore, our approach does not introduce new protocol primitives to MGCP. Copyright © 2001 John Wiley & Sons, Ltd.

The emerging next generation of wireless cellular networks has to provide the quality-of-service (QoS) for a variety of applications. This paper addresses bandwidth allocation for a voice and data integrated mobile wireless network. Specifically, we propose a new bandwidth allocation scheme called dual-threshold reservation (DTR) scheme, which is a natural extension from well-known guarded channel (GC) scheme used in cellular networks supporting voice traffic. The basic idea is to use two thresholds, one for reserving channels for voice handoff, while the other is used to block data traffic into the network in order to preserve the voice performance in terms of handoff dropping and call blocking probabilities. We develop an analytical model which can obtain its performance using an iterative technique. Results obtained from the analytical model are used to illustrate the system tradeoff.

This paper proposes a new approach to simplify the two-dimensional random walk models capturing the movement of mobile users in personal communications services (PCS) networks. Analytical models are proposed for the new random walks. For a PCS network with hexagonal configuration, our approach reduces the states of the two-dimensional random walk from (3n/sup 2/+3n-5) to n(n+1)/2, where n is the layers of a cluster. For a mesh configuration, our approach reduces the states from (2n2-2n+1) to (n/sup 2/+2n+4)/4 if n is even and to (n/sup 2/+2n+5)/4 if n is odd. Simulation experiments are conducted to validate the analytical models. The results indicate that the errors between the analytical and simulation models are within 1%. Three applications (i.e., microcell/macrocell configuration, distance-based location update, and GPRS mobility management for data routing) are used to show how our new model can be used to investigate the performance of PCS networks.

In a dual band personal communications services (PCS) network, heavy traffic areas are covered by microcells which overlay macrocells. In such a network, microcells and macrocells utilize different frequency bands. We propose an analytic model to study the performance of a dual band PCS architecture. Our model assumes that a PCS subscriber has a general residence time distribution in a microcell and the macrocell residence time distribution is derived from the microcell residence time distribution. An iterative algorithm is used to compute the overflow traffic from a microcell to its overlaid macrocell. Then, the call incompletion probability is computed by a macrocell model based on the overflow traffic. Our study indicates that the variance of the microcell residence time distribution and the number of microcells covered by a macrocell have significant effects on the call incompletion probability.

Global system for mobile communications (GSM) call reestablishment service allows a mobile station to resume a call in which the radio link has been temporarily interrupted due to interference or bad signal (which is referred to as an interrupted call). This service increases end user satisfaction and network quality perception. We propose analytic models to study the performance for call reestablishment service. Our study indicates that call reestablishment can significantly reduces dropping for interrupted calls.

This paper presents a formula for the computation of handoff rate in PCS networks under generally distributed call holding times and generally distributed cell residence times. This formula can be used to study the handoff traffic rate. It shows that applying the exponential distribution underestimate the handoff traffic rate, hence the computed handoff call blocking probability will be lower than the actual handoff call blocking probability. This suggests the necessity of the sensitivity study with respect to the variance of channel occupancy time in the PCS network analysis and design.

This paper studies the database failure recovery procedure for cellular phone networks as part of the EIA/TIA IS-41 standard. We show that, under some cost assumptions, a periodic update interval should be chosen to be approximately equal to the call interarrival time, with more frequent updates for more unreliable system. We also show that the cost of an optimized system is relatively small and stable, if the system is even moderately reliable. Finally, if the system is at least moderately reliable, the effects of call origination rate and the rate at which location areas are crossed are rather small, assuming that the periodic update interval was chosen as stated above. Thus in such cases, optimization of the size of the location area can be made independent of the optimization of the periodic update process.

This paper presents a study of channel occupancy times and handoff rate for mobile computing in MC (Mobile Computing) and PCS (Personal Communications Services) networks, using general operational assumptions. It is shown that, for exponentially distributed call holding times, a distribution more appropriate for conventional voice telephony, the channel occupancy times are exponentially distributed if and only if the cell residence times are exponentially distributed. It is further shown that the merged traffic from new calls and handoff calls is Poisson if and only if the cell residence times are exponentially distributed, too. When cell residence times follow a general distribution, a more appropriate way to model mobile computing sessions, new formulae for channel occupancy time distributions are obtained. Moreover, when the call holding times and the cell residence times have general (nonlattice) distributions, general formulae for computing the handoff rate during a call connection and handoff call arrival rate to a cell are given. Our analysis illustrates why the exponential assumption for call holding time results in the underestimation of handoff rate, which then leads to the actual blocking probabilities being higher than the blocking probabilities for MC/PCS networks designed using the exponential distribution approximation for call holding time. The analytical results presented in this paper can be expected to play a significant role in teletraffic analysis and system design for MC/PCS networks.

A personal communications services (PCS) network system constantly tracks the locations of the mobile stations (MS) so that incoming calls can be delivered to the target mobile stations. The overall architecture of the PCS mobility management in GSM is presented. In general, a two-level database is used to store the mobile station location information. The mobile station location update procedure and the call delivery procedure are described in detail. In case of location database failure, incoming calls may be lost. The database failure restoration procedure to reduce the number of lost calls in GSM are also described. Moreover, an efficient home location register (HLR) failure recovery procedure which utilizes the MS movement information to speedup the recovery procedure is also presented.

Previous performance studies of PCS channel allocation assumed that call holding times have an exponential distribution. The exponential call holding time assumption is justified for existing cellular systems, where wireless calls are charged based on the length of the call holding time. Future PCS systems may exercise flat rate billing, and consequently a more general distribution is desirable to model the call holding times. This paper models the call holding times by the Erlang distribution (a generalization of the exponential distribution) to investigate the effect of the variance of the call holding times on the call completion probability. Our analysis indicates that the call completion probability decreases as the variance of the call holding times decreases. This effect becomes more pronounced as the variance of the cell residence times decreases.

It is well known that, due to the mobility of a portable and limited channel availability, calls of portables may not be completed due to being blocked or terminated during the call initiation or the handover process. The characteristics of the call-completion and call-holding times for both a complete call and an incomplete call are of critical importance for establishing the actual billing process in the PCS network. We derive the call-completion probability (hence, call-dropping probability) and the effective call-holding time distributions for complete/incomplete calls with a general cell-residence time and a general call-holding time are analyzed, and general computable formulas are obtained. We show that when call-holding times are Erlang distributed, easy-to-compute formulas for the probability of a call completion and the expected effective call-holding times for both a complete call and an incomplete call can be derived.

—————————— ✦ —————————— One of the most challenging and interesting recent trends in the computer and telecommunications industries is the integration of mobile communications and computing. The resulting distributed network, referred to as a mobile computing system, is in more that one way fundamentally different from conventional wired computer networks. Wireless connectivity enhances the functionality of computing equipment by freeing communication from the location constraints of the wireline infrastructure. By changing this basic characteristic, mobile computing systems operate on a set of assumptions made by traditional computing systems, requiring researchers and users to redefine their model of networked computing. The successful use of mobile computing faces several challenges, among them:

In a personal communication service (PCS) network, the call completion probability and the effective call holding times for both complete and incomplete calls are central parameters in the network cost/performance evaluation. These quantities will depend on the distributions of call holding times and cell residence times. The classical assumptions made in the past that call holding times and cell residence times are exponentially distributed are not appropriate for the emerging PCS networks. This paper presents some systematic results on the probability of call completion and the effective call holding time distributions for complete and incomplete calls with general cell residence times and call holding times distributed with various distributions such as gamma, erlang, hyperexponential, hyper-erlang, and other staged distributions. These results provide a set of alternatives for PCS network modeling, which can be chosen to accommodate the measured data from PCS field trials. The application of these results in billing rate planning is also discussed.

Location tracking operations in a personal communications services (PCSs) network are expensive. Several strategies have been proposed to reduce the location update cost. This paper studies a special case of a location tracking algorithm called the alternative location algorithm. This special case is referred to as the two location algorithm (TLA). An analytical model is proposed to compare the performance of the TLA and the IS-41 protocol. Our study indicates that the performance of the TLA is significantly affected by the user moving patterns and the call traffic. If the user mobility is higher than the call frequency or the user tends to move back to the previously visited registration areas, then the TLA may significantly outperform IS-41. We also observe that the variance of the portable residence times in registration areas has an impact on the performance of the TLA (i.e., better performance is expected for larger variance).

Location tracking operations in a personal communications services network are expensive. Several strategies have been proposed to reduce the location update cost. This paper studies a special case of a location tracking algorithm called the alternative location algorithm. This special case is referred to as the two location algorithm (TLA). An analytical model is proposed to compare the performance of TLA and the IS-41 protocol. Our study indicates that the performance of TLA is significantly affected by the user moving patterns and the call traffic. If the user mobility is higher than the call frequency or the user tends to move back to the previously visited registration areas, then TLA may significantly outperform IS-41. We also observe that the variance of the portable residence times in registration areas has impact on the performance of TLA (i.e. better performance is expected for larger variance). The larger the variance the better the performance of TLA.

This paper addresses two important PCS cost and performance issues: (1) are blocking probabilities (for new call blocking, forced termination or call completion) appropriate for PCS network performance measurement? (2) Should PCS service providers offer discounts to phone calls that are force terminated? In order to do that we derive the effective call holding time distributions for complete/incomplete calls by using an analytic model. We assume that the cell residence times have a general distribution so that the measured data from the field trials, after a second order approximation, can be used to drive our model. Our study on the effective call holding time distributions indicates that (1) blocking probabilities do not provide sufficient information to evaluate the performance of a PCS network, and that output measures, such as expected effective call holding times for complete/incomplete calls, are desirable; (2) for a PCS network with moderate user mobility, the service provider can offer substantial discounts to incomplete calls (to increase the user satisfaction) without significantly reducing the profit margin. A quantitative analysis is also provided that can be used to determine the discount factor.

The signaling traffic between access managers (AMs) and home location register (HLR) are SS7 signaling messages in the personal access communication system (PACS) system. These signaling messages are for the transportation of subscriber unit (SU) registration, call origination, and call delivery, and also for authentication in these procedures. The signaling traffic is referred to mobility management traffic. In addition, the performance of mobility management traffic plays an essential role in the performance of the whole PACS system network. In this paper, we propose an M/G/1 traffic analysis on the PACS mobility traffic between AMs and HLR by using the mobile, business, and residential subscriber profiles. In addition, four performance metrics are investigated to observe the mobility characteristics with various subscriber profiles, which include waiting times at the AM and HLR average query response times, average update response times, and the expected numbers of messages per second exchanged between the AM and HLR. Finally, some observations and comments are made for the PACS system.

The FCC has allocated the spectrum between 1850-1910 and 1930-1990 MHz for licensed personal communications services (PCS) and the band between 1920-1930 MHz for unlicensed PCS (UPCS). This paper describes a polling deregistration protocol for a wireless access communications network which would support interoperability between licensed personal communications services (PCS) and unlicensed-PCS (UPCS). We show how the protocol can be efficiently implemented in the personal access communications system (PACS) for licensed PCS and in the PACS-Unlicensed Version B (PACS-UB). An analytical model is proposed to analyze the performance of the polling protocol. A cost function is derived, which can be used to estimate the optimal polling frequency.

This paper introduces a mobility tracking mechanism that combines a movement-based location update policy with a selective paging scheme. Movement-based location update is selected for its simplicity. It does not require each mobile terminal to store information about the arrangement and the distance relationship of all cells. In fact, each mobile terminal only keeps a counter of the number of cells visited. A location update is performed when this counter exceeds a predefined threshold value. This scheme allows the dynamic selection of the movement threshold on a per-user basis. This is desirable as different users may have very different mobility patterns. Selective paging reduces the cost for locating a mobile terminal in the expense of an increase in the paging delay. We propose a selective paging scheme which significantly decreases the location tracking cost under a small increase in the allowable paging delay. We introduce an analytical model for the proposed location tracking mechanism which captures the mobility and the incoming call arrival patterns of each mobile terminal. Analytical results are provided to demonstrate the cost-effectiveness of the proposed scheme under various parameters.

Complex models may have model components distributed over a network and generally require significant execution times. The field of parallel and distributed simulation has grown over the past fifteen years to accommodate the need of simulating the complex models using a distributed versus sequential method. In particular, asynchronous parallel discrete event simulation (PDES) has been widely studied, and yet we envision greater acceptance of this methodology as more readers are exposed to PDES introductions that carefully integrate real-world applications. With this in mind, we present two key methodologies (conservative and optimistic) which have been adopted as solutions to PDES systems. We discuss PDES terminology and methodology under the umbrella of the personal communications services application.

Abstract We identify three goals for the graphical user interface (GUI) of a network simulation environment: user friendliness, model re‐usability, and application extensibility. We address the user‐friendliness issue by proposing a simple yet efficient approach to setup parameters for the simulation models. We address the application extensibility issue with a two‐layer GUI architecture. The two layers are loosely coupled, and the first layer can be easily replaced without affecting the other components of the simulation environment. The concept of subnetwork is used to address the model reusability issue. Unlike most existing simulation packages, where a subnetwork is simply a method to group the nodes, the subnetwork construct in our approach is a first‐class citizen in the simulation environment (i.e., all operations for a basic node also apply to a subnetwork). The port concept is used to define the I/O relationship between a subnetwork and the outside world. Parameter dialog boxes are used to set up the parameters for a subnetwork conveniently. Finally, a simple stack mechanism is used to measure subnetwork‐wide output statistics.

Most small-scale simulation applications are implemented by sequential simulation techniques. As the problem size increases, however, sequential techniques may be unable to manage the time complexity of the simulation applications adequately. It is natural to consider re-implementing the corresponding large-scale simulations using parallel techniques, which have been reported to be successful in reducing the time complexity for several examples. However, parallel simulation may not be effective for every application. Since the implementation of parallel simulation for an application is usually very expensive, it is required to investigate the performance of parallel simulation for a particular application before re-implementing the simulation. The Chandy-Misra parallel, discrete-event simulation paradigm has been utilized in many large-scale simulation experiments, and several significant extensions have been based on it. Hence the Chandy-Misra protocol is adopted here as a basic model of parallel simulation to which our performance prediction techniques are applied. For an existing sequential simulation program based on the process interaction model, this paper proposes a technique for evaluating Chandy-Misra parallel simulation without actually implementing the parallel program. The idea is to insert parallelism analysis code into the sequential simulation program. When the modified sequential program is executed, the time complexity of the parallel simulation based on the Chandy-Misra protocol is computed. Our technique has been used to determine whether a giant Signaling System 7 simulation (sequential implementation) should be re-implemented using the parallel simulation approach.>

In a personal communication services (PCS) network, a set of channels is assigned to every cell. When a phone call arrives, it consumes a channel until the end of the conversation. If no channel is available, the call is dropped. In many cases, channels may return shortly after a call is dropped. Thus, if some buffering mechanism is introduced to the channel allocation algorithm, a cell may accommodate more phone calls. This is referred to as call request buffering. The paper proposes both analytical and simulation models to study the impact of two call request buffering schemes. The results indicate the potential to greatly improve network performance (i.e., reducing the call blocking probability) by increasing the call-setup period by a reasonably small amount. For the offered load engineered at 1% blocking probability, call request buffering carries 5%-50% more load compared with the system without buffering.>

We propose an auxiliary strategy, called per-user caching, for locating users who move from place to place while using Personal Communications Services (PCS). The caching strategy augments the basic location strategy proposed in existing standards such as GSM and IS-41, with the objective of reducing network signaling and database loads in exchange for increased CPU processing and memory costs. Since technology trends are driving the latter costs down, the auxiliary strategy will become increasingly attractive. The idea behind caching is to reuse the information about a called user's location for subsequent calls to that user, and is useful for those users who receive calls frequently relative to the rate at which they change registration areas. This idea attempts to exploit the spatial and temporal locality in calls received by users, similar to the idea of exploiting locality of file access in computer systems. We use a reference PCS architecture and the notion of a user's local call-to-mobility ratio (LCMR) to quantify the costs and benefits of using caching and classes of users for whom it would be beneficial. We also present two simple algorithms for estimating users' LCMR and the situation in which each is preferable. We show that under a variety of assumptions caching is likely to yield significant net benefits in terms of reduced signaling network traffic and database loads.>

In his feature article, Fujimoto pointed out that the success of parallel simulation depends not only on the speedup that can be achieved through parallel simulation but also on the effort required to develop the parallel code. The general simulation community will only recognize parallel simulation technology if several practical simulation applications are found such that the total cost of the code development and code execution for parallel simulation is much less than the cost of sequential simulation. The sequential execution times of most examples listed in Table II in the feature article were less than two hours. It is difficult to justify parallel simulation as the right approach to follow if one needs to spend one additional day (or more) to develop parallel code in order to reduce a two hour execution time to several minutes. Most parallel simulation research focuses on reducing execution time of parallel simulation. Fujimoto proposed several approaches to address the parallel code development issue. I will consider this issue in a different aspect as a supplement. In addition, I will discuss how to predict the performance of parallel simulation, an issue not explicitly discussed in the feature article. Another issue not addressed in the feature article is the distributed computing platform for parallel simulation. Many examples listed in Table II in the feature article were run on shared memory architectures, and none of the examples were run on a network of workstations, a widely used hardware platform which cannot be ignored by parallel simulation researchers. It is difficult to gain acceptable speedup for parallel simulation in a network of workstations due to long communication delays. One possible solution is to connect the workstations using a high speed network. Another solution is to carefully map the processes to the processors such that inter-processor communications are reduced. How to do the latter efficiently is still an open issue. INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.

Lookahead is the ability of a process to predict its future behavior. The feasibility of implicit lookahead for non-FCFS stochastic queuing systems is demonstrated. Several lookahead exploiting techniques are proposed for round-robin (RR) system simulations. An algorithm that generates lookahead in O(1) time is described. Analytical models and experiments are constructed to evaluate these techniques. A lookahead technique for preemptive priority (PP) systems is evaluated using an analytical model. The performance metric for these techniques is the lookahead ratio, which is correlated with other performance measures of more direct interest, such as speedup. The analyses show that using implicit lookahead can significantly improve the lookahead ratios of RR and PP system simulations.>

The problem is discussed of how the use of a new data structure, the codeword structure, can help improve the performance of quicksort when the records to be sorted are long and the keys are alphanumeric sequences of bytes. The codeword is a compact representation of a key with respect to some codeword generator. It consists of a byte for a character count of equal bytes, a byte for the first nonequal byte, and a pointer to the record. It is shown how the ordering of keys is preserved by an adequate choice of the code generator and how this can be applied to the quicksort algorithm. An analysis of the potential saving son various architectures and actual measurements shows the improvements that can be attained by using codewords rather than pointers. Architecturally independent parameters, such as the number of bytes to be compared, the number of swaps, architecture-dependent parameters such as caches and their write policies, and compiler optimizations such as in-line expansion and register allocation are considered.>