Depression not only afflicts hundreds of millions of people but also contributes to a global disability and healthcare burden. The primary method of diagnosing depression relies on the judgment of medical professionals in clinical interviews with patients, which is subjective and time-consuming. Recent studies have demonstrated that text, audio, facial attributes, heart rate, and eye movement could be utilized for depression-level stratification. In this paper, we construct a virtual assistant for automatic depression-level stratification on mobile devices that can actively guide users through voice dialogue and change conversation content using emotion perception. During the conversation, features from text, audio, facial attributes, heart rate, and eye movement are extracted for multi-modal depression-level stratification. We utilize a feature-level fusion framework to integrate five modalities and the deep neural network to classify the varying levels of depression, which include healthy, mild, moderate, or severe depression, as well as bipolar disorder (formerly called manic depression). With outcome data from 168 subjects, experimental results reveal that the total accuracy of feature-level fusion with five modal features achieves the highest accuracy of 90.26 percent.

Cyber Threat Intelligence (CTI) reports provide valuable insights into cybersecurity attack techniques, which are essential for understanding threat execution. Identifying the root causes of these techniques is crucial for developing effective defense mechanisms. However, the unstructured nature and inconsistent terminology of CTI reports pose significant challenges in extracting causal factors, such as Common Weakness Enumerations (CWEs) and vulnerable data components, limiting proactive responses and the understanding of attack interdependencies. To address these challenges, we propose TRACE, a novel framework that extracts causal factors linked to adversarial techniques and generates comprehensive causal graphs revealing interdependencies within CTI reports. TRACE combines pattern extraction and tagging methods to address the limitations of existing approaches. Utilizing Sentence-based Bidirectional Encoder Representations from Transformers (SBERT) embeddings enhanced with knowledge mappings and deep learning techniques, TRACE discovers and models causal relationships between attack techniques within the reports. By bridging the gap between attack techniques and their underlying vulnerabilities, TRACE provides actionable insights to enhance cybersecurity defenses. Evaluated on 710 CTI reports, TRACE achieved an F1 score of 0.87, demonstrating its accuracy in extracting causal factors and its potential to advance automated causal analysis in cybersecurity.

Baduanjin is a type of martial art that is aimed at the development and health of the physical, emotional and spiritual aspects. It emphasizes on gentle movements, relaxed yet disciplined, and training of mental concentration through relaxation. In order to make Baduanjin attention training more effective and easier, we proposed a novel Baduanjin-based attention training game that instructs the subject to practice Baduanjin using virtual reality (VR) and motion analysis. Through a virtual instructor who demonstrates a series of Baduanjin actions, the subject is asked to follow the instructor's movement at any time. Meanwhile, the 3D position of the subject's body joints is collected by a motion capture device for further analysis using a deep learning model to evaluate the order correctness and precision of the Baduanjin actions. In addition, transfer learning technique is used to solve the problem of small size of Baduanjin data. Preliminary tests with 20 normal individuals showed that the recognition accuracy of the Baduanjin actions reached nearly 97%, and the balance analysis reflected the position change of the body center of mass to a certain extent. We also compared the performance of the model with and without pre-training to demonstrate the importance of transfer learning. The result of these explorations shows the feasibility of this prototype system as an attention training system and its potential as an assistive treatment option. In conclusion, we not only created the virtual instructor that could provide accurate movement demonstration, but also collected objective action data for more accurate balance analysis to provide appropriate feedback.

Drug abuse has always been a severe issue, but the proportion of drug abuse and addiction is rising. According to research reports, youth are motivated to access drugs mainly due to curiosity and peer influence. Additionally, youth especially lack proper knowledge and education surrounding drug abuse. Analyzing whether potential addicts intend to access drugs is helpful in preventing drug abuse and addiction. We developed an Anti-drug Chatbot for young people on a popular online social platform. We can detect potential risks, obtain warnings from the user-entered query and provide these to professional consultants for help. In this article, we present a hierarchical system with bidirectional encoder representation from transformers (BERT) to efficiently recognize and classify a user’s intent. We use the Chinese BERT-based model to utilize contextual information to perform classification and recognition. We evaluate our proposed system on our conversational dataset.

Cyber Threat Intelligence (CTI) plays a crucial role in understanding and preemptively defending against emerging threats. Typically disseminated through unstructured reports, CTI encompasses detailed insights into threat actors, their actions, and attack patterns. The MITRE ATT&CK framework offers a comprehensive catalog of adversary tactics, techniques, and procedures (TTPs), serving as a valuable resource for deciphering attacker behavior and enhancing defensive measures. Addressing the challenge of time-consuming manual analysis of MITRE TTPs in unstructured CTI reports, this paper presents MITREtrieval, a novel system that leverages deep learning and ontology to efficiently extract MITRE techniques. This approach mitigates issues related to the implicit nature of TTPs, textual semantic dependencies, and the scarcity of adequately labeled datasets, enabling more effective analysis even with limited sample sizes. Our approach combines a sophisticated sentence-level BERT deep learning model with ontology knowledge to address sparse data challenges, using a voting algorithm to merge outcomes. This results in a more accurate classification of MITRE techniques, capturing contextual nuances effectively. Our evaluation confirms MITREtrieval’s effectiveness in identifying techniques, regardless of their representation in training samples. MITREtrieval has surpassed benchmarks, achieving F2 scores of 58%, 62%, and 69% in multi-label technique identification across 113, 46, and 23 CTI reports, respectively, thereby streamlining CTI analysis and improving threat intelligence.

Methamphetamine use disorder (MUD) is a brain disease that leads to altered regional neuronal activity. Virtual reality (VR) is used to induce the drug cue reactivity. Previous studies reported significant frequency-specific neuronal abnormalities in patients with MUD during VR induction of drug craving. However, whether those patients exhibit neuronal abnormalities after VR induction that could serve as the treatment target remains unclear. Here, we used an integrated VR system for inducing drug related changes and investigated the neuronal abnormalities after VR exposure in patients. Fifteen patients with MUD and ten healthy subjects were recruited and exposed to drug-related VR environments. Resting-state EEG were recorded for 5 minutes twice-before and after VR and transformed to obtain the frequency-specific data. Three self-reported scales for measurement of the anxiety levels and impulsivity of participants were obtained after VR task. Statistical tests and machine learning methods were employed to reveal the differences between patients and healthy subjects. The result showed that patients with MUD and healthy subjects significantly differed in Θ, α, and γ power changes after VR. These neuronal abnormalities in patients were associated with the self-reported behavioral scales, indicating impaired impulse control. Our findings of resting-state EEG abnormalities in patients with MUD after VR exposure have the translational value and can be used to develop the treatment strategies for methamphetamine use disorder.

The creation of context-aware services in pervasive computing environments has driven the wide development of wireless local area network (WLAN)-based indoor positioning systems. One of the main challenges in WLAN-based indoor positioning is the severe fluctuation of received signal strength (RSS), which may cause the RSS patterns to be mismatched and the positioning to be inaccurate. In this paper, an indoor positioning algorithm that combines the fingerprint scheme with mobility prediction is proposed. Since the mobility prediction is performed according to the moving speed and direction of the mobile client, the resulting location estimation is more stable compared to the use of RSS alone. Experimental results show that the proposed positioning algorithm can mitigate the impact of the RSS fluctuation and has better positioning accuracy and stability than previous fingerprint-based approaches.

Network coding is a promising technology proven to improve the performance of wireless networks. To successfully design a quality-of-service (QoS)-satisfied routing protocol with network coding, the bandwidth consumption of a coding host should be determined. Furthermore, coding opportunities should be increased to improve network capacity. Nevertheless, it is challenging to determine whether a host can be a coding host and to determine the bandwidth consumption of a coding host in a mobile ad hoc network (MANET). In this paper, we first present and define the coding conditions to identify a coding host. The bandwidth consumption of a coding host is then estimated under the contention-based wireless networks with a random access mechanism. Finally, we propose a bandwidth-satisfied and coding-aware multicast routing protocol (BCMRP). By taking into account the residual bandwidth of the carrier-sense neighbors of the forwarders, the proposed protocol can satisfy the bandwidth requirements of the requested flow and other ongoing flows. As a consequence of considering coding opportunities in multicast tree construction, the proposed multicast protocol can reduce the total bandwidth consumption. The simulation results show that BCMRP outperforms the prior multicast routing protocols in receiving ratio, admission ratio, and total bandwidth consumption.

Network function virtualization (NFV), with its virtualization technologies, brings cloud computing to networking. Virtualized network functions (VNFs) are chained together to provide the required functionality at runtime on demand. It has a direct impact on power consumption depending on where and how these VNFs are placed and chained to accomplish certain demands as the power consumption of a physical machine (PM) depends on its traffic load. One of the advantages of VNF placement over traditional virtual machine placement is that virtualization is not limited solely to servers. The PMs, including the servers and varying loads to these machines and their utilization, are critical issues related to the network's energy consumption. In this paper, we designed a dynamic energy-saving model with NFV technology using an M/M/c queuing network with the minimum capacity policy where a certain amount of load is required to start the machine, which increases the utilization of the machine and avoids frequent changes of the machines' states. We formulate an energy-cost optimization problem with capacity and delay as constraints. We propose a dynamic placement of VNF chains (DPVC) heuristic solution to the NP-hard problem. The results show that the DPVC solution performs better and saves more energy. It uses 45%-55% less active nodes to satisfy the requested demands and increases the utilization of the active nodes by 40%-50% compared to other algorithms.

Summary With the rapid development of technology, digital multimedia has been widely utilized. Access of multimedia contents has become a daily routine. Although multimedia brings ease and convenience for content sharing, it also makes piracy more feasible. For example, it is easy to upload a copyrighted video to YouTube without the owners' permission. Authors and merchants are very much in need of protecting their intellectual property and commercial profits. Digital right management (DRM) systems are provided to fulfill this desire. DRM is a collection of techniques used to control access to copyrighted materials. Because current enterprise DRM solutions are not allowed for customized modification, they cannot fit in our considered scenario perfectly. As a result, we propose a secure DRM system with a design based on user demands, where a consumer can access contents only on authenticated devices until the authorization expires. Our DRM scheme involves a series of robust cryptosystems including AES, SHA‐256, and RSA. Applications as DRM agents are implemented on Windows, Mac OS, Android, and iOS platforms. Moreover, we modularized the DRM components for easy extension and integration. For better performance on low‐end devices, parameters of encryption are introduced, namely, the key size and the encryption density. We addressed the mask shift problem caused by random access and implemented the device identifier acquirement. The DRM system also proved to have high security and good performance in our analysis. Copyright © 2017 John Wiley & Sons, Ltd.

Due to the large installed base of distributed legacy networks, software defined networking (SDN) nodes may be required to coexist with legacy nodes to form hybrid networks. It has been shown that such a hybrid network has better performance than a pure legacy network due to smarter transmission scheduling. Despite such advantages, limited budgets continue to hinder the rapid adaptation of SDNs. Only a part of the network can be upgraded at a time especially for large-scale networks. In this paper, we define the minimum percentage of SDN nodes in a path, and paths with at least one SDN node, as the hop coverage and path coverage, respectively. We intend to evaluate the relationship between cost and coverage in the partially deployed SDNs. We formulate SDN node selection as four optimization problems with hop/path coverage and cost as objectives and constraints, respectively, and vice-versa. We propose two heuristic solutions: 1) maximum number of uncovered path first (MUcPF) and 2) maximum number of minimum hop covered path first (MMHcPF), to these NP-hard problems. Through a MATLAB experiment, we show that MUcPF is significantly better in terms of economy and efficiency to establish a hybrid path between every pair of hosts in the network. In particular, it required 5%-15% less investment to achieve 100% path coverage compared to other algorithms. The results show the coverage consistency of MMHcPF on each individual path along with gains in terms of cost and efficiency. It takes 5%-20% less investment to achieve certain hop coverage target compared to other existing algorithms.

In recent years, wireless network structures and mechanisms have been proposed to enhance the efficiency of communications. Regarding the upper-layer of protocol stacks, wireless transmission control protocols (WTCPs) are proposed to deal with transmission control protocol (TCP) performance problems on wireless networks. However, some new lower-layer solutions, e.g., cognitive radio (CR) systems, cause new throughput decay problems to TCPs, which existing WTCPs do not solve. In this paper, we study throughput decay issues in CR environments and discuss three events that cause these problems. Three event handlers are proposed to improve TCP throughput. The proposed solutions are designed by numerical analysis, and performance improvement is verified by NS2. We propose an event-driven CR-TCP that combines these event handlers, which can be combined with state-of-art CR-TCP solutions. Simulation results and analysis are presented to demonstrate the effectiveness of the proposed solution.

Vehicular ad hoc networks (VANETs) provide the communication framework for the dissemination of safety-critical messages such as beacons and emergency messages. The communication channel witnesses significant network load generated by frequently exchanged beacons. Under high-density situations, it leads to a serious scalability problem in VANETs. Moreover, contention-based medium access control (MAC) protocols suffer from a great number of packet collisions, and as a result, the reliability and latency of safety messages are severely affected. Because of the periodic nature of beacons, time-division multiple access (TDMA) can be a good choice over contention-based MAC. In this paper, we propose congestion-controlled-coordinator-based MAC (CCC-MAC), which is a time-slot-based medium access protocol that addresses beacons and emergency messages. Basically, the network is virtually partitioned into a number of segments. Within a segment, medium access is accomplished by using a time-slot-scheduling mechanism supervised by a local coordinator vehicle. A significant number of vehicles can be supported under the proposed configuration. In fact, the proposed scheduling mitigates channel congestion by reducing the transmission time of beacons through the use of multiple data rates. Bandwidth utilization is also improved by reusing the unoccupied time slots. Finally, CCC-MAC ensures fast and reliable propagation of emergency messages by employing a pulse-based reservation mechanism. In the simulations, we demonstrate the ability of CCC-MAC to scale well in different vehicular density scenarios. Moreover, it outperforms existing MAC-layer protocols with respect to packet reception probability and latency of safety messages.

Using advanced wireless local area network technologies, vehicular ad hoc networks (VANETs) have become viable and valuable for their wide variety of novel applications, such as road safety, multimedia content sharing, commerce on wheels, etc. Multihop information dissemination in VANETs is constrained by the high mobility of vehicles and the frequent disconnections. Currently, geographic routing protocols are widely adopted for VANETs as they do not require route construction and route maintenance phases. Again, with connectivity awareness, they perform well in terms of reliable delivery. To obtain destination position, some protocols use flooding, which can be detrimental in city environments. Further, in the case of sparse and void regions, frequent use of the recovery strategy elevates hop count. Some geographic routing protocols adopt the minimum weighted algorithm based on distance or connectivity to select intermediate intersections. However, the shortest path or the path with higher connectivity may include numerous intermediate intersections. As a result, these protocols yield routing paths with higher hop count. In this paper, we propose a hop greedy routing scheme that yields a routing path with the minimum number of intermediate intersection nodes while taking connectivity into consideration. Moreover, we introduce back-bone nodes that play a key role in providing connectivity status around an intersection. Apart from this, by tracking the movement of source as well as destination, the back-bone nodes enable a packet to be forwarded in the changed direction. Simulation results signify the benefits of the proposed routing strategy in terms of high packet delivery ratio and shorter end-to-end delay.

The fingerprint-based techniques are commonly used for indoor location estimation, in which a radio map is built by calibrating signal-strength values at several training locations in the offline phase. However, the signal-strength values change as the environment changes, and hence the radio map built may be out of date. Further, the recalibration of signal-strength values for each environment change is laborious and time consuming. Therefore, in this paper, an efficient radio map management method is proposed in response to the environment changes. We first demonstrate that different features of signal propagation are obtained in different regions of the indoor environment. According to the different features of signal propagation, the environment is divided into several regions and the signal-strength values collected at the training locations in different regions can be updated accurately and individually using proper propagation features. The experimental results show the usefulness of the proposed method and the accuracy of the localization can be improved.

In this paper, based on the concept of ceased areas, the spatial reuse in IEEE 802.11 ad hoc networks is enhanced by transmission power control (TPC). A ceased area is created by a transmitter-receiver pair where all other nodes should cease their transmissions for a while. The size of a ceased area varies with the transmission power. A new TPC scheme that can minimize the induced ceased area is proposed. It is practical without needs to know the transmitter-receiver distance. And its performance in network throughput is superior to previous TPC schemes.

Vehicular ad hoc networks (VANETs) have recently been considered as an attractive network architecture to provide various services ranging from road safety to entertainment applications. In this paper, we propose an IEEE-802.11-based multihop broadcast protocol to address the issue of emergency message dissemination in VANETs. The protocol adopts a binary-partition-based approach to repetitively divide the area inside the transmission range to obtain the furthest possible segment. The forwarding duty is then delegated to a vehicle chosen in that segment. Aside from accomplishing directional broadcast for highway scenario, the protocol also exhibits good adaptation to complex road structures. The main focus of the paper lies in reducing broadcast delay, which is an important factor for time-critical safety applications. Most importantly, the contention delay remains almost constant, irrespective of vehicle density. Mathematical analysis is performed to assess the effectiveness of the protocol. Simulation results demonstrate that the proposed protocol imparts greater performance in terms of latency and message progress when compared with contemporary multihop broadcast protocols for VANETs.

Since the multi-rate enhancements have been implemented in wireless ad hoc networks (MANETs), QoS-constrained multicast protocols for multimedia communication should be adapted to exploit them fully for using more efficiently the limited resources. To build a multicast tree with delay-guaranteed, one-hop delay and end-to-end delay must be known. The one-hop delay is the transmission time at a given link connecting two neighboring hosts, and the end-to-end delay is the time taken for a data packet from a specific source to reach the destination node. However, how to calculate the above two delays using the IEEE 802.11 MAC is still a challenging problem, because the radio channel is shared among neighbors. Further, the multi-rate enhancements make it more difficult since the neighboring relation among hosts is varied with the transmission rates. In this paper, we first propose a method to estimate the one-hop delay based on varied transmission rates by monitoring the sensed busy/idle ratio of shared channel. Then, by its aid, another method is proposed to compute the end-to-end delay. Finally, we integrate the above two methods with a typical multicast routing protocol, ODMRP, for constructing a delay-guaranteed multicast protocol. Simulation results show that the proposed method obtains more precise one-hop delay than a very recently work. Besides, the integrated protocol provides better delay guarantee than the existing protocol when the multicast traffic has delay requirement.

Vehicular Ad Hoc Network has recently been considered as attractive network architecture to provide various services ranging from road safety to entertainment applications. In this paper, we propose an IEEE 802.11 based multihop broadcast protocol to address the issue of safety message dissemination in Vehicular Ad Hoc Networks. This position- based protocol adopts a repetitive 2-partition method to divide the area inside transmission range resulting in a furthest narrow segment and delegates the forwarding duty to a vehicle chosen in the furthest segment. The main focus of the paper lies in reducing broadcast delay which is an important factor in time critical safety applications. We attempt to attain consistent performance irrespective of node density and different VANET scenarios. In addition to this, the protocol also solves the hidden terminal problem of multihop broadcasting. Simulation results show that our protocol achieves greater performance in terms of latency and message progress when compared with other well known multihop broadcast protocols for Vehicular Ad Hoc Networks.

Event detection and environment surveillance are the important issues in wireless sensor networks. However,using the non-renewable power source leads to the short lifetime of the networks. For this reason the scheduling process is to determine the time sensor node wakes up and goes sleeping to conserve energy, so the delay time and the working interval would become trade-off. In this article, we introduce the two ranked aware phase surveillance to lower the delay time, and we use the sensed data to make the scheduling policy.We consider the event happening in two phase, so we propose two surveillance models to cope with these two phases,although this model is simple to create it can achieve the goal of reducing the delay time of detection and delivery. Finally, we show our performance in the simulation section and then describe the improvement of our approach in the future work section.

Recently, with the advantages of peer tutoring, robot for education usage has been the new trend for new generation leaning technology. Robot is not only a toy, but also your learning partner. We considered integrating speech, position information and 3G cell phone to realize a highly-interactive learning platform.Teachers can design different scene with many stages for English or mathematic. Students send out his command to the robot with motions or speech the robot travels within the scene as an adventure. And the students assist the robot to solve any quizzes it meets If the adventure processes successfully, the robot will interact happily with student otherwise, it will encourage the student to keep trying. The parents or the teacher can observe all these activities with a 3G cell phone to give advises of learning at any time.

Routing in vehicular network is a major challenge and research area. The major threat is the node density and high dynamics of the network topology. Existing position based routing protocols try to solve this by forwarding data in greedy forwarding way. However, they solely depend upon Location services. Location service makes a lot of transactions in the network traffic. Proactive routing protocols find the destination information by flooding RREQ messages. But flooding also increases routing overhead. Again they maintain a route from source to destination. The lifetime of route is same as the life time of the edge with smallest life time. This makes it vulnerable to path break up, which leads to frequent RREQ flooding. We have tried to solve the above stated problems in three manners: (1) Location service overhead problem: We have not used any location server; rather a destination discovery message is sent from source to destination which finds the destination direction relative to source. If the destination direction is known this is not used. (2) Flooding of RREQ problem: We have not used any flooding. We have used only unicast messages. (3) Path break-up problem: We have not used any dedicated path from source to destination for data transmission. Rather we have selected the next hop in the direction of destination to send a packet using an algorithm called smart next hop selection algorithm (SNESA). Also we have tried to reduce the frequency of HELLO messages using neighbor update algorithm which validates the neighborhood of a node.

In last decades, the demand of wireless spectrum has increased rapidly with the development of mobile communication services. Recent studies recognize that traditional fixed spectrum assignment does not use spectrum efficiently. Such a wasting phenomenon could be amended after the present of cognitive radio. Cognitive radio is a new type of technology that enables secondary usage to unlicensed user. This paper presents an opportunistic cognitive MAC protocol (OC-MAC) for cognitive radios to access unoccupied resource opportunistically and coexist with wireless local area network (WLAN). By a primary traffic predication model and transmission etiquette, OC-MAC avoids producing fatal damage to licensed users. Then a ns2 simulation model is developed to evaluate its performance in scenarios with coexisting WLAN and cognitive network.

The intelligent transportation system (ITS), a worldwide initiative program utilizes novel information and communication technology for transport infrastructure and vehicles. Among extensive ITS components, efficient communication system is the most important role which connects numerous vehicles with roadside infrastructure and management center in the ITS program. Vehicular ad hoc network (VANET) has been a cornerstone of the envisioned ITS without infrastructure. However, multihop data delivery through VANET is difficult by the fact that vehicular networks are highly mobile and frequently disconnected. Thus, traditional ad hoc routing protocols are not well suited for these high dynamic network. In this paper we propose a new heterogeneous vehicular network (HVN) architecture and a mobility pattern aware routing for HVN. HVN integrates wireless metropolitan area network (WMAN) with VANET technology and reserves advantages of better coverage in WMAN and high data rate in VANET. Vehicles in HVN can communicate with each other and access Internet ubiquitously. We mainly focus on the routing issue for HVN, because the routing protocol for HVN is different from those used in MANET or VANET. With the WMAN infrastructure support in HVN, the mobility pattern aware routing protocol can adopt the whole information of the vehicular network and unique characteristics of vehicle mobility to establish a reliable route path in high dynamic vehicular network.

Previous quality-of-service (QoS) routing/multicasting protocols in mobile ad hoc networks determined bandwidth-satisfied routes for QoS applications. However, they suffer from two bandwidth-violation problems, namely, the hidden route problem (HRP) and the hidden multicast route problem (HMRP). HRP may arise when a new flow is permitted and only the bandwidth consumption of the hosts in the neighborhood of the route is computed. Similarly, HMRP may arise when multiple flows are permitted concurrently. Not considering the bandwidth consumption of two-hop neighbors is the reason that the two problems are introduced. In this paper, a novel algorithm that can avoid the two problems is proposed to construct bandwidth-satisfied multicast trees for QoS applications. Furthermore, it also aims at minimizing the number of forwarders so as to reduce bandwidth and power consumption. Simulation results show that the proposed algorithm can improve the network throughput.

This paper presents an online measurement-based admission control scheme on the basis that the aggregate VBR video traffic is lognormally distributed. The proposed scheme consists of two components: measurement process and admission decision. The measurement process applies a linear Kalman filter to estimate statistical parameters of aggregate VBR video traffic. The estimated statistical parameters are used to calculate the effective bandwidth for admission decision. Variable bit rate (VBR) video traffic with high data rate is expected to occupy a dominant proportion of bandwidth for future wireless broadband home networks. To guarantee quality-of-service (QoS) of such VBR video streams, while achieving a high level of channel utilization, an efficient admission control scheme is urgently required, especially for emerging wireless multimedia indoor services, such as HDTV, online video game, etc. The proposed scheme is computationally efficient and accurate without much prior traffic information. Simulation results verify its effectiveness and show that it performs well for both a small number of connections and a large number of connections.

The bandwidth-constrained routing problem (BCRP) asks for a route that has sufficient bandwidth for data transmission. When BCRP is defined for wired networks, it can be solved in polynomial time. On the other hand, when it is defined for wireless ad hoc networks, it is NP-complete if the underlying MAC protocol is TDMA-based or CDMA-over-TDMA-based. In this paper, we show that BCRP is still NP-complete, even if CSMA-based or contention-based CDMA MAC prot.ocols are used. Besides, we show that BCRP is polynomial-time solvable if the channel model is collision-free and the scheduling policy is FIFO. In wireless ad hoc networks, no MAC protocol was designed before, which would lead to a polynomial-time solution to BCRP. The results of this paper suggest a design for MAC protocols that can support QoS routing well.

In this paper, we design a novel transmission structure called a double-tree for correlated data gathering problem for wireless sensor networks, where the goal is to minimize the total transmission cost of information collected by all sensor nodes, to the sink node. It is well-known that a tree structure is often adopted for network routing problems. However, the traditional tree transmission structure for network routing may not be an optimal structure while data correlation factors are being considered. For a given wireless sensor network, some nodes send their raw data directly to the sink, and some nodes send their encoded data based on information received from other nodes; therefore, there are two types of data in the network. Without the help of decoding/re-coding at the intermediate node, the purpose of encoded data routing is to directly send to the sink, but the purpose of raw data routing is not only to send to the sink, but also to spread raw data to other nodes as side information in encoding operations. The difference from one data type makes traditional tree structure unsuitable for the correlated data gathering problem. Therefore according to our observations, we propose a new transmission double-tree structure, which uses one tree for raw data routing, and uses another tree for encoded data routing. By employing the double-tree structure, the network can achieve lower transmission cost of gathering sensing data. Furthermore the adoption of double-tree structure always outperforms the traditional tree structure in correlated data gathering problem. We first formulate the optimization problem with a double-tree transmission structure in the general case, and prove NP-Hardness of simplified version of this problem. Then we present a 2-approximation algorithm MST+SPT that guarantees the upper bound of total transmission cost compared to the optimal solution.

Measurement of end-to-end available bandwidth has received considerable attention due to its potential use in improving QoS. Available bandwidth enables the sending rate to adapt to network conditions, so that packet loss, caused by congestion, can be significantly reduced before error control mechanisms are finally employed. To this end, we propose a probing noise resilient available bandwidth estimation scheme, called JitterPath, which is adaptive to both the fluid and bursty traffic models. Two key factors, one-way delay jitter and accumulated queuing delay, are both exploited to predict the type of queuing region for each packet pair. Then, the bottleneck utilization information included in the joint queuing regions is estimated and used to quantify the captured traffic ratio, which indicates the relationship between the probing rate and available bandwidth. The contributions of our method are as follows: 1) JitterPath can work without being restricted to fluid traffic models; 2) since JitterPath does not directly use the bottleneck link capacity to calculate the available bandwidth, it is feasible for use in a multihop environment with a single bottleneck; and 3) JitterPath inherently reduces the impact of probing noises under the bursty cross traffic model. Extensive simulations, Internet experiments, and comparisons with other methods were conducted to verify the effectiveness of our method under both single-hop and multihop environments

IEEE 802.15.3, an emerging wireless technology, was designed to provide high-quality multimedia services at home. Dynamic bandwidth allocation for a multimedia connection should be considered in order to achieve higher channel utilization, less buffer and less delay, especially for variable bit rate (VBR) multimedia connections. For real-time VBR videos, the bandwidth requirement should be predicted adaptively for effective channel-time requests. Previously, the adaptive least-mean square (LMS) algorithm with fixed step size was applied to predict channel time requirements due to its simplicity and relatively good performance. However, the performance might degrade when scene changes occurred. In this paper, we modify the variable step-size LMS algorithm and apply it as our predictor (VSSNLMS) so that the prediction errors on scene changes can be effectively reduced. Using the prediction results of VSSNLMS, we propose a dynamic bandwidth-allocation scheme that is scene-change aware and can guarantee the delay bound of real-time VBR videos. Simulation results show that the VSSNLMS predictor is superior to previous LMS-type predictors in performance, and the proposed scheme has better performance in channel utilization, buffer usage, and packet loss

Although quality of display devices is good right now, most textbooks are still printed on papers. At the same time, most learning support and e-learning courseware are built with the assumption that the student only read information displayed on the screen. In this paper, we present an environment that provides learning support via computers, digital devices and network when a student studies a course by reading paper textbooks with a digital pen. The learning support is organized based on the knowledge unit of the location positioning by the digital pen in the textbook. The support includes term explanation, related discussions, underline, and annotation. These studying actions and results on papers will be stored in the computer as well for later use. Initial experiment result on using the system shows that students feel beneficial to their study.

The Bandwidth-Constrained Routing Problem (BCRP) asks for a route that has sufficient bandwidth for data transmission. When BCRP is defined for wired networks, it can be solved in polynomial time. On the other hand, when it is defined for multi-hop wireless networks, it is NP-complete if the underlying MAC protocol is TDMA-based or CDMA-over-TDMA-based. In this paper, we show that BCRP is still NP-complete, even if CSMA-based or contention-based CDMA MAC protocols are used. Besides, we show that BCRP is polynomial-time solvable if the underlying MAC protocol adopts CDMA channel model and FIFO scheduling policy. In multi-hop wireless networks, no MAC protocol was designed before which would lead to a polynomial-time solution to BCRP. The results of this paper suggest a design principle for MAC protocols that can support QoS routing well.

Recently, ultra-wideband (UWB) technologies have attracted considerable attention for its capability, high data rate to achieve 480 Mbps, to wireless personal communications. In this paper, the problem of TCP and energy efficient transmission in IEEE 802.15.3 WPAN based on UWB technologies are addressed. Also, a simple power-efficient scheme for TCP transmission in accordance with IEEE 802.15.3 WPAN standard is proposed and NS2 is used for evaluating the performance of this proposal. The scheme design is driven by two major factors. The first one is that the scheme should provide high TCP throughput in a piconet and low end-to-end delay for TCP packets. The second one is that the scheme should be energy efficient since most mobile devices typically are powered by battery and have limited power capacity. In order to meet these requirements, the energy efficient design at the MAC layer and transport layer is taken into account by the proposed schema

With the wireless technology development, more and more standards are declared for certain purpose and many of them have to share the same radio frequency spectrum. On the other hand,because many requests from unstable traffic use the peak rate and some behavior of bursted traffic, the utilization of the channel might be low in most of the time. Therefore, the radio frequency spectra are treasurable and issues about increasing or balancing spectrum utilization become more important. CR (cognitive radio) technique is now developing for solving this critical problem. CR technique includes many aspects of researches, such as reusing spectrum holes invisibly, learning form users' behavior, adjusting changes form the environment automatically, and so on. This paper gives out a cognitive borrowing algorithm which can ensure the QoS of primary users. By using this algorithm with environment scanning capability, CR traffics raise the utilization of the channel with only rare damage to prior users. Moreover, the algorithm has the advantages of decentralized system, flexibility, low computing complexity, and fairness

We propose a one-way delay jitter based scheme, "jitterpath," for available bandwidth estimation. Common assumptions, including use of the fluid traffic model and use of the bottleneck link capacity, that have been made in the literature are relaxed in this study. We exploit one-way delay jitter and accumulated queuing delay to predict the type of a queuing region for each packet pair. In addition, we quantify the captured traffic ratio, which is defined as the total output gaps of joint queuing regions per total input gaps, and use it to derive the relationship between probing rate and available bandwidth. We further investigate how the estimation resolution and the probing noise ratio are related to the accuracy of available bandwidth estimation. Extensive simulations and real-network experiment have been conducted and comparisons with other methods have been made to verify the effectiveness of our method, no matter whether single-hop or multi-hop environments are considered

In this paper, we propose U-MAC, a medium access control protocol designed for wireless sensor networks. Nowadays, wireless sensor network are formed by a great quantity of sensor nodes, which are generally battery-powered and may not recharge easily. Consequently, how to prolong the lifetime of the nodes is an important issue while designing a MAC protocol. However, lowering the energy consumption may result in higher latency. Addressing on such tradeoff, U-MAC balances the tradeoff by utilization based tuning of duty cycle and selective sleeping after transmission. The experiment results show that our proposed U-MAC saves energy about 43% and reduce latency by 65% from S-MAC in a chain topology. In the cross topology, U-MAC also achieves 32% energy saving and 45% latency reduction from S-MAC.

The mobile IPv6 handover process consists of three major stages: movement detection, duplicate address detection and binding signaling. Most of the research efforts for optimizing the handover process focuses on minimizing the delays caused by the first two stages. The delay introduced by binding signaling is largely ignored since the correspondent node is assumed to be stationary. However, this delay can be significant when two communicating nodes are both mobile and may roam across different networks simultaneously. mobile IPv6 requires that the binding signaling exchanged between the mobile node and the correspondent node to be authenticated using a procedure called return mutability test. The signaling involved in the return routability procedure is mandated to be redirected through the home agents to the most up-to-date addresses of the communicating nodes. This may result in a longer handover duration if the mobile and correspondent nodes are both far from their home agent, In this paper, we present our recommendation on the use of direct signaling without the need to have any redirection from a network element. We also present an analysis of the cost involved in utilizing direct and indirect signaling mechanisms.

In the existing mobile ad hoc network (MANET) QoS routing and multicasting protocols, the methods of bandwidth calculation and allocation were proposed to determine routes with bandwidth guaranteed for QoS applications. As our observations, two bandwidth-violation problems is incurred in the above protocols. First: When a new bandwidth-requirement flow starts, the existing methods determine a bandwidth-satisfied route and reserve the bandwidth for the flow accordingly by considering the nodes' status on the route and network configuration. However, the reservation might violate the bandwidth capacities of other ongoing bandwidth-consuming flows. Second: Another bandwidth-violation problem would mislead the bandwidth reservation for QoS multicast applications when the multiple routes from a server to all clients were determined concurrently. Our simulation results exhibit that the two problems have high possibilities to be incurred so as to cause serious performance declination while the network traffic is heavy. In this paper, the problem of determining a bandwidth-satisfied tree is formulated as a 0/1 integer linear programming (ILP) for the theoretical studies. We minimize the number of forwarders for reducing the number of hosts participating in packet forwarding so as to lower bandwidth and power consumption that are crucial to MANET performance.

Abstract Accompanied by the widespread deployment of wireless networks, content and service providers are increasingly interested in supporting multicast communications over wireless network. The reliable multicast protocol can provide (assure) efficiency in data delivery carried by the new generation e‐services, such as news, advertisement, guiding messages, etc. Its congestion control function enables the transmissions to adapt the sending rate to the available bandwidth and fairly share bandwidth with the widely used transmission control protocol (TCP) traffic in the networks. Many e‐services can be brought and built on the reliable multicast congestion control protocols to the roaming mobile subscribers. However, the reliable multicast congestion control protocols are affected by the wireless packet losses, resulting in degraded multicast performance. This article presents PGMCCW, a pragmatic general multicast congestion control protocol for wireless networks. PGMCCW can differentiate the wireless losses as well as the congestion losses on multicast and can also elect the proper group representative from the multiple receivers in the different wireless sub‐networks. The simulation results validate that this scheme is effective to alleviate the influence of the wireless losses and improve the performance over wireless networks. Copyright © 2005 John Wiley & Sons, Ltd.

Broadcast/multicast is a key service for mobile ad hoc networks. A great number of applications rely on a reliable and efficient MAC layer broadcast. The IEEE 802.11 broadcast protocol, which is based on carrier sense multiple access with collision avoidance (CSMA/CA), does not offer any MAC layer recovery on broadcast frames. Consequently, the increasing probability of lost frames may deteriorate the quality of broadcast/multicast services offered at upper layers. In this paper, we first formulate the broadcast problem as an optimization problem and show that it is NP-hard, even if the upper layer service is periodical beacons. An approximation algorithm with a guaranteed approximation ratio is also suggested. Then, a reliable and efficient MAC layer broadcast protocol, named broadcast protocol with busy tone (BPBT), is proposed. BPBT applies a busy tone to solve the hidden terminal problem. Finally, BPBT is compared with previous protocols for performance evaluation by simulation.

Video transmission needs a stable sending rate in order that the video can be displayed showing uniform quality. In addition, a lower packet loss rate is rather helpful in reducing video quality degradation. Therefore, reliable available bandwidth estimation becomes an indispensable step towards robust transmission of multimedia data. The existing available bandwidth estimation methods cannot deal with the false estimation problem and thereby precise estimation is impossible. In this paper, we propose a reliable available bandwidth estimation method, based on distinguishing queuing regions and resolving false estimations. Promising simulation results indicate that our method can obtain the available bandwidth precisely, no matter what the network environment is; single-bottleneck or multiple-bottleneck.

The IEEE 802.11 working group has been developing a new distributed MAC, called the enhanced distributed function (EDCF), to support service differentiation in the IEEE 802.11 MAC protocol. Besides, highspeed WLAN environments are also expected to provide wireless Internet services in hot spots such as airports, parks, etc. Since there are usually multiple service providers competing for providing wireless network access in hot spots, mobile users are free to choose their own service providers. In this paper, we analyze the resource management problem in the competitive environment, in which the EDCF protocol is implemented in all access points (APs) and mobile stations. We formulate admission control as a game and prove the game owns a Nash equilibrium solution. Based on the game, a service provider not only fulfills, for the most part, the QoS satisfaction of ongoing flows but also increases its own revenue. We evaluate the performance by means of throughput, packet delay and bandwidth violation ratio.

Adequate bandwidth allocations and strict delay requirements are critical for real time applications. Packet scheduling algorithms like class based queue (CBQ), nested deficit round robin (nested-DRR) are designed to ensure the bandwidth reservation function. However, they might cause unsteady packet latencies and introduce extra application handling overhead, such as allocating a large buffer for playing the media stream. High and unstable latency of packets might jeopardize the corresponding quality of service since real-time applications prefer low playback latency. Existing scheduling algorithms which keep latency of packets stable require knowing the details of individual flows. GPS (general processor sharing)-like algorithms does not consider the real behavior of a stream. A real stream is not perfectly smooth after forwarding by the routers. GPS-like algorithms introduces extra delay on the stream which is not perfectly smooth. This thesis presents an algorithm which provides low latency and efficient packet scheduling service for streaming applications called LLEPS.

In this paper, we introduce and analyze a new congestion control approach for multimedia streaming, called TMRC (Time-based Model TCP-Friendly Rate Control). TMRC is a time-based end-to-end congestion control mechanism, which uses a model to estimate sending rate and assures the fairness against competing flows. With our mechanism, the sender can explicitly adjust its sending rate as a function of the measured rate reported by the correspond receiver. In long term, TMRC acts as a TCP-friendly flow with the same throughput as other flows while in short term it performs more stable in its sending rate. This makes our mechanism suitable for real-time multimedia streaming. At last, we compare TMRC to other TCP-friendly rate control mechanism, such as TFRC.

TCP is a widely used transport protocol constructed from the wired links that performs well over the traditional network. Since the wireless network is growing rapidly particularly in the wired/wireless mixed inter-network, a heterogeneous environment is expected to be deployed in the next generation all-IP wireless networks. The TCP that detects the losses as congestion events could not suit the heterogeneous network in which the losses are introduced by the higher bit error rates or handoffs. There exist some unsolved challenges for applying TCP over the wireless links. End-to-end congestion control and fairness issues are two significant factors. To satisfy these two criteria, we propose a jitter-based scheme to adapt the sending rates by the packet losses and jitter ratios. The experiment results have shown that our jitter-based TCP (JTCP) has a good performance over the heterogeneous network.

The session initiation protocol (SIP) provides advanced signaling and control functionality for a wide variety of multimedia services. This paper introduces an extension of session initiation protocol (SIP) to support multipoint conference. via functions, a multipoint conference could be constructed by mobile hosts (user agents, UAs), It requires no server side or network structure modifications. Considering the network performance and end-to-end delay, we propose a new multipoint mobile multicast location management mechanism using SIP. In this mechanism, each data packet is sent out using multicast and routed in a shortest path between any two members of a conference. This paper also introduces the analytical model and performs simulation experiments using network simulator 2 (NS2). The experiment results demonstrate that this extension of SIP carries advantages in end-to-end packet delay and the processing time for a new participant to join a multipoint conference.

Transmission control protocol (TCP), a widely used transport protocol performs well over the traditional network which is constructed by purely wired links. As wireless access networks are growing rapidly, the wired/wireless mixed internetwork, a heterogeneous environment will get wide deployment in the next-generation ALL-IP wireless networks. TCP which detects the losses as congestion events could not suit the heterogeneous network in which the losses will be introduced by higher bit-error rates or handoffs. There exist some unsolved challenges for applying TCP over wireless links. End-to-end congestion control and fairness issues are two significant factors. To satisfy these two criteria, we propose a jitter-based scheme to adapt sending rates to the packet losses and jitter ratios. The experiment results show that our jitter-based TCP (JTCP) conducts good performance over the heterogeneous network.

This paper presents a novel 802.11-based positioning system called the maximal cluster centered positioning system (MCCPS) developed and demonstrated at National Central University. The MCCPS system locates mobile objects via collecting the sensed power strengths of the mobile objects to multiple wireless access points. To overcome the serious multipath fading problem in the indoor environment, several positions called reference points were selected and a database is introduced to maintenance the power signature of each reference point. The experimental results show that the location information provided by MCCPS assures high correctness of region classification and low distance error.

With the provisioning of high-speed wireless LAN (WLAN) environments, traffic classes (e.g., VoIP or video-conference) with different QoS requirements will be introduced in future WLANs. The IEEE 802.11e draft is currently standardizing a distributed access approach, called the enhanced distributed coordination function (EDCF), to support service differentiation in the MAC layer. However, since each mobile station transmits data packets egotistically in a distributed environment, the QoS requirement of each traffic class may not be guaranteed. In this paper, we develop an admission control strategy to guarantee the QoS requirement of each traffic class. In order to provide a criterion for admission decision, we introduce an analytical model for EDCF to evaluate the expected bandwidth and the expected packet delay of each traffic class. The admission control strategy uses the performance measures derived from the analytical model to decide if a new traffic stream is permitted into the system. We validate the accuracy of the analytical model by using the ns-2 simulator. Some performance evaluations are also demonstrated to illustrate the effect of the proposed admission control strategy.

For the multimedia streaming applications to apply RTP/RTCP, two significant factors are the performance of long periodic control with RTCP, and the friendliness to TCP on the rate adjustment. To satisfy these two criteria, this paper proposes a rate estimation scheme based on the packets loss ratio and jitter ratio sampling at the RTP/RTCP-like receiver and adopting the time-based TCP model. The time-based model is a rate equation of the variables of time, while the existing model, named packet-based, is another equation of the variables of packet counting. The meaning of rate estimation is that for one connection of a particular sending rate, the receiver can closely estimate the average transmission rate of other TCP flows in competition. The simulation results show that our rate estimation approach conducts good estimation, and can be the basis of rate adjustment and congestion control.

Recent routing protocols and multicast protocols in ad-hoc networks adopt two-tier architecture to accommodate the effectiveness of the flooding scheme and the efficiency of the tree-based scheme. Some hosts with maximum neighbor degree are chosen as RPs (rendezvous point) to forward data. However, these hosts will higher possibility to be the traffic concentration and bottleneck of the network, and RPs will spend more time forwarding data due to maximum neighbor degree. In this paper, we propose a multicast protocol for ad-hoc network, called OGHAM, with shorter relay and less concentration via selecting RPs from the hosts with minimum hop distance between them and from other normal hosts to these selected RPs rather than the hosts with maximum neighbor degree.

This article proposes a hybrid multiple access (HMA) transmission strategy that integrates the traditional multi-access mode and the novel uni-access mode for WCDMA downlink. For better multiplexing of services with different quality requirements, this paper also proposes a quality based admission control policy and a scheduling scheme to construct an overall system for evaluation. Furthermore, a throughput optimization extension considering both intra-cell and inter-cell interference for the HMA is presented. In the simulation study, it is shown that the HMA outperforms the CDMA system with better GOS, lower delay, lower BER and higher throughput where last three aspects of improvement are gained by uni-access transmission mode. We observe that the HMA provides more significant improvements when the system load is higher.

Abstract An ad hoc network is formed by a collection of mobile nodes without any centralized access point or existing infrastructure. Communications between mobile nodes require routing over multiple‐hop wireless paths. Since mobile nodes could be of high mobility, an effective and adaptive routing protocol must have ongoing details of the topology information. However, it wastes limited bandwidth to keep routing information up‐to‐date and reliable. Thus, one of the crucial design objectives to achieve routing responsiveness and updating efficiency is the minimization of reaction to mobility. Specifically, a scalable and QoS‐guaranteed routing protocol is desired for novel multimedia applications in mobile ad hoc networks. In this paper, we propose an efficiently repairable routing protocol, called Gravitational Cluster Routing (GCR) Protocol. It contains a stable cluster structure to cover dense areas and avoid articulation nodes. The reaction to mobility can be reduced significantly by unicast. Active routing paths can be maintained locally in each cluster. Besides, repairable levels of active routing paths, which rank their stabilities, are evaluated. By their aid, the proposed GCR can find routing paths that satisfy different parameters of QoS. These mechanisms can improve the stability of active connections. Copyright © 2003 John Wiley & Sons, Ltd.

Multimedia applications have been desirable and attract a rapidly increasing number of network subscribers. However, their generated enormous amount of Internet traffic usually congests the network to cause the degradation of network utilization. Although multicast provides an efficient way for distributing multimedia information to a set of destinations simultaneously, the congestion still degrades the desired QoS (quality of service) of the on-going multicast connections especially if the group of multicast destinations is large and scattered. Hence, this paper proposes a novel adaptive multicast routing (AMRST) approach for satellite-terrestrial network (ST network) to provide reliable and adaptive multicast services to global subscribers. This approach decomposes the multicast delivery problem into two parts, (1) the construction of the multicast tree and (2) the maintenance of dynamic membership. The virtual hierarchical routing tree (VHRT) is proposed for constructing an efficient multicast tree and the re-routing scheme is for maintaining the multicast tree in an optimal routing cost once the membership, such as member joining or leaving, changes dynamically. The AMRST not only keeps the benefits of the traditional terrestrial multicast but also further promotes the multicasting performance by employing the satellite broadcasting capability. The simulation results demonstrate that the AMRST has excellent performance for the satellite-terrestrial network.

In a mobile environment, a decision maker would usually like to query times, locations, and moving behaviors of certain mobile terminals. For example, a mobile transaction would like to know where is the next cell of its mobile clients and the probabilities that the mobile clients will move to the cells so that it could reserve appropriate channels for them. As a result, tracking the changing times and positions of mobile terminals capable of continuous movement is becoming increasingly necessary. However, current personal communication services (PCS) networks can only offer current maintained location information of non-idle mobile terminals. Pertinent researches predict location based on tangent velocity approaches. Location prediction based on tangent velocity is effective only within a short time interval. In this paper, we propose a model to model the moving behavior of each mobile terminal. From the moving behavior, we estimate and propose several location prediction functions for location query. The experimental results show that our proposed location prediction functions are accurate enough for regular moving mobile terminals.

An ad-hoc network is formed by a collection of mobile nodes without any centralized access point or existing infrastructure. Communication between mobile nodes requires routing over the multiple-hop wireless path. Since the mobile nodes could be of high mobility, the effective and adaptive routing protocol must have on-going detail of the topology information. However, it wastes limited bandwidth to keep routing information up-to-date and reliable. Thus, a crucial algorithm design objective to achieve routing responsiveness and updating efficiency is the minimization of reaction to mobility. This paper proposes an efficiently repairable routing protocol, called as gravitational cluster routing (GCR) protocol. It is based on a stable cluster structure that covers dense areas to increase stability, and avoids articulate nodes in the cluster to connect strongly and adopts unicast to minimize reaction to mobility. The active routing paths of GCR can be maintained locally by individual stable clusters and globally by quantifying the corresponding repairable levels to satisfy the distinct demand parameters of QoS. These mechanisms improve the stability of active connections.

Due to the insufficiency of available bandwidth resources and the continuously growing demand for cellular communication services, the channel assignment problem becomes increasingly important. To trace the optimal assignment, several heuristic strategies have been proposed. So far, most of them focus on the small-scale systems containing no more than 25 cells and they use an anachronistic cost model that does not satisfy the requirements of most existing cellular operators to measure the solution quality. Solving the small-scale channel assignment problems could not be applied into existing large scale cellular networks' practice. This article proposes a decomposition approach to solve the fixed channel assignment problem (FCAP) for large-scale cellular networks through partitioning the whole cellular network into several smaller sub-networks and then a sequential branch-and-bound algorithm is designed to solve the FCAP for them sequentially. The key issue of partition is to minimize the dependences of the sub-networks so that the proposed heuristics for solving smaller problems will suffer fewer constraints in searching better assignments. The experimental results show that the proposed algorithms perform well and we applied our algorithms in finding better assignments for the cellular network of the Taiwan Cellular Cooperation in ChungLi city.

Multicast provides an efficient way of distributing multimedia information to a set of destinations simultaneously with the highest possible data rate. To enhance the multicasting performance, an adaptive multicast routing (AMR) approach for the satellite-terrestrial network (a hybrid network interconnected by VSAT systems) is proposed. It can dynamically adjust the routing path to obtain a minimal routing cost through a re-routing operation and support dynamic membership, joining and leaving. The simulation results demonstrate that the AMR has better performance and lower routing costs than any other Internet multicast algorithm.

Due to the poverty of available bandwidth resources and increasing demand for cellular communication services, the problem of channel assignment becomes increasingly important. To trace optimal assignment, several algorithms have been proposed to minimize the amount of required channels. However, the total number of available frequencies are given and fixed in many situations. A new cost model is required for assigning channel in the cellular networks with limited bandwidth. We analyze the cost of each assignment in the view of damages from blocking calls and interfered by other frequencies. Furthermore, we formulate a new optimization problem for the fixed channel assignment problem by incorporating the limited bandwidth constraint into its cost model. To minimize the cost function, we adopt genetic approach to propose an evolutionary approach. Experimental results show that the cost function does reflect the quality of different assignments and also show that our algorithm does improve the solution quality significantly.

We propose a new location tracking strategy called behavior-based strategy (BBS) based on each mobile's moving behavior. With the help of data mining technologies the moving behavior of each mobile could be mined from long-term collection of the mobile's moving logs. From the moving behavior of each mobile, we first estimate the time-varying probability of the mobile and then the optimal paging area of each time region is derived. To reduce unnecessary computation, we consider the location tracking and computational cost and then derive a cost model. A heuristics is proposed to minimize the cost model through finding the appropriate moving period checkpoints of each mobile. The experimental results show our strategy outperforms fixed paging area strategy currently used in the GSM system and time-based strategy for highly regular moving mobiles.

In this paper, we propose an approach to support QoS and multimedia applications in ad hoc wireless networks. An ad hoc network is a collection of mobile stations forming a temporary network without the aid of any centralized coordinator and is different from cellular networks which require fixed base stations interconnected by a wired backbone. It is useful for some special situations, such as battlefield communications and disaster recovery, search and rescue. The approach we provide uses the CSMA/CA medium access protocol and additional reservation and control mechanisms to guarantee quality of service in the ad hoc network system. The reason we choose the CSMA protocol instead of other MAC protocols is that it is used in most of the current wireless LAN productions. Via the QoS routing information and reservation scheme, network resources are dynamically allocated to each multimedia application.

With the fast deployment of wireless hand-held terminals, multimedia applications are getting more and more significant for mobile networks. As a result, the QoS (quality of service) support for multimedia in mobile networks has become more and more important. Resource reservation is the current scheme supporting QoS for the Internet. However, reservation of resources and maintenance of QoS for the mobile host as it moves from one area to another create a new set of challenges. It needs other mechanisms to help maintain QoS. In this paper, we propose to use a combination of MRSVP and CAC (connection admission control) to enforce QoS guarantees in mobile networks. Our CAC algorithm not only considers the connection number in the current cell, but also takes the reservation flows of adjacent cells into account. And the simulation results show that our algorithm does provide good performance for mobile networks.

The hierarchical network structure significantly reduces the size and maintenance cost of routing table for huge networks. But in ad hoc networks, no fixed host leads to the challenge of the hierarchical structure, since the topology information needs to be updated dynamically due to membership changes caused by mobility. To construct the hierarchical structure of physical locations, we adopt a cluster infrastructure to partition the network into different groups for physical location maintenance. In order to construct the hierarchical structure of logical locations, all hosts are divided into several domains, each one of them has one corresponding domain location server to record all of the member physical locations (cluster locations). With the hierarchical structure, most necessary routing information can be ignored.

With the fast deployment of the satellite, the integration of the Internet and the satellite will be the important tendency toward providing broadband multimedia transmission service. In the future, with the wide covering range, high bandwidth as well as the broadcasting capability, the satellite communication can easily achieve the ubiquitous transmission for meeting the requirement of the future multimedia applications. Besides, the QOS (quality of service) support for the multimedia is also important. This paper proposes a Spoofing RSVP (Resource Reservation Protocol) based on an integrated platform to guarantee the QOS in multimedia transmission. A CAC (call admission control) is proposed to support this reservation scheme. We compare the Spoofing RSVP with the traditional RSVP through simulation experiments. The results show that the Spoofing RSVP is suitable for the integrated network. In addition; the CAC message could be feedback to the integrated platform to optimize the network resource utilization.

In this paper we address the evaluation of speech quality through a wireless network as perceived by the user. User perceived evaluation (in addition to the usual network metrics including delay, throughput, packet loss statistics, etc.) is critical in the design of wireless multimedia networks where speech and video play a key role and are affected by several factors, such as network performance and encoding scheme. We use two approaches for our evaluation: small scale testbed implementation and hybrid simulation. The testbeds are implemented either by UDP (user datagram protocol) connection or UCLA talk connection. The hybrid simulation is event driven and is based on the Maisie parallel simulation language. It uses speech traces for inputs and plays back the speech outputs off-line. There are several advantages in using the simulation tool, mainly from the point of view of scalability and new protocol feature testing. At the same time, the real life testbed provides verification of the simulator assumptions, albeit on a small scale.