The 1st free5GC World Forum brings together researchers, industry professionals, and open-source contributors to explore the challenges and recent advancements in 5G core networks, with a particular focus on security and the transformative role of free5GC, the leading open-source 5G Standalone (SA) core network. free5GC, a project hosted by the Linux Foundation, is a fully 3GPP-compliant, open-source 5G core network platform. It empowers researchers, developers, and businesses to drive innovation in 5G systems by providing a robust prototyping environment for next-generation connectivity solutions. Recent notable architectures, such as L25GC+, which aims to significantly reduce control plane latency while maintaining 3GPP compliance, exemplify how free5GC facilitates the development and testing of cutting-edge ideas on a production-grade 5G core. The forum offers a unique opportunity for participants to share insights, present innovations, and shape the future direction of free5GC and next-generation mobile networks.

This paper presents the Least Connection-First algorithm, commonly employed in TCP, as a load balancing mechanism implemented within a P4 switch. While previous work in SilkRoad demonstrated the feasibility of P4 switches for cost-effective, high-speed Layer-4 stateful load balancing using hash-based algorithms, these approaches assumed uniform server workloads, making them susceptible to hash collisions and potential connection initiation failures. In contrast, our research leverages the inherent characteristics of TCP connections – specifically, the correlation between request frequency and connection duration – to enhance load balancing performance. By leveraging the P4 switch’s ability to identify SYN and FIN packets in the data plane, our approach enables the forwarding of these control packets to a central controller. The controller then dynamically assigns incoming connections to servers with the fewest active connections. We conduct our experiment on a P4 hardware switch for performance validation. Experimental results demonstrate that our proposed method exhibits superior performance compared to traditional hash-based and query-based Least Connection-First schemes.

We design and implement a 3GPP Rl6-compliant data plane for 5G networks to support Time Sensitive Networks (TSN) in bridge mode based on free5GC and UERANSIM, two open-source projects. We address the concerns of time synchronization in 5G systems, the interaction between the 5G TSN bridge and the TSN control plane, maintenance of TSN capabilities by the 5G TSN bridge, and clock drift of the 5G TSN bridge. Through experiments, the accuracy of a 5G TSN bridge with the proposed time synchronization capability is demonstrated to be 13 times better than that of one without this capability. Furthermore, we analyze the performance of the topology establishment functionality provided by the 5G TSN bridge and show that the impact of clock drift can be reduced by implementing clock drift reporting in the 5G TSN bridge. Finally, we present a solution to implement a 5G system data plane to support TSN and provide an open platform for further extensions and improvements based on the results of this work, which can be used to continue the development of relevant features for 3GPP R17 and RlS.

As the number of connected devices continues to increase and the complexity of services supported by 5G grows, significant challenges may arise in managing the important signaling and processing of the control plane. This will result in extensive resource utilization. While deploying additional resources may be relatively straightforward, the decision-making process for resource scaling poses a challenge. Hence, this paper provides the 5G network management system with the capability of system load prediction to assist in the decision-making process of resource scaling. To apply system load prediction to the 5G core (5GC) network, we collect real-time performance measurement data from the 5GC network using open-source 5G software. We utilize this data to train neural networks to predict the load of 5GC network functions. Additionally, we design a specific loss function for the prediction model to align with our resource scaling strategy objectives. Experimental results demonstrate that the application of performance measurements enhances the accuracy of load prediction tasks, thereby contributing to more effective resource management.

Offloading in edge computing scenarios is considered a prime solution to reduce computational time and also energy resources of the user equipment. This paper focuses on computation offloading from the user equipment to co-located vehicular microclouds. We derive the closed-form system metrics and cross-validate them with simulations. Through a comprehensive observation of vehicular microcloud behavior, the proposed two-state offloading algorithm (TSOA) provides the optimal offloading configuration in both planning and operating states. Finally, our evaluation demonstrates that the proposed TSOA performs optimally among the three offloading schemes.

Cloud-native microservice applications use different communication paradigms to network microservices, including both synchronous and asynchronous I/O for exchanging data. Existing solutions depend on kernel-based networking, incurring significant overheads. The interdependence between microservices for these applications involves considerable communication, including contention between multiple concurrent flows or user sessions. In this paper, we design X-IO, a high-performance unified I/O interface that is built on top of shared memory processing with lock-free producer/consumer rings, eliminating kernel networking overheads and contention. X-IO offers a feature-rich interface. X-IO’s zero-copy interface supports building provides truly zero-copy data transfers between microservices, achieving high performance. X-IO also provides a POSIX-like socket interface using HTTP/REST API to achieve seamless porting of microservices to X-IO, without any change to the application code. X-IO supports concurrent connections for microservices that require distinct user sessions operating in parallel. Our preliminary experimental results show that X-IO’s zero-copy interfaces achieve 2.8x-4.1x performance improvement compared to kernel-based interfaces. Its socket interfaces outperform kernel TCP sockets and achieve performance close to UNIX-domain sockets. The HTTP/REST APIs in X-IO perform 1.4 x-2.3 x better than kernel-based alternatives with concurrent connections.

In 5G, network functions can be scaled out/in dynamically to adjust the capacity for network slices. The scale-out/-in procedure, namely autoscaling, enhances performance by scaling out instances and reduces operational costs by scaling in instances. However, the autoscaling problems in 5G networks are different from those in traditional cloud computing. The 5G network functions must be considered the simultaneous deployment of multiple instances; moreover, the deployment of 5G network functions is more frequent than that of traditional cloud computing. Both the number and timing of deployment will substantially affect the cost-effectiveness of the system. In this paper, we first identify the autoscaling issues specifically based on the 3GPP standards. We develop a low-complexity analytical queuing model to formulate the problem and quantify a set of performance metrics with closed-form solutions. The proposed analytical model and closed-form solutions are cross-validated by extensive simulations. The analytical model offers design insights and theoretical guidelines, helping us study the effectiveness of reservations. We proposed a dynamic block-setup reservation algorithm (DBRA) to find the optimal reserved number and threshold value of network slices. Therefore, mobile operators can balance the system's cost-effectiveness without large-scaled testing and real deployment, saving cost on time and money.

In 5G, multi-access edge computing enables the applications to be offloaded to near-end edge servers for faster response. According to the 3GPP standards, users in 5G are separated into many types, e.g., vehicles, AR/VR, IoT devices, etc. Specifically, the high-priority traffic can preempt edge resources to guarantee the service quality. However, even if a traffic is transmitted with low priority, its latency requirement in 5G is much lower than that in 4G. Too strict latency requirement and priority-based service make resource configuration difficult on the edge side. Therefore, we propose the edge-cloud offloading mechanism, in which each edge server can offload tasks to back-end cloud server to ensure service quality of both high- and low-priority traffic. In this paper, we establish a priority-based queuing system to model the edge-cloud offloading behaviors. Based on the formulation of our system model, we propose Knapsack Potential Game (KPG) to derive an optimal offloading ratio for each edge server to balance the cost-effectiveness of the overall system. We demonstrate that KPG has low computational complexity and outperforms two baseline algorithms. The results indicate that KPG’s performance is optimal and provides a theoretical guideline to operators while designing their edge-cloud offloading strategies without large-scale implementation.

In order to provide an industry-grade 5G Private Network (PN) to the enterprises, the ultra-reliability communication becomes a key feature to successfully deploy 5G PNs for the future industry 4.0 applications. This paper article will use the free5GC, which is the world's first open-source 5G core (5GC) network that complies with 3rd Generation Partnership Project (3GPP) R15 standards, developed in the laboratory as the base to develop a redundant transmission technique for Ultra-Reliable Communication in 5G Core Networks. We compare the its performance and reliability with the original a single protocol data unit (PDU) session in free5GC. Moreover, it confirmed that the reliability it brings would enable users to have a better user experience.

Cellular network control procedures (e.g., mobility, idle-active transition to conserve energy) directly influence data plane behavior, impacting user-experienced delay. Recognizing this control-data plane interdependence, L25GC re-architects the 5G Core (5GC) network, and its processing, to reduce latency of control plane operations and their impact on the data plane. Exploiting shared memory, L25GC eliminates message serialization and HTTP processing overheads, while being 3GPP-standards compliant. We improve data plane processing by factoring the functions to avoid control-data plane interference, and using scalable, flow-level packet classifiers for forwarding-rule lookups. Utilizing buffers at the 5GC, L25GC implements paging, and an intelligent handover scheme avoiding 3GPP's hairpin routing, and data loss caused by limited buffering at 5G base stations, reduces delay and unnecessary message processing. L25GC's integrated failure resiliency transparently recovers from failures of 5GC software network functions and hardware much faster than 3GPP's reattach recovery procedure. L25GC is built based on free5GC, an open-source kernel-based 5GC implementation. L25GC reduces event completion time by ~50% for several control plane events and improves data packet latency (due to improved control plane communication) by ~2×, during paging and handover events, compared to free5GC. L25GC's design is general, although current implementation supports a limited number of user sessions.

Existing global navigation satellite systems (GNSSs) provide insufficient accuracy in terms of GNSS elevation and are limited by two-dimensional maps. Therefore, when traveling along a road that branches off to an overpass, it is impossible to immediately determine whether the vehicle is on the overpass. Inaccurate navigation not only causes anxiety for some drivers but also can lead to car accidents. This problem has existed since the invention of GNSSs. To the best of our knowledge, we are the first to conduct a large number of on-road experiments at different locations using off-the-shelf smartphones equipped with barometers. Based on the preliminary results of the wind tunnel and on-road experiments, we propose barometer-assisted road-layer detection (BARLD), which uses the changes in atmospheric pressure to determine therelativealtitude. Comprehensive experiments in many different scenarios, including on overpasses, underpasses, and in parking lots, are discussed in this paper. The results confirm that the BARLD can effectively assist consumer-grade GNSSs to determine road layers. The source code of BARLD is publicly available, which would benefit the research community.

The Virtual Customer Premises Equipment (vCPE) technology has recently emerged to reduce telecom operators' OPEX and CAPEX. It evolved from Network Function Virtualization (NFV) and Software Defined Networking (SDN) technologies. This paper proposes a flexible vCPE framework to enable dynamic chaining of Virtual Network Functions (VNF) by using Programmable Protocol-independent Packet Processors (P4) switches. It can obtain a much better packet processing performance compared to the pure software vCPE solution. The OpenFlow switch provides similar hardware acceleration, but it executes the flow tables in a fixed order, and it is not possible to skip the flow tables, which are not subscribed to by a customer. However, P4, the domain-specific language used to describe how to process packets on a data plane (DP), gives more flexibility than the OpenFlow. It provides a way to avoid the fixed flow table execution order and can introduce a new service on the fly. Our flexible vCPE framework can be achieved by the synergies between an NFV controller on the cloud and a P4 switch at the edge. In this paper, an Open Network Operating System (ONOS) controller with P4Runtime is used as a VNF control plane and a P4 Behavioral Model (BMv2) software switch is used as a DP. Finally, dynamic function chaining is realized using three possible implementations, viz. multi-instance, clone, and resubmit. P4 language is used for the implementations. Experimental results show that a multi-instance based solution is better than a resubmit and clone.

In 5G mobile networks, users can request services from different network slices in the core network. However, in 3GPP Release 16 (R16), Mutually Exclusive Access to Network Slices (MEANS) was introduced, in which some services may not be accessed simultaneously by the same user. Because the users do not know which slices are mutually incompatible, and the core network has no specific way to deal with it, the mechanisms defined in the standards will not only cause signaling overhead but waste additional time. In this paper, we propose Adaptively Prioritized Subset Algorithm (APSA) as a solution to MEANS, which follows the principles discussed in the 3GPP documents. We conducted an extensive simulation to evaluate the proposed APSA. The results show that our proposed APSA not only uses fewer signaling messages to access the network slices but also outperforms other algorithms compared in this paper.

Mobility type identification is posed as the first step for 5G mobile networks to realize mobility management. The telecom operators can deploy customized network slices for different users with different mobility types. In this paper, we propose Cellular to Image Transportation Type Identification (CITTI) to identify transportation types by using cellular information only. CITTI takes a set of cellular data and transforms them into cellular-based images. The Convolutional Neural Network-based identifier is then used to identify the transportation type. With over 700 hours of two real-world datasets, several experiments are conducted to verify the accuracy of the proposed CITTI. The experimental results show that CITTI can achieve almost 95% accuracy and outperforms prior studies.

In 5G, the requirement of transmission latency is stricter than that in 4G. To enhance transmission efficiency, a user plane function (UPF) with a specific packet processing mechanism is necessary. However, UPF must communicate with the session management function (SMF), which will send the packet processing rules to UPF. Those rules will substantially occupy UPF storage. Moreover, customizing a UPF needs to reconstruct N3, N4, N6, and N9 interfaces, which takes much time for developers. To this end, we propose the user plane function development framework (UPFDF), which modularizes the functions in the UPF, supporting customization to connect different types of packet processing mechanisms. With UPFDF, we address the UPF capacity problem and improve the flexibility of the system.

Accurate positioning in global navigation satellite system (GNSS)-denied environments, such as tunnels and underpasses, remains a challenge. Navigation systems for such environments need to strike a balance between price and precision. In this paper, we propose magnetic vehicular positioning (MVP), a navigation system that guides drivers in GNSS-denied environments. The key idea of MVP is to extract magnetic fingerprints from geomagnetic field anomalies. By comparing the measured magnetic field against a magnetic map, positioning can be achieved without GNSS signals. Our proposed matching algorithm allows MVP to provide 5.14 m positioning accuracy. We conducted large-scale real-road experiments for 36 months in two countries and 56 tunnels to demonstrate the effectiveness of the proposed system. Because MVP can be deployed on off-the-shelf smartphones, our approach makes accurate navigation in GNSS-denied environments affordable.

Next generation intelligent transportation systems aim at many cooperative perception and cooperative driving functions that need significant computational resources. Offloading such tasks to some mobile edge computing solutions is considered part of the solution, which is currently investigated in the scope of 5G networks. In the automotive context, such edge systems could be road-side units (RSU), which, however, can easily be overloaded at peak times. Vehicular micro-cloud approaches have been proposed to overcome such problems by sharing computational resources of nearby cars. In this study, we propose an offloading system architecture to enable such offloading such vehicular micro-cloud interconnected by a 5G core network. We model the system as a queueing model to derive closed-form solutions for selected performance metrics. Based on these insights, we propose the Double-Check Offloading Algorithm (DCOA) to obtain the best offloading ratio to the vehicular micro-cloud. Our simulation results show the proposed DCOA has better system performances compared with four other offloading schemes.

Today's GPS navigators have difficulty determining altitude on multi-layer roads. In this paper, we first explain how the structures of overpasses and bridges have special magnetic fields. We then propose how to use the magnetometers which come with off-the-shelf smartphones to assist GPS navigators to determine position on multi-layer roads by detecting and matching these magnetic fingerprints. We also present performance evaluation on different multi-layer roads to show the feasibility of the proposed method.

One of the main goal of 5G networks is to provide ultra-reliable low latency service to users. When users keep accessing the system, the traffic in 5G core network (5GC) may be congested. Thus, we propose a load balance algorithm to select the best traffic data routing path based on the traffic loading in the 5GC. The proposed algorithm is implemented in a 5G testbed called free5GC. The experimental results show that our proposed algorithm outperforms the traditional round-robin load balance algorithm in many performance metrics.

It is crucial for future 5G networks to intelligently understand how users move so that the networks can allocate different resources efficiently. In this paper, we try to find practical features to identify four common types of motorized transportations, including High-Speed Rail (HSR), subway, railway, and highway. We propose a system architecture that can provide accurate, real-time, and adaptive solution by using cellular information only. Because we do not use GPS as that in most of the prior studies, we can reduce energy consumption, size of log data, and computational time. Around 500-hour data are collected for performance evaluation. Experimental results confirm the effectiveness of the proposed algorithm, which can improve well-known machine learning algorithms to approximately 98% classification accuracy. The results also show that battery consumption can be reduced about 37%.

We propose a novel network architecture called Residual Attention U-Net (ResAttU-Net) for segmenting hepatic lesions. Our model incorporates residual blocks that can extract more complex features as compared with traditional convolutional layers combined with a skip-connection attention module that learns to focus on the relevant features for the task of hepatic lesions segmentation. Moreover, we train our model using an adaptive weighted dice loss that prioritizes the pixels of the tumor class over the pixels of the background class. We evaluate our model on the MICCAI Liver Tumor Segmentation (LiTS) benchmark dataset. Our experimental results show that our method significantly improves upon several state-of-the-art baselines for hepatic lesion or liver tumor segmentation.

Today's GPS navigators have difficulty determining altitude such as whether a car is under or on an overpass. In this paper, we show how to use the barometers, which come with off-the-shelf smartphones, to improve vertical positioning accuracy. We will present performance testing results from different real road scenarios to show the feasibility of the proposed method.

Mobile Crowd Sensing (MCS) is a promising paradigm to collect large-scale network data globally. However, how to motivate people to collect and share data is a challenge. We believe the major reason why many MCS systems are not pervasive is because there are no incentives for people to use them. In this paper, we present SensingGO, a system which encourages people to keep sensing data by integrating incentive mechanisms. The sensed data are then transmitted to our backend server. The data we collected and the source code of SensingGO are open to anyone freely. We also demonstrate the analysis of real mobile data collected from SensingGO.

For future 5G core networks, Service Based Architecture (SBA) has been proposed in 3GPP Release 15. To realize the idea of SBA, we propose Service Level Virtualization (SLV) in which each network entity is decomposed into different service blocks to provide respective services. In addition, each service block can be virtualized independently into different virtual machine. Thus, SLV can increase the flexibility of the core network.

Virtualizing the EPC (Evolved Packet Core) in modern carrier-grade networks provides more flexible and reliable network services by decoupling dependence on the hardware. Hy- pervisor and container are two popular virtualization techniques nowadays to enable virtualization of EPC. In this paper, we compared the Open5GCore, a 5G EPC prototype, over KVM and Docker, which are representatives of the hypervisor and container techniques. Moreover, to verify how each supports new services for Internet of Things (IoT) and Machine-to-Machine (M2M) communications, we also analyze the performance of two systems with the IoT and M2M traffic generated by Open5GMTC, a prototype tool for IoT/M2M platforms.

Device-to-device (D2D) communication is mainly launched by the transmission requirements between devices for specific applications such as proximity services in long-term evolution advanced networks, and each application will form a group of registered devices for the network-covered and network-absent D2D communications. During the applications of D2D communication, each device needs to identify the other devices of the same group in proximity by their group identity. This leads to the exposure of group information, by which the usage of applications can be analyzed by eavesdroppers. Hence, this paper introduces network-covered and network-absent authenticated key exchange protocols for D2D communications to guarantee accountable group anonymity, end-to-end security to network operators, as well as traceability and revocability for accounting and management requirements. We formally prove the security of those protocols, and also develop an analytic model to evaluate the quality of authentication protocols by authentication success rate in D2D communications. Besides, we implement the proposed protocols on android mobile devices to evaluate the computation costs of the protocols. We also evaluate the authentication success rate by the proposed analytic model and prove the correctness of the analytic model via simulation. Those evaluations show that the proposed protocols are feasible to the performance requirements of D2D communications.

One of the most important technologies for future 5G networks is to utilize Network Function Virtualization (NFV) to virtualize the network components. NFV provides flexibility, short time to market, and low cost solution to build network services, which are important features of 5G networks. Although the idea of virtualization is just being applied to cellular networks, it has been used in the community of cloud computing. There are two main virtualization techniques, hypervisor and container. In this paper, we present our practical experience of virtualizing Open5GCore, a commercial product of SDN‐enabled Evolved Packet Core (EPC), over hypervisor and container. In addition to describing how to virtualize Open5GCore, we also present the experimental performance evaluation of the systems. Finally, some important lessons learned are provided.

It is envisioned in the future that not only smartphones will connect to cellular networks, but all kinds of different wearable devices, sensors, vehicles, home appliances, VR headsets, robots, will also connect to cellular networks. Because the characteristics of these devices differ largely, people argue that future 5G systems should be designed to elastically accommodate to the different users. In this paper, we propose a reconfigurable core network called RECO that demonstrates how to implement customized virtual core network entities efficiently to suit for users with different characteristics. We then build a testbed to verify our proposed RECO architecture. Finally, we will open source our RECO in the near future so that the research community can take benefit out of it.

IoT (Internet of Things) has attracted a lot of attention recently. IoT devices need to report their data or status to base stations at various frequencies. The IoT communications observed by a base station normally exhibit the following characteristics: (1) massively connected, (2) lightly loaded per packet, and (3) periodical or at least mostly predictable. The current design principals of communication networks, when applied to IoT scenarios, however, do not fit well to these requirements. When a large number of devices contend to send small packets, the signaling overhead is not cost-effective. To address this problem, our previous work [1] proposes the Hint protocol, which is slot-based and schedule- oriented for uploading IoT devices' data. In this work, we extend [1] to support data transmissions for multiple resource blocks. We assume that the uplink payloads from IoT devices are small, each taking very few slots (or resource blocks), but devices are massive. The main idea is to "encode" information in a tiny broadcast that allows each device to "decode" its transmission slots, thus significantly reducing transmission overheads and contention overheads. Our simulation results verify that the protocol can significantly increase channel utilization compared with traditional schemes.

The urgency of improving user experience has reached a critical point in the high-speed rail environment. However, there is little literature considering authentication failure problems in the high-speed rail environment. In this paper, we present a new authentication architecture for Taiwan High-Speed Rail (THSR). This new authentication architecture applies Software-Defined Network (SDN)- based principles to an outbound LTE gateway platform. We propose a post-authentication method suitable for the high-speed mobile environment, such as THSR. The proposed architecture and successful authentication ratio method can improve user experience via authentication and network access latency relative to the existing system.

In Machine-to-Machine (M2M) communications, devices can automatically communicate with each other without any intervention by humans. However, LTE-A is primarily designed and optimized for Human-to-Human (H2H) communications. Even though LTE-A has defined Machine-Type Communications (MTC), several parts are still undefined or follow the existing H2H standards. Specifically, the existing paging mechanism in LTE-A will substantially increase the computational load and signaling overhead of the system when there are many M2M devices. Therefore, we propose an effective solution to mitigate this problem. Compared with the traditional paging mechanism defined in LTE-A, the proposed solution can save more energy for M2M devices, reduce signaling overhead and alleviate the network's load significantly.

In cloud computing paradigm, virtual resource autoscaling approaches have been intensively studied recent years. Those approaches dynamically scale in/out virtual resources to adjust system performance for saving operation cost. However, designing the autoscaling algorithm for desired performance with limited budget, while considering the existing capacity of legacy network equipment, is not a trivial task. In this paper, we propose a Deadline and Budget Constrained Autoscaling (DBCA) algorithm for addressing the budget-performance tradeoff. We develop an analytical model to quantify the tradeoff and cross-validate the model by extensive simulations. The results show that the DBCA can significantly improve system performance given the budget upper-bound. In addition, the model provides a quick way to evaluate the budget-performance tradeoff and system design without wide deployment, saving on cost and time.

Collecting data from a tremendous amount of Internet-of-Things (IoT) devices for next generation networks is a big challenge. A large number of devices may lead to severe congestion in Radio Access Network (RAN) and Core Network (CN). 3GPP has specified several mechanisms to handle the congestion caused by massive amounts of devices. However, detailed settings and strategies of them are not defined in the standards and are left for operators. In this paper, we propose two congestion control algorithms which efficiently reduce the congestion. Simulation results demonstrate that the proposed algorithms can achieve 20~40% improvement regarding accept ratio, overload degree and waiting time compared with those in LTE-A.

Network Function Virtualization (NFV) enables mobile operators to virtualize their network entities as Virtualized Network Functions (VNFs), offering fine-grained on-demand network capabilities. VNFs can be dynamically scale-in/out to meet the performance desire and other dynamic behaviors. However, designing the auto-scaling algorithm for desired characteristics with low operation cost and low latency, while considering the existing capacity of legacy network equipment, is not a trivial task. In this paper, we propose a VNF Dynamic Auto Scaling Algorithm (DASA) considering the tradeoff between performance and operation cost. We develop an analytical model to quantify the tradeoff and validate the analysis through extensive simulations. The results show that the DASA can significantly reduce operation cost given the latency upper-bound. Moreover, the models provide a quick way to evaluate the cost- performance tradeoff and system design without wide deployment, which can save cost and time.

LTE femtocells have been commonly deployed by network operators to increase network capacity and offload mobile data traffic from macrocells. A User Equipment (UE) camped on femtocells has the benefits of higher transmission rate and longer battery life due to its proximity to the base stations. However, various user mobility behaviors may incur frequent signaling overhead and degrade femtocell offloading capability. To efficiently offload mobile data traffic, we propose a Threshold Offloading (TO) algorithm considering the trade-off between network signaling overhead and femtocell offloading capability. In this paper, we develop an analytical model to quantify the trade-off and validate the analysis through extensive simulations. The results show that the TO algorithm can significantly reduce signaling overhead at minor cost of femtocell offloading capability. Moreover, this work offers network operators guidelines to set offloading threshold in accordance with their management policies in a systematical way.

In this paper, we propose WiAVL, a novel Automatic Vehicle Location (AVL) system based on Wi-Fi Device-to-Device (D2D) communications. WiAVL can monitor, record and notify the location of public transportation vehicles with low communication cost by leveraging Wi-Fi Beacons. In addition, we address the interference problem. A proof-of-concept prototype is implemented. Experimental results are also presented to demonstrate the feasibility and performance results of the proposed system.

3GPP introduced the key management mechanism (KMM) in evolved multimedia broadcast/multicast service (eMBMS) to provide forward security and backward security for multicast contents. In this paper, we point out that KMM may lead to frequent rekeying and re-authentication issues due to eMBMS's characteristics: 1) massive group members; 2) dynamic group topology; and 3) unexpected wireless disconnections. Such issues expose extra load for both user equipment (UE) terminals and mobile operators. It seems prolonging the rekeying interval is an intuitive solution to minimizing the impact of the issues. However, a long rekeying interval is not considered the best operational solution due to revenue loss of content providers. This paper quantifies the tradeoff between the load of the UEs and the operators as well as the revenue loss of the content providers. Moreover, we emphasize how essential this rekeying interval has impacts on the problems. Using our proposed tradeoff model, the operators can specify a suitable rekeying interval to best balance the interest between the above three parties. The tradeoff model is validated by extensive simulations and is demonstrated to be an effective approach for the tradeoff analysis and optimization on eMBMS.

To improve the quantitative accuracy of linear attenuation coefficients measured by computed tomography (CT), we used a single scatter model to estimate the Compton scatter distribution and then a polychromatic image reconstruction algorithm, namely the iterative maximum-likelihood polychromatic algorithm for CT (IMPACT), was implemented to include scatter correction (SC). To perform the IMPACT, the X-ray spectra of a tube were estimated via an expectation-maximization (EM) algorithm with SC. To test the accuracy of the estimated spectra, the projection images of cubic phantoms containing different depths of polymethylmethacrylate (PMMA) were acquired. The percentage of root mean square errors (%RMSE) of the measured transmission data and calculated transmission values were used to evaluate the accuracy of the estimated spectra. In addition, a hydroxylapatite (HA) phantom was used to study streak artifacts and evaluate the accuracy of the linear attenuation coefficients estimated using the IMPACT with SC. The %RMSE of the EM-with-SC estimated spectra were all lower than 1% and were also smaller than that without SC. The error in the quantification of the HA linear attenuation was only about 3% after SC. Our results showed that the quantitative accuracy of the linear attenuation coefficients measured with a cone beam CT was improved when the IMPACT with SC was used.

Due to safety reasons, using mobile phones while driving is prohibited in many countries. Research has also shown that motorcycle riders are 20 times more likely to be killed in a crash than vehicle occupants. Therefore, it is more critical to restrict the use of mobile phones of motorcycle drivers than car drivers. There are some studies that focus on how to distinguish phone use between a driver and other passengers in a car. The techniques used for cars, however, are not always applicable to motorcycles. In this paper, we propose a way to detect phone use of motorcycle drivers. By using two low-cost Bluetooth emitters, mobile phones of the driver and the passenger can measure the signal strengths and decide their locations. We have conducted extensive experiments with various smartphones. The results show that on average we can achieve 96% accuracy.

In this paper, we analyze the packet session channel holding time for packet-switched cellular networks. Channel holding time depends on mobility which is characterized by cell residence time in this paper. We apply Hyper-Erlang distribution model to investigate the packet session channel holding time in which a session will experience active and idle periods. In terms of new session, handoff session in busy mode, handoff session with new arrival packets in idle mode and handoff session without arrival packet in idle mode, we demonstrate that the effective channel holding time is exponentially distributed if and only if the cell residence time is exponentially distributed. The analytical results provide a new approach to evaluate traffic performance and system design in packet-switched cellular networks.

Cognitive radio has received great attention recently for its ability to improve spectrum efficiency by letting secondary users to access spectrum resource that is unoccupied by primary users. However, cognitive radio also brings new challenges in the design of future wireless networks. In this paper, we investigate the problem of resource allocation in cognitive radio networks. Specifically, we consider the problem of proportional fair scheduling in cognitive radio relay networks. Our problem formulation takes into account the fluctuations of usable spectrum resource, channel quality variations caused by frequency selectivity, and interference caused by different transmit power levels. We prove that the problem is NP-hard and is computationally infeasible to be solved in a timely manner by using brute force algorithms. An easy-to-compute upper bound for the formulated problem is also derived. We then propose two heuristic algorithms that are easy-to-implement, yet achieve performance close to the upper bound. The proposed algorithms can be executed and finished within 1 millisecond. Thus, they can meet the requirement of real-time scheduling. Simulation experiments verify that the proposed algorithms can achieve good proportional fairness among users and enhance system throughput by proper power control.

The WiMAX Forum has defined a two-tiered mobility management to minimize handover delay and packet loss. However, it leads to another problem: When to perform ASN GW relocation? The standards only define the ASN GW relocation procedures without specifying when the ASN GW relocation should be performed. It is left for vendors and operators to develop their own proprietary solutions. In this paper, we propose an algorithm, which incorporates traditional Admission Control (AC) and Wiener Process (WP)-based prediction algorithms to determine when to carry out ASN GW relocation. We further develop an analytical model to analyze the proposed algorithm. Simulations are also conducted to evaluate the performance of the proposed algorithm. The results show that the proposed algorithm can improve the performance significantly in terms of blocking probability, dropping probability, average serving rate, and average signaling overhead.

Abstract Many wireless systems have been proposed and deployed for decades. However, most of them are incompatible. It is expected that various wireless systems will still coexist in the near future. How to integrate them, thus, is an important issue. The integration should be done in both radio access network (RAN) and core network. A mobile user could overcome the incompatibility of different RANs by using multiple radio interfaces or software defined radio (SDR). However, it still requires a common core network to achieve universal roaming. If it is not possible to deploy a common core network, different core networks should be compatible. Unfortunately, standard organizations have been defining their own core networks. The roaming among heterogeneous networks, thus, has become a challenge. Earlier, we have proposedReconfigurable Architecture and Mobility Platform(RAMP) to address this issue. However, RAMP mainly considers mobility management. In this paper, we presentsecureRAMP (sRAMP) which extends RAMP to support reconfigurability in security. This paper presents the design and implementation of sRAMP. To demonstrate the feasibility of sRAMP, a testbed has been constructed. This paper also presents the experimental results conducted by using the testbed. Furthermore, a brief comparison between the proposed sRAMP and other related studies is also presented. Copyright © 2010 John Wiley & Sons, Ltd.

The IETF NEtwork MObility (NEMO) working group has considered how to enable an entire network to move from one location to another. Mobile Virtual Private Network (VPN) has been developed to secure mobile user's communication between untrusted external networks and the protected private internal network. However, the IETF's mobile VPN does not address how to support NEMO. In addition, it is not suitable for real-time applications. In this paper, we propose architecture and protocols to support VPN in NEMO, which is called Secure NEMO (SeNEMO). The proposed SeNEMO, based on Session Initiation Protocol (SIP), is specifically designed for real-time applications over VPN. It allows an entire network to move and still maintains session continuity. In addition to analyzing the security vulnerabilities, we also propose analytical models to evaluate the performance of the proposed SeNEMO. The analysis is validated by extensive simulations. The results show that the proposed SeNEMO can reduce signaling cost significantly.

The Generic Access Network (GAN) developed by 3GPP extends services to unlicensed spectrum. A mobile station (MS) with multiple air interfaces can access 3GPP services through GAN and roam seamlessly between different radio access networks. However, mobility management and resource management are critical issues in GAN. To allocate GAN resources efficiently, we propose Adaptive Keep-alive Interval (AKI). By using AKI, an MS can send less signaling messages. In addition, AKI can increase system utilization by releasing unused resources. In this paper, we develop a mathematical model to evaluate the handoff failure probability of the proposed AKI. The analysis is validated by extensive simulations. The results show that the proposed AKI can reduce handoff failure probability and increase GAN utilization significantly.

The Generic Access Network (GAN) developed by 3GPP extends services to unlicensed spectrum. A mobile station with multiple air interfaces can access 3GPP services through GAN and roam seamlessly between different radio access networks. However, resource management is a critical issue in GAN. To allocate GAN resources efficiently, we propose Adaptive Keep-alive Interval (AKI). By using AKI, an MS can send less signaling messages. In addition, AKI can increase system utilization by releasing unused resources. The proposed AKI is evaluated by extensive simulations. The results show that the proposed AKI can reduce signaling overhead and increase GAN utilization significantly.

IEEE 802.16j is defining standards for Multihop Relay (MR) networks. With many low cost Relay Stations (RSs), a Base Station (BS) can diminish the radio range but extend the coverage by RSs. Besides, frequency can be reused in different RSs. When using real-time services in an 802.16j MR network, fixed bandwidth is allocated to each intermediate hop along the path between the MS and the MR-BS. The MS does not need to request bandwidth for each packet in each hop. Therefore overhead is eliminated and packet latency is reduced. However, if an MS suffers from bad channel and cannot transmit packets to its access RS correctly, all bandwidths allocated from the access RS to the MR-BS along the multihop path are wasted. This will decrease the system performance. In this paper, we propose a Cooperative Adaptive Partner Selection (CAPS) algorithm to select a relaying partner to help the MSs experiencing bad channel condition. Simulation results show that the proposed technique can improve the system performance significantly.

IEEE 802.16 is defining standards for mobile multihop relay (MMR). The major purpose of MMR is to efficiently extend the coverage of a BS and to enhance the system throughput. Relay station (RS) has been introduced to fulfill this goal. However, packets in MMR would have a large probability of failure transmission because not all links over the multihop path are in good channel condition. Therefore, hybrid automatic repeat request (HARQ) has been designed to increase the reliability in multihop transmission. However, the retransmission mechanism proposed in 802.16j is not efficient. It will result in high packet delay. In this paper, we propose dynamic pre-allocation HARQ (DP-HARQ) which pre-allocates bandwidth for HARQ. Therefore, the packet delay is reduced significantly. The pre-allocated bandwidth is dynamically adjusted so the channel utilization will not be degraded much. We also propose mathematical models to analyze the proposed DP-HARQ. The analysis is validated by extensive simulations. Results show that the proposed DP-HARQ can reduce packet delay and jitter significantly.

This paper presents an energy conservation scheme, Maximum Unavailability Interval (MUI), to improve the energy efficiency for the Power Saving Class of Type II in IEEE 802.16e. By applying the Chinese Remainder Theorem, the proposed MUI is guaranteed to find the maximum Unavailability Interval, during which the transceiver can be powered down. We also propose new mathematical techniques to reduce the computational complexity when solving the Chinese Remainder Theorem problem. Because the computational complexity is reduced significantly, the proposed MUI can be practically implemented in real systems. The proposed MUI is fully compatible with the 802.16e standard. It provides a systematic way to determine the start frame number, one of the important parameters defined in the standard. In addition to analyzing the computational complexity, simulations and experiments are conducted to evaluate the performance of the proposed algorithms.

To support fast and efficient handovers in mobile WiMAX, we propose fast intra-network and cross-layer handover (FINCH) for intradomain (intra-CSN) mobility management. FINCH is a complementary protocol to mobile IP (MIP), which deals with interdomain (inter-CSN) mobility management in mobile WiMAX. FINCH can reduce not only the handover latency but also the end-to-end latency for MIP. Paging extension for FINCH is also proposed to enhance the energy efficiency. The proposed FINCH is especially suitable for real-time services in frequent handover environment, which is important for future mobile WiMAX networks. In addition, FINCH is a generic protocol for other IEEE 802-series standards. This is especially beneficial for the integration of heterogeneous networks, for instance, the integration of WiMAX and WiFi networks. Both mathematical analysis and simulation are developed to analyze and compare the performance of FINCH with other protocols. The results show that FINCH can support fast and efficient link layer and intradomain handovers. The numerical results can also be used to select proper network configurations.

Multicast services have received great interests recently. They normally cannot tolerate high packet delay and high loss rate. However, multicast services may be disrupted in mobile and wireless networks. Disruption may be caused by different reasons. In this paper, we consider the disruption resulted from handoffs between base stations. Although many mobile multicast protocols have been proposed, they primarily consider the routing in mobile environment. The protocols usually do not consider how to reduce packet delay and packet loss rate caused by intermittent radio connectivity. In this paper, we propose a mobile multicast protocol which utilizes cooperative communications for intermittent connected networks. Specifically, multicast packets are cached in helpers, which in turn relay the packets to the mobile hosts disconnected from the network. Therefore, multicast services still can be delivered to the disconnected mobile hosts. Hence, packet loss rate can be reduced and throughput can be increased significantly. Most of the studies of cooperative communications focus on MAC and physical layers. We demonstrate how cooperative communications can benefit multicast at network layer. Both mathematical model and simulation are developed to analyze the performance of the proposed protocol.

Mobile virtual private network (MVPN) has been developed to secure mobile user's communication between untrusted external networks and protected private internal network. The IETF's solution, however, leads to some problems: where should we put the external home agent (HA), how could we trust the external HA, and overhead of three tunnels. In this paper, we propose an alternative SIP-based MVPN. Because the proposed architecture is based on SIP, the problems inherited from mobile IP are not problems in our architecture. In addition, there is no need to tunnel a packet three times as that in IETF MVPN. In this paper, we also propose analytical models to evaluate and compare the performance of the proposed SIP-based MVPN with the IETF MVPN. The results show that the proposed SIP-based MVPN can reduce packet delivery cost significantly. It is especially suitable for real-time applications.

WiMAX forum is developing and standardizing the end-to-end network architecture. The access service network (ASN) gateway (GW) plays a critical role in the system. How to reduce the load in the ASN GW has become an important issue. However, the standards only define the ASN GW relocation procedure without specifying when the relocation should be performed. In a real development, the key challenge to reduce the load of an ASN GW heavily relies on the decision of an appropriate time to relocate the MSs in an ASN GW. In this paper, we propose two effective ASN GW relocation algorithms. They can accurately estimate the traffic load and decide when to perform ASN GW relocation. The proposed algorithms can be accomplished by ASN GW alone. There is no need to exchange information among ASN GWs or get any help from other servers. They are fully compatible with existing systems and should be easy to implement. Extensive simulations have been performed to investigate the performance of the proposed algorithms. The results show that the proposed algorithms can increase overall throughput and reduce the loads of ASN GWs.

Because wireless channel condition is time-varying, the allocated bandwidth is usually not fixed. Therefore, it is a challenge to guarantee QoS, especially for bandwidth- consuming and delay-sensitive multimedia applications. In this paper, we propose a cross-layer mechanism to improve the quality of H.264 video when encountering short-term bandwidth fluctuations over IEEE 802.11e wireless networks. The proposed cross-layer mechanism consists of slice classification at application layer, dynamic packet selective transmission (DPST) at MAC layer, and channel condition prediction at physical layer. Performance of the proposed mechanism is evaluated through extensive simulations. Results show that the proposed cross-layer mechanism provides better video quality and lower packet delay.

This paper presents a contention adaptation (CA) mechanism to improve the energy efficiency in IEEE 802.11e EDCA. By suspending some transmissions, the proposed EDCA/CA can reduce the number of collisions. Because unnecessary retransmissions are eliminated, the energy consumption is reduced. Extensive simulations have been performed to demonstrate the performance of the proposed EDCA/CA. The results show that EDCA/CA can reduce the energy consumption significantly. It reduces frame delay as well when traffic load is heavy. When traffic load is light, the proposed EDCA/CA will slightly increase the video delay, which in general is still acceptable. Furthermore, the proposed EDCA/CA is simple and easy to implement. It is fully compatible with the 802.11e EDCA. It is both effective and practical.

This paper presents an energy conservation scheme, maximum unavailability interval (MUI), to improve the energy efficiency for the Power Saving Class of Type II in IEEE 802.16e. By applying the Chinese remainder theorem, the proposed MUI is guaranteed to find the maximum Unavailability Interval, during which the transceiver can be powered down. The proposed MUI only dynamically adjusts one parameter defined in the standard. In addition, it is fully compatible with 802.16e standard. We also propose a new technique to reduce the computational complexity when solving the Chinese remainder theorem problem. Simulation and analysis have been conducted to evaluate the performance.

In this paper, we propose a peer-to-peer service discovery protocol specially designed for mobile ad-hoc network (MANET) environment. The proposed mobile service discovery protocol (MSDP) uses a dynamic clustering algorithm to group nodes in a MANET, and utilizes distributed hash tables (DHTs) to efficiently cache service information in a peer-to-peer manner. Simulation results under different scenarios show that MSDP has steady performance and is able to reduce message overhead efficiently

There are many incompatible wireless systems. How to integrate them has become an important issue. The integration should be done in both radio access networks (RANs) and core networks. As that in reconfigurable radio, in this paper we propose a reconfigurable architecture in which different protocols can be used in core networks dynamically. More specifically, we consider reconfigurable mobility management and propose reconfigurable architecture and mobility platform (RAMP). RAMP can accommodate, control, and coordinate various types of mobility management protocols. Therefore, both network operators and users can execute different protocols dynamically. Details of the RAMP are discussed. Both analytical model and simulation are developed to analyze the signaling cost in the proposed RAMP. Results show that the RAMP architecture will not incur high signaling cost. A testbed is constructed as well. Empirical experiments are conducted to demonstrate the feasibility of the proposed idea.

Future network environment is expected to have IPv4 and IPv6 coexisted in heterogeneous networks. This paper presents a roaming mechanism called Heterogeneous Intersystem Mobility (HIM) to achieve intersystem roaming between IPv4 and IPv6 in heterogeneous wireless networks, including 3GPP, 3GPP2, and WLAN. The proposed mechanism integrates Mo- bile IPv6, Network Address Translation - Protocol Translation (NAT-PT), and 6to4 automatic tunnel. The proposed mechanism keeps the network architectures integrated into HIM unchanged. Therefore, it is suitable for other emerging wireless networks. A testbed has been constructed. A real-time multimedia application with remote control has been implemented to demonstrate that users could roam seamlessly in heterogeneous wireless networks without reestablishing the session.

In this paper, we present a scheduling algorithm for the centralized controller in the IEEE 802.11 standards. The proposed algorithm is specifically designed for the Point Coordination Function (PCF). Although many scheduling algo- rithms have been proposed, none of them could be directly applied to the PCF uplink scheduling. Most of the literature work focuses on downlink traffic, in which Access Point (AP) could easily gather necessary information, such as queue length, packet arrival rate, and packet delay, for packet scheduling. The scheduling for uplink traffic is more challenging because the information for scheduling is distributed in each wireless station. We propose Asymptotic Weighted Fair Queuing (AWFQ) to approximate Weighted Fair Queuing (WFQ) for uplink scheduling. In AWFQ, bandwidth is allocated dynamically according to channel condition. In addition, each wireless station will give up its transmission opportunity when confronting a poor channel condition. With the proposed scheme, the channel utilization is improved. The average packet delay is reduced as well. An attractive feature of the proposed algorithm is that it could be implemented with only minor modifications to the IEEE 802.11 standards.

IEEE 802.11 wireless LANs have been widely deployed. How to efficiently balance the traffic loads among access points (APs), which will lead to improved network utilization and higher quality of user experience, has become an important issue. A key challenge is how to select an AP to use during the handoff process in a way that will achieve overall load balance in the network. The conventional approaches typically use signal-to-noise ratio (SNR) as the criterion without considering the load of each AP. In this paper, we propose two effective new AP selection algorithms. These algorithms estimate the AP traffic loads by observing and estimating the IEEE 802.11 frame delays and use the results to determine which AP to use. The algorithms can be implemented in software on mobile stations alone. We will show that better performance can be achieved when the APs provide assistance in delay measurements; however, the improvement is not significant. There is no need to exchange information among APs. The proposed algorithms are fully compatible with the existing standards and systems and they are easy to implement. We will present extensive simulation results to show that the proposed algorithms can significantly increase overall system throughput and reduce average frame delay.

This paper presents the dynamic external home agent (x-HA) assignment, fast authentication, and pre-authentication in mobile virtual private networks (VPNs). The proposed architecture is based on the mobile VPN proposed by the IETF, which adopts mobile IP and IPsec. The IETF solution, however, leads to two questions: where should we put the x-HA and how should we trust the x-HA? We propose to assign the x-HA dynamically so the hand-off latency and end-to-end latency could be reduced significantly. By using diameter mobile IPv4 application, we also propose a technique such that the x-HA can be associated with the VPN securely. In addition, we also propose fast authentication and pre-authentication to further reduce hand-off delay. The proposed technique has been implemented in a mobile VPN testbed. Performance analysis based on empirical experiments is discussed.

Abstract This paper presents the dynamic external Home Agent (x‐HA) assignment in mobile Virtual Private Networks (VPNs). The proposed architecture is based on the mobile VPN proposed by the IETF, which adopts Mobile IP and IPsec. The IETF solution, however, leads to two questions: where should we put the x‐HA and how should we trust the x‐HA? We propose to assign the x‐HA dynamically so the handoff latency and end‐to‐end latency could be reduced significantly. By using Diameter Mobile IPv4 application, we also propose a technique such that the x‐HA can be associated with the VPN securely. In addition, the registrations with x‐HA and internal HA (i‐HA) are concurrently accomplished. The proposed technique has been implemented in a mobile VPN testbed. Performance analysis based on empirical experiments is discussed. Copyright © 2006 John Wiley & Sons, Ltd.

There are many incompatible wireless systems. How to integrate them has become an important issue. The integration should be done in both radio access networks (RANs) and core networks. The current trend is to integrate various RANs with an IP-based core network so users with a multi-mode handset or reconfigurable radio, such as software defined radio (SDR), could seamlessly roam among different RANs. With this all-IP paradigm, there should be one common core network, or various core networks should be compatible. Unfortunately, although both 3GPP and 3GPP2 have adopted IP in their packet-switched core networks, the architectures and protocols are not necessary compatible. In addition, they are also different from today's Internet. A user with reconfigurable radio still could not roam seamlessly among 3GPP, 3GPP2, and other IP core networks. As that in RANs, in this paper we propose a reconfigurable architecture in which users could use different protocols in core networks dynamically. There are many potential research topics for the reconfigurable core network. This paper focuses on reconfigurable mobility management. An architecture called reconfigurable architecture and mobility platform (RAMP) is proposed. Both analytical model and simulation are developed to analyze the architecture. In addition, a testbed is constructed. Empirical experiments are conducted to demonstrate the feasibility of the proposed idea

This paper presents the design and analysis of GPRS-WLAN mobility gateway (GWMG) for the integration of GPRS and wireless LANs (WLANs). The proposed architecture leverages mobile IP as the mobility management protocol over WLANs. The interworking between GPRS and WLANs is achieved by the GWMG which resides on the border of GPRS and WLAN systems. The design goal is to minimize the modifications in GPRS and WLANs as that both systems are widely available in the markets already. By deploying the GWMG, users can seamlessly roam among two systems. Both mathematical analysis and simulation are developed to analyze the performance. The proposed GWMG has also been implemented in a commercial GPRS system. The results show that the GWMG could achieve the design goal to effectively integrate GPRS and WLANs.

A mobile virtual private network (VPN) has been developed to secure a mobile user's communication between entrusted external networks and the protected private internal network. IETF's solution, however, leads to some problems: where the external HA (home agent) should be put; how to trust the external HA; the overhead of three tunnels. We propose an alternative SIP-based mobile VPN. Because the proposed architecture is based on SIP (session initiation protocol), the problems inherited from Mobile IP are not problems in our architecture. In addition, there is no need to tunnel a packet three times, as in IETF's mobile VPN. Besides, by using SRTP, cRTP, MIKEY, Diameter SIP Application, and MIDCOM ALG, the proposed architecture can also provide VPN services for mobile users effectively. The proposed technique has been implemented in a mobile VPN testbed. Empirical experiments with a VoIP application were conducted to analyze the performance in terms of bandwidth consumption, end-to-end delay, and handoff latency.

Distributed object-oriented platforms are increasingly important over wireless environments to provide frameworks for collaborative computations and for managing a large pool of distributed resources. For beyond 3G environments, distributed object-oriented platforms can provide the framework and toolkits for application developments with heterogeneous wireless environments. In this paper, we present our support for Java RMI over Bluetooth, GPRS, and WLAN environments. We propose a software mechanism which can be used to dynamically adapt RMI over different networks with optimization-related strategies. This is an important middleware for component communications. We will show how to employ Java Dynamic Proxy and exception handling techniques to help perform roaming and resource scheduling among heterogeneous wireless environments. Java Grande benchmarks are used to demonstrate that our RMI implementations over GPRS, WLAN, and Bluetooth environments are effective in supporting parallel and distributed control of Java layers over heterogeneous wireless environments.

This paper presents the design principles of dynamic service negotiation protocol (DSNP). DSNP is a protocol to negotiate the SLS (service level specification) in the IP layer. It can be used for service negotiation from host to network, network to host, and network to network. The automated negotiation makes service negotiation efficient in terms of time, cost, and correctness. The dynamic negotiation not only allows users to adapt their needs dynamically, but also lets providers utilize the network better. DSNP can be used in both wireline and wireless networks. It is, however, particularly useful in the mobile environment. To demonstrate the usefulness of DSNP, a reference wireless QoS architecture based on DiffServ is presented. Example applications and experimental results are illustrated.

This paper presents two new methods that use local information alone to predict the resource demands of and determine resource reservation levels for future handoff calls in multimedia wireless IP networks. The proposed methods model the instantaneous resource demand directly. This differs from most existing methods that derive the demands from modeling the factors that impact the demands. As a result, the proposed methods allow new and handoff calls to: (1) follow non-Poisson and/or nonstationary arrival processes; (2) have arbitrary per-call resource demands; and (3) have arbitrarily distributed call and channel holding times. The first method is based on the Wiener prediction theory and the second method is based on time series analysis. Our simulations show that they perform well even for non-Poisson and nonstationary handoff call arrivals, arbitrary per-call bandwidth demands, and nonexponentially distributed call and channel holding times. They generate closely comparable performance with an existing local method and an existing collaborative method that uses information about mobiles in neighboring cells, under assumptions for which these other methods are optimized. The proposed methods are much simpler to implement than most other existing methods with fewer capabilities.

To support fast and efficient handoffs, we propose a single protocol for both link-layer (within an IP subnet) and IP-layer (across the IP subnet) handoffs within a local domain. It is a complementary protocol to Mobile IP, in which Mobile IP deals with inter-domain mobility in the wide area. By combining a routing table in the IP layer and a bridging table in the link layer to form a single forwarding table, packets destined for a mobile terminal can be forwarded by simple table look-ups. When a mobile terminal moves, the new route can be established by table updates initiated by the mobile terminal. Compared with Mobile IP, the proposed scheme does not need IP encapsulation and does not have the triangular routing problem. In addition, the overhead and latency caused by interfacing the mobility management in the link layer and the IP layer are eliminated. Although link-layer mobility management depends on the underlying wireless technologies to a certain extent, the proposed scheme is general enough for most wireless multiple-access protocols.

There are many different types of video coding standards which can only be played with specific decoders. The lack of a decoder requires a user to download and install the proper decoder in order to decode a particular video stream. This however may not be preferable for real-time applications due to real-time constraint. We propose active techniques to dynamically inject video coding software into the transmitted video packets so that users are capable of playing video encoded in any format without having the decoding software pre-installed. The proposed techniques encapsulate the encoded video stream along with the appropriate video decoding software into active packets, and transmit the active packets to the receiving terminal. The receiver then only needs to extract the code from the active packets to get the software to decode the encoded video. The process of creating and extracting active packets is referred as active activation. Depending upon the nature of the video stream, there are different active techniques to encapsulate and restore the video stream. This paper details these active techniques.

Receiver synchronization of continuous media streams is required to deal with delay differences and variations resulting from delivery over packet networks such as the Internet. This function is commonly provided using per-stream playout buffers which introduce additional delay in order to produce a playout schedule which meets the synchronization requirements. Packets which arrive after their scheduled playout time are considered late and are discarded. In this paper, we present the Concord algorithm, which provides a delay-sensitive solution for playout buffering. It records historical information and uses it to make short-term predictions about network delay with the aim of not reacting too quickly to short-lived delay variations. This allows an application-controlled tradeoff of packet lateness against buffering delay, suitable for applications which demand low delay but can tolerate or conceal a small amount of late packets. We present a selection of results from an extensive evaluation of Concord using Internet traffic traces. We explore the use of aging techniques to improve the effectiveness of the historical information and hence, the delay predictions. The results show that Concord can produce significant reductions in buffering delay and delay variations at the expense of packet lateness values of less than 1%.

Mobile computers typically have limited energy for computing and communications due to short battery lifetimes. Encoding, decoding, and transmission of video information require significant computing and communication resources. Low power encoding and decoding schemes have been researched extensively. In this paper, we focus on processing encoded video for transmission under low battery power conditions. Such processing, while conserving battery power, attempts to reduce deterioration of video quality.

This paper describes the design and analysis of the scheduling algorithm for EC-MAC (energy conserving medium access control) (Sivalingam et al.), a low-power medium access control (MAC) protocol for wireless and mobile ATM networks. Based on the structure of EC-MAC and the characteristics of the wireless channel, we propose a new algorithm which can deal with the bursty errors and the location-dependent errors. Most scheduling algorithms proposed for either wired or wireless networks were analyzed with homogeneous traffic or multimedia services with simplified traffic models. We analyze our scheduling algorithm with more realistic multimedia traffic models. One of the key goals of the scheduling algorithm is simplicity and fast implementation. Unlike the time-stamp based algorithm, our algorithm does not need to sort the virtual time, thus reducing the complexity of the algorithm significantly.