Enabling seamless multimedia wireless access through QoS‐based bandwidth adaptation

Effective support of real‐time multimedia applications in wireless access networks, viz. cellular networks and wireless LANs, requires a dynamic bandwidth adaptation framework where the bandwidth of an ongoing call is continuously monitored and adjusted. Since bandwidth is a scarce resource in wireless networking, it needs to be carefully allocated amidst competing connections with different Quality of Service (QoS) requirements. In this paper, we propose a new framework called QoS‐adaptive multimedia wireless access (QoS‐AMWA) for supporting heterogeneous traffic with different QoS requirements in wireless cellular networks. The QoS‐AMWA framework combines the following components: (i) a threshold‐based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes between different classes of handoff calls by assigning a threshold to each class, (ii) an efficient threshold‐type connection admission control algorithm, and (iii) a bandwidth adaptation algorithm that dynamically adjusts the bandwidth of an ongoing multimedia call to minimize the number of calls receiving lower bandwidth than the requested. The framework can be modeled as a multi‐dimensional Markov chain, and therefore, a product‐form solution is provided. The QoS metrics—new call blocking probability (NCBP), handoff call dropping probability (HCDB), and degradation probability (DP)—are derived. The analytical results are supported by simulation and show that this work improves the service quality by minimizing the handoff call dropping probability and maintaining the bandwidth utilization efficiently. Copyright © 2006 John Wiley & Sons, Ltd.     

Handoff algorithms in dynamic spreading WCDMA system supporting multimedia traffic

The undergoing third-generation wireless network needs to support the integration of voice and multimedia data services with varying quality-of-service (QoS) requirements. It is critical that the least bit-error rate (BER) for voice traffic, World Wide Web (WWW) traffic, and streaming video traffic be guaranteed at all time. In this paper, we discussed the integration of soft handoff and dynamic spreading factor in wideband code-division multiple-access system in supporting multimedia traffic. The contribution of our work is twofold. First, the processing time of the handoff request is analyzed. We found that intensive mobile handoff might consume significant amount of access channel time and increase the delay of handoff. We, therefore, proposed a batch mechanism such that multiple handoff requests could be processed simultaneously. The average delay is reduced from 1.12 s to 800 ms at heavy handoff rate. Our second contribution is a new resource allocation algorithm, where the spreading factor and transmission power for the handoff mobiles are jointly considered to maximize the throughput. The BER requirements for the handoff mobiles and the target cell are maintained during the handoff process. The original problem is formulated into a nonlinear programming format. We proposed a procedure to simplify it into a linear constraint problem, which is solved by a revised simplex method. Numerical results show a 25% increase in throughput for WWW traffic and a 26% improvement for the video traffic.     

Feedback Closed-Loop Scheduling Discipline for QoS Guarantee in Mobile Applications

Multi-functional and high-quality services are indispensable for providing responsive information services in a highly interactive e-learning system. This work presents a problem-solving mechanism using closed-loop scheduling discipline to achieve QoS e-learning applications. In the closed-loop schedule, the feedback mechanism supports wireless mobile communications services with dynamic QoS requirements. This work presents a closed-loop architecture by cascading the open-loop schedule, the QoS probe, the Proportional-Integral-Derivative (PID) controller and the feedback mechanism. In this architecture, the relationship between input and output is defined using a Lagrange λ-calculus module. The module estimates the future QoS according to the current scheduling, while the controller parameters are tuned according to the system status to achieve dynamic scheduling. Simulation results with e-learning activities demonstrate that the closed-loop schedule outperforms existing disciplines in terms of service delay and system utilization. Jiann-Liang Chen was born in Taiwan on December 15, 1963. He received the Ph.D. degree in Electrical Engineering from National Taiwan University, Taipei, Taiwan in 1989. Since August 1997, he has been with the Department of Computer Science and Information Engineering of National Dong Hwa University, where he is a professor now. His current research interests are directed at Wireless Sensor Networks, Cellular Mobility Management and Personal Communication Systems. Nong-Kun Chen received MS degree in Computer Science and Information Engineering, from the National Dong Hwa University, Hualien, Taiwan, in 2000. He is currently a doctoral student in the Department of Computer Science and Information Engineering at the National Dong Hwa University. His main research focuses on the areas of mobile cellular networks and feedback control.     

<Emphasis Type="Italic">DSMeM Streaming</Emphasis>: distributed system to mitigate the effects of performance anomaly and user mobility on <Emphasis Type="Italic">IEEE 802.11 WLAN</Emphasis>s

On IEEE 802.11 wireless LANs (WLAN) the clients have control over the handoff procedure; a client decides the best AP (access point) to be associated to and when and where to change its association to a new AP. This simple handoff management technique can have negative effects for both static and mobile clients of the same cell, since some wireless clients remain associated with their current AP even when a better AP is reachable. Combined with handoff latencies, this mobility method can have a negative effect on various services with severe restrictions regarding delivery rate and delay. In this paper, a distributed and transparent system that monitors channel conditions, manages user data based on its knowledge and induces client handoffs when a better AP is reachable, is presented. One of the strongest points of the proposed solution is that it can work in currently deployed IEEE 802.11 WLANs without the server, clients or APs having to introduce new software.     

SIP-based vertical handoff between WWANs and WLANs

Future-generation wireless networks have been envisioned as the integration of various wireless access networks, including both wireless wide area networks and wireless local area networks. In such a heterogeneous network environment, seamless mobility support is the basis of providing uninterrupted wireless services to mobile users roaming between various wireless access networks. Because of transparency to lower-layer characteristics, ease of deployment, and greater scalability, the application-layer-based session initiation protocol has been considered the right candidate for handling mobility in heterogeneous wireless networks. However, SIP entails application-layer transport and processing of messages, which may introduce considerable delay. As a case study of the performance of mobility management protocols in the heterogeneous wireless networks, we analyze the delay associated with vertical handoff using SIP in the WLAN-UMTS internetwork. Analytical results show that WLAN-to-UMTS handoff incurs unacceptable delay for supporting real-time multimedia services, and is mainly due to transmission of SIP signaling messages over erroneous and bandwidth-limited wireless links. On the other hand, UMTS-to-WLAN handoff experiences much less delay, mainly contributed by the processing delay of signaling messages at the WLAN gateways and servers. While the former case requires the deployment of soft handoff techniques to reduce the delay, faster servers and more efficient host configuration mechanisms can do the job in the latter case.     

MCIP: A 3G/IP Interworking System Supporting Inter-Cluster Soft Handoff

In this paper, a novel 3-tier Mobile Cellular IP (MCIP) access network is proposed for interworking between a third generation (3G) wireless cellular system and a wireline Internet Protocol (IP) based network. An inter-cluster hard handoff scheme and an inter-cluster soft handoff scheme are proposed, based on the 3-tier MCIP system model, the core network protocol stacks, and the underlying MCIP routing algorithm. The core network protocol stack is presented to integrate the 3G radio interface and the IP-based core network, and to provide the access network with capability to support soft handoff macroscopic space diversity. The MCIP hard and soft handoff schemes are compared with the hard handoff schemes used in the Cellular IP and HAWAII access networks. The MCIP access network is more efficient in terms of signaling cost, but has the same scalability as Cellular IP and HAWAII. Both MCIP hard and soft handoff schemes enable IP packets to be delivered within the MCIP access network in-order without loss and duplication, a highly desired attribute for real-time multimedia applications. The advantages of supporting soft handoffs and quality-of-service (QoS) provisioning for real-time services are achieved at slightly increased system complexity.This work was supported by a research grant from the Natural Science and Engineering Research Council (NSERC) of Canada. The authors wish to thank the anonymous reviewers for their helpful comments and suggestions which improve the presentation of this paper. Xin Liu received his B.E. and M.E. degrees in radio engineering from Harbin Institute of Technology (China), in 1990 and 1993, respectively, and his M.A.Sc degree in electrical engineering from the University of Waterloo in 2002. He joined Research In Motion in 2002 as a firmware developer. His current work involves GSM/GPRS and WCDMA firmware development. Weihua Zhuang received the B.Sc. and M.Sc. degrees from Dalian Maritime University (China) and the Ph.D. degree from the University of New Brunswick (Canada), all in electrical engineering. Since October 1993, she has been with the Department of Electrical and Computer Engineering, University of Waterloo, Canada, where she is a full professor. She is a co-author of the textbook Wireless Communications and Networking (Prentice Hall, 2003). Her current research interests include multimedia wireless communications, wireless networks, and radio positioning. Dr. Zhuang received the Premier's Research Excellence Award (PREA) in 2001 from the Ontario Government for demonstrated excellence of scientific and academic contributions. She is an Editor of IEEE Transactions on Wireless Communications, an Associate Editor of IEEE Transactions on Vehicular Technology, and an Editor of EURASIP Journal on Wireless Communications and Networking.     

Mobility protocols and RSVP performance in wireless IPv6 networks: shortcomings and solutions

Resource reservation protocol (RSVP) is a network‐control protocol used to guarantee Quality‐of‐Service (QoS) requirements for real‐time applications such as Voice‐over‐IP (VoIP) or Video‐over‐IP (VIP). However, RSVP was designed for end‐systems whose IP addresses do not change. Once mobility of an end‐system is allowed, the dynamically changing mobile IP address inevitably impacts on RSVP performance. Our study aims to first quantify the significance of this impact, and then propose a modified RSVP mechanism that provides improved performance during handoffs. Our simulations reveal that the deployment of standard RSVP over Mobile IPv6 (MIPv6) does not yield a satisfactory result, particularly in the case of VIP traffic. Fast Handovers for Mobile IPv6 (FMIPv6) was found to be providing the best performance in all tested scenarios, followed by Hierarchical Mobile IPv6 (HMIPv6) with a single exception: during low handoff rates with VoIP traffic, MIPv6 outperformed HMIPv6. We then designed a new RSVP mechanism, and tested it against standard RSVP. We found that the proposed approach provides a significant improvement of 54.1% in the Total Interruption in QoS (TI_QoS) when deployed over a MIPv6 wireless network. For HMIPv6, performance depended primarily on the number of hierarchical levels in the network, with no improvement in TI_QoS for single‐level hierarchy and up to 37% for a 5‐level hierarchy. FMIPv6 on the other hand, provided no room for improvement due to pre‐handoff signaling and the tunneling mechanism used to ensure a mobile node (MN)'s connectivity during a handoff, regardless of the RSVP mechanism used. Copyright © 2007 John Wiley & Sons, Ltd.     

DiffServ resource allocation for fast handoff in wireless mobileInternet

The next-generation wireless networks are evolving toward a versatile IP-based network that can provide various real-time multimedia services to mobile users. Two major challenges in establishing such a wireless mobile Internet are support of fast handoff and provision of quality of service (QoS) over IP-based wireless access networks. In this article, a DiffServ resource allocation architecture is proposed for the evolving wireless mobile Internet. The registration-domain-based scheme supports fast handoff by significantly reducing mobility management signaling. The registration domain is integrated with the DiffServ mechanism and provisions QoS guarantee for each service class by domain-based admission control. Furthermore, an adaptive assured service is presented for the stream class of traffic, where resource allocation is adjusted according to the network condition in order to minimize handoff call dropping and new call blocking probabilities     

An Efficient Algorithm for Fast Handoff in Wireless Mobile Networks

Mobile handoff is a relatively significant charters-tic that involves the quality of connections (QoC) between the base stations (BS) and mobile hosts (MH). Maintaining the QoC in IEEE 802.11 networks is an important challenge in wireless mobile networks, and conjointly the necessity for the different real-life wireless mobile applications. To take care of the QoC, these wireless mobile applications is responsible for fast handoffs between BS. Most of the current research is based on a neighbor graph and maintaining the neighbor table by the connected access point and calculates the scan delay. This paper has proposed a novel neighboring approach for fast handoff where scan delay has been reduced to zero by exploiting the MH neighbor table. The result shows that the proposed approach is better than state-of-the-art approaches in terms of scan delay and re-association delay.

     

IPv6-based dynamic coordinated call admission control mechanism over integrated wireless networks

Many wireless access systems have been developed recently to support users mobility and ubiquitous communication. Nevertheless, these systems always work independently and cannot simultaneously serve users properly. In this paper, we aim to integrate IPv6-based wireless access systems and propose a coordinated call admission control mechanism to utilize the total bandwidth of these systems to minimize the call blocking probabilities, especially the handoff call dropping probabilities. First, we propose an integrated hierarchical wireless architecture over IPv6-based networks to combine the wireless access systems including cellular systems (second-generation, General Packet Radio Service, or third-generation), IEEE 802.11 a/b/g WLAN, and Bluetooth. In the proposed architecture, mobile user can request a call with quality-of-service (QoS) requirements by any wireless network interfaces that can be accessed. When the proposed coordinated call admission control (CCAC) mechanism receives a request, it takes the QoS requirements of the incoming call and the available and reserved bandwidth of this wireless system into consideration to accept or reject this request. Besides, the mechanism can coordinate with other wireless systems dynamically to adjust the bandwidth reserved for handoff calls at each wireless system in this architecture so as to reduce the call blocking probabilities. Once the call is admitted, the mobile user is able to access heterogeneous wireless access networks via multiple interfaces simultaneously. Finally, we evaluate this system to show that the CCAC on the proposed architecture outperforms other mechanisms proposed before.     

快速IP切换在无线局域网中的实现

在移动网络中,无缝切换是提供QoS的基础,也是支持实时业务应用(如视频点播和语音传输等)的保证。针对无线局域网(WLAN)的节点切换问题,建立了各种网络模型,提出了链路层、网络层和传输层的解决方案。文章根据切换过程的技术特征,研究了WLAN中网络层切换的各种方案,包括移动IP方案、TAP-DANCE方案以及网络辅助的IP移动支持,具体分析了上述方案的实现过程,比较了性能指标,指出了存在的问题及进一步研究方向。     

A survey of Mobile IP in cellular and Mobile Ad-Hoc Network environments

The Internet has become ubiquitous and there has been tremendous growth in wireless communications in recent years. Many wireless communication techniques are commercially available, such as the Wireless LAN, Bluetooth, GSM, GPRS and CDMA. Because an all-IP network will be a trend, access to the Internet via wireless communication devices has become an important issue.To reduce power consumption and reuse the limited radio spectrum resources, a cellular network was formed. Cell size is one of the factors in the channel reuse rate. Basically, the channel reuse rate in a smaller cell size is higher than the channel reuse rate in a bigger cell size. Micro-mobility is therefore the inevitable direction for future mobile systems. Frequent and fast movements usually characterize micro-mobility. A cellular architecture would then present a challenge to the frequent handover procedures for a smaller cell size would usually induce a higher handoff frequency.In addition to cellular networks, the ad-hoc network is another network architecture for wireless networks. The ad-hoc network is a non-infrastructure architecture; in which nodes can access services from one another regardless where they are. An excellent routing protocol is crucial for an ad-hoc networking to function at high performance. The main difference between a cellular environment and ad-hoc network is that the ad-hoc method has no fixed infrastructure, allowing nodes to communicate with one another at any time and anywhere.We have mentioned that micro-mobility in a cellular environment would introduce a greater number of handoffs than before. The handoff probability drives the mobile IP mechanism due to signal changes. Using the Mobile IP mechanism, handoff breaking would take place within a micro-mobility environment. Therefore, in this paper, some handoff strategies that take the advantage of the ad-hoc mechanism to improve the handoff performance are investigated.     

IEEE 802.11 handoff latency improvement using Fuzzy Logic

Multimedia transmissions are delay‐sensitive Internet applications. Because mobile stations are in continual motion, handoff processes are necessary and unavoidable in wireless network environments. Because handoff processes tend to break the communication link, the research has been conducted on reducing the break time and arrival delay during Internet multimedia applications. In this paper, we propose an approach based on Fuzzy Logic to evaluate the average variation in signal strength received by a mobile station and produce a FitAP factor. This factor indicates the possible handoff access point that is suitable for the mobile station. According to the FitAP factor, a mobile station needs only to execute an active scan process once. Therefore, smaller handoff latency is expected. We compare the results from the current cell search scheme with that of the Fuzzy Logic approach. The statistical results show that the proposed method outperforms the current cell search scheme with an improved handoff latency performance. Copyright © 2007 John Wiley & Sons, Ltd.     

基于动态信道预约的自适应QoS切换算法

未来无线网络将为固定和移动用户提供多媒体通信和计算业务．为移动用户提供无线多媒体业务的一个最关键的挑战是保证端到端连接的业务质量．通过重复使用无线频谱的微蜂窝或微微蜂窝结构是一个有前途的改善移动多媒体网络容量的方式．但切换次数随着蜂窝大小的降低而增加．移动多媒体网络的一个至关重要的问题是需要可以满足各种QoS需要且有更高资源利用率的有效切换方式．该文提出了一种称为基于动态信道预约的自适应QoS切换算法,并与其它切换方式进行了性能比较．     

Adaptive QoS scheduling in wireless cellular networks

Quality of service (QoS) has been always controversial in resource shared networks. Scheduling as a packet prioritizing mechanism at Data Link Layer (DLL) contributes to QoS guarantee provisioning significantly. In this paper, a novel packet scheduler is developed in wireless cellular networks. The proposed scheme provides QoS-guaranteed service for the applications running on the sensor nodes in all the three aspects of QoS, i.e. data rate, packet loss and packet delay with regard to jitter simultaneously. We establish a three-dimensional space with certain basis vectors for QoS and introduce the efficient point of performance in terms of QoS provisioning in that space. Then we develop a generalized metric, the QoS-deviation, which is the Euclidean distance between the QoS work point of flows and the QoS efficient point in the proposed space. Based on this metric, a novel scheduling approach, namely AQDC, is designed which makes it possible to tune the trade-off between QoS provisioning and throughput optimization in an adaptive manner depending on the current Cell QoS-deviation level (CDL). Furthermore, we also develop another scheduler, namely ARTC, which is the residual-time version of the AQDC scheduler. Finally, a QoS-deviation-based CAC policy will be introduced which can be applied to all schedulers without any consideration about their structure and can be employed in cellular packet switched networks.     

Seamless SIP-based mobility for multimedia applications

Application-level protocol abstraction is required to support seamless mobility in next-generation heterogeneous wireless networks. Session initiation protocol (SIP) provides the required abstraction for mobility support for multimedia applications in such networks. However, the handoff procedure with SIP suffers from undesirable delay and hence packet loss in some cases, which is detrimental to applications like voice over IP (VoIP) or streaming video that demand stringent quality of service (QoS) requirements. In this article we present a SIP-based architecture that supports soft handoff for IP-centric wireless networks. Soft handoff ensures that there is no packet loss and that the end-to-end delay jitter is kept under control.     

Pre-scan based fast handoff scheme for enterprise IEEE 802.11 networks

In IEEE 802.11 networks, many access points (APs) are required to cover a large area due to the limited coverage range of APs, and frequent handoffs may occur while a station (STA) is moving in an area covered by several APs. However, traditional handoff mechanisms employed at STAs introduce a few hundred milliseconds delay, which is far longer than what can be tolerated by some multimedia streams such as voice over Internet protocol (VoIP), it is a challenging issue for supporting seamless handoff service in IEEE 802.11 networks. In this paper, we propose a pre-scan based fast handoff scheme within an IEEE 802.11 enterprise wireless local area network (EWLAN) environment. The proposed scheme can help STA obtain the best alternative AP in advance after the pre-scan process, and when the handoff is actually triggered, STA can perform the authentication and reassociation process toward the alternative AP directly. Furthermore, we adopt Kalman filter to minimize the fluctuation of received signal strength (RSS), thus reducing the unnecessary pre-scan process and handoffs. We performed simulations to evaluate performance, and the simulation results show that the proposed scheme can effectively reduce the handoff delay.     

A constrained MDP-based vertical handoff decision algorithm for 4G heterogeneous wireless networks

The 4th generation wireless communication systems aim to provide users with the convenience of seamless roaming among heterogeneous wireless access networks. To achieve this goal, the support of vertical handoff is important in mobility management. This paper focuses on the vertical handoff decision algorithm, which determines the criteria under which vertical handoff should be performed. The problem is formulated as a constrained Markov decision process. The objective is to maximize the expected total reward of a connection subject to the expected total access cost constraint. In our model, a benefit function is used to assess the quality of the connection, and a penalty function is used to model the signaling incurred and call dropping. The user’s velocity and location information are also considered when making handoff decisions. The policy iteration and Q-learning algorithms are employed to determine the optimal policy. Structural results on the optimal vertical handoff policy are derived by using the concept of supermodularity. We show that the optimal policy is a threshold policy in bandwidth, delay, and velocity. Numerical results show that our proposed vertical handoff decision algorithm outperforms other decision schemes in a wide range of conditions such as variations on connection duration, user’s velocity, user’s budget, traffic type, signaling cost, and monetary access cost.     

Two-level protection and guarantee for multimedia traffic in IEEE 802.11e distributed WLANs

In order to support multimedia applications such as voice and video over the wireless medium, a contention-based channel access function, called Enhanced Distributed Channel Access (EDCA), has been developed in the emerging standard IEEE 802.11e. In the EDCA, differentiated channel access is provided for different traffic classes. In this paper, we propose a two-level protection and guarantee mechanism for voice and video traffic in the EDCA-based distributed wireless LANs. In the first-level protection, the existing voice and video flows are protected from the new and other existing voice and video flows via a distributed admission control with tried-and-known and early-protection enhancements. In the second-level protection, the voice and video flows are protected from the best-effort data traffic by adopting frame-based and limit-based data control mechanisms. Performance evaluations are conducted in terms of throughput, delay, transmission limit, number of collisions, and throughput square relative difference. Extensive simulation results demonstrate that the proposed two-level protection and guarantee mechanism is very effective in terms of the protection and guarantee of existing voice and video flows as well as the utilization of the channel capacity. An early version of this paper was presented at IEEE INFOCOM 2004.     

Low-latency mobile IP handoff for infrastructure-mode wireless LANs

The increasing popularity of IEEE 802.11-based wireless local area networks (LANs) lends them credibility as a viable alternative to third-generation (3G) wireless technologies. Even though wireless LANs support much higher channel bandwidth than 3G networks, their network-layer handoff latency is still too high to be usable for interactive multimedia applications such as voice over IP or video streaming. Specifically, the peculiarities of commercially available IEEE 802.11b wireless LAN hardware prevent existing mobile Internet protocol (IP) implementations from achieving subsecond Mobile IP handoff latency when the wireless LANs are operating in the infrastructure mode, which is also the prevailing operating mode used in most deployed IEEE 802.11b LANs. In this paper, we propose a low-latency mobile IP handoff scheme that can reduce the handoff latency of infrastructure-mode wireless LANs to less than 100 ms, the fastest known handoff performance for such networks. The proposed scheme overcomes the inability of mobility software to sense the signal strengths of multiple-access points when operating in an infrastructure-mode wireless LAN. It expedites link-layer handoff detection and speeds up network-layer handoff by replaying cached foreign agent advertisements. The proposed scheme strictly adheres to the mobile IP standard specification, and does not require any modifications to existing mobile IP implementations. That is, the proposed mechanism is completely transparent to the existing mobile IP software installed on mobile nodes and wired nodes. As a demonstration of this technology, we show how this low-latency handoff scheme together with a wireless LAN bandwidth guarantee mechanism supports undisrupted playback of remote video streams on mobile stations that are traveling across wireless LAN segments.