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.     

Tiered bandwidth reservation scheme for multimedia wireless networks

It is important to provide quality of service (QoS) guarantees if we want to support multimedia applications over wireless networks. In this paper, considering the features of tiering in sectored cellular networks, we propose a novel scheme for bandwidth reservation to approach QoS provisioning. By predicting the movement of each connection, the reserving of bandwidth is only required in needful neighboring cells instead of in all neighboring cells. In addition, an admission control mechanism incorporated with bandwidth borrowing assists in distributing scarce wireless bandwidth in more adaptive way. Through mathematical analysis, we proof the advantages of tier‐based approach and the bound for the selection of tiered boundary. The simulation results also verify that our scheme can achieve superior performance than traditional schemes regarding no bandwidth reserving, fixed bandwidth reserving, and bandwidth borrowing in sectored cellular networks when performance metrics are measured in terms of the connection dropping probability (CDP), connection blocking probability (CBP), and bandwidth utilization (BU). Copyright © 2008 John Wiley & Sons, Ltd.     

CDMA网络中多媒体业务的接入控制

从码分多址(CDMA)系统的特点出发，采用多维马尔可夫过程来分析多媒体业务共存时基于干扰水平的接入控制策略，得到在小区容量可变情况下的系统性能。文中考虑到切换用户的优先级以及不同类型用户的不同QoS要求，还在系统中设置了多级接入门限，从而实现在扩大系统容量的同时，又力求保证系统已有的链路质量，实现接入控制的目的。     

Optimized bandwidth allocation in broadband wireless access networks

Towards satisfying the requirements of International Mobile Telecommunications–Advanced, both the Institute of Electrical and Electronics Engineers (IEEE) and Third Generation Partnership Project (3GPP) introduced revolutionary wireless technologies, exploiting advanced technologies and architectures. Both IEEE's 802.16 (Worldwide Interoperability for Microwave Access (WiMAX)) and 3GPP's Long Term Evolution have been introduced to accommodate the increasing demand for mobile services and applications. To realize the true potential of these technologies, however, opportunistic frameworks for radio resource management must be designed to exploit the adaptive nature of mobile traffic. The utility optimized quality‐of‐service (QoS) framework proposed in this paper for the mobile WiMAX networks achieves this objective. To maintain support for QoS guarantees, the framework capitalizes on the adaptive nature of WiMAX traffic by individually linking connections with a utility function designed to both uphold the end users’ perceived performance and determine bandwidth allocations by a search tree maximization algorithm. In doing so, bandwidth utilization is maximized for all active connections, and blocking and dropping probabilities for new and handover calls, respectively, are minimized. The framework is evaluated through an extensive simulation model and is shown to outperform state‐of‐the‐art solutions. Copyright © 2014 John Wiley & Sons, Ltd.     

Handoff performance in wireless DS‐CDMA networks

This paper analyses the performance of DS‐CDMA networks in the presence of call handoffs. We show that a handoff may violate the SINR requirements for other users, and thus cause an outage in the target cell. We propose to use the probability of such events as a possible metric for quality of service in networks with multiple traffic types, and derive the corresponding QoS parameters. A two‐level admission policy is defined: in tier 1 policy, the network capacity is calculated on the basis of the bound on outage probability. However, this policy does not suffice to prevent outage events upon handoffs for various traffic types, and henceforth, we propose an extension that reserves extra bandwidth for handoff calls, thus ensuring that handoff calls will not violate the outage probability bound. The overhead imposed by the extension is negligible, as the complete two‐tier admission control algorithm is executed only when a call is admitted into the network. Once admitted, calls can freely execute handoffs using the reserved bandwidth. The modified second‐tier bandwidth reservation policy is adaptive with respect to the traffic intensity and user's mobility and we show that it can provide satisfactory call (flow) quality during its lifetime. Analytical results for the QoS have been verified by the simulations. Copyright © 2002 John Wiley & Sons, Ltd.     

Heuristic RAT selection policy to minimize call blocking probability in next generation wireless networks

In next generation wireless network (NGWN) where multiple radio access technologies (RAT) co‐exist, a joint call admission control (JCAC) algorithm is needed to make a RAT selection decision for each arriving call. RAT selection policy has a significant effect on the overall new call blocking probability in the network. We propose a heuristic RAT selection policy to minimize new call blocking probability in NGWN. The proposed JCAC scheme measures the arrival rate of each class of calls in the heterogeneous wireless network. Based of the measured values of the arrival rates and using linear programming technique, the JCAC scheme determines the RAT selection policy that minimizes overall call blocking probability in the heterogeneous wireless network. Using Markov decision process, we develop an analytical model for the JCAC scheme, and derive new call blocking probability, handoff call dropping probability (HCDP), and call incompletion probability (CIP). Performance of the proposed scheme is compared with the performance of other JCAC scheme. Simulation results show that the proposed scheme reduces new call blocking probability, HCDP, and CIP in the heterogeneous wireless network. Copyright © 2009 John Wiley & Sons, Ltd.     

Handoff Performance Improvement with Latency Reduction in Next Generation Wireless Networks

The next generation (NG) wireless networks are expected to provide mobile users with the real-time multimedia services. High sensitivity to time constraints like delay and jitter is one of the important characteristics of the multimedia traffic. In order to maintain a certain quality of service (QoS) level, the handoff latency should be minimized. Furthermore, if the new cell is not ready at the actual handoff time, the handoff call may be even forced terminated. Hence, the handoff preparation latency directly affects the performance of the cellular networks in terms of QoS support and the handoff blocking probability. In this paper, we present the expected visitor list (EVL) method to achieve reduced handoff blocking probability and maintain a certain QoS level in the network by minimizing handoff preparation latency. The handoff signaling decomposition is introduced to make the neighbor cells aware of the resource demands and QoS requirements of the mobile terminal before the actual handoff time. The obtained information about the prospective active mobile terminal is stored in an EVL entry at the neighbor cells. The call admission control (CAC) with QoS-provisioning is run against each EVL entry. According to the CAC result, the network preparation algorithms are executed and the results are stored in the entry. No resource reservation or allocation is performed in advance, and the varying network conditions are reflected to validity and admission status of the entries. The results of handoff preparation algorithms stored in the EVL entry are activated at the actual handoff time and hence the handoff latency is minimized. Performance evaluation through mathematical analysis and extensive simulation experiments show that the EVL method reduces handoff latency and hence handoff call blocking probability significantly without introducing high overhead.Özgür B. Akan received the B.S. and M.S. degrees in electrical and electronics engineering from Bilkent University and Middle East Technical University, Ankara, Turkey, in 1999 and 2001, respectively. He received the Ph.D. degree in electrical and computer engineering from the Broadband and Wireless Networking Laboratory, School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, in 2004. He is currently an Assistant Professor with the Department of Electrical and Electronics Engineering, Middle East Technical University. His current research interests include sensor networks, next-generation wireless networks, and deep space communication networks.Buyurman Baykal received his B.Sc. (High Hons.) degree in Electrical and Electronics Engineering from Middle East Technical University in 1990; M.Sc. (Distinction) and Ph.D. degrees in 1992 and 1995 from Imperial College of Science, Technology and Medicine. Dr. Baykal has research and teaching interests in speech processing, signal processing for telecommunications, and communication networks. He has extensive experience both in the theory and applications of adaptive signal processing techniques to communication applications such as acoustic echo cancellation, noise reduction, channel equalization and digital receiver design through self-conducted research and industry-funded research projects. He conducts research and implementation work on low bit rate speech coding and content based indexing of audio signals. He is also involved in communication network research with particular interest in ATM/IP design aspects, wireless networks and network management issues. Dr. Baykal is an Associate Editor of Computer Networks (Elsevier Science), Sensor Letters (American Scientific Publishing), a past Associate Editor of the IEEE Transactions on Circuits and Systems Part II—Analog and Digital Signal Processing (TCAS-II). He authored and co-authored over 50 technical papers.     

Utility‐based probabilistic call admission control for complete fairness in wireless networks

Resource reservation or the other prioritization strategies adopted by Call Admission Control (CAC) schemes in wireless networks lead to unfair resource allocation to users belonging to different service classes (SCs) due to high divergence among the respective call blocking probabilities (CBPs). In this paper, we propose dynamic optimization of probabilistic CAC (P‐CAC) schemes to assure CAC fairness among users of different SCs in wireless networks. The approach is based on users utility combined with fairness optimization, aiming at dynamically determining the probability value in the P‐CAC scheme. This optimal probability is adjusted to network ongoing traffic, CBPs of each SC, prioritization levels characterizing the SCs supported, and the users risk aversion, which reflects their behavior toward the perceived QoS. The existence and uniqueness of the optimal probability that leads to absolute fairness among the users of a wireless network are proven. Copyright © 2012 John Wiley & Sons, Ltd.     

蜂窝无线通信网络呼叫允许控制分析

无线网络中由于用户的移动性、频谱资源的缺乏以及信道的衰落,使无线网络的服务质量的供给成为一个日益严峻的问题。呼叫允许控制(CAC)是无线资源管理中的重要组成部分,是一种保证服务质量和网络资源利用率的重要机制。总结了CAC领域的研究成果,对蜂窝无线通信网络的CAC方案进行了分析,指出了目前CAC研究中存在的问题,并探讨了今后的研究方向。     

MIMO ARIMA models for handoff resource reservation in multimedia wireless networks

This paper presents a new approach to prediction of resource demand for future handoff calls in multimedia wireless IP networks. Our approach is based on application of multi‐input‐multi‐output (MIMO) multiplicative autoregressive‐integrated‐moving average (ARIMA) (p,d,q)x(P,D,Q)_S models fitted to the traffic data measured in the considered cell itself and on the new call admission control (CAC) algorithm that simultaneously maximizes the system throughput while keeping the handoff call dropping probability (CDP) below the targeted value. The main advantages of the proposed approach are the following: first, the proposed multi‐variable prediction method gives on average better predictions (i.e. narrower prediction confidence interval) for realistic traffic situations, which results in lower new call blocking probability (CBP) at the targeted handoff CDP and second, the model is simple to implement since it does not require communication among the adjacent cells. Simulation results show the superiority of the proposed MIMO prediction approach combined with the proposed call admission control algorithm for some typical nonstationary situations in comparison with univariate models. Copyright © 2004 John Wiley & Sons, Ltd.     

Bandwidth borrowing‐based QoS approach for adaptive call admission control in multiclass traffic wireless cellular networks

This paper proposes a QoS approach for an adaptive call admission control (CAC) scheme for multiclass service wireless cellular networks. The QoS of the proposed CAC scheme is achieved through call bandwidth borrowing and call preemption techniques according to the priorities of the traffic classes, using complete sharing of the available bandwidth. The CAC scheme maintains QoS in each class to avoid performance deterioration through mechanisms for call bandwidth degradation, and call bandwidth upgrading based on min–max and max–min policies for fair resource deallocation and reallocation, respectively. The proposed adaptive CAC scheme utilizes a measurement‐based online monitoring approach of the system performance, and a prediction model to determine the amount of bandwidth to be borrowed from calls, or the amount of bandwidth to be returned to calls. The simulation‐based performance evaluation of the proposed adaptive CAC scheme shows the strength and effectiveness of our proposed scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

Call admission control scheme with normalized quality of service metric in IEEE 802.16 networks

IEEE 802.16 network introduces a multimedia data scheduling service with different quality of service (QoS) requirements. The scheduling service manages transmission resources according to data types, satisfying the requirements of different connections or users. On the basis of the data types defined in the service, we discuss a normalized QoS metric for the multimedia connections in the paper. The QoS value of a connection can be determined just by three components: the data type of the connection, its desired resources, and its allocated resources. Then, we propose an optimum bandwidth allocation solution, which can maximize the utility of base station. Next, we propose a call admission control scheme utilizing the bandwidth allocation solution. In the scheme, the occupied resource of ongoing connections will be regulated for the entry admission of a new connection, without degrading the network performance and the QoS of ongoing connections. Finally, the simulation results confirm that the proposed scheme with the normalized QoS can achieve better trade‐off between ongoing connections and new connections.Copyright © 2012 John Wiley & Sons, Ltd.     

Providing deterministic packet delays and packet losses in multimedia wireless networks

‘Anytime, anywhere’ communication, information access and processing are much cherished in modern societies because of their ability to bring flexibility, freedom and increased efficiency to individuals and organizations. Wireless communications, by providing ubiquitous and tetherless network connectivity to mobile users, are therefore bound to play a major role in the advancement of our society. Although initial proposals and implementations of wireless communications are generally focused on near‐term voice and electronic messaging applications, it is recognized that future wireless communications will have to evolve towards supporting a wider range of applications, including voice, video, data, images and connections to wired networks. This implies that future wireless networks must provide quality‐of‐service (QoS) guarantees to various multimedia applications in a wireless environment. Typical traffic in multimedia applications can be classified as either Constant‐Bit‐Rate (CBR) traffic or Variable‐Bit‐Rate (VBR) traffic. In particular, scheduling the transmission of VBR multimedia traffic streams in a wireless environment is very challenging and is still an open problem. In general, there are two ways to guarantee the QoS of VBR multimedia streams, either deterministically or statistically. In particular, most connection admission control (CAC) algorithms and medium access control (MAC) protocols that have been proposed for multimedia wireless networks only provide statistical, or soft, QoS guarantees. In this paper, we consider deterministic QoS guarantees in multimedia wireless networks. We propose a method for constructing a packet‐dropping mechanism that is based on a mathematical framework that determines how many packets can be dropped while the required QoS can still be preserved. This is achieved by employing: (1) An accurate traffic characterization of the VBR multimedia traffic streams; (2) A traffic regulator that can provide bounded packet loss and (3) A traffic scheduler that can provide bounded packet delay. The combination of traffic characterization, regulation and scheduling can provide bounded loss and delay deterministically. This is a distinction from traditional deterministic QoS schemes in which a 0% packet loss are always assumed with deterministically bounding the delay. We performed a set of performance evaluation experiments. The results will demonstrate that our proposed QoS guarantee schemes can significantly support more connections than a system, which does not allow any loss, at the same required QoS. Moreover, from our evaluation experiments, we found that the proposed algorithms are able to out‐perform scheduling algorithms adopted in state‐of‐the‐art wireless MAC protocols, for example Mobile Access Scheme Based on Contention and Reservation for ATM (MASCARA) when the worst‐case traffic is being considered. Copyright © 2002 John Wiley & Sons, Ltd.     

Quality of service control in multimedia network clusters

We introduce a control architecture in which several (independent) multimedia clusters share the same (local or metropolitan) networking resources in a controlled framework. In particular, a central entity (i.e., the Gatekeeper) harmonizes the transmission rates of the various clusters following a given sharing policy. Each cluster, in turn, adopts its own end‐to‐end rate control mechanism to meet the Gatekeeper's transmission rate indications. A testbed has been developed and the system has been evaluated with real experiments by using different types of transmission sources. A software architecture is also introduced and described, with particular reference to the middleware framework realized with the Jini system. Copyright © 2003 John Wiley & Sons, Ltd.     

融合的蜂窝网络/无线局域网中资源管理的性能分析

Wireless Local Area Network (WLAN) with high data bit rates can be used with cellular network to achieve higher level of Quality of Service (QoS) by sharing their total resources efficiently. The integration between cellular and WLAN networks should be ensured considering different channel allocation strategies of both networks and efficient resource management techniques should be developed. In this paper, we propose a new call admission scheme to use the coupled resource effectively. The proposed scheme, by taking the different resource sharing strategies for two access networks, limits the new, horizontal and vertical handoff voice and data call arrivals with respect to their call level QoS requirements. Numerical results show that the proposed integrated cellular/WLAN network model uses the resources more effectively and achieves all upper bound QoS requirements for voice and data users as compared with the non integrated network model.     

多媒体无线网中QoS降级的公平性研究

对无线，移动多媒体网中多服务类、多优先级的适应多媒体应用QoS降级的公平性问题进行了研究。提出降级因子加权平方和最小的降级原则，不但考虑了类间和类内优先级，而且考虑了用户的QoS降级深度。接着，证明对离散型适应多媒体应用，降级因子加权平方和最小的降级原则满足广义的按比例公平性，而对连续型适应多媒体应用，满足按比例公平性。最后，用量子遗传算法对所给问题进行了求解，结果进一步验证了所提算法的有效性。     

无线移动网中呼叫接纳控制模型分析

新一代无线网应该能够同时支持传统的数据业务和实时交互式多媒体业务，并能够为用户提供QoS保证。在无线网中提供QoS保证，呼叫接纳控制扮演着重要的角色。对已有的呼叫接纳控制方面的研究成果进行了归纳、总结和分析，以期得出适合于无线移动多媒体网络的呼叫接纳控制模型。为适应当前的多媒体应用，侧重于对和适应性带宽分配相结合的接纳控制模型的分析。另外，介绍了与价格机制相结合的接纳控制模型，经济学概念的引入，为我们解决问题提供了一种新的视角。     

无线/移动网络中自适应的接纳控制算法及性能分析

无线／移动网络中重要的连接级QoS性能指标包括新连接请求阻塞率(CBP)、切换连接请求丢弃率(HDP)等。其中，更不希望因切换连接请求的丢弃而导致服务的终止。为降低HDP，通常采用资源预留方案。但这种方案导致CBP较高、资源利用率低。本文针对自适应的多媒体应用带宽可以动态调整的特点，研究无线／移动网络中多优先级服务自适应的接纳控制机制，提出一个自适应的接纳控制算法，对其QoS性能进行分析。     

基于蚁群优化的无线多媒体传感器网络区分服务路由

无线多媒体传感器网络中存在多种类型的数据,而且这些数据的服务质量需求并不相同。针对这种情况,提出一种基于蚁群优化的区分服务路由协议（DSACO, differentiated service and ant colony optimization based routing protocol）。DSACO在网络分层的基础上通过限制蚂蚁的搜索范围以减少建立路由的时间和能量消耗,对不同服务质量需求的数据采用区分服务路由以满足不同类型数据的服务质量需求。仿真结果表明,新协议能够为多媒体数据的传输提供更好的QoS保障,在数据传输的平均时延、分组丢失率和能量消耗上优于已有路由协议。     

Adaptive call admission control in 3GPP LTE networks

In this article, we propose new methods to reduce the handoff blocking probability in the 3rd Generation Partnership Project Long Term Evolution wireless networks. This reduction is based on an adaptive call admission control scheme that provides QoS guarantees and gives the priority of handoff call over new call in admission. The performance results of the proposed schemes are compared with other competing methods using simulation analysis. Simulation results show the major impact on the performance of the 3rd Generation Partnership Project Long Term Evolution network, which is reflected in increased resource utilization ratio to (99%) and in the ability in satisfying the requirements of QoS in terms of call blocking probability (less than 0.0628 for Voice over IP service) and dropping probability rate (less than 0.0558).Copyright © 2012 John Wiley & Sons, Ltd.