Call admission control for non‐geostationary orbit satellite networks and other capacity‐varying networks

Many networks, such as non‐geostationary orbit satellite (NGOS) networks and networks providing multi‐priority service using advance reservations, have capacities which vary over time for some or all types of calls carried on these networks. For connection‐oriented networks, call admission control (CAC) policies which only use current capacity information may lead to excessive and intolerable dropping of admitted calls whenever the network capacity decreases. Thus novel CAC policies are required for these networks. We present the admission limit curve (ALC) and prove it is a constraint limiting the conditions under which any causal CAC policy may admit calls and still meet call dropping guarantees on an individual call basis. The ALC also leads to a lower bound on the call blocking performance achievable by any causal CAC policy which provides dropping guarantees to individual calls. Also, we introduce a new CAC policy which uses knowledge of future capacity changes to provide dropping guarantees on an individual call basis and which achieves blocking performance close to the lower bound. Copyright © 2000 John Wiley & Sons, Ltd.     

Call admission control scheme for real-time services in packet-switched OFDM wireless networks

A call admission control scheme is proposed for real-time services in packet-switched orthogonal frequency division multiplexing （OFDM） wireless cellular networks. The main idea of the proposed scheme is to use maximum acceptance ratio to maintain maximum channel utilization for real-time services according to the desired packet-level and call- level quality-of-service （QoS） requirements. The acceptance ratio is periodically adjusted by using a time discrete Markov chain and Wiener prediction theory according to the varying traffic load. Extensive simulation results show that this algorithm maintains high channel utilization, even as it guarantees packet-level and call-level QoS requirements for real-time services.     

无线移动通信系统中的呼叫接入控制

呼叫接入控制是无线移动通信系统中无线资源管理的重要部分,它直接关系到系统中用户服务质量是否能够得到保证,同时呼叫接入控制算法的有效性决定了系统资源的利用效率。文中综述了各种呼叫接入控制算法及其特点,并指出在无线移动通信系统中它们的重要性。     

A call admission control strategy for multiservice wireless cellular packet networks

A simple connection control system for multiservice cellular wireless networks is presented. Mobile stations are classified depending on the traffic they generate (e.g., voice, data). Within each class, two subclasses are also identified: stations which have originated inside the cell and stations which come from adjacent cells. The connection control mechanism is carried out by considering a number of priorities among the various classes and their subclasses. It works on two levels: static and dynamic. The static level looks at packet-level quality of service (QoS), such as cell loss and delay, while the dynamic level takes care of connection dynamics and allows the load of the system to be driven with respect to the various subclasses. Results that illustrate the performance of this control mechanism are presented.     

A Prioritized Real-Time Wireless Call Degradation Framework for Optimal Call Mix Selection

This paper describes a framework for selecting the optimal call mix to be admitted while employing a bandwidth degradation policy in a wireless cellular network. The optimal property is achieved by maximizing the revenue generated by different calls in a cell for the service provider. By degradation, we mean that: (1) some channels can be taken away from ongoing calls that are assigned multiple channels, and/or (2) newly admitted calls that require multiple channels get fewer than what they requested. To avoid removing more channels from calls than they could tolerate, we incorporate a new call attribute: the degradation tolerance, i.e., the number of channels a call can be degraded without sacrificing the acceptable level of quality. We also consider priorities over calls to influence the admission and/or degradation decision. Our analytical framework includes both static and dynamic scenarios. The dynamic case is enhanced with the ability to select the optimal call mix using incoming and departing handoffs, new calls, and call terminations in a recursive way, thus, resulting in a call admission policy. We also discuss how to accommodate non-real-time calls into our system. To evaluate the performance of the proposed scheme, a discrete event simulation tool has been developed that models our dynamic framework built on a customized simulated annealing optimization function. Simulation results demonstrate that not only does the proposed degradation framework maximize the total revenue generated by the admitted calls in the cells, but also reduce the handoff and new call blocking probabilities.     

LEO卫星通信系统的呼叫接入性能分析

在均匀业务模型的基础上,根据LEO卫星通信系统自身特点,提出了一种简单有效的呼叫接入控制策略,这种策略能在非均匀业务下较好地工作,此时系统新呼叫阻塞率和切换呼叫失败率能达到更好的平衡。在分析随机接入（RANDOM）算法和预留保护信道（GC）算法的基础上,进行了计算机仿真,并给出了相应的仿真结果。     

网络收益最大化的异构无线网络呼叫接纳控制

为有效降低异构无线网络拥塞,提高网络收益,提出了网络收益最大化的呼叫接纳控制(Call Admission Control,CAC)算法。首先模拟异构无线网络场景,考虑网络带宽及时延参数,定义网络收益函数,其次解决网络收益最优化问题。仿真结果显示,该算法可以高效地降低网络拥塞,均衡负载并提高网络收益。     

A Dynamic Reservation-Based Call Admission Control Algorithm for Wireless Networks Using the Concept of Influence Curve

In this paper a dynamic channel reservation and call admission control scheme is proposed to provide QoS guarantees in a mobile wireless network using the concept of influence curve. The basic idea behind the proposed scheme is that a moving user, in addition to its requirements in the current cell, exerts some influence on the channel allocation in neighboring cells. Such an influence is related to the moving pattern of the users and is calculated statistically. Furthermore we developed a general analytical model to calculate the corresponding blocking probabilities for wireless networks with multiple platforms, which removes the commonly used assumption that new calls and handoff calls have same channel holding time. The numerical results demonstrate that our scheme outperforms traditional channel reservation schemes and can effectively adapt to the real time network conditions.     

Call Admission Policies Based on Calculated Power Control Setpoints in SIR-Based Power-Controlled DS-CDMA Cellular Networks

In this paper, we develop call admission control algorithms for SIR-based power-controlled DS-CDMA cellular networks. We consider networks that handle both voice and data services. When a new call (or a handoff call) arrives at a base station requesting for admission, our algorithms will calculate the desired power control setpoints for the new call and all existing calls. We will provide necessary and sufficient conditions under which the power control algorithm will have a feasible solution. These conditions are obtained through deriving the inverse of the matrix used in the calculation of power control setpoints. If there is no feasible solution to power control or if the desired power levels to be received at the base station for some calls are larger than the maximum allowable power limits, the admission request will be rejected. Otherwise, the admission request will be granted. When higher priority is desired for handoff calls, we will allow different thresholds (i.e., different maximum allowable power limits) for new calls and handoff calls. We will develop an adaptive algorithm that adjusts these thresholds in real-time as environment changes. The performance of our algorithms will be shown through computer simulation and compared with existing algorithms.     

多业务移动通信系统中的呼叫接入控制

在多业务无线移动通信系统的呼叫接入控制中,不仅要考虑业务之间的优先级,同时也必须考虑切换呼叫的优先级。本文结合可移动边界算法和保护信道策略,提出了一种有效的多业务呼叫接入控制算法。为了方便地分析方案的性能,设计了一个二维的Markov链对方案的性能进行理论上的分析。通过数值分析结果表明,提出的算法同时保证了两种优先级,并提高了系统的性能。1     

Distributed Contention-Aware Call Admission Control for IEEE 802.11 Multi-Radio Multi-Rate Multi-Channel Wireless Mesh Networks

In this paper, we focus on call admission control (CAC) in IEEE 802.11 multi-radio multi-rate multi-channel (MR²-MC) wireless mesh networks (WMNs). CAC is the key component of QoS routing protocols. The goal of CAC is to protect existing flows from QoS violations and fully utilize available radio resource on channels. We propose a CAC mechanism, called Contention-Aware Multi-channel Call Admission Control (CMC), for MR²-MC WMNs based on IEEE 802.11 DCF. CMC is fully distributed, relies on local information to estimate the residual bandwidth of a path, and can be integrated into existing routing protocols for MR²-MC WMNs to provide QoS. We evaluate the performance of CMC via ns-2 simulations. The results show that CMC can precisely predict the end-to-end residual bandwidths of paths, successfully protects existing flows from QoS violations, and fully utilizes the bandwidths on channels.     

ATM基于神经模糊算法的呼叫接入控制

本文研究 ＡＴＭ通信网络基于在线测量的呼叫允许接入控制问题。文章提出利用神经－模糊算法在线协调模糊规则中的参数，并在此基础上，实现了一种新的ＣＡＣ机制。在确保服务质量的情况下，提高网络资源利用率，通过实例仿真表明了应用此种算法的可行性。     

Call Level QoS Performance under Variable User Mobilities in Wireless Networks

The concept of adaptive admission control in cellular wireless networks ensures quality of service by reserving bandwidth for handoff calls. It is equally important in current second generation wireless systems as well as in the future IMT-2000 and UMTS systems. In order to ensure bounded call level QoS we propose to track the changes of the handoff call arrival rate and integrate this information in the admission algorithm. However, the handoff call arrival rate can vary when the new call arrival rate and/or user mobility vary. In our previous work we have analysed bandwidth reservation techniques needed to maintain a stable call level QoS when new call arrival rate is changing in a group, or groups, of wireless cells. This paper analyses bandwidth reservation techniques that are adaptive to the user mobility as well as to the changing new call arrival rate, and which can ensure stable call level QoS over a range of user mobilities. We also propose the technique to derive bandwidth reservation policy when the QoS characteristics over a range of user mobilities are given.     

Soft QoS in Call Admission Control for Wireless Personal Communications

In wireless multimedia communication systems, call admission control (CAC) is critical for simultaneously achieving a high resource utilization efficiency and maintaining quality-of-service (QoS) to mobile users. User mobility, heterogeneous nature of multimedia traffic, and limited radio spectrum pose significant challenges to CAC. QoS provisioning to both new calls and handoff calls comes with a cost of low resource utilization. This paper proposes a CAC policy for a wireless communication system supporting integrated voice and dataservices. In particular, soft QoS (or relaxed target QoS) is incorporated in the CAC policy to make compromises among different objectives.Numerical results are presented to demonstrate that (a) in dealing with the dilemma between QoS satisfaction and high resource utilization, how the resource utilization efficiency can be increased by introducing soft QoS; and (b) in accommodating different types of traffic, how the QoS of low priority traffic can be improved by specifying soft QoS to high priority traffic.     

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。     

适应自相似业务流量模型的CAC算法研究

分析了呼叫接纳控制算法研究的现状，提出一种适应自相似业务流量模型的呼叫接纳控制算法，在接纳判决过程中引入概率接纳机制。理论分析和仿真结果验证了算法的可行性和在自相似业务流量模型下相对于传统呼叫接纳控制算法的优越性。     

具有大容量缓存器的ATM网络交换节点的接入允许控制

本文讨论了ＡＴＭ网络交换节点的缓存器容量较大时,如何实现实时接入允许控制的问题。我们从大量的计算机模拟的结果中发现,对于符合负指数分布的马尔可夫ＯＮ／ＯＦＦ单一类型或多类型信源,在信元及系统的其它参数保持不变的条件下,信元丢失概率和丢失率,只取决于缓存器容量与信元平均突发长度的比值。本文从“生灭过程”出发加以了证明。     

Downlink traffic control for multiple classes of services in MC-CDMA cellular systems

We consider the problem of downlink traffic control in Multi-code Code Division Multiple Access (MC-CDMA) systems, which support multiple classes of services with diverse QoS requirements. Prior solutions proposed for this problem have largely focused on call admission control at the connection level while neglecting the stochastic behavior of mobile subscribers and channel conditions. We quantitatively demonstrate that these statistical factors, in particular log-normal shadowing in propagation and voice activity factors, have a significant impact on the connection-level performance. Furthermore, we show that conventional data services can be best handled at the packet level as background transmissions by taking advantage of these statistical variations, which leads to significantly better utilization of the scarce wireless spectrum. The research was supported in part by grants from RGC under the contracts HKUST6104/04E and HKUST6165/05E, a grant from NSFC/RGC under the contract N_HKUST605/02, a grant from NSF China under the contract 60429202. Jihui Zhang’s work was partially supported by Microsoft fellowship. Jihui Zhang (S’02) received her B.S. degree from Fudan University, China in 2001, and the Ph.D. degree from the Hong Kong University of Science and Technology in 2005, both in the Computer Science. Her research interests include CDMA cellular networks and wireless ad-hoc networks. Bo Li (S’89-M’92-SM’99) received his B. Eng. and M. Eng. degrees in the Computer Science from Tsinghua University, Beijing in 1987 and 1989, respectively, and the Ph.D. degree in the Electrical and Computer Engineering from University of Massachusetts at Amherst in 1993. Between 1993 and 1996, he worked on high performance routers and ATM switches in IBM Networking System Division, Research Triangle Park, North Carolina. Since 1996, he has been with the Department of Computer Science, Hong Kong University of Science and Technology, where he is now an associated professor and Co-Director for the ATM/IP Cooperate Research Center, a government sponsored research center. He also holds an adjunct researcher position at the Microsoft Research Asia (MSRA), Beijing, China, and adjunct professorship in several universities. His recent research interests are on adaptive video multicast, packet scheduling and dynamic routing in optical networks, resource management in mobile wireless systems, scheduling and energy efficient routing in ad hoc networks, across layer design for sensor networks, and content distribution and replication. He has published 150 papers and held several patents in above areas. He has been on editorial board for 16 journals, mainly in IEEE and ACM. He has been involved in organizing over 40 conferences, esp. IEEE Infocom since 1996. He was the Co-TPC Chair for IEEE Infocom 2004.     

End-to-End Adaptive QoS Provisioning over GPRS Wireless Mobile Network

The General Packet Radio Service (GPRS) offers performance guaranteed packet data services to mobile users over wireless frequency-division duplex links with time division multiple access, and core packet data networks. This paper presents a dynamic adaptive guaranteed Quality-of-Service (QoS) provisioning scheme over GPRS wireless mobile links by proposing a guaranteed QoS media access control (GQ-MAC) protocol and an accompanying adaptive prioritized-handoff call admission control (AP-CAC) protocol to maintain GPRS QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded channel access delay for delay-sensitive traffic, bounded packet loss probability for loss-sensitive traffic, and dynamic adaptive resource allocation for bursty traffic with peak bandwidth allocation adapted to the current queue length. The AP-CAC protocol provides dynamic adaptive prioritized admission by differentiating handoff requests with higher admission priorities over new calls via a dynamic multiple guard channels scheme, which dynamically adapts the capacity reserved for dealing with handoff requests based on the current traffic conditions in the neighboring radio cells. Integrated services (IntServ) QoS provisioning over the IP/ATM-based GPRS core network is realized over a multi-protocol label switching (MPLS) architecture, and mobility is supported over the core network via a novel mobile label-switching tree (MLST) architecture. End-to-end QoS provisioning over the GPRS wireless mobile network is realized by mapping between the IntServ and GPRS QoS requirements, and by extending the AP-CAC protocol from the wireless medium to the core network to provide a unified end-to-end admission control with dynamic adaptive admission priorities.