IEEE802.16中基于自适应信道预留的呼叫接入策略

呼叫接入控制（CAC）在宽带无线接入（BWA）服务质量（QoS）中起着非常重要的作用。对无线城域网中IEEE802.16复杂的QoS定义,该文提出了一种在IEEE802.16中基于自适应资源预留的呼叫接入控制策略（AR-CAC）。该策略根据UGS负载和信道利用率为其自适应预留信道,同时考虑了IEEE802.16业务的带宽特性。仿真结果表明,该策略在硬切换呼叫切换失败概率不变的情况下降低了高优先级服务的呼叫阻塞率,同时增大了系统的吞吐量。     

基于马尔科夫链的联合呼叫接入控制算法

异构网络的接入策略与网络资源管理效率紧密相关;同时,网络复杂性与网络资源竞争性直接影响到用户服务质量。针对异构网络接入控制存在的切换掉话率和呼叫阻塞率高、资源利用率低等问题,提出了基于马尔科夫链的联合呼叫接入控制算法。接入控制算法为切换呼叫业务、实时业务动态地预留了一定的带宽资源,根据不同业务设置带宽降级因子来决定是否释放带宽;同时,根据用户偏好和不同业务的QoS要求,构建了呼叫接入控制效用函数,利用马尔科夫链进行了建模分析。仿真表明,算法提高了网络资源利用率,降低了系统复杂度,满足了各类业务的QoS要求。     

无线多媒体网络中一种基于测量网络状态的动态呼叫接纳控制算法

提出了一种无线多媒体网络中基于测量网络状态的动态呼叫接纳控制算法.它区分了实时和非实时业务,在网络带宽资源不足时可通过降低非实时业务带宽确保实时业务呼叫连接的可靠性;还可根据当前网络状况调整预留带宽大小,使小区实时业务切换呼叫掉线率低于设定的门限值.大量仿真结果显示该算法具有低实时业务切换呼叫掉线率和与固定预留方案相当的带宽利用率,而只以略高的新呼叫阻塞率为代价,适合各种不同概率发生时实际应用的情况.     

多媒体CDMA蜂窝网络中联合退避缓存及速率自适应的呼叫接纳控制策略

资源管理和呼叫接纳控制作为未来蜂窝网络的核心管理模块,能为移动用户提供具有QoS保证的多媒体应用并实现无线资源的有效利用.针对多业务CDMA蜂窝网络,结合非理想功率控制下的容量定义,提出退避缓存与自适应速率调控相结合的呼叫接纳控制策略.其中退避缓策略采用请求呼叫主动退避的思想,有效降低阻塞率;自适应速率调控策略则采用业务用户双重分级的思想,确保用户公平性的同时实现平稳的QoS.仿真结果表明,该策略可以自适应地保证各类业务的QoS要求,提高业务间的公平性和系统资源的利用率.     

异构分层无线网络中基于业务QoS保证的切换策略研究

针对异构分层无线网络提出了一种保证业务QoS的切换策略。该策略在层间呼叫双向溢出基础上,为实时业务切换设置了保护信道,为非实时业务切换设置了缓冲队列。为了进一步降低实时业务切换的掉线率,还使用了信道侵占技术,原理是实时业务切换呼叫可以侵占数据业务正在使用的信道资源。仿真结果表明,提出的切换方法能够显著降低各类切换业务的掉线率,同时整个异构分层系统的信道利用率也略有提高。     

部分共享型综合业务网流量拥塞控制策略

为控制流量拥塞,提出以在线的各类On-Off型实时可变比特率业务连接的峰值带宽和预期的分组丢失率门限为依据的部分共享型呼叫接纳控制策略。给出呼叫损失概率和分组丢失率的计算方法,分析这些服务质量指标与该策略中可动态调整的控制参数之间的关系,对相关结论给予数学证明或数值验证。     

CDMA网络中综合业务的呼叫接纳控制算法及性能分析

呼叫接纳控制(CAC)是CDMA系统无线资源管理中的重要组成部分,有效的CAC算法能在满足各类业务不同QoS要求的同时,提高资源的利用率。本文对于新呼叫和切换呼叫,提出了一种有效的呼叫接纳控制算法,给予了切换呼叫更高的优先级,并采用Markov链对算法的性能进行了分析。     

WiMAX网络中信噪比与带宽结合的接纳控制算法

呼叫接纳控制（CAC）是宽带无线接入网络无线资源管理中一个重要的组成部分,其中策略设计的好坏直接影响着网络的性能和资源利用率。针对现有基于WiMAX的接纳控制算法仅考虑了带宽作为接纳控制的标准,提出一种结合带宽和信噪比的接纳控制算法,在考虑小区带宽因素的同时能兼顾考虑接纳后业务的信噪比情况。仿真结果表明,结合带宽和信噪比的接纳控制算法可以有效的降低系统中呼叫的掉线率,提高系统性能。     

一种分层多描述编码的动态带宽分配策略

针对无线流媒体业务带宽资源有限的特点,提出一种基于分层多描述编码的动态带宽分配策略LMDBA.该策略利用了分层多描述编码的特性实现动态带宽分配,并采用QoS升降级策略,在保证用户QoS的前提下,尽可能地降低系统阻塞,提高系统带宽资源利用率.并对QoS升降级策略进行了公平性分析.仿真实验结果表明,在提供一定用户QoS保证下,提出的新策略比传统固定带宽分配策略在带宽资源利用率和系统阻塞上有显著的改善.     

基于IEEE 802.16的接纳控制机制

分析IEEE 802.16的QoS机制,针对其没有详细规定接纳控制算法的情况,结合协议中定义的业务类型QoS特性,在信令交互机制下,提出一种基于优先级的动态带宽分配接纳控制机制。仿真结果表明,与预留带宽的固定带宽分配机制相比,采用该机制后,系统的切换连接掉线率、新增连接的阻塞率和带宽利用率得到改善。     

On utility-fair bandwidth adaptation for multi-class traffic QoS provisioning in wireless networks

The ability to adjust the allocated bandwidth of ongoing calls to cope with wireless network resource fluctuations is becoming increasingly important. In this paper, we describe a utility-based bandwidth adaptation scheme for multi-class traffic quality-of-service (QoS) provisioning in wireless networks. With the proposed scheme, each call is assigned a utility function according to its adaptive characteristics. Depending on the network load the allocated bandwidth of ongoing calls are upgraded or degraded dynamically such that each call receives fair utility. The quantization of utility function by dividing the utility range into a fixed number of equal intervals is a key feature of our proposed utility-fair algorithm. Appropriate call admission control and bandwidth reservation policies are also integrated into the proposed scheme to provide QoS guarantees to the new and handoff calls. Extensive simulation experiments have been conducted to evaluate the performance of the proposed scheme compared with two other existing ones. Results show that our bandwidth adaptation scheme is effective in achieving utility fairness while keeping the call blocking and handoff dropping probabilities substantially low.     

Joint call and packet QoS in cellular packet networks

This paper proposes a novel call admission control scheme capable of providing a combination of call and packet level quality of service requirements in cellular packet networks. Specifically, we propose a distributed call admission control scheme called PFG, which maximizes the wireless channel utilization subject to a predetermined bound on the call dropping and packet loss probabilities for variable-bit-rate traffic in a packet-switched wireless cellular network. We show that in wireless packet networks, the undesired event of dropping an ongoing call can be completely eliminated without sacrificing the bandwidth utilization. Extensive simulation results confirm that our scheme satisfies the hard constraint on call dropping and packet loss probabilities while maintaining a high bandwidth utilization.     

基于位置服务信息的动态速率切换算法

提出了一种新的无线网络中的基于位置服务信息的动态速率切换算法,根据LBS信息和信号变化矢量判断即将来临的数据切换呼叫并为其预留信道,兼顾数据业务的VBR特性而自适应动态改变其服务带宽。仿真的结果表明,与其他切换算法相比,新算法的呼叫强拆率和呼叫阻塞率均有下降,信道利用率得到提高,提高了无线呼叫接入控制系统的QoS。     

无线网络时变带宽业务的准入控制性能分析

无线蜂窝网络的通话准入控制方法与通话的 Qo S以及无线信道的利用率密切相关 .使用 Markov过程得出了业务带宽需求时变状况下系统性能 (通话的切换掉线概率、并发掉线概率、阻塞概率以及信道利用率 )的理论模型 .通过数值结果分析了系统负载、用户的移动、通话的持续时间对系统性能的影响     

A novel contention-on-demand design for WiFi hotspots

In widely deployed wireless “hot-spot” networks, nodes frequently join or leave, and inelastic/elastic and saturated/nonsaturated flows coexist. In such dynamic and diverse environments, it is challenging to maximize the channel utilization while providing satisfactory user experiences. In this paper, we propose a novel contention-on-demand (CoD) MAC scheme to address this problem. The CoD scheme consists of a fixed-CW algorithm, a dynamic-CW algorithm, and an admission control rule. The fixed-CW algorithm allows elastic flows to access limited system bandwidth; the dynamic-CW algorithm enables inelastic flows to contend for channel on demand and quickly adapt to network change; and the admission control rule rejects overloaded traffic for providing good user experiences. We then perform an asymptotic analysis to develop a simple and practical admission control rule for homogeneous and heterogeneous traffic; our rule can not only adapt to the change in offered loads and node number, but also maximize the system utilization. Finally, extensive simulations verify that our scheme is very effective and our theoretical result is very accurate.     

无线移动网中的队列降质接纳控制

提出了在无线移动网中基于队列的降质接纳控制算法,它区分了实时业务和非实时业务,同时考虑了切换优先和业务优先两种优先级。在网络带宽资源不足时,通过降低某些可容忍质量下降的呼叫的质量并与队列缓存呼叫相结合的方式,来获得小区中高优先级业务的新呼叫阻塞率和切换呼叫中断率均很低的性能改善。性能分析结果显示该算法简单易实现,具有较低的新呼叫阻塞率、切换呼叫中断率和较高的系统利用率。     

支持动态带宽分配的呼叫接入策略

为了适应无线网络对多媒体业务的业务服务质量的需求,论文根据无线网络的多媒体业务特征,提出了一种支持动态带宽分配的无线多媒体业务的呼叫接入策略。通过对该策略进行数学模型分析和数值仿真,结果表明,该策略在小区带宽紧张时,通过降低可变带宽业务的业务带宽,能有效降低用户呼叫阻塞概率和中断概率;在小区带宽有剩余时,可以通过增加可变带宽业务的服务带宽来提高资源利用率。另外,可变带宽业务还能够灵活地借用为越区切换用户预留的带宽资源,充分地利用系统资源。     

Mobility-based predictive call admission control and bandwidth reservation in wireless cellular networks

This paper presents call admission control and bandwidth reservation schemes in wireless cellular networks that have been developed based on assumptions more realistic than existing proposals. In order to guarantee the handoff dropping probability, we propose to statistically predict user mobility based on the mobility history of users. Our mobility prediction scheme is motivated by computational learning theory, which has shown that prediction is synonymous with data compression. We derive our mobility prediction scheme from data compression techniques that are both theoretically optimal and good in practice. In order to utilize resource more efficiently, we predict not only the cell to which the mobile will handoff but also when the handoff will occur. Based on the mobility prediction, bandwidth is reserved to guarantee some target handoff dropping probability. We also adaptively control the admission threshold to achieve a better balance between guaranteeing handoff dropping probability and maximizing resource utilization. Simulation results show that the proposed schemes meet our design goals and outperform the static-reservation and cell-reservation schemes.     

Dynamically adaptive channel reservation scheme for cellular networks

In personal communications networks (PCN) supporting network-wide handoffs, new and handoff requests compete for connection resources in both mobile and backbone networks. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. In general, most of the previously proposed schemes for radio channel allocation in cellular networks reduce handoff call blocking probability substantially at the expense of increasing the new call blocking probability by giving higher priority to handoff calls over new calls in admission control. This reduces the total admitted traffic and results in inefficient utilization of wireless channels. The tradeoff between the new and handoff calls blocking probabilities should be defined on importance basis. In this paper, we propose a performance metric equation that makes a trade off between the two probabilities depending on the network preferences. Using this equation, we study the performance of various proposed channel reservation schemes. Also in this paper, a new dynamically adaptive channel reservation scheme (DACRS) is developed and compared with other schemes proposed in the literature. The DACRS assigns handoff-reserved channels to new calls depending on the locality principle in which the base station with the help of location estimation algorithms in the mobile location center predicts the position of the mobile terminal. Eventually, the DACRS is designed to improve channel utilization while satisfying the QoS of the calls. As will be shown analytically and through simulation, the DACRS outperforms current reservation schemes and results in more statistical gain, and powerful channel utilization.