基于多业务的移动通信系统呼叫接入控制

针对在可移动边界保护信道方法中新呼叫堵塞率高的问题,提出一种呼叫接入控制策略。当切换呼叫的掉话率小于门限时,新呼叫以一定的概率使用为切换呼叫预留的保护信道。当高优先级数据等待队列中的数据包为空时,传输普通数据等待队列中的数据包。仿真结果表明,在对切换呼叫掉话率影响较小的前提下,该策略能够有效降低新呼叫的堵塞率和高优先级数据的掉包率。     

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。     

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。     

IEEE 802.16系统中带有收益因子的动态呼叫接纳控制算法*

针对IEEE 80216 OFDMA系统,提出了一种考虑运营收益并且动态调整预留信道的呼叫接纳控制算法。该算法将一个连接申请潜在的运营收益值作为接入优先级函数的因子,从而提高系统的运营收益;其次,算法根据系统内资源的使用情况动态调整预留信道,在降低系统掉话率的同时,也尽可能地将呼叫阻塞率保持在较低水平。将所提算法与传统接纳控制方法进行了仿真比较,结果表明该算法能够有效控制系统掉话率和阻塞率,达到用户使用满意度要求,同时增大系统运营收益。     

保护信道和排队相结合的信道分配策略

提出了一种适用于语音、数据呼叫的蜂窝移动通信系统的信道分配策略。该策略为数据呼叫提供保护信道,降低数据呼叫的阻塞率。同时,采取语音呼叫排队策略抑制数据保护信道引起的语音呼叫阻塞率的恶化。为了进一步提高系统的性能,在策略中引入了不耐烦顾客,并建立了带有不耐烦顾客的排队模型。仿真结果表明该策略能够有效地降低语音呼叫和数据呼叫阻塞率,改善系统性能。     

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。     

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。     

CDMA2000-1X系统多业务复合越区切换策略

提出一种多业务综合越区切换策略,该策略同时支持实时业务和非实时业务;通过双队列模式解决了实时业务的虚拟切换问题,有效地利用资源、缓解呼叫和切换拥塞;并通过建立多维马尔科夫链越区切换策略模型,为请求越区切换的实时业务提供了抢占优先和排队相结合的策略。仿真结果表明,系统的呼损率、阻塞率、强制中断概率等系统性能指标得到明显改善。     

联合无线资源管理技术的改进型垂直切换算法

针对移动主机在垂直切换过程中无线资源的合理分配问题,基于通用移动通信系统(UMTS)和无线局域网(WLAN)构建的无线异构网络环境,按照不同业务的服务质量(QoS)优先级,提出一种联合带宽借用、负载均衡机制的新型垂直切换算法;建立基于Matlab的性能评估仿真平台,对新呼阻塞率、掉话率进行分析。结果表明,该算法可以在维持较小阻塞率的情况下,有效减少掉话率,保证QoS需求高的话音业务取得很好的服务质量。     

一种基于流量预测的多优先级队列缓存管理算法

在引入优先级因素的流量预测模型基础上,提出了一种多优先级队列的缓存管理算法,该算法通过固定时刻的缓存预分配,结合时划间隔中的缓存竞争,使缓存的分配更加合理而有预见性,仿真实输表明它能够明最降低高优先级数据包的丢包率,同时兼顾低优先级数据包的转发,并且不产生额外的延迟,表明该算法有很好的应用价值。     

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.     

Optimal prioritized channel allocation in cellular mobile systems

Under the cutoff priority discipline, the optimal prioritized channel allocation problem is formulated, which minimizes the weighted average blocking probability of handoff calls while ensuring the prespecified grade of service for new calls and the co-channel interference constraints. We use the concept of pattern to deal with the problem more conveniently. Using Lagrangean relaxation and subgradient optimization techniques, we obtain high-quality solutions with information about their deviations from true optimal solutions. Computational experiments show that our method works very well.Scope and PurposeChannel allocation is one of the most important problems in the design of cellular mobile systems. Since the number of cells of forthcoming networks will increase rapidly, this problem will be of even greater importance in the future. In cellular mobile systems, a new channel should be assigned by the new base when a call enters an adjacent cell. It provides continuation of ongoing calls as the user travels across cell boundaries, and is called handoff. The handoff call is forced to terminate before completion if there are no channels available in the new cell. However, in many practical situations, the blocking of a handoff call attempt is critical since it will result in a disconnection of the call in the middle of conversation. Thus, for reducing the blocking probability of handoff calls, several algorithms based on the cutoff priority scheme have been introduced in the literature. In the cutoff priority scheme, priority is given to handoff calls by exclusively reserving some channels called guard channels for them. In this article, we formulate a prioritized channel allocation problem under the cutoff priority scheme in general multicell environments, and suggest an efficient algorithm to solve that problem.     

Performance analysis of wireless mobile networks with queueing priority and guard channels

The blocking probability of originating calls and forced termination probability of handoff calls are important criteria in performance evaluation of integrated wireless mobile communication networks. In this paper, we model call traffic in a single cell in an integrated voice/data wireless mobile network by a finite buffer queueing system with queueing priority and guard channels. We categorize calls into three types of service classes: originating voice calls, handoff voice calls and data calls. The arrival streams of calls are mutually independent Poisson processes, and channel holding times are exponentially distributed with different means. We describe the behavior of the system by a three‐dimensional continuous‐time Markov process and present the explicit expression for steady‐state distribution of queue lengths using a recursive approach. Furthermore, we calculate the blocking, forced termination probabilities and derive the Laplace–Stieltjes transform of the stationary distribution of actual waiting times and their arbitrary kth moment. Finally, we give some numerical results and discuss the optimization problem for the number of guard channels.     

LEO卫星通信系统中信道分配策略仿真

切换是LEO卫星移动通信系统中移动性管理的一个重要组成部分。LEO切换中的信道分配一般采用保护信道和各种排队方法相结合的策略。研究了多业务条件下LEO卫星通信系统越区切换中的信道分配策略,根据数据业务和话音业务的特点,提出了适用于LEO卫星通信系统的保护信道和强占优先相结合的信道分配策略。建立了一个简单而有效的LEO卫星通信系统切换模型,将新策略与传统的保护信道策略进行比较,仿真结果表明新策略以略微增加数据时延为代价换取了话音业务各项性能的极大改善。     

A hybrid channel allocation algorithm with priority to handoff calls in mobile cellular networks

This paper proposes and investigates a novel analytical model of a hybrid channel allocation algorithm within wireless cellular networks. Each cell of the network consists of a predesigned fixed number of channels and the network may approve the request for extra channels for both new and handoff calls if all predesigned channels are occupied. This approval depends on the types of new and handoff calls, as well as the number of approved additional channels in the cell. If a request is denied for the arriving new call, this call will be blocked and cleared from the system. However, if a request is denied for an arriving handoff call, this call will not be blocked immediately but rather put on hold in a buffer with finite space. The implication behind this is to give priority to handoff calls. For this proposed hybrid channel allocation scheme, we first obtain the stationary distribution of each cell when there are i calls connecting to the system and j calls holding on in the buffer. We then derive new and handoff call blocking probabilities, the average number of borrowed channels, and the average delay period of handoff calls. The numerical results show that the proposed hybrid algorithm is more efficient than other approaches, specifically, in comparison with methods without a borrowing capability for new calls and those without a reserved buffer priority for handoff calls. The idea and results presented in this paper are expected to provide guidelines for field data processing within current wireless and mobile network design and performance evaluation.     

An adaptive call admission algorithm for cellular networks

In this paper, we first propose a new continuous action-set learning automaton and theoretically study its convergence properties and show that it converges to the optimal action. Then we give an adaptive and autonomous call admission algorithm for cellular mobile networks, which uses the proposed learning automaton to minimize the blocking probability of the new calls subject to the constraint on the dropping probability of the handoff calls. The simulation results show that the performance of the proposed algorithm is close to the performance of the limited fractional guard channel algorithm for which we need to know all the traffic parameters in advance.     

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 preemptive channel allocation scheme for multimedia traffic in mobile wireless networks

This paper presents a channel allocation model with both partial and full preemptive capabilities for multimedia traffic in mobile wireless networks. The different types of multimedia traffic in transmitting through next-generation networks possess different characteristics and demand an adequate channel allocation scheme to fulfill individual Quality of Service (QoS) requirements. In the proposed model, multimedia traffic is classified into three classes corresponding to different priority levels in a decreasing order. To effectively reduce the dropping probability, a higher-priority handoff call is allowed to fully or partially preempt any lower-priority ongoing calls when the channel capacity becomes insufficient. In addition, to prevent from possible starvation of the lowest-priority traffic, a portion of system channels are purposely reserved. Performance measures, including the dropping probability of handoff calls, the call-interruption probability that an ongoing call is forced to termination due to full preemption, and the bandwidth reduction ratio due to partial preemption, are investigated through an analytical model built with 4-D Markov chains. The numerical results demonstrate the effectiveness of our model.