综合业务系统中切换呼叫损失概率的计算方法

准确、快速地得出通信系统中的呼叫损失概率是实现实时呼叫接入控制的前提。该文提出一种新的无线综合业务系统信道预留策略,基于该策略给出在给定系统小区的信道数、预留信道数、新呼叫与切换呼叫负荷以及接入控制策略前提下,能快速、准确地计算新呼叫及切换呼叫的呼叫损失概率的方法。仿真结果与算法得到的结果是相符的。     

一种新型的异构无线网络呼叫接纳控制算法研究

在CDMA2000蜂窝网络和WLAN组成的异构无线网络中,呼叫接纳控制算法对于提高系统资源的利用率有着非常重要的作用。根据WLAN的网络负载情况和移动用户的速度来判决是否接入WLAN;提出一种基于概率机制的CAC算法,WLAN能够限制来自于蜂窝网的VHO呼叫,减少不必要的VHO处理负荷;对新呼叫阻塞率和DVHO呼叫阻塞率进行理论分析和推导。仿真结果表明,该CAC算法能够减少不必要的重复上下垂直切换,同时将DVHO呼叫阻塞率控制在可接受的范围内。算法保证了较高的系统吞吐量,提高了系统整体性能。     

融合分层呼叫协议与GCM-FIFO的移动管理方案

针对节点高速移动的UAVS通信网络中的移动性管理问题,提出了基于分层呼叫协议的位置管理方案以及融合滞后余量与门限结合的切换判决方法、UAV节点自主决策的紧急切换控制策略和GCM-FIFO信道分配策略的切换管理方案。通过相关理论分析和图形化的测试与仿真,结果表明:分层呼叫协议解决了UAVS通信网中节点高移动性问题;针对系统切换业务量高但信道数有限的特点提出了GCM-FIFO信道分配方案,在满足一定的新呼叫阻塞的同时减小了UAV节点切换失败的概率;针对中继机节点可能被击毁而提出的UAV节点自主决策的紧急切换策略,弥补了一般性切换方案的不足。     

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.     

基于排队论的UAVS通信网切换方案分析

针对UAVS通信网切换管理中的信道分配问题,提出了保护切换信道与切换呼叫按照先入先出队列排队相结合的方案(GCM-FIFO),利用Markov链对该方案进行了建模,通过数学推导分析了系统的性能,并就等待队列容量对切换性能的影响进行了讨论和仿真.结果表明:通过实施GCM-FIFO方案,UAVS通信网获得了较好的切换性能,而且随着队列容量的增加,切换呼叫失败的概率呈下降趋势,但是当队列容量超过某个值后,切换呼叫失败的概率趋于恒定,因而应根据系统相关参数,利用仿真结果选择合适的队列容量.     

感知无线电网络中的呼叫延迟阻塞概率研究*

呼叫允许控制是无线资源管理中的重要组成部分,是一种减少网络拥塞、保证服务质量和提高网络资源利用率的重要机制。在给定系统资源情况下,准确估计用户呼叫延迟阻塞概率,能为网络优化建设提供一个重要依据。在排队论——生灭过程的基础上,探讨了感知无线电（CR）网络中的呼叫延迟阻塞概率与系统资源的关系,并给出了估计公式,仿真结果表明其精确度很高。     

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。     

一种新的基于多业务的移动通信系统切换策略

针对目前移动通信系统大部分信道切换策略中新呼叫阻塞率高的问题,提出了一种新的呼叫延迟切换策略,该策略是让即将占用最后一个空闲信道的新呼叫短暂延迟后再占用空闲信道,切换呼叫则直接占用空闲信道,缩短了信道被全部占用的时间,增加了新呼叫和切换呼叫占用信道的机会。该策略同时考虑了数据业务之间的优先级,只有当高优先级数据队列中的数据包为空时,低优先级队列中的数据包才能够占用信道。给出了切换呼叫掉话率、新呼叫阻塞率及数据包掉包率的理论公式。与预留信道策略和可移动边界策略的对比表明,新策略既提高了新呼叫进入系统的概率,又有效降低了切换呼叫的掉话率,同时也减少了高优先级数据的掉包率。     

一种基于TCRA的低轨星座通信系统的强占预留信道策略

在基于时间信道预留算法的基础上,提出了一种改进的低轨星座通信系统信道分配策略——强占预留信道策略。讨论了策略的基本原理,并通过仿真,比较分析了该策略与 TCRA 和固定信道预留策略对系统新呼叫阻塞概率、切换失败概率和服务等级的影响。仿真结果表明,与 TCRA 策略相比,该策略有效降低了新呼叫阻塞,同时为网络提供更好的 QoS 保证。     

呼叫准入约束下Macro-Femto小区选择GSPN模型研究

随着数据业务快速增长,仅靠宏蜂窝网络已无法满足流量需求;飞蜂窝网络可以有效分流宏蜂窝流量, 近年来 所构成的Macro-Femto架构得到了较广泛的部署。Macro-Femto网络部署的关键问题之一是小区选择,由于飞蜂窝网络频谱资源有限,进行小区选择时仍需考虑呼叫准入控制(Call Admission Control,CAC)。图形化的广义随机Petri网(Generalized Stochastic Petri Nets,GSPN)具有并行性、不确定性和异步特性以及强大的分析复杂系统的功能。针对Macro-Femto网络的呼叫准入约束机制,通过分析呼叫对信道的占用情形,在改进呼叫重审机制的基础上,建立了呼叫准入控制策略GSPN模型。利用建立的GSPN模型,分析了不同呼叫准入控制策略对新呼叫和切换呼叫阻塞率的影响,给出了部分重审机制的呼叫准入控制策略。在分析飞蜂窝的高速服务特性和宏蜂窝的高负载能力的基础上,结合部分重审呼叫准入策略和GSPN方法,提出了基于负载的飞蜂窝优先选择方案(Load-Based Femto-Priority Selection Scheme,LFP)。仿真结果表明,较典型的飞蜂窝优先选择方案,所提出的LFP方案对新呼叫的阻塞率和切换呼叫的掉线率分别降低了2.7%和4.6%。     

基于声望模型的联合呼叫接纳控制算法

为了弥补异构无线网络中呼叫接纳控制研究场景的局限性,降低终端选择接入网时的盲目性,将研究场景从两个接入网延伸为多个接入网,提出一种基于声望模型的联合呼叫接纳控制算法。将声望模型应用于网络选择过程,增加了网络反馈机制。在用户侧,终端根据网络声望值大小选择接入网;在网络侧,采用动态带宽分配和缓冲队列策略来提高接入成功率。仿真结果表明,该算法有效降低了新呼叫阻塞率和切换呼叫掉线率。     

Completed analysis of cellular networks with PH-renewal arrival call

In this paper, we apply the PH-renewal process to model new call and handoff processes, and apply the matrix-analytic approach to explore the performance measures of the drop and block probabilities. We examine the bursty nature of handoff call drops by means of conditional statistics with respect to alternating block and non-block periods. Five related performance measures are derived from conditional statistics, including the long-term new call block and handoff call drop probabilities, and the three short-term measures of average length of a block period and a non-block period, as well as the conditional handoff call drop probability during a block period. These performance measures greatly assist the priority reservation handoff mechanism in determining a proper threshold guard channel in the cell. Furthermore, we derive the handoff call drop probability from the short-term performance measures of average length of a block period and a non-block period, as well as the conditional handoff call drop probability during a block period. The results presented in this paper can provide guidelines for designing adaptive algorithms to adjust the threshold in the guard channel reservation handoff scheme.     

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.     

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。     

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.     

An integrated traffic model for multimedia wireless networks

Multimedia wireless networks are seen today as one of the key factors for the success of the global communication infrastructure in the near future. Such networks will have to handle a range of heterogeneous traffic classes with different QoS requirements. Their design, planning and control must be supported by suitable traffic models capable of dealing with a new set of constraints where QoS management and mobility play an important role.This paper proposes a traffic model for a cellular multimedia wireless network characterized by the integration of mobility and traffic management aspects. User mobility is modeled through a Markov renewal process, which allows for non-exponential cell residence times and may restrict the user mobility to existent paths in the system. A Markov-modulated fluid process is used to describe the changes in the bandwidth requirements of each mobile over the duration of its calls, including the periods where the mobile is inactive (without call).Based on the proposed model, the number of mobiles per class of traffic in a cell and the handoff processes are characterized. System performance results, such as new and handoff call blocking probabilities, for network planning are derived. Also, the distribution of the required capacity in a short time interval for network control is obtained. Simulations were carried out to validate the analytical results. The comparisons have shown that the integrated model may be regarded as a good basis to build useful teletraffic engineering tools for multimedia wireless networks.     

异构无线系统中一种改进的垂直切换方案

针对异构无线系统垂直切换需要综合考虑多种因素的特点,提出了一种改进的垂直切换方案。方案首先考虑网络费用,对原方案的代价函数进行改进。然后根据电池电量,分别采用不同的切换方法。最后将切换语音呼叫留在原网络,以达到减小频繁切换的目的。仿真结果表明,本方案较原方案很好的减小了系统阻塞率、平均切换次数和平均通话费用,有效提高了系统性能,具有现实意义。     

异构网络中贪婪资源分配策略的研究

针对当前异构网络中多种业务并存的现状,提出了一种可应用于由移动微波存取全球互通和通用移动通信系统组成的异构网络中考虑切换业务优先的贪婪资源分配策略,并通过网络中的呼损率验证了该策略的可行性;接着,在NS2环境下将该策略与公平资源分配策略在资源利用率、分组丢失率方面进行了比较.仿真结果显示,新策略可以提供良好的服务质量,前者的资源利用率和分组丢失率比后者分别改善了13％和14％左右.     

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.