基于排队理论的信道分配算法研究

针对蜂窝移动通信系统,基于排队理论提出了一种信道分配方案。该方案将信道分为2部分:语音信道和数据保护信道。预留数据保护信道用于补偿数据丢包率,同时对语音业务设置FIFO排队缓冲器,切换呼叫优先占用缓冲器以确保切换优先。当语音信道空闲时,数据业务可以占用语音信道,一旦有语音呼叫请求到来且无可用语音信道,数据业务应释放占用的语音信道,在数据缓存器中排队等待。仿真结果表明该方案不仅降低了新增呼叫阻塞率和切换掉话率,而且提升了数据业务的性能。     

多业务无线蜂窝网中呼叫接入策略性能分析

下一代无线蜂窝网的关键问题之一是能够提供多业务服务,这就要求呼叫接入策略能够满足各种业务的不同Qos要求,同时有效地利用带宽资源。本文采用双阈值带宽预留策略处理多种业务呼叫的接入,并利用实验仿真比较分析了基于此策略的数据业务可变模型和数据业务排队模型的性能。仿真结果表明数据业务可变模型能够减小切换语音呼叫掉话率而且提高整个系统的性能,数据业务排队模型能够明显降低数据呼叫阻塞率并提高信道利用率。     

基于预留信道和强占优先相结合的接入策略

报道了一种用于话音／数据综合的蜂窝移动通信系统中的基于预留切换信道和强占优先策略相结合的业务接入方案。在本方案中为具有越区切换请求的话音呼叫提供了预留切换信道和强占数据业务的优先权相结合的接入策略。同时为了提高系统总的承载话音的业务量,也为新近产生的话音呼叫提供了一定的强占数据业务的优先权。结果表明：我们的方案可以为移动用户提供更好的服务质量。     

CDMA分层小区结构系统中基于干扰门限的呼叫接人控制策略

本文提出了一种分层小区结构系统中的呼叫接入控制策略，系统根据当前本小区和周围小区的干扰情况实时地对呼叫请求作相应控制，考虑了实时语音和非实时数据两种典型业务，为切换呼叫设置了高于新呼叫的优先级，并对暂时得不到资源的切换呼叫（包括语音和数据业务）进行排队处理，有效地降低了系统的切换掉话率。     

CDMA分层小区结构系统中基于干扰门限的呼叫接入控制策略

本文提出了一种分层小区结构系统中的呼叫接入控制策略,系统根据当前本小区和周围小区的干扰情况实时地对呼叫请求作相应控制,考虑了实时语音和非实时数据两种典型业务,为切换呼叫设置了高于新呼叫的优先级,并对暂时得不到资源的切换呼叫(包括语音和数据业务)进行排队处理,有效地降低了系统的切换掉话率.     

切换保留信道与新呼叫排队相结合的LEO星座通信系统信道分配方案研究

提出一种适用于LEO(低轨道)星座通信系统的信道分配方案。该方案为切换呼叫提供了保留信道,降低了切换呼叫的阻塞概率。同时,采取新呼叫排队策略抑制保留信道引起的新呼叫阻塞概率的恶化,如果正在进行的呼叫离开,队列中的新呼叫可以按照次序获得分配信道。结果表明,该方案可以显著降低切换呼叫阻塞概率,并使新呼叫阻塞概率得到改善。     

一种新型的TD-SCDMA动态信道分配方案

本文提出了一种基于可移动边界(MB)的动态信道分配方案.该方案将信道分为两部分:语音信道和数据信道.在业务传输过程中,如果语音信道空闲且数据缓存器队列不空时,那么队列中的数据包可以借用语音信道进行数据传输.而当语音呼叫到来时,语音业务可以强占被数据业务借用的语音信道,进行语音业务传输,而数据业务则停止在借用的语音信道中的传输,继续排队等待.仿真结果显示此方案可以降低系统成本,提高数据业务的性能和更有效地利用系统资源.     

移动通信系统呼叫接入控制算法性能分析

在对移动系统的性能分析中，为了便于分析，通常都没有区分一个小区中切换呼叫和新 呼叫，而是假定它们的信道占用时间具有相同的分布。但在有些实际的系统中，这种假设是不合理的， 两者信道占用时间的均值往往是不同的。设计了一种适用于多业务的呼叫接入控制算法，它对语音业 务基于保护信道法而对语音和数据业务之间采取可移动边界法，并对其性能进行了分析，结果表明切换 呼叫和新呼叫的均值对语音业务和数据业务的性能都具有重要的影响。     

基于信道预留和强占优先的接力切换策略

提出了一种适用于TD-SCDMA(Time Division Synchronous Code Division Multiple Access)移动通信系统综合业务(语音/数据)的接力切换策略.该策略为语音切换预留信道,根据语音用户属性设置不同切换优先级,赋予语音切换和语音新呼叫对数据服务信道的强占优先权.仿真表明,...     

一种新的切换策略在LEO卫星系统中的应用

增强对数据业务等非话音业务的支持,是LEO(低地球轨道)卫星通信系统的一个重要发展方向。提出了LEO卫星通信系统中一种新的保护信道和强占优先相结合的信道分配策略,即为话音呼叫提供一定的强占数据业务的优先权。将该策略与单纯保护信道策略的各项主要性能指标进行比较,结果表明新策略以略微增加数据时延为代价换取了话音新呼叫阻塞概率和切换阻塞概率的极大改善。     

一种适用于B3G移动通信系统下行共享信道的调度算法

本文针对后三代(B3G)移动通信系统中的宽带无线信道特性和流媒体业务特征,分析了可用于高速下行共享信道的各种传统分组调度算法,提出面向流媒体业务能够提高系统吞吐量的基于优先级公平调度(Priority-Based Fairness Scheduling,PBFS)算法.该算法根据各移动用户收发信道质量和业务传输的QoS要求动态调整各用户的业务传输优先级,确定下行共享信道的调度方案.并给出该算法的简化形式S-PBFS.仿真结果表明,与传统调度算法相比,S-PBFS算法在数据包传输时延受限的条件下具有无线信道利用率高、实现复杂度低等特点.     

Two-step multipolling MAC protocol for wireless LANs

The IEEE 802.11 standard defines two coordination functions: distributed coordination function (DCF) and point coordination function (PCF). These coordination functions coordinate the shared wireless medium. The PCF uses a centralized polling-based channel access method to support time-bounded services. To design an efficient polling scheme, the point coordinator (PC) needs to obtain information about the current transmission status and channel condition for each station. To reduce overhead caused by polling frames, it is better to poll all stations using one polling frame containing the transmission schedule. In this paper, we propose an efficient polling scheme, referred to as two-step multipolling (TS-MP), for the PCF in wireless local area networks (WLANs). In this new scheme, we propose to use two multipolling frames with different purposes. The first frame is broadcast to collect information such as the numbers of pending frames and the physical-layer transmission rates for the communication links among all stations. The second frame contains a polling sequence for data transmissions designed based on the collected information. This frame is broadcast to all stations. Extensive simulation studies show that TS-MP not only overcomes the aforementioned deficiencies, but also help to implement rate adaptation over time-varying wireless channel.     

Performance evaluation of a reservation TDMA protocol forvoice/data transmission in microcellular systems

This paper deals with a random reservation TDMA protocol able to support constant bit rate services as well as variable bit rate services. In particular, voice communications and data transmissions are considered. Voice terminals have a higher priority assigned than data terminals in accessing the shared channel. A suitable analytical approach is proposed in order to evaluate the data and voice subsystem performance. Comparisons to the well known PRMA scheme are also given in order to highlight the superior performance of the proposed approach in terms of maximum data load and overall throughput     

一种具有QoS保证的无线分组调度算法

为提高系统吞吐量对指数规则（EXP-rule）调度算法进行了改进。改进的指数规则（WEXP-rule）算法根据各移动用户收发信道质量和业务传输的QoS要求动态调整各用户的业务传输优先级,确定下行共享信道的调度方案。并给出该算法的简化形式SWEXP-rule。仿真结果表明,与传统调度算法相比,SWEXP-rule算法在数据包传输时延受限的条件下具有无线信道利用率高、实现复杂度低等特点。     

Call admission control for voice/data integrated cellular networks: performance analysis and comparative study

In this paper, we propose a new call admission control scheme called dual threshold bandwidth reservation, or DTBR scheme. The main novelty is that it builds upon a complete sharing approach, in which the channels in each cell are shared among the different traffic types and multiple thresholds are used to meet the specific quality-of-service (QoS) requirements. We present a detailed comparative study based on mathematical and simulation models, and quantitatively demonstrate that the DTBR is capable of providing the QoS guarantee for each type of traffic, while at the same time leading to much better channel efficiency. We further show that the DTBR scheme with elastic data service can offer both service guarantee and service differentiation for voice and data services, and enhance the bandwidth utilization.     

A preemptive polling protocol for applications in wireless LANs

This paper deals with a radio‐based communication network with a single radio channel shared by several data terminals for transmissions to a single hub station. In particular, the communication system considered is a potential provider of wireless LAN‐like services. The focus is on the capacity of combining a preemptive polling‐based multiple access scheme with a Selective Repeat ARQ technique to counteract the effect of the nonstationary transmission channel. The nonstationary transmission channel has been modeled as a two‐state Markov chain with parameters related to actual propagation conditions. Typical outdoor/indoor environments have been considered. The main idea is that of making the service interruption of the preemptive polling scheme dependent on the propagation conditions of the transmission channel by monitoring the outcome of the data packet transmission attempts. A performance comparison clearly reveals the superiority of this preemptive polling scheme with respect to the classical cyclic polling scheme. This revised version was published online in June 2006 with corrections to the Cover Date.     

Performance analysis of wavelet packet multirate multicarrier multicode CDMA for wireless multimedia communications

Different kinds of Multirate (MR) communication systems, such as multicode (MCD) scheme and variable spreading length (VSL) schemes, have been considered for accommodating information sources with different data rates in Multicarrier code-division multiple access (MC-CDMA). In this paper, we propose the use of MCD scheme for MR services in MC/MCD-CDMA system that employs wavelet packets (WPs) as subcarriers. The bit error rate (BER) performance for the system was investigated by means of analytical methods and numerical results in a slow fading frequency selective Nakagami channel. The performance analysis includes the effects of diversity techniques, channel intensity profile, diversity order and fading parameter. Also, the effects of different service rates and number of users in each service rate were investigated. The performance of the system was compared to that of MC/MCD-CDMA based on sinusoidal carrier. Results reveal that BER performance is proportional to the service rate and our proposed system outperform the other system.     

A spare bandwidth sharing scheme based on network reliability

Spare bandwidth is required for recovering the network service from network faults. However, it degrades the efficiency of network utilization. Spare bandwidth demand can be reduced significantly by letting spare bandwidth be shared among several network services. Spare bandwidth reserved on a network element can be shared by a set of network services for a network fault if they are not simultaneously affected by the network fault. A new, and more practical spare bandwidth sharing scheme, which is based on the network reliability, is proposed in this paper. In the proposed scheme, multiple link failures are allowed with a given link failure rate, and a reasonable restoration level of near 100%; while in the conventional scheme, only a single link failure, and 100% restoration level are considered. To develop the spare bandwidth sharing scheme, we first investigate the framework for evaluating the reliability of path-based network services, and then we explain the proposed spare bandwidth sharing scheme with decision parameters such as lifetime of the path, restoration level, and the maximum number of working paths which can be protected by a backup link. Simulation results show that the proposed spare bandwidth sharing scheme requires a smaller amount of spare bandwidth than the conventional scheme.     

A priority scheme for the IEEE 802.14 MAC protocol for hybridfiber-coax networks

In order to support quality-of-service (QoS) for real-time data communications such as voice, video and interactive services, multiaccess networks must provide an effective priority mechanism. The context of this work is the IEEE 802.14 standard for hybrid fiber coaxial (HFC) networks which has a shared upstream channel for transmissions from stations to the headend. This work presents a multilevel priority collision resolution scheme, which separates and resolves collisions between stations in a priority order, thereby, achieving the capability for preemptive priorities. We present a set of simulation scenarios which show the robustness and efficiency of the scheme, such as its ability to isolate higher priority traffic from lower priorities and to provide quick access to high-priority requests. In March 1998, a framework for handling priorities in the collision resolution process, which adopts a semantics similar to the semantics of our scheme, was included in the 802.14 standard     

Adaptive Transmission Scheme for Mixed Multicast and Unicast Traffic in Cellular Systems

Wireless communication systems have been developed to support users' various requirements. Multicast and unicast transmission schemes are proposed for various types of services. The multicast transmission is known as an efficient method for group-data transmission. The data rate for multicast transmission depends on the instantaneous worst channel user. On the other hand, unicast transmission exploits wireless channel variation and achieves a multiuser diversity gain. In this paper, we evaluate and compare the system performance of multicast and unicast transmission schemes in terms of system capacity, worst average channel user's capacity, and outage probability for varying cell environments. We also propose a novel hybrid scheduling scheme for mixed multicast and unicast traffic services and compare the proposed scheme with the conventional scheme.