基于NS2的IEEE 802.16 Mesh模式的功能模型与仿真*

IEEE 802.16定义了无线城域网物理层（PHY）和媒质接入控制层（MAC）标准,其MAC支持点到多点和Mesh两种模式。为了满足Mesh模式网络研究中可扩展仿真平台的需要,根据IEEE 802.16—2004标准提出了基于NS2的Mesh模式功能仿真模型。该模型将Mesh模式的物理层和媒质接入控制层的必要功能分成相对独立的几个功能模块,每个模块都可以在NS2仿真中用面向对象的C++类实现其功能,具有很好的可扩展性。基于该模型,扩展了NS2,实现了Mesh模式的协调分布式调度功能和算法。通过建立仿真环     

一个提高WiMax服务质量的带宽分配调度算法研究

随着接入网络作为连接用户终端与核心网络的纽带的倍受关注,用户越来越关注数据传输的QoS(服务质量)问题。在IEEE802.16协议的MAC层定义了比较完善的QoS机制。但QoS机制中的核心问题,带宽调度算法,协议没有作出明确的阐述和定义。该文在已有典型算法基础上,吸收、采纳了已有算法中适合于IEEE802.16协议的带宽调度的方法,并结合IEEE802.16协议关于QoS的定义,提出了一个针对IEEE802.16协议的PMP(点对多点)模式下集中式的带宽分配调度算法。并在NS2模拟环境下对算法进行了测试。     

802.16 Mesh模式下提供QoS保障的调度算法

无线Mesh网络是一种多跳分布式自组织网络。提出了一种IEEE 802.16 Mesh模式下的分布式QoS保障调度算法。该算法充分利用方向性天线带来的空分复用增益,并采用DiffServ机制保证QoS需求。仿真结果表明,所提算法不仅提高吞吐量,而且能够为不同类型的服务提供QoS保障。     

IEEE 802.16 Mesh模式下基于QoS的时隙分配算法

IEEE 802.16-2004标准定义了Mesh模式下的调度机制，基于这些调度机制下的数据信道资源分配算法，在标准中没有详细规定。该文提出了两种基于优先级的时隙分配算法，以实现MAC层的QoS，通过仿真分析了平均分组延迟、请求失败率和时隙利用率。仿真结果表明这些算法实现了对不同需求的业务流的QoS保障。     

支持QoS的无线Mesh网络协同分布式调度算法

无线Mesh网作为下一代宽带无线通信网络的关键技术之一受到越来越多的关注.针对现有无线Mesh网MAC层调度算法的不足,提出一种基于TDMA模式的支持QoS的协同分布式调度算法(CDS-QoS:Coord inated Distributed Schedu ling-Quality of Service).算法的核心思想是在本次发送控制消息的同时预测下一次发送的时机,并告知其他节点,在预测的同时保证节点的QoS,对不同业务流进行有区分的调度.实验结果表明,CDS-QoS算法具有较高的时效性,并且能够有效保证不同多媒体业务的QoS.     

WiMAX Mesh网络混合调度下的QoS保障

在WiMAX Mesh网络中,资源分配可由集中式和分布式2种调度机制完成,但多数QoS研究只针对一种调度机制。针对上述情况,提出结合2种调度机制的QoS保障机制CDCSQ,针对不同的服务采用不同的调度机制以改进QoS,其中,集中式调度用于保证实时服务,分布式调度确保Mesh内部节点的直接通信。模拟结果表明,该机制比IEEE 802.16标准中的服务延迟小。     

基于忙音多址的多信道无线Mesh网的MAC协议

无线Mesh网（WMN）是一种新型宽带无线接入技术,选择适当的MAC子层规范,根据网络业务特征有效地配置信道资源,可以提高Mesh网的无线资源使用效率以及系统传输性能。而现有的无线Mesh网络基本上是采用单信道MAC协议,不能满足日益俱增的用户需求,限制了整个网络的数据传输速率与网络容量。文中基于忙音多址访问的设计思想,结合无线Mesh网络的特点,提出了一种无线Mesh网MAC协议MCBTMA（Multi-Channel Busy Tone Multiple Access）。MCBTMA通过构建多个忙信号控制信道和多个数据信道,在MAC层进行多信道调度,使无线Mesh网络在吞吐量和时延方面性能有显著提高。     

基于IEEE 802．16的QOS研究

在固定宽带接入系统中,如何为具有不同QOS要求的多种类型业务流提供服务质量(QOS)保证是一个很重要并且很有挑战性的课题。尽管IEEE 802.16 MAC协议支持对各种类型应用的QOS保证,但是它没有给出具体的流调度方案来实现QOS要求。要为各种应用提供不同级别的QOS并且保证较高的系统吞吐率,必须在此MAC协议中集成一个QOS架构。这篇论文针对应用于802.16 MAC协议中的QOS架构进行深入的讨论和研究。     

基于忙音多址的多信道无线Mesh网的MAC协议

无线Mesh网(WMN)是一种新犁宽带无线接入技术,选择适当的MAC子层规范,根据网络业务特征有效地配置信道资源,可以提高Mesh网的无线资源使用效率以及系统传输性能.而现有的无线Mesh网络基本上是采用单信道MAC协议,不能满足日益俱增的用户需求,限制了整个网络的数据传输速率与网络容量.文中基于忙音多址访问的设计思想,结合无线Mesh网络的特点,提出了一种无线Mesh网MAC协议MCBTMA(Multi-Channel Busy Tone Multiple Access).MCBTMA通过构建多个忙信号控制信道和多个数据信道,在MAC层进行多信道调度,使无线Mesh网络在吞吐量和时延方面性能有显著提高.     

无线传感器网络TDMA MAC协议的对比和改进研究

无线传感器网络MAC协议对网络的生命期有着重要影响,为找到适合一定环境所使用的MAC协议,必须对不同的MAC协议进行必要的分析。从数据帧着手,分析了不同的基于TDMA的调度式MAC协议的差异。针对原有TDMA MAC协议数据传输量不高、实现难度大等问题,提出相应的改进方法,并对三个基于LEACH的TDMA MAC协议进行了仿真实现,仿真结果与数据分析的结果一致。     

IEEE 802.16 Mesh模式下区分服务时隙调度算法

为了满足用户需求,IEEE802.16支持多种QoS。在IEEE802.16-2004定义的mesh模式的调度机制下,针对实时业务和非实时业务对时延具有不同敏感性的特点,提出了一种区分服务的时隙调度算法。该算法优先处理实时业务,并通过拥塞情况,自适应地调整实时业务的预留带宽。最后对算法进行了仿真,结果表明该算法下业务的延迟、服务请求拒绝率、时隙利用率均有所改善。     

基于IEEE802.16d PMP网络的业务调度研究

研究无线城域网PMP网络结构TDD模式下媒质接入机制和MAC层调度机制.通过对截断二进制指数算法的研究给出上行调度碰撞解决机制的一种实现方案,在保证QoS要求的同时最优地利用了动态分配的带宽.最后使用NS网络仿真软件对此进行了仿真,给出了UGS和rtPS调度业务数据仿真的结果.     

A performance study of uplink scheduling algorithms in point-to-multipoint WiMAX networks

The IEEE 802.16 standard defines the specifications for medium access control (MAC) and physical (PHY) layers of WiMAX networks. A critical part of the MAC layer specification is packet scheduling, which resolves contention for bandwidth and determines the transmission order of users. Evaluating the performance packet scheduling algorithms is of utmost importance towards realizing large-scale WiMAX deployment. In this paper, we conduct a comprehensive performance study of scheduling algorithms in point-to-multipoint mode of OFDM-based WiMAX networks. We first make a classification of WiMAX scheduling algorithms, then simulate a representative number of algorithms in each class taking into account that vital characteristics of the IEEE 802.16 MAC layer and OFDM physical layer. We evaluate the algorithms with respect to their abilities to support multiple classes of service, providing quality of service (QoS) guarantees, fairness amongst service classes and bandwidth utilization. To the best of our knowledge, no such comprehensive performance study has been reported in the literature. Simulation results indicate that none of the current algorithms is capable of effectively supporting all WiMAX classes of service. We demonstrate that an efficient, fair and robust scheduler for WiMAX is still an open research area. We conclude our study by making recommendations that can be used by WiMax protocol designers.     

An efficient bandwidth allocation algorithm for real-time VBR stream transmission under IEEE 802.16 wireless networks

This paper investigates variable rate control strategies for real-time multimedia variable bit rate (VBR) services over IEEE 802.16 broadband wireless networks. A data rate control mechanism is derived for the case where the uplink channel provides real-time services and the traffic rate parameter remains constant. This paper shows that the common queuing scheduling algorithms have some bandwidth allocation fairness problems for the real-time polling service (rtPS) in the MAC layer. In other words, the use of a VBR for the rtPS by a WiMAX system results in additional access latency jitter and bandwidth allocation disorder in the transmitted multimedia streams during the regular time interval polling of subscribe stations (SSs) for the contention bandwidth request period. However, the proposed scheduling algorithm solves these SSs contending with bandwidth resource allocation problems based on an extended rtPS (ertPS) of quality-of-service (QoS) pre-programming for a ranging response non-contention polling period. The adopted bandwidth allocation of max–min fairness queue scheduling uses a time constraint condition to transmit real-time multimedia VBR streaming in an IEEE 802.16 broadband wireless environment. In addition, we use the ns-2 simulation tool to compare the capacity of multimedia VBR stream and show that the proposed ertPS scheduling algorithm outperforms other rtPS scheduling algorithms.     

Relay technologies and technical issues in IEEE 802.16j Mobile Multi-hop Relay (MMR) networks

An amendment to the 802.16e standard namely IEEE 802.16j specifying relay station (RS) and multi-hop relay base station (MR-BS) was approved in year 2006 supports Mobile Multi-hop Relay networks. (MMR). It provides coverage extension to isolated area and throughput enhancement by specifying relay stations. The physical (PHY) layer of WiMAX IEEE 802.16j standard is based on the IEEE 802.16-2004 and IEEE 802.16e-2005 standards and was designed from IEEE 802.11a. This paper reviews the Relay technologies and technical issues in the physical and MAC layer of IEEE 802.16j such as Data forwarding schemes frame structure, Link adaptation, modulation and coding, these issues belongs to physical layer, QoS scheduling services, Bandwidth allocation and request, Network planning, MAC handover procedures, connection management, path management, interference management, all these issues belongs to MAC layer.     

IEEE802.16e的实时上行链路调度服务优化算法

深入分析了IEEE802.16e建议的三种实时调度服务算法：UGS、rtPS、ertPS，并在此基础上提出了一种优化的实时调度服务算法：irtPS。该优化的调度服务算法在保证变化数据率实时上行链路的延时性能基础上，最大限度地提高了实时上行链路的资源利用率。数学建模分析结果显示，在保证延时性能的前提下，该优化的调度服务算法的系统容量较IEEE802.16e建议算法的系统容量有显著增加。     

Scheduling solution for the IEEE 802.16 base station

The IEEE 802.16 standard defines a wireless broadband access network technology called WiMAX. It introduces several advantages, one of which is the support for QoS at the MAC level. To ensure meeting the QoS requirements, the 802.16 base station must run some algorithm to allocate slots between connections. This algorithm is not defined in the 802.16 specification but rather is open for alternative implementations. We propose a simple, yet efficient, solution that is capable of allocating slots based on the QoS requirements, bandwidth request sizes, and the 802.16 network parameters. To test the proposed solution, we have implemented the 802.16 MAC and PHY layers in the NS-2 simulator. Several simulation scenarios are presented that demonstrate how the scheduling solution allocates resources in various cases. According to the simulation results, the proposed scheduling solution ensures the QoS requirements of all 802.16 service classes. The solution shares free resources fairly and demonstrates work-conserving behaviour.     

IEEE 802．16协议中上行带宽分配机制研究

802.16是新一代宽带无线接入的标准。标准中明确定义了在MAC层实现QoS的机制,例如:MAC层的通信是基于连接的;将上层业务流根据QoS的要求进行分类等。但是标准对上行带宽的分配机制却未加以定义。我们就这个问题进行了研究,并提出了一种有效的上行带宽分配机制。