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对IEEE 802.16网络点对多点模式的带宽分配过程进行分析,讨论在不同可用带宽情况下WiMAX网络中各种数据流通过用户站向基站请求带宽资源的过程以及基站和用户站对网络中的不同数据流的带宽请求进行处理的情况.在此基础上,提出一种分析WiMAX网络按用户站集中分配带宽资源的马尔可夫模型.该模型使用多重队列的方式分析了基站和用户站的运行情况,提供了在不同网络配置情况下或者使用不同带宽分配算法时网络中各种数据流的阻塞概率,为分析WiMAX网络带宽资源分配过程和优化网络参数设置提供帮助. 相似文献
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在轮询带宽调度和随机带宽调度两种经典算法的基础上,提出一种基于多面体优先列表的带宽资源调度算法来分析和优化WiMAX网络Mesh模式的带宽请求和调度过程.该算法通过为各个用户站构建不同的静态优先请求次序,避免或者减少了"带宽资源分配不均"现象,使带宽资源能够在网络局部得到优化调度,并扩展到整个无线网络.分析和仿真结果表明,本算法能够极大地改善整个网络的运行性能. 相似文献
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针对分簇Ad Hoc网络中固定时隙分配算法信道资源浪费和竞争时隙分配算法传输延迟不固定的问题,提出一种基于时分多址接入的无冲突动态时隙分配算法。该算法根据网络负载动态调整帧长,即当网络负载增大时,增加帧长,提高信道利用率;当网络负载减小时,减少帧长,降低信道申请时延。仿真结果表明,与NEBS算法和时隙ALOHA算法相比,该算法可根据网络负载动态调整资源分配,从而提高系统的吞吐量。 相似文献
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在802.11协议中,DCF(Distributed Coordination Function)机制是节点共享无线信道进行数据传输的基本接入方式,为了解决无线网络中隐藏节点问题,使用RTS/CTS机制减少冲突,然而当网络节点数增加时,节点传输的冲突次数亦增加,从而使网络性能明显下降。因此,需要设计新的MAC协议,以适应当前Ad Hoc网络应用的快速发展。在IEEE 802.11的分布式协调功能访问机制(DCF)基础上,本文设计新的节点合作式的网络协议(C-MAC)。C-MAC节点通过控制帧获得本节点2跳内的邻接节点信息,并且根据邻接节点的信息设计调度算法,使节点以轮询的合作方式传输数据,有效地避免冲突。仿真实验表明,在改变节点速率、帧长度、网络节点数等参数情况下,分别以吞吐量、单帧传输时间和公平性为指标,对DCF和C MAC协议进行性能比较。在节点传输速率为11Mbps时,C MAC协议吞吐量比标准DCF最多可增加50%。 相似文献
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车地通信系统对帧传输的实时性要求较高。为了提高车地通信系统帧传输的时延性能,针对车地通信系统中多个外置天线的信号的部分可预测性特点,文中提出一种帧请求调度的新算法一最早离开算法。在车地通信系统中,多个外置天线的RSSI值之间是一种单向平移的关系,最早离开算法充分利用了这种平移性,在帧到达的时刻预测帧在每个外置天线上的离开时刻,从而选择最早处理完的外置天线进行帧传输。仿真结果表明,最早离开算法的传输时延性能优于现有的请求调度算法。 相似文献
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数据密集型应用通常需要在广域网分布式共享计算环境中高效地传输海量数据。并行处理中,大量的数据需要在生成集群、存储集群、处理集群间进行传输。针对该传输问题提出了一个支持多集群数据并行传输的按需文件传输算法(On-demand File Transfer),该算法以批量传输请求的整体完成时间最小为目的,根据集群内部快速传输的特点,实现目的端并行,分散单个节点的传输负载;在传输路径上,采用多重路径和多跳路径分割方法实现并行传输。对于批量传输请求,依据每个请求的传输负载,全局按需分配带宽,以解决传输路径的带宽冲突,从而充分利用当前网络带宽,快速传输批量传输请求。 相似文献
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一种可选择最佳带宽的多路路由算法 总被引:1,自引:0,他引:1
实现服务质量保证,在多用户、多请求接入的网络中都是采取为相应请求预留资源的方式,而多请求预留资源使得网络局部出现资源"碎块".单路路由算法不能利用这些资源接入用户请求.为提高网络的资源利用率,采用多路路由方法,在单一通路不能满足连接请求要求时,寻找多条能联合满足要求的一组虚拟不相交并路,并预留资源共同满足用户的服务质量要求.为验证算法的有效性,在ns2模拟器上实现了所提出的算法,并与其他算法进行了性能比较.实验结果表明,提出的算法能很好地适应网络运行状况.在网络轻负载情况下,通信开销小.在网络重负载情况下,使用并行多路增加连接请求的接通率.将此算法应用于支持服务质量保证的多媒体数据网,能充分利用有限的网络资源,提高传输多媒体信息的能力. 相似文献
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The IEEE 802.16e standard enhances the IEEE 802.16 for the mobility support. Mobile stations can move while receiving services,
thus ongoing IP sessions may be maintained during a handover in the IEEE 802.16e. To reduce handover latency, the idea of
cross-layer handover which incorporates layer 2 handover with IP layer has been devised. Various cross-layer handover schemes
supporting fast handover in the IEEE 802.16e networks have been proposed. However, the problem of the conventional cross-layer
fast handover schemes is that they are heavily influenced by the new address confirmation latency which is the most time-consuming
procedure. In this paper, we propose an enhanced cross-layer fast handover scheme which is not susceptible to the new address
confirmation latency. Detailed performance analysis is performed in terms of the signaling costs and the handover latencies
to show the effectiveness of the proposed scheme compared with the conventional ones. The results of the performance evaluation
confirm the effectiveness of the proposed scheme. 相似文献
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To avoid collisions in WiMAX networks, the connections in Subscriber Stations (SSs) use a request–grant process to acquire transmission resources from the Base Station (BS). In accordance with the IEEE 802.16 standard, the request–grant process is accomplished using either a unicast polling method or a contention request method. In WiMAX systems, the number of bandwidth-request (BR) slots per frame is limited. Thus, to enhance the network performance, the BR slots must be used in the most efficient manner possible. In practical WiMAX systems, the offered network load varies over time, and thus the strict use of either the unicast polling method or the contention request method results in a poor utilization efficiency of the BR slots. Accordingly, the present study proposes a scheme designated as Efficiency-Driven Selection of Bandwidth Request (EDSBR), in which the request–grant mechanism is adjusted dynamically on a frame-by-frame basis in accordance with the network conditions. The performance of the proposed scheme is evaluated by simulations. The results show that EDSBR achieves a more efficient utilization of the BR slots than the unicast polling scheme or the contention request scheme, and therefore yields an improved network performance. 相似文献
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Sheng-Shih WangAuthor VitaeChan-Ying LienAuthor Vitae Wen-Hwa LiaoAuthor VitaeKuei-Ping ShihAuthor Vitae 《Computers & Electrical Engineering》2012,38(4):953-962
For coverage extension and throughput enhancement, the IEEE 802.16j task group has developed a novel multi-hop relay network architecture to enable typical IEEE 802.16 networks to achieve data transmission between base stations and mobile stations via a multi-hop path with relay stations deployment. How to determine an effective path for throughput gain and overhead reduction is emerging and crucial in IEEE 802.16 multi-hop relay networks. This paper introduces a load-aware spectral-efficient routing metric, called LASER, to evaluate paths, and proposes an efficient scheme to determine a proper path. Based on the LASER metric, the proposed path selection scheme formulates the path cost as the summation of cost of each link, and the path with the minimum cost will be selected as the appropriate one. Simulation results show that the proposed LASER-based path selection scheme significantly outperforms existing path selection schemes in network throughput and map overhead. 相似文献
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IEEE802.16e协议给出的LDPC码是短码时,其校验矩阵存在大量的短环,针对这一问题,设计了一种新的LDPC缩短码方案。该方案在现有的IEEE802.16e标准的LDPC码的校验矩阵设计框架下,提出了一种分块修正子校验矩阵的设计方案,这种方案用准循环矩阵和有限几何法联合优化的方法构造了扩展因子zf=48的校验矩阵,运用同步顺序搜索度数节点的方式,使缩短码情况下的校验矩阵无4环并且仅含有少量6环。在AWGN信道下仿真实验表明,码率为0.5的情况下,改进后的码字不仅保持了IEEE802.16e标准编码的快速编码性能,并且误码率仅比此时的香农限多了1.1dB 相似文献
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《Computer Networks》2007,51(8):2049-2066
In this paper, we investigate the characteristics of IEEE 802.16 and conclude that it is better to equip BS (base station) and SS (subscriber station) with Layer 3 functionality. Therefore, an 802.16 network can act as the backbone network of different subnets for better deployment. Based on the two IEEE Specifications, 802.16-2004 and 802.16e, we propose two kinds of paradigms of the 802.16 network technology for mobile networking. In the first paradigm, a novel concept called middle-domain mobility management in between macro- and micro-domain for 802.16-2004 is proposed. The management scheme of middle-domain is designed to accommodate different micro-mobility protocols in an 802.16-2004 network environment. Moreover, a mathematical analysis and simulation study are presented for performance evaluation. In the second paradigm, by comparing with traditional overlay networks (e.g. GPRS/WLAN), we have found that the characteristics for the 802.16e/802.11 overlay network are actually different from traditional overlay networks. To provide more efficient vertical handoff, a novel protocol called speed-based vertical handoff scheme (SVH) is proposed. A Simulation study has demonstrated that SVH can achieve a better performance than its WLAN-first counterpart in terms of less signaling and fewer packet losses. 相似文献
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The IEEE 802.16(d) mesh coordinated distributed scheduling (CDS) mode is a novel technology for future fixed wireless backbone networks and designed for the use of omnidirectional antennas. The use of Single-Switched-Beam Antennas (SSBAs) may have great potential to increase network capacity due to the antenna directivity. However, a network designed for omnidirectional antennas usually cannot operate well or achieve good performance with the presence of antenna directivity.In this paper, we review the designs of the IEEE 802.16 mesh CDS-mode network, study the issues of this network with the use of Single-Switched-Beam Antennas (SSBAs), and propose a complete solution to solve these issues. The performances of our proposed scheme is evaluated using simulations. The simulation results show that our proposed scheme can effectively solve the issues of using SSBAs in the IEEE 802.16 mesh CDS-mode network and greatly increase its network capacity. 相似文献
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N. Sai Shankar 《Journal of Scheduling》2004,7(2):149-167
Bidirectional Cable TV networks using hybrid fiber coaxial (HFC) systems are good examples of broadcast environments where a contention resolution algorithm is needed in order to allocate the multiaccess medium among various customers. The medium access control (MAC) scheme, proposed by DAVIC/DVB, IEEE 802.14 and DOCSIS for the upstream channel of HFC access networks is based on a mixable contention-based/contentionless time slot assignment. Contention-less (CL) slots are assigned by the head-end (HE) to end stations according to a reservation scheme. Contention-based slots (CB) are randomly accessed by active terminals without any prelimanry allocation and so collisions may occur. To resolve contention the contention tree algorithm has been widely accepted by the DVB/DAVIC, IEEE 802.14 and DOCSIS standards for MAC because of higher throughput and lower access delay. In this paper we propose a simple modification to the existing protocol and analyze its performance. We propose to have one slot in the frame exclusively reserved for the new arrivals that wish to access the channel capacity using contention resolution and atleast one more slot reserved for resolving their contention if there was a contention in the arrival slot. This assumption simplifies the protocol to a queuing mechanism and we use the results of the queue to analyze the protocol. The queuing analysis method is used to determine the throughput of the channel and waiting times of the arbitrary customers. Furthermore, we present numerical results and compare that with simulations. 相似文献