IEEE802.11a WLAN中DCF性能分析

引入二维马尔科夫模型,对DCF的两种传输方式:基本接入方式和RTS/CTS方式,在IEEE802.11a WLAN中的饱和吞吐量和传输时延性能进行了理论分析和仿真,理论分析和仿真结果表明,与低速IEEE802.11WLAN中的情况相反,在IEEE802.11a WLAN中,基本接入方式在多数情况下比RTS/CTS方式更有效.     

Performance Analytical Model of IEEE 802.11 Distributed Coordination Function

IEEE 802.11 distributed coordination function （DCF） is a distributed medium access scheme based on carrier sense multiple access with collision avoidance （CSMA/CA） protocol. Many literatures have analyzed the performance of IEEE802.11 DCF. However, such literatures either used simulation methods or built the analytical models under the assumption that the saturation condition was satisfied. To overcome such a problem, in this paper, a hi-dimensional Markovian model has been introduced to depict the DCF mechanism. The proposed model introduced an idle stage and a discrete time M/G/1 queue to deduce the channel throughput under finite load traffic. Simulation results proved the accuracy of the proposed model.     

DGPS for outdoor mobile Robots by a wireless LAN

With the cancellation of SA in 2000, the precision of GPS has been improved, widening the field of GPS applications. This range of applications includes the measurement of the position of mobile robots. Because the precision of point positioning by GPS is approximately 22mCEP, positioning such objects as automatically controlled oil tankers can be done with good results. However in the case of mobile robots the size of a human, point positioning does not provide enough precision. But with a differential system, utilization involves obtaining information through radio networks, and international agreements written into law determine the radio frequencies that are permitted for use by citizens. For that reason the selection of radio equipment is a very difficult problem for DGPS. In Japan one radio system attracting attention recently is the wireless LAN System, using IEEE802.11b. It is on the 2.4 GHz band, which is available without license, and functions on TCP/IP protocol. This report describes the experimental results of position measurement for a mobile robot using a wireless LAN to send data from a reference station to the robot. We examined what radio transmissions could be used effectively by the LAN.     

802.11 DCF中优化吞吐率的RTS门限调整算法

针对IEEE 802.11 DCF网络,提出了优化吞吐率的RTS门限分布式调整算法.通过分析一次成功发送和一次碰撞持续的平均时间,找到网络饱和吞吐率与RTS门限的关系.分析显示,存在一个最佳RTS门限,使得网络的饱和吞吐率最大.从一次发送过程平均时间最小化出发给出了求解最佳RTS门限的数值计算方法,然后,设计出一个分布式算法,以使终端能自动调整其RTS门限到最佳值,从而优化网络的饱和吞吐率.计算机仿真证明了该分布式算法的有效性.     

一种CFP 40G/100G光模块物理层的测试方法

针对CFP 40G/100G光模块物理层测试需要,文章介绍了一种基于IEEE 802.3BA协议的测试方案。该测试方案利用泰克BertScope示波器测试平台,制作CFP测试夹具把CFP 40G/100G光模块高速电信号引出来,实现了对CFP 40G/100G光模块接收端和发送端物理层电信号的测试。通过对Finisar公司的CFP 40G和CFP 100G光模块发送端有源眼图、光模块接收端眼图及接收端芯片抖动的测试,验证了该测试方案的可行性。     

一种适合IEEE802.16m的改进前导字结构和定时同步算法

结合IEE802.16m协议分析了定时同步误差对系统性能的影响.通过对同步训练序列及传统定时同步算法的分析,提出了一种适合IEEE802.16m系统的定时同步方案.该方案利用训练序列的相关性,通过改进前导字结构及同步算法实现接收端的定时同步.在高斯信道和SUI-3信道下进行了仿真.结果表明,改进的定时同步方案优于传统方...     

基于OMNeT++的WiMAX协议仿真设计

基于IEEE802.16标准,在OMNeT++仿真平台上设计并验证了WiMAX仿真模块。仿真模块实现了IEEE802.16标准定义的主要功能,包括用户终端注册,服务流建立和带宽请求与分配机制。仿真模块的实现为以后进一步研究WiMAX提供了基础。     

Improved MIMO-OFDM scheme for the next generation WLAN

The research and application of wireless local area networks (WLAN) technology are in a stage of rapid development. It has been one of research focuses of the wireless communications field. Through the use of enhanced single-user (SU)/multi-user (MU) multiple input multiple output (MIMO)-orthogonal frequency division multiplexing (OFDM) technology, the next generation WLAN IEEE 802.11ac dramatically increases the throughput. An improved MIMO-OFDM scheme based on modulation diversity is proposed for the next generation WLAN. It uses two-dimensional modulation diversity to the current IEEE 802.11ac transmission scheme. Through the space-time-frequency component interleaver and the rotational modulation, the proposed scheme exhibits high spectral efficiency and low error rate in fading channels. The simulation results show that the proposed scheme significantly outperforms the SU/MU MIMO-OFDM scheme in the current IEEE 802.11ac standard, which is up to 5 dB.     

IEEE 802.11e无线网络协议标准中增强分布式协调功能(EDCF)性能分析

从理论上分析了IEEE802.11e协议中EnhancedDistributedCoordinationFunction(EDCF)的性能。目前,EDCF作为实际实现中的标准接入机制而成为研究的热点,已有大量文献分析了EDCF中参数的选择及其对网络性能的影响。但是在以前的工作中对使用TransmissionOpportunity(TXOP)时以及非理想信道条件下EDCF系统的性能分析却很少。文章的主要工作就是从理论上分析了采用TXOP以及考虑信道误码时EDCF的性能。     

Mesh模式的IEEE 802.16系统的带宽调度研究

研究了IEEE 802.16在mesh模式下的带宽调度策略,提出了分层调度模型.以调度开销最小为原则得出链式拓扑存在最优调度分界,证明了可以分解成链式拓扑集合的任意mesh网络调度也存在最优分层.给出了mesh最优分层的解,并分析了BS覆盖范围对分层的影响.数值仿真结果显示了分层带宽调度明显降低了调度需要的开销和跳数.