摘要IEEE工作组为无线局域网设置了802.11协议标准，包括从物理层(PHY)到媒体接入控制层(MAC)的相关规定。MAC层是无线局域网的重要结构层，它的基本接入控制协议是分布协调功能(DCF)，可选的接入控制协议是点协调功能(PCF)。DCF共有两种数据传输方式：基本接入机制和RTS/CTS接入机制，这两种机制均采用基于二进制指数退避的载波侦听多址接入/碰撞退避(CSMA/CA)算法来避免数据碰撞。吞吐量和时延是无线局域网最重要的两个性能，可以使用二维Markov模型对它们进行计算，该模型同样适用于两者的混合接入机制。随后可以运用NS-2软件对两者进行仿真，从而验证模型的可行性。本文重点讨论了基本接入机制、RTS/CTS接入机制和混合接入机制对吞吐量及时延的影响，除此之外，还涉及到对RTS/CTS阈值的计算。60086

关键词:分布协调功能；基本接入机制；RTS/CTS接入机制；混合接入机制；吞吐量；时延

毕业设计说明书（论文）外文摘要

Title    The  Performance  Analysis  Of  WLAN  Protocol                     

Abstract

The IEEE has standardized the 802.11 protocol for Wireless Local Area Networks,which ranges from rules for physical layer(PHY) and medium access control(MAC).MAC layer is one of the most important structures for WLAN, the primary access control protocol for it is called distributed coordination function(DCF),and the optional one is called point coordination function(PCF). DCF consists of two kinds of data transmission techniques:the basic access scheme and the RTS/CTS access scheme,and both of them use the carrier sense multiple access with collision avoidance (CSMA/CA) scheme based on the binary slotted exponential backoff to avoid data collision.Throughput and delay are the most important performances of WLAN,which can be calculated through a two-dimensional Markov model,the model is also appliable to the combination of them.Then,we can simulate with the NS-2 software to prove the practicality of the model.Threshold of the RTS/CTS access mechanism and the MAC layer is also discussed in this paper,thus the influence of both two access mechanism and the related parameters to the network throughput is carried out.

Keywords : DCF;The basic access scheme;The RTS/CTS access scheme;The hybrid access scheme; throughput;delay

目   次  

1  引言 1

1.1  无线局域网协议的简单介绍 1

1.2  研究手段 3

1.3  本次毕业设计将要完成的工作 4

2  WLAN的两种接入控制机制 5

2.1  分布协调功能DCF 5

2.2  点协调功能PCF 8

3  运用Markov链进行吞吐量性能的分析 8

3.1  Markov模型 9

3.2  吞吐量和时延的理论推导 11

4  系统仿真 13

4.1  仿真软件和系统参数的选定 13

4.2  吞吐量和时延的仿真结果 14

5  变包长对吞吐量的影响 16

5.1  混合接入机制机制的启动阈值 17

5.2  变包长下吞吐量与时延的变化情况 20

5.3  变包长下吞吐量与时延的仿真结果