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1、华中科技大学 硕士学位论文 无线局域网中的接入点放置与信道分配 姓名：蒂达希妮 申请学位级别：硕士 专业：信息与通信工程 指导教师：葛晓虎 2010-05-20 华华 中中 科科 技技 大大 学学 硕硕 士士 学学 位位 论论 文文 II 摘摘 要要 无线通信通常要求增加带宽、覆盖范围和数据传输速率，减小干扰和降低成本。 目前， 大量基于无线局域网的 AP 因为用户的移动性而性能降低，提供的数据吞吐总 量往往小于理想值。 设计 802.11 无线局域网包括两个主要部分：AP 在服务区内的放置，每一 AP 的 频率分配。当在服务区内放置 AP 时，覆盖范围和容量是关键因素，通常 AP 需要覆 盖
2、所有用户。 本文研究了移动用户对 信道分配的影响，提出一种针对无线局域网 AP 的信道 分配算法，以最大化用户端的信干比（SIR） 。AP 的信道分配基于最小化 AP 之间的 干扰总量。当用户进入室内时，我们采用负载平衡方案以减小最拥塞 AP 的功率，直 至负载平衡为止。 基于该初始分配， 我们利用 MATLAB 软件计算每一用户的信干比， 研究不同用户位置对信道分配的影响。 最后，借助 OPNET 软件，通过分配 AP 在不同信道上并比较移动用户和固定用 户的网络情形，来研究移动用户对信道分配的影响。结果表明该算法改善了用户端 的网络性能。算法可用于任意无线局域网，无论用户分布和用户负载情形
3、。 关键词：关键词：无线局域网，接入点，信干比，信道分配，负载平衡 华华 中中 科科 技技 大大 学学 硕硕 士士 学学 位位 论论 文文 III Abstract Wireless communication always demand for more bandwidth, increased coverage or range, increased data rate, decreased interference, and lower costs. Today, most AP based WLANs are inefficient in the because of user mob
4、ility. Therefore, they end up providing far less total throughput than they should. Designing 802.11 WLANs include two major components: placement of APs in the service areas and assignment of radio frequencies to each AP. Coverage and capacity are some key issues when placing APs in a service area.
5、 APs need to cover all users. This work is based on studying the effect of mobile users on channel assignment by first developing a channel-assignment algorithm at the Access Points (APs) of a Wireless Local Area Network (WLAN) in order to maximize Signal-to-Interference Ratio (SIR) at the user leve
6、l. We start with the channel assignment at the APs, which is based on minimizing the total interference between APs. Then after when users come in we apply load balancing, by decrementing the power of the MCAP (Most Congested Access Point) until the load is balanced. Based on this initial assignment
7、, we calculate the SIR for each user, using MATLAB. From different users positions a study was conducted on the effect of users position on channel assignment, using MATLAB. Finally OPNET was used for a study which was conducted on the effect of mobile user on channel assignment by comparing a netwo
8、rk with mobile users and a network with fixed users by assigning APs different channels, and it has proven that the algorithm improves the network performance at users level. The algorithm can be applied to any WLAN, irrespective of the user distribution and user load. Key words: WLAN, Access point,
9、 Signal-to-Interference Ratio, Channel assignment, Load balancing 华华 中中 科科 技技 大大 学学 硕硕 士士 学学 位位 论论 文文 VI List of Figures Figure 1.1 Infrastructure mode. 2 Figure 1.2 Ad hoc mode. 2 Figure 3.1 Flowchart for power management algorithm. 20 Figure 4.1 4APs and 20 users (Scenario 1). 27 Figure 4.2 4APs a
10、nd 20 users (Scenario 2). 29 Figure 4.3 4APs and 20 users (Scenario 3). 31 Figure 4.4 4APs and 20 users (Scenario 4). 33 Figure 4.5 4APs and 20 users (Scenario 5). 35 Figure 4.6 4APs and 20 users (Scenario 6). 37 Figure 5.1 Topology for a fixed network. 42 Figure 5.2 Topology for a mobile network. 4
11、3 Figure 5.3 AP1 throughputs for fixed and mobile network. 43 Figure 5.4 AP2 throughputs for fixed and mobile network. 44 Figure 5.5 AP3 throughputs for fixed and mobile network. 45 Figure 5.6 AP4 throughputs for fixed and mobile network. 45 华华 中中 科科 技技 大大 学学 硕硕 士士 学学 位位 论论 文文 VII List of Tables Tab
12、le 2.1 Parameters for link SNR models for different indoor propagation models. 16 Table 4.1 Channels and Powers (Scenario 1). 28 Table 4.2 Distances and SIR from APs to Users (Scenario1). 28 Table 4.3 Channels and Powers (Scenario 2). 29 Table 4.4 Distances and SIR from APs to Users (Scenario2). 30 Table 4.5 Channels and Powers (Scenario3). 31 Table 4.6 Dist
