【作者】 王昕；

【导师】 任勇；

【作者基本信息】 清华大学 ， 信息与通信工程， 2004， 硕士

【摘要】 随着现代无线通信技术和因特网的发展与进步,人们对移动信息服务的需求也日益增长,这促使低成本、较少依赖基础设施的无线网络技术成为学术和产业研究的热点。降低能量消耗是无线网络协议中最重要的设计目标之一,MAC层的功率管理机制是降低无线网络能量消耗的重要手段。本文围绕流行的MAC层标准和功率管理问题,主要做了以下几方面工作:论文综述了当前流行的IEEE802系列无线网络标准,比较协议的性能和发展前景。通过计算性仿真,论文比较了802.11e和802.15.3工作在高速率物理层上的吞吐量,以及802.11和802.15.4工作在低速率物理层上的带宽利用效率。相关分析和评述将对无线网络研究和产品开发有所帮助。论文深入分析了现有的MAC层功率管理协议,提出了通用的MAC层功率管理策略:减少冲突,减少意外侦听,减少状态转换,自适应的功率控制和多速率调制,减少控制开销,自适应的自动重传和前向纠错以及按照能量优先级分配信道。在此基础上,论文提出了功率管理原理。论文以802.11PSM为基础,研究发现以CSMA/CA为基础的功率管理存在两大问题:意外侦听造成的能量开销和省电模式下的收包反应延迟。意外侦听是802.11PSM的能量浪费的主要原因,本文针对DCF、EDCA、PCF和HCF等不同协调方式提出了减少意外侦听的策略。同时,本文提出的RTTA-PSM协议可以在减少反应延迟与降低能耗之间取得较好的折衷。基于对802.15.3MAC机制的深入分析,论文指出减少状态转换次数是TDMA系统中功率管理的主要问题,利用通信流调度算法可以有效地减少网络的总体状态转换次数,且该调度问题可以转化为一个哈密顿图问题。依据图论知识,论文推导出最小状态转换次数的理论上界和下界。考虑到哈密顿图问题尚无最优的解决方案,本文相继提出LSA和MDS两种次优调度算法,仿真比较说明它们优于现有算法而且MDS在大多数情况下已经能够取得最优解。 <WP=4> 本文重视理论与实际相结合,提出的功率管理方案和算法都易于在现有无线网络产品中实现。更多还原

【Abstract】 With the rapid development of modern wireless communication and Internet, people have become more and more dependent on mobile information services. This trend is driving the technology of wireless network, which requires low cost and little dependency on infrastructure, to become one of the hottest focuses in academic and professional research. Energy conservation is one of the most important objectives in the design of wireless network protocols and MAC power management is an effective way to achieve this goal. Focusing on the popular MAC standards and problems of power management, this thesis makes contribution as described in the following paragraphs. The thesis gives a review of popular IEEE 802 wireless network standards, comparing them in performance and prospective industrial applications. With numerical simulation, the thesis compares throughput of 802.11e and 802.15.3 over high physical rates and compares bandwidth efficiency of 802.11 and 802.15.4 over low physical rates. The related analysis and evaluations should be helpful for research of wireless network and product development.With the extensive analysis of MAC level power management protocols in the state of art, this thesis induces the universal policies for MAC level power management: less contention, less overhear, fewer state transitions, adaptive power control and multi-rate modulation, less control overhead, adaptive ARQ and FEC and channel allocation based on energy priority. At the same time, the thesis proposes an analytical model for power management.Based on 802.11PSM, the thesis points out two problems existing in power management for CSMA/CA—energy loss due to overhear and delay of response time for stations in power saving mode. For coordination functions of DCF, EDCA, PCF and HCF, the thesis proposes corresponding methods to reduce overhear, which is the greatest source of energy loss for 802.11PSM. <WP=6>The thesis also proposes a RTTA-PSM protocol to make a tradeoff between response time and energy consumption.With an extensive analysis of 802.15.3MAC, this thesis points out that reducing transition times is a primary problem of power management in TDMA systems. Flow schedule algorithms can be used to reduce the overall transition times in such a system. Thanks to the graph theory, the schedule problem can be changed into a Hamilton Graph problem for theoretical analysis. At the same time the lower bound and upper bound of the minimum transition times are deduced. However, since there is no optimal solution for Hamilton Graph problem, the thesis proposes two sub-optimal schedule algorithms—LSA and MDS. Simulation results prove that the proposed algorithms perform much better than existing algorithms solving similar problems and MDS can actually achieve optimal solution in most scenarios.Studied with both theoretical and practical consideration, the mechanisms and algorithms proposed in this thesis can be easily implemented within current wireless network products.更多还原