【作者】 肖渊；

【导师】 谭长庚；

【作者基本信息】 中南大学 ， 通信与信息系统， 2008， 硕士

【摘要】 无线传感器网络是由大量集成了传感、数据收集、处理和无线通信能力的传感器节点构成的无线自组织网络。其低成本、自组织、体积小等特点及强大的数据获取能力使无线传感器网络能够广泛应用于多种领域。无线传感器网络中,介质访问控制协议(Medium AccessControl,MAC)规定了无线信道的使用方式,为无线节点合理分配通信资源。传统MAC协议的设计目标是最大化吞吐量、最小化延迟并保证其公平性。而无线传感器网络能量极为有限的特点决定了其MAC协议的设计要以最小化能耗为首要目标。本文首先对典型无线传感器网络MAC协议进行了分类介绍,从传感器节点能量消耗的主要原因入手,分析了MAC协议设计中采用的节能机制。随后详细介绍了专用于无线传感器网络的基于竞争的MAC协议——SMAC(Sensor-MAC),分析了SMAC的节能机制,并指出了周期性睡眠带来的延迟影响。论文提出了两种MAC协议的设计方案:第一,提出了延迟控制的动态占空比MAC协议DC-SMAC。该协议旨在改善SMAC固定占空比不能适应负载变化以及延迟过大的不足,节点能够根据数据包的平均延迟动态调整占空比,并可根据应用的需要选择合适的延迟容忍度。仿真结果表明,相比SMAC,DC-SMAC在延迟、能耗以及吞吐量方面都有显著提高;第二,提出了带功率控制的MAC协议TPC-SMAC。功率控制的目的在于优化网络拓扑,减少冲突,进一步减少能耗。TPC-SMAC利用SMAC的同步过程建立优化功率表,为不同邻居选择合适的功率等级。除此之外,TPC-SMAC还加入了邻居数目优化策略,通过发送功率的控制合理选择邻居,控制邻居数目,达到优化网络拓扑、降低冲突概率的目的。仿真结果表明,TPC-SMAC较之SMAC在能量消耗和网络吞吐量方面都有一定程度的提高。更多还原

【Abstract】 Wireless Sensor Network (WSN) is composed of a larger number of sensors which have functions of data sensing, gathering, handling and communicating. The characteristic of WSN includes low price, small size, powerful data-gathering capacity, which makes it can be widely used in many areas. In WSN, MAC (medium access control) protocol provides the way of wireless channel use and reasonable distribution of communication resources for nodes. The design of traditional MAC protocols usually focuses on throughput maximizing, latency minimizing and guarantee the fairness of channel access at the same time. As a result of the power limitation in sensor nodes, the MAC design in WSN always put minimizing energy-consumption into the top goal.First of all, we introduced the classic MAC protocols in WSN. Then we have given a detailed introduction to SMAC (Sensor-MAC), which is mainly designed for WSN. We analyzed its energy-saving mechanism, and pointed out the latency affection brought by periodic sleeping.We put forward two schemes that based on SMAC: DC-SMAC and TPC-SMAC. DC-SMAC aimed to improve the fixed duty cycle of SMAC, which have a high latency and couldn’t adapt to the traffic change in the network. DC-SMAC can adjust the duty cycle dynamically according to the average packet delay, and can choose an appropriate delay tolerance according to the specific application. The results of our simulation show that in contrast to SMAC, DC-SMAC have a remarkable improvement on end-to-end latency, energy consumption and throughput. TPC-SMAC uses transmission power control to optimize network topology and reduce collision. The optimal power table is built in synchronization process of SMAC, and the appropriate transmission power level is selected for every neighbor. In addition, neighbor optimal scheme is used in TPC-SMAC, which can select neighbor node by transmission power adjusting. The result of the simulation shows that TPC-SMAC has a certain extent of improvement on energy consumption and throughput.更多还原