Energy-efficient MAC protocol for Voice/Data over Ad Hoc Networks

• Main Author: 張建忠
• Other Authors: Lee, Tsern-Huei
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/09164041436257208787

碩士 === 國立交通大學 === 電機學院碩士在職專班電信組 === 97 === To prolong the network operating time of battery-powered wireless LAN devices, this work proposes a synchronized power management scheme specified in IEEE 802.11 standard. The proposed synchronous protocol requires precise time synchronization among all participating nodes within the Independent Basic Service Set (IBSS). Therefore, Time Synchronization Function (TSF) is defined to enable the protocol to operate without external timing sources. In the proposed 802.11 power management scheme, time is divided into so-called beacon intervals. At the start of each beacon interval, each node must stay awake for a fixed time-period called an ATIM window (Ad-Hoc Traffic Indication Map window). Nodes that have no data to send or receive during the ATIM window enter the doze state in the data transmission window. Many studies indicate that ATIM window size significantly affects power saving and throughput achieved by the nodes. This thesis introduces an energy-efficient MAC protocol to support CBR Voice and Data. Overall Quality of service (QOS) is guaranteed. A bandwidth reservation scheme can be used for CBR Voice transmission. Once stations finish the ATIM message exchange in ATIM window, stations transmit CBR Voice packets in the Data transmission window without further ATIM contention. The proposed protocol improves bandwidth utilization to dynamically adjust ATIM window length to the traffic load. Stations are also allowed to stay awake for only a fraction of the Data window which reduces switch-over time in the Data transmission window.