MTSP: Multi-hop Time Synchronization Protocol for IEEE 802.11 Wireless Ad Hoc Network

• Main Authors: Guan-Nan Chen, 陳冠男
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/36755064169857960560

碩士 === 國立中正大學 === 通訊工程研究所 === 93 === Clock synchronization is very important for power management protocol in a multi-hop MANET. However, since MANET is a network temporarily formed by a collection of mobile nodes without the aid of any centralized coordinator, clock synchronization is very difficult to achieve. Therefore, most of previous works on power efficiency assumed asynchronous clock. As a consequence, a mobile node will waste a lot of power and time waiting for forwarding a packet to its neighbors, due to the lack of information of wakeup times of its neighbors. In IEEE 802.11 standard, time synchronization function (TSF) is defined to synchronize clocks of all mobile devices in a single hop ad hoc network. In this standard, devices generate beacons with timestamp and contend to send a beacon in each beacon interval. Based on the received timestamp, devices then can synchronize their clocks easily. However, the IEEE 802.11 TSF is not suitable for dense networks and will cause time partition problem when extended to multi-hop ad hoc networks. In this paper, we propose a multi-hop time synchronization protocol, referred to as MTSP, for IEEE 802.11 multi-hop ad hoc networks. The MTSP consists of two phases, namely the beacon window phase (BW-phase) and the SYN phase (SYN-phase). In beacon window phase (BW-phase), several devices, which can directly communicate with each others, form a synchronization group. And each group selects the device with fastest timer as the leader node of the group. In SYN phase (SYN-phase), leader nodes then synchronize with each other. Our simulation results show that MTSP is a distributed and effective multi-hop time synchronization protocol, especially for dense networks.