Network Synchronization in Wireless Ad Hoc Networks
Carlos H. Rentel, Thomas Kunz · 2004
Abstract. This report presents a brief overview of network synchronization in the context of Wireless Ad Hoc networks. A network synchronization algorithm is proposed and computer performance evaluations presented that show the feasibility of a mutual network synchronization algorithm compatible with an IEEE 802.11 complaint station. The algorithm proposed seeks to synchronize the clocks of the nodes in a Wireless Ad Hoc network in which single-hop (Wireless LAN) or multi-hop communication is supported. No use is made of a master clock such as the one provided by the Global Positioning System (GPS) or by a fixed cluster of broadcasting stations. The algorithm takes advantage of the simplicity of the clock-sampling technique to exchange timing information among the nodes, and the truly distributed characteristic of a mutual network synchronization approach. The beacon messages specified in the IEEE 802.11 standard are used to periodically send the timestamps by each node. A steady-state inter-node timedeviation error less than ten microseconds is obtained after a transition period during which the clocks in the network learn about their drift differences. Performance results for the single-hop and multi-hop case are presented using computer simulations that show a considerable improvement in terms of scalability and maximum inter-node time deviation error with respect to the timing synchronization function (TSF) of the IEEE 802.11 independent basic service set (IBSS) network. Additional results are presented for a modification of the original algorithm in which beacon transmission permission probabilities are computed per node in order to improve the spreading of the synchronization information in a multi-hop network. The contribution of this work is, 1) The performance evaluation of the TSF in a multi-hop scenario, 2) the performance evaluation and approximate analysis of simple extensions to the TSF algorithm, and 3) The introduction of a more scalable and accurate network synchronization algorithm for wireless Ad Hoc networks. 1.