Network Synchronization in Wireless Ad Hoc Networks

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 time- deviation 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]  J A Murray.  Proceedings of the Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting (15th) Held at Washington, DC on 6-8 December 1983, , 1984 .

[2]  B. J. Karafin,et al.  Mutual synchronization of geographically separated oscillators , 1966 .

[3]  Yoshihiko Akaiwa,et al.  Autonomous decentralized inter-base-station synchronization for TDMA microcellular systems , 1991, [1991 Proceedings] 41st IEEE Vehicular Technology Conference.

[4]  David W. Allan.  Clock Characterization Tutorial , 1984 .

[5]  M. Nakagawa,et al.  Mutual decentralized synchronization for intervehicle communications , 1999 .

[6]  Kay Römer.  Time synchronization in ad hoc networks , 2001, MobiHoc '01.

[7]  Donald F. Towsley,et al.  Estimation and removal of clock skew from network delay measurements , 1999, IEEE INFOCOM '99. Conference on Computer Communications. Proceedings. Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies. The Future is Now (Cat. No.99CH36320).

[8]  Lifei Huang,et al.  On the scalability of IEEE 802.11 ad hoc networks , 2002, MobiHoc '02.

[9]  P. Kartaschoff,et al.  Synchronization in digital communications networks , 1991, Proc. IEEE.

[10]  K. Dessouky,et al.  Network synchronization , 1985, Proceedings of the IEEE.

[11]  H. Rohling,et al.  Decentralized slot synchronization in highly dynamic ad hoc networks , 2002, The 5th International Symposium on Wireless Personal Multimedia Communications.

[12]  Deborah Estrin,et al.  Proceedings of the 5th Symposium on Operating Systems Design and Implementation Fine-grained Network Time Synchronization Using Reference Broadcasts , 2022 .

[13]  John R. Vig,et al.  Quartz Crystal Resonators and Oscillators for Frequency Control and Timing Applications , 1993 .

[14]  J.E. Mazo,et al.  Digital communications , 1985, Proceedings of the IEEE.

[15]  A. M. Abdullah,et al.  Wireless lan medium access control (mac) and physical layer (phy) specifications , 1997 .

[16]  Dong Zhou,et al.  Efficient,and scalable IEEE 802.11 ad-hoc-mode timing synchronization function , 2003, 17th International Conference on Advanced Information Networking and Applications, 2003. AINA 2003..

[17]  H. L.,et al.  Van Nostrand's Scientific Encyclopedia , 1938, Nature.