FH-Code Phase Synchronization in a Wireless Multi-Hop FH/DSSS Adhoc Network
Vanninen,Teemu
Centre for Wireless Communications
Saarnisaari,Harri
Centre for Wireless Communications
Raustia,Matti
Centre for Wireless Communications
Koskela,Timo
Centre for Wireless Communications
A military adhoc network has to have a good LPI (Low Probability of Intercept) and LPJ (Low Probability of Jamming) capabilities. These requirements can be met by using a combined frequency hopping / direct sequence (FH / DS) spread spectrum (SS) system. Due to characteristics of an adhoc network, the network wide synchronization has to be achieved distributely, which makes especially FH-code phase synchronization a challenging task. Here, we present an FH-code phase synchronization method suitable for very long FH-codes and unknown codepatterns. The synchronization data is spread using a specific synchronization DS-code (DS(s)-code), i.e., the control channel is in the codespace. Synchronization messages are broadcasted periodically to allow single nodes or subnetworks with different FH-code phases to synchronize as a one network. Divergent synchronization hops are not needed, thus providing excellent LPI & LPJ prop-erties.
In order to achieve and maintain a common FH-code phase a network time synchronization algorithm has to be used. Simulations of an adhoc network with a simple network time synchronization algorithm has been made and the results are presented in this paper. The simulations prove that the chosen algorithm can maintain a common timing at a satisfactory level as long as the connectiveness in a network is tolerable. The effects of clock drift and the synchronization message size have also been studied.
Born in Oulu, Finland
Received M. Sc. (Tech.) from University of Oulu, in 2001.
Has been working for Centre for Wireless Communications (CWC) since 1999 and has been involved with the Finish Software Radio Programme since 2001. Current research topic considers cognitive radios and AdHoc networks.