EURASIP Journal on Wireless Communications and Networking 
Volume 2006 (2006), Article ID 37952, 14 pages
doi:10.1155/WCN/2006/37952

Blind Synchronization in Asynchronous UWB Networks Based on the Transmit-Reference Scheme

Relja Djapic,1 Geert Leus,2 Alle-Jan van der Veen,2 and António Trindade2

 1TNO-ICT, Brassersplein 2, CT Delft 2612, The Netherlands
2Department of Electrical Engineering, Delft Institute of Microelectronics and Submicron-technology (DIMES), Delft University of Technology, Mekelweg 4, CD Delft 2628, The Netherlands
Received 15 September 2005; Revised 13 December 2006; Accepted 13 December 2006

Abstract

Ultra-wideband (UWB) wireless communication systems are based on the transmission of extremely narrow pulses, with a duration inferior to a nanosecond. The application of transmit reference (TR) to UWB systems allows to side-step channel estimation at the receiver, with a tradeoff of the effective transmission bandwidth, which is reduced by the usage of a reference pulse. Similar to CDMA systems, different users can share the same available bandwidth by means of different spreading codes. This allows the receiver to separate users, and to recover the timing information of the transmitted data packets. The nature of UWB transmissions—short, burst-like packets—requires a fast synchronization algorithm, that can accommodate several asynchronous users. Exploiting the fact that a shift in time corresponds to a phase rotation in the frequency domain, a blind and computationally effcient synchronization algorithm that takes advantage of the shift invariance structure in the frequency domain is proposed in this paper. Integer and fractional delay estimations are considered, along with a subsequent symbol estimation step. This results in a collision-avoiding multiuser algorithm, readily applicable to a fast acquisition procedure in a UWB ad hoc network.