Timing and Frequency Synchronisation for Multiuser Detection on the Return Link of Interactive Mobile Satellite Networks

Abstract

Synchronization, a key process in a communication system, can be very demanding, especially in burst mode transmissions. The estimation of timing, frequency and phase offsets is sensitive to the ambient interference and noise levels. The aggressive reuse of frequencies in a multibeam satellite system increases the co-channel interference significantly and motivates the need to revisit, and re-design if needed, the algorithms used for synchronization. This paper deals with such a scenario occurring on the return link of a mobile interactive satellite system and provides a set of synchronization sub-systems that allow for the design of a robust modem that can reap the benefits of sophisticated interference mitigation techniques.

Multibeam joint detection

“…. Sampling the above sequences at symbol period would produce a matrix C in (1.47) with imperfectly known entries unless {τ k , ω l , θ k } are precisely known for all k. Different timing and frequency recovery techniques have been tested specifically for multibeam return links using MUD [67]; the latter reference proposed a hybrid algorithm, where a nondata aided estimate is refined by exploiting the pilot pattern, and concluded that good performance results can be obtained if the start of the frames can be correctly decoded, even though better pilot sequences would probably be required. c kL ), we have that c k (t) = L n=1 c kn g(t − nT), k = 1, .…”