Timing estimation for quasi-synchronous SDMA systems

In this paper, timing estimation for quasi-synchronous SDMA systems is considered. The problem arises in the uplink of a mobile communication system where precise synchronization among all mobiles is very difficult to be achieved and signals of all mobiles are time-aligned at the receiver within a small synchronization window. An efficient timing estimation method is proposed. It can simultaneously estimate the channel responses and the time delays which are required for signal detection. Simulation results show that the time delays can be accurately estimated and the performance of MMSE multi-user detection with the proposed method is very close to that with the perfect timing and channel information.