Space-time blind delay and DOA estimation in chip-asynchronous DS-CDMA systems

A blind time-delay and direction-of-arrival (DOA) estimation algorithm using beamforming arrays is proposed for short-code chip-asynchronous DS-CDMA systems. The proposed space-time processing technique consists of two stages. The time delay estimation process is performed at the first stage. Then, the soft information obtained from the first stage is used for DOA estimation at the second stage. The time-delay estimation algorithm is based on the minimum output energy (MOE) criterion. It consists of two steps, coarse and fine synchronization, where integer and fractional delays of the desired signal are estimated, respectively. The DOA estimation is performed based on the estimated power of the desired signal (or soft information) from each beamforming filter steering at a different direction. Experiments are conducted to demonstrate the superior performance of the proposed scheme.