Accelerated subspace tracking scheme and its applications to multiuser systems

This paper is concerned with a new subspace tracking method by using an accelerated RLS algorithm for time-varying parameters, and its application to direction-of-arrival (DOA) estimation and blind multiuser detection (MUD) in the case that the spatial information of users rapidly changes. The proposed subspace tracker is derived by combining the projection approximation subspace tracking (PAST) with the internal model principle, approximately expressing the changing parameters with an expansion of polynomial time functions. It can still maintain the linear computational complexity to the number of users, similar to the PAST. The effectiveness is validated through some numerical simulations of DOA estimation in a narrowband source scenario and blind MUD in a synchronous DS-CDMA system, respectively