BACKGROUND

A coherent wireless communication system supports M users, where each user transmits on the same angular carrier frequency ω with a single transmit antenna while the receiver is equipped with a linear antenna array consisting of L uniformly spaced elements in order to achieve user separation in the angular domain (Paulraj et al., 2003; Tse & Viswanath, 2005). Assume furthermore that the channel is non-dispersive and hence it does not induce intersymbol interference.

Beamforming Signal Model

The symbol-rate complex-valued received signal vector can be expressed as (Litva & Lo, 1996; Blogh & Hanzo, 2002)