Joint Transmitter-Receiver Beamforming Over Space-Time Fading Channels

The problem of joint transmitter and receiver beam- forming in the downlink DS-CDMA over multipath fading channels is considered in this paper. The proposed investigation is based on the array manifold concept and thus, the space-time properties of the channel can be fully exploited, playing a crucial role in the operation of blind channel estimation and interference suppression techniques. The beamforming weights are designed to minimise the overall mean-squared-error (MSE) of the system. An iterative solution to the optimisation problem is firstly proposed under the system framework. A closed-form solution based on channel eigendecomposition is then proposed. The convergence of the iterative method to the closed-form solution and the equivalence of the two methods are verified through numerical simulations. The performance of the proposed approach is also supported by some illustrative examples.