Linear transceiver design for relay-assisted broadcast systems with diagonal scaling

Abstract

In this paper, we study the linear transceiver design for the downlink of a cellular network assisted by a multi-antenna relay. A diagonal scaling scheme is proposed in which multiple single-antenna users apply different complex-valued scaling to their signals before decoding, as represented by an equivalent diagonal equalizer matrix. This equalizer is designed together with a linear precoder at the base station (BS) and a linear processing matrix at the relay. The objective is to minimize the weighted minimum mean square error (MMSE) between the precoder input and the equalizer output, subject to power constraints at the BS and the relay. In particular, the optimal relaying matrix is first derived in closed form as a function of the precoder and the equalizer. The latter two can then be jointly designed in an efficient iterative manner. Simulation results demonstrate lower biterror rates (BERs) than previous design methods.

A Unified Approach to Optimal Transceiver Design for Non-Regenerative MIMO Relaying

“…Correspondingly in (29), the first term tr(E h ) is the minimum MSE achieved by the first-hop transmission alone [44], and tr(E g ) − tr(E h E g ) is the penalty due to the second-hop transmission. The last term in (29), −tr(E h E g ), is determined by both B and G, implying that the joint design cannot easily be decoupled.…”

“…The problem of minimizing (29) subject to the power constraint (9) is equivalent to that of minimizing…”

“…For a fixed equalizer Q, with the optimal F in (23), the optimal precoder B that minimizes (29) is in the SVD form…”