Joint power allocation and MMSE equalizer designs for MIMO distributed relay networks

In this paper, we jointly investigate the power allocation and the equalizer weights for multiple relay nodes in a distributed relay network where each node is equipped with multiple antennas. Based on the minimum mean-square error (MSE) criterion and under the total equalizer power constraint, multi-input multi-output (MIMO) equalizers are designed for equalizing-and-forwarding the signals from the source to the destination in the time domain. An iterative algorithm is proposed to obtain the optimal solution by using the Karush-Kuhn-Tucker (K.K.T.) conditions. With these optimal MIMO equalizers, the MIMO distributed relay network can effectively mitigate the inter-symbol interference (ISI) and achieve both the spatial and multipath diversity gains. Simulation results show that the proposed scheme outperforms the conventional one-tap equalizer scheme for MIMO distributed relay systems in terms of the bit error rate (BER) performance.