Power Allocation Algorithms for GMD or UCD Based Joint Transceiver Designs

In a downlink multiuser multiple-input multiple-output channel, joint transceiver designs based on geometric mean decomposition and uniform channel decomposition can provide a BER performance enhancement by making all substreams of each user have the same SINR. However, if a user power allocation (uPA) algorithm is not applied in their designs, they actually make the same SINR for all substreams in each user while causes different SINR with one another, and therefore the average BER is dominated by the user with the worst SINR. In this regards, it is possible to enhance BER performance further provided that the uPA algorithm is taken into account under a total power constraint. The objective of this paper is to maximize the worst user’s SINR by applying the uPA algorithm with the total power constraint. Because of proposed uPA algorithms, all substreams across all users can have the same SINR, which leads to minimization of average BER. Simulation results show that joint transceiver designs with proposed uPA algorithms have an SNR gain about 2 dB at the BER of 10^-3.