Power Allocation Scheme for MIMO MC-CDMA With Two Dimensional Spreading

In this paper, we develop a power distribution scheme for multi-input multi-output (MIMO) multi-carrier (MC) code division multiple access (CDMA) systems with two-dimensional spreading for wireless transmission. We propose to allocate power among symbols of the active users transmitted from multiple transmit antennas based on a heuristic expression of the bit error rate (BER). Optimization principle consists of minimizing the average BER of all users in term of channel conditions, user multiplexing and number of transmit antennas. Due to the simplicity of the approximate BER expression, we can obtain a closed form expression of the optimum power to be allocated to each user on each transmit antenna. Simulation results show significant improvement of the BER performances compared to the equal power distribution for various modulations, several encoding gains and two antenna configurations.