Optimal Power Allocation for Channel Estimation in MIMO-OFCDM Systems

This paper investigates the power allocation in orthogonal frequency and code division multiplexing (OFCDM) systems with multiple input multiple output (MIMO) multiplexing (MIMO-OFCDM). Since time-multiplexed pilot channels are employed for channel estimation, the total transmission power should be properly assigned to the pilot and data channels to achieve the best performance. By minimizing the mean square error (MSE) during signal detection, a closed form expression is derived for the optimal power ratio between the pilot and data channels. It is shown that the optimal power ratio is mainly decided by the number of transmit antennas and the number of pilot and data symbols in a packet, while it is not sensitive to other system parameters like signal-to-noise ratio (SNR) and the frequency domain spreading factor. Simulations demonstrate the accuracy of the derived optimal power ratio.