Efficient Power Allocation for OFDM with Imperfect Channel State Information

This paper studies the effect of the imperfect channel state information (CSI) on the performance of adaptive orthogonal frequency division multiplexing (OFDM) systems. To perform resource allocation, CSI must be fed back to the transmitter. Such feedback CSI is always imperfect due to the time-varying channel, the noisy channel estimation and the limited feedback. First, we analyze the imperfection of the feedback CSI from these three aspects. Then, we propose an efficient method to perform power allocation, where Jensen's inequality is used to approximate the objective of the power allocation in order to enhance the computational efficiency. Simulations show that performance loss due to the CSI imperfection and this approximation is very small for a proper frame length.