QoS-Driven Power Allocation for Multi-Channel Communication under Delayed Channel Side Information

In this paper, we study the power allocation scheme for a single user, multi-channel system, e.g. orthogonal frequency- division multiplexing (OFDM) systems, under time-variant wireless fading channels. We assume the receiver feeds back perfectly estimated channel state information (CSI) to the transmitter after a processing delay. The objective of the power allocation is to maximize physical (PHY) layer throughput under quality-of- service (QoS) constraint. The QoS measure of our consideration is a triplet of data rate, delay, and delay bound violation probability. A two-step suboptimal power allocation scheme is proposed which addresses the imperfect CSI issue. In the first step, the total transmission power that can be used by one block is determined according to the summation of the channel gains of all the channels. In the second step, the total transmission power is allocated to all the channels. Compared to the optimal power allocation scheme designed for the perfect CSI scenario, the proposed power allocation scheme reduces the computation complexity significantly while achieves comparable performance.