Power Allocation and Feedback Reduction for MIMO-OFDMA Opportunistic Beamforming

MIMO-OFDMA systems using opportunistic beamforming are a promising solution to satisfy the increasing demand in terms of data rate and quality-of-service (QoS). An important practical issue in MIMO-OFDMA systems is the feedback load. As a large number of carriers (e.g. 2048 for WiMax) is usually used in such systems, feeding back full channel state information at the transmitter (CSIT) for each carrier is prohibitive. In this paper, the problem of feedback reduction in MIMO-OFDMA opportunistic beamforming is addressed. We present different partial CSIT schemes that reduce significantly the feedback overload at little expense of system throughput. We additionally investigate different power control strategies that show significant capacity gain for low to moderate number of users over standard opportunistic beamforming approaches