Reduced Feedback and Signaling Schemes for Sum-Rate Maximization in OFDMA systems

We study several channel quality reporting strategies for OFDMA systems that maximize the sum-rate while constrained by feedback and signaling overhead. These reporting schemes are based on the grouping idea, which essentially limits the number of users accessing a sub-channel or physical resource block. This in turn reduces the overhead needed to convey channel quality indication (CQI). On the other hand, grouping user and/or sub-channels reduces the multi-user diversity. We investigate this trade-off for various grouping schemes. Numerical experiments show that even for reasonably high overheads, the grouping schemes achieve a substantial gain in sum-rate as compared to reporting on all sub-channels. Reporting fine- granular channel quality information on the user´s best subchannels, is found to be the optimal strategy.