On the Asymptotic Throughput of OFDMA Systems with Best-M CQI Feedback

In order to enable channel-aware scheduling, orthogonal frequency-division multiple access (OFDMA) systems require each user to feed back channel quality information (CQI) relative to each frequency resource block (RB) toward the base station. 3GPP LTE systems relieve the overhead entailed by CQI feedback by employing the "best-M" feedback scheme prescribing each user to report the index of the M best RB\´s along with one single CQI measure. In order to provide a flexible tool for system design, we derive an upper bound for the downlink throughput with best-M CQI feedback for both single and multi-antenna communication schemes. Asymptotic analysis shows that, for a large number of users, multiuser diversity provides an SNR gain that scales as 1/M.