Reduced feedback selective cluster index scheduling with user pre-selection for next generation MIMO-OFDMA systems

The joint use of Opportunistic scheduling and Orthogonal Frequency Division Multiple Access (OFDMA) provide significant diversity gains even in environments of low mobility and scatter for which channel variations are low. The downside of opportunistic scheduling, in multicarrier systems such as OFDMA, lies in the substantial uplink overhead required to be fed back by the Mobile Stations (MSs) describing users’ instantaneous link conditions. This paper presents a novel approach towards multicarrier opportunistic scheduling for a MIMO configuration that promises major uplink feedback overhead reductions with only minor degradations on downlink throughput performance. The conventional channel quality indicator (CQI), in the form of instantaneous Signal to Noise Ratio (SNR) is replaced by an alternative metric, in the form of the index of the strongest frequency clusters of each MS, which imposes a significantly reduced overhead. This paper examines the performance of the proposed channel quality metric for Random Beamforming and examines the benefits in terms of throughput and feedback overhead over existing schemes. Results show that the proposed scheduling approach maintains performance within 1dB of a full SNR feedback scheme whilst achieving a reduction of the required uplink feedback overhead by a factor of up to 24 and also providing improved fairness amongst users experiencing different channel gain levels. Index Terms –Multiuser Diversity, Channel Quality Information, Scheduling