CQI Feedback Reduction Based on Spatial Correlation in OFDMA System

In OFDMA systems, channel quality information (CQI) feedback is used to determine the modulation and coding level of a mobile station (MS). When the MS uses diversity, it transmits the CQI feedback information which contains channel condition which is averaged over all the sub-bands allocated to itself. In conventional CQI feedback scheme, every MS should send its own CQI feedback. So, as the number of MSs in the system increases, the amount of CQI feedbacks increases too, and it results in the reduction of system throughput. To solve this problem, we have proposed a new CQI feedback scheme. In our CQI feedback scheme, MSs which are close each other make a CQI feedback group. And only one representative CQI feedback per one CQI feedback group is transmitted because MSs which are in the same CQI feedback group have similar channel condition. In this paper, we also have derived the PER equation of MSs when the MSs use a representative CQI feedback. And also, through simulations and numerical results, we have shown that by using our proposed scheme, CQI feedbacks can be reduced.