Channel Quality Indication Reporting Schemes for UTRAN Long Term Evolution Downlink

Abstract

In this paper we evaluate the performance of channel quality indicator (CQI) reporting schemes in 3GPP UTRAN long term evolution (LTE) downlink (DL). In LTE, time and frequency dependent CQI is needed for DL packet scheduling (PS) and fast link adaptation (LA). Studies have indicated that frequency domain PS (FD-PS) and LA are essential techniques in improving the LTE performance, giving e.g. both cell throughput and coverage gain of around 40 % over a distributed multiplexing scheme. However, there is a tradeoff with signaling overhead related to the CQI feedback and overall LA and PS performance, which is rather overlooked in the literature. We analyze four different CQI reporting schemes with respect to system spectral efficiency and conclude that the best-M average and threshold based CQI reporting schemes seem to be the most promising in terms of the compromise between system performance and signaling overhead.