Exploiting Correlation Between Wideband and Differential CQIs for Adaptation and Feedback

Abstract

Differential channel quality indicator (CQI) and wideband CQI are key components of the 4G and 5G standards. They enable a base station (BS) to acquire channel state information that is essential for rate adaptation and scheduling without overwhelming the uplink. We present a novel throughput-optimal rate adaptation rule, which exploits the correlation between the differential and wideband CQIs to improve throughput without any additional feedback, and a computationally efficient approach to evaluate it. We then propose a novel flexible-overhead differential CQI feedback scheme, in which the number of feedback bits can be subband-specific. The combination of the two approaches provides a new flexibility to the BS to control the feedback overhead and achieves a throughput comparable to conventional approaches with much less feedback.