Performance analysis of discrete feedback schemes for downlink multiuser diversity in OFDMA systems

This paper analyzes discrete feedback of various feedback schemes for multiuser diversity in a multiple subchannel environment. In these schemes of full feedback, fixed feedback, adaptive feedback, and threshold-based feedback, users report a quantized discrete value to indicate their modulation and coding scheme instead of feeding back the full values of the channel state. A closed-form expression of the sum-rate capacity is developed to evaluate the feedback schemes. By comparing the feedback schemes in terms of the sum-rate capacity and the feedback load, this paper provides guidance for the selection of a feedback scheme. Additionally, a mixed-feedback scheme is proposed to reduce the amount of allocated feedback resources in the threshold-based feedback scheme, where the base station adjusts the capacity-feedback tradeoff by controlling two parameters, namely the number of subchannels and a threshold.