Capacity analysis of simple and opportunistic feedback schemes in OFDMA Systems

We mathematically analyze the system capacity of one simple feedback scheme and two opportunistic feedback schemes: simple-feedback, max-feedback, and max-n-feedback schemes, in orthogonal frequency division multiple access (OFDMA) systems. The maximum signal-to-noise ratio (SNR) scheduling strategy can be used as a scheduling criterion at base stations (BSs). In the simple-feedback scheme, each user sends the received SNRs of all sub-bands to the BS for frequency domain scheduling (FDS) at the BS. In two opportunistic feedback (OFB) schemes: max-feedback and max-n-feedback schemes, each user sends the reduced number of SNR values among the SNR values of all sub-bands in order to reduce the feedback overhead. In this paper, we derive the system capacity of the simple-feedback and max-feedback schemes in a closed-form. In addition, we derive the upper-bound of the system capacity of the max-n-feedback scheme. The analytical results agree with computer simulation results. Furthermore, the results show that the OFB schemes can reduce the feedback overhead, while the multiuser diversity can be maintained as the number of user increases.