Throughput analysis of three multiuser diversity schemes

The throughput of three slot allocation schemes for the downlink of a wireless TDMA system are investigated under the assumption of block-Rayleigh fading. The schemes use the instantaneous SNR at the users in order to take advantage of the independent fading of the channels. In the first scheme, which has been proposed earlier (R. Knopp et al., 1995), the base station transmits to the user that experiences the largest SNR in every slot. In the second scheme, which is a variant of an existing scheme (P. Viswanath et al., June 2002), the user with highest ratio between instantaneous SNR and mean SNR is transmitted to. Lastly, we propose a scheme that compares the SNR at a user to a threshold in order determine if transmission to that user shall occur. If the SNR is below the threshold, transmission to another user is attempted. The results indicate that considerable throughput gains can be achieved even with limited SNR feedback, although there exists a trade-off between throughput and delay.