Busy Bursts for Trading off Throughput and Fairness in Cellular OFDMA-TDD

Abstract

Decentralised interference management for orthogonal frequency division multiple access (OFDMA) operating in time division duplex (TDD) cellular systems is addressed. Interference aware allocation of time-frequency slots is accomplished by letting receivers transmit a busy burst (BB) in a time-multiplexed minislot, upon successful reception of data. Exploiting TDD channel reciprocity, an exclusion region around a victim receiver is established, whose size is determined by a threshold parameter, known at the entire network. By adjusting this threshold parameter, the amount of cochannel interference (CCI) caused to active receivers in neighbouring cells is dynamically controlled. It is demonstrated that by tuning the interference threshold parameter, system throughput can be traded off for improving user throughput at the cell boundary, which in turn enhances fairness. Moreover, a variable BB power is proposed that allows an individual link to signal the maximum CCI it can tolerate whilst satisfying a certain quality-of-service constraint. The variable BB power variant not only alleviates the need to optimise the interference threshold parameter, but also achieves a favourable tradeoff between system throughput and fairness. Finally, link adaptation conveyed by BB signalling is proposed, where the transmission format is matched to the instantaneous channel conditions.