Study of BER fairness and PAPR for interleaved OFDMA system

In this study, we analyze the role of interleavers in OFDMA system for ensuring uniform BER performance amongst the active users and also investigate their respective PAPR properties. At first considering a generic system in a slowly changing multipath channel where high dispersion in the individual users performance exists, we apply different types of interleaving and show that they in general help in achieving fairness. In particular, by introducing the application of cyclically shifted random interleaver, we demonstrate its effectiveness in achieving BER fairness over others (dispersion in individual users BER reduced by 89% compared to no interleaving at 15dB SNR). Then we explore the comparative performance of different interleavers at varying active user density considering a system based on the IEEE 802.16 standard specifications. Finally, for a generic OFDMA, we investigate the PAPR distribution of different interleavers as the system moves from low to high user loads. Based on the results, we conclude that for a heavily loaded system, cyclically shifted random interleavers can effectively ensure uniform performance amongst active users with reduced system complexity and manageable PAPR.