A Cross-Layer Downlink Scheduling Scheme for Balancing QoS in IEEE 802.16 Broadband Wireless Access Systems

IEEE 802.16 OFDMA wireless network is expected to be the dominant system used by operators in these last decade due to its promising solutions for providing high data rate. However, IEEE 802.16 packet scheduling and resources assigning among Mobile Stations (MSs) is still the main challenge due to unfairness and low performance which occur when allocating resources to MSs. Furthermore, MaxSNR scheduler is often recognized by the scientific community as the most effective in OFDMA wireless networks. Thanks to its opportunistic operation, it takes into account changes in the states of links, maximizes system throughput and so can accommodate a very large number of users in the network. However, this does not come cheap: MSs far from the access point are systematically penalized compared to closer ones; this is because of their little favorable transmission conditions (caused by path loss). In this paper, we propose an improvement to MaxSNR scheduler called Dynamic and Fair MaxSNR (DFMaxSNR). The DFMaxSNR consists not only of exploiting the concept of opportunistic scheduler in order to maximize system throughput, but also of correcting the unequal spectral efficiencies induced by path loss attenuations in order to minimize the delay and the packet loss rate for real time applications. Performance evaluation shows that this well-balanced resource allocation scheme outperforms other existing schedulers (MaxSNR, PF and RR) and demonstrate that choosing between high system capacity and high fairness is not required.