Cross-Layer Design for OFDMA-based Broadband Wireless Systems with Heterogeneous QoS and Imperfect CSI

Qiang Ni; Lecturer, Brunel University

28th April, 2010 at 1.00 pm - EM1.27

Joint UoE/HWU videoconference seminar

There is a growing demand that future networks should be ubiquitous, pervasive and multimedia-capable, i.e. anyone should have broadband access at anytime and anywhere. This demands that the future network access should be broadband, high-speed, and with Quality of Service (QoS) support for various multimedia applications. This vision will not become true without the development of next-generation QoS-enabled broadband wireless access technologies. Orthogonal Frequency Division Multiple Access (OFDMA) technology has been treated as a most promising transmission technique for the next-generation broadband wireless access networks (e.g. WiMAX and LTE). Recent research efforts in resource management of OFDMA generally assume the availability of perfect channel state information (CSI) at the transmitter (CSIT) or imperfect CSIT but with small error variance. However, in a real wireless environment this assumption cannot always hold as large channel feedback delays and/or estimation errors may cause high CSIT imperfectness. Furthermore, the majority does not consider users heterogeneous QoS requirements; instead treats various needs as homogenous. In this work, we propose an opportunistic Adaptive Error-Tolerant cross-layer Scheduling (AETS) scheme for OFDMA systems that incorporates a novel approach of considering the system level’s packet outage and heterogeneous user QoS requirements in combination with a robust physical layer power-bit loading (PBL) algorithm. Our analytical and simulation results show that AETS achieves optimum subcarrier and power allocation by increasing the system's average throughput and simultaneously satisfying the heterogeneous QoS requirements of individual users with significant lower power consumption in comparison to those existing schemes.