A Joint Time and Frequency Domains Utility-Based Packet Scheduler for Mobile WiMAX Networks

Abstract

Mobile WiMAX represents a broadband wireless solution that enables the convergence of mobile and fixed broadband networks through a common wide area broadband radio access technology and flexible network architecture. IEEE802.16e standard for Mobile WiMAX system is based on the Orthogonal Frequency Division Multiple Access (OFDMA) scheme and allows sub-channelization in both uplink and downlink connections. Different sub-channelization schemes were proposed and implemented for Mobile WiMAX standard. Among them, AMC allows the exploitation of multi-user diversity over frequency domain, in that sub-channels may be allocated to users according to their frequency response over each band of sub-carriers comprising each sub-channel. This multi-user diversity can provide significant gains in overall system capacity if each sub-channel is opportunistically assigned to the user resulting in the highest gain, and therefore using the most efficient modulation and coding scheme. As the frequency diversity is lost with AMC this mode of channelization is more appropriate for fixed and low-mobility applications and/or with the use of Adaptive Antenna Systems (AAS) because these scenarios are associated to better SINR ratios.This article extends the work performed in by proposing a new joint scheduling and resource allocation algorithms for Mobile WiMAX system. The scheduler is based on the two degrees of freedom which results from the definition of radio resources over both time and frequency domains in the TDD OFDMA frame standardized by IEEE802.16e.