Modified cross-layer scheduling for mobile WiMAX networks

The IEEE 802.16 standard defines wireless broadband access technology called Worldwide Interoperability for Microwave Access (commonly called fixed WiMAX). WiMAX introduces several interesting advantages including variable and high data rate, last mile wireless access, point to multipoint communication, large frequency range, and Quality of Service (QoS) for various types of applications. IEEE 802.16e amendment defines mobile WiMAX which includes the fixed WiMAX features plus other features like mobility. However, the actual version of the standard does not define a Medium Access Control (MAC) scheduling architecture in uplink as well as downlink direction. Efficient scheduling design is left for designers and thus providing QoS for IEEE 802.16 Broadband Wireless Access (BWA) system is a challenge for system developers. A scheduling algorithm should take into account the WiMAX QoS classes and service requirements. Cross-layer scheduler which designed for WiMAX networks assign a priority function for every service. The priority functions take into account many parameters like channel conditions, service classes, delay, and throughput. In this paper, the scheduling algorithms will be classified, and a modification in cross-layer scheduling algorithm will be proposed to improve the scheduling performance.