IEEE 802.16 系統下針對變動位元速率影像傳輸之增進效率的上傳排班演算法

Abstract

Recently, the applications of real time multi-media for broadband wireless access (BWA) systems have become more and more popular. One of the major challenges in transmitting real time multi-media data in BWA systems is that the bit rate of the video traffic varies from time to time, and hence the bandwidth utilization is low. The conventional uplink scheduling algorithms for variable bit rate (VBR) video traffic transmission in IEEE 802.16 BWA systems have some disadvantages, including waste of uplink bandwidth, MAC overhead, and access delay. To cope with the difficulties, we propose an enhanced uplink scheduling algorithm for VBR video traffic transmission for IEEE 802.16 BWA systems. In our proposed algorithm, the base station (BS) assigns uplink bandwidth to the video user by considering the traffic state transitions. We equally divided the uplink bandwidth into several intervals and each interval represents a traffic state. Only when the traffic state is changed, the bandwidth request process is incurred. Also, by using two reserved bits in the generic MAC header of IEEE 802.16 BWA systems as piggyback bits, the information of video traffic state transition can be sent to the BS without extra overhead. With QualNet 4.0, simulation results show that the extra bandwidth consumption of our proposed algorithm is less than that of the conventional algorithms. That is, our proposed algorithm outperforms the conventional algorithms for VBR video traffic transmission in IEEE 802.16 BWA systems.