PERFORMANCE EVALUATION OF DR-TDMA PROTOCOL FOR WIRELESS ATM NETWORKS

Abstract

Broadband wireless networks will be an integral part of the global communication infrastructure in the future, while Asynchronous Transfer Mode (ATM) is the recommended transfer protocol for the emerging broadband integrated services digital network (B-ISDN). In order to extend the capabilities of ATM over wireless channel the concept of wireless ATM (WATM) was introduced. One of the main challenge in the design of a wireless ATM network resides in the conception of a Medium Access Control (MAC) protocol that will handle the different ATM services while providing an efficient utilization of the wireless channel. In this thesis, we evaluated the performance of a Dynamic Reservation Time Division Multiple Access (DR-TDMA) protocol [1] for wireless ATM networks. It uses Framed Pseudo-Bayesian Priority Aloha protocol to manage the contention slot access. The DR-TDMA resource allocation algorithm grants terminals reserved access to the wireless ATM channel by considering their requested bandwidth and QoS. Two algorithms, Time To Expiry (TTE) and Fair Bandwidth Allocation (FBA) are used to allocate the bandwidth. These two algorithms are combined in the base station scheduler to allocate the bandwidth for the integrated traffic. A simulation program is written in C++ on the linux platform to evaluate the performance of the protocol and it is observed that DR-TDMA MAC protocol provides high throughput in the range of 90 to 95% while maintaining reasonable QoS for all ATM services. Finally the scheduling strategy used by the base station is modified slightly, to allocate the bandwidth in the case of location dependent link errors. It is found that the modified scheduling strategy reduces cell loss rate without much degrading the QoS offered to different classes of traffic.