Air interface protocol design for wireless ATM
Shahram Davari · cIRcle (University of British Columbia) · 2009
The concept of "Wireless Asynchronous Transfer Mode (WATM) is actively considered as a potential framework for next-generation wireless communication networks. In this thesis, the fundamental issues that have to be addressed in order to provide broadband multimedia services to mobile users are discussed. Some system architectures are reviewed which extend the broadband wireline infrastructure to the wireless environment. The Air Interface Protocol (AIP) design which has a direct impact on channel utilization and QoS guarantee, is examined in detail. Wireless links are fading channels, which introduce burst transmission errors. WATM systems are expected to support high data rate applications, therefore the channel behaves as a slow fading channel. Many techniques can overcome slow fading, but the real-time nature of most WATM applications require use of ARQ techniques. To accommodate various applications with different QoS requirements (delay, cell loss ratio) is challenging and requires different error correction techniques to efficiently utilize the channel bandwidth. The solution proposed is to divide a frame to a few sub-frames, and to apply an adaptive FEC/ARQ technique to the sub-frames to overcome channel errors. The proposed system uses a novel Limited ARQ technique; this is a modified Selective Repeat ARQ (SR_ARQ) in which the number of retransmissions is limited and controlled by the base station. Some bandwidth is reserved in each sub-frame to ensure the availability of slots for retransmitted cells. Channel throughput efficiency drives trade-offs among the most important system parameters including number of sub-frames per frame, frame duration, permitted number of retransmissions, and fading burst duty factor.