| LMCS (Local Multipoint Communication System) is a bidirectional fixed wireless access technology aims to cater multimedia services to business and residential customers. The nature of supported applications which ranges from highly bursty sources to constant bit rate sources necessitates the use of multiple access techniques for efficient link utilization and QoS guarantees. In this respect TDMA schemes appear at the moment to be the most appropriate choice which can assign bandwidth on demand. CDMA system which gives high capacity gains are presently not considered because of implementation complexity of systems operating with data rate in the 10's of Mbps range.; The focus of this work is to examine and compare the performance of various MAC protocols that are applicable to LMCS networks. DAVIC 1.2 MAC recommendations is the only LMCS specific MAC protocol which provides complete LMCS system engineering solutions, this makes it to be an obvious candidate. The HFC (Hybrid Fiber Coax) networks offer services similar to the LMCS networks, hence HFC-related MACs are also possible candidates. The recently ITU approved DOCSIS (Data Over Cable System Interface Specifications) MAC standard (also called MCNS MAC) is selected for comparison with DAVIC MAC.; Since the study of the upstream channel is comparatively more challenging than that of downstream, we concentrate our study on the upstream performance of both MAC protocols. The performance has been evaluated under homogeneous and heterogeneous traffic conditions for noisy and noiseless channels. The reported results include mean-access delay, throughput, probability distribution function of mean-access delay, collision multiplicity statistics, coefficient of delay variation and call blocking probability. Moreover, the effects of dynamic slot allocation schemes and application of ATM scheduling in wireless networks have also been examined. |
