Performance analysis of integrated‐services load‐adaptive/TDMA satellite networks

Abstract

A load‐adaptive/TDMA multiple‐access communications system which serves to interconnect broad‐band multimedia packet streams is considered. In particular, the use of a satellite backbone communications link whose channels are dynamically assigned to network stations is investigated. Each station supports packetized voice and data message streams. Incoming streams to a station are statistically multiplexed by the station across the backbone channels currently allocated to this station. To enhance the multiplexing process, a variable bit‐rate packet‐voice encoding scheme is also employed. Stations periodically issue requests for backbone channel allocations, based upon their estimated loading status. We introduce two distinct multiple‐access algorithms for allocating the shared backbone channels to the stations. We develop analytical methods for the analysis and design of such integrated multiplexing/multiple‐access networks. Performance measures include voice and data packet delays and packet blocking probabilities. Voice stream performance is also characterized by the average number of bits per sample used by the voice encoding scheme. The effects of the propagation delay across the backbone link are especially demonstrated. Also illustrated are the performance improvements attained due to the use of the load‐adaptive/TDMA scheme. Under the example of the ’all‐voice’ traffic loading, an LA/TDMA scheme exhibits no obvious performance improvement over a fix‐assigned scheme. However, as the burstiness of the traffic loading increases in the example of the ’data‐voice’ traffic loading, a significant amount of improvement (36 per cent bandwidth savings) is realized by a LA/TDMA scheme.