Performance analysis of star architecture packet-switched VSAT networks using random code division multiple access

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1987
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Virginia Polytechnic Institute and State University
Abstract

The intent of this research is to provide a performance analysis of multiple access protocols in packet-switched Very Small Aperture Terminal (VSAT) satellite communication networks. This research consisted of three major thrusts. First, we analyzed the average time delay of the broadcast Time Division Multiplexing (TDM) outbound channel (hub to VSAT). Second, a throughput performance analysis of an asynchronous Direct-Sequence Code Division Multiple Access (DS-CDMA) communication system is carried out for the inbound line (VSAT to hub). Each channel was characterized by its bit error probability, and transmits fixed-length packets generated according to a Poisson process in an unslotted environment. Third, we presented a delay analysis of the ALOHA DS-CDMA/TDM channel to determine the total service time of a packet originating from either the VSAT or the hub station. In addition to its multiple access capability, this thesis is concerned with the use of direct-sequence spread-spectrum signaling primarily because of its ability to combat interference. Emphasis is placed on average throughput performance, and on the average packet delay after solving for the steady state probability generating function of the station queue size. Then, a discussion of the effect of finite buffer size, and an analysis relating the probability of buffer overflow to packet statistics and buffer size is presented. Because of the bursty nature of a traffic originating from the VSAT’s, the Automatic Repeat Request (ARQ) technique used for error control is the Stop-and-Wait (SW) protocol. It is used as a retransmission strategy in both the Asynchronous Time Division Multiplexing (ASTDM) and the ALOHA DS-CDMA channels.

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