A medium rate integrated TDM/TDMA satellite system

Abstract

Since the launch of domestic communications satellites in 1974, the United States communication network extensively uses C-band transponders for providing services to various locations in the CONUS, Hawaii, the Virgin Islands and Mexico. To meet the growing transponder capacity demands through satellites The Western Union Telegraph Company (WUTCO) launched Westar I11 in August 1979, and is planning to use all 3 Westar and Advanced Westar Satellites in the early 1980s. These satellite networks include earth stations with antenna dishes ranging from 15 meters to 4.5 meters for carrying messages, data, program material and video signals for broadcasting and point-to-point transmissions. The satellite systems are designed using Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) techniques for transmission of signals through transponders. The use of TDMA in accessing the transponders for m.ultipoint transmissions provides substantial space segment cost savings and large system flexibility. WUTCO has developed a prototype communication network using low cost small earth stations (SES) employing Time Division Multiplexing (TDM) and Time Division Multiple Access (TDMA) transmission techniques for medium rate (up to 128 KBS) transmissions. The system is designed for carrying the low speed data signals between SES and large earth stations (LES). Each channel is designed to carry up to twelve 9600 baud lines using TDM from LES to SES and TDMA from SES to LES. The ground terminal equipment includes flexibility of system key features such as burst length and network configurations utilizing Field Programmable Logic Arrays (FPLA'S). The frame formats are designed to allow for the inclusion of overhead signalling bits, which would permit automatic downline loading of the network information. This paper briefly describes the network configuration, the TDM/TDMA terminal and other system features. Further, the channel performance for different modes of operation are given. Finally, the system test results are shown. The extension of this system configuration for data transmission between SES locations is also described.