The INTELSAT TDMA/DSI System is a complex, centrally‐controlled communications system, the performance of which will depend to some extent on the effectiveness of the alignment, maintenance and testing procedures. However, the wide range of disciplines encountered in the system mean staff currently familiar with the existing FDMA network may have difficulty with these new and unfamiliar fields. The purpose of this series of four papers is to provide an understanding of the necessity for, and operation of, the SSOG test procedures for the INTELSAT TDMA/DSI system. In this first part, the overall system and its testing requirements will be discussed as a foundation for a discussion of the SSOG tests in Part 2.
This paper presents some results obtained in laboratory measurements of interference caused by FM television signals to encoded SCPC/QPSK carriers. Certain parameters, such as the TV energy dispersal excursion, the frequency spacing between wanted and interfering carriers, the SCPC bit rate, etc., were varied during the measurements in order to study their influence on the amount of interference suffered by the SCPC channel.
Computer simulations were also carried out in order to analyse and interpret measurement results obtained in some cases.
Conclusions are drawn on the use of a possible interference criterion when rate 1/2 convolutional encoding and soft decision Viterbi decoding is used in the SCPC system as well as on the expected improvement with frequency offset.
This is the third paper in a four-part series addressing the testing and alignment techniques to be used in the INTELSAT TDMA/DSI system. In the first part,' the salient characteristics of the overall TDMA/DSI system were presented together with a discussion of the fundamental requirements for testing and alignment. In the second part,2 INTEiLSAT's satellite system operations guide (SSOG) for TDMA was introduced, the principles of SSOG testing were discussed and the need for several types of specialized test equipment identified. This third part reviews the features of TDMA which affect test equipment design and gives a detailed description of the three items of specialized test equipment which are essential requirements for the conduct of system tests and line-up of individual links. The fourth part will complete the series with a report on operational experience gained in the initial stages of TDMA implementation within the INTELSAT system.
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