With the increasing success and acceptance of small-terminal satellite systems, there are growing demands for satellite transponder power and a drive towards greater efficiency. Current modulation and coding methods are reviewed and it is shown that improvements in performance can be obtained by using a low-rate code concatenated with a Reed-Solomon code. Several candidate codes are reviewed and their inadequacies highlighted. A new class of codes, the TCH codes, are defined and some examples of these codes, together with their performances, are given.

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