Error performance for D-MAC data services

Options for error protection within the D-MAC packet format are discussed. It is proposed that the packet-type byte be encoded using frame error correction (FEC), thereby increasing the robustness of the packet. Once FEC for the packet-type byte has been allocated, the choice of FEC for data broadcasting is limited to block codes whose lengths are integer multiples of the information block length. Three different codes have been found to be suitable and (along with the case of no FEC) this gives four options for encoding data within the D-MAC packet. These are related to the carrier-to-noise ratio, and the calculation is made on the assumption that FM duobinary can be treated as three-state frequency shift keying and that the noise is additive white Gaussian noise