• Coherent Demodulation of Continuous Phase Binary FSK Signals

      Pelchat, M. G.; Davis, R. C.; Luntz, M. B.; Radiation Incorporated (International Foundation for Telemetering, 1971-09)
      This paper gives achievable bounds for the probability of error of continuous phase binary FSK signals on the white gaussian noise channel. Phase continuity, like convolutional encoding, introduces a dependence between adjacent transmitted signals which can be used to advantage in the demodulation process. It is shown that continuous phase binary FSK can provide a given probability of error with 0.8 db less signal-to-noise ratio than antipodal PSK. The paper also shows how the ideas developed for decoding convolutional codes apply to the demodulation of continuous phase FSK with rational deviation ratio.
    • Implementation of Maximum Likelihood Decoders for Convolutional Codes

      Clark, George C., Jr.; Radiation Incorporated (International Foundation for Telemetering, 1971-09)
      Maximum likelihood decoding of convolutional codes is finding considerable application in communication systems and several decoders of this type have recently been built. These decoders implement an evolved form of a decoding procedure that was originally described by Viterbi in 1967. In this document we describe the problems of reducing the Viterbi algorithm to hardware, the various tradeoffs and compromises that must be made, and the short cuts that are available. In addition an interesting variation on the Viterbi algorithm is described which results in favorable implementation particularly at high data rates.