Optimal combination of convolutional codes and partial response M-level digitally phase modulated (DPM) signals

The effect of the coding in improving the power efficiency of partial response DPM signals is examined. The main interest is to investigate what improvements may be obtained by coding. The type of convolutional encoders which are considered are of short constraint lengths. The constraint length (or memory length) v varies from 1 to 3. The best combinations of a rate 1/2 convolutional encoder, mapping rule and modulator (binary and 4-level partial response DPM) are found and presented for each modulation index and memory length. It is shown that coded schemes which provide greater power-bandwidth efficiencies than uncoded ones can be achieved. The study is restricted to a partial response DPM scheme with pulse duration LT, where L=3