Simulation of Binary Continuous Phase Modulation Combined with (1,2)-Convolutional Encoder

Abstract

In this paper the performance of a (1,2)-convolutional encoder combined with continuous phase modulation is simulated. A binary sequence is used inconjunction with the above encoder and a modulation index of (h=1/4). A full response 1REC frequency shaping function is used to maintain phase continuity. A binary (uncoded)CPM with the above modulation index is also simulated. The performance in terms of the probability of bit error event is plotted against signal to noise ratio for both coded and the uncoded CPM schemes. The asymptotic performance of both schemes is plotted along with MSK for comparison purposes. The simulation algorithm used in this paper utilizes the Block Oriented System Simulator known as BOSS. The major components of this simulation are the encoder and the decoder. The encoder consists of binary random data generator and a (1,2)-convolutional encoder combined with a channel vector encoder and a random white gaussian noise generator. The decoder consists of the following modules: sequential vector bank, inner product unit, metric calculator unit, multi stage trellis, symbol decoder and error counter module.