Symbol Assignment for High-Rate Circular Trellis-Based Turbo Codes

Circular trellis code modulators (CTCM) are low latency, short block codes. These codes were originally designed for spread spectrum communication systems operating in an anti- jam environment. For these applications, low-rate, non-systematic parallel concatenated encoders along with iterative turbo decoders were used to achieve Near Shannon limit performance. For applications that require high data rates, CTCM can be modified to get a high-rate encoder. For this high-rate encoder, the symbol assignment method used by the low-rate code cannot be directly applied. In this paper, we present symbol assignment for rate-1/2 and rate-1/3 CTCM and show that their performance is comparable to other codes available in literature.