A New Method for the Integration of Modulation and Channel Coding in an ARQ Protocol

The combination of modulation and channel coding can improve the performance of a communication system. In this paper, a new method for the integration of the modulation operation in an automatic-repeat-request scheme is described. This method uses a memory for the successive transmissions of a codeword and, through a suitable encoding operation, the Euclidean distances among the codewords are significantly increased with the number of transmissions. The application of the described method to some different modulation schemes, as M-ary PSK with M > 2 and continuous-phase frequency shift keying modulation, is described. The optimum combination of the modulation and channel coding operations for some short block codes is also presented. The results of the theoretical analysis show that the method described in this paper permits improving both the error probability and the throughput of an ARQ protocol with respect to other similar schemes.