Performance evaluation of efficient continuous ARQ protocols

Generalized continuous automatic-repeat-request schemes with compound error detection (compound go-back-N, or CGBN) and increased bit interval (IGBN) are presented. In the proposed CGBN scheme, sets of identical copies of each block are continuously transmitted through the forward channel to the receiver where soft error detection is performed in conjunction with the standard hard demodulation algorithm on each received block. In this way, errors can often be corrected without the implementation of an explicit correction procedure. Throughput efficiency is increased by optimization of the soft demodulation algorithm and by derivation of the optimum value of the number of identical copies to be transmitted for each data block. The IGBN scheme achieves performance close to that of the optimized CGBN with no additional implementation complexity over a hard-decision decoder by increasing suitably the bit interval. In comparison to classical and and modified versions of continuous ARQ schemes described in the literature, the CGBN and IGBN schemes also achieve better performance in terms of mean buffer occupancy and waiting times