Combining-after-Decoding Turbo Hybrid ARQ by Utilizing Doped-Accumulator

This letter proposes a doped-accumulator assisted packet-combining-after-decoding (ACC-CAD) technique with different doping rates per transmission phases for hybrid automatic repeat request (ARQ). Horizontal iteration (HI) performed for decoding the serially concatenated codes (SCC) is followed by Vertical iteration (VI) to exchange extrinsic log-likelihood ratio (LLR) of the uncoded (systematic) bits, and the HI/VI chain is repeated. The doped-accumulator enables the two extrinsic information transfer (EXIT) curves of the SCC to match very well and the convergence tunnel to open until a point very close to the (1.0,1.0) mutual information point. Excellent performance of our technique is verified through EXIT analysis as well as frame-error-rate (FER) and throughput simulations.