Hybrid Type-II ARQ Schemes based on Convolutional Codes in Wireless Channels

|In this work we studied the performance of the hybrid type-II Automatic Repeat reQuest (ARQ) system on Rayleigh fading channels. This system is based on High Rate Optimized Rate Compatible Punctured Convolutional (HRO-RCPC) codes combined with simple repetition codes. The performance is investigated for di erent packet sizes and constraint lengths of the convolutional encoder. Additionally the e ect of packet size on the performance in di erent fading environments is studied in more detail. We have also studied the performance of the HRO-RCPC codes combined with optimized Rate Compatible Repetition Convolutional (RCRC) codes as another alternative for channel coding in hybrid type-II ARQ schemes. The simulation results show that HRO-RCPC codes combined with optimized RCRC codes with high parent code rate perform almost as good as the HRO-RCPC codes with simple repetition codes at lower parent code rate. Also a tailbiting decoder using Circular Viterbi Algorithm (CVA) is examined for di erent hybrid type-II ARQ schemes and packet sizes. It is shown that the improvement of the performance due to tailbiting is noticeable for only short packets. For long packets, the sub-optimality of CVA decoding compared to the General Viterbi Algorithm (GVA) degrades the performance considerably. Keywords|Rayleigh fading channels, BPSK modulation, Rate compatible convolutional codes, hybrid type-II ARQ, tailbiting decoder.