Performance analysis of a hybrid ARQ for IP packet transmission in fading channel

This paper proposes and analyses the performance of a hybrid selective repeat (SR)/ multi copy (MC) automatic repeat request (ARQ) scheme to transmit fragmented Internet protocol (IP) packets in a Rayleigh fading channel. The ARQ scheme works in SR mode till the last IP packet fragment is transmitted. If a fragment is negatively acknowledged after the last fragment is transmitted, then the system goes in MC mode. In MC mode multiple copies of the erroneous fragment are transmitted. After the IP fragments are received without error the system goes back to SR mode. Performance of the proposed scheme is evaluated in terms of Eb/No (energy per bit to noise ratio), IP packet size, fragmentation size and number of diversity branches. Performance results are obtained using quadrature phase shift keying (QPSK) modulation scheme using maximum ratio combining (MRC) as the diversity combining technique. The results are obtained under a slow Rayleigh fading channel. The proposed scheme gives an improvement of 2 dB over selective repeat stutter scheme 2 (SR+ST 2) for fragment size of 160 bytes and 4 diversity branches