Design of Cross-Packet Channel Coding with Low-Density Parity-Check Codes

We describe a new mechanism that extends the notion of current hybrid automatic repeat request (H-ARQ) schemes. Unlike other H-ARQ methods, if a retransmission for a packet is required, the retransmission jointly embeds the original information of the first packet as well as additional information from a second packet. In fading channels, this approach introduces diversity gain for the first packet without decreasing the overall code rate. This concept is demonstrated with an implementation based on low-density parity-check (LDPC) codes, and simulations show that this H-ARQ scheme provides a significant increase in coding gain for the first packet, and incurs negligible loss of coding gain for the second packet.