A Novel Type-III HARQ Cross-layer Design Based Network Coding for Wireless Broadcast

For improving broadcasting efficiency of wireless network, a novel Network-Coding (NC)-based type-III Hybrid Automatic Repeat reQuest (HARQ) mechanism with Joint Network and Channel Decoding (JNCD) strategy is presented. A combination strategy is developed to perform XORing Network Coding Combined (XNCC) retransmission. The main idea is to recover packets for most users simultaneously using the network coding technology and obtain the soft information of missing packets to implement JNCD in each retransmission phase. Moreover, The proposed NC-HARQ III mechanism is extended to relay system by opportunistic relaying selected strategy. Analytical results and simulation illustrate that the average number of transmissions can be sharply decreased in the whole network especially in severe fading circumstance. Compared with type-I HARQ scheme and NC-HARQ I scheme, the delay gains can be attributed to the potential advantage of network coding and the better PER performance of JNCD strategy.