Joint coding of sequential HARQ feedback

Wireless broadband systems conceal the high error rates of their underlying channel from Internet protocols such as TCP using a windowed ARQ protocol. They also use a HARQ protocol at the physical layer where ACK/NACK feedback signals are sent for every packet. The higher layer “outer” ARQ protocol is needed due to the relatively high error rate of the HARQ feedback signals, especially NACK→ACK errors. The ARQ protocol feedback messages incur a relatively high protocol overhead but are sent relatively infrequently and corrects HARQ errors. Using a novel method of jointly coding successive HARQ feedback signals, this paper shows how NACK→ACK errors can be virtually eliminated and the outer ARQ protocol dispensed with. The method reduces protocol overhead and overall packet latency.