A combined link adaptation and incremental redundancy protocol for enhanced data transmission

The variability of the wireless channel requires adaptive error control. Conventional approaches use either link adaptation (LA), which adjusts the coding scheme based on the estimated channel condition, or incremental redundancy (IR), which adjusts the code rate by incrementally transmitting redundancy until decoding is successful. IR usually achieves a higher effective throughput than that of LA, but a larger delay compared to LA. A protocol which combines the advantages of LA and IR to enhance data transmission is proposed. In contrast to the conventional IR with a highest starting code rate, the proposed approach adaptively adjusts the starting code rate based on the current channel condition. Three schemes are proposed to accomplish adaptation. Simulation results show that the average number of transmissions is significantly reduced, with a small sacrifice in the average throughput compared with those of IR.