OFDMA-CDM performance enhancement by combining H-ARQ and interference cancellation

In this paper, superimposed packet allocation for orthogonal frequency-division multiple-access code-division multiplexing (OFDMA-CDM) is presented, where each transmitted packet is associated with one spreading code. An iterative algorithm which is a combination of parallel interference cancellation and hybrid automatic repeat request (H-ARQ) based on soft value combining (SVC) is proposed, and its performance is studied and compared with other existing H-ARQ schemes. The proposed algorithm exploits the reliability information of erroneously received copies of the same data packet to improve the performance of interference cancellation. The interference of correctly received packets is ideally reconstructed and subtracted. Thus, the overall system performance improves iteratively. As a result, the proposed algorithm outperforms conventional H-ARQ based on SVC, as well as H-ARQ based on maximum ratio combining.