Partially Repeated SC-LDPC Codes for Multiple-Access Channel

A simple partially repeated spatially coupled low-density parity-check (SC-LDPC) code is proposed for a multiple-access channel (MAC) with a large number of users. This code is constructed by selecting part of bits of an SC-LDPC code to be repeated. Since the decoding increment is only a log-likelihood ratio (LLR) combination, compared with the original SC-LDPC code, the decoding complexity scarcely increases. It is shown that this LLR combination is effective to overcome the multi-user interference. By optimizing the ratio of coded bits for repetition, the decoding threshold of the partially repeated SC-LDPC code can be close to the MAC capacity. Experimental results show that the partially repeated SC-LDPC codes have better performance than the graph-extended and parallelly connected SC-LDPC codes over the MAC.