1. An apparatus comprising: at least one processor configured to perform detection independently for each of at least one data stream selected from among multiple data streams transmitted by a transmitter, to perform detection jointly for remaining data streams among the multiple data streams, to compute log-likelihood ratios (LLRs) for code bits for each of the at least one data stream independent of other data streams, and to compute LLRs for code bits for the remaining data streams jointly; and a memory coupled to the at least one processor.