Correlated Superposition Coding: Lossless Two-User NOMA Implementation Without SIC Under User-Fairness

Non-orthogonal multiple access (NOMA) has a larger achievable sum rate than orthogonal multiple access (OMA). This superiority is achieved via superposition coding (SC) and successive interference cancellation (SIC). In this letter, the authors propose a lossless NOMA implementation without SIC. This implementation is achieved via correlated SC (CSC), in contrast to conventional independent SC (ISC). In addition, correlated non-SIC decoding is performed, in contrast to conventional SIC decoding. Using the random channel coding theorem, we prove that the conditional achievable sum rate given channel gain realizations in the conventional ISC/SIC NOMA scheme can be achieved without SIC, without loss, over the power allocation range of user-fairness.