A method for increasing the efficiency and robustness of non-orthogonal multiple access (NOMA) schemes may include storing relationships that associate codewords with values of bit sets, receiving information bits and converting the information bits into bit sets, determining codewords associated with the bit sets, and transmitting the determined codewords. A first codeword may be pre-defined for a WTRU. A second codeword associated with a first bit set may be determined using a first relationship between the first codeword and a value of the first bit set. A third codeword associated with a second bit set may be determined using a second relationship between the second codeword and a value of the second bit set.