System Design and Performance Analysis of $M$-ary Complementary Coded Multiple Access

Future wireless communications need to support massive connectivity with an increasing number of connected devices. In this work, an $M$-ary complementary coded multiple access ($M$-ary CCMA) scheme is proposed for its applications in future wireless communications with a large overload ratio. Data streams from different users in an $M$-ary CCMA system are mapped to different combinations of codewords generated by a complementary code set. The combinations of codewords share the same time-frequency resources. Compared to traditional orthogonal frequency division multiple access (OFDMA), the proposed $M$-ary CCMA can support a larger overload ratio and a higher spectral efficiency. On the other hand, $M$-ary CCMA ensures a lower bit error rate (BER) performance at the same overload ratio than a traditional non-orthogonal multiple access (NOMA) scheme, making it a very attractive multiple access scheme for future wireless communications.