Performance Enhancement of Downlink NOMA by Combination with GSSK

In non-orthogonal multiple access (NOMA), cell-edge users experience significantly low spectral density because only some part of the total transmit power is allocated. This leads to low spectral efficiency for the paired users in NOMA. To overcome this problem, we propose an integration of NOMA and generalized space shift keying (GSSK), called NOMA-GSSK, to improve the spectral efficiency by exploiting the spatial domain. Spectral and energy efficiency, bit error rate (BER), and computational complexity of the proposed system were analyzed and compared to those of multiple-input multiple-output NOMA (MIMO-NOMA). It is shown that NOMA-GSSK outperforms MIMO-NOMA.