Non orthogonal multiple access for DS-CDMA systems

In direct sequence code division multiple access (DS-CDMA), the symbols of a single user are transmitted over a given spreading code. In this paper, we propose to increase the throughput of CDMA systems using non orthogonal multiple access (NOMA). The base station transmits a combination of N symbols dedicated to N NOMA users using the same spreading code. The ith NOMA user performs despreading then it detects the symbol of weakest user. The ith user performs successive interference cancelation (SIC) to remove the contribution of the signal of weakest user and detects the symbol of the second weakest user. SIC is repeated until the ith user detects its own symbol. We show that CDMA using NOMA offers a larger throughput than CDMA.