In this paper, a performance analysis of DS-CDMA and MC-CDMA is conducted. With DS-CDMA, data is spread using a spreading sequence in the time domain. In contrast, with MC-CDMA, data is spread over different sub-carriers using a spreading sequence in the frequency domain. The comparison of DS-CDMA and MC-CDMA is presented under an AWGN channel. Also, the simulation results for maximal ratio combining and equal gain combining in MC-CDMA are discussed under a Rayleigh fading channel. When the number of users is small (i.e., ≤ 14), maximum ratio combining exhibits better performance than equal gain combining because maximum ratio combining does not increase much multiple access interference. However, when the number of users is large (i.e., ≥ 16), equal gain combining has better performance than maximal ratio combining because maximal ratio combining increases multiple access interference. To facilitate understanding of different systems, the conceptual block diagrams are also introduced.