A geometrical analysis of OFDM-CDMA with frequency offset

We analyze the performance of code division multiple access (CDMA) systems with orthogonal frequency division multiplexing (OFDM). We obtain the probability density function (pdf) of the multiple access interference (MAI) of CDMA systems and extend the results to OFDM-CDMA systems to determine the pdf of the MAI and inter-carrier interference (10) in terms of the number of users, the spreading length, the crosscorrelation of spreading sequences, the number of sub-carriers and the frequency offset. we consider the synchronous downlink of cellular multi-carrier CDMA systems and derive a Gaussian approximation of the MAI and ICI. The results show that the overall effect of frequency offset varies with system loading for a given crosscorrelation. The performance of OFDM-CDMA in frequency selective fading channels is analyzed in terms of the joint probability of the fading parameter in each sub-carrier.