Performance comparison between MC/DS-CDMA and MC-CDMA for reverse link broadband packet wireless access

This paper compares the radio link capacity between multi-carrier/DS-CDMA (MC/DS-CDMA) and multi-carrier CDMA (MC-CDMA) for reverse-link broadband packet wireless access, taking into consideration all major subject factors: the asynchronous signal reception at the receiver; the path timing or symbol timing detection; and channel estimation error. Simulation results show that, although the influence of the asynchronous signal reception on the packet error rate (PER) performance in MC-CDMA is slight, the degradation caused by the channel estimation error in MC-CDMA is severe compared to that caused by the path timing detection error in MC/DS-CDMA. Consequently, the required average received signal energy per bit-to-background noise power spectrum density ratio (E_b/N₀) at the average PER of 10^-2 in MC/DS-CDMA is reduced by approximately 4.5 dB compared to that in MC-CDMA assuming a 12-path exponential decayed Rayleigh fading channel. Furthermore, the number of accommodated users in MC/DS-CDMA is 2.5 fold greater than that in MC-CDMA employing two-branch antenna diversity reception. Therefore, we conclude that MC/DS-CDMA is more appropriate than MC-CDMA for the reverse link broadband packet wireless access, along with its advantageous features such as an inherently much lower peak-to-average power ratio (PAPR) compared to MC-CDMA, which accompanies a high PAPR causing an Increase in the back-off of the power amplifier.