On the peak-to-average power ratio of pre-equalized multi-carrier code-division multiple-access transmissions

Recently, pre-equalization for multi-carrier code-division multiple-access (MC-CDMA) systems has attained increased interest. In addition, combined-equalization has been proposed to further enhance the error rate performance of conventional MC-CDMA systems. However, an important issue, peak-to-average power ratio (PAPR), has not been addressed within such systems in the literature. The purpose of this paper is to fill this gap. In particular, we focus on uplink MC-CD MA with pre- or combined-equalization and analyze its PAPR. A general expression for the PAPR of uplink MC-CDMA is derived and some analytical properties are provided. It turns out that PAPR significantly depends on applied pre-equalization technique. Thus, we show how pre-equalization coefficients could be designed in order to reduce PAPR.