One of the main disadvantage of multi-carrier CDMA (MC-CDMA) signals is the high peak power of the transmitted signals which limits their applications. To account for this issue, we provide a simple signal processing for reducing the high crest factor (CF) of MC-CDMA signals. Using this modified MC-CDMA signal, the high CF due to Walsh spreading sequences can be mitigated without explicit side information and degradation in the detection performance.

This letter proposes a modified orthogonal frequency division multiplexing (OFDM) signal with low peak-to-average power ratio (PAPR). As the case of previous works, OFDM system exploits a frequency diversity by using a simple symbol repetition. From the presented results, we can see that three modified OFDM signals using one transmit antenna can be implemented with low PAPR, still maintaining the same diversity gain at the receiver as in [9],[10].

This letter presents a new probability expression for a multi-carrier (MC) DS/CDMA acquisition system with a reference matched filter (RMF). To evaluate the mean acquisition time (MAT) as a measure of the system performance, the probabilities of detection, miss, and false alarm are derived. From the results, it is shown that the MAT of the MC-CDMA hybrid system with RMF is comparable to the optimum mean acquisition time of the conventional MC-CDMA hybrid system, maintaining approximately the same degree of structuring complexity.