On the analysis of peak-to-average ratio (PAR) for IS95 and CDMA2000 systems

Peak-to-average ratio (PAR) of a signal is an important parameter to a linear amplifier because it determines the backoff factor needed to be applied to the amplifier in order to avoid clipping and hence spectral regrowth. In this paper, we analyzed the PAR of the downlink direct code-division multiple-access (DS-CDMA) signal for the IS-95 (2G) and the CDMA2000 (3G) systems. Both the single-carrier (SC) and the multi-carrier (MC) situations are considered. For MC systems, an analytical model is developed to describe the PAR distribution. Closed-form expressions are obtained. Results are compared with simulations, and a nearly exact match is found. This is very useful since simulations for PAR distribution are very costly. Finally, PAR control by synthesis methods are proposed, and their effectiveness are discussed.