Simple algorithm for peak windowing and its application in GSM, EDGE and WCDMA systems

In conventional GSM base station solutions, transmitted carriers are combined after power amplifiers. A GSM signal is a constant envelope signal which means that a power efficient nonlinear power amplifier can be used. However, in third generation systems the signal is no longer a constant envelope signal, which means that linearity requirements for the PA are increased. Also, in the case of multicarrier GSM or EDGE transmission the peak to average power of the signal becomes high if the carriers are combined in the digital domain. High linearity requirements lead to low power efficiency and therefore to high power consumption. In order to achieve good efficiency in the PA the PAR must be reduced, i.e. the signal must be clipped. In the paper the effect of a peak windowing clipping algorithm is studied in the cases of WCDMA, GSM and EDGE transmission. Also, an efficient way to implement the peak windowing algorithm is presented.