Effect of limiting the downlink power in CDMA systems with or without forward power control

This paper investigates the effects of limiting the downlink transmit power in cellular CDMA communications systems. The composite signal transmitted in downlink is the sum of all the signals intended for different users. The amplitude of the composite baseband signal depends on the data bits, the spreading waveforms of the users, and the forward power control algorithm, and it determines the transmit power. Two of the important constraints when designing the RF circuits are the average transmit power and the peak transmit power. These two parameters are often specified in terms of the peak-to-average power ratio. One way to reduce the peak-to-average power ratio is to clip the composite baseband signal before modulating it. The analysis in this paper investigates how the signal-to-noise ratio at the remote receiver changes as a result of this clipping. The results show that the peak-to-average power ratio can be made significantly smaller without notable signal-to-noise ratio degradation