Effect of nonlinearities in wireless communication with digital receiver

This paper discusses the effect of nonlinearities introduced by Radio Frequency (RF) amplifier in practical digital receivers. Taking downlink as an example, after considering several main limitations in engineering implementation and simplifying the model of the receiver, the effects of receiver nonlinearities on the performance both in A WGN and Rayleigh fading channel are obtained. In A WGN channel, the SNR at the input of Am converter has a limit, even though the transmitting SNR is very large with given input power of A/D converter. Combining with the characteristic of quantization, we find trade-off relationship between the SNR at the input and the output of A/D converter. Then, a method is proposed to maximize the SNR at the output of Am converter, and an upper bound of the SNR is also obtained. Considering nonlinearities and using the optimizing method in this paper, the SNR at the output of AID converter increase 4 dB at most, as the digital bit increases 1 bit. In Rayleigh fading channel, a threshold of transmitting rate is derived, which is affected by nonlinearities of the receiver.