Adaptive modulation system with discrete power control and predistortion-type nonlinear compensation for high spectral efficient and high power efficient wireless communication systems

Abstract

This paper proposes an adaptive modulation system (AMS) with a discrete power control combined with a predistortion (PD)-type nonlinear distortion compensation technique for high quality and high power efficient high-bit-rate wireless communication systems. In the PD-type nonlinear distortion compensator, predistortion look-up table is updated using a teaching signal embedded in the guard time. In this process, nonlinear input signal vs. output distortion performance is discretely measured during the guard time period, and at the end of the guard time, a sequence of the measured distortion is interpolated using a cubic spline function to reduce memory size and the number of computation. More over, in the power control section, three levels of transmitter power attenuation, i.e., 0, 10 and 20 dB are prepared, and they are selected according to the expected carrier power to noise power spectral density (C/N/sub 0/) of the transmitter. Computer simulation confirms that the proposed method can sufficiently suppress the non-linear distortion in the adaptive modulation TDMA/TDD systems.