Performance analysis of 16-ary QAM signalling through two-link nonlinear channels in additive Gaussian noise

Abstract

This paper considers the problem of evaluating the performance of a 16-ary quadrature amplitude modulation (QAM) signal transmitted through a bandpass nonlinearity (BPNL), exhibiting AM-AM and AM-PM conversions, and in the presence of additive gaussian noise (AGN) both preceding and following the nonlinearity. An expression for the error probability is derived and computed. Also, the effect of TWT back-off from saturation on 16-ary QAM system performance is studied. Finally, as an example, a comparative study of 16-ary CPSK and 16-ary QAM transmissions is undertaken with the BPNL operated at various levels of back-off from saturation. IntroductionDue to rapid growth in demands for communication capacity, available RF bands for terrestrial and satellite communications are becoming more and more crowded. Suitable choice of efficient digital modulation techniques provides one means of achieving improved spectrum efficiency. In addition to spectrum efficient CPSK systems, digital radio transmission may use QAM signalling because of its relative simplicity of implementation and good error performance through linear channels in the presence of Gaussian noise [1]. Initial attempts at solving the problem of evaluating 16-ary QAM performance over two-link nonlinear channels were reported by Thomas et al. [2] and Dupuis et al. [3]. Thomas et al. [2] investigated the performance of 16-ary QAM through a typical two-link nonlinear satellite channel with AGN on the down-link. No account is taken of up-link AGN, but the results indicate that with typical nonlinear TWT amplifier 16-ary QAM signal loses its SNR advantage over 16-ary CPSK unless the signal is either predistorted or the TWT operated below saturation. Dupuis et al.[3] presented a computer simulation procedure to evaluate the error probability of 16-ary QAM through a two-link nonlinear channel exhibiting AM-AM and AM-PM conversions. They included impairments such as AGN and intersymbol interference on the downlink only. As expected, they demonstrated that 16-ary QAM is very sensitive to nonlinearities.As far as the author is aware, no work has been reported on the performance evaluation of 16-ary QAM transmission through two-link nonlinear channels when AGN is present on both up-and down-links. Such study is called for since 16-ary QAM is being seriously considered as a possible signalling scheme to improve the spectrum utilisation of 'bandwidth conscious' nonlinear satellite channels.In this paper, the method of Mathews and Aghvami [4] is extended to analyses the performance of 16-ary QAM transmission through a two-link nonlinear channel in the presence of AGN both preceding and following the nonlinearity. Computations of symbol error probability together with the effect of 'backing-off' the nonlinearity from saturation on system performance are given. Finally, as an example, we compare the effect of back-off on system performanes of 16-ary QAM and 16-ary CPSK transmissions.Paper 3034F (E7, E8). first 2Error probability analysis A schematic diagram of the two-link...

A modified model and linearization method for solid state power amplifier

“…Generally we assume M · M QAM modulation and in a manner similar to [12,23], we derive a general form for P e .…”

Polynomial Based Predistortion for Solid State Power Amplifier Nonlinearity Compensation

“…Generally we assume M × M QAM modulation and in a manner similar to [4,9], we derive a general form for P e . Fig.…”

Performance Analysis of 49-QPRS Through Nonlinear Satellite Channels in the Presence of Gaussian Noise and Cochannel Interference

“…/ Hz of the 1F-bandwidth , its relative simplicity of implementation and good error performance through linear Gaussian channels [3] - [6] . Performance of another schemes such as 16-ary QAM , 16-ary QAM/MSK , I 6-ary CPSK and 9-ary QPRS through nonlinear satellite channel in the presence of AWGN are illustrated in [7] - [10 ] respectively .…”