Performance Analysis of Digital Radio Links with Nonlinear Transmit Amplifiers

This paper evaluates the effects of transmit amplifier nonlinearities on digital radio link performance. Special emphasis is given to links carrying 256-level modulations, for which the impact of even mild nonlinearities can be severe. Performance is measured in terms of the flat fade margin ( F ) normalized by its theoretical maximum (F max ). Curves of F / F_{max} versus amplifier input drive level are used to evaluate and compare numerous design strategies. A major contribution of this work is the development of a fast, accurate method of computer analysis, in contrast to the more cumbersome Monte Carlo simulations generally used for these assessments. Moreover, the new method is used to study a variety of techniques devised to combat the nonlinearity, particularly signal predistortion. It is also used to investigate various approaches to pulse shaping and filtering, to quantify the degradation in performance with increasing numbers of modulation levels, and to examine the possible benefits of linear equalization.

[1]  D. Falconer Adaptive equalization of channel nonlinearities in QAM data transmission systems , 1978, The Bell System Technical Journal.

[2]  L. J. Greenstein,et al.  Required Transmit Filter Bandwidths in Digital Radio Systems , 1981, IEEE Trans. Commun..

[3]  Hiroshi Nakamura,et al.  A New 4 GHz 90 Mbps Digital Radio System Using 64-QAM Modulation , 1984, ICC.

[4]  J. A. Crossett,et al.  64-QAM Digital Radio Transmission System Integration and Performance , 1984, ICC.

[5]  Larry J. Greenstein,et al.  Digital Radio Performance When the Transmitter Spectral Shaping Follows the Power Amplifier , 1987, IEEE Trans. Commun..

[6]  David G. Messerschmitt,et al.  Nonlinear Echo Cancellation of Data Signals , 1982, IEEE Trans. Commun..

[7]  Allen Gersho,et al.  Adaptive Cancellation of Channel Nonlinearities For Data Transmission , 1984, ICC.

[8]  Adel A. M. Saleh,et al.  Frequency-Independent and Frequency-Dependent Nonlinear Models of TWT Amplifiers , 1981, IEEE Trans. Commun..

[9]  Sergio Benedetto,et al.  Nonlinear Equalization of Digital Satellite Channels , 1982, IEEE J. Sel. Areas Commun..

[10]  Larry J. Greenstein,et al.  Multipath Fading Models and Adaptive Equalizers in Microwave Digital Radio , 1984, IEEE Trans. Commun..

[11]  J. Namiki An Automatically Controlled Predistorter for Multilevel Quadrature Amplitude Modulation , 1983, IEEE Trans. Commun..

[12]  Kamilo Feher,et al.  256-QAM Modem Performance in Distorted Channels , 1985, IEEE Trans. Commun..

[13]  J. D. McNicol,et al.  Design and Application of the RD-4a and RD-6a 64-QAM Digital Radio System , 1984, ICC.

[14]  Gianfranco Bilardi,et al.  Spectral analysis of the powers of a PAM digital signal , 1984 .

[15]  T. Noguchi,et al.  Design and Performance of 6-GHz 135-Mb/s Radio System with 64-QAM , 1984, ICC.

[16]  A. A. M. Saleh,et al.  Adaptive linearization of power amplifiers in digital radio systems , 1983, The Bell System Technical Journal.

[17]  Allen Gersho,et al.  Adaptive Cancellation of Nonlinear Intersymbol Interference for Voiceband Data Transmission , 1984, IEEE Journal on Selected Areas in Communications.