Analysis of noise immunity of receiving signals with quadrature amplitude modulation in the presence of scanning interference

 

G. V. Kulikov¹, A. A. Lelyuh^1,2

¹ MIREA – Russian Technological University, Vernadsky av. 78, Moscow, 119454, Russia

² JSC «Moscow Research Institute of Radio Communications», Nizhegorodskaya 32, Moscow, 109029, Russia

 

The paper is received on January 13, 2019, after correction – on February 8, 2019

 

Abstract. Multiposition quadrature amplitude modulation signals (M-QAM)  are widely used in the high-capacity digital data transmission systems. In such systems, the quality of radio communication is affected by various types of interference, both, casual and intended. The aim of the work is to analyze the noise immunity of receiving M-QAM signals in the presence of noise and scanning interference. The scanning interference is presented in this paper in the form of a harmonic oscillation with a frequency varying according to the sawtooth law. Methods of statistical radio engineering and calculations using numerical integration on a computer were used for the analysis. The error probability calculation technique is based on the assumption that the initial phase of the interference and its frequency are first assumed to be some fixed values. In this case, it is possible to calculate the average values and variance of the conditional normal distributions of random processes at the outputs of all the correlators of the receiver and the conditional probability of bit error. Then averaging of the obtained results by random parameters is performed by numerical integration. The dependences of the bit error probability on the signal-to-noise ratio, the deviation of the scanning interference frequency and its intensity are obtained for different number of positions M. It is shown that the M-QAM signals are very strongly influenced by scanning interference and with increasing of number of positions of the signals this effect is significantly enhanced. For example, with a weak interference for M=4 or 16, the probability of error practically does not increase and the energy losses for are not more than 1 dB, for M=32 or 64, the reduction in noise immunity becomes noticeable, and the energy losses reach 2-5 dB. The scanning interference of high intensity threat for all kinds of M-QAM signals and completely destroy the reception. The main negative impact is caused by frequency components of the interference, close to the frequency of the carrier oscillation of the useful signal. The scanning interference that does not fall into the zone of the main lobe of the M-QAM signal spectrum slightly affects the noise immunity of the reception.

Keywords: quadrature amplitude modulation, scanning interference, noise immunity, probability of bit error.

References

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For citation:

G. V. Kulikov, A. A. Lelyuh. Analysis of noise immunity of receiving signals with quadrature amplitude modulation in the presence of scanning interference. Zhurnal Radioelektroniki - Journal of Radio Electronics. 2019. No. 2. Available at http://jre.cplire.ru/jre/feb19/5/text.pdf

DOI  10.30898/1684-1719.2019.2.5