Research of the Influence of the Quadrature Components Mismatch on the Noise Immunity of OFDM and UFMC Signals

Abstract

The method of direct modulation using complex signals is used to implement signal paths of transmitters in base stations of cellular communication systems. In the process of modulation, there are mismatches of the gain coefficient and the phase of the quadrature components of the signal. Mismatch degrades the Error Vector Magnitude (EVM) at the receiver, which in turn results in an increased Bit Error Rate (BER). The quality of the received signal is expressed in bit error rate. The mismatch of the amplitude and phase of the quadrature components is one of the most important factors making the greatest contribution to the amplitude of the error vector, and which must be investigated. The paper presents a research of the influence of the mismatch on the OFDM (Orthogonal frequency-division multiplexing) and UFMC (universal filtered multi-carrier) technologies. A model of the transmitter, communication channel and receiver for OFDM and UFMC signals has been developed. The model was built in the MatLab software environment. In the work, by studying the simulation model, the dependence of the noise immunity of technologies was studied by changing the parameters of the communication channel, such as the amplitude and phase mismatch of the quadrature components of the signal, as well as the signal-to-noise ratio. Also, a comparative analysis of such signal parameters as the occupied bandwidth, peak to average ratio, frequency of occurrence of bits with an error was carried out. Based on the results of the study, graphs of the dependence of the error probability and the signal peak to average ratio on the mismatch of the quadrature components were obtained for two technologies, OFDM and UFMC. The study allows us to highlight the advantages of UFMC technology, which are expressed in spectral efficiency, noise immunity and the level of the signal peak to the average ratio.