Study of the Influence of Changing Signal Propagation Conditions in the Communication Channel on Bit Error Rate

Abstract

The transmission of the information signal through the communication channel is accompanied by the addition of additive white Gaussian noise, industrial interference, atmospheric noise, etc. In addition, the signal may have an additional frequency and phase shift caused by the movement of the receiver concerning the transmitter. The article is devoted to the study of the effect of the listed conditions on the errors number dependence in the communication channel on the signal-to-noise ratio. It also explores the possibilities of reducing the effect of signal propagation conditions in a communication channel by using symbolic synchronization, which is based on a phase-locked loop. The early-late-time and Gardner synchronization error detectors are investigated. The early-late-time synchronization error detector is 1.5 dB more efficient than the Gardner detector at low signal-to-noise ratio and has a simpler implementation scheme. An energy efficiency study of a coherent digital communication system with quadrature phase shift keying modulation at the phase shift in the propagation medium is performed. Increasing of the phase shift from 0 to 40° decreases the energy efficiency by 3 dB at low signal-to-noise ratio. The energy efficiency of a non-coherent digital quadrature phase shift keying modulation system is reduced by 10 dB at the phase shift of 30° in the propagation medium. Adding a symbolic synchronization circle compensates for the rotation of the signal constellation. Increasing of the phase shift in the propagation medium to 45° for a coherent communication system leads to reduction of the energy efficiency by 2 dB. Frequency shifting has a significant impact on the energy efficiency of the communication system. The energy efficiency of the digital communication system decreases by 10 dB when 0.1 Hz frequency offset occurs and symbolic synchronization is missing. Symbol synchronization circuit increases the energy efficiency by 7 dB with a frequency shift of 0.1 Hz. When the value of frequency offset increases, the energy efficiency of coherent communication expands. The efficiency of coherent digital communication is increased by 24 dB with the introduction of frequency shift at 2 Hz.