Research On Equalization Algorithm For OFDM/OQAM In Power Line Communication System

Aiming at the problem of frequency mask and low spectrum efficiency in power line communication(PLC)orthogonal frequency division multiplexing(OFDM)system.It is proposed to apply the orthogonal frequency division multiplexing/offset quadrature amplitude modulation(OFDM/OQAM)technology to the PLC system.However,this technology will cause severe self-interference in PLC multipath channels.In addition,there exists impulse noise whose amplitudes fluctuate greatly.However,the traditional equalization algorithm cannot effectively eliminate the inherent interference and impulsive interference.In view of this problem,the channel equalization algorithm of the power line OFDM/OQAM communication system is studied in this thesis,and the corresponding solution is put forward.First of all,the linear channel equalization algorithm for OFDM/OQAM in power line communication system is introduced in detail.After analyzing the reason for the existence of the inherent interference,the inhibiting ability of several traditional linear equalization algorithms to the inherent interference is compared,the results show that the inhibitory effects are weak.On this basis,two kinds of improved minimum mean square error equalization algorithms are introduced.The accuracy of the equalization is improved by estimating the interference power,but the calculation workload of interference power is larger.For this problem,a simplified calculation method of interference power is proposed.This method only needs the received signal and channel frequency response to calculate the interference power,which is simple and convenient to implement.Then,the nonlinear channel equalization algorithm for OFDM/OQAM in power line communication system is studied carefully.Aiming at the inherent interference of the system,an interference cancellation equalization algorithm based on channel phase preprocessing is proposed,and the interference component can be reduced when the received signal is multiplied by a channel phase adjustment factor.Compared with the existing interference cancellation equalization algorithm,the complexity is dramatically decreased.In addition,aiming at the impulsive interference of the system,an interference cancellation equalization algorithm for impulse noise is proposed.The algorithm uses the initial equalization result in frequency domain to reconstruct the impulse interference,which effectively restrains its impact on the equalization performance.On this basis,adding the denoising processing in the time domain can further improve the performance of equalization.Finally,aiming at the inherent interference and impulsive interference existing in the power line OFDM/OQAM communication system,two optimal algorithms which respectively consider the two interferences are combined to design the overall channel equalization solution.The simulation results show that the proposed equalization scheme can achieve the performance improvement of 1.5 dB compared with the impulse noise cancellation equalization scheme which only considers the impulse interference.And compared with the channel phase preconditioning equalization scheme which only considers the inherent interference,the proposed scheme can achieve the performance improvement of 9.5 dB,thus verifying the feasibility of the entire equalization scheme.