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CN-121984539-A - Signal processing method and system for power line carrier

CN121984539ACN 121984539 ACN121984539 ACN 121984539ACN-121984539-A

Abstract

The invention relates to the field of power line carrier communication and discloses a signal processing method and a system of a power line carrier, wherein the method comprises the steps of dividing a high-speed serial data stream to be transmitted of the power line carrier into multiple paths of parallel low-speed data streams, modulating the low-speed data streams, demodulating a signal at a receiving end, wherein the modulating comprises the steps of performing OQAM pretreatment on the multiple paths of parallel low-speed data streams, sending parallel frequency domain symbols subjected to the OQAM pretreatment to a comprehensive filter module for processing, and realizing filter bank multi-carrier modulation signals (namely FBMC modulation), the demodulating comprises the steps of performing FBMC demodulation on the signal received at the receiving end through an analysis filter module, and performing OQAM demodulation on the signal subjected to the FBMC demodulation.

Inventors

  • WU YELING
  • ZENG QI
  • LIU YOUBO

Assignees

  • 四川大学

Dates

Publication Date
20260505
Application Date
20260409

Claims (6)

  1. 1. A power line carrier signal processing method, comprising: Dividing a high-speed serial data stream to be transmitted of a power line carrier into multiple parallel low-speed data streams; a modulation process is performed on a low-speed data stream, the modulation process comprising the steps of: performing OQAM pretreatment on multiple paths of parallel low-speed data streams; sending the parallel frequency domain symbols subjected to the OQAM pretreatment to a comprehensive filter module for FBMC modulation processing; The OQAM preprocessing includes: real-imaginary part separation and time interleaving are carried out on the input complex QAM symbols, so that at any moment, each subcarrier is transmitted with a real value; multiplying the real symbol sequence by a phase factor designed according to the subcarrier and the time index through phase adjustment; The FBMC modulation process includes: Synthesizing the frequency domain symbol into a time domain waveform signal through an inverse fast Fourier transform unit; applying a comprehensive filter with excellent time-frequency localization characteristics to the time-domain waveform signal to form; and through parallel/serial conversion, the multipath parallel signals are overlapped and integrated into a single serial time domain waveform, and are coupled to a power line channel for transmission.
  2. 2. The method of claim 1, further comprising a demodulation process of the signal at the receiving end, the demodulation process comprising: performing FBMC demodulation processing on the signal received by the receiving end through an analysis filter module; performing OQAM demodulation on the signal subjected to the FBMC demodulation treatment; the FBMC demodulation process includes: The signal received by the receiving end is transmitted to an analysis filter matched with the transmitting end for filtering through serial/parallel conversion, and then each subcarrier signal is converted back to the frequency domain; the OQAM demodulation includes: multiplying the signal received by the receiving end by the conjugate of the phase factor in the signal processing of the transmitting end; Recovering the transmitted real symbols by taking the real part; and (3) converting real numbers into complex numbers, recombining the real numbers recovered at the front moment and the rear moment, recovering the original complex number QAM symbols, and outputting a final original data stream.
  3. 3. The method for processing a signal of a power line carrier according to claim 2, wherein the modulation algorithm of the modulation process comprises: The method comprises the steps of carrying out OQAM preprocessing on complex QAM symbols, wherein an original complex QAM symbol is c m,n =a m,n +jb m,n , c m,n is the original complex QAM symbol, a m,n is a real part sequence of the original complex QAM, b m,n is an imaginary part sequence of the original complex QAM, m is a subcarrier index, n is symbol time, j represents an imaginary number unit, and the separation mapping of the real part and the imaginary part is as follows: ; Where d m,n is the (m, n) th element of the complex sequence, a m,n/2 is the real sequence, b m,(n-1)/2 imaginary sequence; The phase rotation factor θ m,n is set to satisfy: ; The final complex OQAM symbol is: ; s m,n is denoted as the final complex OQAM symbol on subcarrier m and symbol n; the PHYDYAS prototype filter g (t), PHYDYAS prototype filter was designed with the time domain expression: , Wherein K represents an overlap factor, T represents a time variable, T represents a symbol width, H k is a frequency domain coefficient, K is an overlap factor sequence number, A is a normalization constant, and a function rect ()' is a unit rectangular window function; The signals on each path of carrier wave are overlapped to obtain a transmission signal through M/2 point up-sampling, filter assembly and carrier modulation, and the transmission signal of a transmitting end is expressed as: ; Wherein g (,) is PHYDYAS prototype filter, M represents subcarrier number, and phase factor , Is the primary phase of the crystal, and the phase of the crystal is the primary phase of the crystal, Representing the subcarrier spacing of the filter bank; The transmission signal is transmitted through a power line channel, and the channel is described by adopting Manfred-Kostas multipath models; The transmission signal is modulated and transmitted through a power line channel, and the power line receiving end receives a signal r (t) as follows: ; where h (t) represents the time domain transfer function of the multipath model of the power line channel Manfred-Kostas, n k represents the background noise, Representing time domain convolution calculation, s (t) represents a transmission signal of the transmitting end.
  4. 4. A method of power line carrier signal processing according to claim 3, wherein the frequency domain representation of the Manfred-Kostas multipath model: , Wherein N represents the number of PLC paths, g i represents the attenuation coefficient of the path i, b 0 is a frequency independent attenuation constant, b 1 is a frequency dependent attenuation constant, l represents the index of the attenuation factor, d i represents the length of the path i, v p represents the transmission speed of the signal, H (f) is a frequency domain model of the power line carrier channel, and f is the frequency; the power line carrier channel has background noise n k , synthesized by gaussian background white noise and impulse interference: n k =w k +i k ; Wherein w k is Gaussian background white noise satisfying Gaussian distribution, denoted as , Is the variance of w k , i k is the impulse interference expressed as follows: i k =b k v k , Wherein b k represents a Bernoulli sequence with occurrence probability p b , v k represents zero mean and variance Is recorded as the Gaussian sequence of (2) , Is the variance of v k ; The probability density function of n k is expressed as: ; wherein p b represents the probability of occurrence of the bernoulli sequence.
  5. 5. The method of power line carrier signal processing according to claim 4, wherein the demodulation algorithm of the FBMC demodulation process includes: And (3) performing FBMC signal demodulation on the signal of the receiving end by adopting an analysis filter bank, and processing the received signal by a matched filter: Wherein, the method comprises the steps of, Is the FBMC demodulated signal, g (∈) represents the conjugate of PHYDYAS prototype filter; the received signal expressions r (t), f (n k ) and H (f) are simplified into the above expression, and the expression of the FBMC demodulation signal under the power line channel is obtained: ; Where a p,q represents the real or imaginary part of an OQAM symbol, p is the FBMC subcarrier index, q is the time scale of the symbol, Is the conjugate function of the filter function at the time-frequency point (m, n) coordinates; The demodulation algorithm of the OQAM demodulation comprises the following steps: recombining the real parts of the symbols obtained by the FBMC demodulation processing to obtain complex OQAM demodulation symbols: ; Wherein, the Is a complex version of the OQAM demodulated symbols, Is the real part of the above formula; Is the imaginary part of the above-mentioned, Is all positive integers.
  6. 6. A power line carrier signal processing system for implementing a power line carrier signal processing method according to any one of claims 1-5, the system comprising: The preprocessing module is used for dividing a high-speed serial data stream to be transmitted of the power line carrier into multiple paths of parallel low-speed data streams; The modulation processing module is used for modulating the low-speed data stream; The demodulation processing module is used for carrying out demodulation processing on the signal of the receiving end; the modulation processing module includes: The OQAM preprocessing unit is used for carrying out OQAM preprocessing on multiple paths of parallel low-speed data streams; The FBMC modulation unit is used for sending the parallel frequency domain symbols subjected to the OQAM pretreatment to the comprehensive filter module for FBMC modulation processing; The demodulation processing module comprises: The FBMC demodulation unit is used for performing FBMC demodulation processing on the signals received by the receiving end through the analysis filter module; and the OQAM demodulation unit is used for performing OQAM demodulation on the signal subjected to the FBMC demodulation processing.

Description

Signal processing method and system for power line carrier Technical Field The invention relates to the field of power line carrier communication, in particular to a power line carrier signal processing method and system. Background With the increasing demand for communication of new power systems, power line carrier communication (PLC) has shown great potential in supporting ubiquitous metering devices, distributed energy device access and mass monitoring data transmission. But the existing PLC system has a technical bottleneck. First, the power line has a limited operating band, typically within [1.8 mhz,20mhz ], limiting the difficulty of high speed, massive data transmission through the PLC. Therefore, how to improve the spectrum utilization rate on the limited PLC frequency band is an important precondition for realizing high-speed and large-capacity data transmission. In addition, a large number of noise, pulse interference, multipath propagation, nonlinear distortion and other bad factors exist in the novel power system environment, which can lead to the attenuation and distortion of the PLC signal, and lead to the loss of data packets and the increase of the error rate. Therefore, how to optimally use the PLC channel in a complex power line attenuation interference environment and ensure the stability and high quality of data transmission is an important direction of PLC technical research. At present, the main signal transmission mode of the domestic and foreign PLC system adopts an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) modulation mode. The high-speed serial data stream is split into a plurality of low-speed parallel data streams, each of which is transmitted over an independent subcarrier. The sub-carriers are kept independent through orthogonality, so that interference between the sub-carriers is avoided. The serial-parallel conversion and orthogonal subcarrier characteristics of OFDM lead the signal to be lower than the coherent bandwidth of a PLC channel, thereby reducing the influence of frequency selective fading and improving the reliability and the frequency spectrum efficiency of communication. Although OFDM can effectively utilize spectrum resources to a certain extent, the problems of large network topology change, complex pulse interference generated by high-power electronics, easy occurrence of subcarrier frequency offset, time delay offset and the like in the novel power system exist in the OFDM, and the transmission reliability of a PLC system is reduced. In addition, OFDM requires the addition of a redundant Cyclic Prefix (CP) before and after the symbol to avoid Inter-symbol interference (Inter-Symbol Interference, ISI) caused by multipath fading, which further wastes the time-frequency resources of the PLC channel. Therefore, how to improve the robustness of the PLC system in a complex power line environment while maintaining high spectral efficiency is a bottleneck that hinders the development of PLC technology. Disclosure of Invention Therefore, in order to solve the above-mentioned shortcomings, the present invention provides a method and a system for processing a signal of a power line carrier, and the present invention provides a PLC signal transmission method with higher time-frequency efficiency and better performance, so as to improve the signal transmission quality of the PLC. In one aspect, the present invention provides a method for processing a signal of a power line carrier, including: Dividing a high-speed serial data stream to be transmitted of a power line carrier into multiple parallel low-speed data streams; a modulation process is performed on a low-speed data stream, the modulation process comprising the steps of: performing OQAM pretreatment on multiple paths of parallel low-speed data streams; sending the parallel frequency domain symbols subjected to the OQAM pretreatment to a comprehensive filter module for FBMC modulation processing; The OQAM preprocessing includes: real-imaginary part separation and time interleaving are carried out on the input complex QAM symbols, so that at any moment, each subcarrier is transmitted with a real value; multiplying the real symbol sequence by a phase factor designed according to the subcarrier and the time index through phase adjustment; The FBMC modulation process includes: Synthesizing the frequency domain symbol into a time domain waveform signal through an inverse fast Fourier transform unit; applying a comprehensive filter with excellent time-frequency localization characteristics to the time-domain waveform signal to form; and through parallel/serial conversion, the multipath parallel signals are overlapped and integrated into a single serial time domain waveform, and are coupled to a power line channel for transmission. Optionally, the method for processing a signal of a power line carrier further includes demodulation processing of a signal of a receiving en