A power line carrier signal processing method and system

Abstract

This invention relates to the field of power line carrier communication and discloses a power line carrier signal processing method and system. The method includes dividing a high-speed serial data stream to be transmitted by the power line carrier into multiple parallel low-speed data streams; modulating the low-speed data streams; and demodulating the received signal. The modulation processing includes: performing OQAM preprocessing on the multiple parallel low-speed data streams; and sending the OQAM preprocessed parallel frequency domain symbols into a comprehensive filter module for processing to achieve filter bank multi-carrier modulation (i.e., FBMC modulation). The demodulation processing includes: performing FBMC demodulation on the received signal through an analysis filter module; and performing OQAM demodulation on the FBMC demodulated signal. This invention can enhance the resistance of power line communication to multipath interference and background noise, while improving the spectral efficiency of power line carrier communication.

Description

Technical Field

[0001] This invention relates to the field of power line carrier communication, specifically a power line carrier signal processing method and system. Background Technology

[0002] With the increasing communication demands of new power systems, power line carrier communication (PLC) has shown great potential in supporting ubiquitous metering equipment, distributed energy equipment access, and massive monitoring data transmission. However, existing PLC systems face technical bottlenecks. First, the operating frequency band of power lines is limited, typically within [1.8 MHz, 20 MHz], making it difficult to transmit high-speed, massive data via PLC. Therefore, improving spectrum utilization within the limited PLC frequency band is a crucial prerequisite for achieving high-speed, high-capacity data transmission. Furthermore, the new power system environment is characterized by numerous adverse factors such as noise, impulse interference, multipath propagation, and nonlinear distortion, which can lead to PLC signal attenuation and distortion, resulting in data packet loss and increased bit error rate. Therefore, optimizing the use of PLC channels in complex power line attenuation and interference environments to ensure stable and high-quality data transmission is an important direction for PLC technology research.

[0003] Currently, the mainstream signal transmission method for PLC systems both domestically and internationally is Orthogonal Frequency Division Multiplexing (OFDM) modulation. This method divides a high-speed serial data stream into multiple low-speed parallel data streams, each transmitted via an independent subcarrier. The subcarriers maintain independence through orthogonality, avoiding interference between them. The serial-to-parallel conversion and orthogonal subcarrier characteristics of OFDM ensure that the signal is below the coherence bandwidth of the PLC channel, thereby reducing the impact of frequency-selective fading and improving communication reliability and spectral efficiency.

[0004] While OFDM can effectively utilize spectrum resources to some extent, it suffers from weaknesses in subcarrier synchronization and interference resistance. In new power systems, with significant changes in network topology and complex pulse interference generated by high-power power electronics, OFDM is prone to subcarrier frequency and time delay shifts, reducing the transmission reliability of PLC systems. Furthermore, OFDM requires redundant cyclic prefixes (CP) before and after symbols to avoid inter-symbol interference (ISI) caused by multipath fading, further wasting the time-frequency resources of the PLC channel. Therefore, improving the robustness of PLC systems in complex power line environments while maintaining high spectral efficiency remains a bottleneck hindering the development of PLC technology. Summary of the Invention

[0005] Therefore, in order to overcome the above-mentioned shortcomings, the present invention provides a power line carrier signal processing method and system. The present invention proposes a PLC signal transmission method with higher time-frequency efficiency and better performance, thereby improving the signal transmission quality of PLC.

[0006] On one hand, the present invention provides a power line carrier signal processing method, comprising:

[0007] The high-speed serial data stream to be transmitted by the power line carrier machine is divided into multiple parallel low-speed data streams.

[0008] The low-speed data stream is modulated, and the modulation process includes the following steps:

[0009] Perform OQAM preprocessing on multiple parallel low-speed data streams;

[0010] The parallel frequency domain symbols preprocessed by OQAM are sent to the integrated filter module for FBMC modulation processing.

[0011] The OQAM preprocessing includes:

[0012] The input complex QAM symbols are processed by separating the real and imaginary parts and interleaving the time, so that at any given moment, each subcarrier transmits a real value.

[0013] By adjusting the phase, the real symbol sequence is multiplied by a phase factor designed based on the subcarrier and time index;

[0014] The FBMC modulation process includes:

[0015] Frequency domain symbols are synthesized into time domain waveform signals using an inverse fast Fourier transform unit;

[0016] The time-domain waveform signal is shaped by applying a comprehensive filter with excellent time-frequency localization characteristics;

[0017] By converting parallel signals to serial signals, multiple parallel signals are superimposed and integrated into a single serial time-domain waveform, which is then coupled to the power line channel for transmission.

[0018] Optionally, the power line carrier signal processing method further includes demodulation processing of the received signal, which includes:

[0019] The received signal at the receiver is demodulated using an analysis filter module;

[0020] The signal after FBMC demodulation is then demodulated using OQAM.

[0021] The FBMC demodulation process includes:

[0022] The received signal is converted from serial to parallel and then fed into an analysis filter matched with the transmitter for filtering. Finally, each subcarrier signal is transformed back to the frequency domain.

[0023] The OQAM demodulation includes:

[0024] The received signal at the receiving end is multiplied by the conjugate of the phase factor in the signal processing at the transmitting end;

[0025] The sign of the transmitted real number can be recovered by extracting the real part.

[0026] The real-to-complex conversion reassembles the real-number symbols recovered from the two time points to recover the original complex QAM symbols, and outputs the final raw data stream.

[0027] On the other hand, the present invention also provides a power line carrier machine signal processing system for implementing the aforementioned power line carrier machine signal processing method, the system comprising:

[0028] The preprocessing module is used to divide the high-speed serial data stream to be transmitted by the power line carrier machine into multiple parallel low-speed data streams;

[0029] The modulation processing module is used to modulate low-speed data streams.

[0030] The demodulation processing module is used to demodulate the received signal.

[0031] The modulation processing module includes:

[0032] The OQAM preprocessing unit is used to perform OQAM preprocessing on multiple parallel low-speed data streams.

[0033] The FBMC modulation unit is used to send the parallel frequency domain symbols preprocessed by OQAM into the integrated filter module for FBMC modulation processing.

[0034] The demodulation processing module includes:

[0035] The FBMC demodulation unit is used to perform FBMC demodulation processing on the signal received at the receiving end through the analysis filter module;

[0036] The OQAM demodulation unit is used to perform OQAM demodulation on the signal after FBMC demodulation.

[0037] The present invention has the following advantages:

[0038] This invention discloses a power line carrier signal processing method and system, which replaces the traditional OFDM rectangular window PLC communication scheme with a real orthogonal prototype filter. The prototype filter employs a PHYDYAS design, exhibiting excellent time-frequency localization characteristics. OQAM preprocessing achieves the conversion from complex to real domain through real-imaginary part separation and time interleaving. This modulation strategy completely eliminates the need for a cyclic prefix, improves spectral efficiency, and increases the utilization of time-frequency resources in the sequence, thereby enhancing the system's spectral efficiency and anti-interference capability (reliability).

[0039] This invention also proposes using a phase factor to achieve real-domain orthogonality, avoiding inter-carrier interference. This ensures the real orthogonality condition of the FBMC / OQAM system and guarantees that matched filtering demodulation of the PLC system will not introduce additional performance degradation. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the power line carrier signal processing method of the present invention;

[0041] Figure 2 This is a basic framework diagram of the power line carrier signal processing system described in this invention;

[0042] Figure 3 It is a traditional OFDM spectrum;

[0043] Figure 4 This is a spectrum diagram processed by the power line carrier signal processing method described in this invention.

[0044] Figure 5 This is a bit error rate comparison chart (PLC multipath channel, no pulse interference);

[0045] Figure 6 This is a bit error rate comparison chart (impulse interference). p =0.03);

[0046] In the diagram: 100, OQAM preprocessing unit; 200, FBMC modulation unit; 300, FBMC demodulation unit; 400, OQAM demodulation unit. Detailed Implementation

[0047] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0048] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] As described in the background section, the mainstream signal transmission method for PLC systems both domestically and internationally is Orthogonal Frequency Division Multiplexing (OFDM) modulation. This method divides a high-speed serial data stream into multiple low-speed parallel data streams, each transmitted via an independent subcarrier. The subcarriers maintain independence through orthogonality, avoiding interference between them. The serial-to-parallel conversion and orthogonal subcarrier characteristics of OFDM ensure that the signal is below the coherence bandwidth of the PLC channel, thereby reducing the impact of frequency-selective fading and improving communication reliability and spectral efficiency.

[0050] While OFDM can effectively utilize spectrum resources to some extent, it suffers from weaknesses in subcarrier synchronization and interference resistance. In new power systems, with significant changes in network topology and complex pulse interference generated by high-power power electronics, OFDM is prone to subcarrier frequency and time delay shifts, reducing the transmission reliability of PLC systems. Furthermore, OFDM requires redundant cyclic prefixes (CP) before and after symbols to avoid inter-symbol interference (ISI) caused by multipath fading, further wasting the time-frequency resources of the PLC channel. Therefore, improving the robustness of PLC systems in complex power line environments while maintaining high spectral efficiency remains a bottleneck hindering the development of PLC technology.

[0051] Based on the above problems, this embodiment provides a power line carrier signal processing method, such as... Figure 1 The method shown includes:

[0052] Step S100: Divide the high-speed serial data stream to be transmitted by the power line carrier machine into multiple parallel low-speed data streams;

[0053] Step S200: Modulate the low-speed data stream.

[0054] The modulation process includes the following steps:

[0055] Step S210: Perform OQAM (Offset Quadrature Amplitude Modulation) preprocessing on the multi-channel parallel low-speed data stream;

[0056] Step S220: Send the OQAM preprocessed parallel frequency domain symbols into the integrated filter module for FBMC (Filter Bank Multi-Carrier) modulation processing;

[0057] The row OQAM preprocessing in step S210 includes:

[0058] Step S211: Perform real-imaginary separation and time-interleaving processing on the input complex QAM symbols so that at any given time, each subcarrier transmits a real value.

[0059] Step S212: Multiply the real number symbol sequence by a phase factor designed based on the subcarrier and time index through phase adjustment;

[0060] The FBMC modulation process in step S220 includes:

[0061] Step S221: Synthesize the frequency domain symbols into a time domain waveform signal using the inverse fast Fourier transform unit;

[0062] Step S222: Apply a comprehensive filter with excellent time-frequency localization characteristics to the time-domain waveform signal to shape it;

[0063] Step S223: Through parallel-to-serial conversion, multiple parallel signals are superimposed and integrated into a single serial time-domain waveform, which is then coupled to the power line channel for transmission.

[0064] For example, modulation of a low-speed data stream begins by dividing the high-speed serial data stream to be transmitted into M parallel low-speed data streams. Then, OQAM preprocessing is performed. First, a C2R (complex-to-real) step is used to separate the real and imaginary parts of the input complex QAM symbols and interleave them in time, ensuring that at any given time, each subcarrier transmits only a real value. Next, phase adjustment is performed, multiplying the real symbol sequence by a phase factor designed based on the subcarrier and time index. This step is crucial for achieving orthogonality in the real number field.

[0065] The parallel frequency domain symbols preprocessed by OQAM are then subjected to FBMC modulation by a synthesis filter module. An IFFT (Inverse Fast Fourier Transform) module efficiently synthesizes the frequency domain symbols into a time domain waveform. Subsequently, a synthesis filter bank applies a prototype filter with excellent time-frequency localization characteristics to the signal for shaping. This filtering operation significantly suppresses spectral sidelobes, effectively combating channel interference without the need for a cyclic prefix (CP) and improving spectral efficiency. Finally, through parallel-to-serial conversion, the multiple parallel signals are superimposed and integrated into a single serial time domain waveform, which is then coupled to the power line channel for transmission.

[0066] For example, the modulation algorithm for implementing the above modulation processing is as follows:

[0067] Step A1: Perform OQAM preprocessing on the complex QAM symbols. The core idea of ​​OQAM preprocessing is to transmit the real and imaginary parts of the complex QAM symbols separately, so that they are modulated onto orthogonal carriers that are time-shifted by half a symbol period.

[0068] Let the primitive complex number QAM be denoted as c m,n = a m,n + jb m,n ,in c m,n It is the primitive complex number QAM notation. a m,n It is the sequence of the real parts of the primitive complex number QAM. b m,n It is the sequence of the imaginary part of the primitive complex number QAM. m For subcarrier index, n For the symbol time, j The imaginary unit is represented by the following mapping:

[0069] ,

[0070] in d m,n It is the (th)th of the complex sequence m,n ) elements, a m,n / 2 It is a sequence of real parts. b m,(n-1) / 2 Imaginary part sequence.

[0071] Set phase rotation factor θ m,n satisfy:

[0072] ;

[0073] The final complex number OQAM notation is:

[0074] ;

[0075] s m,n Represented as in subcarrier m and symbols n The final complex number OQAM symbol on;

[0076] Step A2: PHYDYAS prototype filter g ( t The design, based on Nyquist pulse shaping theory, aims to minimize out-of-band leakage and maximize time-frequency convergence, employing an overlap factor. K The mechanism allows symbols to overlap in the time domain. The time-domain expression of the PHYDYAS prototype filter is:

[0077] ,

[0078] in: K Indicates the overlap factor. t It is a time variable. T The symbol period (i.e., the OQAM symbol width); H k For frequency domain coefficients, k The overlap factor index; A As a normalization constant, ensuring The function rect(⋅) is defined in [- KT / 2, KT Unit rectangular window function on [ / 2]; T This indicates the symbol width (i.e., the OQAM symbol width). The FBMC / OQAM method based on the PHYDYAS prototype filter can effectively suppress interference caused by multipath frequency offset in the PLC channel.

[0079] Step A3: respectively through M / 2-point upsampling, filter configuration, carrier modulation, and the signals on each carrier are superimposed to obtain the transmitted signal. The transmitted signal at the transmitting end is represented as:

[0080] ;

[0081] Where g(⋅) is the PHYDYAS prototype filter; M Represents the number of subcarriers; phase factor , This is the initial phase. This indicates the subcarrier spacing of the filter bank.

[0082] Step A4: The FBMC / OQAM signal is transmitted through the PLC channel. Due to reflection and refraction caused by impedance mismatch, the PLC channel exhibits complex multipath fading characteristics. Therefore, the Manfred-Kostas multipath model is used for the channel in this step. The frequency domain expression of this model is described as follows:

[0083] ;

[0084] in N Indicates the number of PLC paths. g i Representing a path i The attenuation coefficient, b 0 It is a frequency-independent attenuation constant. b 1 It is a frequency-dependent attenuation constant. l The exponent representing the decay factor, d i Representing a path i Length (transmission distance) v p Indicates the speed at which the signal is transmitted. j Represents the imaginary unit. H ( f () is the frequency domain model of the power line carrier channel. f It refers to frequency.

[0085] In addition to multipath fading, PLC channels also have background noise. Background noise consists of two components: Gaussian white noise and impulse interference.

[0086] n k = w k + i k ,

[0087] in, n k Indicates background noise. w k It is Gaussian white background noise that follows a Gaussian distribution, denoted as , yes w k variance i k Impulse interference is a type of interference that occurs when a power source experiences a sudden, transient disturbance. Gaussian white noise is continuous background noise, generated by the thermal noise produced by the continuous operation of electrical equipment. In contrast, impulse interference is caused by factors such as the switching operation of high-power electrical equipment and the random integration of a high proportion of renewable energy sources. Impulse interference is particularly pronounced in new power systems.

[0088] Impulse interference is described using a Gaussian mixture model, whose probability density function is a mixture of two Gaussian distributions. This model can characterize the random transient interference brought about by the high proportion of new energy sources in new power systems. The impulse interference is expressed as follows:

[0089] i k = b k v k ;

[0090] in, b k This indicates that the probability of occurrence is p b Bernoulli sequence; v k This indicates zero mean and variance. The Gaussian sequence, denoted as . , yes v k The variance. Due to w k and v k The pairs are independent and both are Gaussian distributed. According to the additivity of Gaussian distributions, we know that: n k With probability as p It follows a Gaussian distribution. ,in yes w k The variance. Therefore, n k The probability density function of can be expressed as a mixture of two Gaussian distributions, as follows:

[0091] ;

[0092] in, p b This represents the probability of a Bernoulli sequence occurring, i.e. P ( b k =1)= p b , P ( b k =0)=1- p b .

[0093] Step A5: The transmitted signal is modulated by FBMC / OQAM and then passes through the PLC channel. This is equivalent to combining the signal's time-domain pulse with the PLC channel response. h ( tThe received time-domain signal is obtained by performing convolution in the time domain and adding background noise, as follows:

[0094] ;

[0095] in h ( t ) represents the time-domain transfer function of the Manfred-Kostas multipath model for power line channels (i.e. Inverse Fourier Transform This represents temporal convolution computation. s ( t ) indicates the transmission signal from the transmitting end.

[0096] Compared to OFDM technology, this invention eliminates out-of-band interference and sidelobe leakage by employing an independently designed prototype filter bank (PHYDYAS filter) for subcarrier modulation. Furthermore, it achieves high-efficiency transmission without the need for a CP (Continuous Filter), improving time-frequency resource utilization and multipath fading resistance. The advantages of FBMC technology align with the characteristics of PLC channels, making it a potential future signal transmission method for PLCs. However, the extremely narrow bandwidth, specific multipath fading, and strong impulse interference characteristics of PLC channels determine that the performance of FBMC PLCs differs from that of traditional wireless FBMC systems.

[0097] For the reasons mentioned above, in one embodiment, the power line carrier signal processing method further includes step S300, demodulation processing of the received signal;

[0098] The demodulation process includes the following steps:

[0099] Step S310: Perform FBMC demodulation processing on the signal received at the receiving end through the analysis filter module;

[0100] Step S320: Perform OQAM demodulation on the signal after FBMC demodulation;

[0101] The FBMC demodulation process in step S310 includes:

[0102] The received signal is converted from serial to parallel and then fed into an analysis filter matched with the transmitter for filtering. Finally, each subcarrier signal is transformed back to the frequency domain.

[0103] The OQAM demodulation described in step S320 includes:

[0104] Step S321: Multiply the signal received at the receiving end by the conjugate of the phase factor in the signal processing at the transmitting end;

[0105] Step S322: Recover the sign of the transmitted real number by extracting the real part;

[0106] Step S323: Real number to complex number conversion. The real number symbols recovered from the two time points are recombined to recover the original complex QAM symbols, and the final original data stream is output.

[0107] For example, the demodulation process of the received signal is the reverse process of the receiver acting as the transmitter, and its signal processing flow begins with the analysis filter module. The received signal is first converted from serial to parallel, and then fed into an analysis filter matched to the transmitter for filtering to separate the signal components of each subcarrier. Subsequently, the subcarrier signals are transformed back to the frequency domain using FFT (Fast Fourier Transform). The core of demodulation lies in OQAM demodulation, which first performs phase compensation, that is, multiplying the received signal by the conjugate of the transmitter's phase factor. This process cancels out the phase rotation before channel transmission. Based on real orthogonality, the desired transmitted symbol is now completely contained within the real part of the signal, while inherent neighboring interference is isolated in the imaginary part. Therefore, by taking the real part, the transmitted real symbol can be recovered without distortion, and endogenous interference can be eliminated. Finally, the R2C (Real to Complex Conversion) step recombines the recovered real symbols from the two time points to recover the original complex QAM symbol, outputting the final original data stream.

[0108] For example, a demodulation algorithm for implementing FBMC demodulation processing includes:

[0109] Step B1: The receiver uses an analysis filter bank to demodulate the signal.

[0110] The received signal is processed by a matched filter (FBMC demodulation):

[0111] ;

[0112] in, g *( t ) represents the conjugate of the analysis filter (i.e., the PHYDYAS prototype filter function).

[0113] Step B2: The transmitted signal is represented by the transmitting end as follows:

[0114]

[0115] Substitute received signal , and then the joint probability density function f ( n k Substituting into the above equation and simplifying, we obtain the expression for the demodulated signal under power line channel conditions:

[0116] ;

[0117] in, ap,q Represents the real or imaginary part of the OQAM symbol. p For FBMC subcarrier index, q For the time scale of the symbol, At the time and frequency point ( m , n The conjugate function of the filter function at the coordinates; the orthogonality operator is defined as... ,variable x for r ( t )or n k ,variable y yes .

[0118] Demodulation algorithms that implement OQAM demodulation include:

[0119] The real parts of the symbols obtained from FBMC demodulation are recombined to obtain complex QAM symbols:

[0120] ;

[0121] in, It is the complex form of the OQAM demodulation symbol. The real part of the above expression; This is the imaginary part of the above equation. It represents all positive integers.

[0122] To address the fading and background noise characteristics of PLCs, a signal processing scheme for PLC transceivers based on FBMC / OQAM is proposed. By employing a joint design of Offset Quadrature Amplitude Modulation (OQAM) and a PHYDYAS prototype filter, and utilizing a phase factor to control the orthogonality in the real domain, both cyclic prefixes and inter-carrier interference (ICI) are suppressed. The proposed FBMC / OQAM-based method exhibits higher time-frequency utilization and stronger resistance to channel fading. Its bit error rate performance surpasses that of traditional OFDM modulation, providing a more efficient and stable signal transmission method for the evolution of future power systems.

[0123] In another embodiment, a power line carrier machine signal processing system is also provided for implementing the aforementioned power line carrier machine signal processing method, such as... Figure 2 The system shown includes:

[0124] The preprocessing module is used to divide the high-speed serial data stream to be transmitted by the power line carrier machine into multiple parallel low-speed data streams;

[0125] The modulation processing module is used to modulate low-speed data streams.

[0126] The demodulation processing module is used to demodulate the received signal.

[0127] The modulation processing module includes:

[0128] OQAM preprocessing unit 100 is used to perform OQAM preprocessing on multiple parallel low-speed data streams.

[0129] The FBMC modulation unit 200 is used to send the parallel frequency domain symbols preprocessed by OQAM into the synthesis filter module for FBMC modulation processing. For example, the synthesis filter module includes, in sequence: an IFFT transform unit, a specific filter generation unit, and a parallel / serial transform unit.

[0130] The demodulation processing module includes:

[0131] The FBMC demodulation unit 300 is used to perform FBMC demodulation processing on the signal received at the receiving end through the analysis filter module. For example, the analysis filter module includes, in sequence: a serial-to-parallel conversion unit, a specific filter generation unit, and an FFT conversion unit.

[0132] The OQAM demodulation unit 400 is used to perform OQAM demodulation on the signal after FBMC demodulation.

[0133] Compared to OFDM, FBMC (Filter Bank Multicarrier) utilizes independently designed prototype filter banks (PHYDYAS filters) for subcarrier modulation, eliminating out-of-band interference and sidelobe leakage. It achieves high-efficiency transmission without the need for a CP (Continuous Calibration) filter, improving time-frequency resource utilization and multipath fading resistance. The advantages of FBMC align well with PLC channel characteristics, making it a potential future signal transmission method for PLCs. Furthermore, addressing PLC fading and background noise characteristics, a PLC transceiver signal processing scheme based on FBMC / OQAM is proposed. By employing Offset Quadrature Amplitude Modulation (OQAM) in conjunction with a PHYDYAS prototype filter, and utilizing phase factors to control real-domain orthogonality, cyclic prefixes are eliminated while suppressing ISI (Inter-Carrier Interference) and ICI (Inter-Carrier Interference). The proposed FBMC / OQAM-based PLC system exhibits higher time-frequency utilization and stronger resistance to channel fading, with a higher bit error rate than traditional OFDM modulation, providing a more efficient and stable signal transmission method for the evolution of future power systems.

[0134] To demonstrate the effectiveness of the power line carrier signal processing method and system described in this invention, the following example is used:

[0135] In the PLC operating frequency band [1.8MHz, 20MHz], set the system parameters as follows: Total number of subcarriers M=512, effective subcarrier count 300, prototype filter overlap coefficient K =4. The MK multipath attenuation model is used to describe the PLC fading channel (4-path and 6-path), and the background noise is represented by a Gaussian mixture model. The impulse interference probability is... p =0.03 or 0.06. The performance of a power line carrier signal processing method and system proposed in this invention is compared with that of a traditional OFDM PLC system (CP length 128, 16QAM modulation), hereinafter referred to as the FBMC / OQAM PLC system or 4OQAM / 16OQAM / 64OQAM / 256OQAM modulation scheme.

[0136] Test 1: Verification of Spectral Efficiency Improvement

[0137] The spectral efficiency advantage of FBMC / OQAM over OFDM was verified through spectral analysis. Figure 3 and Figure 4 Normalized spectrum diagrams (taking 4 subcarriers as an example) of the traditional OFDM system and the FBMC / OQAM system (the technical solution of this invention) are presented respectively.

[0138] Comparison revealed that, to ensure subcarrier orthogonality, the frequency spacing of OFDM is 1 / T The main lobe of OFDM is wider; the side lobes of OFDM decay according to the sampling function, resulting in a longer tail. However, due to the non-rectangular characteristics of the filter, FBMC has higher subcarrier overlap and faster side lobe attenuation, enabling more effective use of the limited spectrum resources of PLC and improving bandwidth efficiency. In addition, since OFDM has high synchronization requirements and is sensitive to frequency offset, it needs to rely on CP to overcome the destruction of orthogonality conditions caused by time extension. However, the FBMC / OQAM system of this invention does not require CP, indicating that the FBMC / OQAM system has higher time-frequency resource efficiency.

[0139] This invention proposes an FBMC / OQAMPLC that eliminates the need for a CP through prototype filter design and improves spectral efficiency in a limited PLC frequency band [1.8MHz, 20MHz].

[0140] Test 2: Verification of resistance to multipath fading:

[0141] In a PLC multipath fading environment (without pulse interference), the bit error rate performance of the present invention FBMC / OQAM is compared with that of traditional OFDM. Figure 5 A comparison of BER curves under 4-path and 6-path channel conditions is presented.

[0142] Simulation results show that, in PLC channel multipath environments (4-path channels, 6-path channels), the FBMC / OQAM PLC method proposed in this invention consistently exhibits superior BER performance compared to OFDM PLC systems, with an approximately 2dB signal-to-noise ratio gain.

[0143] Therefore, through the special real orthogonality design of FBMC, optimized prototype filters, and receiver signal processing, the FBMC / OQAM system exhibits excellent anti-fading performance in PLC multipath environments.

[0144] Test 3: Verification of anti-pulse interference performance:

[0145] Considering PLC multipath fading and pulse interference ( p =0.03) System performance under the dual influence. Figure 6 A comparison of bit error rates under complex interference environments is presented.

[0146] Considering PLC multipath fading and pulse interference (reach rate) p The system performance under the dual influence of (=0.03) shows that the FBMC / OQAM proposed in this invention still has a 2dB gain compared to OFDM. OFDM has strict requirements for sampling time synchronization, and impulse interference can easily lead to sampling point offset and inter-carrier interference (ICI). In contrast, FBMC / OQAM is more robust to synchronization errors through phase factor design and time-frequency localization of the filter. Under the Gaussian mixture noise model, the demodulation algorithm of FBMC / OQAM can better handle impulse interference and reduce demodulation errors.

[0147] Therefore, through signal processing optimization, FBMC / OQAM technology exhibits superior anti-interference performance compared to OFDM in complex power line interference environments.

[0148] Therefore, the FBMC / OQAM PLC system design proposed in this invention can effectively resist PLC channel fading and external interference, with a lower bit error rate than traditional OFDM PLC systems. The poor performance of traditional OFDM PLC systems is due to several factors: the use of rectangular window filters in OFDM introduces spectral leakage, which reduces the spectral efficiency of the OFDM system, limiting transmission capacity within the limited PLC frequency band. Furthermore, the addition of cyclic prefixes further wastes valuable spectrum resources. In addition, OFDM's strict requirement for inter-carrier orthogonality makes it prone to inter-carrier interference in impulse interference environments, leading to degraded demodulation performance. Therefore, the performance improvement (or even degradation) of traditional OFDM PLC systems in complex power line environments is not ideal. Only by adopting the FBMC / OQAM and PLC channel joint optimization design proposed in this invention, through techniques such as replacing rectangular windows with prototype filters, achieving real-domain orthogonality, and eliminating cyclic prefix requirements, can the spectral efficiency and anti-interference capability of the PLC system be improved.

[0149] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power line carrier signal processing method, characterized in that, include: The high-speed serial data stream to be transmitted by the power line carrier machine is divided into multiple parallel low-speed data streams. The low-speed data stream is modulated, and the modulation process includes the following steps: Perform OQAM preprocessing on multiple parallel low-speed data streams; The parallel frequency domain symbols preprocessed by OQAM are sent to the integrated filter module for FBMC modulation processing. The OQAM preprocessing includes: The input complex QAM symbols are processed by separating the real and imaginary parts and interleaving the time, so that at any given moment, each subcarrier transmits a real value. By adjusting the phase, the real symbol sequence is multiplied by a phase factor designed based on the subcarrier and time index; The FBMC modulation process includes: Frequency domain symbols are synthesized into time domain waveform signals using an inverse fast Fourier transform unit; The time-domain waveform signal is shaped by applying a comprehensive filter with excellent time-frequency localization characteristics; By converting parallel signals to serial signals, multiple parallel signals are superimposed and integrated into a single serial time-domain waveform, which is then coupled to the power line channel for transmission. The modulation algorithm for the modulation processing includes: OQAM preprocessing of complex QAM symbols: Let the original complex QAM symbols be... c m,n = a m,n + jb m,n ,in, c m,n It is the primitive complex number QAM notation. a m,n It is the sequence of the real parts of the primitive complex number QAM. b m,n It is the sequence of the imaginary part of the primitive complex number QAM. m For subcarrier index, n For the symbol time, j The imaginary unit is represented by the following mapping: ； in d m,n It is the (th)th of the complex sequence m,n ) elements, a m,n / 2 It is a sequence of real parts. b m,(n-1) / 2 Imaginary part sequence; Set phase rotation factor θ m,n satisfy: ； The final complex number OQAM notation is: ； s m,n Represented as in subcarrier m and symbols n The final complex number OQAM symbol on; Design a PHYDYAS prototype filter. g ( t The time-domain expression of the PHYDYAS prototype filter is: ， in: K Indicates the overlap factor. t It is a time variable. T Indicates the symbol width. H k For frequency domain coefficients, k The overlap factor index is used. A The function rect(⋅) is a unit rectangular window function and is a normalization constant. respectively M / 2-point upsampling, filter configuration, carrier modulation, and the signals on each carrier are superimposed to obtain the transmitted signal. The transmitted signal at the transmitting end is represented as: ； in, g (⋅) represents the PHYDYAS prototype filter; M Represents the number of subcarriers; phase factor , This is the initial phase. Indicates the subcarrier spacing of the filter bank; The transmitted signal is transmitted through the power line channel, which is described by the Manfred-Kostas multipath model; The transmitted signal is modulated and transmitted through the power line channel, and the power line receiver receives the signal. r ( t ) is represented as: ； in h ( t ) represents the time-domain transfer function of the Manfred-Kostas multipath model for power line channels. n k Indicates background noise. This represents temporal convolution computation. s ( t () indicates the transmission signal from the transmitting end; Frequency domain expression of the Manfred-Kostas multipath model: ， in: N Indicates the number of PLC paths. g i Representing a path i The attenuation coefficient, b 0 It is a frequency-independent attenuation constant. b 1 It is a frequency-dependent attenuation constant. l The exponent representing the decay factor; d i Representing a path i Length; v p Indicates the speed at which the signal is transmitted; H ( f () is the frequency domain model of the power line carrier channel. f It is frequency; Power line carrier channels have background noise n k It is synthesized from Gaussian white background noise and impulse interference: n k = w k + i k ； in, w k It is Gaussian white background noise that follows a Gaussian distribution, denoted as , yes w k variance i k It is pulse interference, expressed as follows: i k = b k v k , in b k This indicates that the probability of occurrence is p b Bernoulli sequence; v k This indicates zero mean and variance. The Gaussian sequence, denoted as . , yes v k The variance; n k The probability density function is expressed as: ； in, p b This represents the probability of a Bernoulli sequence occurring. The demodulation algorithm for the FBMC demodulation process includes: The received signal is demodulated using an analytical filter bank via FBMC, and then processed by a matched filter. ;in, It is an FBMC demodulated signal. g *(⋅) denotes the conjugate of the PHYDYAS prototype filter; The received signal expression r ( t ), f ( n k )and H ( f Substituting into the above equation and simplifying, we obtain the expression for the FBMC demodulated signal under power line channel conditions: ； in, a p,q Represents the real or imaginary part of the OQAM symbol. p For FBMC subcarrier index, q For the time scale of the symbol, At the time and frequency point ( m , n The conjugate function of the filter function at the coordinates; The OQAM demodulation algorithm includes: The real parts of the symbols obtained from FBMC demodulation are recombined to obtain complex OQAM demodulation symbols: ； in, It is the complex form of the OQAM demodulation symbol. The real part of the above expression; This is the imaginary part of the above equation. It represents all positive integers.

2. The power line carrier signal processing method according to claim 1, characterized in that, It also includes demodulation processing of the received signal, which includes: The received signal at the receiver is demodulated using an analysis filter module; The signal after FBMC demodulation is then demodulated using OQAM. The FBMC demodulation process includes: The received signal is converted from serial to parallel and then fed into an analysis filter matched with the transmitter for filtering. Finally, each subcarrier signal is transformed back to the frequency domain. The OQAM demodulation includes: The received signal at the receiving end is multiplied by the conjugate of the phase factor in the signal processing at the transmitting end; The sign of the transmitted real number can be recovered by extracting the real part. The real-to-complex conversion reassembles the real-number symbols recovered from the two time points to recover the original complex QAM symbols, and outputs the final raw data stream.

3. A power line carrier signal processing system, characterized in that, For implementing the power line carrier signal processing method as described in claim 1 or 2, the system comprises: The preprocessing module is used to divide the high-speed serial data stream to be transmitted by the power line carrier machine into multiple parallel low-speed data streams; The modulation processing module is used to modulate low-speed data streams. The demodulation processing module is used to demodulate the received signal. The modulation processing module includes: The OQAM preprocessing unit is used to perform OQAM preprocessing on multiple parallel low-speed data streams. The FBMC modulation unit is used to send the parallel frequency domain symbols preprocessed by OQAM into the integrated filter module for FBMC modulation processing. The demodulation processing module includes: The FBMC demodulation unit is used to perform FBMC demodulation processing on the signal received at the receiving end through the analysis filter module; The OQAM demodulation unit is used to perform OQAM demodulation on the signal after FBMC demodulation.

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