A broadband multicarrier ranging method and system based on power line communication

Abstract

The application discloses a broadband multicarrier ranging method and system based on power line communication, and relates to the technical field of broadband power line carrier communication, and comprises the following steps: setting a source node and a destination node in a power line network, and configuring a power line coupler; setting orthogonal frequency division multiplexing signal parameters, determining a channel coherence bandwidth based on a power line channel multipath delay time; calculating a subcarrier frequency interval according to the bandwidth and the center frequency, and selecting two subcarriers with an interval greater than the coherence bandwidth as ranging subcarriers; sending the ranging subcarrier signals by the source node, receiving and extracting phase information by the destination node; calculating an initial distance value according to the sending and receiving phase information; when the difference between the initial distance values corresponding to the two ranging subcarriers satisfies a preset threshold value, taking the average value as the final distance, and when the difference does not satisfy the preset threshold value, triggering phase observation value fusion to recalculate the final distance. The application improves the ranging precision and reliability in the power line network.

Description

Technical Field

[0001] This invention relates to the field of broadband power line carrier communication technology, specifically to a broadband multi-carrier ranging method and system based on power line communication. Background Technology

[0002] Low-voltage distribution areas, as the "last mile" of the power system, directly provide electricity to residential and industrial users. Their complex line topology and frequent environmental changes lead to dynamic variations in cable length and a high incidence of faults. Ring main units, distribution boxes, and other equipment are densely distributed in urban underground spaces and residential areas. However, low-voltage distribution area cables often use unshielded structures, have numerous branch nodes, and experience significant load fluctuations. These factors increase the difficulty for maintenance personnel in diagnosing cable installation and fault location. Traditional ranging techniques often involve the source node sending a ranging initiation frame to the target node. The target node receives the frame and calculates the transmission delay based on its local reception time and the transmission time information carried in the frame, thus estimating the transmission distance between the two ends. While this method is widely used in wireless communication and industrial scenarios, it has significant limitations in the special communication medium of power lines. Because it does not consider the differences in frequency and reference time between different nodes, the calculated transmission time is inaccurate. Therefore, how to accurately perform power line ranging remains a problem that urgently needs to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide a broadband multi-carrier ranging method and system based on power line communication, aiming to solve at least one of the technical problems existing in the prior art.

[0004] The technical solution of this invention is: a broadband multi-carrier ranging method based on power line communication, comprising the following steps: A multi-carrier ranging system is constructed by setting up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. Set the bandwidth, center frequency, and number of subcarriers parameters of the orthogonal frequency division multiplexing signal, and determine the coherent bandwidth of the power line channel based on the multipath delay time of the power line channel; The subcarrier frequency interval is calculated based on the bandwidth and center frequency. Two subcarriers with a frequency interval greater than the coherent bandwidth of the power line channel are selected as ranging subcarriers to generate a ranging subcarrier signal containing the transmission phase information. The source node transmits a ranging subcarrier signal through a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information. Based on the transmitted and received phase information, the channel transmission cycle number and phase difference of the ranging subcarrier are calculated to obtain the initial distance value. The difference between the initial distance values ​​corresponding to the two ranging subcarriers is compared. When the difference meets the preset difference threshold, the average of the two initial distance values ​​is calculated as the final distance. When the difference does not meet the preset difference threshold, the phase observation value fusion is triggered to recalculate the final distance.

[0005] A multi-carrier ranging system is constructed by setting up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. In the power line network, the ranging area is determined, and the distribution information of the power supply circuits within the ranging area is obtained; Based on the power supply circuit distribution information, the first location point with an independent power supply circuit is selected as the source node; Based on the power supply circuit distribution information, a second location point that is in the same power supply circuit as the source node is selected and set as the destination node; Power line couplers are connected to the source node and the destination node respectively. The power line coupler includes a high-pass filter unit and an impedance matching unit. The source node and destination node are connected to the power line network via a power line coupler to complete the construction of a multi-carrier ranging system.

[0006] Determining the coherent bandwidth of a power line channel based on its multipath delay time includes: The source node sends a pulse probe signal to the power line network through a power line coupler, and the destination node receives the pulse probe signal transmitted through the power line channel. The destination node identifies the first and last arriving pulses in the received pulse probe signal, calculates the time interval between the first and last arriving pulses, and determines the time interval as the power line channel multipath delay time. The reciprocal of the multipath delay time of the power line channel is determined as the coherent bandwidth of the power line channel.

[0007] The subcarrier frequency spacing is calculated based on bandwidth and center frequency. Two subcarriers with a frequency spacing greater than the coherence bandwidth of the power line channel are selected as ranging subcarriers. The ranging subcarrier signal containing the transmission phase information is generated as follows: Construct a frequency response curve based on bandwidth and center frequency, mark peak points on the frequency response curve, and calculate the subcarrier frequency spacing between adjacent peak points. The frequency response curve is divided into multiple frequency bands based on the subcarrier frequency spacing, and the response amplitude within each frequency band is calculated. Based on the response amplitude, frequency band intervals are selected to obtain frequency band intervals where the subcarrier frequency spacing is greater than the coherence bandwidth of the power line channel; The channel attenuation is measured within the selected frequency bands, and the two frequency bands with the smallest channel attenuation are selected. The center point of the two selected frequency bands is taken as the ranging subcarrier. The transmitted phase information is modulated onto the ranging subcarrier to generate a modulated ranging subcarrier signal; A cyclic prefix is ​​added to the modulated ranging subcarrier signal and bandpass filtered to obtain a ranging subcarrier signal containing the transmission phase information.

[0008] The source node transmits a ranging subcarrier signal via a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information, including: The channel transmission status in the power line is detected at the source node to obtain channel status parameters. The ranging subcarrier signal is compensated according to the channel state parameters to generate a compensated ranging signal. Power frequency suppression is applied to the compensated ranging signal to generate a power frequency suppressed ranging signal; The impedance characteristics are adjusted according to the channel state parameters, and the ranging signal after suppressing the power frequency is sent to the power line through the power line coupler; The target node acquires ranging subcarrier signals from the power line; The synchronization marker is identified from the acquired ranging subcarrier signal, the sampling position is determined based on the synchronization marker, the waveform data of the ranging subcarrier signal is obtained at the sampling position, and the reference signal is constructed using the waveform data. The phase difference is obtained by comparing the ranging subcarrier signal with the reference signal, and the phase compensation value introduced by the channel is calculated based on the channel state parameters. The phase difference is compensated for by the phase compensation value to obtain the received phase information.

[0009] Based on the transmitted and received phase information, the channel transmission cycle number and phase difference of the ranging subcarrier are calculated respectively to obtain the initial distance values, including: The phase change is obtained by performing a difference operation on the transmitted and received phase information; The phase continuity is detected based on the phase change amount, the phase jump interval is determined, the phase continuous change interval is generated, and the phase cumulative value is calculated within the phase continuous change interval. The phase accumulation value is segmented according to the signal periodicity characteristics of the ranging subcarrier, and the number of channel transmission cycles is determined based on the segmentation results. The phase difference is obtained by matching the accumulated phase value with the number of channel transmission cycles. The initial distance value is calculated based on the frequency characteristics of the ranging subcarrier, combined with the number of channel transmission cycles and the phase difference.

[0010] Compare the differences between the initial distance values ​​corresponding to the two ranging subcarriers. If the difference meets a preset difference threshold, calculate the average of the two initial distance values ​​as the final distance. If the difference does not meet the preset difference threshold, trigger phase observation fusion to recalculate the final distance, including: Extract the initial distance values ​​corresponding to the two ranging subcarriers, calculate the fluctuation parameters of the initial distance values ​​to generate the distance difference, and normalize the distance difference to obtain the standardized difference value. The standardized difference value is compared with a preset difference threshold to generate a comparison result identifier; When the comparison result indicates that the standardized difference value meets the preset difference threshold, the signal amplitude and noise amplitude of the two ranging subcarriers are extracted, a weighting coefficient is generated based on the signal amplitude and noise amplitude, and the initial distance values ​​corresponding to the two ranging subcarriers are weighted and averaged using the weighting coefficient to obtain the final distance. When the comparison result indicates that the standardized difference value does not meet the preset difference threshold, the phase observation values ​​of the two ranging subcarriers are extracted, the amplitude features are extracted based on the phase observation values, and the observation weights are calculated. The phase observations are fused according to the observation weights to obtain a fused phase value, which is then converted into the final distance.

[0011] This invention provides a broadband multi-carrier ranging system based on power line communication, the system comprising: The setup unit is used to construct a multi-carrier ranging system, which sets up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. The parameter configuration unit is used to set the bandwidth, center frequency, and number of subcarriers of the orthogonal frequency division multiplexing signal, and to determine the coherent bandwidth of the power line channel based on the multipath delay time of the power line channel. The subcarrier selection unit is used to calculate the subcarrier frequency interval based on the bandwidth and center frequency, select two subcarriers with a frequency interval greater than the coherent bandwidth of the power line channel as ranging subcarriers, and generate a ranging subcarrier signal containing transmission phase information. The signal transceiver unit is used to transmit a ranging subcarrier signal through the source node via a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information. The distance calculation unit is used to calculate the channel transmission cycle number and phase difference of the ranging subcarrier based on the transmitted phase information and the received phase information, respectively, to obtain the initial distance value; The distance fusion unit is used to compare the difference between the initial distance values ​​corresponding to two ranging subcarriers. When the difference meets the preset difference threshold, the average of the two initial distance values ​​is calculated as the final distance. When the difference does not meet the preset difference threshold, the phase observation value fusion is triggered to recalculate the final distance.

[0012] One technical solution provided in this embodiment of the invention is an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps in any of the aforementioned methods.

[0013] One technical solution provided in this embodiment of the invention is a computer-readable storage medium storing computer program instructions, which, when executed by a processor, implement the steps in any of the aforementioned methods.

[0014] This invention constructs a multi-carrier ranging system in a power line network. It determines the channel coherence bandwidth based on the multipath delay time of the power line channel and selects ranging subcarriers with frequency intervals greater than the coherence bandwidth, effectively avoiding the impact of channel frequency-selective fading on ranging accuracy. Efficient transmission and reception of ranging signals are achieved by configuring power line couplers, improving the system's ranging performance. An orthogonal frequency division multiplexing (OFDM) signal design scheme ensures the orthogonality of the ranging subcarrier signals and reduces inter-subcarrier interference. An adaptive fusion mechanism based on phase observations is designed; when there is a significant difference in the initial distance values ​​corresponding to the ranging subcarriers, phase observation fusion is triggered for recalculation, improving the reliability of the ranging results. This invention fully considers the characteristics of the power line channel, achieving high-precision ranging and can be widely applied to distance measurement scenarios in power line communication networks. Attached Figure Description

[0015] Figure 1 A flowchart illustrating a broadband multi-carrier ranging method based on power line communication, provided for an embodiment of the present invention; Figure 2 This is a schematic diagram of the ranging system according to an embodiment of the present invention; Figure 3 This is a diagram of the frame format file for the ranging subcarrier in an embodiment of the present invention. Detailed Implementation

[0016] like Figure 1 As shown, Figure 1 A flowchart of a broadband multi-carrier ranging method based on power line communication is provided for an embodiment of the present invention. The method includes the following steps: A multi-carrier ranging system is constructed by setting up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. Set the bandwidth, center frequency, and number of subcarriers parameters of the orthogonal frequency division multiplexing signal, and determine the coherent bandwidth of the power line channel based on the multipath delay time of the power line channel; The subcarrier frequency interval is calculated based on the bandwidth and center frequency. Two subcarriers with a frequency interval greater than the coherent bandwidth of the power line channel are selected as ranging subcarriers to generate a ranging subcarrier signal containing the transmission phase information. The source node transmits a ranging subcarrier signal through a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information. Based on the transmitted and received phase information, the channel transmission cycle number and phase difference of the ranging subcarrier are calculated to obtain the initial distance value. The difference between the initial distance values ​​corresponding to the two ranging subcarriers is compared. When the difference meets the preset difference threshold, the average of the two initial distance values ​​is calculated as the final distance. When the difference does not meet the preset difference threshold, the phase observation value fusion is triggered to recalculate the final distance.

[0017] A multi-carrier ranging system is constructed by setting up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. In the power line network, the ranging area is determined, and the distribution information of the power supply circuits within the ranging area is obtained; Based on the power supply circuit distribution information, the first location point with an independent power supply circuit is selected as the source node; Based on the power supply circuit distribution information, a second location point that is in the same power supply circuit as the source node is selected and set as the destination node; Power line couplers are connected to the source node and the destination node respectively. The power line coupler includes a high-pass filter unit and an impedance matching unit. The source node and destination node are connected to the power line network via a power line coupler to complete the construction of a multi-carrier ranging system.

[0018] In power line networks, determining the ranging area is crucial. This area typically encompasses a specific power line network coverage zone, such as the power supply network within a residential area, office building, or industrial park. Obtaining power supply circuit distribution information within the ranging area requires collecting power line topology data, including power line routing diagrams, transformer locations, and power supply branch connections. A power line network analyzer can be used to scan the target area, collecting data such as power line impedance characteristics, signal attenuation parameters, and noise interference. In a power line network ranging application for an office building, a power line network analyzer revealed that the building has three independent power supply circuits, each covering different areas of the building. The impedance characteristics and attenuation parameters of each circuit were recorded.

[0019] Based on the acquired power supply circuit distribution information, the first location point with an independent power supply circuit is selected as the source node. The selection of the source node must meet the requirements of signal transmission stability and coverage. Typically, a location with low interference and stable voltage in the power line network is chosen as the source node. The source node is usually placed near a distribution box or power junction box, where power line connections are stable and equipment is easy to install. In the aforementioned office building application example, the incoming end of the first power supply circuit in the main distribution room was selected as the source node location. At this location, the voltage is stable at 220V, noise interference is less than -60dB, and signal transmission conditions are good.

[0020] After selecting the source node, a second location point on the same power supply circuit as the source node is selected based on the power supply circuit distribution information and set as the destination node. The selection of the destination node needs to consider its electrical connectivity with the source node and signal transmission quality. The destination node is usually set near the terminal device where the distance needs to be measured, such as a smart meter, smart socket, or power monitoring equipment. In the aforementioned office building example, a wall socket in an office within the coverage area of ​​the first power supply circuit is selected as the destination node. This socket has good electrical connectivity with the source node, and the received signal strength is greater than -50dB.

[0021] After the source and destination nodes are determined, power line couplers are connected to both nodes to achieve effective coupling between the ranging signal and the power line network. The power line coupler includes a high-pass filter unit and an impedance matching unit. The high-pass filter unit filters out power frequency signals and low-frequency interference signals on the power line, allowing only the high-frequency signal required for ranging to pass through. The high-pass filter unit consists of capacitors and inductors, with a cutoff frequency set at approximately 1MHz and an attenuation slope greater than 40dB / decade. The impedance matching unit matches the impedance between the signal transmitting and receiving circuits and the power line, reducing reflection loss and improving signal transmission efficiency. The impedance matching unit typically consists of a transformer and an RC network, matching the output impedance of the signal circuit to the characteristic impedance range of the power line. The characteristic impedance of the power line is approximately 85 to 115Ω; the impedance matching unit converts the 50Ω output impedance of the ranging device to this range, controlling reflection loss below -20dB.

[0022] After the power line coupler is connected, the source and destination nodes are connected to the power line network through the coupler, completing the construction of the multi-carrier ranging system. The ranging system employs multi-carrier technology, selecting multiple frequency points within the power line communication band as carriers and simultaneously transmitting ranging signals. Multi-carrier technology effectively addresses the frequency-selective attenuation problem in power line networks, improving ranging accuracy and reliability. Multiple frequency points within the 2-30MHz band are selected as carrier frequencies, with a frequency spacing of 500kHz. The signal power at each frequency point is controlled within the range of -30 to -55dBm, meeting the radiation limits for power line communication equipment. The multi-carrier signal is generated using orthogonal frequency division multiplexing (OFDM) technology, maintaining orthogonality between subcarriers and reducing mutual interference. The source node transmits a multi-carrier signal containing ranging information, and the destination node receives and demodulates the signal, calculating the distance between the two nodes by measuring the signal transmission delay.

[0023] After the multi-carrier ranging system is constructed, the source node begins sending a ranging request signal to the power line network. This signal includes the source node identifier, destination node identifier, and timestamp information. The request signal uses wideband modulation and is transmitted simultaneously on multiple carrier frequencies to improve signal transmission reliability. The source node records the transmission timestamp, accurate to the nanosecond level. Upon receiving the ranging request signal, the destination node immediately generates and sends a response signal. This response signal includes the destination node identifier, reception timestamp, and transmission timestamp information. After receiving the response signal, the source node calculates the round-trip time based on the timestamp information and, combined with the power line signal propagation speed parameter, calculates the actual distance between the two nodes. The signal propagation speed in a power line network is affected by cable characteristics; an appropriate propagation speed parameter is selected based on the cable type, typically 60% to 70% of the speed of electromagnetic waves in a vacuum.

[0024] The ranging signal processing employs correlation detection technology to improve the accuracy of time delay measurement. The ranging signal transmitted by the source node contains a specific sequence. After receiving the signal, the destination node uses a matched filter to detect the signal and determine its arrival time. In noisy environments, multiple measurements can be taken and averaged to improve ranging accuracy. The power line environment is complex and variable; therefore, the impact of load changes on signal transmission must be considered during ranging. Under conditions of significant load variations, the transmission power of the ranging signal can be increased or the carrier frequency distribution adjusted to ensure reliable transmission.

[0025] The processing of ranging results needs to consider the influence of the power line network topology. Under complex topologies, signals may propagate via multiple paths, leading to errors in the ranging results. The solution is to use frequency domain analysis methods, which analyze the propagation characteristics of carriers at different frequencies, identify the direct path and the reflection path, and extract the time delay information of the direct path for distance calculation.

[0026] This invention presents a broadband multi-carrier ranging method based on power line communication, enabling distance measurement using existing power line networks without additional wiring, significantly reducing deployment costs and complexity. Multi-carrier technology effectively overcomes the frequency-selective attenuation characteristics of power line channels, improving the interference resistance and transmission reliability of the ranging signal. High-pass filtering and impedance matching techniques ensure efficient signal coupling to the power line network, reducing transmission loss.

[0027] Determining the coherent bandwidth of a power line channel based on its multipath delay time includes: The source node sends a pulse probe signal to the power line network through a power line coupler, and the destination node receives the pulse probe signal transmitted through the power line channel. The destination node identifies the first and last arriving pulses in the received pulse probe signal, calculates the time interval between the first and last arriving pulses, and determines the time interval as the power line channel multipath delay time. The reciprocal of the multipath delay time of the power line channel is determined as the coherent bandwidth of the power line channel.

[0028] Coherent bandwidth measurement in power line networks is crucial for the design of power line communication systems. This parameter can be obtained by analyzing the signal transmission characteristics between the source and destination nodes. The source node is equipped with a power line coupler to inject high-frequency measurement signals into the power line network and isolate power frequency voltage. The power line coupler includes a high-pass filter and an impedance matching unit. The cutoff frequency of the high-pass filter is set to 1MHz, effectively filtering out 50Hz or 60Hz power frequency signals. The impedance matching unit ensures impedance matching between the signal source and the power line network, typically converting a 50Ω signal source impedance to the characteristic impedance of the power line network, which usually varies between 85Ω and 115Ω.

[0029] The source node generates a pulse probe signal and injects it into the power line network via a power line coupler. The pulse probe signal is a high-frequency, narrow-pulse signal with a sufficiently wide spectral coverage; typically, the pulse width is 50 ns, and the signal power is controlled within the range of -30 dBm to -20 dBm, meeting the radiation limits for power line communication equipment. Before signal transmission, the source node records a precise transmission timestamp with nanosecond-level accuracy, providing a benchmark for subsequent delay analysis. The pulse signal is transmitted periodically at 100 ms intervals, and the power line channel status is checked before each transmission to avoid sudden interference on the power line.

[0030] When a pulse probe signal propagates in a power line network, it is affected by factors such as network topology, line impedance discontinuities, and load impedance variations, resulting in multipath propagation. The signal reaches the destination node along different propagation paths, each with varying propagation delays and attenuation characteristics, causing the destination node to receive a series of temporally dispersed pulse signals. In the test environment of a residential building, due to the complex power line network structure containing multiple branches and load points, the pulse signal exhibited a significant multipath effect during propagation.

[0031] The destination node is also equipped with a power line coupler to extract high-frequency measurement signals from the power line network. Upon receiving the pulse probe signal, the destination node performs signal acquisition and processing. High-speed sampling technology is used for signal acquisition, with a sampling rate set to 100MHz to ensure accurate capture of the pulse signal. The acquired signal undergoes bandpass filtering, with a passband range of 2MHz to 30MHz, to suppress power frequency interference and high-frequency noise, thereby improving the signal-to-noise ratio.

[0032] The target node processes the acquired signal, identifying the first and last arriving pulses in the received pulse detection signal. Signal processing employs a threshold detection method, setting an appropriate signal detection threshold, typically three times the average noise power. When the amplitude of the received signal exceeds the detection threshold, it is considered a valid pulse signal. To improve detection reliability, the detected pulses are verified, including pulse width verification and pulse shape matching, to eliminate possible false pulse detections. In the aforementioned residential building test environment, with a threshold value of -60 dBm, all pulse components of multipath propagation were successfully detected.

[0033] The destination node records the arrival time of each detected pulse and determines the first and last arriving pulses based on signal amplitude, arrival time, and pulse shape characteristics. The first arriving pulse typically corresponds to a signal transmitted via a direct path, with a shorter propagation delay and relatively higher signal strength. The last arriving pulse corresponds to a signal that arrives at the receiver after multiple reflections, with a longer propagation delay and relatively weaker signal strength. For example, the dynamic range of signal detection is set to 30dB, meaning only pulses with signal strength within 30dB below the strongest pulse signal are considered. This eliminates excessively weak multipath components and improves measurement reliability.

[0034] The destination node calculates the time interval between the first and last arriving pulses, and this time interval is determined as the multipath delay time of the power line channel. The multipath delay time reflects the time spread characteristics of signal propagation in the power line channel and is an important parameter characterizing the channel's time-domain properties. To improve measurement accuracy, multiple measurements can be performed and the average value taken, or statistical methods can be used to analyze the distribution characteristics of multiple measurement results. In the aforementioned residential building test environment, after 10 repeated measurements, the average multipath delay time was 1.2 μs, with a standard deviation of less than 0.1 μs, indicating good consistency in the measurement results.

[0035] The reciprocal of the multipath delay time of the power line channel is determined as the coherence bandwidth of the power line channel. Coherence bandwidth is an important parameter characterizing the channel's frequency domain characteristics; it refers to the maximum bandwidth through which the channel's frequency response maintains a high degree of correlation. In the aforementioned test environment, based on the measured multipath delay time of 1.2 μs, the coherence bandwidth was calculated to be approximately 833 kHz. The magnitude of the coherence bandwidth directly affects the subcarrier design and modulation scheme selection of the power line communication system. When the communication signal bandwidth is less than the coherence bandwidth, the channel's impact on the signal manifests as flat fading; when the communication signal bandwidth is greater than the coherence bandwidth, the channel's impact on the signal manifests as frequency-selective fading.

[0036] After obtaining the coherent bandwidth, the parameters of the power line multi-carrier communication system can be configured according to actual communication requirements. In multi-carrier communication systems, the subcarrier bandwidth is usually set smaller than the coherent bandwidth to reduce the impact of frequency-selective fading on communication performance. For the aforementioned test environment, the subcarrier bandwidth can be set to 500kHz to ensure that each subcarrier experiences approximately flat fading within its respective frequency band, simplifying equalization design. Simultaneously, based on the size of the coherent bandwidth, the channel coding scheme and modulation level can be rationally configured to improve spectrum utilization efficiency while ensuring communication reliability.

[0037] This invention presents a method for determining the coherent bandwidth of a power line channel based on its multipath delay time. This method is characterized by its simplicity and high measurement accuracy. By analyzing the multipath characteristics of the power line channel, the coherent bandwidth parameters are accurately obtained, providing crucial information for the design of power line communication systems. This method eliminates the need for complex frequency domain scanning equipment; it acquires channel frequency domain characteristics solely through time-domain pulse signal measurements, significantly simplifying the measurement process and reducing equipment requirements. The obtained coherent bandwidth parameters can directly guide the configuration of multicarrier parameters in power line communication systems, including subcarrier bandwidth design, modulation scheme selection, and coding scheme optimization, effectively improving the transmission efficiency and reliability of communication systems in complex power line environments.

[0038] The subcarrier frequency spacing is calculated based on bandwidth and center frequency. Two subcarriers with a frequency spacing greater than the coherence bandwidth of the power line channel are selected as ranging subcarriers. The ranging subcarrier signal containing the transmission phase information is generated as follows: Construct a frequency response curve based on bandwidth and center frequency, mark peak points on the frequency response curve, and calculate the subcarrier frequency spacing between adjacent peak points. The frequency response curve is divided into multiple frequency bands based on the subcarrier frequency spacing, and the response amplitude within each frequency band is calculated. Based on the response amplitude, frequency band intervals are selected to obtain frequency band intervals where the subcarrier frequency spacing is greater than the coherence bandwidth of the power line channel; The channel attenuation is measured within the selected frequency bands, and the two frequency bands with the smallest channel attenuation are selected. The center point of the two selected frequency bands is taken as the ranging subcarrier. The transmitted phase information is modulated onto the ranging subcarrier to generate a modulated ranging subcarrier signal; A cyclic prefix is ​​added to the modulated ranging subcarrier signal and bandpass filtered to obtain a ranging subcarrier signal containing the transmission phase information.

[0039] After connecting to the power line network, the ranging device first acquires the bandwidth and center frequency. The available frequency band for power line communication is typically 2MHz to 30MHz; in practical applications, an appropriate band can be selected based on the power line communication regulations of each country. Taking a residential area's power line network as an example, the available frequency band is set to 4MHz to 24MHz, the center frequency is 14MHz, and the total bandwidth is 20MHz. After acquiring these parameters, the ranging device probes the frequency response characteristics of the power line channel across the entire frequency band using a frequency sweep method.

[0040] The frequency sweep process employed a stepped sweep technique with a frequency step interval of 50kHz, generating 400 test points within the range of 4MHz to 24MHz. The ranging device transmitted a sinusoidal signal of constant amplitude at each test frequency, with the signal power controlled at -30dBm. The receiver measured the signal amplitude and phase response at each frequency. To eliminate the influence of random noise during the measurement process, each frequency point was measured 10 times repeatedly, and the average value was taken. The resulting frequency response dataset contains three parts: frequency point, amplitude response, and phase response, forming a complete frequency response curve. In a residential area testing environment, the measured frequency response curve exhibited obvious fluctuation characteristics, with multiple amplitude peaks and troughs.

[0041] Peak point marking is performed based on the constructed frequency response curve. A peak point is a local maximum on the frequency response curve where the amplitude is higher than that of adjacent frequencies. A sliding window method is used for peak point identification, with a window width of 500kHz, searching for the frequency with the largest amplitude within the window range. To avoid false peaks caused by noise interference, a peak threshold is set to 3dB higher than the average amplitude. When a detected local maximum exceeds this threshold, it is marked as a valid peak point. In a residential area test environment, eight valid peak points were identified in the 4MHz to 24MHz frequency band using the above method, located at 5.2MHz, 7.8MHz, 10.1MHz, 13.5MHz, 16.3MHz, 18.7MHz, 21.2MHz, and 23.4MHz.

[0042] The frequency difference between adjacent peak points is the subcarrier frequency spacing. Calculating the frequency difference between adjacent points for the eight identified peak points yields seven frequency spacing values: 2.6MHz, 2.3MHz, 3.4MHz, 2.8MHz, 2.4MHz, 2.5MHz, and 2.2MHz. These frequency spacing values ​​reflect the frequency selectivity characteristics of the power line channel in different frequency bands. Regions with larger frequency spacing typically indicate poor channel coherence and severe frequency selective fading in that region; conversely, regions with smaller frequency spacing indicate better channel coherence and a flatter frequency response.

[0043] Based on the calculated subcarrier frequency spacing, the entire frequency response curve is divided into multiple frequency bands. Each frequency band is bounded by adjacent peak points, and the width of the band is equal to the corresponding frequency spacing. In a residential area test environment, seven frequency bands were formed: 4MHz to 5.2MHz, 5.2MHz to 7.8MHz, 7.8MHz to 10.1MHz, 10.1MHz to 13.5MHz, 13.5MHz to 16.3MHz, 16.3MHz to 18.7MHz, 18.7MHz to 21.2MHz, and 21.2MHz to 24MHz. The average response amplitude was calculated for each frequency band by averaging the amplitude response of all test frequencies within the band. The calculated average response amplitudes for each frequency band were -42dB, -38dB, -45dB, -35dB, -39dB, -46dB, -41dB, and -47dB, respectively.

[0044] Based on the previously measured coherent bandwidth of the power line channel of 833kHz, frequency bands with frequency intervals greater than 833kHz were selected. In the residential area test environment, the frequency intervals of all seven frequency bands were greater than the coherent bandwidth, thus meeting the selection criteria. Larger frequency intervals mean that subcarrier signals will experience different channel fading characteristics within these intervals, which is beneficial for the transmission and reception of ranging signals.

[0045] Channel attenuation was measured within the selected frequency bands, and the two bands with the best channel conditions were selected for ranging. The channel attenuation was measured using an end-to-end transmission test method, transmitting a test signal and measuring the strength of the received signal within each frequency band. The test signal was a sinusoidal sweep signal covering the entire frequency band, with a transmitted power of -20dBm. The receiver recorded the signal strength at each frequency point and calculated the average attenuation value across the entire band. Measurement results showed that in a residential area test environment, the 10.1MHz to 13.5MHz and 13.5MHz to 16.3MHz frequency bands had the lowest channel attenuation, with average attenuation values ​​of -35dB and -39dB, respectively. These two frequency bands were selected as candidate bands for ranging subcarriers.

[0046] When determining the ranging subcarrier frequency, the center point of each candidate interval is selected as the subcarrier frequency. The center points of the two candidate intervals are 11.8MHz and 14.9MHz, respectively, and these two frequency points are set as the ranging subcarrier frequencies. Selecting the center point of the frequency band as the subcarrier frequency can minimize the instability characteristics that may exist at the frequency band edges and improve the transmission reliability of the ranging signal. The ranging subcarrier frequency spacing is 3.1MHz, which is much larger than the channel coherence bandwidth, ensuring that the two subcarriers experience different channel characteristics, which is beneficial to improving ranging accuracy.

[0047] The transmitted phase information is modulated onto selected ranging subcarriers to generate a ranging signal. The transmitted phase information uses known initial phase values: 0° on the 11.8MHz subcarrier and 90° on the 14.9MHz subcarrier. The modulation process employs quadrature amplitude modulation (QAM) to map the phase information onto the carrier phase. The modulated signals from the two subcarriers are combined into a single composite signal, with the signal power controlled at -25dBm to ensure compliance with power line communication radiation limits.

[0048] A cyclic prefix is ​​added to the modulated ranging subcarrier signal, followed by bandpass filtering. The cyclic prefix length is set to one-quarter of the effective signal length; that is, if the effective signal length is 80 μs, a 20 μs cyclic prefix is ​​added. Adding the cyclic prefix effectively mitigates inter-symbol interference caused by multipath propagation, improving the reliability of signal detection. A Butterworth filter is used for bandpass filtering, with a passband range of 11 MHz to 16 MHz, covering both ranging subcarrier frequencies with appropriate margin. The filter order is 6th, with passband ripple controlled below 1 dB and stopband attenuation greater than 40 dB. The filtered signal exhibits good spectral characteristics, reduces out-of-band radiation, and effectively suppresses power frequency interference and high-frequency noise.

[0049] This invention determines the subcarrier frequency spacing by bandwidth and center frequency, and selects appropriate ranging subcarrier frequencies, achieving high-precision distance measurement in complex and variable power line channel environments. The subcarrier selection method based on frequency response curve analysis can fully adapt to the frequency selectivity characteristics of power line channels, selecting the frequency band with optimal transmission conditions for ranging signal transmission. Employing a dual-carrier structure with a frequency spacing greater than the coherence bandwidth effectively utilizes the channel diversity provided by frequency-selective fading, enhancing the robustness of the ranging signal.

[0050] The source node transmits a ranging subcarrier signal via a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information, including: The channel transmission status in the power line is detected at the source node to obtain channel status parameters. The ranging subcarrier signal is compensated according to the channel state parameters to generate a compensated ranging signal. Power frequency suppression is applied to the compensated ranging signal to generate a power frequency suppressed ranging signal; The impedance characteristics are adjusted according to the channel state parameters, and the ranging signal after suppressing the power frequency is sent to the power line through the power line coupler; The target node acquires ranging subcarrier signals from the power line; The synchronization marker is identified from the acquired ranging subcarrier signal, the sampling position is determined based on the synchronization marker, the waveform data of the ranging subcarrier signal is obtained at the sampling position, and the reference signal is constructed using the waveform data. The phase difference is obtained by comparing the ranging subcarrier signal with the reference signal, and the phase compensation value introduced by the channel is calculated based on the channel state parameters. The phase difference is compensated for by the phase compensation value to obtain the received phase information.

[0051] Before transmitting the ranging subcarrier signal, the source node needs to detect the channel transmission status and obtain channel status parameters. Channel transmission status detection employs an active detection method, sending a probe signal to the power line and analyzing the echo signal. The probe signal uses a pseudo-random binary sequence with a bandwidth of 20MHz, a sequence length of 1023 bits, and a transmission power of -15dBm. The echo signal is amplified and then digitized using a 16-bit analog-to-digital converter at a sampling rate of 50MHz and a sampling time of 200μs. Time-frequency analysis is performed on the acquired echo signal to extract channel status parameters, including channel attenuation, phase characteristics, noise level, and impedance characteristics. Taking a residential power line network as an example, the measured channel attenuation is 32dB, the phase delay is 15μs, the noise level is -85dBm / Hz, and the line impedance is 75Ω±15Ω.

[0052] After obtaining the channel state parameters, the source node performs signal compensation on the ranging subcarrier signal. This signal compensation involves pre-compensation for channel attenuation and phase delay characteristics. Signal amplitude pre-compensation adjusts the transmitted signal amplitude based on the measured channel attenuation value. For a measured channel attenuation of 32dB, the signal amplitude is increased by 30dB at the transmitting end, retaining a 2dB margin to prevent signal overload. Phase pre-compensation adjusts the signal based on the channel phase delay characteristics. For a measured phase delay of 15μs, a 63.3° phase compensation is introduced on the 11.8MHz subcarrier, and an 80.1° phase compensation is introduced on the 14.9MHz subcarrier.

[0053] After the compensated ranging signal is generated, power frequency suppression processing is performed to eliminate 50 / 60Hz power frequency signal interference on the power line. Power frequency suppression is achieved using a digital notch filter with a center frequency of 50Hz and 60Hz, a bandwidth of 5Hz, and a stopband attenuation greater than 50dB. The filter adopts an 8th-order Butterworth structure to ensure that the impact on the ranging signal is minimized while suppressing power frequency interference. Harmonic components at 100Hz, 150Hz, and 200Hz are also suppressed to a depth of 40dB. After power frequency suppression processing, the signal-to-noise ratio is improved by approximately 12dB.

[0054] Based on the acquired channel state parameters, the source node adjusts the impedance characteristics of the power line coupler to achieve optimal matching between the ranging signal and the power line. Impedance adjustment is achieved through a network of variable capacitors and variable inductors. Based on the measured line impedance of 75Ω ± 15Ω, the coupler output impedance is adjusted to 75Ω. The impedance matching network includes a π-type matching circuit consisting of two variable capacitors and one variable inductor. The capacitor values ​​range from 10pF to 100pF, and the inductor values ​​range from 1μH to 10μH. Precise impedance adjustment is achieved through digital control. The impedance matching degree is evaluated by measuring the voltage standing wave ratio (VSWR), and the VSWR after matching is controlled within 1.5.

[0055] After impedance characteristic adjustment, the source node transmits the suppressed power frequency ranging signal to the power line via a power line coupler. The power line coupler uses a high-frequency transformer coupling method, with the transformer employing a ferrite core structure. Its operating frequency range is 1MHz to 30MHz, and its insertion loss is less than 1dB. The protection circuit includes a gas discharge tube and a varistor to prevent high-voltage spikes on the power line from damaging the ranging equipment. The signal transmission power is controlled at -10dBm to meet the electromagnetic compatibility requirements of power line communication.

[0056] The target node acquires the ranging subcarrier signal from the power line via a power line coupler. During acquisition, a high-pass filter removes power frequency and low-frequency interference. The high-pass filter has a cutoff frequency of 1MHz and a stopband attenuation greater than 60dB. The filtered signal is amplified by a low-noise amplifier with a gain of 20dB and a noise figure less than 3dB. The amplified signal is then passed through a bandpass filter to extract the ranging subcarrier signal. The bandpass filter has center frequencies of 11.8MHz and 14.9MHz and a bandwidth of 200kHz. The filtered signal is then sampled by a 16-bit analog-to-digital converter at a sampling rate of 50MHz and a sampling time of 200μs, forming the digital waveform data of the ranging subcarrier signal.

[0057] Synchronization markers are identified from the acquired ranging subcarrier signals to determine the precise sampling position. The synchronization markers are Barker code sequences with a length of 13 bits, exhibiting good autocorrelation properties. Synchronization marker detection employs a sliding correlation method, calculating the correlation value between the received signal and the locally stored standard Barker code sequence. When the correlation value exceeds a set threshold of 0.8, a synchronization marker is detected. The starting position of the ranging subcarrier signal is determined based on the detected synchronization marker position. Waveform data is then acquired starting 20 μs after this position, with an acquisition duration of 50 μs and a sampling point count of 2500 points.

[0058] The reference signal was constructed based on a standard sinusoidal signal generated by a local oscillator, with frequencies precisely set to 11.8MHz and 14.9MHz and an initial phase of 0°. The local oscillator employed a temperature-compensated crystal oscillator, achieving a frequency stability better than ±0.5ppm. The received ranging subcarrier signal was compared with the corresponding reference signal at each frequency, and the phase difference was extracted using quadrature demodulation. Quadrature demodulation multiplied the received signal with both the in-phase and quadrature reference signals, filtered out high-frequency components using a low-pass filter, and obtained the in-phase and quadrature components, from which the phase difference was calculated. The measured phase difference for the 11.8MHz subcarrier was 105.3°, and the measured phase difference for the 14.9MHz subcarrier was 168.7°.

[0059] The phase compensation value introduced by the channel is calculated based on the previously obtained channel state parameters. The phase compensation calculation takes into account the frequency selectivity and nonlinear phase response of the channel. For a measured channel phase delay of 15 μs, the phase delay introduced on the 11.8 MHz subcarrier is 63.3°, and the phase delay introduced on the 14.9 MHz subcarrier is 80.1°. Additional phase delays introduced by branch reflections on the power line, at 12.5° and 15.8° respectively, also need to be considered. The phase compensation value is the sum of these two phase delays, which are 75.8° and 95.9° respectively.

[0060] The measured phase difference is compensated for by the phase compensation value introduced by the channel to obtain the true received phase information. Compensating the 105.3° phase difference measured on the 11.8MHz subcarrier with a 75.8° phase compensation value yields a received phase of 29.5°; compensating the 168.7° phase difference measured on the 14.9MHz subcarrier with a 95.9° phase compensation value yields a received phase of 72.8°. The received phase information differs from the initial phase (0° and 90°) set during transmission. This difference reflects the phase change caused by the signal propagation distance and is the fundamental data for distance calculation.

[0061] This invention achieves high-precision distance measurement in complex power line network environments through techniques such as power line channel state detection, signal pre-compensation, power frequency suppression, impedance matching, synchronization marker identification, and phase extraction. This invention effectively overcomes challenges in power line communication such as power frequency interference, channel attenuation, impedance mismatch, and multipath propagation, providing reliable ranging performance. Signal compensation and impedance adjustment techniques based on channel state parameters significantly improve the transmission quality of the ranging signal and enhance the system's adaptability to channel variations. The dual-carrier ranging structure combined with phase comparison technology achieves sub-meter ranging accuracy, providing an effective means for equipment location, topology identification, and fault location in power line networks.

[0062] Based on the transmitted and received phase information, the channel transmission cycle number and phase difference of the ranging subcarrier are calculated respectively to obtain the initial distance values, including: The phase change is obtained by performing a difference operation on the transmitted and received phase information; The phase continuity is detected based on the phase change amount, the phase jump interval is determined, the phase continuous change interval is generated, and the phase cumulative value is calculated within the phase continuous change interval. The phase accumulation value is segmented according to the signal periodicity characteristics of the ranging subcarrier, and the number of channel transmission cycles is determined based on the segmentation results. The phase difference is obtained by matching the accumulated phase value with the number of channel transmission cycles. The initial distance value is calculated based on the frequency characteristics of the ranging subcarrier, combined with the number of channel transmission cycles and the phase difference.

[0063] The phase change is obtained by subtracting the transmitted and received phase information. This change directly reflects the degree of phase change of the ranging subcarrier signal during transmission. For example, for an 11.8MHz ranging subcarrier, the transmitted phase is set to 0 degrees, and the received phase is measured to be 29.5 degrees; for a 14.9MHz ranging subcarrier, the transmitted phase is set to 90 degrees, and the received phase is measured to be 72.8 degrees. The calculated phase change for the 11.8MHz subcarrier is 29.5 degrees, and for the 14.9MHz subcarrier, it is -17.2 degrees (72.8 - 90 = -17.2, a negative value indicates phase back-off).

[0064] In power line communication environments, phase information may abruptly change at certain points in time due to factors such as line impedance variations and interference signals, leading to discontinuities. Phase continuity detection employs a sliding window method, with a window length of 5 phase sampling points. A phase jump point is defined as a phase change where the phase difference between adjacent sampling points exceeds 30 degrees. In this example, the 11.8MHz subcarrier detected two phase jump points within the sampling time period, located at points 357 and 1258 of the sampling sequence; the 14.9MHz subcarrier detected one phase jump point, located at point 892. Based on the detection results, the 11.8MHz subcarrier forms three continuous phase change intervals: points 1-357, 358-1258, and 1259-2500; the 14.9MHz subcarrier forms two continuous phase change intervals: points 1-892 and 893-2500.

[0065] Calculating the cumulative phase value within a continuously changing phase range requires considering the periodicity of the phase. A phase unfolding technique is used to convert the folded phase value into a continuously increasing cumulative phase. During phase unfolding, when a sudden change in phase value from approximately 360 degrees to approximately 0 degrees is detected, it is determined that one cycle has been completed, and the cumulative phase value increases by 360 degrees. For an 11.8MHz subcarrier, the cumulative phase value is 357 degrees in the first interval, 3245 degrees in the second interval, and 4823 degrees in the third interval; for a 14.9MHz subcarrier, the cumulative phase value is 2875 degrees in the first interval and 5732 degrees in the second interval.

[0066] The phase accumulation value is segmented according to the signal periodicity characteristics of the ranging subcarrier. The number of channel transmission cycles is determined based on the segmentation results. The signal periodicity characteristics are determined by the frequency of the ranging subcarrier; the period is 84.75 ns for an 11.8 MHz subcarrier and 67.11 ns for a 14.9 MHz subcarrier. The total number of cycles can be calculated based on the relationship between the accumulated phase value and the phase angle (360 degrees) corresponding to a single cycle. For the 11.8 MHz subcarrier, the final accumulated phase value of 4823 degrees corresponds to 13.4 cycles; for the 14.9 MHz subcarrier, the final accumulated phase value of 5732 degrees corresponds to 15.9 cycles.

[0067] The phase difference is obtained by taking the remainder of the accumulated phase value and the angle (360 degrees) corresponding to the complete cycle. This angle represents the incomplete cycle portion. For an 11.8MHz subcarrier, 4823 degrees corresponds to 13 complete cycles, with a remaining phase difference of 144 degrees. For a 14.9MHz subcarrier, 5732 degrees corresponds to 15 complete cycles, with a remaining phase difference of 324 degrees. These phase differences reflect the phase changes that do not constitute a complete cycle during signal propagation and are key parameters for achieving high-precision distance measurement.

[0068] Electromagnetic waves travel at 0.6 to 0.8 times the speed of light in electric field lines; in this example, the speed is taken as 0.7 times the speed of light, or 2.1 × 10⁻⁶. 8m / s. For an 11.8MHz subcarrier, one cycle corresponds to a propagation distance of 17.8m, and 13.4 cycles correspond to 238.52m; the phase difference of 144 degrees accounts for 0.4 of one cycle, corresponding to 7.12 meters. Therefore, the initial distance calculated based on the 11.8MHz subcarrier is 238.52 + 7.12 = 245.64 meters. For a 14.9MHz subcarrier, one cycle corresponds to a propagation distance of 14.09m, and 15.9 cycles correspond to 224.03m; the phase difference of 324 degrees accounts for 0.9 of one cycle, corresponding to 12.68m. The initial distance calculated based on the 14.9MHz subcarrier is 224.03 + 12.68 = 236.71m.

[0069] The initial distance values ​​measured by subcarriers of different frequencies differ, requiring fusion processing to obtain a more accurate result. The differences mainly stem from frequency-selective attenuation and multipath effects of the channel; in this example, the ranging results of the two subcarriers differ by 8.93m. Distance fusion employs a weighted average method, assigning weights based on the anti-interference capability and stability of each subcarrier frequency: the 11.8MHz subcarrier has a weight of 0.45, and the 14.9MHz subcarrier has a weight of 0.55. The fused distance value is 0.45 × 245.64 + 0.55 × 236.71 = 240.81m.

[0070] In practical applications, the initial distance value also needs to be calibrated and compensated, taking into account the signal delay in the transmitting and receiving circuits. Analysis of the measurement results for known distances revealed that the distance corresponding to the system's inherent delay is 3.27m. Subtracting this value from the initial distance value yields a final distance measurement result of 237.54m. Compared to the actual physical distance of 237m, the measurement error is 0.54m, with a relative error of approximately 0.23%, meeting the accuracy requirements for power line ranging.

[0071] This invention achieves high-precision distance measurement in complex power line environments through meticulous processing of transmitted and received phase information. Employing techniques such as phase difference calculation, continuity detection, cumulative value calculation, period determination, and phase difference extraction, it effectively overcomes problems such as phase jumps and period folding, accurately reproducing the phase change characteristics of the ranging signal during transmission. The multi-carrier ranging structure provides frequency diversity gain, which not only improves the reliability of the measurement results but also reduces the random error of single-frequency point measurements through fusion algorithms.

[0072] Compare the differences between the initial distance values ​​corresponding to the two ranging subcarriers. If the difference meets a preset difference threshold, calculate the average of the two initial distance values ​​as the final distance. If the difference does not meet the preset difference threshold, trigger phase observation fusion to recalculate the final distance, including: Extract the initial distance values ​​corresponding to the two ranging subcarriers, calculate the fluctuation parameters of the initial distance values ​​to generate the distance difference, and normalize the distance difference to obtain the standardized difference value. The standardized difference value is compared with a preset difference threshold to generate a comparison result identifier; When the comparison result indicates that the standardized difference value meets the preset difference threshold, the signal amplitude and noise amplitude of the two ranging subcarriers are extracted, a weighting coefficient is generated based on the signal amplitude and noise amplitude, and the initial distance values ​​corresponding to the two ranging subcarriers are weighted and averaged using the weighting coefficient to obtain the final distance. When the comparison result indicates that the standardized difference value does not meet the preset difference threshold, the phase observation values ​​of the two ranging subcarriers are extracted, the amplitude features are extracted based on the phase observation values, and the observation weights are calculated. The phase observations are fused according to the observation weights to obtain a fused phase value, which is then converted into the final distance.

[0073] Initial distance values ​​for two ranging subcarriers were extracted from the measurement data. The initial distance measured for the 11.8MHz subcarrier was 245.64m, and the initial distance measured for the 14.9MHz subcarrier was 236.71m, with a difference of 8.93m. The fluctuation parameter of the initial distance values ​​was calculated to generate the distance difference. The fluctuation parameter reflects the stability of the distance measurement results. It was calculated by taking the standard deviation of 20 consecutive ranging measurements. The fluctuation parameter for the 11.8MHz subcarrier was 1.25m, and the fluctuation parameter for the 14.9MHz subcarrier was 0.87m. The distance difference was calculated by correlating the difference between the two initial distance values ​​with the fluctuation parameter, resulting in a distance difference of 9.02m.

[0074] The distance difference is normalized to obtain a standardized difference value. The normalization process considers ranging environmental factors and signal transmission characteristics. In power line ranging environments, line length has a significant impact on measurement accuracy; the longer the distance, the greater the measurement deviation. Therefore, a distance compensation factor is introduced during normalization. This factor is positively correlated with the measured distance. Specifically, the percentage correlation between the average of two initial distance values ​​is used as the compensation factor; in this example, the compensation factor is 2.41. The standardized difference value is obtained through the correlation calculation between the distance difference and the compensation factor; in this example, the standardized difference value is 3.74.

[0075] The standardized difference value is compared with a preset difference threshold to generate a comparison result identifier. The preset difference threshold is set according to the complexity of the power line network and the distance measurement accuracy requirements. For power line networks in general residential and office environments, the threshold is set to 5.0; for power line networks in industrial environments, the threshold can be appropriately relaxed to 8.0. This example uses the residential environment standard, with a preset difference threshold of 5.0. The comparison result identifier is a Boolean value; it is true when the standardized difference value is less than the preset difference threshold, and false otherwise. In this example, 3.74 is less than 5.0, so the comparison result identifier is true.

[0076] The comparison results indicate that when the standardized difference value meets the preset difference threshold, the signal amplitude and noise amplitude of the two ranging subcarriers are extracted, and weighting coefficients are generated based on the signal amplitude and noise amplitude. For the 11.8MHz subcarrier, the measured signal amplitude is -32.5dBm, the noise amplitude is -85.6dBm, and the signal-to-noise ratio (SNR) is 53.1dB; for the 14.9MHz subcarrier, the measured signal amplitude is -34.8dBm, the noise amplitude is -82.3dBm, and the SNR is 47.5dB. The weighting coefficient is proportional to the SNR, and the weight of each subcarrier is calculated using the relative value of the SNR. The weighting coefficient for the 11.8MHz subcarrier is 0.53, and the weighting coefficient for the 14.9MHz subcarrier is 0.47.

[0077] The initial distance values ​​corresponding to the two ranging subcarriers are weighted and averaged using weighting coefficients to obtain the final distance. The product of the initial distance value of the 11.8MHz subcarrier and its weighting coefficient is 130.19m; the product of the initial distance value of the 14.9MHz subcarrier and its weighting coefficient is 111.25m. The sum of the two is 241.44m, which is the final distance value after weighted averaging. Inherent delay compensation is then applied to this value. After deducting the distance corresponding to the inherent system delay of 3.27m, the final ranging result is 238.17m.

[0078] When the comparison results indicate that the standardized difference value does not meet the preset difference threshold, the initial distance values ​​measured by the two ranging subcarriers differ too much, requiring a more refined fusion method. Phase observations of the two ranging subcarriers are extracted, amplitude features are extracted based on these phase observations, and observation weights are calculated. Phase observations refer to the initial phase information obtained during ranging, including the cumulative phase value and phase difference. For the 11.8MHz subcarrier, the cumulative phase value is 4823 degrees, and the phase difference is 144 degrees; for the 14.9MHz subcarrier, the cumulative phase value is 5732 degrees, and the phase difference is 324 degrees.

[0079] Amplitude characteristics are obtained by analyzing the time-domain waveforms of phase observations. The analysis methods include multiple dimensions such as waveform smoothness, phase continuity, and signal strength. Waveform smoothness is calculated using the local variance of the phase values; the smaller the variance, the higher the smoothness. Phase continuity is obtained statistically from the phase differences between adjacent sampling points. Signal strength is directly obtained using the subcarrier signal amplitude. The waveform smoothness of the 11.8MHz subcarrier is 0.85, the phase continuity is 0.92, and the normalized signal strength is 0.78; the waveform smoothness of the 14.9MHz subcarrier is 0.79, the phase continuity is 0.85, and the normalized signal strength is 0.72.

[0080] The observation weights are calculated based on amplitude characteristics. These weights reflect the reliability of the measurement results for each subcarrier. The calculation process considers three factors: waveform smoothness, phase continuity, and signal strength, assigning different weights to each for comprehensive evaluation. The waveform smoothness weight is 0.4, the phase continuity weight is 0.4, and the signal strength weight is 0.2. For the 11.8MHz subcarrier, the observation weight is 0.856; for the 14.9MHz subcarrier, the observation weight is 0.806. After normalization, the normalized observation weight for the 11.8MHz subcarrier is 0.515, and the normalized observation weight for the 14.9MHz subcarrier is 0.485.

[0081] The phase observations are fused using observation weights to obtain a fused phase value. The fusion process is not simply a weighting of the phase values, but rather a weighting of the propagation delay corresponding to the phase measurements. For an 11.8MHz subcarrier, the propagation delay corresponding to the phase measurements is 1169.7ns; for a 14.9MHz subcarrier, the propagation delay is 1127.2ns. The weighted average propagation delay is calculated using normalized observation weights, resulting in a fused propagation delay of 1149.0ns.

[0082] Converting the propagation delay into the final distance, the propagation speed of electromagnetic waves in electric field lines is 2.1 × 10⁻⁶. 8The distance is calculated as 241.3 m, calculated by multiplying the propagation delay by the propagation speed (m / s). After compensating for inherent delay, subtracting the distance corresponding to the inherent system delay (3.27 m), the final distance measurement is 238.03 m. Compared to the actual physical distance of 23 m, the measurement error is 1.03 m, with a relative error of approximately 0.43%.

[0083] This invention effectively improves ranging accuracy and reliability by intelligently comparing and fusing distance values ​​measured from different subcarriers. Different fusion strategies are adaptively selected based on the degree of difference in ranging results, solving the problem of unstable ranging results in complex power line environments. The signal quality-based weighted averaging technique fully utilizes the advantages of high signal-to-noise ratio subcarriers, reducing the impact of measurement noise. When the measurement results differ significantly, deep fusion of phase observations effectively handles complex factors such as multipath propagation and frequency-selective attenuation.

[0084] In another alternative embodiment, such as Figure 2 The diagram shows the principle of the ranging system of the present invention. It constructs a multi-carrier ranging system based on OFDM, including a source node and a destination node. Both the source node S and the destination node P are equipped with power line couplers for injecting OFDM signals into the power line and extracting signals from the power line.

[0085] Initialize the OFDM signal parameters transmitted from the source node to the destination node and select two subcarriers as ranging subcarriers. Specifically, initialize the bandwidth of the OFDM signal transmitted from the source node to the destination node to be B, and the center frequency to be... The OFDM signal contains N subcarriers. In this embodiment, the bandwidth of the OFDM signal is set. MHz, center frequency MHz, the number of subcarriers contained in an OFDM signal is Based on the OFDM signal parameters sent from the source node to the destination node, two frequencies from N subcarriers are selected. Subcarrier as ranging subcarrier , The data transmitted is ; ; ; Where f1 is the frequency of the ranging subcarrier to the left of the center frequency, f c Where f is the center frequency, B is the bandwidth of the OFDM signal, N is the number of subcarriers contained in the OFDM signal, f2 is the frequency of the ranging subcarrier to the right of the center frequency, and [·] indicates rounding down.

[0086] △f is the frequency spacing of the ranging subcarriers. To improve ranging accuracy, it must meet the following requirements. When the frequency interval Δf between the two subcarriers is greater than the coherence bandwidth B of the power line channel c At that time, that is The two subcarriers experience significantly different channel characteristics, and their phase changes are independent. By comparing their information, the phase ambiguity caused by multipath effects can be eliminated more accurately, thus improving ranging accuracy. It is the maximum delay time of signal multipath propagation.

[0087] Ranging subcarrier The expression is: ; Where exp(·) represents the exponential function, express The transmitted data takes values ​​from the QPSK constellation. According to the definition of the Cramer-Rao lower bound, maximizing the frequency spacing between the two ranging subcarriers can improve ranging accuracy; therefore, in this embodiment, the frequencies of the two ranging subcarriers are... MHz, MHz.

[0088] Then, the distance is calculated by obtaining the number of cycles the ranging subcarrier passes through the channel and the phase difference. Let the receiving node P obtain the j-th ranging subcarrier sent by the transmitting end S. The ranging subcarrier after attenuation by the power line carrier channel is and according to and Calculate the number of cycles experienced by the ranging subcarrier during channel transmission. The set of period numbers corresponding to the ranging subcarrier is ,in It is an integer. The calculation formula is: ; Where j represents the index number of the ranging subcarrier, k represents the index number of all subcarriers in the OFDM signal, a(k) represents the position index of the k-th subcarrier, and p(k) represents the frequency value of the k-th subcarrier. This indicates rounding down to the nearest integer.

[0089] Read the data frame format file of the ranging subcarrier The phase information is used to obtain the phase information set of the ranging subcarrier. ,in, Indicates that S sends Phase information at time. In this embodiment, The data frame format file for the ranging subcarrier is shown in the figure below. Figure 3As shown: The data frame format file includes a 1-byte frame header, which is a check frame and can be used for synchronization and verification; a 4-byte timestamp, used to record the transmission and reception time (optional); 2 bytes of phase information, which contains the phase information when the signal is transmitted and received, used for multi-carrier ranging; and a 1-byte subcarrier ID, used to indicate which ranging subcarrier the signal belongs to.

[0090] Read the ranging subcarrier received by the destination node P Data frame format file The phase information is used to obtain the set of phase information of the ranging subcarrier after channel attenuation. .

[0091] calculate and Phase difference And based on the number of cycles and calculate The corresponding distance set between S and P ,in, express The corresponding distance between S and P, The calculation formula is: ; in, It is a frequency of ranging subcarrier The wavelength.

[0092] Determine whether the distance between two subcarriers meets the distance difference threshold. If it does, take the average value. Otherwise, determine that there is a phase ambiguity problem, trigger the phase observation fusion algorithm, and recalculate the distance.

[0093] Set the distance difference threshold to and judge If true, then calculate. , average First, obtain the distance from the source node S to the destination node P; otherwise, proceed to the next step. The calculation formula is: ; Calculate the destination node's reception of the data sent by S. The phase observations are used to obtain the phase observation set. and the phase observation values , Linear merging is performed to obtain phase observations. ,in, This indicates that P receives what S sends. Phase observations, This represents the phase observation value corresponding to S. The calculation formulas are as follows: ; ; ; ; in, express The true value of the geometric distance to P. express Phase noise, express Phase ambiguity, express Phase ambiguity, express The phase noise, x, y are linear combining coefficients, and the selection of the linear combining coefficients is related to the ranging subcarrier. frequency The formula for calculating the linear consolidation coefficient is as follows: ; Where t is any non-zero constant.

[0094] calculate The corresponding wavelength observation value is obtained. and according to and Calculate the distance from the source node to the destination node. ,in, This represents the wavelength observation value corresponding to S. This represents the distance between S and P. and The calculation formulas are as follows: ; .

[0095] This invention provides a broadband multi-carrier ranging system based on power line communication, the system comprising: The setup unit is used to construct a multi-carrier ranging system, which sets up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. The parameter configuration unit is used to set the bandwidth, center frequency, and number of subcarriers of the orthogonal frequency division multiplexing signal, and to determine the coherent bandwidth of the power line channel based on the multipath delay time of the power line channel. The subcarrier selection unit is used to calculate the subcarrier frequency interval based on the bandwidth and center frequency, select two subcarriers with a frequency interval greater than the coherent bandwidth of the power line channel as ranging subcarriers, and generate a ranging subcarrier signal containing transmission phase information. The signal transceiver unit is used to transmit a ranging subcarrier signal through the source node via a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information. The distance calculation unit is used to calculate the channel transmission cycle number and phase difference of the ranging subcarrier based on the transmitted phase information and the received phase information, respectively, to obtain the initial distance value; The distance fusion unit is used to compare the difference between the initial distance values ​​corresponding to two ranging subcarriers. When the difference meets the preset difference threshold, the average of the two initial distance values ​​is calculated as the final distance. When the difference does not meet the preset difference threshold, the phase observation value fusion is triggered to recalculate the final distance.

[0096] One technical solution provided in this embodiment of the invention is an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps in any of the aforementioned methods.

[0097] One technical solution provided in this embodiment of the invention is a computer-readable storage medium storing a computer program, wherein the processor executes the computer program to implement the steps in any of the aforementioned methods.

[0098] The specific embodiments described above are preferred embodiments of the present invention and are not intended to limit the specific scope of the present invention. The scope of the present invention includes, but is not limited to, these specific embodiments. All equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A broadband multi-carrier ranging method based on power line communication, characterized in that, Includes the following steps: A multi-carrier ranging system is constructed by setting up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. Set the bandwidth, center frequency, and number of subcarriers parameters of the orthogonal frequency division multiplexing signal, and determine the coherent bandwidth of the power line channel based on the multipath delay time of the power line channel; The subcarrier frequency interval is calculated based on the bandwidth and center frequency. Two subcarriers with a frequency interval greater than the coherent bandwidth of the power line channel are selected as ranging subcarriers to generate a ranging subcarrier signal containing the transmission phase information. The source node transmits a ranging subcarrier signal through a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information. Based on the transmitted and received phase information, the channel transmission cycle number and phase difference of the ranging subcarrier are calculated to obtain the initial distance value. The difference between the initial distance values ​​corresponding to the two ranging subcarriers is compared. When the difference meets the preset difference threshold, the average of the two initial distance values ​​is calculated as the final distance. When the difference does not meet the preset difference threshold, the phase observation values ​​are fused and the final distance is recalculated. Determining the coherent bandwidth of a power line channel based on its multipath delay time includes: The source node sends a pulse probe signal to the power line network through a power line coupler, and the destination node receives the pulse probe signal transmitted through the power line channel. The destination node identifies the first and last arriving pulses in the received pulse probe signal, calculates the time interval between the first and last arriving pulses, and determines the time interval as the power line channel multipath delay time. The reciprocal of the multipath delay time of the power line channel is determined as the coherent bandwidth of the power line channel; Compare the differences between the initial distance values ​​corresponding to the two ranging subcarriers. If the difference meets a preset difference threshold, calculate the average of the two initial distance values ​​as the final distance. If the difference does not meet the preset difference threshold, trigger phase observation fusion to recalculate the final distance, including: Extract the initial distance values ​​corresponding to the two ranging subcarriers, calculate the fluctuation parameters of the initial distance values ​​to generate the distance difference, and normalize the distance difference to obtain the standardized difference value. The standardized difference value is compared with a preset difference threshold to generate a comparison result identifier; When the comparison result indicates that the standardized difference value meets the preset difference threshold, the signal amplitude and noise amplitude of the two ranging subcarriers are extracted, a weighting coefficient is generated based on the signal amplitude and noise amplitude, and the initial distance values ​​corresponding to the two ranging subcarriers are weighted and averaged using the weighting coefficient to obtain the final distance. When the comparison result indicates that the standardized difference value does not meet the preset difference threshold, the phase observation values ​​of the two ranging subcarriers are extracted, the amplitude features are extracted based on the phase observation values, and the observation weights are calculated. The phase observations are fused according to the observation weights to obtain a fused phase value, which is then converted into the final distance.

2. The method according to claim 1, characterized in that, A multi-carrier ranging system is constructed by setting up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. In the power line network, the ranging area is determined, and the distribution information of the power supply circuits within the ranging area is obtained; Based on the power supply circuit distribution information, the first location point with an independent power supply circuit is selected as the source node; Based on the power supply circuit distribution information, a second location point that is in the same power supply circuit as the source node is selected and set as the destination node; Power line couplers are connected to the source node and the destination node respectively. The power line coupler includes a high-pass filter unit and an impedance matching unit. The source node and destination node are connected to the power line network via a power line coupler to complete the construction of a multi-carrier ranging system.

3. The method according to claim 1, characterized in that, The subcarrier frequency spacing is calculated based on bandwidth and center frequency. Two subcarriers with a frequency spacing greater than the coherence bandwidth of the power line channel are selected as ranging subcarriers. The ranging subcarrier signal containing the transmission phase information is generated as follows: Construct a frequency response curve based on bandwidth and center frequency, mark peak points on the frequency response curve, and calculate the subcarrier frequency spacing between adjacent peak points. The frequency response curve is divided into multiple frequency bands based on the subcarrier frequency spacing, and the response amplitude within each frequency band is calculated. Based on the response amplitude, frequency band intervals are selected to obtain frequency band intervals where the subcarrier frequency spacing is greater than the coherence bandwidth of the power line channel; The channel attenuation is measured within the selected frequency bands, and the two frequency bands with the smallest channel attenuation are selected. The center point of the two selected frequency bands is taken as the ranging subcarrier. The transmitted phase information is modulated onto the ranging subcarrier to generate a modulated ranging subcarrier signal; A cyclic prefix is ​​added to the modulated ranging subcarrier signal and bandpass filtered to obtain a ranging subcarrier signal containing the transmission phase information.

4. The method according to claim 1, characterized in that, The source node transmits a ranging subcarrier signal via a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information, including: The channel transmission status in the power line is detected at the source node to obtain channel status parameters. The ranging subcarrier signal is compensated according to the channel state parameters to generate a compensated ranging signal. Power frequency suppression is applied to the compensated ranging signal to generate a power frequency suppressed ranging signal; The impedance characteristics are adjusted according to the channel state parameters, and the ranging signal after suppressing the power frequency is sent to the power line through the power line coupler; The target node acquires ranging subcarrier signals from the power line; The synchronization marker is identified from the acquired ranging subcarrier signal, the sampling position is determined based on the synchronization marker, the waveform data of the ranging subcarrier signal is obtained at the sampling position, and the reference signal is constructed using the waveform data. The phase difference is obtained by comparing the ranging subcarrier signal with the reference signal, and the phase compensation value introduced by the channel is calculated based on the channel state parameters. The phase difference is compensated for by the phase compensation value to obtain the received phase information.

5. The method according to claim 1, characterized in that, Based on the transmitted and received phase information, the channel transmission cycle number and phase difference of the ranging subcarrier are calculated respectively to obtain the initial distance values, including: The phase change is obtained by performing a difference operation on the transmitted and received phase information; The phase continuity is detected based on the phase change amount, the phase jump interval is determined, the phase continuous change interval is generated, and the phase cumulative value is calculated within the phase continuous change interval. The phase accumulation value is segmented according to the signal periodicity characteristics of the ranging subcarrier, and the number of channel transmission cycles is determined based on the segmentation results. The phase difference is obtained by matching the accumulated phase value with the number of channel transmission cycles. The initial distance value is calculated based on the frequency characteristics of the ranging subcarrier, combined with the number of channel transmission cycles and the phase difference.

6. A broadband multi-carrier ranging system based on power line communication, used to implement the method described in any one of claims 1-5, characterized in that, The system includes: The setup unit is used to construct a multi-carrier ranging system, which sets up a source node for transmitting ranging signals and a destination node for receiving ranging signals in a power line network. Both the source node and the destination node are equipped with power line couplers. The parameter configuration unit is used to set the bandwidth, center frequency, and number of subcarriers of the orthogonal frequency division multiplexing signal, and to determine the coherent bandwidth of the power line channel based on the multipath delay time of the power line channel. The subcarrier selection unit is used to calculate the subcarrier frequency interval based on the bandwidth and center frequency, select two subcarriers with a frequency interval greater than the coherent bandwidth of the power line channel as ranging subcarriers, and generate a ranging subcarrier signal containing transmission phase information. The signal transceiver unit is used to transmit a ranging subcarrier signal through the source node via a power line coupler, and the destination node receives the ranging subcarrier signal and extracts the received phase information. The distance calculation unit is used to calculate the channel transmission cycle number and phase difference of the ranging subcarrier based on the transmitted phase information and the received phase information, respectively, to obtain the initial distance value; The distance fusion unit is used to compare the difference between the initial distance values ​​corresponding to two ranging subcarriers. When the difference meets the preset difference threshold, the average of the two initial distance values ​​is calculated as the final distance. When the difference does not meet the preset difference threshold, the phase observation value fusion is triggered to recalculate the final distance.

7. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the method as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer program instructions that, when executed by a processor, implement the steps of the method as described in any one of claims 1 to 5.

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