A communication method based on a power line communication system using OFDM

Abstract

The application relates to the technical field of communication, in particular to a communication method based on a power carrier communication system using OFDM (Orthogonal Frequency Division Multiplexing), which comprises the following steps: S1, an original data stream is modulated by OFDM at a transmitting end to generate an OFDM signal; S2, the OFDM signal is transmitted to a receiving end through a power line at the transmitting end; S3, an analog-to-digital conversion is performed on the received OFDM signal at the receiving end to obtain a digital baseband signal, and the sampling frequency of the analog-to-digital conversion is higher than that during the OFDM modulation; S4, a discrete Fourier transform is performed on the digital baseband signal at the receiving end to obtain frequency domain data symbols; and S5, demodulation and decoding are performed on the frequency domain data symbols at the receiving end to obtain a received data stream. The method modulates an original data stream by OFDM, thereby not only improving the frequency spectrum utilization rate but also enhancing the ability to resist multipath effects and ensuring efficient transmission in a complex power line environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, and in particular to a communication method based on an OFDM-based power line carrier communication system. BACKGROUND

[0002] Power line communication (PLC) is a communication technology that uses existing power line distribution networks as transmission media to realize the transmission of data, images, voice and other integrated services. PLC technology has the advantages of low wiring cost and wide coverage, and has therefore been widely concerned and applied in smart home, industrial automation and other fields. In particular, in scenarios where additional communication lines are not needed, PLC technology can effectively reduce construction costs and quickly realize the deployment of communication networks.

[0003] However, as a communication channel, the channel environment of the power line is very complex, and there are significant technical challenges. The power line network usually has high impedance mismatch characteristics and is greatly affected by external environmental factors, with strong noise interference. Typical sources of interference include power frequency signals, pulse interference generated by load switch actions, and random noise introduced by other electrical equipment. In addition, multipath effects also adversely affect signal transmission, causing reflection, refraction and diffraction of signals, resulting in severe delay spread and phase shift. These problems greatly reduce the transmission performance and reliability of power line carrier communication.

[0004] Orthogonal frequency division multiplexing (OFDM) is an efficient multicarrier modulation technology. By dividing a high-speed data stream into multiple lower-rate sub-data streams and using a set of orthogonal subcarriers for parallel transmission, OFDM technology can significantly improve the spectral efficiency and anti-interference capability of the system. In particular, when dealing with multipath effects and frequency-selective fading, OFDM technology exhibits superior performance. Therefore, introducing OFDM technology into the power line carrier communication system (OFDM-PLC) has become an important technical means, which can effectively improve the stability and reliability of data transmission.

[0005] In existing OFDM-PLC systems, the sampling frequency is usually designed based on the Nyquist sampling theorem. However, in a complex power line environment, the design of the Nyquist sampling frequency may not be sufficient to cope with high noise and signal attenuation problems in some cases. For example, in long-distance transmission or high-interference scenarios, signal attenuation is more severe, and traditional sampling methods can result in a decrease in the accuracy of signal recovery, thereby limiting the overall performance of the system. SUMMARY

[0006] In view of the above-mentioned defects and disadvantages of the prior art, the present application provides a communication method based on a power carrier communication system using OFDM, which solves the technical problem of insufficient anti-interference capability in the prior art.

[0007] In order to achieve the above-mentioned purpose, the main technical scheme adopted by the present application comprises:

[0008] The present application provides a communication method based on a power carrier communication system using OFDM, which comprises:

[0009] S1, the transmitting end performs OFDM modulation on the original data stream to generate an OFDM signal;

[0010] S2, the transmitting end sends the OFDM signal to the receiving end through a power line;

[0011] S3, the receiving end performs analog-to-digital conversion on the received OFDM signal to obtain a digital baseband signal, and the sampling frequency of the analog-to-digital conversion is higher than the sampling frequency during OFDM modulation;

[0012] S4, the receiving end performs discrete Fourier transform on the digital baseband signal to obtain a frequency domain data symbol;

[0013] S5, the receiving end demodulates and decodes the frequency domain data symbol to obtain a received data stream.

[0014] Preferably, the S1 specifically comprises:

[0015] S11, channel encoding and interleaving are performed on the original data stream to obtain a data symbol sequence to be modulated;

[0016] S12, the data symbol sequence is mapped to each subcarrier according to OFDM modulation parameters to form an initial frequency domain data symbol;

[0017] S13, inverse discrete Fourier transform is performed on the initial frequency domain data symbol to obtain a transmitting time domain OFDM symbol;

[0018] S14, a cyclic prefix is added before each transmitting time domain OFDM symbol to form an OFDM signal.

[0019] Preferably, the S13 specifically comprises:

[0020] S131, power allocation is performed on the initial frequency domain data symbol to adjust the transmitting power of the data symbol on each subcarrier;

[0021] S132, the initial frequency domain data symbol on each subcarrier is multiplied by a corresponding power allocation factor to obtain a power-adjusted frequency domain data symbol, so that the transmitting power of the data symbol on each subcarrier meets a preset power spectral density requirement.

[0022] S133, performing inverse discrete Fourier transform on the power-adjusted frequency-domain data symbol to obtain a transmit time-domain OFDM symbol.

[0023] Preferably, the method further comprises, after S3:

[0024] digitally filtering the digital baseband signal to filter out high-frequency interference in the digital baseband signal;

[0025] down-sampling the filtered digital baseband signal to reduce the sampling frequency to the sampling frequency in OFDM modulation;

[0026] removing the cyclic prefix from the down-sampled digital baseband signal to obtain a receive time-domain OFDM symbol.

[0027] Preferably, the method further comprises, after S4:

[0028] performing discrete Fourier transform on the real part and the imaginary part of the receive time-domain OFDM symbol to obtain the real part and the imaginary part of a frequency-domain data symbol;

[0029] obtaining the amplitude and the phase of the frequency-domain data symbol according to the real part and the imaginary part of the frequency-domain data symbol.

[0030] Preferably, S5 specifically comprises:

[0031] demodulating and decoding the frequency-domain data symbol based on the amplitude and the phase of the frequency-domain data symbol to obtain a receive data stream.

[0032] Preferably, the method further comprises, after S3:

[0033] performing symbol timing synchronization and carrier frequency synchronization on the received OFDM signal;

[0034] performing timing alignment and frequency correction on the receive time-domain OFDM symbol according to the synchronization result to compensate for symbol timing deviation and carrier frequency offset introduced by the channel.

[0035] Preferably, the method further comprises, after S5:

[0036] comparing the receive data stream obtained at the receiving end with the original data stream at the transmitting end to calculate a bit error rate;

[0037] feeding back the calculated bit error rate to the transmitting end, and adjusting the OFDM modulation parameters at the transmitting end according to the fed-back bit error rate.

[0038] Preferably,

[0039] The power line is a low-voltage power line, and the transmitting end and the receiving end are electrically connected with different phase lines of the low-voltage power line respectively to realize inter-phase communication.

[0040] Preferably, the S131 specifically comprises:

[0041] The initial frequency domain data symbol is power allocated, and the transmitting power of the data symbol on each sub-carrier is adjusted by formula (1);

[0042] The formula (1) is:

[0043]

[0044] P k represents the transmitting power of the kth sub-carrier;

[0045] h k represents the channel gain of the kth sub-carrier;

[0046] σ 2 represents the noise power;

[0047] α k is a channel estimation error correction factor;

[0048]

[0049]

[0050] μ k is a bandwidth requirement weight factor of the kth sub-carrier, and satisfies ∑ k μ k = 1.

[0051] The present application has the advantages that: the communication method of the power carrier communication system based on OFDM of the present application, since OFDM modulation is adopted, high-speed data flow is decomposed into multiple lower-speed data flow, and is transmitted in parallel through multiple orthogonal sub-carriers. The design of the orthogonal sub-carrier makes that there is no interference (ICI) between the sub-channels, and the influence of the multipath effect on the communication quality is reduced. Discrete Fourier transform (DFT) effectively suppresses the influence of frequency selective fading through frequency domain signal processing. This way can effectively deal with the multipath effect and frequency selective fading commonly seen in power line communication, thereby enhancing the anti-interference ability of the system.

[0052] The communication method of the power carrier communication system based on OFDM in the application can ensure sampling precision by using a sampling frequency of analog-digital conversion (ADC) higher than that of OFDM modulation, and can make the system effectively estimate channel characteristics by combining discrete Fourier transform (DFT) for frequency domain processing of signals, and then optimize the recovery process of received signals. The analog-digital conversion step with higher sampling frequency and the signal decoding method based on frequency domain processing can make the system more accurately capture signal characteristics and adapt to complex power line channel environment.

[0053] The communication method of the power carrier communication system based on OFDM in the application can maximize channel capacity and improve frequency spectrum utilization by using OFDM modulation technology to transmit data in parallel through multiple subcarriers. The parallel transmission characteristics of OFDM can effectively improve data rate, and the discrete Fourier transform can further optimize the spectral orthogonality between subcarriers. The application of OFDM technology effectively solves the problem of low frequency spectrum utilization of power carrier communication, and meets the demand of large data transmission.

[0054] The communication method of the power carrier communication system based on OFDM in the application can use existing power line network as transmission medium without rewiring. OFDM signals are directly transmitted to power lines without additional transmission equipment, and the system performance is improved by realizing frequency domain demodulation and decoding at the receiving end. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 The flow chart of the communication method of the power carrier communication system based on OFDM in the application is shown in the embodiment one.

[0056] Figure 2 The flow chart of the communication method of the power carrier communication system based on OFDM in the application is shown in the embodiment one. DETAILED DESCRIPTION

[0057] In order to better explain the application and facilitate understanding, the application will be described in detail below with specific embodiments in combination with the drawings.

[0058] In order to better understand the above technical solutions, the exemplary embodiments of the application will be described in more detail below with reference to the drawings. Although the exemplary embodiments of the application are shown in the drawings, it should be understood that the application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer, more thorough understanding of the application and to fully convey the scope of the application to those skilled in the art.

[0059] Embodiment one

[0060] Referring toFigure 1 The embodiment provides a communication method based on a power carrier communication system using OFDM, and the method comprises the following steps:

[0061] S1, an original data stream is modulated by a transmitting end to generate an OFDM signal; in the embodiment, data can be transmitted on multiple subcarriers in parallel by using OFDM modulation technology, which not only improves spectral efficiency but also enhances the ability to resist multipath effects and frequency selective fading, thereby improving communication quality.

[0062] S2, the transmitting end sends the OFDM signal to a receiving end through a power line; specifically, the existing power line is used as a communication medium, and no special communication line needs to be laid additionally, so that infrastructure cost is reduced, and simultaneous transmission of electric energy and information can be realized, which is very suitable for smart home, smart grid and other application scenarios.

[0063] S3, the receiving end performs analog-to-digital conversion on the received OFDM signal to obtain a digital baseband signal, and the sampling frequency of the analog-to-digital conversion is higher than that in OFDM modulation; in the embodiment, higher sampling frequency is used for analog-to-digital conversion to obtain more accurate signal representation, which helps to improve the accuracy of subsequent processing. In addition, oversampling (i.e., sampling frequency is higher than Nyquist frequency) can reduce aliasing, making signal recovery more reliable.

[0064] S4, the receiving end performs discrete Fourier transform on the digital baseband signal to obtain frequency domain data symbols; in the embodiment, the discrete Fourier transform can convert the OFDM signal in the time domain into a frequency domain representation, so that the data symbols on each subcarrier are separated, which is convenient for demodulation. Since the OFDM signal itself is constructed based on multiple orthogonal subcarriers, the discrete Fourier transform operation matches this characteristic, thereby simplifying the demodulation process.

[0065] S5, the receiving end demodulates and decodes the frequency domain data symbols to obtain a received data stream. Specifically, demodulating the data symbols in the frequency domain can effectively extract the information bits carried by each subcarrier, and decoding is responsible for restoring the original data stream. This step ensures that the data received from the physical layer can be correctly parsed into the information required by the user, and the function of the entire communication link is completed.

[0066] In the actual application process of the embodiment, the S1 specifically comprises:

[0067] S11, channel coding and interleaving are performed on the original data stream to obtain a data symbol sequence to be modulated; in this embodiment, channel coding (such as convolutional code, Turbo code or LDPC code) can increase redundant information, so that the receiving end can detect and correct errors that can be generated in the transmission process. The interleaving technology disperses the impact of burst errors by disordering the data sequence, that is, even if continuous bit errors occur, after deinterleaving, only a small number of bits will be affected, thereby simplifying the error correction process. Assuming that a data packet is transmitted in a noisy environment and a burst interference is encountered, causing a continuous data damage. Without interleaving, this part of data can not be recovered; but with interleaving, these errors will be dispersed to different positions and are easier to be corrected during decoding.

[0068] S12, the data symbol sequence is mapped to each subcarrier according to OFDM modulation parameters to form initial frequency domain data symbols; by mapping data to a plurality of orthogonal subcarriers, OFDM can effectively utilize spectrum resources and resist frequency selective fading. The data symbols on each subcarrier can be independently affected by multipath effects, reducing inter-symbol interference (ISI) and improving frequency band utilization and transmission efficiency.

[0069] S13, inverse discrete Fourier transform is performed on the initial frequency domain data symbols to obtain a transmission time domain OFDM symbol; the inverse discrete Fourier transform operation converts the data in the frequency domain back to the time domain to facilitate transmission in the actual physical channel. This process maintains the orthogonality between the subcarriers, ensuring the good characteristics of the OFDM signal, so that the receiving end can separate the information of each subcarrier through simple DFT.

[0070] S14, a cyclic prefix is added in front of each transmission time domain OFDM symbol to form an OFDM signal. The cyclic prefix (CP) is a key mechanism in the OFDM system for resisting inter-symbol interference caused by multipath propagation. It is actually a copy of the tail of the OFDM symbol, and when this copy appears at the beginning of the symbol, even if there is a multipath delay, as long as the delay does not exceed the length of the cyclic prefix, it will not cause inter-symbol interference. For example, in a complex wireless or power line environment, the time of signal arriving at the receiving end will be different, causing multipath effect. For example, if the maximum multipath delay is 1 microsecond, setting a cyclic prefix with a length greater than 1 microsecond can ensure that even the delayed signal can be correctly aligned with the current symbol without affecting the adjacent symbol, thereby avoiding inter-symbol interference ISI.

[0071] Specifically, the S13 specifically includes:

[0072] S131, power allocation is performed on the initial frequency domain data symbols to adjust the transmit power of the data symbols on each subcarrier; in this embodiment, different subcarriers can experience different channel conditions (such as fading, noise, etc.), and thus power allocation on the data symbols on each subcarrier can ensure that the signal on each subcarrier can be reliably demodulated at the receiving end. Reasonable power allocation can help improve the overall performance of the system, such as increasing the transmission distance, improving the bit error rate (BER), or achieving more efficient spectrum usage. For example, in an environment with frequency-selective fading, some subcarriers can be subject to greater attenuation. If no power adjustment is made, the information on these subcarriers can be lost or severely damaged. By allocating more transmit power to subcarriers that are more affected, it can be ensured that good communication quality can be maintained even under adverse conditions.

[0073] S132, the initial frequency domain data symbols on each subcarrier are multiplied by the corresponding power allocation factor to obtain the power-adjusted frequency domain data symbols, so that the transmit power of the data symbols on each subcarrier meets the preset power spectral density requirement;

[0074] In this embodiment, this process ensures that the power spectral density of the entire signal meets the standards set by regulatory agencies and the requirements of communication protocols, avoiding interference with other systems. In addition, it also allows dynamic adjustment of power according to the actual channel conditions, thereby maximizing the transmission efficiency of itself without affecting adjacent channels.

[0075] Assuming that the maximum allowed power spectral density within a specific frequency band is specified, by calculating and applying appropriate power allocation factors, it can be ensured that the OFDM signal does not exceed this limit, while optimizing the power usage of each subcarrier to adapt to the current channel conditions. For example, in a crowded spectrum environment, appropriately reducing the power of some subcarriers can reduce the impact on other users, while increasing the power of other subcarriers can improve the communication performance of itself without violating the regulations.

[0076] S133, performing inverse discrete Fourier transform on the power-adjusted frequency domain data symbol to obtain a time domain OFDM symbol. The power-adjusted frequency domain data symbol is converted into a time domain signal through IDFT, which maintains the orthogonality of the OFDM signal, allowing the receiving end to separate the information of each subcarrier through simple DFT. More importantly, since the power adjustment has been completed, the time domain OFDM symbol generated at this time can be directly used for physical channel transmission without additional processing. Continuing the above example, after completing the power adjustment, a new set of frequency domain data symbols is obtained, which now takes into account not only the channel conditions but also the power spectral density regulations. Next, the IDFT operation converts these adjusted frequency domain data into a time domain OFDM symbol suitable for transmission over the power line. Since all necessary adjustments have been completed, this time domain signal can be directly transmitted, and the receiving end only needs to follow the conventional OFDM receiving process.

[0077] Specifically, the method further comprises, after S3: digitally filtering the digital baseband signal to filter out high-frequency interference in the digital baseband signal; The power line environment usually contains various noise sources, such as switching power supply, impulse noise generated by electrical equipment, etc. These noises may appear in a higher frequency range. By using a low-pass filter, these high-frequency components can be effectively removed, reducing the impact on the useful signal. The filtering process helps to improve the ratio of the signal to the background noise, making the subsequent demodulation more accurate and reliable.

[0078] Downsampling the filtered digital baseband signal to reduce the sampling frequency to the sampling frequency during OFDM modulation; Specifically, the digital baseband signal after digital filtering is downsampled to reduce its sampling frequency to the same level as during OFDM modulation. Since the receiving end initially uses a higher sampling frequency than the transmitting end to ensure signal quality, it can now be restored to the original sampling rate through downsampling, reducing unnecessary computational load and storage requirements. Ensuring that the data format processed by the receiving end is consistent with the transmitting end facilitates subsequent processing steps such as cyclic prefix removal and discrete Fourier transform (DFT), improving processing efficiency.

[0079] The down-sampled digital baseband signal is subjected to cyclic prefix removal to obtain a received time-domain OFDM symbol. In this embodiment, the cyclic prefix (CP) added by the transmitting end is removed from the down-sampled digital baseband signal. The main role of the cyclic prefix is to prevent inter-symbol interference (ISI) in the presence of multipath propagation. Once the signal reaches the receiving end and is subjected to appropriate processing, the cyclic prefix has fulfilled its mission, and removing it can obtain a pure OFDM symbol, preparing conditions for the subsequent DFT. Removing the cyclic prefix also helps to simplify the process of time synchronization, because this step can help to determine the exact boundaries of each OFDM symbol, which is very important for accurately performing DFT.

[0080] In this embodiment, the method further comprises, after S4: performing discrete Fourier transform (DFT) on the real part and the imaginary part of the received time-domain OFDM symbol respectively to obtain the real part and the imaginary part of a frequency-domain data symbol. In this embodiment, performing DFT on the real part and the imaginary part respectively can more accurately recover the original frequency-domain data symbol. This method ensures that even in the presence of noise or interference, the information on each subcarrier can be accurately extracted. By independently processing the real part and the imaginary part, subtle changes in the signal can be better captured, thereby improving the accuracy of demodulation, especially in a low signal-to-noise ratio environment.

[0081] According to the real part and the imaginary part of the frequency-domain data symbol, the amplitude and the phase of the frequency-domain data symbol are obtained.

[0082] OFDM signals usually use amplitude and phase to carry information. Therefore, by obtaining the amplitude and the phase of the frequency-domain data symbol, the original data symbol can be directly mapped back, completing the demodulation process. In a complex power line environment, multipath effects can cause signal distortion. By accurately obtaining amplitude and phase information, techniques such as equalization can be used to compensate for these distortions, further improving reception performance.

[0083] In this embodiment, by performing DFT on the real part and the imaginary part respectively and then obtaining the amplitude and the phase, the entire demodulation process becomes more robust. Even in the face of complex transmission environments, such as noise and multipath effects in power lines, a high demodulation success rate can be maintained. This processing method helps to maximize the quality of the original signal, reduce the bit error rate (BER), and thus improve the performance of the overall communication system. Obtaining accurate amplitude and phase information enables the application of more advanced error correction coding techniques, such as soft decoding, which can significantly improve the system's error correction capability.

[0084] In this embodiment, S5 specifically comprises:

[0085] Based on the amplitude and phase of the frequency domain data symbols, the frequency domain data symbols are demodulated and decoded to obtain a received data stream. In this embodiment, demodulation is the conversion of amplitude and phase information in the frequency domain data symbols back to the original data bit stream. Decoding is the channel decoding of the demodulated data to recover the original transmitted information. By obtaining the amplitude and phase information of the frequency domain data symbols, the original data symbols can be more accurately mapped back. This step ensures that even in the presence of noise or interference, the original data can be restored as accurately as possible. This method not only improves the accuracy and reliability of data demodulation, but also enhances the system's ability to resist multipath effects and other interference. In addition, it supports efficient decoding algorithms, further improving communication quality and efficiency. This method is particularly suitable for applications that require high reliability and high-quality communication, such as smart grid, smart home, and other power line carrier communication fields, ensuring stable data transmission even in complex power line environments.

[0086] In a specific embodiment, the method further comprises, after S3: performing symbol timing synchronization and carrier frequency synchronization on the received OFDM signal; and performing timing alignment and frequency correction on the received time domain OFDM symbols according to the synchronization results, to compensate for symbol timing deviation and carrier frequency offset introduced by the channel. In this embodiment, the receiver estimates the symbol boundary by detecting specific pilot signals or training sequences to achieve symbol timing synchronization. With accurate symbol timing synchronization, interference between adjacent symbols can be avoided, improving demodulation accuracy. Carrier frequency offset will destroy the orthogonality between subcarriers, causing inter-carrier interference (ICI). Frequency synchronization can restore this orthogonality, ensuring that data on each subcarrier can be independently demodulated. Correct carrier frequency synchronization helps to more accurately recover the original signal, thereby reducing the bit error rate (BER) and improving overall communication quality. The above synchronization and correction measures work together to improve the demodulation capability of the receiver and the robustness of the system, allowing high-quality communication to be maintained even in poor channel conditions.

[0087] In this embodiment, the method further comprises, after S5:

[0088] The received data stream obtained by the receiving end is compared with the original data stream of the transmitting end to calculate the bit error rate; the calculated bit error rate is fed back to the transmitting end, and the transmitting end adjusts the OFDM modulation parameters according to the fed-back bit error rate. In the embodiment, the bit error rate (BER) in the transmission process is calculated by comparing the received data stream with the original data stream, and the result is fed back to the transmitting end. The transmitting end can flexibly adjust the OFDM modulation parameters, such as the modulation order and the coding rate, according to the received bit error rate information, so as to optimize the communication performance. The transmitting end adjusts the OFDM modulation parameters according to the fed-back bit error rate to adapt to the change of the channel condition. When the bit error rate is high, the transmitting end can enhance the anti-interference capability by reducing the modulation order or increasing the redundant coding, so as to reduce the bit error rate and ensure the reliability of data transmission. When the channel condition is good, the transmitting end can appropriately increase the modulation order or reduce the redundant coding to improve the spectral efficiency and the transmission rate. This method realizes the adaptability of the system and can automatically cope with the change of the channel to maintain the best communication performance.

[0089] In the practical application of the embodiment, the power line is a low-voltage power line, and the transmitting end and the receiving end are electrically connected to different phase lines of the low-voltage power line to realize inter-phase communication. In the embodiment, through inter-phase communication, the limitation of a single phase line can be crossed to realize wider network coverage. Communication between different phase lines enables signals to be transmitted in a larger range, increasing the coverage area and accessibility of the communication network. There can be a large number of electromagnetic interference sources in the power line environment, and these interferences are usually concentrated on a certain phase line. Through inter-phase communication, even if a certain phase line is severely interfered, other phase lines can still maintain normal communication. By transmitting data on different phase lines, communication load can be more evenly distributed to avoid overload of a certain phase line. The frequency response characteristics of different phase lines are different, and inter-phase communication can comprehensively utilize these characteristics to improve the overall communication performance.

[0090] In the embodiment, the S131 specifically includes: performing power allocation on the initial frequency domain data symbol, and adjusting the transmission power of the data symbol on each subcarrier by using formula (1);

[0091] The formula (1) is:

[0092]

[0093] P k denotes the transmission power of the kth subcarrier; h k denotes the channel gain of the kth subcarrier; σ 2 denotes the noise power; α kare correction factors for channel estimation errors; these parameters ensure that the transmission power is appropriately increased in the case of large noise and channel estimation errors. By taking noise and channel estimation errors into account, the bit error rate can be reduced and the data quality at the receiving end can be improved. Even in poor channel conditions, the communication quality can be maintained by adjusting the transmission power.

[0094] In this embodiment, β k is a parameter calculated according to SINR k , which reflects the bandwidth demand weight factor of each subcarrier. By dynamically adjusting the power, the bandwidth resources of each subcarrier can be fully utilized, and resource waste can be avoided. By dynamically adjusting the power, the bandwidth resources of each subcarrier can be fully utilized, and resource waste can be avoided. μ k is the bandwidth demand weight factor of the kth subcarrier, and satisfies ∑ k μ k = 1. In this embodiment, by adjusting the transmission power of each subcarrier, the best signal-to-noise ratio is ensured in a noisy and interfered environment, and max(0, ·) in formula (1) ensures that the transmission power is not negative and limits the upper limit of the power. By limiting the lower limit of the power to 0, unnecessary power consumption is avoided. By limiting the upper limit of the power, the device is prevented from being overloaded due to excessive power consumption.

[0095] In this embodiment, the transmitting end dynamically allocates power through formula (1), so that the total transmission power ∑ k P k of all subcarriers satisfies the power limit P max , and the power allocation strategy is optimized to maximize the total capacity of the system.

[0096] Embodiment Two

[0097] The embodiment provides a communication method based on an OFDM-based power line carrier communication system, and solves the technical problem that the prior art is insufficient in signal processing to completely overcome the instability and interference of power lines, thereby achieving the technical effects of improving signal transmission efficiency and transmission quality.

[0098] In this embodiment, a communication method based on an OFDM-based power line carrier communication system is provided, as shown in Figure 2 , the method comprises the following steps.

[0099] Step 100: The transmitting end performs OFDM modulation on the original data stream to generate an OFDM signal.

[0100] Specifically, the transmitting end is a device or apparatus responsible for sending data, such as various monitoring and control devices in industrial environments, distributed power generation units in smart grids, and smart home devices such as smart switches and security cameras. The transmitting end first receives the original data stream, which is the raw data signal without processing. These data can be any information that needs to be transmitted, such as text, images, or videos. Next, the transmitting end modulates these data using OFDM technology. Specifically, the transmitting end segments the original data stream and assigns each segment of data to multiple subcarriers for transmission. Each subcarrier is orthogonal in the frequency domain, meaning they do not interfere with each other, effectively utilizing the frequency spectrum and improving data transmission efficiency. The transmitting end uses inverse discrete Fourier transform (IDFT) to convert these subcarriers into a comprehensive signal, i.e., the OFDM signal. The OFDM signal is the signal after OFDM modulation, containing multiple parallel transmitted subcarriers, which can be transmitted to the receiving end through the power line later.

[0101] Step 100 converts the original data stream into an OFDM signal containing multiple subcarriers through OFDM modulation, ensuring efficient and reliable data transmission. Further, the embodiment of the present application step 100 specifically includes:

[0102] Step 101: Channel coding and interleaving the original data stream to obtain the data symbol sequence to be modulated.

[0103] Step 102: Map the data symbol sequence to each subcarrier according to the OFDM modulation parameters to form the initial frequency domain data symbol.

[0104] Step 103: Perform inverse discrete Fourier transform on the initial frequency domain data symbol to obtain the transmitting time domain OFDM symbol.

[0105] Step 104: Add a cyclic prefix before each transmitting time domain OFDM symbol to form an OFDM signal.

[0106] In particular, channel coding refers to encoding the original data to increase redundancy for error detection and correction during transmission. Interleaving refers to rearranging the coded data to spread it out during transmission to improve resistance to burst errors. First, the original data stream is channel coded using methods such as convolutional coding or Turbo coding to increase the redundancy information so that the receiving end can detect and correct errors that may occur during transmission. Next, the coded data is interleaved using block interleaving or random interleaving methods to rearrange it so that adjacent data symbols are spread out, thus making it more resistant to burst interference during transmission. The original data stream is channel coded and interleaved to obtain a data symbol sequence to be modulated, which refers to the representation of the coded and interleaved data. OFDM modulation parameters are related parameters for OFDM modulation, including the number of subcarriers, subcarrier spacing, etc. The obtained data symbol sequence is mapped to each subcarrier according to the OFDM modulation parameters. A subcarrier is an independent frequency channel in OFDM, and each subcarrier carries part of the data. Each data symbol is assigned to a specific subcarrier position to form an initial frequency domain data symbol. The initial frequency domain data symbol refers to the frequency domain representation formed after mapping the data symbol to the subcarrier. For example, in a system using 64 subcarriers, each data symbol is mapped to one of the 64 frequency domain positions. Inverse discrete Fourier transform (IDFT) is the process of converting frequency domain data into time domain signals. The initial frequency domain data symbol is subjected to inverse discrete Fourier transform (IDFT) to convert it from the frequency domain to the time domain to form a transmit time domain OFDM symbol. The transmit time domain OFDM symbol refers to the time domain signal after IDFT conversion. This process can be achieved through the inverse process of the fast Fourier transform (FFT) algorithm. For example, in a 64-subcarrier system, IDFT converts 64 frequency domain symbols into 64 time domain symbols. A cyclic prefix is added before each transmit time domain OFDM symbol. The cyclic prefix is a copy of the symbol tail pasted to the beginning of the symbol, which helps to combat multipath interference and ensure correct synchronization at the receiving end. For example, if the OFDM symbol length is 64 and the cyclic prefix length is 16, the first 16 samples of the symbol will be the same as the last 16 samples of the symbol.

[0107] Further, the step 103 of the embodiment of the present application comprises:

[0108] Step 103-1: Power allocation is performed on the initial frequency domain data symbol, and the transmission power of the data symbol on each subcarrier is adjusted. Specifically, the power allocation adjusts the transmission power on each subcarrier according to the preset requirements to optimize the signal transmission effect. The system allocates appropriate transmission power through the power allocation method according to the transmission conditions of each subcarrier, such as noise level and channel attenuation, to ensure that the signal strength of each subcarrier is optimal. For example, a water level algorithm can be used to set the total power limit and the channel gain of each subcarrier, initialize the power allocation factor of all subcarriers, and adjust the power allocation factor to optimally allocate the total power under the premise of meeting the power spectral density requirement.

[0109] Step 103-2: The initial frequency domain data symbol on each subcarrier is multiplied by the corresponding power allocation factor to obtain the power-adjusted frequency domain data symbol, so that the transmission power of the data symbol on each subcarrier meets the preset power spectral density requirement. The transmitting end predefines a power spectral density according to the actual signal transmission requirements. The power spectral density refers to the power distribution per unit frequency, which affects the transmission efficiency and anti-interference ability of the signal. The initial frequency domain data symbol on each subcarrier is multiplied by the corresponding power allocation factor to weight each subcarrier and adjust the transmission power of each subcarrier, so that it meets the system's preset power spectral density requirement and ensures that the signal power of all subcarriers reaches the optimal balance under different transmission conditions. The power allocation factor is a coefficient used to adjust the transmission power of the data symbol on each subcarrier.

[0110] Step 103-3: Inverse discrete Fourier transform is performed on the power-adjusted frequency domain data symbol to obtain the power-adjusted transmission time domain OFDM symbol. The power-adjusted frequency domain data symbol is subjected to inverse discrete Fourier transform (IDFT) again to generate the power-adjusted transmission time domain OFDM symbol.

[0111] Step 100 in this embodiment converts the original data stream into a power-optimized OFDM signal through a series of channel encoding, interleaving, subcarrier mapping, inverse discrete Fourier transform, power allocation and adjustment sub-steps, combined with complex signal processing and optimization algorithms, to ensure that the data can be efficiently and reliably transmitted over the power line.

[0112] Step 200: The transmitting end sends the OFDM signal to the receiving end through the power line.

[0113] Specifically, the receiving end is a device or apparatus responsible for receiving data. The transmitting end amplifies the OFDM signal generated in step 100 to ensure that the signal strength is sufficient for transmission over the power line. The amplified signal is filtered to remove unnecessary frequency components and prevent interference with other devices. The OFDM signal is coupled to the power line using a coupling device. The coupling device includes a coupling capacitor or transformer, etc., which can effectively superimpose high-frequency communication signals on low-frequency power signals. The OFDM signal is transmitted to the receiving end using the power line as the transmission medium. The power line has its own characteristics as a communication medium, including frequency-selective fading, multipath effects, and noise interference.

[0114] Preferably, the power line is a low-voltage power line, and the transmitting end and the receiving end are respectively electrically connected to different phase lines of the low-voltage power line to realize inter-phase communication.

[0115] Specifically, the low-voltage power line refers to a low-voltage power line used for power supply in residential, commercial, or industrial premises. These lines typically carry lower voltage power, such as 120V or 240V, in the power system. The phase lines in the power system are usually divided into three phases, and there is a phase difference between these phase lines, usually 120 degrees. Inter-phase communication refers to a communication method that utilizes the voltage difference between different phase lines. In a low-voltage power line, signal transmission signals may be affected by various noise interference and multipath effects, such as appliance switching noise, background noise, and interference from other electronic devices. Since the interference between different phase lines is usually small, the transmitting end and the receiving end are respectively connected to different phase lines, and communication is carried out using the voltage difference between the phase lines. This inter-phase communication can reduce noise interference on the same phase line and improve the reliability and anti-interference ability of signal transmission.

[0116] Step 300: The receiving end performs analog-to-digital conversion on the received OFDM signal to obtain a digital baseband signal, and the sampling frequency of the analog-to-digital conversion is higher than the sampling frequency during OFDM modulation.

[0117] Specifically, analog-to-digital conversion refers to the process of converting received analog signals into digital signals. The receiving end receives the OFDM signal from the power line through a coupling device. The signal is amplified and filtered to remove noise and interference introduced during power line transmission. Then, the receiving end uses an analog-to-digital converter to convert the received analog OFDM signal into a digital signal, obtaining a digital baseband signal. Among them, the sampling frequency of analog-to-digital conversion must be higher than the sampling frequency during OFDM modulation to ensure that the signal can be accurately captured and reconstructed. Sampling at a higher sampling frequency than the modulation sampling frequency can provide higher resolution and better anti-interference capability. For example, if the OFDM modulation sampling frequency is 1MHz, the analog-to-digital conversion sampling frequency can be set to 2MHz or higher. The sampling frequency refers to the number of times the signal is sampled per second. The OFDM modulation sampling frequency is the sampling frequency used by the transmitting end during OFDM modulation. Further processing of the obtained digital baseband signal includes channel equalization, error correction, and demodulation steps. The digital baseband signal is the signal after analog-to-digital conversion, representing the equivalent form of the received OFDM signal in the digital domain, containing all the subcarrier information.

[0118] Step 300 improves the quality and reliability of the signal through high sampling frequency analog-to-digital conversion, allowing the receiving end to more accurately acquire and process the received OFDM signal, ensuring the reliability and effectiveness of communication.

[0119] Further, after obtaining the digital baseband signal in step 300 of the embodiments of the present application, it further includes: digitally filtering the digital baseband signal to filter out high-frequency interference in the signal. The filtered digital baseband signal is down-sampled to reduce the sampling frequency to the sampling frequency during OFDM modulation. The down-sampled digital baseband signal is subjected to cyclic prefix removal to obtain a received time-domain OFDM symbol.

[0120] Specifically, after obtaining the digital baseband signal, the receiving end needs to perform a series of processing on it to extract the valid OFDM symbol and perform demodulation. First, a digital filter is used to perform digital filtering on the digital baseband signal to filter out high-frequency interference in the signal. Digital filtering refers to processing a digital signal to remove unwanted frequency components, especially high-frequency interference. The digital filter can be a FIR (Finite Impulse Response) filter or an IIR (Infinite Impulse Response) filter. Through digital filtering, the useful components in the baseband signal can be retained, while high-frequency noise and interference can be removed. Then, the filtered digital baseband signal is down-sampled to reduce the sampling frequency from a relatively high analog-to-digital conversion sampling frequency to the sampling frequency during OFDM modulation. Down-sampling refers to reducing the sampling frequency of a signal from a higher sampling rate to a lower sampling rate, which helps to reduce the complexity of data processing while matching the sampling frequency of the transmitting end. For example, if the analog-to-digital conversion sampling frequency is 2MHz, and the sampling frequency during OFDM modulation is 1MHz, then the down-sampling factor is 2.

[0121] The receiving end removes the cyclic prefix from the down-sampled digital baseband signal. Cyclic prefix removal is to remove the cyclic prefix added at the front of the signal to restore the original time-domain OFDM symbol. The cyclic prefix is added during OFDM modulation to combat multipath interference and improve system robustness. At the receiving end, the cyclic prefix is removed to restore the original time-domain OFDM symbol to obtain the received time-domain OFDM symbol. The received time-domain OFDM symbol is a time-domain OFDM signal without the cyclic prefix, which can be converted to the frequency domain and data extracted subsequently. For example, if the OFDM symbol length is 64 and the cyclic prefix length is 16, the first 16 samples need to be removed to obtain a pure OFDM symbol. Through the above sub-steps of digital filtering, down-sampling and cyclic prefix removal, the digital baseband signal is further processed to ensure good signal quality and lay a foundation for subsequent frequency domain conversion and data extraction.

[0122] Step 400: The receiving end performs a discrete Fourier transform on the digital baseband signal to obtain a frequency domain data symbol.

[0123] Specifically, the receiving end has obtained digital baseband signals through analog-to-digital conversion. These signals represent the OFDM signals received after transmission over the power line, and are expressed as a series of discrete numerical values in the digital domain. The discrete Fourier transform is performed on the digital baseband signals to decompose the time-domain signals into different frequency components, extract the data symbols on each subcarrier, and complete the conversion of the digital baseband signals from the time domain to the frequency domain. The discrete Fourier transform is a mathematical transform that converts time-domain signals into frequency-domain signals and can be implemented through the fast Fourier transform algorithm. Through the discrete Fourier transform, the receiving end obtains frequency-domain data symbols. Each frequency-domain data symbol corresponds to a subcarrier in the OFDM system and contains data information on the subcarrier. The frequency-domain data symbols can be further used for channel equalization, demodulation, and decoding to recover the original data information.

[0124] Further, the embodiment of the present application further includes the following steps after step 400:

[0125] The real part and the imaginary part of the received time-domain OFDM symbol are respectively subjected to the discrete Fourier transform to obtain the real part and the imaginary part of the frequency-domain data symbol.

[0126] The amplitude and the phase of the frequency-domain data symbol are calculated according to the real part and the imaginary part, and demodulation and decoding are performed based on the amplitude and the phase.

[0127] Specifically, the receiving end respectively subjects the real part and the imaginary part of the received time-domain OFDM symbol to the discrete Fourier transform to convert the time-domain signals into the frequency-domain signals and extract the real part and the imaginary part of the frequency-domain data symbol. The real part and the imaginary part are two components of a complex signal, the real part representing the real part of the complex number and the imaginary part representing the imaginary part of the complex number. Next, the receiving end calculates the amplitude and the phase of the frequency-domain data symbol according to the real part and the imaginary part. The amplitude and the phase are important characteristics of a complex signal, the amplitude representing the strength of the signal and the phase representing the phase angle of the signal. The specific calculation method is as follows:

[0128]

[0129] Demodulation and decoding are performed based on the calculated amplitude and phase. Demodulation is the process of extracting the original data information from the frequency-domain data symbol, and decoding is the process of converting the demodulated data into meaningful information. Common demodulation methods include QAM (Quadrature Amplitude Modulation) and PSK (Phase Shift Keying). Through the above steps, the receiving end can efficiently extract and recover the original data.

[0130] Further, the embodiment of the present application further includes the following steps after step 300:

[0131] The received OFDM signal is subjected to symbol timing synchronization and carrier frequency synchronization.

[0132] According to the synchronization result, the received time-domain OFDM symbol is subjected to timing alignment and frequency correction, to compensate for the symbol timing deviation and carrier frequency offset introduced by the channel.

[0133] Specifically, before the receiving end performs discrete Fourier transform on the digital baseband signal to obtain frequency-domain data symbols, it needs to perform symbol timing synchronization and carrier frequency synchronization on the received OFDM signal. Symbol timing synchronization refers to identifying and aligning the starting position of the received OFDM symbol at the receiving end, to ensure correct demodulation of the data. Carrier frequency synchronization refers to correcting the carrier frequency offset of the received signal at the receiving end, to ensure correct extraction and demodulation of the data. The receiving end identifies the starting position of the OFDM symbol by detecting the pilot signal or a predefined synchronization sequence, to complete symbol timing synchronization. The purpose of symbol timing synchronization is to ensure that the receiving end can correctly align the received OFDM symbol, so as to perform subsequent demodulation and processing. For example, the peak position of the pilot signal is detected using a correlation-based method, to determine the starting position of the OFDM symbol. The receiving end corrects the frequency offset of the received OFDM signal by detecting the carrier frequency offset, to complete carrier frequency synchronization. The purpose of carrier frequency synchronization is to ensure that the receiving end can correctly extract the data symbol on each subcarrier. For example, the carrier frequency offset is estimated using an FFT (Fast Fourier Transform)-based method, and then frequency correction is performed.

[0134] According to the result of symbol timing synchronization, the receiving end performs timing alignment and frequency correction on the received time-domain OFDM symbol, to compensate for the symbol timing deviation and carrier frequency offset introduced by the channel. Timing alignment refers to adjusting the starting position of the received OFDM symbol, to align it with the symbol starting position of the transmitting end. Frequency correction refers to correcting the carrier frequency offset of the received signal, to make the frequency of the received signal consistent with that of the transmitting end. Symbol timing deviation refers to the fact that the starting position of the received symbol is inconsistent with that of the transmitting end, due to the delay or jitter of the transmission path. Carrier frequency offset refers to the fact that the frequency of the received signal deviates from the predetermined value, due to the asynchronous frequency of the transmitting end and the receiving end. The receiving end first adjusts the starting position of the received time-domain OFDM symbol, to align it with the symbol starting position of the transmitting end, to compensate for the symbol timing deviation. For example, the starting position of the received symbol data is shifted, to align it with the expected position. Timing alignment helps to reduce the demodulation error caused by symbol timing deviation. Then, according to the result of carrier frequency synchronization, the frequency offset of the received signal is corrected, to make the frequency of the received signal consistent with that of the transmitting end, to compensate for the carrier frequency offset. Frequency correction helps to reduce the demodulation error caused by carrier frequency offset. For example, a complex exponential factor is multiplied to compensate for the frequency offset. Through the above two sub-steps, the receiving end can compensate for the symbol timing deviation and carrier frequency offset introduced by the channel, to improve the accuracy of signal demodulation.

[0135] Step 500: The receiving end demodulates and decodes the frequency domain data symbols to obtain a received data stream. Specifically, demodulation is the process of extracting the original data signal from the modulated signal. Decoding is the process of converting the demodulated signal into meaningful data information. The received data stream refers to the original data stream after demodulation and decoding processing.

[0136] The receiving end uses a demodulation algorithm to recover the data carried on each subcarrier according to the amplitude and phase of the frequency domain data symbols. Common demodulation methods include quadrature amplitude modulation (QAM) and phase shift keying (PSK). For example, in QAM demodulation, the real and imaginary parts of the frequency domain data symbols are mapped back to the original data signal. Then, channel equalization is used to compensate for distortion and attenuation introduced by the channel. The receiving end uses channel estimation information to perform equalization on the frequency domain data symbols to correct the effects of the channel on the signal. Common methods include linear equalization and minimum mean square error (MMSE) equalization. Then, decoding techniques such as forward error correction codes are used to detect and correct transmission errors. Decoding is the process of converting demodulated symbol data into meaningful data information. It usually includes error detection and correction, such as decoding using convolutional codes or Turbo codes, which can effectively detect and correct errors that occur during transmission. Finally, the decoded data symbols are recombined into a complete data stream. Through step 500, the receiving end achieves demodulation and decoding of the signal, thereby recovering the original data stream and completing the data information transmission process.

[0137] Further, after obtaining the received data stream in step 500 of the embodiments of the present application, the following steps are further included:

[0138] The received data stream obtained by the receiving end is compared with the original data stream of the transmitting end to calculate the bit error rate.

[0139] The calculated bit error rate is fed back to the transmitting end, which adjusts the OFDM modulation parameters according to the feedback bit error rate.

[0140] Specifically, after obtaining the received data stream, the receiving end needs to further optimize the data transmission process. The receiving end compares the received data stream with the original data stream of the transmitting end to calculate the bit error rate. The bit error rate (BER) is the ratio of the number of error bits received during communication to the total number of bits, which is an important indicator of data transmission quality, and the calculation formula is: For example, if there are 100 bits in the received data stream of the receiving end, of which 5 bits are incorrect, the bit error rate is

[0141] The receiving end feeds back the calculated error rate to the transmitting end. After receiving the feedback information, the transmitting end adjusts the OFDM modulation parameters according to the error rate to optimize data transmission. For example, if the error rate is high, the transmitting end can increase the redundancy of channel coding, reduce the order of modulation mode (e.g., from 16-QAM to QPSK), or increase the transmitting power. If the error rate is low, the transmitting end can reduce the redundancy of channel coding, increase the order of modulation mode (e.g., from QPSK to 16-QAM) to improve transmission efficiency.

[0142] The above steps achieve fast adaptation to changing environments by establishing a feedback adjustment mechanism to dynamically optimize modulation parameters, thereby improving the reliability and efficiency of data transmission.

[0143] Specifically, if the error rate is greater than a pre-set target error rate, a more robust low-order modulation mode is selected, such as from 16-QAM to QPSK. If the error rate is less than the pre-set target error rate, a higher-order modulation mode can be attempted, such as from QPSK to 16-QAM.

[0144] In addition, the modulation and coding rate is guided by a decision function;

[0145] wherein the decision function is:

[0146]

[0147] wherein ΔR is the step size of coding rate adjustment, usually 0.1 or 0.2. R old is the coding rate in the current OFDM modulation parameters; R new is the new coding rate obtained after adjusting the coding rate in the current OFDM modulation parameters. BER is the current error rate; BER target is the pre-set target error rate;

[0148] In addition, based on the current error rate BER and the pre-set target error rate BER target , the current total transmitting power of each subcarrier or the entire signal of the transmitting end is adjusted by the following formula:

[0149] P t，new = P t，old + r x (BER - BER target );

[0150] P t，new is the new total transmitting power of each subcarrier or the entire signal of the transmitting end; P t，old is the total transmitting power of each subcarrier or the entire signal of the transmitting end; and r is a pre-set adjustment factor for controlling the speed and amplitude of power change.

[0151] In summary, the communication method based on the power carrier communication system adopting OFDM provided by the embodiments of the present application has the following technical effects:

[0152] The transmitting end converts the original data stream into power-optimized OFDM signals through a series of channel coding, interleaving, subcarrier mapping, inverse discrete Fourier transform, power distribution and adjustment and other steps, so as to ensure that the data can be transmitted efficiently and reliably through the power line. The transmitting end sends the generated OFDM signals to the receiving end through the low-voltage power line. In the transmission process, the signals are transmitted to the power line through the coupling device and the interphase communication mode is used to improve the reliability and anti-interference ability of the transmission. The receiving end performs analog-to-digital conversion on the received OFDM signals to obtain a digital baseband signal, the sampling frequency of the analog-to-digital conversion is higher than that in the OFDM modulation, and the digital baseband signal is further processed through digital filtering, downsampling and cyclic prefix removal and other steps, so as to enhance the resistance to power line channel noise and interference and ensure that the received signal quality is good, thereby laying a foundation for subsequent frequency domain conversion and data extraction. The receiving end compensates for the symbol timing deviation and carrier frequency offset introduced by the channel through synchronization processing of the digital baseband signal, improves the accuracy of signal demodulation, performs discrete Fourier transform on the processed digital baseband signal to obtain frequency domain data symbols, and ensures correct reception and processing of the signal. The receiving end demodulates and decodes the frequency domain data symbols to obtain a received data stream, establishes a feedback adjustment mechanism, calculates the bit error rate and feeds it back to the transmitting end, so that the transmitting end adjusts the OFDM modulation parameters and optimizes the data transmission process.

[0153] In the description of the present application, it should be understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can be explicitly or implicitly included one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0154] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connecting", "connecting", "fixing" and other terms should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0155] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature is "over", "above" and "on top of" a second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. A first feature is "under", "below" and "underneath" a second feature can mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0156] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0157] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A communication method based on a power carrier communication system employing OFDM, characterized by, The method comprises: S1, the transmitting end carries out OFDM modulation on the original data stream to generate an OFDM signal; S2, the transmitting end sends the OFDM signal to the receiving end through the power line; S3, the receiving end carries out analog-to-digital conversion on the received OFDM signal to obtain a digital baseband signal, and the sampling frequency of the analog-to-digital conversion is higher than that in the OFDM modulation; S4, the receiving end carries out discrete Fourier transform on the digital baseband signal to obtain a frequency domain data symbol; S5, the receiving end carries out demodulation and decoding on the frequency domain data symbol to obtain a received data stream; The method further comprises, after S5: comparing the received data stream obtained by the receiving end with the original data stream of the transmitting end, calculating a bit error rate, feeding back the calculated bit error rate to the transmitting end, and the transmitting end adjusts the OFDM modulation parameters according to the fed-back bit error rate; The transmitting end adjusts the OFDM modulation parameters according to the fed-back bit error rate, which comprises: A new coding rate is obtained by adjusting the coding rate in the current OFDM modulation parameters by using a decision function; the decision function is: ； wherein, is a step size of the coding rate adjustment; is a coding rate in the current OFDM modulation parameters; is a new coding rate obtained after adjusting the coding rate in the current OFDM modulation parameters; BER is a current bit error rate; BER target is a pre-set target bit error rate; based on the current bit error rate BER and a pre-set target bit error rate BER target The current total transmitting power of each sub-carrier or the whole signal of the transmitting end is adjusted by the following formula to obtain the new total transmitting power of each sub-carrier or the whole signal of the transmitting end. P t，new =P t，old +r×(BER - BER target ); P t，new P is the new total transmit power for each subcarrier or the whole signal of the transmitting end; P t，old P is the total transmit power for each subcarrier or the whole signal of the transmitting end; r is a pre-set adjustment factor.

2. The communication method based on the power carrier communication system employing OFDM according to claim 1, characterized by, The S1 specifically comprises: S11, channel coding and interleaving are carried out on the original data stream to obtain a data symbol sequence to be modulated; S12, the data symbol sequence is mapped to each subcarrier according to the OFDM modulation parameters to form an initial frequency domain data symbol; S13, inverse discrete Fourier transform is performed on the initial frequency domain data symbol to obtain a transmitting time domain OFDM symbol; S14, a cyclic prefix is added in front of each transmitting time domain OFDM symbol to form an OFDM signal.

3. The communication method based on the power carrier communication system employing OFDM according to claim 2, characterized by, The S13 specifically comprises: S131, power allocation is carried out on the initial frequency domain data symbol to adjust the transmitting power of the data symbol on each subcarrier; S132, the initial frequency domain data symbol on each subcarrier is multiplied by a corresponding power allocation factor to obtain a power-adjusted frequency domain data symbol, so that the transmitting power of the data symbol on each subcarrier meets a preset power spectral density requirement; S133, inverse discrete Fourier transform is performed on the power-adjusted frequency domain data symbol to obtain a transmitting time domain OFDM symbol.

4. The communication method based on the power carrier communication system employing OFDM according to Claim 1, characterized by, The method further comprises, after S3: Digital filtering is carried out on the digital baseband signal to filter out high-frequency interference in the digital baseband signal; Down-sampling is carried out on the filtered digital baseband signal to reduce the sampling frequency to the sampling frequency in the OFDM modulation; Cyclic prefix removal is carried out on the down-sampled digital baseband signal to obtain a receiving time domain OFDM symbol.

5. The communication method based on the power carrier communication system employing OFDM according to claim 4, characterized by, The method further comprises, after S4: Discrete Fourier transform is respectively performed on the real part and the imaginary part of the receiving time domain OFDM symbol to obtain the real part and the imaginary part of the frequency domain data symbol; The amplitude and the phase of the frequency domain data symbol are obtained according to the real part and the imaginary part of the frequency domain data symbol.

6. The communication method based on the power carrier communication system employing OFDM according to claim 5, characterized by, The S5 specifically comprises: Demodulation and decoding are carried out on the frequency domain data symbol based on the amplitude and the phase of the frequency domain data symbol to obtain a received data stream.

7. The communication method based on the power carrier communication system employing OFDM according to claim 5, characterized by, The method further comprises, after S3: Symbol timing synchronization and carrier frequency synchronization are carried out on the received OFDM signal; According to the synchronization result, the received time-domain OFDM symbol is subjected to timing alignment and frequency correction, so as to compensate for the symbol timing deviation and carrier frequency offset introduced by the channel.

8. The communication method based on the OFDM-based power line carrier communication system according to claim 1, characterized in that, The power line is a low-voltage power line, and the transmitting end and the receiving end are electrically connected to different phase lines of the low-voltage power line respectively to realize inter-phase communication.

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