Communication method based on power line carrier communication system adopting OFDM (Orthogonal Frequency Division Multiplexing)

Abstract

The invention relates to the technical field of communication, in particular to a communication method based on a power line carrier communication system adopting OFDM (Orthogonal Frequency Division Multiplexing), which comprises the following steps: S1, a transmitting end performs OFDM modulation on an original data stream to generate an OFDM signal; s2, the transmitting end transmits the OFDM signal to a receiving end through a power line; 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; s4, the receiving end performs discrete Fourier transform on the digital baseband signal to obtain a frequency domain data symbol; and S5, the receiving end demodulates and decodes the frequency domain data symbol to obtain a received data stream. According to the method, OFDM modulation is carried out on the original data stream, so that the spectrum utilization rate is improved, the capability of resisting the multipath effect is enhanced, and efficient transmission in a complex power line environment is ensured.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a communication method based on a power line carrier communication system using OFDM. Background Art

[0002] Power Line Communication (PLC) is a communication technology that uses the existing power line distribution network as a transmission medium to achieve the transmission of comprehensive services such as data, images, and voice. PLC technology has the significant advantages of low wiring cost and wide coverage, so it has received widespread attention and application in the fields of smart home and industrial automation. Especially in scenarios where there is no need to lay additional communication lines, PLC technology can effectively reduce construction costs and quickly realize the deployment of communication networks.

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

[0004] Orthogonal Frequency Division Multiplexing (OFDM) is an efficient multi-carrier modulation technology. By decomposing 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 system's spectrum efficiency and anti-interference ability. Especially when dealing with multipath effects and frequency selective fading, OFDM technology exhibits superior performance. Therefore, introducing OFDM technology into the power carrier communication system (OFDM-PLC) has become an important technical means to 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 complex power line environments, 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, the signal attenuation is more serious, and the traditional sampling method may lead to a decrease in the accuracy of signal recovery, thereby limiting the overall performance of the system. Summary of the invention

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a communication method based on a power line 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 object, the main technical solutions adopted by the present invention include:

[0008] An embodiment of the present invention provides a communication method based on a power line carrier communication system using OFDM, the method comprising:

[0009] S1, the transmitter 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 the power line;

[0011] S3, the receiving end performs analog-to-digital conversion on the received OFDM signal to obtain a digital baseband signal, wherein 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 frequency domain data symbols;

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

[0014] Preferably, the S1 specifically includes:

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

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

[0017] S13, performing an inverse discrete Fourier transform on the initial frequency domain data symbol to obtain a transmission time domain OFDM symbol;

[0018] S14. Add a cyclic prefix before each transmitted time-domain OFDM symbol to form an OFDM signal.

[0019] Preferably, the S13 specifically includes:

[0020] S131, performing power allocation on the initial frequency domain data symbols, and adjusting the transmission power of the data symbols on each subcarrier;

[0021] S132, multiplying the initial frequency domain data symbol on each subcarrier by the corresponding power allocation factor to obtain the frequency domain data symbol after power adjustment, so that the transmission power of the data symbol on each subcarrier meets the preset power spectrum density requirement;

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

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

[0024] Perform digital filtering on the digital baseband signal to remove 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 of OFDM modulation;

[0026] The cyclic prefix is ​​removed from the downsampled digital baseband signal to obtain a received 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 received time-domain OFDM symbol respectively to obtain the real part and the imaginary part of the frequency-domain data symbol;

[0029] The amplitude and phase of the frequency domain data symbol are obtained according to the real part and the imaginary part of the frequency domain data symbol.

[0030] Preferably, the S5 specifically includes:

[0031] 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.

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

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

[0034] According to the synchronization result, timing alignment and frequency deviation correction are performed on the received time-domain OFDM symbols to compensate for the symbol timing deviation and carrier frequency offset introduced by the channel.

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

[0036] Compare the received data stream obtained by the receiving end with the original data stream of the transmitting end and calculate the bit error rate;

[0037] The calculated bit error rate is fed back to the transmitter, and the transmitter adjusts the OFDM modulation parameters 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 respectively electrically connected to different phase lines of the low-voltage power line to achieve inter-phase communication.

[0040] Preferably, the S131 specifically includes:

[0041] Perform power allocation on the initial frequency domain data symbols, and use formula (1) to adjust the transmission power of the data symbols on each subcarrier;

[0042] The formula (1) is:

[0043]

[0044] P k represents the transmit power of the kth subcarrier;

[0045] h k represents the channel gain of the kth subcarrier;

[0046] σ 2 represents the noise power;

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

[0048]

[0049]

[0050] μ k is the bandwidth requirement weight factor of the kth subcarrier, satisfying ∑ k μ k =1.

[0051] The beneficial effects of the present invention are as follows: a communication method based on a power carrier communication system using OFDM according to the present invention decomposes a high-speed data stream into multiple lower-speed data streams due to the use of OFDM modulation, and transmits them in parallel through multiple orthogonal subcarriers. The design of orthogonal subcarriers eliminates interference (ICI) between subchannels, reducing the impact of multipath effects on communication quality. Discrete Fourier transform (DFT) effectively suppresses the impact of frequency selective fading through frequency domain signal processing. This method can effectively deal with the multipath effects and frequency selective fading commonly seen in power line communications, thereby enhancing the system's anti-interference capability.

[0052] The communication method of the power carrier communication system based on OFDM of the present invention ensures the sampling accuracy by making the sampling frequency of analog-to-digital conversion (ADC) higher than the sampling frequency of OFDM modulation; and performs frequency domain processing on the signal in combination with discrete Fourier transform (DFT), so that the system can effectively estimate the channel characteristics, thereby optimizing the recovery process of the received signal. The analog-to-digital conversion step with a higher sampling frequency and the signal decoding method based on frequency domain processing enable the system to capture the signal characteristics more accurately and adapt to the complex power line channel environment.

[0053] The present invention discloses a communication method based on a power carrier communication system using OFDM. OFDM modulation technology uses multiple subcarriers to transmit data in parallel, maximizes channel capacity, and improves spectrum utilization. The parallel transmission characteristics of OFDM enable the data rate to be effectively improved; discrete Fourier transform further optimizes the spectrum orthogonality between subcarriers. The application of OFDM technology effectively solves the problem of low spectrum utilization in power carrier communication, while meeting the needs of large data transmission.

[0054] The invention discloses a communication method based on a power line carrier communication system using OFDM. The power line carrier communication uses the existing power line network as a transmission medium without the need for rewiring. The OFDM signal is directly sent to the power line without the need for additional transmission equipment. The system performance is improved by implementing frequency domain demodulation and decoding at the receiving end. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of a communication method based on a power line carrier communication system using OFDM in Embodiment 1 of the present invention;

[0056] Figure 2 This is a flow chart of a communication method based on a power line carrier communication system using OFDM in Embodiment 1 of the present invention. DETAILED DESCRIPTION

[0057] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0058] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention 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 and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0059] Embodiment 1

[0060] See also Figure 1 This embodiment provides a communication method based on a power line carrier communication system using OFDM, the method comprising:

[0061] S1. The transmitter performs OFDM modulation on the original data stream to generate an OFDM signal. In this embodiment, by using OFDM modulation technology, data can be transmitted in parallel on multiple subcarriers, which not only improves the spectrum efficiency, but also enhances the ability to combat multipath effects and frequency selective fading, thereby improving the communication quality.

[0062] S2. The transmitter sends the OFDM signal to the receiver via the power line. Specifically, the existing power line is used as the communication medium, and there is no need to lay additional dedicated communication lines, which reduces the infrastructure cost and can achieve simultaneous transmission of power and information, which is very suitable for application scenarios such as smart homes and smart grids.

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

[0064] S4. The receiving end performs a discrete Fourier transform on the digital baseband signal to obtain frequency domain data symbols. In this 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 can be separated for easy demodulation. Since the OFDM signal itself is constructed based on multiple orthogonal subcarriers, the discrete Fourier transform operation just matches this feature, 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, while 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, completing the function of the entire communication link.

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

[0067] S11. Channel code and interleave 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 add redundant information so that the receiving end can detect and correct errors that may occur during the transmission process. Interleaving technology disperses the impact of burst errors by disrupting the order of data. Even if continuous bit errors occur, only a small number of bits will be affected after deinterleaving, thereby simplifying the error correction process. Suppose that a burst interference is encountered when transmitting a data packet in a noisy environment, resulting in a continuous period of data being damaged. If there is no interleaving, then this part of the data is likely to be unrecoverable; but with interleaving, these errors will be dispersed to different locations and are easier to correct during decoding.

[0068] S12, mapping the data symbol sequence to each subcarrier according to the OFDM modulation parameters to form an initial frequency domain data symbol; by mapping the data to multiple orthogonal subcarriers, OFDM can effectively utilize spectrum resources while combating frequency selective fading. The data symbol on each subcarrier can be independently affected by the multipath effect, reducing inter-symbol interference (ISI) and improving the bandwidth utilization and transmission efficiency.

[0069] S13, perform an inverse discrete Fourier transform on the initial frequency domain data symbol to obtain a transmitted time domain OFDM symbol; perform an inverse discrete Fourier transform operation to convert the data in the frequency domain back to the time domain for transmission in the actual physical channel. This process maintains the orthogonality between the subcarriers, ensures the good characteristics of the OFDM signal, and enables the receiving end to separate the information of each subcarrier through a simple DFT.

[0070] S14. Add a cyclic prefix before each OFDM symbol in the transmitted time domain to form an OFDM signal. The cyclic prefix (CP) is a key mechanism in the OFDM system to combat inter-symbol interference caused by multipath propagation. It is actually a copy of the tail of the OFDM symbol. When this copy appears at the beginning of the symbol, even if there is multipath delay, as long as the delay does not exceed the cyclic prefix length, it will not cause interference between symbols. For example, in a complex wireless or power line environment, the time it takes for the signal to arrive at the receiving end will be different, causing a 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 delayed signals can be correctly aligned with the current symbol without affecting adjacent symbols, thereby avoiding inter-symbol interference ISI.

[0071] Specifically, the S13 specifically includes:

[0072] S131. Perform power allocation on the initial frequency domain data symbols and adjust the transmission power of the data symbols on each subcarrier. In this embodiment, different subcarriers may experience different channel conditions (such as fading, noise, etc.). Therefore, performing 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 helps to improve the overall performance of the system, such as increasing the transmission distance, improving the bit error rate (BER), or achieving more efficient spectrum use. For example, in an environment with frequency selective fading, some subcarriers may be greatly attenuated. If power adjustment is not performed, the information on these subcarriers may be lost or severely damaged. By allocating more transmission power to the more affected subcarriers, good communication quality can be maintained even under adverse conditions.

[0073] S132, multiplying the initial frequency domain data symbol on each subcarrier by the corresponding power allocation factor to obtain the frequency domain data symbol after power adjustment, so that the transmission power of the data symbol on each subcarrier meets the preset power spectrum density requirement;

[0074] In this embodiment, this process ensures that the power spectrum density of the entire signal meets the standards set by the regulatory agency and the requirements of the communication protocol, avoiding interference with other systems. In addition, it allows the power to be dynamically adjusted according to the actual channel conditions, thereby maximizing its own transmission efficiency without affecting adjacent channels.

[0075] Assuming that the maximum allowed power spectral density in a specific frequency band is specified, by calculating and applying the appropriate power allocation factor, it is possible to ensure 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 its own communication performance without violating regulations.

[0076] S133. Perform an inverse discrete Fourier transform on the power-adjusted frequency-domain data symbols to obtain the transmitted time-domain OFDM symbols. The power-adjusted frequency-domain data symbols are then converted into time-domain signals through IDFT. This step maintains the orthogonal characteristics of the OFDM signal, allowing the receiving end to separate the information of each subcarrier through a simple DFT. More importantly, since the power adjustment has been completed, the time-domain OFDM symbols generated at this time can be directly used for physical channel transmission without additional processing. Continuing with the above example, after the power adjustment is completed, a new set of frequency-domain data symbols are obtained. These symbols now not only take into account the channel conditions, but also comply with the provisions of the power spectrum density. Next, the IDFT operation converts these adjusted frequency-domain data into time-domain OFDM symbols suitable for transmission on the power line. Since all necessary adjustments have been completed, this time-domain signal can be sent directly, and the receiving end only needs to process it according to the conventional OFDM receiving process.

[0077] Specifically, after S3, the method further includes: 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 pulse noise generated by switching power supplies and electrical equipment, etc., which may appear in a higher frequency range. By using a low-pass filter, these high-frequency components can be effectively removed to reduce the impact on useful signals. The filtering process helps to increase the ratio of the signal to the background noise, thereby making subsequent demodulation more accurate and reliable.

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

[0079] The cyclic prefix is ​​removed from the downsampled digital baseband signal to obtain a received time domain OFDM symbol. In this embodiment, the cyclic prefix (CP) added by the transmitter is removed from the downsampled digital baseband signal. The main function 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 properly processed, the cyclic prefix has completed its mission. Removing it at this time can obtain a pure OFDM symbol and prepare the conditions for the subsequent DFT. Removing the cyclic prefix also helps to simplify the time synchronization process because this step can help determine the exact boundaries of each OFDM symbol, which is very important for accurately performing DFT.

[0080] In this embodiment, the method further includes after S4: performing discrete Fourier transform on the real part and imaginary part of the received time domain OFDM symbol respectively to obtain the real part and imaginary part of the frequency domain data symbol; in this embodiment, performing DFT on the real part and imaginary part respectively can more accurately restore the original frequency domain data symbol. This method ensures that the information on each subcarrier can be accurately extracted even in the presence of noise or interference. By independently processing the real part and the imaginary part, the 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] The amplitude and phase of the frequency domain data symbol are obtained according to the real part and the imaginary part of the frequency domain data symbol.

[0082] OFDM signals usually use amplitude and phase to carry information. Therefore, by obtaining the amplitude and phase of the frequency domain data symbol, it is possible to directly map back to the original data symbol to complete the demodulation process. In a complex power line environment, multipath effects may cause signal distortion. By accurately obtaining amplitude and phase information, equalization and other technologies can be used to compensate for these distortions and further improve reception performance.

[0083] In this embodiment, by performing DFT on the real part and the imaginary part respectively, and then obtaining the amplitude and phase, the entire demodulation process becomes more robust. Even in the face of complex transmission environments, such as noise and multipath effects in the power line, a high demodulation success rate can be maintained. This processing method helps to restore the quality of the original signal to the maximum extent, 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 error correction capability of the system.

[0084] In this embodiment, S5 specifically includes:

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

[0086] In a specific implementation, the method further includes after S3: performing symbol timing synchronization and carrier frequency synchronization on the received OFDM signal; and performing timing alignment and frequency deviation correction on the received time domain OFDM symbol according to the synchronization result, and compensating for the symbol timing deviation and carrier frequency offset introduced by the channel. In this embodiment, the receiving end estimates the symbol boundary by detecting a specific pilot signal or training sequence, thereby achieving symbol timing synchronization. Through accurate symbol timing synchronization, interference between adjacent symbols can be avoided and demodulation accuracy can be improved. Carrier frequency offset destroys the orthogonal relationship between subcarriers, resulting in inter-subcarrier interference (ICI). This orthogonality can be restored through frequency synchronization to ensure that the data on each subcarrier can be demodulated independently. Correct carrier frequency synchronization helps to restore the original signal more accurately, thereby reducing the bit error rate (BER) and improving the overall communication quality. The above-mentioned synchronization and deviation correction measures work together to improve the demodulation capability of the receiving end and the robustness of the system, so that high-quality communication can be maintained even under harsh channel conditions.

[0087] In this embodiment, the method further includes, 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 this embodiment, the bit error rate (BER) during 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, the coding rate, etc., 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 changes in channel conditions. When the bit error rate is high, the transmitting end can enhance the anti-interference ability by reducing the modulation order or increasing the redundant coding, thereby reducing the bit error rate and ensuring 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 spectrum efficiency and transmission rate. This method realizes the adaptability of the system, which can automatically respond to channel changes and maintain the best communication performance.

[0089] In the practical application of this 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, respectively, to realize inter-phase communication. In this embodiment, through inter-phase communication, the limitation of a single phase line can be overcome to achieve a wider network coverage. Communication between different phase lines allows signals to propagate over a larger range, increasing the coverage area and accessibility of the communication network. There may 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, the communication load can be distributed more evenly to avoid overloading a certain phase line. The frequency response characteristics of different phase lines are different, and inter-phase communication can make comprehensive use of these characteristics to improve the overall communication performance.

[0090] In this 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 using formula (1);

[0091] The formula (1) is:

[0092]

[0093] P k represents the transmission power of the kth subcarrier; h k represents the channel gain of the kth subcarrier; σ 2 represents the noise power; α kis the channel estimation error correction factor; these parameters ensure that the transmit 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 transmit power.

[0094] In this embodiment, β k Based on SINR k The calculated parameter reflects the bandwidth requirement weight factor of each subcarrier. By dynamically adjusting the power, the bandwidth resources of each subcarrier can be fully utilized to avoid resource waste. By dynamically adjusting the power, the bandwidth resources of each subcarrier can be fully utilized to avoid resource waste. k is the bandwidth requirement weight factor of the kth subcarrier, satisfying ∑ k μ k =1. In this embodiment, the transmit power of each subcarrier is adjusted to ensure the best signal-to-noise ratio in a noise and interference environment. The max(0,·) in formula (1) ensures that the transmit power will not be a negative value 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, excessive power consumption is avoided to cause device overload.

[0095] In this embodiment, the transmitting end dynamically allocates power through formula (1) so that the total transmission power of all subcarriers ∑ k P k Meet the power limit P max and optimize the power allocation strategy with the goal of maximizing the total system capacity.

[0096] Embodiment 2

[0097] This embodiment solves the technical problem that the prior art is not sufficient to completely overcome the instability and interference of power lines in terms of signal processing by providing a communication method based on a power line carrier communication system using OFDM, thereby achieving the technical effect of improving signal transmission efficiency and transmission quality.

[0098] This embodiment 2 provides a communication method based on a power line carrier communication system using OFDM, see Figure 2 , the method comprising:

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

[0100] Specifically, the transmitter is the device or device 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 transmitter first receives the original data stream, which is the original data signal that has not been processed. This data can be any information that needs to be transmitted, such as text, images, or videos. Next, the transmitter modulates this data using OFDM technology. Specifically, the transmitter segments the original data stream and assigns each segment of data to multiple subcarriers for transmission. Each subcarrier is orthogonal in the frequency domain, which means that they will not interfere with each other, can effectively utilize spectrum resources and improve the efficiency of data transmission. The transmitter uses the inverse discrete Fourier transform (IDFT) to convert these subcarriers into a composite signal, namely the OFDM signal. The OFDM signal is a signal modulated by OFDM, which contains multiple subcarriers transmitted in parallel and can then be transmitted to the receiving end through the power line.

[0101] Step 100 converts the original data stream into an OFDM signal containing multiple subcarriers through OFDM modulation to ensure that the data can be transmitted efficiently and reliably. Further, step 100 of the embodiment of the present application specifically includes:

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

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

[0104] Step 103: Perform an inverse discrete Fourier transform on the initial frequency-domain data symbols to obtain transmit time-domain OFDM symbols.

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

[0106] Specifically, channel coding refers to encoding the original data to increase redundancy and facilitate error detection and correction during transmission. Interleaving refers to rearranging the encoded data so that it is dispersed during transmission to improve the ability to resist sudden errors. First, the original data stream is channel-encoded using methods such as convolutional coding or Turbo coding to increase redundant information so that the receiving end can detect and correct errors that may occur during transmission. Next, the encoded data is interleaved using block interleaving or random interleaving methods to rearrange it so that adjacent data symbols are dispersed, thereby being more resistant to sudden interference during transmission. After channel coding and interleaving, the original data stream obtains a data symbol sequence to be modulated, and the data symbol sequence refers to the data representation after encoding and interleaving. 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. Subcarriers are independent frequency channels 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. Among them, the initial frequency domain data symbol refers to the frequency domain representation formed after the data symbol is mapped to the subcarrier. For example, in a system using 64 subcarriers, each data symbol is mapped to one of 64 frequency domain positions. Inverse Discrete Fourier Transform (IDFT) is the process of converting frequency domain data into time domain signals. The inverse discrete Fourier transform (IDFT) is performed on the initial frequency domain data symbol to convert it from the frequency domain to the time domain to form a transmitted time domain OFDM symbol. The transmitted time domain OFDM symbol refers to the time domain signal after IDFT conversion. This process can be achieved by the inverse process of the fast Fourier transform (FFT) algorithm. For example, in a system with 64 subcarriers, IDFT converts 64 frequency domain symbols into 64 time domain symbols. A cyclic prefix is ​​added before each transmitted time domain OFDM symbol. The cyclic prefix is ​​a portion of the end of the symbol copied and pasted to the beginning of the symbol, which helps to combat multipath interference and ensure that the receiving end can synchronize correctly. For example, if the OFDM symbol length is 64 and the cyclic prefix length is 16, then the first 16 samples of the symbol will be the same as the last 16 samples of the symbol.

[0107] Furthermore, step 103 of the embodiment of the present application includes:

[0108] Step 103-1: Perform power allocation on the initial frequency domain data symbols and adjust the transmit power of the data symbols on each subcarrier. Specifically, power allocation is to adjust the transmit power on each subcarrier according to preset requirements to optimize the signal transmission effect. The system allocates appropriate transmit power through a power allocation method based on the transmission conditions of each subcarrier, such as noise level and channel attenuation, to ensure the optimal signal strength of each subcarrier. 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 so that the total power is optimally allocated while meeting the power spectrum density requirements.

[0109] Step 103-2: Multiply the initial frequency domain data symbol on each subcarrier by the corresponding power allocation factor to obtain the frequency domain data symbol after power adjustment, so that the transmission power of the data symbol on each subcarrier meets the preset power spectrum density requirement. The transmitter pre-customizes a power spectrum density according to the actual signal transmission requirements. Power spectrum density refers to the power distribution per unit frequency, which affects the transmission efficiency and anti-interference ability of the signal. Multiply the initial frequency domain data symbol on each subcarrier by the corresponding power allocation factor, weight each subcarrier, and adjust the transmission power of each subcarrier to meet the preset power spectrum density requirements of the system, ensuring that the signal power of all subcarriers is optimally balanced under different transmission conditions. Among them, the power allocation factor is a coefficient used to adjust the transmission power of the data symbol on each subcarrier.

[0110] Step 103-3: Perform inverse discrete Fourier transform (IDFT) on the power-adjusted frequency-domain data symbol to obtain the power-adjusted transmit time-domain OFDM symbol. Perform inverse discrete Fourier transform (IDFT) on the power-adjusted frequency-domain data symbol again to generate the power-adjusted transmit time-domain OFDM symbol.

[0111] In this embodiment, step 100 converts the original data stream into a power-optimized OFDM signal through the above-mentioned series of sub-steps such as channel coding, interleaving, subcarrier mapping, inverse discrete Fourier transform, power allocation and adjustment, combined with the use of complex signal processing and optimization algorithms, to ensure that the data can be efficiently and reliably transmitted through 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 on the power line. The amplified signal is filtered to remove unnecessary frequency components to prevent interference with other devices. The OFDM signal is coupled to the power line using a coupling device. Coupling devices include coupling capacitors or transformers, etc., which can effectively superimpose high-frequency communication signals on low-frequency power signals. Use power lines as transmission media to transmit OFDM signals to the receiving end. Power lines have their particularities as communication media, 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 electrically connected to different phase lines of the low-voltage power line respectively to achieve inter-phase communication.

[0115] Specifically, low-voltage power lines refer to low-voltage power lines used to supply power to residential, commercial or industrial sites. These lines usually carry lower voltage power in the power system, such as 120V or 240V. 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. Interphase communication refers to the way of communicating using the voltage difference between different phase lines. In low-voltage power lines, signal transmission signals may be affected by various noise interferences and multipath effects, such as electrical switching noise, background noise, and interference from other electronic devices. Since the interference between different phase lines is usually small, the transmitter and the receiver are connected to different phase lines respectively, and the voltage difference between the phase lines is used for communication. This interphase 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, wherein 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 the received analog signal into a digital signal. The receiving end receives the OFDM signal from the power line through a coupling device. The signal is amplified and filtered to remove the noise and interference introduced during the power line transmission process. Then, the receiving end uses an analog-to-digital converter to convert the received analog OFDM signal into a digital signal to obtain a digital baseband signal. Among them, the sampling frequency of the 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 higher than the modulation sampling frequency can provide higher resolution and better anti-interference ability. For example, if the OFDM modulation sampling frequency is 1MHz, the sampling frequency of the analog-to-digital conversion 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 transmitter during the OFDM modulation process. The obtained digital baseband signal is further processed, including steps such as channel equalization, error correction and demodulation. The digital baseband signal is the signal after analog-to-digital conversion, which represents the equivalent form of the received OFDM signal in the digital domain and contains all subcarrier information.

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

[0119] Furthermore, after obtaining the digital baseband signal in step 300 of the embodiment of the present application, the method further includes: digitally filtering the digital baseband signal to filter out high-frequency interference in the signal. Downsampling the filtered digital baseband signal to reduce the sampling frequency to the sampling frequency during OFDM modulation. Removing the cyclic prefix of the downsampled digital baseband signal 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 valid OFDM symbols and demodulate it. First, use a digital filter to digitally filter the digital baseband signal to filter out high-frequency interference in the signal. Digital filtering refers to processing digital signals to remove unnecessary 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 removing high-frequency noise and interference. Then the filtered digital baseband signal is downsampled, and the sampling frequency is reduced from the higher analog-to-digital conversion sampling frequency to the sampling frequency of OFDM modulation. Downsampling refers to reducing the sampling frequency of the signal from a higher sampling rate to a lower sampling rate, which helps to reduce the complexity of data processing and match the sampling frequency of the transmitter. For example, if the sampling frequency of the analog-to-digital conversion is 2MHz, and the sampling frequency of OFDM modulation is 1MHz, the downsampling factor is 2.

[0121] The receiving end removes the cyclic prefix of the downsampled digital baseband signal. Cyclic prefix removal is to remove the cyclic prefix part added in 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 the robustness of the system. 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 the time domain OFDM signal with the cyclic prefix removed, and subsequent frequency domain conversion and data extraction can be performed. 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. The digital baseband signal is further processed through the above-mentioned sub-steps such as digital filtering, downsampling and cyclic prefix removal to ensure that the received signal quality is good, laying the foundation for subsequent frequency domain conversion and data extraction.

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

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

[0124] Furthermore, after step 400, the embodiment of the present application further includes:

[0125] Perform discrete Fourier transform 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 the frequency-domain data symbol.

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

[0127] Specifically, the receiving end performs discrete Fourier transform on the real and imaginary parts of the received time domain OFDM symbol, converts the time domain signal into a frequency domain signal, and extracts the real and imaginary parts of the frequency domain data symbol. The real part and the imaginary part are two components of a complex signal. The real part represents the real part of the complex number, and the imaginary part represents the imaginary part of the complex number. Next, the receiving end calculates the amplitude and phase based on the real and imaginary parts of the frequency domain data symbol. Amplitude and phase are important characteristics of complex signals. The amplitude represents the strength of the signal, and the phase represents 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 symbols, 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 restore the original data.

[0130] Furthermore, after step 300, the embodiment of the present application further includes:

[0131] The received OFDM signal is synchronized with the symbol timing and the carrier frequency.

[0132] According to the synchronization result, timing alignment and frequency deviation correction are performed on the received time-domain OFDM symbols 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 and obtains the frequency domain data symbol, it is necessary 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 that the data is demodulated correctly. Carrier frequency synchronization refers to correcting the carrier frequency offset of the received signal at the receiving end to ensure that the data is correctly extracted and demodulated. The receiving end detects the pilot signal or the predefined synchronization sequence to identify the starting position of the OFDM symbol and complete the symbol timing synchronization. The purpose of symbol timing synchronization is to ensure that the receiving end can correctly align the received OFDM symbol for 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 detects the carrier frequency offset, corrects the frequency offset of the received OFDM signal, and completes the 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 the 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 so that the received signal frequency is consistent with the signal frequency of the transmitting end. Symbol timing deviation refers to the inconsistency between the starting position of the received symbol and the transmitting end due to the delay or jitter of the transmission path. Carrier frequency offset refers to the deviation of the frequency of the received signal from the predetermined value due to the frequency asynchronization between 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 and compensate for the symbol timing deviation. For example, by shifting the received symbol data, its starting position is aligned 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 so that the received signal frequency is consistent with the signal frequency of the transmitting end and the carrier frequency offset is compensated. Frequency correction helps to reduce the demodulation error caused by carrier frequency offset. For example, the frequency offset is compensated by multiplying by a complex exponential factor. Through the above two sub-steps, the receiving end can compensate for the symbol timing deviation and carrier frequency offset introduced by the channel, thereby improving 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.

[0136] The receiving end uses a demodulation algorithm to recover the data carried on each subcarrier based on the amplitude and phase of the frequency domain data symbol. 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 symbol are mapped back to the original data signal. Then, the distortion and attenuation introduced by the channel are compensated by channel equalization. The receiving end uses the channel estimation information to equalize the frequency domain data symbol to correct the impact 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 to convert the demodulated symbol data into meaningful data information. It usually includes error detection and correction. For example, decoding using convolutional codes or Turbo codes can effectively detect and correct errors that occur during transmission. Finally, the decoded data symbols are reorganized into a complete data stream. Through step 500, the receiving end realizes demodulation and decoding of the signal, thereby restoring the original data stream and completing the data information transmission process.

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

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

[0139] The calculated bit error rate is fed back to the transmitter, and the transmitter adjusts the OFDM modulation parameters according to the fed-back bit error rate.

[0140] Specifically, after the receiving end obtains the received data stream, it 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) refers to the ratio of the number of erroneous bits received to the total number of bits during the communication process. It is an important indicator for measuring the quality of data transmission. The calculation formula is: For example, if the data stream received by the receiver contains 100 bits and 5 of them are erroneous, the bit error rate is

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

[0142] The above steps achieve rapid adaptation to changing environments and improve the reliability and efficiency of data transmission by establishing a feedback adjustment mechanism and dynamically optimizing modulation parameters.

[0143] Specifically, if the bit error rate is greater than the preset target bit error rate, a more robust low-order modulation method is selected, such as reducing from 16-QAM to QPSK. If the bit error rate is less than the preset target bit error rate, a higher-order modulation method can be tried, such as increasing from QPSK to 16-QAM.

[0144] In addition, a decision function is used to guide the modulation coding rate;

[0145] Among them, this decision function is:

[0146]

[0147] Where ΔR is the step size of the coding rate adjustment, usually 0.1 or 0.2. old is the coding rate in the current OFDM modulation parameters; R new is the new coding rate obtained by adjusting the coding rate in the current OFDM modulation parameters. BER is the current bit error rate; BER target is a preset target bit error rate;

[0148] In addition, based on the current bit error rate BER and the preset target bit error rate BER target , the current total transmit power of each subcarrier or the entire signal at the transmitter is adjusted by the following formula:

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

[0150] P t，new is the new total transmit power of each subcarrier or the entire signal at the transmitter; P t，old is the total transmission power of each subcarrier or the entire signal at the transmitting end; r is a preset adjustment factor used to control the speed and amplitude of power change.

[0151] In summary, the communication method based on the power line carrier communication system using OFDM provided in the embodiment of the present application has the following technical effects:

[0152] The transmitter performs OFDM modulation on the original data stream, and converts the original data stream into a power-optimized OFDM signal through a series of steps such as channel coding, interleaving, subcarrier mapping, inverse discrete Fourier transform, power allocation and adjustment, ensuring that the data can be efficiently and reliably transmitted through the power line. The transmitter sends the generated OFDM signal to the receiver through the low-voltage power line. During the transmission process, the signal is transmitted to the power line through the coupling device, and the reliability and anti-interference ability of the transmission are improved through the phase-to-phase communication method. The receiver performs analog-to-digital conversion on the received OFDM signal to obtain a digital baseband signal. The sampling frequency of the analog-to-digital conversion is higher than the sampling frequency during OFDM modulation, and the digital baseband signal is further processed through digital filtering, downsampling and cyclic prefix removal to enhance the resistance to power line channel noise and interference, ensure the received signal quality is good, and lay the foundation for subsequent frequency domain conversion and data extraction. The receiving end performs synchronous processing on the digital baseband signal, compensates for the symbol timing deviation and carrier frequency offset introduced by the channel, improves the accuracy of signal demodulation, performs discrete Fourier transform on the processed digital baseband signal, obtains frequency domain data symbols, and ensures the correct reception and processing of the signal. The receiving end demodulates and decodes the frequency domain data symbols to obtain the 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 can adjust the OFDM modulation parameters and optimize the data transmission process.

[0153] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0154] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0155] In the present invention, unless otherwise clearly specified and limited, when a first feature is “on” or “below” a second feature, it may be that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, when a first feature is “above”, “above” or “above” a second feature, it may be that the first feature is directly above or obliquely above the second feature, or it may simply mean that the first feature is higher in level than the second feature. When a first feature is “below”, “below” or “below” a second feature, it may be that the first feature is directly below or obliquely below the second feature, or it may simply mean that the first feature is lower in level than the second feature.

[0156] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0157] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A communication method based on a power line carrier communication system using OFDM, characterized in that: The method comprises: S1, the transmitter performs 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 performs analog-to-digital conversion on the received OFDM signal to obtain a digital baseband signal, wherein the sampling frequency of the analog-to-digital conversion is higher than the sampling frequency during OFDM modulation; S4, the receiving end performs discrete Fourier transform on the digital baseband signal to obtain frequency domain data symbols; S5. The receiving end demodulates and decodes the frequency domain data symbols to obtain a received data stream.

2. The communication method based on the power line carrier communication system using OFDM according to claim 1, characterized in that: The S1 specifically includes: S11, performing channel coding and interleaving on the original data stream to obtain a data symbol sequence to be modulated; S12, mapping the data symbol sequence to each subcarrier according to the OFDM modulation parameters to form an initial frequency domain data symbol; S13, performing an inverse discrete Fourier transform on the initial frequency domain data symbol to obtain a transmission time domain OFDM symbol; S14. Add a cyclic prefix before each transmitted time-domain OFDM symbol to form an OFDM signal.

3. The communication method based on the power line carrier communication system using OFDM according to claim 2, characterized in that: The S13 specifically includes: S131, performing power allocation on the initial frequency domain data symbols, and adjusting the transmission power of the data symbols on each subcarrier; S132, multiplying the initial frequency domain data symbol on each subcarrier by the corresponding power allocation factor to obtain the frequency domain data symbol after power adjustment, so that the transmission power of the data symbol on each subcarrier meets the preset power spectrum density requirement; S133, performing inverse discrete Fourier transform on the power-adjusted frequency-domain data symbols to obtain transmit time-domain OFDM symbols.

4. The communication method based on the power line carrier communication system using OFDM according to claim 1, characterized in that: The method further comprises, after S3: Perform digital filtering on the digital baseband signal to remove high-frequency interference in the digital baseband signal; Down-sampling the filtered digital baseband signal to reduce the sampling frequency to the sampling frequency of OFDM modulation; The cyclic prefix is ​​removed from the downsampled digital baseband signal to obtain a received time-domain OFDM symbol.

5. The communication method based on the power line carrier communication system using OFDM according to claim 4 is characterized in that: The method further comprises after S4: Performing discrete Fourier transform 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 the frequency-domain data symbol; The amplitude and 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 line carrier communication system using OFDM according to claim 5, characterized in that: The S5 specifically includes: 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.

7. The communication method based on the power line carrier communication system using OFDM according to claim 5, characterized in that: The method further comprises, after S3: Perform symbol timing synchronization and carrier frequency synchronization on the received OFDM signal; According to the synchronization result, timing alignment and frequency deviation correction are performed on the received time-domain OFDM symbols to compensate for the symbol timing deviation and carrier frequency offset introduced by the channel.

8. The communication method based on the power line carrier communication system using OFDM according to claim 7, characterized in that: After S5, the method further includes: Compare the received data stream obtained by the receiving end with the original data stream of the transmitting end and calculate the bit error rate; The calculated bit error rate is fed back to the transmitter, and the transmitter adjusts the OFDM modulation parameters according to the fed-back bit error rate.

9. The communication method based on the power line carrier communication system using OFDM 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 respectively electrically connected to different phase lines of the low-voltage power line to achieve inter-phase communication.

10. The communication method based on the power line carrier communication system using OFDM according to claim 3, characterized in that: The S131 specifically includes: Perform power allocation on the initial frequency domain data symbols, and use formula (1) to adjust the transmission power of the data symbols on each subcarrier; The formula (1) is: P k represents the transmit power of the kth subcarrier; h k represents the channel gain of the kth subcarrier; σ 2 represents the noise power; α k is the channel estimation error correction factor; μ k is the bandwidth requirement weight factor of the kth subcarrier, satisfying ∑ k μ k =1.

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