CN116389214B - Noise reduction method, noise reduction terminal and medium suitable for voltage power line carrier communication - Google Patents
Noise reduction method, noise reduction terminal and medium suitable for voltage power line carrier communication Download PDFInfo
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Abstract
The invention discloses a noise reduction method, a noise reduction terminal and a medium suitable for power line carrier communication of a voltage, which belong to the technical field of data communication, wherein a transmitting end carries out quadrature phase shift keying modulation and inverse discrete Fourier transform on an original signal, a training sequence is added at the same time, and signal interleaving is carried out through an interleaver; then transmitting the signals to a receiving end through a power line, de-interleaving and Fourier transforming the received signals at the receiving end, estimating signal response and balancing, and carrying out noise reduction treatment on the signals by detecting and treating impulse noise; the invention effectively improves the performance of the power line carrier communication of the voltage, reduces the noise influence in communication signals, is beneficial to improving the communication quality, and has obvious practical value and wide application prospect.
Description
Technical Field
The invention relates to the technical field of data communication, in particular to a noise reduction method, a noise reduction terminal and a medium suitable for power line carrier communication.
Background
Power line carrier communication (PowerLineCommunication, PLC) is a technique for data transmission using existing power lines. This technique is very useful in many applications, such as smart grids, home automation, internet access, etc. However, the power line is a very complex transmission medium, and there is much noise and interference, which has a great influence on the performance of the power line carrier communication.
The low-voltage power line is used as a signal transmission medium so that the data signal is transmitted over the power line. Because the power line is mainly used for power transmission rather than communication in design, communication signals can be affected by various noises in practical application, and the reliability and quality of communication are reduced. In particular, impulse noise has large amplitude and strong time variability, and has remarkable influence on a communication system.
In a conventional power line carrier communication system, a noise reduction method that is generally used includes filtering, equalization, and the like. The filtering is to remove signals in the noise frequency range by designing a filter, thereby achieving the purpose of noise reduction. However, these methods do not work well for bursty noise because both the frequency and time domain characteristics of bursty noise are uncertain. Therefore, noise reduction to improve signal quality is an urgent problem to be solved in the field of power line communication.
Disclosure of Invention
The invention aims to provide a noise reduction method, a noise reduction terminal and a medium suitable for power line carrier communication at the current stage, which solve the technical problem that the signal transmission quality of the power line carrier communication at the current stage is poor, and realize effective noise reduction of the power line carrier communication at the current stage.
The invention is realized by the following technical scheme:
a noise reduction method suitable for power line carrier communication of a voltage, wherein a transmitting end and a receiving end are connected through a power line, the noise reduction method comprises the following steps: mapping the original signal into a first matrix block signal modulated by quadrature phase shift keying at a transmitting end;
performing inverse discrete Fourier transform on the first matrix block signal to obtain a time domain signal;
adding a known training sequence into the time domain signal;
inputting the time domain signal added with the training sequence into an interleaver, and interleaving the time domain signal to obtain a transmission signal;
performing digital-to-analog conversion on the transmission signal, and transmitting the transmission signal to a power line;
receiving the transmission signal at a receiving end, de-interleaving the transmission signal to obtain a receiving signal, and performing Fourier transform on the receiving signal to obtain a first frequency domain signal;
estimating a signal response based on the received training sequence; and equalizing the first frequency domain signal using the estimated signal response;
mapping the equalized first frequency domain signal into a second matrix block signal modulated by quadrature phase shift keying;
converting the second matrix block signal into a serial signal, and obtaining average power of noise in the serial signal;
acquiring a pulse noise detection threshold, and determining a noise threshold=the pulse noise detection threshold×average power; detecting the serial signal through a noise threshold to obtain impulse noise;
performing Fourier transformation on the impulse noise to obtain a second frequency domain signal, wherein the second frequency domain signal is the frequency domain signal of the impulse noise;
obtaining a noise-reduced frequency-domain signal, noise-reduced frequency-domain signal = first frequency-domain signal-second frequency-domain signal;
and performing inverse Fourier transform on the noise reduction frequency domain signal to obtain a noise reduction signal.
Specifically, at a transmitting end, a transmitting signal is distributed to a plurality of subcarriers by an orthogonal frequency division multiplexing technology; at the receiving end, the signals on the plurality of sub-carriers are recovered into transmission signals by an orthogonal frequency division multiplexing technology.
Optionally, the method for interleaving the time domain signal comprises:
constructing an interleaver, which consists ofColumn matrix block and->A row matrix block;
an interleaver performance evaluation model is obtained,wherein->For cumulative distribution function->Is the spreading factor of a two-dimensional interleaver, +.>For the sampling time length, +.>Is pulse duration mean +.>For pulse duration, +.>Is a natural constant;
setting an evaluation thresholdAnd evaluating the performance of the constructed interleaver if +.>Then the interleaver performance is determined to be disqualified and +.>Is a value of (2); if->Continuously judging that the performance of the interleaver is qualified;
randomly interweaving a plurality of different OFDM symbol blocks, wherein the minimum interweaving distance is as followsWherein->Is a set constant greater than 0;
a plurality of OFDM symbol blocks on each subcarrier are cyclically shifted interleaved.
Optionally, after obtaining the time domain signal of the first matrix block signal, each OFDM symbol in the time domain signal is preceded by a length ofAnd updated to a new time domain signal +.>Wherein->For an updated time domain signal +.>For the pre-update time domain signal +.>Is a mapping matrix;
after the receiving end obtains the received signal, the cyclic prefix of the received signal is removed, and then fourier transformation is performed to obtain a first frequency domain signal.
Specifically, the method for obtaining the average power of noise in the serial signal comprises the following steps:
converting serial signals to the frequency domain by fast fourier transformation：/>Wherein->，/>Is the number of data subcarriers; />Is the frequency domain of the signal, +.>Frequency domain of background noise, +.>Is the frequency domain of impulse noise;
the frequency domain is usedInputting to hard decision module, placing pilot symbol at pilot sub-carrier position, inserting zero at other positions, and demodulating according to QPSK modulation mode to obtain signal +.>；
Determining noise signals：/>Wherein->Is a serial signal;
performing inverse Fourier transform on the noise signal to obtain an estimated value of the noise；
Obtaining average power of noise：/>Wherein->Is the length of the noise signal.
Optionally, the method for obtaining the impulse noise detection threshold includes:wherein->For the interference rate of impulse noise +.>For the received signal power without impulse noise occurrence, +.>For the power of the received signal with impulse noise generation, < >>For the received signal power without impulse noise occurrence, +.>Is the power of the received signal with impulse noise occurring.
In particular, the method comprises the steps of,wherein->For the power of the signal in the received signal, +.>As the power of the background noise,power for impulse noise; />，/>Is the interference ratio of impulse noise.
Optionally, the detection operation of the serial signal by the noise threshold is performed to obtain impulse noiseThe method of (1) comprises:wherein->Is an estimated value of noise +.>Is impulse noise detection threshold, < >>Is the average power of the noise.
A noise reducing terminal adapted for low voltage power line carrier communication comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the method as described above when the computer program is executed.
A computer readable storage medium storing a computer program which, when executed by a processor, implements the steps of a method as described above.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the invention carries out quadrature phase shift keying modulation and inverse discrete Fourier transform on the original signal at the transmitting end, simultaneously adds a training sequence, and carries out signal interleaving through an interleaver. The receiving end de-interleaves the received signal, performs Fourier transform, estimates the signal response and performs equalization. Meanwhile, the noise reduction processing is further carried out on the signals by detecting and processing impulse noise; the invention effectively improves the performance of the power line carrier communication of the voltage, reduces the noise influence in communication signals, is beneficial to improving the communication quality, and has obvious practical value and wide application prospect.
By performing quadrature phase shift keying modulation on the signal and by adding training sequences and interleaving, impulse noise and other forms of noise can be effectively resisted, thereby significantly improving communication quality.
By using signal response estimation and equalization processing at the receiving end, multipath interference and time variability in the power line communication system can be effectively counteracted, thereby enhancing the stability of the system.
By detecting and processing impulse noise, the noise influence in the communication signal can be effectively reduced, and the quality and reliability of communication are further improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the principles of the invention.
Fig. 1 is a communication schematic diagram of a noise reduction method suitable for use in the power line carrier communication according to the present invention.
Fig. 2 is a schematic flow chart of a transmitting end in a noise reduction method suitable for the voltage power line carrier communication according to the present invention.
Fig. 3 is a schematic flow chart of a receiving end in a noise reduction method suitable for the voltage power line carrier communication according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and embodiments, for the purpose of making the objects, technical solutions and advantages of the present invention more apparent. It is to be understood that the specific embodiments described herein are merely illustrative of the substances, and not restrictive of the invention.
It should be further noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.
Embodiments of the present invention and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
Example 1
The low-voltage power line carrier communication is a communication technology for transmitting information by using an existing power line. Because the power lines are distributed throughout each home and office, the PLC technology has a wide application prospect. The intelligent household appliance can realize household automation, such as intelligent ammeter reading, remote control of household appliances and the like; the method can also be applied to broadband internet access and even remote monitoring of the power system.
However, the voltage power line carrier communication faces many challenges in practical use, the most dominant of which is the noise problem. Since the power line is originally used to transmit electric energy, not information, its transmission environment is quite complex, and noise sources mainly include background noise and impulse noise: how to effectively process these noises and reduce their influence on the performance of power line carrier communication is a key problem to be solved by the current power line communication technology.
As shown in fig. 1, the transmitting end and the receiving end are connected by a power line, and the present embodiment provides a noise reduction method suitable for the carrier communication of a voltage power line as shown in fig. 2 and 3, and the noise reduction method in the present embodiment includes:
the method comprises the steps that firstly, an original signal is mapped into a quadrature phase shift keying modulated first matrix block signal at a transmitting end;
quadrature phase shift keying (QuadraturePhaseShiftKeying, QPSK) is a digital modulation method in which two orthogonal carriers (90 degrees out of phase) are modulated and added simultaneously to transmit binary data. In this step, the original binary data signal is mapped into a QPSK modulated signal. This mapping is typically done by a look-up table, with every two bits of data corresponding to one symbol of QPSK. For example, '00' may correspond to one particular symbol, '01' to another symbol, and so on.
By "first matrix block signal" is meant that the original data is divided into blocks (each block containing a plurality of bits) and then each block is mapped to one QPSK symbol. This approach, known as block coding, may improve the reliability of the data transmission. Because in block coding, even if some bits are lost or erroneous, the original data can still be recovered by the correct bits that have been received.
Performing inverse discrete Fourier transform on the first matrix block signal to obtain a time domain signal;
the discrete fourier transform (DiscreteFourierTransform, DFT) is an algorithm that converts a signal from the time domain to the frequency domain. In this step an inverse discrete fourier transform (InverseDiscreteFourierTransform, IDFT) is performed with the purpose of converting the first matrix block signal in the frequency domain back into the time domain. This has the advantage that the time domain signal is more effectively resistant to channel noise and interference when transmitted in the physical channel.
Thirdly, adding a known training sequence into the time domain signal;
the training sequence is a predefined, known signal sequence, typically inserted before or in the transmitted signal. The receiving end can estimate the characteristics of the channel, including fading, phase shift, etc. of the channel by comparing the received training sequence with the original training sequence, thereby performing corresponding signal processing to improve the signal quality.
Fourth, inputting the time domain signal added with the training sequence to an interleaver, and interleaving the time domain signal to obtain a transmission signal;
interleaving (Interleaving) may improve the reliability of signals in a harsh communication environment. The main idea of interleaving is to spread consecutive data to be transmitted at different points in time so that even if the signal at a certain point in time is severely disturbed, the reception of the whole data block is not affected. In this step, the time domain signal to which the training sequence is added is input to an interleaver, and the interleaver interleaves the time domain signal to obtain an interleaved transmission signal.
Fifthly, performing digital-to-analog conversion on the sending signal, and transmitting the sending signal to a power line;
the interleaved digital signal is converted to an analog signal because the power lines transmit information by transmitting analog voltages and currents. Digital-to-AnalogConverter, DAC converts Digital signals to analog signals. The analog signal is then transmitted to the power line via an appropriate line driver. In this way, the voltage power line is able to transmit data signals.
Sixthly, receiving the transmission signal at a receiving end, de-interleaving the transmission signal to obtain a receiving signal, and performing Fourier transform on the receiving signal to obtain a first frequency domain signal;
at the receiving end, the analog signal on the power line is received first. The analog signal contains digital information that is added at the transmitting end. In order to recover the original digital information, the analog signal needs to be subjected to analog-to-digital conversion to obtain a digital signal. Then, this digital signal is subjected to a deinterleaving operation, which is the inverse of interleaving, in order to restore data scattered at the transmitting end in order to combat channel interference to the original continuous data. After the deinterleaving, a reception signal is obtained. And finally, carrying out Fourier transform on the received signal, and converting the received signal into a frequency domain signal to obtain a first frequency domain signal.
Seventh, estimating signal response according to the received training sequence; and equalizing the first frequency domain signal using the estimated signal response;
in this step, the received training sequence is used to estimate the signal response. The signal response describes the changes that the signal undergoes during transmission, including attenuation, phase shift, etc. By comparing the received training sequence with the original training sequence inserted by the transmitting end, the signal response can be estimated. This estimated signal response is then used to equalize the first frequency domain signal. The purpose of the equalization is to adjust the signal based on the signal response in order to more accurately recover the original signal.
Eighth step, the first frequency domain signal after equalization is mapped into a second matrix block signal modulated by quadrature phase shift keying;
the equalized first frequency domain signal is mapped to a quadrature phase shift keying modulated second matrix block signal. This step is in effect converting the signal from the frequency domain back to the time domain. Quadrature phase shift keying modulation is a common signal modulation scheme that can effectively transmit digital signals. After this step a second matrix block signal is obtained, which can be further processed to recover the original information.
Ninth, converting the second matrix block signal into a serial signal, and obtaining average power of noise in the serial signal;
the second matrix block signal is converted into a serial signal. Serial signals refer to signals that are transmitted sequentially in time sequence, in contrast to parallel signals (signals transmitted simultaneously). During the conversion, the average power of the noise in the serial signal can be calculated and obtained. The average noise power is the average value of noise power in a certain period of time, and can be used for measuring the intensity of noise.
Tenth, acquiring a pulse noise detection threshold, and determining a noise threshold=the pulse noise detection threshold×average power; detecting the serial signal through a noise threshold to obtain impulse noise;
firstly, a pulse noise detection threshold is obtained and used for judging whether pulse noise exists in a signal. The noise threshold is then determined based on this threshold and the noise average power calculated in the previous step. And then, detecting the serial signal through the noise threshold, and if the power of the signal exceeds the noise threshold, considering that impulse noise exists in the signal and recording the part of the signal.
Eleventh step, fourier transform is carried out on the impulse noise to obtain a second frequency domain signal, wherein the second frequency domain signal is the frequency domain signal of the impulse noise;
and (3) carrying out Fourier transform on the impulse noise obtained in the tenth step, and converting the impulse noise from a time domain to a frequency domain to obtain a second frequency domain signal. This frequency domain signal is the frequency domain representation of impulse noise.
A twelfth step of obtaining a noise reduction frequency domain signal, noise reduction frequency domain signal=first frequency domain signal-second frequency domain signal;
the first frequency domain signal (i.e., the frequency domain signal obtained from the original received signal and subjected to a series of processing) and the second frequency domain signal (i.e., the frequency domain signal obtained from impulse noise) are subjected to a subtraction operation, resulting in a noise reduction frequency domain signal. This process can be understood as removing the component of impulse noise from the original signal.
And thirteenth step, performing inverse Fourier transform on the noise reduction frequency domain signal to obtain a noise reduction signal.
And (3) performing inverse Fourier transform on the noise reduction frequency domain signal obtained in the twelfth step, and converting the noise reduction frequency domain signal from the frequency domain to the time domain to obtain a noise reduction signal. This noise reduction signal is the final output, which achieves that the effect of impulse noise is removed from the original signal.
By performing this series of steps, noise reduction processing can be effectively performed on the voltage power line carrier communication. First, quadrature phase shift keying modulation and discrete fourier transform are used, and training sequences are added and signal interleaving is performed, which all contribute to the stability of the signal and the noise immunity during signal transmission. Then, at the receiving end, signal de-interleaving and fourier transformation are used, as well as estimation and equalization of the signal response, which steps help to accurately restore the original signal when receiving the signal. Finally, by detecting impulse noise and removing it from the original signal, noise reduction processing of the signal is achieved. Therefore, the method can effectively reduce the influence of noise and improve the performance of the power line carrier communication at the voltage while maintaining the signal transmission quality.
Example two
In order to improve the anti-interference capability and the frequency band utilization rate, a transmitting signal is distributed to a plurality of subcarriers at a transmitting end through an orthogonal frequency division multiplexing technology; at the receiving end, the signals on the plurality of sub-carriers are recovered into transmission signals by an orthogonal frequency division multiplexing technology.
Orthogonal frequency division multiplexing (OrthogonalFrequencyDivisionMultiplexing, OFDM) is a multi-carrier transmission technique that is effective against frequency selective fading and interference of channels in high-speed data transmission.
OFDM divides the entire frequency band into a plurality of independent, mutually orthogonal subcarriers, each of which independently transmits data. At the transmitting end, the input high-speed data stream is divided into a plurality of lower-speed parallel data streams, and each parallel data stream is mapped to one subcarrier for transmission. The orthogonality between the sub-carriers ensures that they do not interfere with each other in the frequency domain. The process of distributing the transmission signal to the plurality of sub-carriers is to multiplex the signal in the frequency domain, thereby increasing the frequency band utilization rate and the data transmission rate.
At the receiving end, the signal on each subcarrier is independently demodulated and recovered, and then the data streams on all subcarriers are recombined into the original high-speed data stream. Because the subcarriers are orthogonal, the signals on each subcarrier can be separated in a simple manner without affecting each other.
In a fourth step, in order to discretize the influence of burst noise, an interleaver is added in the communication process to discretize the noise, and the method for interleaving the time signal comprises the following steps:
constructing a 2-dimensional interleaver consisting ofColumn matrix block and->A row matrix block; the input data is first filled into the matrix by columns and then read out by rows, thus realizing the reordering of the data.
The performance results of the interleaver are mainly due to the duration of the burst noise generation and the interleaving depth of the interleaverAnd (5) determining. In the practical test, the impulse noise duration time generated by the indoor electric appliance is exponentially distributed, in order to measure the interleaving performance of the interleaver, the performance of the interleaver is evaluated by adopting a complementary cumulative distribution function, thus constructing an interleaver performance evaluation model,wherein->For cumulative distribution function->Is the spreading factor of a two-dimensional interleaver, +.>，/>For the sampling time length, +.>Is pulse duration mean +.>For pulse duration;
setting an evaluation thresholdAnd evaluating the performance of the constructed interleaver if +.>Then the interleaver performance is determined to be disqualified and +.>Is a value of (2); if->Continuously judging that the performance of the interleaver is qualified; i.e. to obtain good interleaving performance, the size of the interleaver column +.>Can be properly adjusted according to actual needs to ensure the interleaving effect.
Randomly interweaving a plurality of different OFDM symbol blocks, wherein the minimum interweaving distance is as followsWherein->Is a set constant greater than 0;
a plurality of OFDM symbol blocks on each subcarrier are cyclically shifted interleaved. The first position of each row of the interleaver is shifted to l' = (l+m) mod l, where m is the m-th row of the interleaver; mod is a modulo operation, i.e. burst noise occurring on one OFDM symbol block is randomly dispersed to L different OFDM symbols, each OFDM symbol only contains a few sporadic pulse samples, and at the same time, the special interleaving method can ensure that data on the same subcarrier is not spread to other subcarriers, so that the frequency domain channel maintains an equalization effect.
In a communication system, OFDM (orthogonal frequency division multiplexing) technology is widely used because it can efficiently cope with the influence of multipath channels. However, multipath propagation may cause so-called "inter-symbol interference" (ISI) because multiple copies of one symbol may arrive at the receiver at the same time, resulting in symbol confusion. To solve this problem, a cyclic prefix is typically added before each OFDM symbol.
After obtaining the time domain signal of the first matrix block signal, each OFDM symbol in the time domain signal is added with a length ofAnd updated to a new time domain signal +.>Wherein->For an updated time domain signal +.>For the pre-update time domain signal +.>Is a mapping matrix;
the cyclic prefix is a signal that adds a small segment at the beginning of each OFDM symbol, which is a replica of the end portion of the OFDM symbol. Thus, even if a portion of the signal arrives at the receiver due to multipath propagation, it does not interfere with the next symbol because this portion of the signal is identical to the end of the OFDM symbol. Thus, the cyclic prefix can effectively cancel ISI.
After the receiving end obtains the received signal, the cyclic prefix of the received signal is removed, and then fourier transformation is performed to obtain a first frequency domain signal.
At the receiving end, the cyclic prefix added before each OFDM symbol is first removed, and then the remaining signals are fourier transformed to obtain signals in the frequency domain. This is because OFDM symbols are orthogonal to each other in the frequency domain, and demodulation can be performed easily.
Example III
The embodiment describes a method for obtaining average power of noise in a serial signal, the method including:
converting serial signals to the frequency domain by fast fourier transformation：/>Which is provided withMiddle->，/>Is the number of data subcarriers; />Is the frequency domain of the signal, +.>Frequency domain of background noise, +.>Is the frequency domain of impulse noise;
the frequency domain is usedInputting to hard decision module, placing pilot symbol at pilot sub-carrier position, inserting zero at other positions, and demodulating according to QPSK modulation mode to obtain signal +.>；
By combining frequency domain signalsInput to a hard decision module. Hard decisions refer to quantization decisions on the received signal, typically with only two possible outcomes: 0 or 1. In the hard decision module, pilot symbols are placed at the pilot subcarrier positions, and zeros are inserted at other positions, so as to facilitate the subsequent demodulation process. Then, the signal is demodulated in a QPSK (Quadrature Phase Shift Keying, quadrature phase keying) manner to obtain a signal +.>。
Determining noise signals：/>Wherein->Is serial signal>In fact representing the signal differences due to noise.
Performing inverse Fourier transform on the noise signal to obtain an estimated value of the noise；
Obtaining average power of noise：/>Wherein->Is the length of the noise signal, i.e. the number of samples in the noise signal. This length may be determined based on the actual signal sampling rate and the duration of the signal.
For example, there is a sampling rate of 1000Hz for one signal, that is, 1000 sample points per second are acquired. If this signal is observed for 1 second we will get 1000 sample points, hence the length of this signal1000.
In practice, it is necessary to determine the characteristics of the signal (such as sampling rate, duration, etc.) and the requirementsIs a value of (2).
In this embodiment, the pulse noise is obtained by detecting the serial signal with the noise thresholdThe method of (1) comprises: />The above solves for the average power +.>The following is a pulse noise detection threshold->The method of obtaining (c) is described.
The method for obtaining the impulse noise detection threshold comprises the following steps:wherein->For the interference rate of impulse noise +.>For the received signal power without impulse noise occurrence, +.>Is the power of the received signal with impulse noise occurring.
Wherein->For the power of the signal in the received signal, +.>Power for background noise +.>Is the power of the impulse noise.
Example IV
A noise reduction terminal suitable for low voltage power line carrier communication comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the method as described above when executing the computer program.
The memory may be used to store software programs and modules, and the processor executes various functional applications of the terminal and data processing by running the software programs and modules stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an execution program required for at least one function, and the like.
The storage data area may store data created according to the use of the terminal, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other volatile solid-state storage device.
A computer readable storage medium storing a computer program which when executed by a processor performs the steps of a noise reduction method suitable for use in a voltage power line carrier communication as described above.
Computer readable media may include computer storage media and communication media without loss of generality. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instruction data structures, program modules or other data. Computer storage media includes RAM, ROM, EPROM, EEPROM, flash memory or other solid state memory technology, CD-ROM, DVD or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices. Of course, those skilled in the art will recognize that computer storage media are not limited to the ones described above. The above-described system memory and mass storage devices may be collectively referred to as memory.
In the description of the present specification, reference to the terms "one embodiment/manner," "some embodiments/manner," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/manner or example is included in at least one embodiment/manner or example of the present application. In this specification, the schematic representations of the above terms are not necessarily for the same embodiment/manner or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/modes or examples described in this specification and the features of the various embodiments/modes or examples can be combined and combined by persons skilled in the art without contradiction.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless explicitly defined otherwise.
It will be appreciated by persons skilled in the art that the above embodiments are provided for clarity of illustration only and are not intended to limit the scope of the invention. Other variations or modifications of the above-described invention will be apparent to those of skill in the art, and are still within the scope of the invention.
Claims (9)
1. The noise reduction method suitable for the power line carrier communication of the voltage is characterized in that a transmitting end and a receiving end are connected through a power line, and the noise reduction method comprises the following steps:
mapping the original signal into a first matrix block signal modulated by quadrature phase shift keying at a transmitting end;
performing inverse discrete Fourier transform on the first matrix block signal to obtain a time domain signal;
adding a known training sequence into the time domain signal;
inputting the time domain signal added with the training sequence into an interleaver, and interleaving the time domain signal to obtain a transmission signal;
performing digital-to-analog conversion on the transmission signal, and transmitting the transmission signal to a power line;
receiving the transmission signal at a receiving end, de-interleaving the transmission signal to obtain a receiving signal, and performing Fourier transform on the receiving signal to obtain a first frequency domain signal;
estimating a signal response based on the received training sequence; and equalizing the first frequency domain signal using the estimated signal response;
mapping the equalized first frequency domain signal into a second matrix block signal modulated by quadrature phase shift keying;
converting the second matrix block signal into a serial signal, and obtaining average power of noise in the serial signal;
acquiring a pulse noise detection threshold, and determining a noise threshold=the pulse noise detection threshold×average power; detecting the serial signal through a noise threshold to obtain impulse noise;
performing Fourier transformation on the impulse noise to obtain a second frequency domain signal, wherein the second frequency domain signal is the frequency domain signal of the impulse noise;
obtaining a noise-reduced frequency-domain signal, noise-reduced frequency-domain signal = first frequency-domain signal-second frequency-domain signal;
and performing inverse Fourier transform on the noise reduction frequency domain signal to obtain a noise reduction signal.
2. The noise reduction method suitable for power line carrier communication of claim 1, wherein the transmitting signal is distributed to a plurality of subcarriers by an orthogonal frequency division multiplexing technique at the transmitting end; at the receiving end, the signals on the plurality of sub-carriers are recovered into transmission signals by an orthogonal frequency division multiplexing technology.
3. A method of noise reduction for use in a power line carrier communication according to claim 1, wherein the method of interleaving the time domain signal comprises:
constructing an interleaver, wherein the interleaver consists of M column matrix blocks and L row matrix blocks;
an interleaver performance evaluation model is obtained,wherein q is a cumulative distribution function, epsilon is a spreading factor of the two-dimensional interleaver, Δt is a sampling time length, lambda is a pulse duration mean value, t is a pulse duration, and e is a natural constant;
setting an evaluation threshold F 0 And evaluating the performance of the constructed interleaver if F (t, lambda) < F 0 Judging that the performance of the interleaver is unqualified, and adjusting the value of L; if F (t, lambda) is greater than or equal to F 0 Continuously judging that the performance of the interleaver is qualified;
randomly interweaving a plurality of different OFDM symbol blocks, wherein the minimum interweaving distance is as followsWherein ω is a set constant greater than 0;
a plurality of OFDM symbol blocks on each subcarrier are cyclically shifted interleaved.
4. The method of noise reduction for power line carrier communication according to claim 1, wherein after obtaining the time domain signal of the first matrix block signal, each OFDM symbol in the time domain signal is preceded by a length L cp And updated to a new time domain signal S cp ＝Θ cp S H Wherein S is cp For the updated time domain signal, S H For the pre-update time domain signal Θ cp Is a mapping matrix;
after the receiving end obtains the received signal, the cyclic prefix of the received signal is removed, and then fourier transformation is performed to obtain a first frequency domain signal.
5. The method for noise reduction for power line carrier communication according to claim 1, wherein the method for obtaining average power of noise in the serial signal comprises:
converting serial signal to frequency domain R by fast Fourier transform n ：R n ＝S n +W n +I n Where n=0, 1,2, …, N-1, N is the number of data subcarriers; s is S n Is the frequency domain of the signal, W n Frequency domain of background noise, I n Is the frequency domain of impulse noise;
will frequency domain R n Inputting to hard decision module, placing pilot symbol at pilot subcarrier position, inserting zero at other positions, and demodulating according to QPSK modulation mode to obtain signal
Determining noise signal Z n ：Wherein D is n Is a serial signal;
performing inverse Fourier transform on the noise signal to obtain an estimated value d of the noise n ；
Average power E of noise is obtained:where M is the length of the noise signal.
6. The method for noise reduction for power line carrier communication according to claim 5, wherein the method for obtaining the impulse noise detection threshold comprises:wherein p is the interference rate of impulse noise, < >>For the received signal power without impulse noise occurrence, +.>Is the power of the received signal with impulse noise occurring.
7. A noise reduction method for use in a low voltage power line carrier communication as claimed in claim 6The method is characterized in that the pulse noise p is obtained by detecting the serial signal through a noise threshold n The method of (1) comprises:wherein d n The estimated value of the noise is that T is impulse noise detection threshold and E is average power of the noise.
8. A noise reducing terminal adapted for low voltage power line carrier communication, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the steps of the method according to any of claims 1-7 when the computer program is executed.
9. A computer readable storage medium storing a computer program, characterized in that the computer program when executed by a processor implements the steps of the method according to any of claims 1-7.
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