CN114221677A - Power line carrier modulation system and method based on channel state self-adaptive adjustment - Google Patents
Power line carrier modulation system and method based on channel state self-adaptive adjustment Download PDFInfo
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Abstract
The utility model belongs to the technical field of power communication, and provides a power line carrier modulation system based on channel state self-adaptive adjustment, which comprises a channel state acquisition module, a channel state visualization module and a carrier power distribution module for connecting the channel state acquisition module and the channel state visualization module; the channel state acquisition module is used for acquiring the channel state information of the power line and transmitting the channel state information to the carrier power distribution module; the carrier power distribution module is used for receiving and analyzing the received channel information, and performing power distribution on power line subcarriers by adopting a constraint water injection algorithm distribution strategy based on specific communication service quality based on an analysis result to obtain a power line carrier modulation mode; the channel state visualization module preliminarily judges the channel state according to the difference of the mapping relation between the modulation mode and the channel state, and realizes the self-adaptive adjustment of the power line carrier.
Description
Technical Field
The disclosure belongs to the technical field of power communication, and particularly relates to a power line carrier modulation system and method based on channel state self-adaptive adjustment.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The power line carrier communication is widely used in a power utilization information acquisition system of a power enterprise due to the characteristics of no need of additionally erecting a communication line and no maintenance; however, since the main function of the power line carrier line is used for transmitting electric energy, the transmission environment of the power channel is "different from the environment of a specially-erected communication line," which is mainly characterized in that the transmission environment of the power channel is influenced by load variation in the power transmission line, the branch node of the power transmission line and sudden random interference in the line, and the superposition of these interference factors will cause the communication performance of the power channel to be greatly reduced.
In the existing Power consumption information collection system, a High Speed Power Line Communication (HPLC) technology is widely used, which is based on an Orthogonal Frequency Division Multiplexing (OFDM) technology, and divides an available transmission band into a series of Orthogonal subcarriers by dividing the transmission band, modulates the subcarriers with information to be transmitted, and transmits the information to a receiving end by using the subcarriers. The modulation scheme can be divided into multiple modulation schemes such as BPSK, QPSK, 16QAM, 64QAM, etc., according to the amount of information carried by each symbol. In the information modulation process, because the noise immunity performance is different due to different modulation modes, different modulation modes can be selected for each subcarrier according to the quality of a transmission channel in general to ensure that the information transmitted each time is maximized.
Therefore, it is necessary to perform a study related to power line carrier modulation.
Disclosure of Invention
In order to solve the above problems, the present disclosure provides a power line carrier modulation system and method based on channel state adaptive adjustment, which adaptively adjust a modulation mode in a power line carrier module according to a channel state.
According to some embodiments, a first aspect of the present disclosure provides a power line carrier modulation system adaptively adjusted based on a channel state, which adopts the following technical solutions:
a power line carrier modulation system based on channel state self-adaptive adjustment comprises a channel state acquisition module, a channel state visualization module and a carrier power distribution module, wherein the carrier power distribution module is used for connecting the channel state acquisition module and the channel state visualization module;
the channel state acquisition module is used for acquiring the channel state information of the power line and transmitting the channel state information to the carrier power distribution module; the carrier power distribution module is used for receiving and analyzing the received channel information, and performing power distribution on power line subcarriers by adopting a constraint water injection algorithm distribution strategy based on specific communication service quality based on an analysis result to obtain a power line carrier modulation mode; the channel state visualization module preliminarily judges the channel state according to the difference of the mapping relation between the modulation mode and the channel state, and realizes the self-adaptive adjustment of the power line carrier.
As a further technical limitation, the channel state acquisition module comprises a coupling unit, a signal conditioning unit and an analog-to-digital conversion unit which are electrically connected in sequence; the coupling unit adopts a capacitive coupling circuit, and a band-pass filter circuit is arranged in the signal conditioning unit.
As a further technical limitation, the carrier power allocation module includes a control unit, a spectrum analysis unit and a power allocation unit which are electrically connected in sequence; the channel state visualization module comprises a time-frequency transformation unit, a training unit and a visualization unit which are electrically connected in sequence.
According to some embodiments, a second aspect of the present disclosure provides a power line carrier modulation method based on channel state adaptive adjustment, which adopts the following technical solutions:
a power line carrier modulation method based on channel state self-adaptive adjustment comprises the following steps:
acquiring power line channel state information;
according to the channel state information and a preset carrier power distribution model, power distribution of power line subcarriers is carried out to obtain a power line carrier modulation mode;
the quality of the channel state is preliminarily judged according to different mapping relations between the modulation mode and the channel state, and the self-adaptive adjustment of the power line carrier is realized;
the carrier power distribution model adopts a constraint water filling algorithm distribution strategy based on specific communication service quality.
As a further technical limitation, in the process of acquiring the channel state information of the power line, low-frequency noise signals and pseudo signals doped in the power carrier signals are filtered based on high-pass filtering, so that the attenuation of the power carrier signals is reduced, and the influence of linear amplitude-frequency characteristics and phase-frequency characteristics is reduced; and performing secondary filtering on the power carrier signal based on a Chebyshev I-type band-pass filter to remove power frequency harmonic waves and broadband noise.
Further, the power distribution process of the power line subcarrier includes: and carrying out spectrum analysis on the acquired power line channel state information, and carrying out power distribution on power line subcarriers by adopting a constraint water injection algorithm distribution strategy based on specific communication service quality based on an analysis result to obtain a power line carrier modulation mode.
Furthermore, the power line carrier modulation mode includes a multi-system quadrature amplitude modulation, a bi-phase shift keying modulation and a quad-phase shift keying modulation.
Further, the specific process of the spectrum analysis is as follows: the method comprises the steps of obtaining a frequency spectrogram of power line channel state information by utilizing Fourier transform, carrying out statistical analysis on attenuation characteristics of all frequency points in the frequency spectrogram, and distributing a high-order modulation scheme to the frequency points with better channel states and distributing a low-order modulation scheme to the frequency points with poorer channel states based on statistical analysis results.
Furthermore, the spectrograms of the power line channel state information corresponding to different power line carrier modulation modes have different energy images at different frequency points, and time-frequency transformation of the power line channel state information is required to better distinguish the modulation modes.
Further, aiming at different modulation modes, the corresponding power line carrier modulation mode is identified from the energy image according to different time-frequency images through the training of early-stage energy image identification based on the deep learning neural network, and the channel state is preliminarily judged.
Compared with the prior art, the beneficial effect of this disclosure is:
the modulation mode in the power line carrier module is adaptively adjusted according to the channel state, the modulation mode is mapped and displayed to users in an image form, and system operators can visually know the channel transmission environment conditions according to different modulated signal images.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Fig. 1 is a schematic structural diagram of a power line carrier modulation system adaptively adjusted based on a channel state in a first embodiment of the disclosure;
fig. 2 is a schematic structural diagram of a coupling unit in a first embodiment of the disclosure;
fig. 3 is a schematic diagram of a signal conditioning circuit according to a first embodiment of the disclosure;
fig. 4 is a schematic structural diagram of an analog-to-digital conversion unit in a first embodiment of the disclosure;
fig. 5 is a flowchart of a power line carrier modulation method based on channel state adaptive adjustment in the second embodiment of the disclosure;
fig. 6(a) is a frequency spectrum diagram of a double-sideband signal modulation method in the second embodiment of the disclosure;
fig. 6(b) is a frequency spectrum diagram of a single-sideband signal modulation method in the second embodiment of the disclosure;
FIG. 7 is a SSD structure diagram of an embedded attention mechanism in an embodiment two of the disclosure;
fig. 8 is a diagram of image recognition results in different modulation schemes in the second embodiment of the present disclosure.
The specific implementation mode is as follows:
the present disclosure is further described with reference to the following drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict.
Example one
The embodiment provides a power line carrier modulation system based on channel state adaptive adjustment.
As shown in fig. 1, the power line carrier modulation system based on channel state adaptive adjustment includes a channel state acquisition module, a carrier power distribution module, and a channel state visualization module; the specific settings of the modules are as follows:
1. channel state acquisition module
The channel state acquisition module comprises a coupling unit, a signal conditioning unit and an analog-to-digital conversion unit which are sequentially and electrically connected.
1.1 coupling Unit
Since the channel state information needs to be extracted from the power line and then transferred to the carrier power distribution module for spectrum analysis, the process involves acquiring the channel state information from the strong power line and then performing corresponding transformation, a dedicated signal coupling circuit needs to be designed to acquire the channel state in the power line.
In the present embodiment, the coupling circuit employs a capacitive coupling circuit as shown in fig. 2. Because the transmission performance of inductive coupling is poorer than that of capacitive coupling, the attenuation is large, and the coupling attenuation of a signal is 12dB through a coupling transformer through a test, a capacitive coupling circuit is adopted in the embodiment. As shown in fig. 2, one end of the high frequency Y capacitor C10 is connected to the low voltage power line access point, and the other end is connected to the coupling transformer T1. C10 and resistance R2 constitute first order high pass filter, filter low frequency noise signal and pseudo-signal that mix in the carrier signal, and such design does benefit to high frequency carrier signal and can high-fidelity pass through, reduces the decay of signal as far as possible, reduces the influence of linear amplitude frequency characteristic and phase frequency characteristic to signal transmission. The values of the resistor R2 and the capacitor C10 can be calculated according to the formula
Calculation is made, e.g. if the desired RC filter cut-off frequency is 150KHz, C10-0.0047 μ F and R2-187 Ω can be calculated by the formula. The main function of the coupling transformer T1 is to isolate strong or weak current, and also to balance the signal lines. The TVS is a transient suppression diode, prevents strong interference and voltage surge on a power grid, and protects circuit devices. R1 is the unloading resistance of C10, and is usually 10M Ω.
1.2 Signal Conditioning Unit
Usually, the output of the coupling circuit at the receiving end is also mixed with power frequency harmonic and broadband noise, and secondary filtering is required to be performed in order to better restore the carrier signal on the 2-30 MHz frequency band, and a signal conditioning unit is introduced. The indexes of the secondary filtering are that the upper passband and the lower passband are fch＝30MHz,fcl2MHz, attenuation in the passband not greater than 3dB, upper and lower cut-off frequencies fsh＝60MHz,fsl1MHz, stopband attenuation of as50dB, then Ω1＝2πfcl，Ω3＝2πfch，Ω2 2＝Ω1Ω3Because the order used by the Butterworth filter is more than that used by the Chebyshev under the same index performance, the circuit is more complex, the cost is higher, and the attenuation of the Chebyshev in the pass band or the stop band is equal ripple, the Chebyshev type I filter is selected as the band-pass filter, and the function of the filter satisfies the following conditions:
the circuit design parameters obtained from equation (1) show the signal conditioning circuit comprising a five-stage chebyshev i-band pass filter circuit as shown in fig. 3.
In fig. 3, the star-shaped diode voltage stabilizing circuit on the left side of the circuit has the function of suppressing differential mode spike signals between live wires and zero wires and common mode spike signals between the live wires and the ground wires and between the zero wires and the ground wires. For differential mode spikes, D2 and D3 may form a bi-directional voltage regulator tube; for common-mode peak signals, the star-shaped structure is equivalent to two bidirectional voltage-stabilizing tubes, and can effectively protect a band-pass filter network from differential mode and common-mode interference; r4 and R7 are isolation resistors of the parallel resonant network, R5 models the power line output impedance, and R7 models the coupling circuit output impedance. R5 and R7 are both 50 omega to satisfy impedance matching; on the right side of the bandpass filter network, the zener diodes D4 and D5 form a bidirectional amplitude limiting circuit to prevent the subsequent signal decoding circuit from being damaged by too large signal amplitude.
1.3 analog-to-digital conversion unit
In order to realize the transmission of the acquired state information of the power line channel, in this embodiment, 10-precision TLC1543 produced by the american TI company is used as an analog-to-digital conversion unit of the hardware acquisition device, the converter is a 20-pin DIP package and a switched capacitor successive comparison type analog-to-digital converter, and an SPI serial communication interface is used, so that the converter has the characteristics of multiple input channels and high cost performance, and specific technical parameters are shown in table 1:
TABLE 1 technical indices of TLC1543 chips
The communication process of the A/D chip and the carrier power distribution module is as follows: the A/D chip is firstly defined as a slave chip, and a CPU in the carrier power distribution module is defined as a master chip. The master chip and the slave chip are connected through an SPI 4 wire serial bus, and REF + and REF-are positive and negative ends of reference voltage and are usually connected with a power supply and a ground; the AIN 0-AIN 7 access analog signals as sampling ports;
and if the chip is selected, the low level is effective, the EOC port is a conversion end indicating port, and the output high level indicates that the conversion is finished. Therefore, the working process is as follows: the clock pin of the slave chip is connected with the clock pin of the master chip, the system clock is provided by the clock, when the master chip selects the slave chip, the system clock is
Effectively, the counter resets and controls the enable 16-18 ports, the chip starts to convert data, then the main chip provides 2-bit channel address for IN (17 ports), voltage and current signals IN a line are collected, a sampling retainer is gated, simultaneously a clock sequence is input into the clock (18 ports), the main chip receives a conversion result sent from an OUT (16 port) end of the main chip, and one-time analog value sampling is completed>Conversion to digital quantities>And outputting the digital quantity.
In order to facilitate the capacity expansion of the system in the later stage, in this embodiment, there are 8 analog input ports and 8 input protection circuits. The first 4 paths are 0-10V direct current input, the COM5 port is a common grounding end, the second 4 paths are 0-20 mA direct current input, and the common grounding end is COM 6. An analog input port AI 01-AI 08 with 8 paths is designed, the analog input port AI 01-AI 08 is connected with an ADC 0-ADC 7 interface of an AD chip after passing through a filter protection circuit and is transmitted to a CPU of a carrier power distribution module through a 16-port OUT, and a connection circuit of an analog-to-digital conversion unit is shown in fig. 4: analog input port circuit wherein the upper left corner is analog signal input to filter protection circuit, and filter protection circuit comprises diode, resistance and electric capacity, adds diode and electric capacity and is in order to prevent that the transient voltage when switching in the analog from too big punctures AD chip and filters and switch in the analog burr.
2. Carrier power distribution module
The carrier power distribution module comprises a control unit, a spectrum analysis unit and a power distribution unit.
2.1 control Unit
The control unit has the main functions of completing the acquisition and analysis of channel data and distributing the power of the sub-carriers according to the frequency spectrum analysis result so as to achieve the purposes of maximum channel capacity and best transmission quality. The processor type of the control unit can be selected according to the amount of processing tasks required, and common alternatives include a microcomputer control unit based on a CPU, a control unit based on a cloud platform and an embedded system based on a single chip microcomputer or a DSP chip.
2.2 Spectrum analysis Unit
The spectrum analysis mainly refers to obtaining a spectrogram by utilizing Fourier transform, then carrying out statistical analysis on the attenuation characteristics of each frequency point, and on the basis of an analysis result, following a frequency point with a better channel state to allocate a high-order modulation scheme, and a frequency point with a worse channel state to allocate a low-order modulation scheme, so as to complete the modulation mode configuration and transmission power allocation on each subcarrier.
In this embodiment, considering that the main function of this embodiment is to implement optimal allocation of carrier power according to the state of a channel, and the requirement on computation amount and real-time performance is not high, the control unit and the spectrum analysis unit are combined into one, and a DSP is selected, because the chip is implemented by hardware with spectrum analysis (FFT (fast fourier transform)), so that spectrum analysis of the state of the channel can be implemented quickly. Therefore, in the embodiment of the present invention, the selection of the DSP chip may be preferably selected from the TMS320C5000 series of the american TI company, such as TMS320C54x, TMS320C54xx, TMS320C55x, and the functions described in the embodiment can be implemented as long as the DSP chip is selected.
2.3 Power distribution Unit
The scheduling of data to be transmitted in different frequency bands for transmission based on the control unit is a software implementation.
3. Channel state visualization module
The channel visualization module is essentially a display module, namely, a power grid manager uses a display platform (such as a computer) to visually check power line signals; the channel state visualization module comprises a time-frequency transformation unit, a training unit and a visualization unit.
Example two
The embodiment introduces a power line carrier modulation method based on channel state adaptive adjustment, and adopts the power line carrier modulation system based on channel state adaptive adjustment introduced in the first embodiment.
As shown in fig. 5, a power line carrier modulation method based on channel state adaptive adjustment includes the following steps:
acquiring power line channel state information;
according to the channel state information and a preset carrier power distribution model, power distribution of power line subcarriers is carried out to obtain a power line carrier modulation mode;
the quality of the channel state is preliminarily judged according to different mapping relations between the modulation mode and the channel state, and the self-adaptive adjustment of the power line carrier is realized;
the carrier power distribution model adopts a constraint water filling algorithm distribution strategy based on specific communication service quality.
The present embodiment develops detailed description on the process of power allocation of power line subcarriers:
the channel capacity of a communication system refers to the maximum average information rate that a channel can transmit without error. According to the Shannon formula, the channel capacity is
Wherein C represents the limit value of the data rate and the unit bit/s; b is expressed as the channel bandwidth in Hz; s denotes signal power (watts) and N denotes noise power (watts).
Under the interference of the thermal noise of the power line and the impedance characteristic of the access load, the signal-to-noise ratio (SNR) of a transmission signal usually has significant variation in a transmission bandwidth and is not constant, so that the classical Shannon formula is not suitable for the power line channel. Considering that the power of the carrier signal coupled to the power channel is generally limited, the channel capacity can be expressed by equation (3):
wherein S (f) | H (f) & gtdoes not pass through2X p (f), s (f) -received signal power spectrum, h (f) -channel transfer function, n (f) -noise power spectrum, p (f) -input signal power spectrum. H (f) and n (f) are inherent characteristics of the power line channel, then the solution for channel capacity C can be translated into an optimized allocation of the input signal power spectrum p (f).
In the operation of the actual carrier communication module, in order to ensure that each module operates within the allowable safe operating range, the input power of the carrier signal transmitter to the power line channel needs to be constrained, so that the carrier communication module is prevented from operating in a high-power state for a long time, and the probability of failure caused by overhigh power consumption is increased. In this embodiment, for the power allocation problem, an allocation algorithm combining a water injection method and a Quality of Service (Qos) for communication is adopted, and a constrained water injection algorithm allocation policy based on a specific Qos policy is proposed with a lower system error rate as a communication threshold, so as to maximize the PLC channel capacity, which mainly includes the following steps:
1. assuming that the referenced low-voltage power-line channel is divided into M narrow-band flat-fading sub-channels with a span of Δ f, the capacity of each sub-channel
Wherein, PjIs the allocated power of the jth sub-channel, HjIs the frequency response of the jth sub-channel, NjIs the noise power of the jth sub-channel. Discretized total channel capacity
And also
Pj>0，PinIs the total input power of the PLC channel.
2. Let Mj，Sj，PejRespectively representing the modulation order, the signal-to-noise ratio and the bit error rate of the j sub-channel input signal, and satisfying the following conditions:
Sj＝F(Pej,Mj) (4)
wherein M isj＝2qQ is the number of transmit bits and q is 1,2, 3.
3. Threshold value phi for defining bit error rate is 10-6Indicating the QoS allowed by the power line carrier communication system.
4. Order to
To PjCalculating deviation and guiding order
To obtain
From Pj>When the number of the first and second pixels is 0,
5. setting subchannel power allocation limit psijAnd psij>0, on the premise of meeting the QoS, finding the maximum available MΦjValue, then S is obtainedΦjThen, the power P allocated to the jth sub-channel is calculated by formula (4)Φj。
6. When the power P allocated to certain sub-channelsΦj>ψjLet the residual power Δ pj＝PΦj-ψj，PΦj＝ψj(ii) a When 0 is present<PΦj≤ψjWhen so, its value is retained; when P is presentΦj<When 0, let PΦjAnd closes the subchannel.
7. The residual power of the jth sub-channel is distributed into the (j + 1) th sub-channel, i.e. PΦ(j+1)＝PΦ(j+1)+ΔpjRepeating the steps 5 and 6, and repeating the iteration until the distributed power on all the sub-channels meets 0<PΦj≤ψj。
8. In satisfying
On the premise of (2), iteratively adjusting psijAnd calculates P at that timeΦjUp to
Infinitely approaching Pin. Will PΦjSubstituting into formula (7) to obtain ginsengNumber of
9. Substituting the formula (8) into the formula (6) can obtain a closed expression for maximizing the channel capacity:
as shown in formula (9), PΦj、SΦjAs can be derived from step 8, the subchannel noise power NjRemains substantially constant over deltaf, then the subchannel gain function HjIs influencing CmaxThe first factor of change. According to the formula (2), the number N of multipath branches and the length d of the multipath branches of the low-voltage power line channeliAnd attenuation caused by power line access load impedance can cause HjIs varied in a non-linear manner. According to simulation of multiple test results, in order to increase the capacity of a channel, the algorithm described in this embodiment can achieve an optimal effect under the following environmental conditions:
the distance between power communication equipment is suitably shortened, the design of a signal coupling circuit is optimized, and a bypass filter is installed at a distribution line, a 220V wall socket and the like. And selecting the power cable with less branches and no access load as a communication channel as possible. If necessary, an optimization device can be used to change the load characteristics of the tail end of the indoor power cable, and a coil capable of improving impedance is inserted in series at the front end of the electric equipment. Capacitive load is converted into resistive load as much as possible, so that attenuation and interference of power grid electric equipment to carrier signals are reduced.
In the power algorithm step 5, the maximum available modulation order of each subchannel input signal needs to be determined, the higher the modulation order is, the greater the bit error rate at the receiving end thereof is, and common modulation modes in power line carrier communication include Multilevel Quadrature Amplitude Modulation (MQAM), Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK). For each modulation mode, under the condition of an ideal channel, the corresponding bit error rate is as follows: if it is
Wherein M is 2qAnd q is the number of transmission bits.
Let the error function be
The inverse function defined as y ═ erf (x) is x ═ ζ (y), then
The transmission bit number under the MQAM modulation mode is converted by the formula (10) and the formula (11)
Sending bit number q and bit error rate P of signals in low-voltage PLC channeleMQAMAverage signal-to-noise ratio P/N of sum signaloIn relation to the sub-channel to which power has been allocated, the modulation scheme can be calculated according to the formula (13) under the condition that the bit error rate requirement is certain
Where ent (x) is the largest integer less than x.
When q is less than 1, the channel environment is bad, q is made to be 0, and the subchannel is closed;
when q is 1, selecting BPSK modulation; when 1< q <3, selecting q as 2, and selecting QPSK modulation;
when q is more than or equal to 3 and less than 5, selecting q to be 4, and selecting 16QAM modulation;
and when q is more than or equal to 5, taking q to be 6, and selecting 64QAM modulation.
The OFDM self-adaptive bit modulation method can effectively avoid the conditions of signal error rate increase, signal to noise ratio reduction, error rejection of sub-channels capable of transmitting a small amount of data and the like caused by the severe communication environment of a PLC channel, and improves the transmission bit number and the communication rate of signals while retaining the original carrier signal information to the maximum extent.
The following detailed description is made for visualization of channel states:
as can be known from the foregoing power allocation and modulation scheme allocation methods, the modulation scheme is actually an indirect mapping of the channel state, the high-order modulation scheme (e.g., 16QAM or 64QAM) is suitable for better channel conditions, and the low-order modulation scheme (BPSK or QPSK) is suitable for application scenarios with worse channel states. Therefore, if the modulation mode of the transmitted signal or the received signal can be visually identified every time, the quality of the channel state can be preliminarily judged according to the mapping mode of the modulation mode and the channel state, and a decision basis is provided for the management of a subsequent acquisition mode. Based on the above consideration, the present embodiment invents a method for visualizing a channel state based on a modulation mode on the basis of completing adaptive power allocation and modulation allocation.
Due to different modulation modes, different points are that energy distribution is inconsistent at different frequency points, and the representation of the energies in the frequency domain is that at different frequency points, the corresponding energy colors are different, such as a common measured double sideband signal (as shown in fig. 6 (a)) and a single sideband signal (as shown in fig. 6 (b)).
As can be seen from the spectrograms in fig. 6(a) and fig. 6(b), the energy images of different modulation modes at different frequency points are different in appearance, and these different spectral images provide a basis for distinguishing the modulation modes.
In this embodiment, the time-frequency transform is implemented by selecting a continuous wavelet transform. The continuous wavelet transform is shown in equation (14):
in the formula, the time domain signal x (t) and a wavelet function with good local properties in both time and frequency domains
The inner product operation is performed to extract the spectrum characteristics at different time instants. Wherein
Referred to as mother wavelets; a is a scaling factor; b is obtained by translation and expansion of translation factor psi (t)
Referred to as the wavelet basis function,
is psiab(t) conjugation.
Continuous wavelet transform projects the time domain signal x (t) onto a two-dimensional plane of time-scale, obtaining continuous wavelet transform coefficients. The coefficients reflect the degree of similarity of the signal to be analyzed to the wavelet function, with greater wavelet coefficients giving greater degrees of similarity, and vice versa.
The deep learning neural network is widely applied to image recognition in recent years, and the main working principle of the deep learning network is to complete parameter training in the deep learning network by learning a large number of image features, and then to recognize a new image by using a trained deep neural model. The deep neural network training process in this embodiment is as follows:
1. firstly, a communication module of a concentrator or a copy controller is utilized, and a special software of the communication module is utilized to generate a modulation signal with specific power according to the communication specification of a carrier product; then, a signal generator is used for generating noise which changes in a range of [0,85dB ] (the upper attenuation limit is selected to be 85dB according to the anti-noise performance of a carrier module specified by a state gateway in a broadband power line carrier interconnection and intercommunication specification), the noise attenuation is 0.001dB (the accuracy which can be identified by a measuring instrument is one thousandth), then the signals are coupled into a power line through the system provided in the first embodiment, and at the other end, a channel state collector is used for collecting modulation signals mixed with the noise and sending the modulation signals into a computer to be processed.
2. The computer converts the received mixed signals into time-frequency images by using a time-frequency processing algorithm and finishes the labeling work of the time-frequency images, wherein the purpose of the labeling work is to provide correct reference basis for training the deep neural network;
3. dividing the marked mixed signal image according to the proportion of 7:3 to form a training set and a testing set of the deep neural network;
4. and selecting a deep network learning frame, and completing the pre-training of the deep learning network by using a transfer learning mode.
In this embodiment, in order to improve the recognition accuracy of the deep neural network, a structure of a deep learning network ssd (single shot multi box detector) embedded with an attention mechanism shown in fig. 7 is selected; in the structure, an attention mechanism is added among conv3- > conv4 and conv7- > conv8- > conv9- > conv10- > conv11 in an original SSD deep learning network structure, the feature map is detected and a default box is extracted by the last layer of convolution, and the extraction of the default box is configured according to data in the following table 2;
5. on the basis of the arrangement of the network structure, training the improved deep neural network is completed by utilizing the generated training set, and then the trained deep neural network structure is tested by utilizing the test set;
6. finally, the tested deep neural network structure is used for carrying out modulation identification on the received mixed signals; a visual interface as shown in fig. 8 is formed, and a user can realize preliminary judgment of the channel state by combining the former contents according to the modulation mode of the interface, so that a basis is provided for subsequent acquisition strategy formulation.
Based on the recognition result in fig. 8, it is possible to obtain: aiming at different modulation modes, through the training of early-stage image recognition, the deep learning neural network can recognize the modulation mode of the signal from the image according to the difference of time-frequency images and display the signal to a user in an image mode, and the user can preliminarily judge the state of the channel according to the modulation mode recognized by the image by combining the previous description of the embodiment and provide a basis for the subsequent establishment of an acquisition strategy.
TABLE 2 Default Box sizes for layers
Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.
Claims (10)
1. A power line carrier modulation system based on channel state self-adaptive adjustment is characterized by comprising a channel state acquisition module, a channel state visualization module and a carrier power distribution module for connecting the channel state acquisition module and the channel state visualization module;
the channel state acquisition module is used for acquiring the channel state information of the power line and transmitting the channel state information to the carrier power distribution module; the carrier power distribution module is used for receiving and carrying out spectrum analysis on the received channel information, and carrying out power distribution on power line subcarriers by adopting a constraint water injection algorithm distribution strategy based on specific communication service quality based on an analysis result to obtain a power line carrier modulation mode; the channel state visualization module preliminarily judges the channel state according to different mapping relations between the modulation mode and the channel state, and realizes the self-adaptive adjustment of the power line carrier.
2. The power line carrier modulation system based on channel state adaptive adjustment as claimed in claim 1, wherein the channel state acquisition module comprises a coupling unit, a signal conditioning unit and an analog-to-digital conversion unit which are electrically connected in sequence; the coupling unit adopts a capacitive coupling circuit, and a band-pass filter circuit is arranged in the signal conditioning unit.
3. The power line carrier modulation system for adaptive adjustment based on channel status as claimed in claim 1, wherein the carrier power allocation module comprises a control unit, a spectrum analysis unit and a power allocation unit which are electrically connected in sequence; the channel state visualization module comprises a time-frequency transformation unit, a training unit and a visualization unit which are electrically connected in sequence.
4. A power line carrier modulation method based on channel state self-adaptive adjustment is characterized by comprising the following steps:
acquiring power line channel state information;
according to the channel state information and a preset carrier power distribution model, power distribution of power line subcarriers is carried out to obtain a power line carrier modulation mode;
based on the difference of the mapping relation between the modulation mode and the channel state, the channel state is preliminarily judged, and the self-adaptive adjustment of the power line carrier is realized;
the carrier power distribution model adopts a constraint water filling algorithm distribution strategy based on specific communication service quality.
5. The power line carrier modulation method based on channel state adaptive adjustment as recited in claim 4, wherein in the process of obtaining the channel state information of the power line, low-frequency noise signals and pseudo signals doped in the power line carrier signals are filtered based on high-pass filtering, so that the attenuation of the power line carrier signals is reduced, and the influence of linear amplitude-frequency characteristics and phase-frequency characteristics is reduced; and performing secondary filtering on the power carrier signal based on a Chebyshev I-type band-pass filter to remove power frequency harmonic waves and broadband noise.
6. The method as claimed in claim 5, wherein the power distribution of the power line sub-carriers comprises: and carrying out spectrum analysis on the acquired power line channel state information, and carrying out power distribution on power line subcarriers by adopting a constraint water injection algorithm distribution strategy based on specific communication service quality based on an analysis result to obtain a power line carrier modulation mode.
7. The power line carrier modulation method based on channel state adaptive adjustment as claimed in claim 6, wherein the power line carrier modulation modes include multilevel quadrature amplitude modulation, biphase shift keying modulation, and quadrature phase shift keying modulation.
8. The power line carrier modulation method based on channel state adaptive adjustment as claimed in claim 6, wherein the specific process of the spectrum analysis is: the method comprises the steps of obtaining a frequency spectrogram of power line channel state information by utilizing Fourier transform, carrying out statistical analysis on attenuation characteristics of all frequency points in the frequency spectrogram, and distributing a high-order modulation scheme to the frequency points with better channel states and distributing a low-order modulation scheme to the frequency points with poorer channel states based on statistical analysis results.
9. The method as claimed in claim 8, wherein the power line carrier modulation method based on the channel state adaptive adjustment is characterized in that the spectral diagrams of the power line channel state information corresponding to different power line carrier modulation modes are different in energy images at different frequency points, and the time-frequency transformation of the power line channel state information is required to better distinguish the modulation modes.
10. The method as claimed in claim 9, wherein for different modulation modes, the deep learning neural network based training through early energy image recognition identifies the corresponding power line carrier modulation mode from the energy image according to the difference of the time-frequency images, and preliminarily determines the channel state.
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