CN109861726A - A kind of improved low pressure power line communication system channel estimation method - Google Patents
A kind of improved low pressure power line communication system channel estimation method Download PDFInfo
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- CN109861726A CN109861726A CN201910212458.6A CN201910212458A CN109861726A CN 109861726 A CN109861726 A CN 109861726A CN 201910212458 A CN201910212458 A CN 201910212458A CN 109861726 A CN109861726 A CN 109861726A
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Abstract
A kind of improved low pressure power line communication system channel estimation method.Algorithm follows following steps: obtaining the initial value of channel estimation by LS algorithmIt will using IDFTTime domain is transformed to obtainImpulsive noise is carried out to sample point outside cyclic prefix to filter out to obtain The all noise sample points of sample point outside middle cyclic prefix, whole zero setting；It is smoothed the sample point in the noise sample point and cyclic prefix outside cyclic prefix after removal impulsive noise to obtain noise threshold T；Noise filtering is carried out to the sample point in cyclic prefix using T and obtains the time domain expression h of final channel estimationDFT(n)；To hDFT(n) it carries out DFT and obtains the frequency domain presentation of channel estimation.This algorithm to cyclic prefix outside impulsive noise filtered out, solve the problems, such as because power line impulse noise interference cause threshold value thresholding setting it is excessive due to filter out useful sample point in cyclic prefix, improve the performance of channel estimation.
Description
Technical field
The present invention relates to fields of communication technology more particularly to a kind of improved low pressure power line communication system channel estimation to calculate
Method.
Background technique
Power line carrier communication (Power Line Communication, PLC) refers to the logical of power line transmission signals
Letter technology does not have to rearrange communication line, can substantially reduce logical because original powerline systems are utilized to communicate
Believe cost, but with being originally used for transmission electric energy and the power line arranged is communicated with regard to needing to face severe communication environment.It is orthogonal
Frequency Division Multiplexing system (OFDM) is a key technology for realizing broadband power line communication, this technology is utilized multiple mutually orthogonal
Subcarrier transmit information, not only substantially increase transmission rate, but also be effective against the frequency selection of power line channel
Property decline and multidiameter delay, improve transmission quality.
In order to fight the severe channel circumstance of power line channel, we use OFDM technology, and channel estimation is to OFDM system
Most important for system, the channel estimation method of ofdm system can be divided into following three classes: channel estimation, blind Channel based on pilot tone
Estimation and semi-blind channel estimation, the channel estimation based on implicit training sequence.For the channel estimation based on frequency pilot sign,
Blind Channel Estimation and the channel estimation methods based on implicit training sequence possess the higher availability of frequency spectrum, but the method needs to count
There is higher irrelevance according to sequence and pilot frequency sequence and computation complexity is higher, is not easy to Project Realization.
The channel estimation methods of pilot aided are because its computation complexity is low and what channel estimation errors were small is current reality
Most widely used a kind of channel estimation methods in engineering.The channel estimation methods of traditional pilot aided are that least square (LS) is estimated
Calculating method.LS algorithm for estimating is a kind of simplest channel estimation method, it only need to be with the pilot frequency sequence of receiving end divided by known
The pilot frequency sequence of transmitting terminal can be obtained by the impulse response estimated value of channel, but the method is not considered in channel
Influence of noise, and the noise interference of low voltage power line communication channel is more serious, therefore LS estimation is believed for low tension wire channel
The effect of road estimation is poor.Therefore related improvement has been made to it again on the basis of LS channel estimation method, propose and be based on
The channel estimation method of DFT improves channel estimation effect of the algorithm in the serious environment of noise jamming.
Paper " the Efficient EFT-based channel estimation for that Kang Y et al. is delivered at it
OFDM systems on multipath channels[J]”(IET communications,2007,1(2):197-202)
In propose using a kind of innovatory algorithm to traditional DFT channel estimation method, the algorithm it is assumed that noise energy entire
All be within channel under the premise of being uniformly distributed, using cyclic prefix outside noise component(s) set a threshold value, utilize this threshold value
The operation that sample point in cyclic prefix is denoised.But the threshold value thresholding does not consider useful sample in cyclic prefix
The Energy distribution of this point is easy to appear the excessive situation of threshold value thresholding, thus can be by some useful samples in cyclic prefix
Point carries out mistake and filters out.
Summary of the invention
It is an object of the invention to be the deficiency for above-mentioned existing DFT channel estimation method, proposing one kind can be with
Effectively weaken the channel estimation method based on DFT of impulse noise interference in low-voltage power line.
To achieve the goals above, present invention employs following technical solutions:
A kind of improved low pressure power line communication system channel estimation method, which comprises the steps of:
Step 1 carries out the available channel response of LS algorithm channel estimation to the OFDM symbol received in receiving end and estimates
Value
Step 2, to what is obtainedThe IDFT operation for carrying out N point, by channel response value by frequency-domain transform to time domain,
It obtainsWherein N is the number of channel sub-carrier；
Step 3, to time domain estimated value of channel impulse responseThe value given threshold of middle cyclic prefix outer portion carries out
Impulsive noise filters out to obtain
Step 4 works as LCP(L when≤n≤N-1CPFor circulating prefix-length),All noise sample points, do not contain
Channel information, under time domainIt carries out filtering processing of making an uproar；
Step 5 carries out the sample point in the noise sample point and cyclic prefix outside cyclic prefix after removal impulsive noise
Smoothing processing obtains noise threshold T；
Step 6 carries out noise filtering using threshold value T to the sample point in cyclic prefix.It will be in cyclic prefix
Less than the direct zero setting of the sample point of T, the channel estimation value h of time domain is obtainedDFT(n),0≤n≤N-1；
Step 7, to hDFT(n) it carries out DFT transform and obtains the channel estimation value of frequency domain:
Further, the channel estimation in frequency domain value obtained in step 2 using LS algorithmTime domain is obtained by IDFT
Channel estimation valueProcess are as follows:
Further, impulsive noise noise outside cyclic prefix is filtered out in step 3 are as follows:
M is outside cyclic prefix in formulaIntermediate value, λ be setting impulsive noise energy and background noise energy ratio
It is worth thresholding.
Further, outside in step 4 to cyclic prefixNoise filtering processing are as follows:
By the sample point whole zero setting outside cyclic prefix, and the sample point in cyclic prefix is constant.
Further, the threshold value thresholding T in cyclic prefix obtained in step 5 are as follows:
T=aT1+(1-a)T2
Wherein, a is smoothing factor, T1For average energy outside CP, T2For the average energy of sample point useful in CP.T1Table
Up to formula such as formula are as follows:
Wherein set B is that the set card (B) of the sample point after filtering out impulsive noise outside cyclic prefix is indicated in set B
Element number, i.e., after impulse noise component filters out outside cyclic prefix sample point number.
T2Expression formula are as follows:
In conclusion by adopting the above-described technical solution, the beneficial effects of the present invention are:
The OFDM channel estimation method that the invention proposes a kind of in low pressure power line communication system, to cyclic prefix outside
Noise sample point carried out impulsive noise first and filtered out, be then smoothed further according to the sample point inside and outside cyclic prefix
Obtain threshold value.It is excessive so as to cause effective sample point in cyclic prefix to avoid the setting of the threshold value as caused by impulse noise interference
The case where loss, improves the accuracy and stability of channel estimation.
Detailed description of the invention
Fig. 1 is the flow chart of channel estimation method of the present invention；
Fig. 2 is low-voltage power line OFDM baseband communication system flow chart.
Specific embodiment
Below with reference to low-voltage power line OFDM baseband communication system flow chart and channel estimation method attached drawing pair of the invention
The present invention is described further, it is clear that and described embodiments are only a part of the embodiments of the present invention,
Instead of all the embodiments.Based on the embodiments of the present invention, those of ordinary skill in the art are not making
All other embodiment obtained, shall fall within the protection scope of the present invention under the premise of creative work.
In transmitting terminal, baseband modulation is carried out to binary data sequence, obtains the baseband signal of frequency domain, tune used herein
Mode processed is QPSK.Number of sub carrier wave is set as N, obtains the road N parallel signal by going here and there and converting, the length of cyclic prefix is
LCP, for the frequency selective fading for resisting power line channel, the inserted mode of pilot tone is Block-type pilot, with time interval τ and completely
Sufficient Nyquist law insertion.Specific implementation step of the invention is as follows:
Step 1, the channel estimation initial value of frequency domain is obtained using LS algorithm
Wherein YpFor the pilot signal received at receiver, XPFor the pilot signal of known transmission, WPAt pilot tone
Noise frequency domain components.
Step 2, to the channel estimation initial value of obtained frequency domainIt carries out at IDFT (inverse discrete fourier transform)
Reason, willTime domain is transformed by frequency domain, is obtainedIn ofdm communication system, imitated to resist multipath in channel
Intersymbol interference caused by answering, we insert cyclic prefix in transmitting terminal, and the insertion of cyclic prefix causes inverse by Fourier
After transformation, the energy of actual data-signal is concentrated mainly on the sample point within circulating prefix-length, and in cyclic prefix
Except sample point on all noise energies of energy.
Step 3, due to containing various impulsive noises in low voltage power line communication channel, for the noise sample except cyclic prefix
Point setting thresholding carries out impulsive noise and filters out.
Step 4, to cyclic prefix outside sample point whole zero setting, the sample point in cyclic prefix is constant.
Step 5, in order to be filtered out to the noise in sample point in cyclic prefix, in cyclic prefix and removal pulse
Sample point outside the cyclic prefix of noise is smoothed, and obtains threshold value thresholding T.
Step 6, noise filtering is carried out to the sample point in cyclic prefix using threshold value thresholding T, when the energy of sample point is small
Then think that the sample point is noise when T, carries out zero-setting operation, other sample points remain unchanged.Obtain final channel estimation
The time domain of value expresses hDFT(n)。
Step 7, by hDFT(n) it carries out DFT (Discrete Fourier Transform) processing and obtains the frequency domain presentation H of channel estimationDFT
(k)。
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto,
Anyone skilled in the art in the technical scope disclosed by the present invention, according to the technique and scheme of the present invention and its
Inventive concept is subject to equivalent substitution or change, should be covered by the protection scope of the present invention.
Claims (3)
1. a kind of improved low pressure power line communication system channel estimation method, which comprises the steps of:
Step 1: the initial value of channel estimation is obtained using LS algorithm
Step 2: rightThe IDFT for carrying out N point converts to obtain the channel estimation initial value of time domainWherein N is channel
Number of sub carrier wave；
Step 3: outside to cyclic prefixSample point given threshold carry out impulsive noise filter out to obtain
Step 4: work as LCP(L when≤n≤N-1CPFor circulating prefix-length),All noise sample points, without useful
Channel information, under time domainIt carries out filtering processing of making an uproar；
Step 5 carries out the sample point in the noise sample point and cyclic prefix outside cyclic prefix after removal impulsive noise smooth
Processing obtains noise threshold T；
Step 6 carries out noise filtering using threshold value T to the sample point in cyclic prefix.It will be in cyclic prefixLess than T
The direct zero setting of sample point, obtain the channel estimation value h of time domainDFT(n),0≤n≤N-1；
Step 7, to hDFT(n) it carries out DFT transform and obtains the channel estimation value of frequency domain:
2. improved low pressure power line communication system channel estimation method according to claim 1, which is characterized in that step
In three to cyclic prefix outsideImpulsive noise filters out are as follows:
M is outside cyclic prefix in formulaIntermediate value, λ be setting impulsive noise energy and background noise energy ratio door
Limit.
3. improved low pressure power line communication system channel estimation method according to claim 1, which is characterized in that step
For the threshold value thresholding T of sample point in cyclic prefix obtained in five are as follows:
T=aT1+(1-a)T2
Wherein, a is smoothing factor, T1For average energy outside CP, T2For the average energy of sample point useful in CP.T1Expression formula
Such as formula are as follows:
Wherein set B is that the set card (B) of the sample point after filtering out impulsive noise outside cyclic prefix indicates the element in set B
Number, i.e., after impulse noise component filters out outside cyclic prefix sample point number.
T2Expression formula are as follows:
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| CN112702085A (en) * | 2021-03-22 | 2021-04-23 | 北京思凌科半导体技术有限公司 | Pulse noise estimation method, pulse noise estimation device, storage medium and electronic equipment |
| CN113595945A (en) * | 2021-08-04 | 2021-11-02 | 重庆邮电大学 | Channel estimation method suitable for PDSCH of 5G system |
| CN116389214A (en) * | 2023-06-05 | 2023-07-04 | 四川科冠电子有限公司 | Noise reduction method, noise reduction terminal and medium suitable for voltage power line carrier communication |
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| CN112702085A (en) * | 2021-03-22 | 2021-04-23 | 北京思凌科半导体技术有限公司 | Pulse noise estimation method, pulse noise estimation device, storage medium and electronic equipment |
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| CN113595945A (en) * | 2021-08-04 | 2021-11-02 | 重庆邮电大学 | Channel estimation method suitable for PDSCH of 5G system |
| CN116389214A (en) * | 2023-06-05 | 2023-07-04 | 四川科冠电子有限公司 | Noise reduction method, noise reduction terminal and medium suitable for voltage power line carrier communication |
| CN116389214B (en) * | 2023-06-05 | 2023-08-08 | 四川科冠电子有限公司 | Noise reduction method, noise reduction terminal and medium suitable for voltage power line carrier communication |
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