CN110519194A - Based on the phase noise inhibition method of Comb Pilot in OFDM data chain - Google Patents

Based on the phase noise inhibition method of Comb Pilot in OFDM data chain Download PDF

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CN110519194A
CN110519194A CN201910702700.8A CN201910702700A CN110519194A CN 110519194 A CN110519194 A CN 110519194A CN 201910702700 A CN201910702700 A CN 201910702700A CN 110519194 A CN110519194 A CN 110519194A
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phase noise
pilot
ofdm
phase
inhibition method
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CN110519194B (en
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闫朝星
罗翔
李辉
付林罡
李响
王先朋
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Aerospace Long March Launch Vehicle Technology Co Ltd
Beijing Institute of Telemetry Technology
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Aerospace Long March Launch Vehicle Technology Co Ltd
Beijing Institute of Telemetry Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03159—Arrangements for removing intersymbol interference operating in the frequency domain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Noise Elimination (AREA)

Abstract

The invention discloses the phase noise inhibition methods based on Comb Pilot in a kind of OFDM data chain, belong to digital wireless communication transmission technique field.This method utilizes the Comb Pilot of OFDM symbol, in demodulating end by weighted difference relevant calculation, obtains the clock drift amount estimated value in previous OFDM symbol, and eliminate each sub-carrier phase noise by linear fit.The present invention realizes between system when existing compared with great bell drift, effective inhibition to phase noise, can effectively promote the anti-phase of transceiver and make an uproar interference performance.

Description

Based on the phase noise inhibition method of Comb Pilot in OFDM data chain
Technical field
The present invention relates to digital wireless communication transmission technique fields, in particular to based on Comb Pilot in OFDM data chain Phase noise inhibition method.
Background technique
OFDM data chain transceiver is often applied to microminiature unmanned vehicle wideband data transmission system over the ground.It is made for low The phase noise performance of valence, modularization, the data terminal of miniaturization, used clock generation unit such as crystal is poor.It is right at this time Receiver can cause biggish performance loss.It needs to eliminate effect of phase noise using signal processing technology.
Patent " phase noise elimination method of ofdm system " (201310652815.3) is reflected for specific APSK constellation, is tied The noise power for closing each subcarrier is calculated phase noise coefficient, finally eliminates phase noise.Patent " OFDM receiver The middle method for eliminating the inter-sub-carrier interference as caused by phase noise " (200710071470.7) is extracted from subcarrier data Phase noise spectrum eliminates the interference between the subcarrier due to caused by phase noise.
" phase noise correcting algorithm in flight test telemetry system " (Wang Zhongjie, China's test, 2017,43 (6): 1-6) Channel estimation and compensation have been carried out to CP continuous pilot position, phase noise estimation and correction are carried out to common phase error."OFDM The influence and compensation of phase noise in system " (Gao Yujie, Xian Electronics Science and Technology University, 2007) uses a kind of Data Conjugate algorithm Eliminate the influence of phase noise.
But above-mentioned document carries out the elimination of common phase deviation for ofdm signal phase noise, or using noise spectrum point Analysis or self elimination method reduce the influence of phase noise, do not account for there is ofdm signal sampling time when compared with great bell drift between system The poor problem of frequency-region signal phase noise caused by shaking.
Summary of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide the phases based on Comb Pilot in OFDM data chain Noise suppressing method realizes between system effective inhibition to phase noise when existing compared with great bell drift.
Above-mentioned purpose of the invention is achieved by following technical solution:
Based on the phase noise inhibition method of Comb Pilot in OFDM data chain, steps are as follows:
Step (1), at OFDM data end modification end, OFDM symbol includes NsA sampling, the then total N of frequency domainsA subcarrier, NsThe power that value is 2, and 64≤Ns≤ 8192, OFDM data end modification end time domain data is expressed as x (n), 0≤n≤Ns- 1, modulated terminal frequency domain data is expressed as X (k), 0≤k≤Ns- 1, Comb Pilot Xp(m), 0≤m≤M-1；
In demodulating end, the theoretical time domain data after transmission is expressed as y (n), by the time domain of effect of phase noise Data be y (n- τ (n)), wherein τ (n) indicate nth data clock drift, in the same OFDM symbol, τ (n) variation compared with It is small, it is set as unified value τ；Y (k), Comb Pilot Y are expressed as in demodulating end frequency domain data after transmissionp(m)；
Step (2), in OFDM data terminal demodulating end, first carry out synchronization process, then eliminate receive frequency pilot sign in phase Position modulation intelligence, then by weighted difference relevant calculation, obtain the clock drift amount estimated value in previous OFDM symbol
Clock drift amount estimated value in step (3), the previous OFDM symbol obtained according to step (2)Linear fit Calculate NuThe corresponding phase theta (k) of a effective subcarrier, is converted to plural number for θ (k) and is multiplied with Y (k), completes phase noise It eliminates.
In step (1), frequency domain NsA subcarrier meets following situation:
A) effectively sub-carrier number is Nu, 1≤Nu≤Ns；
B) intermediate 1 sub-carrier values are 0；
c)NuThe both sides N of a effective subcarriers-NuIt is 0 that -1 sub-carrier values, which is all provided with,；
d)NuThere are M pilot tone, 1≤M≤N in a effective subcarrieru；
E) M pilot tone is uniformly distributed by interval of D, 1≤D≤Nu。
In step (2), by the frequency domain signal X of Comb Pilot and receiving end known pilotp(m) conjugate multiplication is eliminated and is received Phase-modulated information in frequency pilot sign, is expressed as
In step (2), it is weighted difference relevant calculation using following formula, obtains the clock in previous OFDM symbol Drift value estimated value
Wherein, R0To design difference gap length, w (d) is design weighting coefficient, and arg [] expression takes clock to float phase operation.
1≤R0≤M/2。
In step (2), phase theta (k) is obtained using following formula:
Two adjacent OFDM symbols, should be by selecting different M and D to design different pilot tone patterns.
Compared with prior art, the present invention has the following advantages:
(1) present invention is led for there is the case where compared with great bell drift between system according to the frequency domain pectination of modulated terminal OFDM symbol Frequently, the clock drift amount estimated value in OFDM symbol is obtained by weighted difference relevant calculation in demodulating end, then passes through Linear Quasi Conjunction obtains the corresponding phase of effective subcarrier, realizes effective inhibition to each sub-carrier phase noise.
(2) present invention utilizes the frequency domain Comb Pilot of OFDM symbol, obtains OFDM symbol by weighted difference relevant calculation Interior clock drift amount estimated value, demodulation performance are not influenced by adjacent OFDM symbol the amount of phase noise.
(3) present invention obtains the phase of the effective subcarrier of OFDM symbol by linear fit, and eliminates each subcarrier phase Position noise, the pilot tone pattern suitable for different pilot interval D.
(4) present invention design adjustable differential gap length can be adjusted for different size of phase noise, meet phase The design requirement of position estimation range and estimated accuracy.
Detailed description of the invention
Fig. 1 is phase noise inhibition method system block diagram and pilot patterns based on Comb Pilot in OFDM data chain of the present invention Sample；
Fig. 2 be OFDM data chain of the present invention in based on the phase noise inhibition method of Comb Pilot estimating at different SNR Count deviation mean value performance.
Fig. 3 be OFDM data chain of the present invention in based on the phase noise inhibition method of Comb Pilot estimating at different SNR Count deviation standard deviation performance.
Specific embodiment
The following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments:
Phase noise inhibition method based on Comb Pilot in OFDM data chain of the present invention, is led using the pectination of OFDM symbol Frequently, the clock drift amount estimated value in previous OFDM symbol is obtained, and pass through line by weighted difference relevant calculation in demodulating end Property fitting eliminate each sub-carrier phase noise, effectively promote the anti-phase of transceiver and make an uproar interference performance.
Based on the phase noise inhibition method of Comb Pilot in OFDM data chain, mainly include the following steps:
Step (1), at OFDM data end modification end, OFDM symbol includes NsA sampling, N in general data catenary systems The power that value is 2,64≤Ns≤ 8192, the total N of frequency domainsA subcarrier, in which:
A) effectively sub-carrier number is Nu, 1≤Nu≤Ns,
b)NsIn a subcarrier, 1 subcarrier (the i.e. N in centres/ 2) value be 0,
c)NuThe both sides N of a effective subcarriers-NuIt is 0 that -1 sub-carrier values, which is all provided with,
d)NuThere are M pilot tone, 1≤M≤N in a effective subcarrieru,
E) M pilot tone is uniformly distributed by interval of D, 1≤D≤Nu。
Contained pilot tone number M can not be identical in different OFDM symbols, and interval D can not also be identical, obtains different pilot patterns Sample.
OFDM data end modification end time domain data is expressed as x (n), 0≤n≤Ns-1.Modulated terminal frequency domain data is expressed as X (k), 0≤k≤Ns- 1, Comb Pilot Xp(m), 0≤m≤M-1.
In demodulating end, the theoretical time domain data after transmission is expressed as y (n).By the time domain of effect of phase noise Data be y (n- τ (n)), wherein τ (n) indicate nth data clock drift, between different OFDM symbols, τ (n) variation compared with Greatly, in the same OFDM symbol, τ (n) variation is smaller, is set as unified value τ.
Y (k), Comb Pilot Y are expressed as in demodulating end frequency domain data after transmissionp(m)。
Step (2), in OFDM data terminal demodulating end, after synchronization process, will be led known to Comb Pilot and receiving end The frequency domain signal X of frequencyp(m) conjugate multiplication is eliminated and receives phase-modulated information in frequency pilot sign, is expressed asThen by weighted difference relevant calculation, the clock drift amount obtained in previous OFDM symbol is estimated Evaluation
Wherein, R0To design difference gap length, 1≤R0≤ M/2,To design weighting coefficient, arg [] Expression takes clock to float phase operation, passes through 1 computation of table lookup of ROM table.
Clock drift amount estimated value in step (3), the previous OFDM symbol obtained according to step (2)Linear fit Calculate NuThe corresponding phase of a effective subcarrier:
It is tabled look-up ROM table 2 according to the phase theta (k) of effective subcarrier, θ (k) is converted into plural I (k)+jQ (k), and pass through It is multiplied with Y (k), completes phase noise and eliminate.
Embodiment
The performance of phase noise inhibition method based on Comb Pilot in OFDM data chain of the present invention is analyzed.
Fig. 1 is the phase noise inhibition method system block diagram and pilot tone pattern in OFDM data chain based on Comb Pilot.If Two kinds of pilot tone patterns are counted.NuHaving intermediate 1 carrier wave in+1 subcarrier is 0, and different pilot interval D-shapeds are at M=Np1、Np2Two kinds The pilot tone pattern of different pilot lengths.
If OFDM symbol has 1024 point FFT signals, 720 effective subcarriers form 10.8MHz band width in physical, wherein each OFDM symbol has 120 pilot sub-carriers, using the present invention program, using Np1、Np2Two kinds of pilot tone patterns alternately clock floats The estimation of shifting amount, emulation obtain ofdm signal caused by clock floats and mutually make an uproar in the clock drift amount estimated value of frequency domainEstimated bias is equal It is worth performance as shown in Fig. 2, standard deviation performance is as shown in figure 3,5000 statistical analysis of emulation.
For Fig. 2 estimated bias mean value, within the scope of effective signal-to-noise ratio SNR=5dB-20dB, emulation deviation mean value is 0. For SNR=5dB, work as R0When=32, clock drift amount estimated valueMaximum value is 0.0009, works as R0When=60, clock drift amount Estimated valueMaximum value is 0.00055.For SNR=20dB, work as R0When=32, clock drift amount estimated valueMaximum value is 0.00018, work as R0When=60, clock drift amount estimated valueMaximum value is 0.00016.
Analysis chart 3 estimates that standard deviation works as R for SNR=5dB0When=32,60, clock drift amount estimated valueStandard Deviation is respectively 0.00025,0.00016.For SNR=20dB, work as R0When=32,60, clock drift amount estimated valueStandard deviation Difference is respectively 5E-5,3E-5.
Clock drift amount can be effectively estimated by illustrating method provided by the invention, then can be eliminated by linear fit each Sub-carrier phase noise effectively promotes the anti-phase of transceiver and makes an uproar interference performance.
The above, optimal specific embodiment only of the invention, but scope of protection of the present invention is not limited thereto, In the technical scope disclosed by the present invention, any changes or substitutions that can be easily thought of by anyone skilled in the art, It should be covered by the protection scope of the present invention.
The content that description in the present invention is not described in detail belongs to the well-known technique of professional and technical personnel in the field.

Claims (8)

  1. Based on the phase noise inhibition method of Comb Pilot in 1.OFDM data-link, it is characterised in that steps are as follows:
    Step (1), at OFDM data end modification end, OFDM symbol includes NsA sampling, the then total N of frequency domainsA subcarrier, NsIt takes The power that value is 2, and 64≤Ns≤ 8192, OFDM data end modification end time domain data is expressed as x (n), 0≤n≤Ns- 1, it adjusts End frequency domain data processed is expressed as X (k), 0≤k≤Ns- 1, Comb Pilot Xp(m), 0≤m≤M-1；
    In demodulating end, the theoretical time domain data after transmission is expressed as y (n), by the time domain data of effect of phase noise For y (n- τ (n)), wherein τ (n) indicates the clock drift of nth data, and in the same OFDM symbol, τ (n) variation is smaller, It is set as unified value τ；Y (k), Comb Pilot Y are expressed as in demodulating end frequency domain data after transmissionp(m)；
    Step (2), in OFDM data terminal demodulating end, first carry out synchronization process, then eliminate receive frequency pilot sign in phase tune Information processed, then by weighted difference relevant calculation, obtain the clock drift amount estimated value in previous OFDM symbol
    Clock drift amount estimated value in step (3), the previous OFDM symbol obtained according to step (2)Linear fit calculates N outuThe corresponding phase theta (k) of a effective subcarrier, is converted to plural number for θ (k) and is multiplied with Y (k), completes phase noise and eliminates.
  2. 2. the phase noise inhibition method based on Comb Pilot in OFDM data chain according to claim 1, feature exist In, in step (1), frequency domain NsA subcarrier meets following situation:
    A) effectively sub-carrier number is Nu, 1≤Nu≤Ns；
    B) intermediate 1 sub-carrier values are 0；
    c)NuThe both sides N of a effective subcarriers-NuIt is 0 that -1 sub-carrier values, which is all provided with,；
    d)NuThere are M pilot tone, 1≤M≤N in a effective subcarrieru；
    E) M pilot tone is uniformly distributed by interval of D, 1≤D≤Nu。
  3. 3. the phase noise inhibition method based on Comb Pilot in OFDM data chain according to claim 2, feature exist In in step (2), by the frequency domain signal X of Comb Pilot and receiving end known pilotp(m) conjugate multiplication is eliminated and receives pilot tone Phase-modulated information in symbol, is expressed as
  4. 4. the phase noise inhibition method based on Comb Pilot in OFDM data chain according to claim 3, feature exist In in step (2), being weighted difference relevant calculation using following formula, obtain the clock drift amount in previous OFDM symbol Estimated value
    Wherein, R0To design difference gap length, w (d) is design weighting coefficient, and arg [] expression takes clock to float phase operation.
  5. 5. the phase noise inhibition method based on Comb Pilot in OFDM data chain according to claim 4, feature exist In 1≤R0≤M/2。
  6. 6. the phase noise inhibition method based on Comb Pilot in OFDM data chain according to claim 5, feature exist In,
  7. 7. the phase noise inhibition method based on Comb Pilot in OFDM data chain according to claim 2, feature exist In in step (2), phase theta (k) is obtained using following formula:
  8. 8. the phase noise inhibition method based on Comb Pilot in OFDM data chain according to claim 2, feature exist In two adjacent OFDM symbols should be by selecting different M and D to design different pilot tone patterns.
CN201910702700.8A 2019-07-31 2019-07-31 Phase noise suppression method based on comb-shaped pilot frequency in OFDM data chain Active CN110519194B (en)

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