CN106888178B - A kind of OFDM/OQAM system channel estimation method - Google Patents
A kind of OFDM/OQAM system channel estimation method Download PDFInfo
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- CN106888178B CN106888178B CN201710195488.1A CN201710195488A CN106888178B CN 106888178 B CN106888178 B CN 106888178B CN 201710195488 A CN201710195488 A CN 201710195488A CN 106888178 B CN106888178 B CN 106888178B
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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
- H04L25/0202—Channel estimation
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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
- H04L25/0202—Channel estimation
- H04L25/0212—Channel estimation of impulse response
- H04L25/0218—Channel estimation of impulse response with detection of nulls
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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
- H04L25/0202—Channel estimation
- H04L25/022—Channel estimation of frequency response
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
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Abstract
The present invention discloses a kind of OFDM/OQAM system channel estimation method, on the basis of the FDA algorithm based on Block-type pilot, first obtains channel frequency domain responseSince time domain upper signal channel energy is concentrated mainly on limited sampled point, progress interference region zero-setting operation on IFFT operation transform to time domain is passed it through, FFT operation is then carried out again and obtains final frequency domain responseThis method will only exist interchannel noise and the solid noisy a large amount of time domain sampling points of system carry out zero-setting operation, it further reduced the influence interfered to precision of channel estimation, higher estimated accuracy is obtained, guarantees the error performance for improving OFDM/OQAM system in the case where certain complexity.
Description
Technical field
The present invention relates to fields of communication technology, and in particular to a kind of OFDM/OQAM system channel estimation method.
Background technique
As one of 5G physical layer Alternative modulation scheme, the orthogonal frequency division multiplexing (offset based on staggeredly orthogonal modulation
Quadrature modulation based orthogonal frequency division multiplexing, OFDM/
OQAM) technology receives the more and more extensive concern of academia.Compared with traditional ofdm system, OFDM/OQAM has following spy
Point and advantage: the energy of first, OFDM/OQAM pulse can be concentrated well in time domain and frequency domain, therefore system no longer needs
Cyclic prefix (cyclic prefix, CP) improves the spectrum efficiency and effective transmission power of communication system as protection；The
Two, orthogonality condition is relaxed by complex field strict orthogonal as real number field strict orthogonal, it is good to have simultaneously in time domain and frequency domain
The prototype pulse bandwidth filtering introducing of focus characteristics provides condition, therefore OFDM/OQAM system has both well under conditions of no CP
Anti- ISI and ICI ability.
The performance of wireless communication system is largely influenced by wireless channel, so that between transmitter and receiver
Propagation path it is extremely complex.Wireless channel unlike wire channel is fixed and it is foreseeable that but there is very big randomness, this
Very big challenge just is proposed to the design of receiver.It needs to estimate channel in the relevant detection of ofdm system, believe
The precision of road estimation will directly affect the performance of whole system.
Since the channel estimation methods of CP-OFDM system can not be directly applied in OFDM/OQAM system, some documents
(interference cancellation method, ICM) is eliminated from interference respectively and interference utilizes (interference
Approximation method, IAM) the two thinkings study pilot tone, propose corresponding pilot configuration.IAM
The a part of method by interference as pilot tone reduces intrinsic interference by being inserted into zero frequency pilot sign in pilot configuration, such
Algorithm improves the equivalent power of frequency pilot sign, so as to improve channel estimating performance.However pilot configuration needs 3-5 real value symbol
Number requirement reduce the spectrum efficiency of system.Premise using such algorithm is that the value of the time-frequency lattice point around pilot point is true
Fixed, so being generally used Block-type pilot structure.ICM method will be interfered to be eliminated from reception symbol, due to wrapping around pilot tone
Containing unknown data symbol, such algorithm needs pre- judgement and iteration to eliminate interference, increases the complexity of system realization.This
Class algorithm generally uses Block-type pilot and dotted pilot configuration.
In addition, above-mentioned channel estimation method also has ignored a fact, i.e., for equal interval sampling channel, channel impulse is rung
The energy of (channel impulse response, CIR) is answered to be concentrated mainly on the time domain sampling point of channel length in the time domain
On, other sampled points can be regarded as OFDM/OQAM system and inherently interfere and the stack power of noise.
Summary of the invention
To be solved by this invention is to eliminate OFDM/ using traditional channel estimation method under OFDM/OQAM system
OQAM system is inherently interfered and system error performance undesirable problem when noise, provides a kind of OFDM/OQAM system channel and estimates
Meter method.
To solve the above problems, the present invention is achieved by the following technical solutions:
A kind of OFDM/OQAM system channel estimation method, includes the following steps:
Step 1. generates frequency domain information source data, and obtains complex data after carrying out orthogonal QAM mapping to it；
Step 2. is periodically inserted block-like pilot configuration between the front end and data of complex data；Wherein lead for every piece
Frequency structure includes three column frequency pilot signs, and first row and third column are set as complete zero, and secondary series is then maximum according to pilot tone equivalent power
Change principle be designed as 1, j, -1,-j, 1, j, -1,-j ... }；
Step 3. carries out channel using frequency domain averaging method according to a preliminary estimate, to obtain channel frequency domain response；
Step 4. is operated by inverse Fourier transform, and channel frequency domain response is transformed into channel impulse response；
Step 5. retains the energy for the subcarrier that channel impulse response sub-carriers number is [0, L-1], and by channel impulse
The energy zero setting for responding the subcarrier that sub-carriers number is [L, M-1], obtains estimating required channel impulse response；Wherein L is
Channel length, M are the sum of channel impulse response sub-carriers；
Step 6. becomes channel impulse response needed for estimation to estimate required channel frequency by Fourier transform operation
Domain response, the channel frequency domain response are estimated final channel frequency domain response.
In above scheme, the sum M of subcarrier is equal to the line number of frequency domain information source data.
In above scheme, channel length L is equal to maximum delay in each diameter of channel and extends divided by the sampling interval.
In above scheme, the line number Yu step 1 frequency domain information source data of three column frequency pilot signs of pilot configuration in step 2
Line number is identical.
In above scheme, the frequency domain information source data generated in step 1 are 2048 rows, 1000 column.
In above scheme, in step 2, by every 5 column insertion one piece of pilot configuration i.e. three column pilot tones between complex data
Symbol.
The present invention carries out zero-setting operation by that will only exist interchannel noise and the solid noisy a large amount of time domain sampling points of system,
It is averaged on (frequency domain averaging, FDA) algorithm in original frequency domain and further decreases interference to channel estimation
The influence of precision improves the precision and OFDM/OQAM system of channel estimation on the basis of not influencing Project Realization complexity
Error performance.It is that one kind does not influence resource consumption, improves system in Project Realization compared with traditional LS algorithm, FDA algorithm
The channel estimation method of system error performance.
Detailed description of the invention
Fig. 1 is that OFDM/OQAM system realizes block diagram.
Fig. 2 is FDA-FFT channel estimation method module frame chart in OFDM/OQAM system.
Fig. 3 is that sub-carrier number is 2048, the OFDM/OQAM system different Q AM that symbolic number is 1000 modulate lower LS, FDA,
FDA-FFT channel estimation method MSE performance.
Fig. 4 is that sub-carrier number is 2048, the OFDM/OQAM system different Q AM modulation that symbolic number is 1000 it is lower using LS,
The system error performance that FDA, FDA-FFT channel estimation method obtain.
Specific embodiment
Method of the invention is further elaborated with specific embodiment with reference to the accompanying drawing:
For traditional FDA algorithm based on Block-type pilot and IAM-C pilot configuration, the design pilot structures meter on frequency domain
Calculate channel frequency domain response.It is weighted and averaged to obtain more accurate channel frequency domain response by the channel frequency domain response to design pilot tone
(channel frequency response, CFR).IAM-C design pilot structures are added in the front end for sending data first, with
It is inserted into Block-type pilot symbol period in transmission data afterwards.Therefore, channel response can be calculated by traditional pilot channel estimation
Method obtains, and then is averaging to obtain more accurate channel frequency domain response by the channel frequency domain response to design pilot tone.
Based on set forth above, it is assumed that the columns of Block-type pilot symbol is N, pm,nRepresent m-th of subcarrier of nth symbol
On transmission pilot tone, pm,n' reception pilot tone on m-th of subcarrier of nth symbol is represented,Represent the letter of m-th of subcarrier
Estimate parameter in road.Then the expression formula of channel estimation can indicate are as follows:
It is above-mentioned it is traditional based on Block-type pilot and based on the channel estimation method of IAM-C on the basis of, the present invention is done
Following improvement:
The energy centrality of channel impulse response (channel impulse response, CIR).Time domain channel energy base
Originally it concentrates on limited sampled point of OFDM/OQAM symbol, remaining sampled point energy is it is seen that interchannel noise and system
The superposition of interfering energy.Therefore, the energy for retaining the time sampling point that the maximum multipath time delay of channel impulse response includes, by it
The energy zero setting of remaining sampled point:
Here, l and k represents sub-carrier number, and L represents channel length, equal to maximum delay extension in each diameter of channel divided by adopting
Sample interval, sampling interval are the inverse of sample frequency, and L is much smaller than the number M of subcarrier.
A kind of OFDM/OQAM system channel estimation method is present embodiments provided, the OFDM/OQAM system of the present embodiment is such as
Shown in Fig. 1, channel circumstance is IEEE 802.22WRAN standard channel model, this system is used to be had well on time-frequency domain
The filter (such as EGF and IOTA) of localization characteristic and good energy focusing property, therefore can be approximate from phase by interference
Adjacent symbol.Meanwhile on based on the maximized pilot configuration design of equivalent pilot power, the present embodiment uses IAM-C pilot tone
Structure reduces influence of the interference to precision of channel estimation in channel estimation process.It is as follows that parameter is respectively arranged in the present embodiment system:
Table 1
The channel estimation method based on FDA-FFT under OFDM/OQAM system is described below in the present embodiment, i.e., it is a kind of
OFDM/OQAM system channel estimation method, as shown in Fig. 2, specific steps:
The generation of information source and orthogonal QAM mapping.
Step 1: the frequency domain information source data of 2048 rows, 1000 column are generated, it is each to be classified as a symbol.The n-th of m-th of symbol
Data on a subcarrier are expressed as am,n, (m ∈ [1,1000]；N ∈ [1,2048] and m and n are positive integer).By orthogonal
QAM mapping, information source binary data are mapped to complex data.
IAM-C and Block-type pilot structure.
Step 2: treated data symbol is inserted into IAM-C pilot configuration.Firstly, being inserted into one in the front end of data
A Block-type pilot, then, then by Block-type pilot symbol by every five column datas be inserted into a Block-type pilot in the way of periodically
It is inserted between data.
Between Data Frontend and data Block-type pilot is inserted into be made of three column frequency pilot signs, wherein first row and
Third column are set as complete zero, secondary series be then designed as according to pilot tone equivalent power maximization principle 1, j, -1,-j, 1, j, -1, -
J...... }, wherein j is imaginary unit in plural number.
In addition, OFDM/OQAM has the quick reality based on inverse Fourier transform and Fast Fourier Transform (FFT) (IFFT/FFT)
Existing algorithm and the molding impulse function with good time-frequency focus characteristics, computational complexity and the ISI/ICI for reducing system are dry
The influence disturbed.The channel circumstance that the data process of pilot configuration is added simultaneously is IEEE 802.22WRAN standard channel.
Channel estimation method module based on FDA-FFT.
Step 3:FDA channel estimation expression formula is as follows:
Pass through the channel estimation value of available k-th of the subcarrier of above formulaAs channel frequency domain response
Step 4: it is operated by inverse Fourier transform IFFT, channel frequency domain response is transformed into channel impulse response CIR:ThenIt can be expressed as.
Here, l and k represents the number of subcarrier, and L represents channel length, and L is much smaller than the number M of subcarrier.μlSystem of representatives
The interference of system and noise.
Step 5: by sampled point (i.e. L≤l≤M-1) energy zero setting except channel length L, obtaining FDA-FFT algorithm is needed
The channel impulse response wanted
Step 6: by M point (2048 points) FFT transform,It is transformed into the higher channel frequency domain response letter of accuracy
NumberThat is:
The Channel Equalization Algorithm used in the present embodiment is zero forcing equalization, is finally carried out treated data orthogonal
QAM demapping obtains solution adjusting data.The present embodiment square mean error amount (mean square error, MSE) and error performance
(bit error rate, BER) two kinds of indexs compare the accuracy of several channel estimation methods, at the same to algorithm complexity and
Engineering realizability has made comparative analysis.
(1) mean square error estimation accuracy comparison.
Reference value is used as using square mean error amount (mean square error, MSE), passes through mention the present invention
FDA-FFT algorithm and traditional least square (least square, LS), FDA algorithm compare, more several channel estimation methods
Estimate accuracy.Fig. 3 abscissa indicates that signal-to-noise ratio is arranged under OFDM/OQAM system, and ordinate indicates MSE value.This implementation difference
The estimation accuracy of more several algorithms under 4QAM and 16QAM modulation.From figure 3, it can be seen that when estimated accuracy meets MSE=
10-1When, it can be seen that in OFDM/OQAM system from signal-to-noise ratio setting data of several algorithms under 4QAM and 16QAM modulation,
FDA-FFT algorithm ratio LS algorithm has the signal-to-noise ratio advantage of about 15dB and 17dB respectively, has the excellent of about 5dB signal-to-noise ratio than FDA algorithm
Gesture.This is because the present invention further decreases interference and noise energy on time domain impulse response, the channel estimation on frequency domain
Value then than directly with traditional error improvement LS algorithm and FDA algorithm estimated accuracy it is high.
(2) error performance compares.
Fig. 4 abscissa indicates the signal-to-noise ratio setting under OFDM/OQAM system, and ordinate indicates error rate BER.The present embodiment
Improvement situation of more several algorithm for estimating to system error performance equally under the QAM modulation of different rank.It can from Fig. 4
Out, compared with traditional FDA algorithm, FDA-FFT is in 4QAM modulation, BER=10-3In the case of have the snr gain of 1.5dB；In
16QAM modulation, BER=10-1In the case of have the snr gain of 3dB.It analyzes from above-mentioned data it is found that in OFDM/OQAM system
In, FDA-FFT algorithm further improves the error code of system while improving the estimated accuracy of conventional channel algorithm for estimating
Energy.
(3) algorithm complexity compares.
The complexity of several algorithms changes with the complexity of the operations such as IFFT/FFT in the present embodiment, and table 2 gives calculation
The analysis of complexity of method.
Table 2
As shown in Table 2, compared with LS algorithm, FDA algorithm, FDA-FFT algorithm has centainly in multiplying property, additivity complexity
The increase of degree.FDA-FFT algorithm obtained by sacrificing tolerable computational complexity higher accuracy of channel estimation and
The error performance of system.
The present invention first obtains channel frequency domain response on the basis of the FDA algorithm based on Block-type pilotDue in time domain
Channel energy is concentrated mainly on limited sampled point, passes it through progress interference region zero setting on IFFT operation transform to time domain
Operation, then carries out FFT operation again and obtains final frequency domain responseThis method will only exist interchannel noise and system
Gu noisy a large amount of time domain sampling points carry out zero-setting operation, it further reduced the influence interfered to precision of channel estimation, obtain
Higher estimated accuracy was obtained, guarantees the error performance for improving OFDM/OQAM system in the case where certain complexity.
Claims (6)
1. a kind of OFDM/OQAM system channel estimation method, characterized in that include the following steps:
Step 1. generates frequency domain information source data, and obtains complex data after carrying out orthogonal QAM mapping to it；
Step 2. is periodically inserted block-like pilot configuration between the front end and complex data of complex data；Wherein lead for every piece
Frequency structure includes three column frequency pilot signs, and first row and third column are set as complete zero, and secondary series is then maximum according to pilot tone equivalent power
Change principle be designed as 1, j, -1,-j, 1, j, -1,-j ... }；
Step 3. carries out channel using frequency domain averaging method according to a preliminary estimate, to obtain channel frequency domain response；
Step 4. is operated by inverse Fourier transform, and channel frequency domain response is transformed into channel impulse response；
Step 5. retains the energy for the subcarrier that channel impulse response sub-carriers number is [0, L-1], and by channel impulse response
Sub-carriers number is the energy zero setting of the subcarrier of [L, M-1], obtains estimating required channel impulse response；Wherein L is channel
Length, M are the sum of channel impulse response sub-carriers；
Step 6. becomes channel impulse response needed for estimation to estimate that required channel frequency is rung by Fourier transform operation
It answers, which is estimated final channel frequency domain response.
2. a kind of OFDM/OQAM system channel estimation method according to claim 1, characterized in that the sum M etc. of subcarrier
In the line number of frequency domain information source data.
3. a kind of OFDM/OQAM system channel estimation method according to claim 1, characterized in that channel length L is equal to letter
Maximum delay extension is divided by the sampling interval in each diameter in road.
4. a kind of OFDM/OQAM system channel estimation method according to claim 1, characterized in that pilot configuration in step 2
Three column frequency pilot signs line number it is identical as the line number of step 1 frequency domain information source data.
5. a kind of OFDM/OQAM system channel estimation method according to claim 1, characterized in that the frequency generated in step 1
Domain information source data are 2048 rows, 1000 column.
6. a kind of OFDM/OQAM system channel estimation method according to claim 1, characterized in that in step 2, in plural number
By every 5 column insertion one piece of pilot configuration i.e. three column frequency pilot signs between data.
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| CN108627818B (en) * | 2018-03-19 | 2023-11-17 | 桂林电子科技大学 | OFDM-based frequency control array radar communication integrated waveform design method |
| CN108650005B (en) * | 2018-05-19 | 2023-11-14 | 宜春学院 | Pilot structure and channel estimation method for MIMO-FBMC/OQAM system |
| CN109600327B (en) * | 2018-11-28 | 2020-07-28 | 华中科技大学 | Channel estimation method based on imaginary part interference utilization |
| CN111865840B (en) * | 2019-04-26 | 2024-02-23 | 中兴通讯股份有限公司 | Channel estimation method and device |
| CN114696848A (en) * | 2022-04-08 | 2022-07-01 | 哈尔滨工业大学 | Method for suppressing self-interference of simultaneous same-frequency full-duplex relay amplification forwarding residue |
| CN114513396B (en) * | 2022-04-21 | 2022-07-08 | 科大天工智能装备技术（天津）有限公司 | Pilot frequency method and system based on OFDM/OQAM under industrial 5G |
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| CN102868662A (en) * | 2012-09-21 | 2013-01-09 | 河北工业大学 | Channel estimation method for PDM-CO-OFDM (Pulse Duration Modulation-Coherent Optical-Orthogonal Frequency Division Multiplexing) system |
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