CN109981513A - The Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system - Google Patents
The Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system Download PDFInfo
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- CN109981513A CN109981513A CN201910066397.7A CN201910066397A CN109981513A CN 109981513 A CN109981513 A CN 109981513A CN 201910066397 A CN201910066397 A CN 201910066397A CN 109981513 A CN109981513 A CN 109981513A
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- 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
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
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- 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
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/2659—Coarse or integer frequency offset determination and synchronisation
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- 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
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/266—Fine or fractional frequency offset determination and synchronisation
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- 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
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
- H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
- H04L27/3854—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
Abstract
The invention belongs to wireless communication technology fields, disclose a kind of Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system, comprising: are grouped using PN1 training sequence, are divided into five groups of adjacent sets auto-correlations and carry out frame synchronization；Coarse frequency offset is carried out using the phase difference between the adjacent packets of PN1 training sequence according to the principle of offset estimation to synchronize；It estimates thick frequency deviation and thick frequency deviation compensation is carried out to the data on every receiving antenna later；Cross-correlation is carried out using PN2 training sequence and local PN2 training sequence, the influence of pseudo- multipath is successfully avoided to complete smart Timing Synchronization；Using the auto-correlation of PN2 training sequence and cyclic prefix, the phase difference of front and back data carries out smart offset estimation；It estimates smart frequency deviation and smart frequency deviation compensation is carried out to the data on every receiving antenna later.Essence Timing Synchronization processing of the invention can accurately detect that starting point avoids introducing ISI, guarantee the orthogonality between subcarrier.
Description
Technical field
The invention belongs to wireless communication technology field more particularly to a kind of indoor high-speed large capacity MIMO-OFDM systems
Time And Frequency synchronous method.
Background technique
Currently, the prior art commonly used in the trade is such that fast development and portable shifting with information science technology
Increasing, demand continuous improvement of the people to information data of the electronic products such as dynamic communication apparatus, more and more people are urgent
It is required to carry out the communication such as data, voice and video of real-time high-efficiency at any time and any place.As mobile Internet
For each individual that technology uses, the user more than 80% is in indoor environment.Indoor acquisition signal will consider
To the signal of penetration loss and reflection path, reflection and refracted signal be can not ignore for limited indoor environment, indoor
Environment increases due to signal reflex number, and multipath effect is also more serious.The characteristic of indoor radio propagation channel and simulation side
Method is for many years always by wireless communication field extensive concern.The system of any commercial operation cannot all ignore indoor environment
Covering, indoor communications quality receive more and more attention.
Future wireless system will have the higher rate of information throughput, and there are also many challenges for high-speed radiocommunication system design:
Bandwidth increases severely, channel circumstance is complicated and low time delay, the high reliability request of system.Orthogonal frequency division multiplexing (Orthogonal
Frequency-Division Multiplexing, OFDM) technology can be very good to overcome the frequency selectivity of wireless channel to decline
It falls, due to the being simple and efficient property that it is realized, OFDM, which has become, realizes one of technology most crucial in the following high-speed radiocommunication.
MIMO (Multiple Input Multiple Output) system can be readily available the space diversity gain of wireless channel
With the capacity gain for realizing wireless channel.OFDM and MIMO technology oneself become two big foundation stones of advanced wireless transmissions technology, OFDM
Combination with MIMO technology is to realize the bright approach of wireless data high-speed high capacity reliable transmission.
For any digital communication system, synchronous is all a problem for needing to solve, and is calculated without accurately synchronous
Method cannot carry out effectively reliable receive to data.Ofdm system is very sensitive to synchronizing, and inaccurate synchronizing, which will lead to, is
The decline for performance of uniting.For high speed, large capacity MIMO-OFDM system, quickly, accurately and efficiently Time And Frequency is synchronous
It is the key that improve system performance and difficult point.It is directed to SISO (Single Input Single Output)-ofdm system at present
Synchronized algorithm, research achievement is more, and industry has been presented for many synchronized algorithms and is roughly divided into four kinds so far, respectively based on leading
The synchronization of frequency, the synchronization based on protection interval and the synchronization based on training sequence.For indoor high-speed, large capacity MIMO-
For ofdm system, if it is desired that synchronizing processing with pilot tone, the frequency domain for converting data from time domain is needed, increases complexity
While can not improve precision.Synchronous needs based on protection interval are handled in data field, can not be reached useful
Before data arrive, synchronization process is just completed to the requirement for not meeting high speed.Therefore selection uses the synchronization based on training sequence,
In time domain and the just synchronous processing of completion before receiving valid data.Synchronized algorithm has received widespread attention such as 2015
Year, propose a kind of synchronous method, basic thought is that synchronization process is divided into two stages: first is based on autocorrelative coarse adjustment
Stage and second is based on the differential relevant accurate adjustment stage.It slightly synchronizes and is intended to use by lead code auto-correlation coarse localization, still
Auto-correlation shows a platform, leads to the uncertainty of time detection accuracy, this is because the knot of training sequence circulating repetition
The output of structure judgment variables within the duration of training symbol is all bigger, and the position of maximum value not necessarily appears in frame
Head.In second stage, in order to alleviate platform effect, the differential use correlation displacement different from lead code sub-sequence length comes
Execute correlation.Short time interval of the fine tuning stage centered on thick time Estimate is handled, and difference relevant operation is reduced
Calculated load, but will appear time peak, indoor environment increases due to signal reflex number, and multipath effect is also more serious,
In the case where multi-emitting antenna, with respect to first antenna of other antennas can recycle data indoor MIMO-OFDM system
The processing of displacement to avoid Wave beam forming effect, but will form pseudo- multipath effect in timing stage in this way, cause timing position
Deviation introduce ISI (Inter Symbol Interference), the deviation of timing position may be caused, influence MIMO-
The receiver overall performance of ofdm system.
In conclusion problem of the existing technology is: the precision of existing Time And Frequency synchronized algorithm is low, and error is big.
Solve the difficulty of above-mentioned technical problem:
Indoor environment increases due to signal reflex number, and multipath effect is also more serious, since the presence of multipath causes
Data portion is overlapped between the symbol of front and back, causes intersymbol interference.Due to the increasing of transmitting antenna number in MIMO-OFDM system
Add cause to emit signal not only will by interference identical with traditional single antenna systems influence but also there are inter-antenna interference,
Therefore, the stationary problem of MIMO-OFDM system is more than a single aerial system difficulty.
Solve the meaning of above-mentioned technical problem:
Ofdm system is very sensitive to synchronizing, and inaccurate synchronizing will lead to the decline of system performance, introduces ISI.It is synchronous
Processing is the first step the to be carried out operation of MIMO-OFDM receiver, is the basis of subsequent channel estimation and signal detection.For height
For speed, large capacity MIMO-OFDM system, it is the key that improve system performance that quickly, accurately and efficiently Time And Frequency, which synchronizes,
And difficult point.
Summary of the invention
In view of the problems of the existing technology, the present invention provides a kind of indoor high-speed large capacity MIMO-OFDM systems
Time And Frequency synchronous method.
The invention is realized in this way a kind of Time And Frequency side of synchronization of indoor high-speed large capacity MIMO-OFDM system
The Time And Frequency synchronous method of method, the indoor high-speed large capacity MIMO-OFDM system includes:
The first step is grouped using PN1 training sequence, is divided into five groups of adjacent sets auto-correlations and is carried out frame synchronization；
Second step is carried out slightly according to the principle of offset estimation using the phase difference between the adjacent packets of PN1 training sequence
Offset estimation is synchronous；
Third step estimates thick frequency deviation and carries out thick frequency deviation compensation to the data on every receiving antenna later；
4th step carries out cross-correlation using PN2 training sequence and local PN2 training sequence, successfully avoids the shadow of pseudo- multipath
It rings and completes smart Timing Synchronization；
5th step, using the auto-correlation of PN2 training sequence and cyclic prefix, the phase difference of front and back data carries out smart frequency deviation and estimates
Meter；
6th step estimates smart frequency deviation and carries out smart frequency deviation compensation to the data on every receiving antenna later.
Further, the Time And Frequency synchronous method of the indoor high-speed large capacity MIMO-OFDM system specifically includes:
Step 1: frame synchronization, the process of frame synchronization are carried out to received data；
Step 2: carrying out coarse frequency offset, and the estimation of thick frequency deviation is completed during frame synchronization, and carrying out, frame is same
It asks the phase difference receiving antenna between second group, third group and the 4th group of adjacent sets to do MRC operation summation while step to be averaging
Obtain thick frequency deviation Δ fcoarse, formula is；
Wherein LS2It represents the distance between grouping length, i and represents the i-th receiving antenna i=1 ..., Nr, k (k=2 ..., 4)
Represent packet count Ri,nConjugation correlation window is represented, n (n=1 ..., len) represents the length of search window, m (m=1 ... Ls2) generation
The autocorrelative length of window of table；
Seek thick frequency deviation formula are as follows:
Phase value, Δ f are asked in wherein arg () representativecoarseIt is the thick frequency deviation estimated；
Step 3, this step carry out thick frequency deviation compensation, and every antenna will carry out thick frequency deviation compensation formula are as follows:
rk=rk.*exp(j*2*pi*(-Δfcoarse)*(0:len-1)/Nfft)；
Wherein rkBe kth (k=1 ..., Nr) a receiving antenna signal, wherein NfftThe length of an OFDM symbol is represented,
NrReceiving antenna number, Δ fcoarseIt is the thick frequency deviation estimated, j imaginary unit；
Step 4 will form pseudo- multipath effect in timing stage, cause the deviation of timing position to introduce ISI, to frame synchronization
Error corrected；
Step 5, smart offset estimation, smart offset estimation is using PN2 training sequence；
Step 6 carries out frequency deviation compensation, the formula of frequency deviation compensation using obtained smart frequency deviation are as follows:
rk=rk.*exp(j*2*pi*(-Δffine)*(0:len-1)/Nfft)；
Wherein rkBe kth (k=1 ..., Nr) a receiving antenna signal, Δ ffineIt is the thin frequency deviation estimated, len is letter
Number length, NfftIt is the length of FFT, MIMO-OFDM system synchronously completes.
Further, the step 1 specifically includes:
(1) received data are grouped be divided into five groups of every group of data length be Ls2；
(2) to the data of grouping, every group of data will do auto-correlation with adjacent group and obtain conjugation correlation window Ri,nAnd energy
Window Ci,nIt will be operated on every receiving antenna, summation averaging finally is carried out to the judgment variables on all antennas
Carry out MRC (Maximum ratio Combining) operation, formula are as follows:
Wherein, i (i=1 ..., Nr) receiving antenna is represented, k represents packet count k=1 ..., 5, n (n=1 ..., len) generations
The length of table search window, m (m=1 ... Ls2) autocorrelative length of window is represented, j is imaginary unit, | | it is modulus operation
Symbol, Ri,nIt is conjugation correlation window, Ci,nIt is energy window, n represents first group of position n=L of PN1 training sequences2；
(3) it obtains energy window and conjugation correlation window further seeks judgment variables Mn, formula are as follows:
Wherein n=1 ..., len, MnJudgment variables are represented, | | it is modulo operator；
(4) when continuous 30 values of statistical decision variable are both greater than decision threshold, frame synchronization success, the mistake of statistics are considered as
Retain position and the continuous renewal of maximum value, formula in journey are as follows:
Fram_pos=max (Mn)；
Wherein fram_pos represents the position that a frame data start, the namely thick timing of frame synchronization, the position that data start
Within limits, range is Δ τ ∈ [- Lcp,Lcp] it is considered as the data frame arrival of burst, frame synchronization success.
Further, the step 4 specifically includes:
(1) after thick frequency deviation is corrected, movement will be moved to L before PN2 training sequence herein backwardcpA point；
(2) received data and local PN2 training sequence, which are done, related obtains correlation window Ci(n), formula are as follows:
Wherein i (i=1 ... Nr) receiving antenna is represented,Represent the length of cross-correlation window, pPN2
It (m) is that local PN2 training sequence essence synchronization processes respectively on different antennas, ri(n) it is received to represent i-th of receiving antenna
Data, LPN2Represent the length of PN2 training sequence；
(3) the obtained correlation window that obtained correlation window is subtracted to front, observes minuend by formula M (n)
, formula are as follows:
Pos=max (M (n))；
M (n) represents judgment variablesThe position that pos represents smart timing position maximum value is exactly smart timing
Position, max () representative be maximized.
Further, the step 5 specifically includes:
(1) smart offset estimation is not carried out using in the position of PN2 training sequence in the position that PN2 training sequence starts
Set forward movementWith
(2) existWithThe auto-correlation for doing PN2 training sequence respectively obtains Ri,1And Ri,2, PN2 training sequence is two
The sequence that the equal sequence of segment length adds GI to form, obtaining two frequency deviations is respectively Δ fi,1With Δ fi,2, formula are as follows:
Wherein Ri,1(i=1 ..., Nr) auto-correlation of PN2 training sequence first segment is represented, n, which represents PN1 training sequence, to be terminated
PositionRi,2(i=1 ..., Nr) represent the auto-correlation of PN2 training sequence second segment, ri,n(m) m=1 ..., LPN2
Represent i-th (i=1 ..., Nr) a received data of receiving antenna, NfftBe an OFDM symbol length arg () representative ask
Phase value；
(3) after obtaining two frequency deviations, summation, which is averaging, finally does MRC operation in each antenna, estimates thin frequency deviation Δ
ffine, formula are as follows:
Wherein NrFor receiving antenna number, i=1 ..., Nr。
Another object of the present invention is to provide a kind of times using the indoor high-speed large capacity MIMO-OFDM system
With the radio communication platform of frequency synchronization method.
In conclusion advantages of the present invention and good effect are as follows: utilize the auto-correlation of PN1 training sequence in the frame synchronization stage
Property be divided into five groups, to reach frame synchronization, can use during frame synchronization packet characteristic utilize context phase difference
Can with obtain a thick frequency deviation, compare other synchronizing processes, frame synchronization and thick frequency deviation can complete together, save resource,
Secondly in smart timing stage since MIMO-OFDM system is in the case where multi-emitting antenna, data are carried out with the place of cyclic shift
Reason, causes pseudo- multipath effect, and the deviation of timing position is caused to introduce ISI.
The present invention can completely avoid this problem, correct to the error of frame synchronization, it is ensured that the starting of OFDM symbol
Position is to carry out FFT demodulation, and smart Timing Synchronization processing can accurately detect that starting point avoids introducing ISI, finally in smart frequency deviation mistake
Being divided into two parts not only to PN2 training sequence in journey can guarantee precision but also will not introduce ISI, guarantee the orthogonality between subcarrier,
The synchronous overall performance of receiver of the MIMO-OFDM system based on training sequence can be improved by synchronization process.
Detailed description of the invention
Fig. 1 is the Time And Frequency side of synchronization of indoor high-speed large capacity MIMO-OFDM system provided in an embodiment of the present invention
Method flow chart.
Fig. 2 is the format of the training sequence provided in an embodiment of the present invention used.
Fig. 3 is the format of the PN1 training sequence provided in an embodiment of the present invention used.
Fig. 4 is the format that the MIMO-OFDM system 2 provided in an embodiment of the present invention used sends out 2 time receiving PN2 training sequences.
Fig. 5 is the format that the MIMO-OFDM system 4 provided in an embodiment of the present invention used sends out 4 time receiving PN2 training sequences.
Fig. 6 is the MIMO-OFDM system frame synchronization flow chart provided in an embodiment of the present invention based on training sequence.
Fig. 7 is B channel essence timing method in the MIMO-OFDM system chambers provided in an embodiment of the present invention based on training sequence
With existing algorithm simulating figure.
Fig. 8 is that the timing of B channel essence is adjudicated in the MIMO-OFDM system chambers provided in an embodiment of the present invention based on training sequence
Variable analogous diagram.
Fig. 9 is B channel essence offset estimation in the MIMO-OFDM system chambers provided in an embodiment of the present invention based on training sequence
Method and existing algorithm simulating figure.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to embodiments, to the present invention
It is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, it is not used to
Limit the present invention.
Present invention seek to address that the precision of existing Time And Frequency synchronized algorithm is low, the big problem of error, accurate, quick,
It is efficiently completed MIMO-OFDM system time and Frequency Synchronization.
Application principle of the invention is explained in detail with reference to the accompanying drawing.
As shown in Figure 1, the Time And Frequency of indoor high-speed large capacity MIMO-OFDM system provided in an embodiment of the present invention is same
One step process the following steps are included:
S101: being grouped using PN1 training sequence, is divided into five groups of adjacent sets auto-correlations and is carried out frame synchronization；
S102: thick frequency is carried out using the phase difference between the adjacent packets of PN1 training sequence according to the principle of offset estimation
Estimation synchronizes partially；
S103: it estimates thick frequency deviation and thick frequency deviation compensation is carried out to the data on every receiving antenna later；
S104: cross-correlation is carried out using PN2 training sequence and local PN2 training sequence, successfully avoids the influence of pseudo- multipath
Complete smart Timing Synchronization；
S105: using the auto-correlation of PN2 training sequence and cyclic prefix, the phase difference of front and back data carries out smart frequency deviation and estimates
Meter；
S106: it estimates smart frequency deviation and smart frequency deviation compensation is carried out to the data on every receiving antenna later.
The Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system provided in an embodiment of the present invention is specific
The following steps are included:
Receiver received signal isNrIt represents and receives
Antenna number NtRepresent transmitting antenna number, k=1 ..., Nr, rk(n) be k-th of receiving antenna signal, len be receive Chief Signal Boatswain
Degree is defined as follows parameters: NfftRepresent the length of an OFDM symbol, LPN1Represent the length of PN1 training sequenceLS1Represent the length of each group of data in 10 groups of arrays of PN1 training sequenceLs2Training sequence 10
The length of every two groups of data in group arrayLPN2Represent the length L of PN2 training sequencePN2=Nfft, LcpFor circulation
The length of prefix is equal topPN2(m) local training sequence m=1 is represented ... LPN2；
Step 1: to received data carry out frame synchronization, the process of frame synchronization, as shown in Figure 6；
(1) received data are grouped first be divided into five groups of every group of data length be Ls2；
(2) to the data of grouping, every group of data will do auto-correlation with adjacent group and obtain conjugation correlation window Ri,nAnd energy
Window Ci,nIt will be operated on every receiving antenna, summation averaging finally is carried out to the judgment variables on all antennas
Carry out MRC (Maximum ratio Combining) operation, formula are as follows:
Wherein, i (i=1 ..., Nr) receiving antenna is represented, k represents packet count k=1 ..., 5, n (n=1 ..., len) generations
The length of table search window, m (m=1 ... Ls2) autocorrelative length of window is represented, j is imaginary unit, | | it is modulus operation
Symbol, Ri,nIt is conjugation correlation window, Ci,nIt is energy window, n represents first group of position n=L of PN1 training sequences2；
(3) it obtains energy window and conjugation correlation window further seeks judgment variables Mn, formula are as follows:
Wherein n=1 ..., len, MnJudgment variables are represented, | | it is modulo operator；
(4) when continuous 30 values of statistical decision variable are both greater than decision threshold, frame synchronization success, the mistake of statistics are considered as
Retain position and the continuous renewal of maximum value, formula in journey are as follows:
Fram_pos=max (Mn)；
Wherein fram_pos represents the position that a frame data start, the namely thick timing of frame synchronization, the position that data start
Within limits, range is Δ τ ∈ [- Lcp,Lcp] it is considered as the data frame arrival of burst, frame synchronization success；
Step 2: carrying out coarse frequency offset, and the estimation of thick frequency deviation is completed during frame synchronization, and carrying out, frame is same
It asks the phase difference receiving antenna between second group, third group and the 4th group of adjacent sets to do MRC operation summation while step to be averaging
Obtain thick frequency deviation Δ fcoarse, formula is；
Wherein LS2It represents the distance between grouping length, i and represents the i-th receiving antenna i=1 ..., Nr, k (k=2 ..., 4)
Represent packet count Ri,nConjugation correlation window is represented, n (n=1 ..., len) represents the length of search window, m (m=1 ... Ls2) generation
The autocorrelative length of window of table；
Seek thick frequency deviation formula are as follows:
Phase value, Δ f are asked in wherein arg () representativecoarseIt is the thick frequency deviation estimated；
Step 3, this step carry out thick frequency deviation compensation, and every antenna will carry out thick frequency deviation compensation formula are as follows:
rk=rk.*exp(j*2*pi*(-Δfcoarse)*(0:len-1)/Nfft)；
Wherein rkBe kth (k=1 ..., Nr) a receiving antenna signal, wherein NfftThe length of an OFDM symbol is represented,
NrReceiving antenna number, Δ fcoarseIt is the thick frequency deviation estimated, j imaginary unit；
Step 4, smart timing stage is since MIMO-OFDM system is in the case where multi-emitting antenna, other antennas are with respect to
A piece antenna can carry out the processing of cyclic shift to data, to avoid Wave beam forming effect, but in this way in timing stage meeting shape
At pseudo- multipath effect, the deviation of timing position is caused to introduce ISI, this algorithm can completely avoid this problem to the mistake of frame synchronization
Difference is corrected.
(1) after thick frequency deviation is corrected, movement will be moved to L before PN2 training sequence herein backwardcpA point to avoid
The influence of frame synchronization；
(2) received data and local PN2 training sequence, which are done, related obtains correlation window Ci(n), formula are as follows:
Wherein i (i=1 ... Nr) receiving antenna is represented,Represent the length of cross-correlation window, pPN2
It (m) is that local PN2 training sequence essence synchronization processes respectively on different antennas, ri(n) it is received to represent i-th of receiving antenna
Data, LPN2Represent the length of PN2 training sequence；
(3) in order to avoid puppet multipath effect caused by cyclic shift, the operation taken is that the correlation window that will be obtained subtracts
The obtained correlation window of front, it is pseudo- because with respect to first transmitting antenna of other transmitting antennas is ring shift right operation
Multipath is comparable to behind true path at this time be not in peak, pass through when correlation window reaches the position of pseudo- multipath
Formula M (n) is observed that at this moment minuend plays a role, and can inhibit peak thus can be public to avoid pseudo- multipath effect
Formula are as follows:
Pos=max (M (n))；
M (n) represents judgment variablesThe position that pos represents smart timing position maximum value is exactly smart timing
Position, max () representative be maximized；
Step 5, smart offset estimation, smart offset estimation is using PN2 training sequence；
(1) influence in order to avoid ISI to smart offset estimation does not carry out here in the position that PN2 training sequence starts
Smart offset estimation is moved forward using in the position of PN2 training sequenceWith
(2) existWithThe auto-correlation for doing PN2 training sequence respectively obtains Ri,1And Ri,2, because of PN2 training sequence
In the sequence that the equal sequence of two segment length adds GI to form, it is respectively Δ f that operation, which obtains two frequency deviations, in this wayi,1With Δ fi,2With it
His algorithm is compared will not introduce ISI, formula while guaranteeing precision again are as follows:
Wherein Ri,1(i=1 ..., Nr) auto-correlation of PN2 training sequence first segment is represented, n, which represents PN1 training sequence, to be terminated
PositionRi,2(i=1 ..., Nr) represent the auto-correlation of PN2 training sequence second segment, ri,n(m) m=1 ..., LPN2
Represent i-th (i=1 ..., Nr) a received data of receiving antenna, NfftBe an OFDM symbol length arg () representative ask
Phase value；
(3) after obtaining above-mentioned two frequency deviation, summation averaging does aforesaid operations in each antenna and is finally MRC behaviour
Make, estimates thin frequency deviation Δ ffine, formula are as follows:
Wherein NrFor receiving antenna number, i=1 ..., Nr；
Step 6 carries out frequency deviation compensation, the formula of frequency deviation compensation using obtained smart frequency deviation are as follows:
rk=rk.*exp(j*2*pi*(-Δffine)*(0:len-1)/Nfft)；
Wherein rkBe kth (k=1 ..., Nr) a receiving antenna signal, Δ ffineIt is the thin frequency deviation estimated, len is letter
Number length, NfftIt is the length of FFT, MIMO-OFDM system synchronously completes.
Application effect of the invention is explained in detail below with reference to emulation.
1, simulated conditions: the hair of MIMO-OFDM system two two is received, and an OFDM subcarrier number is Nfft=64, useful sub- load
Wave number is Lsub=52；
2, emulation content and result:
Emulation 1, indoors under B channel, the smart timing algorithm present invention and existing and Leil algorithm compare can be with
See that advantage of the invention is as shown in Figure 7, it can be seen that although the good letter of B indoors of the algorithm of Leil performance under Gaussian channel
MIMO-OFDM communication system is good without the performance of this algorithm under road, however multipath channel is necessary in actual communication system
To be considered especially indoors under channel condition, indoor acquisition signal will consider the signal of penetration loss and reflection path,
Reflection and refracted signal be can not ignore for limited indoor environment, and indoor environment increases due to signal reflex number,
Multipath effect is also more serious, therefore the algorithm of patented invention has apparent advantage compared with the algorithm of Leil, more meets reality
The requirement of indoor MIMO-OFDM communication system.
Emulation 3, indoors under channel B channel, the analogous diagram of smart timing judgment variables is as shown in Figure 8, it can be seen that just
True sync bit is equipped with apparent relevant peaks, and on the point in the puppet path as caused by cyclic shift, judgment variables are negative, it is evident that
The algorithm of this patent can effectively avoid puppet path caused by the cyclic shift between MIMO-OFDM system transmitting antenna data from asking
Topic.
Emulation 4, indoors under B channel, the smart frequency deviation method present invention and existing Schmidl algorithm and its innovatory algorithm 1
Compare it can be seen that advantage such as Fig. 9 of the invention show that this algorithm is higher than Schmidl arithmetic accuracy under identical signal-to-noise ratio,
It is higher than 1 precision of innovatory algorithm in this algorithm of high s/n ratio this is because innovatory algorithm 1 does not account for the influence of multipath, use circulation
The information of prefix introduces ISI, however multipath channel is to have to especially believing indoors for consideration in actual communication system
Under the conditions of road, therefore the algorithm of patented invention has apparent advantage more to meet reality compared with Schmidl algorithm and its innovatory algorithm 1
The requirement of border MIMO-OFDM communication system；
In conjunction with Fig. 7, Fig. 8 and Fig. 9 as it can be seen that MIMO-OFDM system time and frequency of the invention based on training sequence are same
One step process either under additive white Gaussian noise channel still indoors under multipath channel, overall performance all advantageously, essence
Timing Synchronization also can be 1 assigning the probability of success compared with low signal-to-noise ratio under severe multipath channel.In smart offset estimation,
Under indoor multipath channel, this algorithm both can guarantee higher precision while will not introduce ISI.
By analogous diagram 7, channel is to be arranged under indoor standard B channel circumstance in the indoor MIMO-OFDM system that two hairs two are received
Monte Carlo simulation number is 10000 times, and it is 100% that essence, which synchronizes successful probability, when signal-to-noise ratio 6dB.There is analogous diagram 8
It can be seen that the puppet multipath effect as caused by the cyclic shift of transmitting antenna is simultaneously in the MIMO-OFDM system that two hairs two are received
Judgment variables are not influenced, are not in that time peak influences court verdict.It is in the interior that two hairs two are received in analogous diagram 9
Channel is that Monte Carlo simulation number is arranged under indoor standard B channel circumstance is to obtain for 10000 times in MIMO-OFDM system,
Indoor B channel is multipath channel, it can be seen that the algorithm of this patent is while improving smart offset estimation and avoids pseudo- multipath
Influence signal-to-noise ratio when be 15dB mean square error be 2.92e-06.
The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the invention, all in essence of the invention
Made any modifications, equivalent replacements, and improvements etc., should all be included in the protection scope of the present invention within mind and principle.
Claims (6)
1. a kind of Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system, which is characterized in that the interior
The Time And Frequency synchronous method of high-speed high capacity MIMO-OFDM system includes:
The first step is grouped using PN1 training sequence, is divided into five groups of adjacent sets auto-correlations and is carried out frame synchronization；
Second step carries out thick frequency deviation using the phase difference between the adjacent packets of PN1 training sequence according to the principle of offset estimation
Estimation synchronizes；
Third step estimates thick frequency deviation and carries out thick frequency deviation compensation to the data on every receiving antenna later；
4th step carries out cross-correlation using PN2 training sequence and local PN2 training sequence, successfully avoids the influence of pseudo- multipath complete
At smart Timing Synchronization；
5th step, using the auto-correlation of PN2 training sequence and cyclic prefix, the phase difference of front and back data carries out smart offset estimation；
6th step estimates smart frequency deviation and carries out smart frequency deviation compensation to the data on every receiving antenna later.
2. the Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system as described in claim 1, feature
It is, the Time And Frequency synchronous method of the indoor high-speed large capacity MIMO-OFDM system specifically includes:
Step 1: frame synchronization, the process of frame synchronization are carried out to received data；
Step 2: carrying out coarse frequency offset, and the estimation of thick frequency deviation is completed during frame synchronization, is carrying out frame synchronization
It asks the phase difference receiving antenna between second group, third group and the 4th group of adjacent sets to do MRC operation summation and be averaging simultaneously to obtain
Thick frequency deviation Δ fcoarse, formula is；
Wherein LS2It represents the distance between grouping length, i and represents the i-th receiving antenna i=1 ..., Nr, k (k=2 ..., 4) it represents
Packet count Ri,nConjugation correlation window is represented, n (n=1 ..., len) represents the length of search window, m (m=1 ... Ls2) represent certainly
Relevant length of window；
Seek thick frequency deviation formula are as follows:
Wherein argPhase value, Δ f are asked in () representativecoarseIt is the thick frequency deviation estimated；
Step 3, this step carry out thick frequency deviation compensation, and every antenna will carry out thick frequency deviation compensation formula are as follows:
rk=rk.*exp(j*2*pi*(-Δfcoarse)*(0:len-1)/Nfft)；
Wherein rkBe kth (k=1 ..., Nr) a receiving antenna signal, wherein NfftRepresent the length of an OFDM symbol, NrIt connects
Receive antenna number, Δ fcoarseIt is the thick frequency deviation estimated, j imaginary unit；
Step 4 will form pseudo- multipath effect in timing stage, cause the deviation of timing position to introduce ISI, to the mistake of frame synchronization
Difference is corrected；
Step 5, smart offset estimation, smart offset estimation is using PN2 training sequence；
Step 6 carries out frequency deviation compensation, the formula of frequency deviation compensation using obtained smart frequency deviation are as follows:
rk=rk.*exp(j*2*pi*(-Δffine)*(0:len-1)/Nfft)；
Wherein rkBe kth (k=1 ..., Nr) a receiving antenna signal, Δ ffineIt is the thin frequency deviation estimated, len is Chief Signal Boatswain
Degree, NfftIt is the length of FFT, MIMO-OFDM system synchronously completes.
3. the Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system as claimed in claim 2, feature
It is, the step 1 specifically includes:
(1) received data are grouped be divided into five groups of every group of data length be Ls2；
(2) to the data of grouping, every group of data will do auto-correlation with adjacent group and obtain conjugation correlation window Ri,nAnd energy window
Ci,nIt will be operated on every receiving antenna, summation finally is carried out to the judgment variables on all antennas and is averaging progress
MRC (Maximum ratio Combining) operation, formula are as follows:
Wherein, i (i=1 ..., Nr) receiving antenna is represented, k represents packet count k=1 ..., and 5, n (n=1 ..., len) represent search
The length of window, m (m=1 ... Ls2) autocorrelative length of window is represented, j is imaginary unit, | | it is modulo operator, Ri,n
It is conjugation correlation window, Ci,nIt is energy window, n represents first group of position n=L of PN1 training sequences2；
(3) it obtains energy window and conjugation correlation window further seeks judgment variables Mn, formula are as follows:
Wherein n=1 ..., len, MnJudgment variables are represented, | | it is modulo operator；
(4) it when continuous 30 values of statistical decision variable are both greater than decision threshold, is considered as frame synchronization and succeeds, during statistics
Retain the position of maximum value and continuous renewal, formula are as follows:
Fram_pos=max (Mn)；
Wherein fram_pos represents the position that a frame data start, and the namely thick timing of frame synchronization, the position that data start is one
Within the scope of fixed, range is Δ τ ∈ [- Lcp,Lcp] it is considered as the data frame arrival of burst, frame synchronization success.
4. the Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system as claimed in claim 2, feature
It is, the step 4 specifically includes:
(1) after thick frequency deviation is corrected, movement will be moved to L before PN2 training sequence herein backwardcpA point；
(2) received data and local PN2 training sequence, which are done, related obtains correlation window Ci(n), formula are as follows:
Wherein i (i=1 ... Nr) receiving antenna is represented,Represent the length of cross-correlation window, pPN2(m) it is
Local PN2 training sequence essence synchronization processes respectively on different antennas, ri(n) the received data of i-th of receiving antenna are represented,
LPN2Represent the length of PN2 training sequence；
(3) the obtained correlation window that obtained correlation window is subtracted to front observes minuend by formula M (n), public
Formula are as follows:
Pos=max (M (n))；
M (n) represents judgment variablesPos represent smart timing position maximum value position be exactly smart timing position
It sets, max () representative is maximized.
5. the Time And Frequency synchronous method of indoor high-speed large capacity MIMO-OFDM system as claimed in claim 2, feature
It is, the step 5 specifically includes:
(1) not the position that PN2 training sequence starts carry out smart offset estimation using the position of PN2 training sequence to
Preceding movementWith
(2) existWithThe auto-correlation for doing PN2 training sequence respectively obtains Ri,1And Ri,2, PN2 training sequence is long at two sections
The sequence that equal sequence adds GI to form is spent, obtaining two frequency deviations is respectively Δ fi,1With Δ fi,2, formula are as follows:
Wherein Ri,1(i=1 ..., Nr) auto-correlation of PN2 training sequence first segment is represented, n represents the position that PN1 training sequence terminates
It setsRi,2(i=1 ..., Nr) represent the auto-correlation of PN2 training sequence second segment, ri,n(m) m=1 ..., LPN2It represents
I-th (i=1 ..., Nr) a received data of receiving antenna, NfftBe an OFDM symbol length arg () representative seek phase
Value；
(3) after obtaining two frequency deviations, summation, which is averaging, finally does MRC operation in each antenna, estimates thin frequency deviation Δ ffine,
Formula are as follows:
Wherein NrFor receiving antenna number, i=1 ..., Nr。
6. a kind of Time And Frequency using indoor high-speed large capacity MIMO-OFDM system described in Claims 1 to 5 any one
The radio communication platform of synchronous method.
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