CN105245484B - The method of MIMO-OFDM system frequency deviations estimation - Google Patents
The method of MIMO-OFDM system frequency deviations estimation Download PDFInfo
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- CN105245484B CN105245484B CN201510688422.7A CN201510688422A CN105245484B CN 105245484 B CN105245484 B CN 105245484B CN 201510688422 A CN201510688422 A CN 201510688422A CN 105245484 B CN105245484 B CN 105245484B
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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
- H04L27/2668—Details of algorithms
- H04L27/2669—Details of algorithms characterised by the domain of operation
- H04L27/2672—Frequency domain
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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
- H04L27/2668—Details of algorithms
- H04L27/2681—Details of algorithms characterised by constraints
- H04L27/2682—Precision
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Abstract
The present invention relates to a kind of methods of MIMO ofdm systems frequency offset estimation, the signal comprising short training sequence, long training sequence and SIG sequences received for several reception antennas to MIMO ofdm system receivers carries out frequency offset estimation, and this method is calculated coarse frequency deviation including the use of the short training sequence of signal, long training sequence frequency departure is calculated using the long training sequence of signal, being calculated the summation to the rear of time domain residual carrier frequency using SIG sequences as the estimated result of carrier wave frequency deviation.This method has higher frequency offset estimation accuracy and very wide application range.
Description
Technical field
The present invention relates to a kind of MIMO-OFDM system receivers to carry out carrier frequency using training sequence and SIG sequences
The method of estimation of deviation, the method for being particularly suitable for carrying out frequency offset estimation when similar 802.11n frame structure signals receive.
Background technology
In ofdm system, carrier frequency offset can cause the frequency domain sample value for receiving signal to shift.Moreover, if carrying
Wave frequency rate deviation is not the integral multiple of subcarrier spacing, will there is " leakage " of energy between subcarrier, is caused between subcarrier
Orthogonality destroyed, introduce inter-sub-carrier interference (ICI).ICI directly affects channel estimation and reception demodulation as a result, whole
The reception Packet Error Ratio of system system increases.Relative to a single aerial system, the interference between MIMO-OFDM system spatial data streams makes
Obtain overall performance is influenced bigger by ICI, and therefore, MIMO-OFDM has higher requirement for carrier frequency offset estimation.
Ofdm signal frame in 802.11n includes three kinds of formats, and each pattern frame head part all includes training field and letter
Number field.Estimate in general, IEEE802.11n systems carry out frequency deviation using the short training sequence and long training sequence data of preamble field
Meter, this offset estimation residual frequency deviation based on time domain very little, but still there is most of residual frequency deviation to be more than carrier wave interval
1%, certain influence is still had for the decoding performance of MIMO-OFDM systems, and new method is needed to further increase frequency deviation
The precision of estimation.
Invention content
The object of the present invention is to provide a kind of precision improving offset estimation, to improve the whole decoding performance of system
The method of MIMO-OFDM system frequency deviations estimation.
In order to achieve the above objectives, the technical solution adopted by the present invention is：
A kind of method of MIMO-OFDM system frequency deviations estimation, for total N to MIMO-OFDM system receiversrx
The signal comprising short training sequence, long training sequence and SIG sequences that a reception antenna is received carries out frequency offset estimation, should
Method includes the following steps：
The first step：Coarse frequency deviation delta f is calculated using the short training sequence of the signalsts；
Second step：Long training sequence frequency deviation f is calculated using the long training sequence of the signallts；
Third walks：For each SIG field in the SIG sequences, acquired respectively by following steps (1)-(3) described
SIG sequences in each SIG field channel weights frequency domain phase deviation average value Rx_SIG_Freq_Dif：
(1) frequency domain data of the SIG field of each reception antenna is calculated, further according to the frequency domain data
Calculate channel equalization data Rx_SIG_Freq_rx (i)；The channel equalization number for the SIG field that each antenna is received
According to being averaged to obtain average frequency domain data Rx_SIG_Freq, the average frequency domain data Rx_SIG_Freq demappings are conciliate
Code obtains SIG information datas；
(2) the SIG information datas are re-started into coding and mapping generates SIG local frequency domain data Local_SIG_
Freq；
(3) according to the average frequency domain data Rx_SIG_Freq and locals the SIG frequency domain data Local_
The channel weights frequency domain phase deviation average value Rx_SIG_Freq_ of each nonzero value frequency point in the domains SIG is calculated in SIG_Freq
Dif；
4th step：It is calculated after the channel weights frequency domain phase deviation average value plural number of each SIG field is summed
Its plural angle, obtains average phase deviation
5th step：According to the average phase deviationAnd the mean coefficient α of each SIG field calculates one
The residual phase deviation that residual frequency deviation generates in a symbol interval
6th step：The residual phase deviation generated according to residual frequency deviation in a symbol intervalIt calculates
Obtain time domain residual carrier frequency offset Δ fsig；
7th step：The estimated result of carrier wave frequency deviation is calculated, the estimated result of the carrier wave frequency deviation is the coarse frequency
Deviation delta fsts, described long training sequence frequency deviation fltsWith the time domain residual carrier frequency offset Δ fsigThe sum of Δ flts
+Δfsts+Δfsig。
In the first step, the short training sequence includes that several continuously repeat field, using described continuous
Repeating Field respectively calculates each reception antenna received signal
Afterwards, it carries out multiple antennas weighted average and calculates angle wherein, Ts is described
Continuously repeat the length of field；∠ is the angle operation of calculated complex, then the coarse frequency deviation
In the second step, the long training sequence includes several long training fields, utilizes the long training
Field respectively calculates each reception antenna received signal
Afterwards, it carries out multiple antennas weighted average and calculates angleWherein, Ts2It is described
Long training field length；The then long training sequence frequency departure
In the step of third walks (1), the time domain sampled data of the SIG field described in each is passed through respectively
FFT operations obtain obtaining the channel equalization data Rx_SIG_ after the frequency domain data, then channel equalized operation
The channel equalization data weighted average of Freq_rx (i), the SIG field that each antenna is received obtain average frequency domain number
According toFinally pass through BPSK demappings and convolution decoder obtain it is described
SIG information datas.
In the step of third walks (3), pass through calculating
Obtain the channel weights frequency domain phase deviation average value Rx_SIG_Freq_ of each nonzero value frequency point in the domains SIG
Dif。
In 5th step,
In 6th step,Wherein TsymbolFor the length of a symbol interval
Degree.
Since above-mentioned technical proposal is used, the present invention has following advantages compared with prior art：The frequency deviation of the present invention is estimated
Meter method is utilized SIG sequences and carries out frequency domain offset estimation, when multiple SIG fields on the basis of time-domain frequency deviation estimation
Plural summation can be carried out, there is higher frequency offset estimation accuracy, especially in the case of low signal-to-noise ratio.It can not only be answered
It is similar usable with leading and SIG field MIMO-OFDM systems for other for 802.11n systems, have very wide
Application range.
Description of the drawings
Attached drawing 1 is three kinds of PPDU signal frame formats of 802.11n.
Attached drawing 2 is the mean error simulation result with traditional frequency deviation estimating method of frequency deviation estimating method of the present invention.
Specific implementation mode
The invention will be further described for embodiment shown in below in conjunction with the accompanying drawings.
Embodiment one：Three kinds of PPDU signal frame formats of 802.11n are as shown in Fig. 1, wherein including short training sequence
STF, long training sequence LTF and SIG sequence.And in the HT_Mixed format signal frames of 802.11n, short training sequence STF, long instruction
SIG sequences after white silk sequence LTF include L_SIG, HT_SIG1 and HT_SIG2 totally 3 SIG fields.It is somebody's turn to do below with receiving
The method of MIMO-OFDM system frequency deviations estimation is described in detail for HT_Mixed format signals.
The first step：Coarse frequency deviation delta f is calculated using the short training sequence STF for receiving signalsts。
Short training sequence STF includes that several continuously repeat field STS, using continuously repeating field STS respectively to each
Reception antenna received signal calculates
Afterwards, it carries out multiple antennas weighted average and calculates angle
In above-mentioned calculating, Ts is the length for continuously repeating field STS；∠ is the angle operation of calculated complex, and Rx_STS is
The short training sequence that every reception antenna receives.
Then coarse frequency deviation
Second step：Long training sequence frequency deviation f is calculated using the long training sequence LTF for receiving signallts。
Long training sequence LTF includes two continuous long training field LTS, using long training field LTS respectively to each
Reception antenna received signal calculates
Afterwards, it carries out multiple antennas weighted average and calculates angle
Wherein, Ts2For the length of long training field.
Then long training sequence frequency departure
By above-mentioned coarse frequency deviation delta fstsWith long training sequence frequency deviation fltsSummation obtains Δ flts+Δfsts,
The method that as common short training sequence and long training sequence data using preamble field carries out offset estimation, it is this to be based on
The offset estimation residual frequency deviation of time domain very little, can approximation ignore the influence of inter-carrier interference (ICI), carrier wave frequency deviation draws at this time
The frequency domain phase deviation risen is identical for all subcarriers.Therefore, each non-zero frequency point of SIG field frequency domain can proceed with multiple
Number weighted sum obtains frequency point average phase deviation.
Third walks：For each SIG field in SIG sequences, acquired in SIG sequences by following steps (1)-(3) respectively
The channel weights frequency domain phase deviation average value Rx_SIG_Freq_Dif of each SIG field.
(1) after demodulating and decoding obtains SIG bit information data, the time domain sampled data of each SIG field is passed through respectively
FFT operations are crossed to obtain obtaining channel equalization data Rx_SIG_Freq_rx (i) after frequency domain data, then channel equalized operation,
The channel equalization data weighted average for the SIG field that each antenna is received obtains average frequency domain dataFinally pass through BPSK demappings and convolution decoder obtains SIG Information Numbers
According to.
(2) SIG information datas are re-started into coding and mapping generates SIG local frequency domain data Local_SIG_Freq.
(3) it is calculated according to average frequency domain data Rx_SIG_Freq and SIG local frequency domain data Local_SIG_Freq
To the channel weights frequency domain phase deviation average value Rx_SIG_Freq_Dif of each nonzero value frequency point in the domains SIG.Specially：Pass through
It calculates
Obtain the channel weights frequency domain phase deviation average value Rx_SIG_Freq_Dif of each nonzero value frequency point in the domains SIG.
Below by taking the SIG of HT_Mixed format signal frames as an example：
Step (1)：Frequency domain data is obtained by FFT operations to the time domain sampled data of each L_SIG field, then through letter
Channel equalization data Rx_L_SIG_Freq_rx (i) is obtained after trace equalization operation, the L_SIG fields that each antenna is received
Channel equalization data weighted average obtains average frequency domain dataMost
Afterwards L_SIG information datas are obtained by BPSK demappings and convolution decoder.
Step (2)：L_SIG information datas are re-started into coding and mapping generates the local frequency domain data of L_SIG fields
Local_L_SIG_Freq。
Step (3)：It calculates
To the channel weights frequency domain phase deviation average value Rx_L_ of each nonzero value frequency point in the domains L_SIG (48 data frequency points and 4 pilot points)
SIG_Freq_Dif。
It repeats the above steps, the frequency domain phase for respectively obtaining each nonzero value frequency point in the domains HT_SIG1 and the domains HT_SIG2 is inclined
Poor Rx_HT_SIG1_Freq_Dif and Rx_HT_SIG2_Freq_Dif.
4th step：By the frequency domain phase deviation result plural number summation of this 3 fields of L_SIG, HT_SIG1 and HT_SIG2, then
Angle is calculated to summed result, obtains average phase deviation
5th step：, according to average phase deviationAnd the mean coefficient α of each SIG field calculates a mark space
The residual phase deviation that residual frequency deviation generates in timeI.e.Here for multiple SIG fields equally based on multiple
The thought of number summation weighting, plural number summation obtain average phase deviation, can further eliminate the influence of noise.
By taking HT_Mixed signal frames as an example, theoretically after the long sequence offset estimation of time domain, the frequency domain of 3 SIG fields is adopted
Sample phase deviation is respectivelyWithFor a mark space Tsymbol=4us residual frequency deviations
The phase deviation of generation, then mean coefficient α=(1.6+2.6+3.6)/3=2.4, then
6th step：According to a symbol interval TsymbolThe residual phase deviation that interior residual frequency deviation generatesIt calculatesObtain time domain residual carrier frequency offset Δ fsig。
7th step：The estimated result of carrier wave frequency deviation is calculated, the estimated result of carrier wave frequency deviation is coarse frequency deviation delta fsts, it is long
Training sequence frequency deviation fltsWith time domain residual carrier frequency offset Δ fsigThe sum of Δ flts+Δfsts+Δfsig。
The method of the present invention and traditional time-domain frequency deviation estimation are subjected to simulation result comparison, simulated conditions are set as
Transmitting terminal generates HT_Mixed format signal frames, MCS=11 (antenna 2*2), and signal enters reception by TGn_B simulated channels
End, receiving terminal carries out offset estimation operation, under conditions of different Signal to Noise Ratio (SNR), respectively emulates 1000 data packets, average remnants
Offset estimation error comparing result is shown in attached drawing 2.In attached drawing 2, circle solid line is the simulation result of conventional Time-domain frequency deviation estimating method, side
Block solid line is that the time domain of the present invention adds the simulation result of the frequent bias estimation of frequency domain.It can be seen from the figure that the frequency of the present invention
Bias estimation improves 8db~9db or so compared with the performance of conventional Time-domain frequency deviation estimating method, and ratio is promoted when signal-to-noise ratio is low
More apparent, performance is also promoted when noise is relatively high.
The normalization residual frequency deviation of two kinds of frequency excursion algorithms (is spaced) estimated value between residual frequency deviation/subcarrier
Error distribution results are as shown in following table one and table two.
The evaluated error distribution of results of table one, conventional Time-domain frequency deviation estimating method
| SNR | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| >5% | 0.3 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| >2% | 11.6 | 7.7 | 4.4 | 2.1 | 1.8 | 0.5 | 0.3 | 0.1 | 0.1 | 0 | 0 | 0 | 0 |
| >1% | 42.9 | 39.5 | 30.4 | 24.5 | 20.8 | 12.5 | 9.3 | 6.1 | 4.7 | 1.9 | 1.8 | 1.8 | 1.1 |
| >0.5% | 69.6 | 66.5 | 61.1 | 57.4 | 52.6 | 45.7 | 40.1 | 31.3 | 28.4 | 21.9 | 17.5 | 13 | 10.2 |
| >0.1% | 95.3 | 94.1 | 93.4 | 90.7 | 89.1 | 88 | 83.6 | 84 | 82.4 | 80.5 | 79 | 76.4 | 69.5 |
| <0.1% | 4.7 | 5.9 | 6.6 | 9.3 | 10.9 | 12 | 16.4 | 16 | 17.6 | 19.5 | 21 | 23.6 | 30.5 |
The evaluated error distribution of results of table two, new time-frequency domain combination frequency deviation estimating method
| SNR | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| >5% | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| >2% | 1.2 | 0 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| >1% | 2.4 | 0.5 | 0.4 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| >0.5% | 19.9 | 14.8 | 11.1 | 7 | 3.8 | 2.3 | 0.7 | 0.6 | 0 | 0 | 0 | 0 | 0 |
| >0.1% | 80.6 | 79.5 | 75.3 | 74.1 | 68.5 | 62.9 | 61.3 | 54.1 | 51.4 | 44.6 | 37.1 | 35.5 | 28.1 |
| <0.1% | 19.5 | 20.5 | 24.7 | 25.9 | 31.5 | 37.1 | 38.7 | 45.9 | 48.6 | 55.4 | 62.9 | 64.5 | 71.9 |
It can be seen that the residual frequency deviation of the frequency deviation estimating method estimation of the present invention is more than carrier wave interval 1% from subordinate list two
Probability only has in signal-to-noise ratio 3db less than 3%, and when signal-to-noise ratio is more than or equal to 6db, frequency offset error is in 0.5% (312.5 (kHz) *
0.5%=1562.5Hz) probability below reaches 99% or more, and frequency offset estimation accuracy has large increase.
Patent of the present invention provides a kind of method carrying out offset estimation in MIMO-OFDM systems, estimates in time domain frequency deviation
On the basis of meter, SIG field is utilized and is accurately estimated in frequency domain, time-frequency domain combines the essence for improving receiving terminal offset estimation
Degree, especially in the case of low signal-to-noise ratio, estimated accuracy has greatly improved.According to the disclosed embodiment, this field skill
Art personnel can realize or using the present invention.Embodiment described above is only presently preferred embodiments of the present invention, and is not had to
To limit the present invention, all within the spirits and principles of the present invention, any modification, equivalent replacement, improvement and so on, at this
Within the protection domain of invention.
Claims (1)
1. a kind of method of MIMO-OFDM system frequency deviations estimation, for total N to MIMO-OFDM system receiversrxIt is a
The signal comprising short training sequence, long training sequence and SIG sequences that reception antenna is received carries out frequency offset estimation, special
Sign is：This approach includes the following steps：
The first step：Coarse frequency deviation delta f is calculated using the short training sequence of the signalsts；
In the first step, the short training sequence includes that several continuously repeat field, is continuously repeated using described
Field respectively calculates each reception antenna received signal
Afterwards, it carries out multiple antennas weighted average and calculates angleWherein, Ts is described continuous
The length of Repeating Field；∠ is the angle operation of calculated complex, then the coarse frequency deviation
Second step：Long training sequence frequency deviation f is calculated using the long training sequence of the signallts；
In the second step, the long training sequence includes several long training fields, utilizes the long training field
Each reception antenna received signal is calculated respectively
Afterwards, it carries out multiple antennas weighted average and calculates angleWherein, Ts2For the long instruction
The length for section of practising handwriting；The then long training sequence frequency departure
Third walks：For each SIG field in the SIG sequences, acquired respectively by following steps (1)-(3) described
The channel weights frequency domain phase deviation average value Rx_SIG_Freq_Dif of each SIG field in SIG sequences：
(1) frequency domain data of the SIG field of each reception antenna is calculated, is calculated further according to the frequency domain data
Channel equalization data Rx_SIG_Freq_rx (i)；The channel equalization data for the SIG field that each antenna is received are taken
Average frequency domain data Rx_SIG_Freq is averagely obtained, to the average frequency domain data Rx_SIG_Freq demappings and is decoded
To SIG information datas；
In the step of third walks (1), the time domain sampled data of the SIG field described in each is transported by FFT respectively
It calculates and obtains the channel equalization data Rx_SIG_Freq_rx after obtaining the frequency domain data, then channel equalized operation
(i), the channel equalization data weighted average for the SIG field that each antenna is received obtains average frequency domain dataFinally pass through BPSK demappings and convolution decoder obtains the SIG
Information data；
(2) the SIG information datas are re-started into coding and mapping generates SIG local frequency domain data Local_SIG_
Freq；
(3) according to the average frequency domain data Rx_SIG_Freq and locals the SIG frequency domain data Local_SIG_
The channel weights frequency domain phase deviation average value Rx_SIG_Freq_Dif of each nonzero value frequency point in the domains SIG is calculated in Freq；
In the step of third walks (3), pass through calculating
Rx_SIG_Freq_Dif=∑s Rx_SIG_Freq.*conj (Local_SIG_Freq)
Obtain the channel weights frequency domain phase deviation average value Rx_SIG_Freq_Dif of each nonzero value frequency point in the domains SIG；
4th step：It is calculated after the channel weights frequency domain phase deviation average value plural number of each SIG field is summed to answer
Number angle, obtains average phase deviation
5th step：According to the average phase deviationAnd the mean coefficient α of each SIG field calculates a symbol
The residual phase deviation that residual frequency deviation generates in number interval time
In 5th step,
6th step：The residual phase deviation generated according to residual frequency deviation in a symbol intervalWhen being calculated
Domain residual carrier frequency offset Δ fsig；
In 6th step,Wherein TsymbolFor the length of a symbol interval；
7th step：The estimated result of carrier wave frequency deviation is calculated, the estimated result of the carrier wave frequency deviation is the coarse frequency deviation
Δfsts, described long training sequence frequency deviation fltsWith the time domain residual carrier frequency offset Δ fsigThe sum of Δ flts+Δ
fsts+Δfsig。
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| CN106788635B (en) * | 2017-01-18 | 2020-05-26 | 深圳市极致汇仪科技有限公司 | Residual frequency offset estimation method and device suitable for tester |
| CN108199994B (en) * | 2017-12-29 | 2021-04-20 | 深圳市极致汇仪科技有限公司 | OFDM signal frequency offset estimation method and system for wireless comprehensive measurement instrument |
| CN111262805B (en) * | 2018-11-30 | 2023-01-13 | 华为技术有限公司 | Data transmission method, device and system |
| CN110611629B (en) * | 2019-09-27 | 2022-05-20 | 上海移芯通信科技有限公司 | Method and device for estimating frequency deviation and communication equipment |
| CN113452635B (en) * | 2020-03-27 | 2022-12-27 | 华为技术有限公司 | Method, station and access point for frequency offset estimation |
| CN113794535B (en) * | 2021-09-14 | 2024-04-05 | 深圳市极致汇仪科技有限公司 | Signal synchronization method compatible with punching mode, wireless signal analysis method and system |
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