CN103248591B - Based on the coarse frequency offset method of barycenter of frequency spectrum - Google Patents
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Abstract
The present invention proposes a kind of coarse frequency offset method based on barycenter of frequency spectrum, comprise the following steps: S1: receive time-domain signal and time-domain signal is divided into n group, and the fast Fourier transform of N point is carried out to obtain n group frequency domain data to the time-domain signal of each group, wherein, n is positive integer, and N is that fast Fourier transform is counted; S2: each group frequency domain data of n group frequency domain data is processed, to obtain the average value vector containing n frequency domain data log power; S3: the threshold value that Noise Background is set, and remove containing the noise in the average value vector of n frequency domain data log power according to the threshold value of Noise Background; S4: the data after removing noise are carried out cycle spinning, and calculates frequency domain center of gravity, to obtain frequency offset.According to the method for the embodiment of the present invention, owing to not needing to add pilot signal, decrease data processing amount and algorithm complex, and by estimating frequency shift (FS), make, under predetermined signal to noise ratio, to there is good estimated performance.
Description
Technical field
The present invention relates to wireless communication technology field, particularly a kind of coarse frequency offset method based on barycenter of frequency spectrum.
Background technology
In a wireless communication system, due to the frequency difference between transmitting apparatus and receiving equipment, and client device moves the impacts such as brought Doppler frequency-shift, makes to there is frequency shift (FS) between carrier frequency and the frequency of this locality.Frequency shift (FS) brings very large impact to wireless communication system, such as at OFDM (OrthogonalFrequencyDivisionMultiplexing, OFDM) in system, in frequency domain, channel is divided into many orthogonal sub-channels, the intercarrier of each subchannel keeps orthogonal, and frequency spectrum is overlapped, in this case, fractional part of frequency offset just likely destroys the orthogonality between subcarrier, produces inter-carrier interference (ICI) to cause the degradation of systematic function.Although integer frequency offset can not cause the interference between subcarrier, the cyclic shift of the frequency domain data symbols sequence that receiving terminal can be caused to recover and phase rotating, make the bit error rate of system greatly improve.So in wireless communications, in order to ensure the transmitting of data, need to estimate frequency shift (FS) and compensate, frequency deviation is estimated namely to utilize the signal that receives as observation sample to determine the frequency deviation of signal the unknown.The method that frequency deviation is estimated has a lot, in different systems, have different frequency deviation estimating methods.Traditional frequency deviation estimating method needs to add pilot signal at transmitting terminal, and receiving terminal utilizes known pilot signal to carry out frequency deviation estimation.This method due to needs add pilot frequency information, because this increasing amount of calculation and the algorithm complex of data.
Summary of the invention
Object of the present invention is intended at least solve one of above-mentioned technological deficiency.
For this reason, the object of the invention is to propose a kind of coarse frequency offset method based on barycenter of frequency spectrum.
For achieving the above object, embodiments of the invention propose a kind of coarse frequency offset method based on barycenter of frequency spectrum, comprise the following steps: S1: receive time-domain signal and described time-domain signal is divided into n group, and the fast Fourier transform of N point is carried out to obtain n group frequency domain data to the time-domain signal of each group, wherein, described n is positive integer, and N is that fast Fourier transform is counted, and is the positive integer power of 2; S2: described n group frequency domain data is processed, to obtain the average value vector containing n frequency domain data log power; S3: the threshold value that Noise Background is set, and remove described containing the noise in the average value vector of n frequency domain data log power according to the threshold value of described Noise Background; And S4: the data after removing noise are carried out cycle spinning, and calculates frequency domain center of gravity, to obtain frequency offset.
In one embodiment of the present of invention, described step S2 specifically comprises:
According to described n group frequency domain data, to obtain the log power of each element in each group; And
According to the log power of each element in each group described, to obtain the average value vector containing n frequency domain data log power.
In one embodiment of the present of invention, described step S3 comprises further: when the value in described average value vector is less than the threshold value of described Noise Background, the value in described average value vector is set to 0; And when the value in described average value vector is not less than the threshold value of described Noise Background, do not change the value in described average value vector.
In one embodiment of the present of invention, described step S4 comprises further: the data after described removal noise are carried out cycle spinning, to obtain new vector; Described vector is newly processed, to obtain described frequency domain center of gravity; And process according to described frequency domain center of gravity, to obtain described frequency offset.
In one embodiment of the present of invention, described translational movement is N/2 point, and wherein, N is that fast Fourier transform is counted, and is the positive integer power of 2.
In one embodiment of the present of invention, described frequency domain center of gravity is obtained by following formula, and described formula is,
wherein, f is frequency domain center of gravity, q
ifor i-th element in new vector, q
kfor a kth element in new vector, i, k are positive integer, and N is that fast Fourier transform is counted, and are the positive integer power of 2.
In one embodiment of the present of invention, described frequency offset is obtained by following formula, and described formula is, Δ f=| (N+1)/2-f|, and wherein, Δ f is frequency offset, and N is that fast Fourier transform is counted, and be the positive integer power of 2, f is frequency domain center of gravity.
According to the method for the embodiment of the present invention, owing to not needing to add pilot signal, decrease data processing amount and algorithm complex, and by estimating frequency shift (FS), make, under predetermined signal to noise ratio, to there is good estimated performance.
The aspect that the present invention adds and advantage will part provide in the following description, and part will become obvious from the following description, or be recognized by practice of the present invention.
Accompanying drawing explanation
The present invention above-mentioned and/or additional aspect and advantage will become obvious and easy understand from the following description of the accompanying drawings of embodiments, wherein:
Fig. 1 is according to an embodiment of the invention based on the flow chart of the coarse frequency offset method of barycenter of frequency spectrum; And
Fig. 2 utilizes barycenter of frequency spectrum to the performance chart of TD-LTE uplink frequency bias estimation according to an embodiment of the invention.
Embodiment
Be described below in detail embodiments of the invention, the example of embodiment is shown in the drawings, and wherein same or similar label represents same or similar element or has element that is identical or similar functions from start to finish.Being exemplary below by the embodiment be described with reference to the drawings, only for explaining the present invention, and can not limitation of the present invention being interpreted as.
Fig. 1 is according to an embodiment of the invention based on the flow chart of the coarse frequency offset method of barycenter of frequency spectrum.As shown in Figure 1, according to the coarse frequency offset method based on barycenter of frequency spectrum of the embodiment of the present invention, comprise the following steps:
Step 101, receive time-domain signal and time-domain signal is divided into n group, and carrying out the fast Fourier transform of N point to obtain n group frequency domain data to the time-domain signal of each group, wherein, n is positive integer, and N is that fast Fourier transform is counted, and is the positive integer power of 2.
Particularly, receive time-domain signal and the time-domain signal data received are divided into n group, and each group data being carried out to the fast Fourier transform of N point respectively, to obtain n group frequency domain data.
Step 102, processes each group frequency domain data of n group frequency domain data, to obtain the average value vector containing n frequency domain data log power.
Specifically, for n group frequency domain data A=(A
1, A
2..., A
n), wherein, A
i=(a
i1, a
i2..., a
iN) (i=1,2 ..., n) be the column vector containing N number of data.First each group A is obtained
iin the power B of each element
i, B
i=(b
i1, b
i2..., b
iN) (i=1,2 ..., n).Then, according to power B
iin each element utilize formula c
ij=10log10 (b
ij) (j=1,2 ..., N) and calculate its log power, transform into the log power C in units of dB
i, C
i=(c
i1, c
i2..., c
iN) (i=1,2 ..., n).Afterwards, according to log power C
i(i=1,2 ..., n) utilize formula
calculate, to obtain the average value vector P of frequency domain data log power, P=(p
1, p
2... p
n).
Step 103, arranges the threshold value of Noise Background, and removes containing the noise in the average value vector of n frequency domain data log power according to the threshold value of Noise Background.
Particularly, arrange the threshold value of Noise Background, wherein, this threshold value can be determined as the case may be.Then when the value in average value vector is less than the threshold value of Noise Background, the value in average value vector is set to 0, otherwise does not change the value in average value vector, thus generate vectorial R, the R=(r after denoising
1, r
2..., r
n).
Data after removing noise are carried out cycle spinning, and are calculated frequency domain center of gravity, to obtain frequency offset by step 104.
Specifically, the data after removal noise and vectorial R are carried out cycle spinning N/2 point, to obtain new vectorial Q, Q=(q
1, q
2..., q
n).Then, according to vectorial Q, formula is utilized
calculate, to obtain barycenter of frequency spectrum f, wherein, q
ifor i-th element in vector, q
kfor the element of kth in vector, i, k are positive integer, and N is that fast Fourier transform is counted, and are the positive integer power of 2.
Finally, according to frequency domain center of gravity f by formula Δ f=| (N+1)/2-f|, calculate, to obtain Frequency offset estimation Δ f, wherein, Δ f is frequency offset, and N is that fast Fourier transform is counted, and be the positive integer power of 2, f is frequency domain center of gravity.
According to the method for the embodiment of the present invention, owing to not needing to add pilot signal, decrease data processing amount and computation complexity, and by estimating frequency shift (FS), make, under predetermined signal to noise ratio, to there is good estimated performance.
In order to verify estimation effect of the present invention, carry out following test.For TD-LTE up link in the present invention, its basic parameter arranges as shown in table 1.
| Parameter | Parameter value |
| Bandwidth | 20MHz |
| Packet count | 45groups |
| Number of users | 1 |
| Channel type | PedA |
| Resourse Distribute | 100RBs |
| Launching Model | 1x1 |
| Frequency shift (FS) | 15×12KHz |
| Simulated lengths | 20000subframes |
Table 1
Fig. 2 utilizes barycenter of frequency spectrum to the performance chart of TD-LTE uplink frequency bias estimation according to an embodiment of the invention.As shown in Figure 2, as signal to noise ratio snr=0:2:30dB, as can be seen from Figure 2, when signal to noise ratio is lower, the root-mean-square error that frequency deviation is estimated is comparatively large, but when signal to noise ratio is more than 8dB, root-mean-square error, all within 0.3 unit, has good estimated performance.
Although illustrate and describe embodiments of the invention above, be understandable that, above-described embodiment is exemplary, can not be interpreted as limitation of the present invention, those of ordinary skill in the art can change above-described embodiment within the scope of the invention when not departing from principle of the present invention and aim, revising, replacing and modification.
Claims (7)
1., based on a coarse frequency offset method for barycenter of frequency spectrum, it is characterized in that, comprise the following steps:
S1: receive time-domain signal and described time-domain signal is divided into n group, and the fast Fourier transform of N point is carried out to obtain n group frequency domain data to the time-domain signal of each group, wherein, described n is positive integer, N is that fast Fourier transform is counted, and N is the positive integer power of 2;
S2: described n group frequency domain data is processed, to obtain the average value vector containing n frequency domain data log power;
S3: the threshold value that Noise Background is set, and remove described containing the noise in the average value vector of n frequency domain data log power according to the threshold value of described Noise Background; And
S4: the data after removing noise are carried out cycle spinning, and calculates frequency domain center of gravity, to obtain frequency offset.
2., as claimed in claim 1 based on the coarse frequency offset method of barycenter of frequency spectrum, it is characterized in that, described step S2 specifically comprises:
According to described n group frequency domain data, to obtain the log power of each element in each group; And
According to the log power of each element in each group described, to obtain the average value vector containing n frequency domain data log power.
3., as claimed in claim 1 based on the coarse frequency offset method of barycenter of frequency spectrum, it is characterized in that, described step S3 comprises further:
When the value in described average value vector is less than the threshold value of described Noise Background, the value in described average value vector is set to 0; And
When the value in described average value vector is not less than the threshold value of described Noise Background, do not change the value in described average value vector.
4., as claimed in claim 1 based on the coarse frequency offset method of barycenter of frequency spectrum, it is characterized in that, described step S4 specifically comprises:
Data after described removal noise are carried out cycle spinning, to obtain new vector;
Described vector is newly processed, to obtain described frequency domain center of gravity; And
Process according to described frequency domain center of gravity, to obtain described frequency offset.
5., as claimed in claim 4 based on the coarse frequency offset method of barycenter of frequency spectrum, it is characterized in that, the amount of described cycle spinning is N/2 point, and wherein, N is that fast Fourier transform is counted, and N is the positive integer power of 2.
6., as claimed in claim 4 based on the coarse frequency offset method of barycenter of frequency spectrum, it is characterized in that, described frequency domain center of gravity is obtained by following formula, and described formula is,
Wherein, f is frequency domain center of gravity, q
ifor i-th element in new vector, q
kfor a kth element in new vector, i, k are positive integer, and N is that fast Fourier transform is counted, and N is the positive integer power of 2.
7., as claimed in claim 4 based on the coarse frequency offset method of barycenter of frequency spectrum, it is characterized in that, described frequency offset is obtained by following formula, and described formula is,
Δf＝|(N+1)/2-f|，
Wherein, Δ f is frequency offset, and N is that fast Fourier transform is counted, and N is the positive integer power of 2, and f is frequency domain center of gravity.
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| CN111654308B (en) * | 2020-04-30 | 2021-05-28 | 中国科学院上海微系统与信息技术研究所 | Precision frequency offset estimation method for burst spread spectrum weak signal |
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| US8064553B2 (en) * | 2008-04-23 | 2011-11-22 | Newport Media, Inc. | Coarse frequency offset estimation in ISDB receivers |
| CN102694763A (en) * | 2012-05-31 | 2012-09-26 | 重庆邮电大学 | Method for assessing integer frequency offset of TD-LTE system |
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| US8064553B2 (en) * | 2008-04-23 | 2011-11-22 | Newport Media, Inc. | Coarse frequency offset estimation in ISDB receivers |
| CN102694763A (en) * | 2012-05-31 | 2012-09-26 | 重庆邮电大学 | Method for assessing integer frequency offset of TD-LTE system |
Non-Patent Citations (1)
| Title |
|---|
| "A LOW-COMPLEXITY FREQUENCY-OFFSET ESTIMATION ALGORITHM FOR THE MEDICAL BODY AREA NETWORK";Ning Li 等;《Proceedings of 2012 3rd IEEE International Conference on Network Infrastructure and Digital Content》;20120921;第554-557页 * |
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