CN107979454A - A kind of OFDMA distributed modes downlink comb spectrum rapid extracting method - Google Patents
A kind of OFDMA distributed modes downlink comb spectrum rapid extracting method Download PDFInfo
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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
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0003—Two-dimensional division
- H04L5/0005—Time-frequency
- H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
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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
- H04L5/0037—Inter-user or inter-terminal allocation
- H04L5/0041—Frequency-non-contiguous
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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
- H04L5/0091—Signaling for the administration of the divided path
- H04L5/0094—Indication of how sub-channels of the path are allocated
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Abstract
The present invention provides a kind of OFDMA distributed modes downlink comb spectrum rapid extracting method.The present invention extracts the quick problem of implementation of L × M pectination frequency point for the N number of time-domain received signal of system, using discrete Fourier transform, that is, existsLSame position starts in a every section of sub-bandMThe data of carrying are extracted in a continuous subcarrier, will using decomposition method is convertedNA input data is decomposed intoLA length isPData block, to every piece respectively carry out DFT computings, simplify this using the division base cutting method based on decimation in timeLThe DFT computings of block number evidence, by the way that the extra twiddle operation brought by output frequency displacement is distributed on the twiddle factor of computings at different levels in itself, and the butterfly computation cut on some grades, so as to realize the rapid extraction to all pectination frequency points for distributing to the user in user terminal, computational complexity is substantially reduced.The present invention can be applied in the field such as signal processing or image procossing, realize that discrete Fourier transform pectination frequency point extracts.
Description
Technical field
The present invention relates to signal of communication process field, and in particular to one kind is directed to Orthogonal Frequency Division Multiple Access (OFDMA) communication system
The rapid extracting method of comb spectrum when distributed sub-carrier allocation mode downlink of uniting user terminal receives demodulation.
Background technology
Orthogonal Frequency Division Multiple Access (OFDMA) is the mainstream of the mobile telecommunication system down link such as LTE, 4G and IEEE 802.16m
Multiple Access scheme.Whole frequency band is divided into many subcarriers by OFDMA, and frequency selective fading channels are converted into some flat decline
Begin channel, so as to be reasonably resistant to the frequency selective fading in wireless mobile environment.By to different user point
With different subcarriers, subcarrier meets mutually orthogonal between user, can at the same time access system.OFDMA can use two seeds to carry
Ripple allocation model：It is centralized and distributed.Some continuous subcarriers are distributed to a user by centralization, are distributed in distributed
The subcarrier of one user is distributed to whole frequency band, so as to form comb frequency spectrum.Centralization can reduce the difficulty of channel estimation,
But the frequency diversity gain that this mode obtains is smaller, user's average behavior is slightly poor；And distribution then can be using between subcarrier
Frequency selective fading correlation is weaker between interval farther out causes, so as to obtain stronger diversity gain, Yong Huping
Equal better performances, but the estimation of this mode lower channel is complex.Two ways can flexibly be selected according to actual conditions.This
Patent mainly studies pectination when user terminal receives demodulation in ofdma communication system distributed sub-carrier allocation mode downlink
The extraction problem of spectrum.Current main stream approach is using the Fast Fourier Transform (FFT) method FFT extractions such as conventional base 2 or split-radix
The data carried on all subcarriers, the present invention realize the data on pectination frequency point to being cut in conventional FFT methods
Rapid extraction.
The content of the invention
The shortcomings that it is an object of the invention to improve the prior art and deficiency, there is provided one kind is directed to Orthogonal Frequency Division Multiple Access
(OFDMA) rapid extraction of comb spectrum when communication system distributed sub-carrier allocation mode downlink user terminal receives demodulation
Method.
Assuming that the total subcarrier number of system is N, it is P (P=2 that all subcarriers, which are divided into length,m) L blocks, i.e. N=L ×
P, each user same position in every piece of P carrier wave start to take continuous M (M=2d<P) a subcarrier, subscriber signal into
Comb frequency spectrum, user terminal, which receives processing, only need to extract the data distributed to and carried on its L × M subcarrier, its minor
Data on carrier wave are unrelated with the user without extraction.Current method is using in quick Fu such as conventional base 2 or split-radix
Leaf transformation method (FFT) extracts the data carried on all subcarriers, and the present invention is realized to being cut in conventional FFT methods
The rapid extraction of data on required frequency point；Limitation P and M is the situation of 2 power.The present invention is decomposed based on conversion and butterfly diagram
Cutting realizes the rapid solving of DFT comb spectrums.Specific method is that N number of input data is decomposed into L using decomposition method is converted
A length carries out DFT computings respectively for the block of P points, is simplified using the division base cutting method based on decimation in time DIT and calculates this L
A length be P DFT block, by by the extra twiddle operation brought by output frequency displacement be distributed to the rotation of computings at different levels in itself because
On son, and the butterfly computation cut on some grades, rapid computations method is realized, so that in user terminal realization pair
The rapid extraction of all pectination frequency points of the user is distributed to, greatly reduces computational complexity.
Specifically, to N number of input data [x (0), x (1), x (2) ..., x (N-1)], its discrete Fourier transform is calculated
Pectination exports；The N points DFT for remembering N number of input data is [X (0), X (1), X (2) ..., X (N-1)], by N number of data of output point
The L blocks for being P for length, if certain user occupies the M continuous frequency points from k-th position to K+M-1 positions in every piece；To this
For user L × M total output data of L blocks be denoted as [X (K), X (K+1) ..., X (K+M-1)；X(P+K),X(P+K+1),…,
X(P+K+M-1)；…；X((L-1)P+K),X((L-1)P+K+1),…,X((L-1)P+K+M-1)]；Especially, it is every in the present invention
M data of arbitrary continuation are also the continuous situation of circumferential cycle including this M data in block output data, i.e., in every piece of output
End to end M data fall within situation about need to consider in data；Input data is utilized conversion decomposition side by the technical program
Formula is equally divided into the L blocks that length is P, and r blocks are denoted as [xr-1(0),xr-1(1),…,xr-1(P-1)], r=1 ..., L；Every piece
Calculate and realized using hierarchical approaches, every piece of input data one shares m grades, i.e. P=2m, wherein there are d grades of computings to cut, i.e. M
=2d；The output of t grades of calculating of r blocks is denoted as [x(r-1),t(0),x(r-1),t(1),…,x(r-1),t(P-1)], t=1~m, its
In t grades of output be t+1 grade of input, m grades of preceding M continuous datas exported of r blocks are the operation results of the block；
M data of arbitrary continuation in every piece of required output data, output is changed to by its cyclic shift movement to the left K
The the 0th Dao M-1 of end；According to the property of discrete Fourier transform, K inputs being equivalent to every piece of ring shift left of output terminal
Hold each data to be rotated, i.e., frequency displacement twiddle factor is multiplied by n-th of input dataN=0 ..., P-1；By the frequency displacement
Twiddle factorIt is distributed on division based method butterfly diagram original twiddle factors at different levels, rapid solving piecemeal DFT comb spectrums
Output, so as to fulfill the rapid extraction of all pectination frequency points to distributing to user, specifically includes following steps：
Step 1. to it is N number of when input data, using conversion decompose mode be divided into L length for P block；
Step 2. calculates the total series m of split-radix butterfly diagram per block number evidence and need not cut to the block that L length is P
Series d, and the sequence number of every piece of input data is subjected to bit backward；
Step 3. calculates 2 butterfly of decimation in time base all in the 1st grade every piece to the block that L length is P；
Step 4. calculates the 2nd grade every piece to all decimation in time split-radix butterflies in d-th level to the block that L length is P
Shape；
Step 5. calculates every piece d+1 grades level-one m to the end to the block that L length is P according to division base cutting method
The split-radix butterfly of all cuttings of level；
The L length that step 6. obtains above-mentioned steps is that the output block of P is recombinated, and obtains the defeated of required pectination
Go out.
Further, in step 1, the input to N points, by sequence { x (Ln1)},n1=0 ..., P-1 is mapped to first long
Spend in the block for P, be denoted as x respectively0(0),x0(1),…,x0(P-1)；By sequence { x (Ln1+1)},n1=0 ..., P-1 is mapped to
In the block that second length is P, x is denoted as respectively1(0),x1(1),…,x1(P-1)；…；By sequence { x (Ln1+L-1)},n1=
0 ..., P-1 are mapped in the block that l-th length is P, are denoted as are denoted as x respectively respectivelyL-1(0),xL-1(1),…,xL-1(P-1)。
In step 2, the series total to the input DIT split-radix butterfly diagrams of P points in every pieceM point arbitrary continuations
Output, it is not necessary to the series of cuttingThe series for needing to cut is m-d.Input { x to r blocksr-1(0),xr-1(1),
xr-1(2),…,xr-1(P-1) } sequence number carries out bit backward, particularly as being by 0,1 ..., this P sequence number of P-1 with m levels two into
Tabulation is shown, then these binary numerals are overturn, and is expressed as new decimal system sequence number.According to new decimal system sequence number weight
The order of element in new sort list entries, and it is denoted as { x(r-1)0(0),x(r-1)0(1),…,x(r-1)0(P-1) }, this will be r
The input of the 1st grade of computing of block.
In step 3,2 butterfly of decimation in time base all in the 1st grade of every piece in the block that L length is P is calculated respectively.It is right
For r blocks, 2 butterfly computation of decimation in time base all in the 1st grade is performed.The calculation formula of 2 butterfly of decimation in time base can
It is expressed as：
Wherein p and q=p+1 represents the sequence number of the upper lower node of butterfly unit computing.Only p=2 × 4a-2+b×4a+1The base at place
2 butterflies need to calculate, wherein a=0, and 1,2 ...；B=0,1,2 ...；Make p ＜ P-1.
In step 4, the 2nd grade every piece is calculated respectively to all decimation in time split-radix butterflies in d-th level.For r blocks
For, the 2nd grade to d-th level performs decimation in time split-radix butterfly computation.T grades where t is represented in split-radix butterfly, NiRepresent
The size of twiddle factor block where split-radix, wherein Ni=2t, 2≤t≤m.Input terminal frequency displacement twiddle factor WP- Kn is distributed to
Twiddle factor after 2nd grade to the original twiddle factor of d-th level is
Wherein
Q (u)=(u-K) 2(m-t), u=0,1 ..., 2t-2- 1, t=2 ..., m. formula (3)
Especially, as u=0, φ (u) and φ (3u) is respectively first of twiddle factor block where t grades of split-radix
The twiddle factor of split-radix butterfly；During u=1, φ (u) and φ (3u) are respectively the of t grade split-radix place twiddle factor blocks
The twiddle factor of two split-radix butterflies, and so on.The calculation formula of the split-radix butterfly of decimation in time is represented by:
Here j is imaginary unit,
N=Ni×4a+1-Ni+2b×Ni×4a+1+ u formula (5)
Wherein a=-1,0,1,2 ...；B=0,1,2 ...；U=0,1 ..., 2t-2- 1 so that n ＜ P-3Ni/4。
Complete split-radix butterfly is carried out according to this formula to the 2nd grade to d-th level of all decimation in time split-radix butterflies
Shape computing.
In step 5, the split-radix butterfly of every piece d+1 grades all cuttings of m grades of level-one to the end is calculated respectively.For
For r blocks, according to the division base cutting method of decimation in time, the split-radix of d+1 grades of m grades of level-ones to the end is used
The butterfly computation that the mode that output is cut is cut, specific cutting method are：
In d+1 grades, the first two output of decimation in time split-radix butterfly is only calculated, cuts decimation in time split-radix
Latter two output of butterfly, the output of this first two is xt(n) withT grades where t is represented in split-radix butterfly, NiTable
Show the size of the twiddle factor block where split-radix, wherein Ni=2d+1, frequency displacement twiddle factorIt was distributed to d+1 grades originally
Twiddle factor after twiddle factor φ (u) and φ (3u) calculated by formula (2) and formula (3).N is calculated by formula (5).This
The calculation formula that step cuts split-radix butterfly is represented by:
D+2 grades of m grades of level-ones to the end it is at different levels in, for every level-one each twiddle factor block calculate before M
Split-radix butterfly, and each split-radix butterfly only calculates first output.Wherein Ni=2t, t=d+2 ..., m, frequency displacement rotation
The factorIt is distributed to the d+2 grades of twiddle factor φ (u) after m grades of original twiddle factors of level-one and φ (3u) to the end
Calculated by formula (2) and formula (3), simply the value range of u is u=0,1 ..., M-1.This step cuts the meter of split-radix butterfly
Formula is calculated to be represented by:
Wherein, n is calculated by formula (5), and simply the value range of u is u=0,1 ..., M-1.
In step 6, the block that L length is P is subjected to reorganization operation, obtains the output of our required pectinations.It is L long
Spend in the block for P, we go out the output of our needs using preceding M data recombination in every piece, are obtained using following formula final required
Want comb spectrum output [X (K), X (K+1) ..., X (K+M-1)；X(P+K),X(P+K+1),…,X(P+K+M-1)；…；X((L-
1)P+K),X((L-1)P+K+1),…,X((L-1)P+K+M-1)]。
Compared with prior art, the present invention having the following advantages that and beneficial effect：
1st, the present invention provides a kind of Orthogonal Frequency Division Multiple Access (OFDMA) communication system distributed sub-carrier allocation pattern downlink chain
The rapid extracting method of comb spectrum when road user terminal receives demodulation, can be equidistant continuous comb spectrum to the output of DFT
Quick evaluation is carried out, will be big relative to FFT methods such as conventional base 2 and the split-radix that must obtain all point values completely
Amount reduces time complexity.
2nd, the present invention proposes that N point DFT are decomposed into more fritter by way of converting and decomposing carries out DFT computings respectively, separately
The rotation that the frequency displacement of DFT computing output terminals each piece outer produces input terminal, it is each to be cleverly distributed to decimation in time DIT butterfly diagrams
On the original twiddle factor of level, and the output for combining split-radix is cut, and the complexity of computing is greatly reduced, in signal processing
Or the field such as image procossing needs the value for asking DFT in comb spectrum output point, and to time complexity it is more demanding when,
This method can be used to replace traditional FFT computings.
Brief description of the drawings
Fig. 1 is OFDMA distributed sub-carrier allocations mode downlink subscriber signal pectination spectrogram of the present invention.
Fig. 2 is decimation in time base 2 of the present invention and split-radix butterfly diagram.
Fig. 3 is two kinds of cutting butterfly diagrams of decimation in time split-radix of the present invention.
Fig. 4 is 16 decimation in time DIT split-radix butterfly diagrams of the present invention.
Fig. 5 is the flow diagram of comb frequency spectrum of the present invention output extraction.
Embodiment
With reference to embodiment and attached drawing, the present invention is described in further detail, but embodiments of the present invention are unlimited
In this.
Assuming that the total subcarrier number of an Orthogonal Frequency Division Multiple Access ofdma communication system is N number of, all subcarriers are divided into length
Spending the L blocks for P, each user is taken in every piece of P carrier wave from k-th position to M continuous data of K+M-1 positions,
Subscriber signal is into comb frequency spectrum, as shown in Figure 1.User terminal, which receives to handle only extract, distributes to its L × M subcarrier
The data of upper carrying, the data on its remaining sub-carriers are unrelated with the user without extraction.
Comb spectrum is fast when ofdma communication system distributed sub-carrier allocation mode downlink user terminal receives demodulation
Fast extracting method, specifically with N=48 points, factoring L=3, block length P=16, every piece continuously exports M=since K=6 points
Illustrate, comprise the following steps exemplified by 4 points：
N points, are mapped in the block that L length is P by input of the step 1. to N points using the mode that conversion is decomposed.
Further, in step 1, the input to N points, by sequence { x (Ln1)},n1=0 ..., P-1 is mapped to first long
Spend in the block for P and be denoted as x respectively0(0),x0(1),…,x0(P-1)；By sequence { x (Ln1+1)},n1=0 ..., P-1 is mapped to
X is denoted as respectively in the block that two length are P1(0),x1(1),…,x1(P-1)；…；By sequence { x (Ln1+L-1)},n1=0 ...,
P-1 is mapped to be denoted as respectively in the block that l-th length is P is denoted as x respectivelyL-1(0),xL-1(1),…,xL-1(P-1)。
Further, in step 1, as (a) in Fig. 5 arrives (b) process, by x (0), x (3), x (6), x (9) ..., x
(45) it is mapped in the block that first length is 16 and is denoted as x0(0),x0(1),x0(2),x0(3),…,x0(15)；By x (1), x
(4), x (7), x (10) ..., x (46) is mapped in the block that second length is 16 and is denoted as x1(0),x1(1),x1(2),x1
(3),…,x1(15)；By x (2), x (5), x (8), x (11) ..., x (47) is mapped in the block that the 3rd length is 16 and is denoted as x2
(0),x2(1),x2(2),x2(3),…,x2(15)。
The series that step 2. needs to cut to the block that L length is P, calculating per the total sum of series of block splitting base butterfly diagram, and
Every piece of input point is subjected to bit backward.
Further, in step 2, the series total to the input DIT split-radix butterfly diagrams of P points in every piece isM
The output of point arbitrary continuation, it is not necessary to which the series of cutting isThe series for needing to cut is m-d.Input to r blocks
{xr-1(0),xr-1(1),xr-1(2),…,xr-1(P-1) } sequence number carries out bit backward, particularly as being by 0,1 ..., this P of P-1
A sequence number is overturn with m grades of binary representations, then by these binary numerals, and is expressed as new decimal system sequence number.According to
The order of element in new decimal system sequence number rearrangement list entries, and it is denoted as { x(r-1)0(0),x(r-1)0(1),…,x(r-1)0
(P-1) }, this by be the 1st grade of computing of r blocks input.
Further, in step 2, explained with the first 16 point data in the block, as shown in Fig. 4 16 points of input M
The decimation in time DIT butterfly diagrams of=4 arbitrary continuation output.16 point DIT butterflies share 4 grades, it is not necessary to which the series of cutting is the 1st
Level is with the 2nd grade, it is necessary to which the series cut is 3rd level and the 4th grade.This 16 input points are subjected to bit backward, according still further to new
For decimal system sequence number to input value adjustment order, it is respectively x to obtain corresponding new decimal system sequence number00(0) (=x0(0)),x00(1)
(=x0(8)),x00(2) (=x0(4)),x00(3) (=x0(12)),x00(4) (=x0(2)),x00(5) (=x0(10)),x00(6)
(=x0(6)),x00(7) (=x0(14)),x00(8) (=x0(1)),x00(9) (=x0(9)),x00(10) (=x0(5)),x00
(11) (=x0(13)),x00(12) (=x0(3)),x00(13) (=x013(11)),x00(14) (=x0(7)),x00(15) (=x0
(15))。
Step 3. calculates 2 butterfly of decimation in time base all in the 1st grade every piece to the block that L length is P.
Further, in step 3,2 butterfly of decimation in time base all in the 1st grade every piece is calculated respectively, just for r blocks
For, perform 2 butterfly computation of decimation in time base all in the 1st grade.The calculation formula of 2 butterfly of decimation in time base is represented by：
Wherein p and q=p+1 represents the sequence number of the upper lower node of butterfly unit computing.Only p=2 × 4a-2+b×4a+1Place
2 butterfly of base need to calculate, wherein a=0,1,2 ...；B=0,1,2 ...；Make p ＜ P-1.
Further, in step 3,2 butterfly of decimation in time base all in the 1st grade every piece is calculated respectively, just for the 1st
For block, according to the calculation formula of p, x in Fig. 400(0) and x00(1),x00(4) and x00(5),x00(6) and x00(7)、x00(8) and
x00(9)、x00(12) and x00(13) two input terminals of 2 butterfly of base are corresponded to respectively.During K=6, after 2 butterfly combination deviation ratio of base
Twiddle factor be (- 1)6=1, the output valve of each 2 butterfly of base of the first order can be calculated according to formula (1).
Step 4. calculates the 2nd grade every piece to all decimation in time split-radix butterflies in d-th level to the block that L length is P
Shape.
Further, in step 4, the 2nd grade every piece is calculated respectively to all decimation in time split-radix butterflies in d-th level,
With regard to for r blocks, the 2nd grade to d-th level performs decimation in time split-radix butterfly computation.Where t is represented in split-radix butterfly
T grades, NiThe size of twiddle factor block where expression split-radix, wherein Ni=2t, 2≤t≤m.Input terminal frequency displacement twiddle factorThe twiddle factor being distributed to after the 2nd grade to the original twiddle factor of d-th level
Wherein
Q (u)=(u-K) 2(m-t), u=0,1 ..., 2t-2- 1, t=2 ..., m. formula (3)
Especially, as u=0, φ (u) and φ (3u) is respectively first of twiddle factor block where t grades of split-radix
The twiddle factor of split-radix butterfly；During u=1, φ (u) and φ (3u) are respectively the of t grade split-radix place twiddle factor blocks
The twiddle factor of two split-radix butterflies, and so on.The calculation formula of the split-radix butterfly of decimation in time is represented by:
Here, j is imaginary unit,
N=Ni×4a+1-Ni+2b×Ni×4a+1+ u formula (5)
Wherein a=-1,0,1,2 ...；B=0,1,2 ...；U=0,1 ..., 2t-2- 1 so that n ＜ P-3Ni/4。
Complete split-radix butterfly is carried out according to this formula to the 2nd grade to d-th level of all decimation in time split-radix butterflies
Shape computing.
Further, in step 4, the 2nd grade every piece is calculated respectively to all decimation in time split-radix butterflies in d-th level
Shape, with regard to for the 1st piece, the DIT split-radix butterfly diagrams of 16 points of inputs, 4 arbitrary continuation output, the only second level is entirely complete
Decimation in time divide base butterfly, the size N of the twiddle factor block where the split-radix of the second leveliThe value of=4, n are according to formula
(5) respectively 0,8,12, u=0 can be drawn.Corresponding twiddle factor is by formula (2) and formula (3) when n is 0,8,12WithThe output of each split-radix butterfly of the second level can be according to formula at this time
(4) calculate.
Step 5. calculates every piece d+1 grades level-one m to the end to the block that L length is P according to division base cutting method
The split-radix butterfly of all cuttings of level.
Further, in step 5, the split-radix of every piece d+1 grades all cuttings of m grades of level-one to the end is calculated respectively
Butterfly, with regard to for r blocks, according to the division base cutting method of decimation in time, to d+1 grades of m grades of level-ones to the end
The butterfly computation that split-radix is cut by the way of output is cut, specific cutting method are：In d+1 grades, only
The first two output of decimation in time split-radix butterfly is only calculated, latter two output of decimation in time split-radix butterfly is cut, before this
Two outputs are xt(n) withT grades where t is represented in split-radix butterfly, NiRepresent split-radix where rotation because
The size of sub-block, wherein Ni=2d+1, frequency displacement twiddle factorThe rotation being distributed to after d+1 grades of original twiddle factors
Factor φ (u) and φ (3u) is calculated by formula (2) and formula (3).N is calculated by formula (5).This step cuts the meter of split-radix butterfly
Formula is calculated to be represented by:
D+2 grades of m grades of level-ones to the end it is at different levels in, for every level-one each twiddle factor block calculate before M
Split-radix butterfly, and each split-radix butterfly only calculates first output.Wherein Ni=2t, t=d+2 ..., m, frequency displacement rotation
The factorIt is distributed to the d+2 grades of twiddle factor φ (u) after m grades of original twiddle factors of level-one and φ (3u) to the end
Calculated by formula (2) and formula (3), simply the value range of u is u=0,1 ..., M-1.This step cuts the meter of split-radix butterfly
Formula is calculated to be represented by:
Wherein, n is calculated by formula (5), and simply the value range of u is u=0,1 ..., M-1.
Further, in step 5, every piece d+1 grades m grades of level-ones to the end are calculated according to division base cutting method
The split-radix butterfly of all cuttings.With regard to for first piece, 3rd level and the 4th grade of split-radix are using output cutting method
The butterfly computation cut, concrete mode：In 3rd level, the first two output of decimation in time split-radix butterfly is only calculated.
Twiddle factor block size where the split-radix of 3rd level is Ni=8, the value of n, as u=0, n=can be drawn according to formula (5)
0；As u=1, n=1.Therefore the output after two of split-radix butterfly cut is respectively x03(0) and x03(2), x03(1) and x03
(3).Export as x03(0) and x03(2) twiddle factor of butterfly isWithExport as x03
(1) and x03(3) twiddle factor of butterfly is by formula (2) and formula (3)WithProfit
The first two that 3rd level split-radix butterfly can be calculated with formula (6) exports.And at the 4th grade, only calculate decimation in time split-radix butterfly
First output of shape.The size N of twiddle factor block where wherein the 4th grade of split-radixi=16, in the 4th grade, according to formula
(5) value of n can be drawn, as u=0, n=0, corresponding output is x04(0)；As u=1, n=1, corresponding output is x04
(1)；As u=2, n=2, corresponding output is x04(2)；As u=3, n=3, corresponding output is x04(3).By formula (2) with
Formula (3), exports as x04(0) twiddle factor of butterfly isWithExport as x04(1)
The twiddle factor of butterfly isWithExport as x04(2) twiddle factor of butterfly isWithExport as x04(3) twiddle factor of butterfly isWithFirst output of the 4th grade of 4 split-radix butterfly can be calculated using formula (7).Other all outputs
All it is not have to calculate.
The block that L length is P is carried out reorganization operation by step 6., obtains the output of our required pectinations.
Further, in step 6, the block that L length is P is subjected to reorganization operation, obtains our required pectinations
Output.In the block that L length is P, we go out the output of our needs using preceding M data recombination in every piece, are asked using following formula
Go out final required comb spectrum output [X (K), X (K+1) ..., X (K+M-1)；X(P+K),X(P+K+1),…,X(P+K+M-
1)；…；X((L-1)P+K),X((L-1)P+K+1),…,X((L-1)P+K+M-1)].
Above-described embodiment is the preferable embodiment of the present invention, but embodiments of the present invention and from above-described embodiment
Limitation, other any Spirit Essences without departing from the present invention with made under principle change, modification, replacement, combine, simplification,
Equivalent substitute mode is should be, is included within protection scope of the present invention.
Claims (7)
1.OFDMA distributed mode downlink comb spectrum rapid extracting methods, it is characterised in that：In ofdma communication system point
In cloth subcarrier assignment patterns downlink, it is assumed that the total subcarrier number of system is N number of, and all subcarriers are divided into length and are
The L blocks of P, each user same position in every piece of P carrier wave start to take continuous M subcarrier, and subscriber signal is into pectination
Frequency spectrum, user terminal, which receives processing, only need to extract the data distributed to and carried on its L × M subcarrier, its remaining sub-carriers
On data it is unrelated with the user without extraction；To being cut in conventional FFT methods, realize needed on frequency point data it is fast
Speed extraction, limitation P and M are the situation of 2 power；
To N number of input data [x (0), x (1), x (2) ..., x (N-1)], the pectination output of its discrete Fourier transform is calculated；Note
The N points DFT of N number of input data is [X (0), X (1), X (2) ..., X (N-1)], and N number of data of output are divided into the L that length is P
Block, if certain user occupies the M continuous frequency points from k-th position to K+M-1 positions in every piece；The L blocks for the user
L × M total output data be denoted as [X (K), X (K+1) ..., X (K+M-1)；X(P+K),X(P+K+1),…,X(P+K+M-
1)；…；X((L-1)P+K),X((L-1)P+K+1),…,X((L-1)P+K+M-1)]；The M of arbitrary continuation in every piece of output data
A data are also the continuous situation of circumferential cycle including this M data, i.e., the end to end M data in every piece of output data
Fall within situation about need to consider；Input data is equally divided into the L blocks that length is P using isolation is converted, r blocks are denoted as
[xr-1(0),xr-1(1),…,xr-1(P-1)], r=1 ..., L；Every piece of calculating is using hierarchical approaches realization, every piece of input data
One is m grades shared, i.e. P=2m, wherein there are d grades of computings to cut, i.e. M=2d；The output of t grades of calculating of r blocks is denoted as
[x(r-1),t(0),x(r-1),t(1),…,x(r-1),t(P-1)], t=1~m, wherein t grades of output is t+1 grades of input,
The preceding M continuous data of m grades of outputs of r blocks is the operation result of the block；
M data of arbitrary continuation in every piece of required output data, output terminal is changed to by its cyclic shift movement to the left K
0th Dao M-1；According to the property of discrete Fourier transform, ring shift left K of output terminal is equivalent to every to every piece of input terminal
A data are rotated, i.e., are multiplied by frequency displacement twiddle factor to n-th of input dataN=0 ..., P-1；The frequency displacement is rotated
The factorIt is distributed on division based method butterfly diagram original twiddle factors at different levels, the output of rapid solving piecemeal DFT comb spectrums,
So as to fulfill the rapid extraction of all pectination frequency points to distributing to user, following steps are specifically included：
Step 1. to it is N number of when input data, using conversion decompose mode be divided into L length for P block；
Step 2. calculates the total series m of split-radix butterfly diagram per block number evidence and the level that need not be cut to the block that L length is P
Number d, and the sequence number of every piece of input data is subjected to bit backward；
Step 3. calculates 2 butterfly of decimation in time base all in the 1st grade every piece to the block that L length is P；
Step 4. calculates the 2nd grade every piece to all decimation in time split-radix butterflies in d-th level to the block that L length is P；
Step 5. calculates every piece d+1 grades m grades of level-ones to the end to the block that L length is P according to division base cutting method
The split-radix butterfly of all cuttings；
The L length that step 6. obtains above-mentioned steps is that the output block of P is recombinated, and obtains the output of required pectination.
2. OFDMA distributed modes downlink comb spectrum rapid extracting method according to claim 1, its feature exist
In：In step 1, to N number of input data [x (0), x (1), x (2) ..., x (N-1)], by sequence { x (Ln1)},n1=0 ..., P-
1, it is mapped in the block that first length is P, is denoted as x respectively0(0),x0(1),…,x0(P-1)；By sequence { x (Ln1+1)},n1
=0 ..., P-1, are mapped in the block that second length is P, are denoted as x respectively1(0),x1(1),…,x1(P-1)；……；By sequence
Arrange { x (Ln1+L-1)},n1=0 ..., P-1, are mapped in the block that l-th length is P, are denoted as are denoted as x respectively respectivelyL-1(0),
xL-1(1),…,xL-1(P-1)。
3. OFDMA distributed modes downlink comb spectrum rapid extracting method according to claim 1, its feature exist
In：In step 2, to each data block, the total series of DIT split-radix butterfly diagrams isThe output of M point arbitrary continuations, no
The series for needing to cut isThe series for needing to cut is m-d；Input { x to r blocksr-1(0),xr-1(1),xr-1
(2),…,xr-1(P-1) } sequence number carries out bit backward, particularly as being by 0,1 ..., this P sequence number of P-1 is with m grades of binary forms
Show, then these binary numerals are overturn, and be expressed as new decimal system sequence number；Arranged again according to new decimal system sequence number
The order of element in sequence list entries, and it is denoted as { x(r-1)0(0),x(r-1)0(1),…,x(r-1)0(P-1) }, this will be r blocks the 1st
The input of level computing.
4. OFDMA distributed modes downlink comb spectrum rapid extracting method according to claim 1, its feature exist
In：In step 3,2 butterfly of decimation in time base all in the 1st grade of every piece in the block that L length is P is calculated respectively；For r
For block, 2 butterfly computation of decimation in time base all in the 1st grade is performed；The calculation formula of 2 butterfly of decimation in time base is expressed as：
Wherein p and q=p+1 represents the sequence number of the upper lower node of butterfly unit computing；Only p=2 × 4a-2+b×4a+1The base 2 at place
Butterfly needs to calculate, wherein a=0, and 1,2 ...；B=0,1,2 ...；Make p ＜ P-1.
5. OFDMA distributed modes downlink comb spectrum rapid extracting method according to claim 1, its feature exist
In：In step 4, the 2nd grade every piece is calculated respectively to all decimation in time split-radix butterflies in d-th level；For r blocks,
2nd grade performs decimation in time split-radix butterfly computation to d-th level；T grades where t is represented in split-radix butterfly, NiRepresent division
The size of twiddle factor block where base, wherein Ni=2t, 2≤t≤m；Input terminal frequency displacement twiddle factor WP -KnIt is distributed to the 2nd grade
New twiddle factor is after the twiddle factor original to d-th level
Wherein
Q (u)=(u-K) 2(m-t), u=0,1 ..., 2t-2- 1, t=2 ..., m. formula (3)
Especially, as u=0, φ (u) and φ (3u) is respectively first division of twiddle factor block where t grades of split-radix
The twiddle factor of base butterfly；During u=1, φ (u) and φ (3u) is respectively second of twiddle factor block where t grades of split-radix
The twiddle factor of split-radix butterfly, and so on；The calculation formula of the split-radix butterfly of decimation in time is represented by:
Here j is imaginary unit,
N=Ni×4a+1-Ni+2b×Ni×4a+1+ u formula (5)
Wherein a=-1,0,1,2 ...；B=0,1,2 ...；U=0,1 ..., 2t-2- 1 so that n ＜ P-3Ni/4；
Complete split-radix butterfly is carried out to the 2nd grade to d-th level of all decimation in time split-radix butterflies according to this formula to transport
Calculate.
6. OFDMA distributed modes downlink comb spectrum rapid extracting method according to claim 1, its feature exist
In：In step 5, the split-radix butterfly of every piece d+1 grades all cuttings of m grades of level-one to the end is calculated respectively；For r blocks
For, according to the division base cutting method of decimation in time, to the split-radix of d+1 grades of m grades of level-ones to the end using exporting
The butterfly computation that the mode of cutting is cut, specific cutting method are：
In d+1 grades, the first two output of decimation in time split-radix butterfly is only calculated, cuts decimation in time split-radix butterfly
Latter two output, this first two output be xt(n) withT grades where t is represented in split-radix butterfly, NiRepresent
The size of twiddle factor block where split-radix, wherein Ni=2d+1, frequency displacement twiddle factorBe distributed to d+1 grades it is original
New twiddle factor φ (u) and φ (3u) is calculated by formula (2) and formula (3) after twiddle factor, and n is calculated by formula (5)；This
The calculation formula that step cuts split-radix butterfly is represented by:
D+2 grades of m grades of level-ones to the end it is at different levels in, for every level-one each twiddle factor block calculate before M divide
Base butterfly, and each split-radix butterfly only calculates first output；Wherein Ni=2t, t=d+2 ..., m, frequency displacement twiddle factorBe distributed to d+2 grades to the end the twiddle factor φ (u) after m grades of original twiddle factors of level-one and φ (3u) by public affairs
Formula (2) and formula (3) calculate, and simply the value range of u is u=0,1 ..., M-1；The calculating that this step cuts split-radix butterfly is public
Formula is expressed as:
Wherein, n is calculated by formula (5), and simply the value range of u is u=0,1 ..., M-1.
7. OFDMA distributed modes downlink comb spectrum rapid extracting method according to claim 1, its feature exist
In：In step 6, the block that L length is P is subjected to reorganization operation, obtains the output of required pectination；The block that L length is P
In, the output of needs is gone out using preceding M data recombination in every piece, final required comb spectrum is obtained using following formula and exports [X
(K),X(K+1),…,X(K+M-1)；X(P+K),X(P+K+1),…,X(P+K+M-1)；…；X((L-1)P+K),X((L-1)P+
K+1),…,X((L-1)P+K+M-1)]；
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