CN102118350B - Channel estimation method of frequency domain filtering mobile WiMAX (world interoperability for microwave access) downlink system based on singular value decomposition - Google Patents
Channel estimation method of frequency domain filtering mobile WiMAX (world interoperability for microwave access) downlink system based on singular value decomposition Download PDFInfo
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Abstract
The invention relates to a channel estimation method of a frequency domain filtering mobile WiMAX (world interoperability for microwave access) downlink system based on singular value decomposition, which comprises the following steps: using the least-square estimation method to get channel frequency response estimation of an actually distributed pilot symbol subcarrier in each OFDM (orthogonal frequency division multiplexing) symbol; getting the channel frequency response estimation of the subcarriers of the adjacent OFDM symbols by channel frequency response linear interpolation in the corresponding subcarriers in the adjacent OFDM symbols; merging the actual pilot subcarriers with the channel frequency response estimation got by linear interpolation, arranging index values of all the subcarriers in an ascending order, and then sending into a frequency domain filter for denoising after judging a singular value threshold; and finally re-utilizing the linear interpolation to get the final channel frequency response estimation of all the data subcarriers. By using the frequency domain filter, the impacts of noise in a frequency domain least-square channel estimator can be reduced; by performing the judgment of the threshold based on the singular value decomposition on the frequency domain filter, the stability of frequency domain filtering is increased, and the problem of edge effect caused by non-uniform distribution of the pilot symbols is overcome.
Description
Technical field
The present invention relates to a kind of channel estimation methods of mobile WiMAX downlink system, be specifically related to a kind ofly based on singular value decomposition frequency domain filtering mobile WiMAX downlink system channel estimation methods, belong to wireless communication technology field.
Background technology
In recent years, the broadband wireless technical development is swift and violent, and (Wordwide Interoperability for Microware Access WiMAX) becomes the focus that wireless communication arena is paid close attention to micro-wave access global inter communication gradually, has vast market prospect.WiMAX is the wireless access wide band technology based on IEEE 802.16 series standards, supports fixing, nomadic, portable and mobile four kinds of application scenarioss entirely.Mobile WiMAX wherein uses orthogonal frequency division multiplexing multiple access technology (OFDMA) according to air-interface standard IEEE802.16e, have mobility, high-speed data service and the advantage cheaply supported, be considered as the wireless broad band technology of future generation that can contend with 3G by industry.
In the IEEE802.16e standard, each orthogonal frequency division multiplex OFDM subframe contains data subcarrier and pilot sub-carrier, and the allocative decision of its sub-channels contains uses subchannel scheme (FUSC) and part to use subchannel scheme (PUSC) fully.The sub-channel allocation scheme that is used for up-link OFDM symbolic construction is different with downlink system, in the PUSC sub-channel allocation scheme of downlink system, divide cluster after at first the subcarrier of two adjacent-symbols being removed virtual carrier and DC component, each bunch contains two pilot sub-carriers, and even symbol is different with odd symbol pilot sub-carrier position.Therefore, the pilot tone number is limited under the mobile WiMAX downlink system PUSC pattern, and the pilot frequency locations maldistribution.
Usually, channel condition information is vital for wireless communication system receiver, because it not only can balanced receiver, and auxiliary signal decoding, and can increase power system capacity.Yet because receiving terminal is unknown to channel information, so receiver need estimate that the quality of channel estimating greatly affects the performance of whole communication system like this to it.Although the research of channel estimation methods is existing a lot of in the wireless communication system, the research that is directed to actual mobile WiMAX system certain orthogonal frequency division multiplex OFDM symbolic construction channel estimation methods is also very limited.Because ad hoc structure and the sub-channel allocation scheme of OFDM symbol under the mobile WiMAX system, the conventional channel method of estimation is difficult to direct application.Generally speaking, channel estimation methods designs based on least mean-square error (MMSE) or least square (LS) criterion usually.MMSE channel estimation methods wherein has been owing to utilized the correlation properties of channel, thus obtained important performance gain, but complexity is higher.Although the LS channel estimation methods is carried out simple, channel estimation errors is bigger, has higher mean square error (MSE) value.And, because the considerably less and skewness of number of pilot symbols that distributes in the PUSC symbolic construction of IEEE 802.16e standard, cause channel estimating to have serious " edge effect ", so the channel estimation problems in the mobile WiMAX system is difficult to handle than general communication system more.
Recently, in pertinent literature, occurred at the WiMAX system based on improving discrete Fourier transform (DFT) (DFT) orthogonal frequency division multiplex OFDM channel estimation methods, this method estimated accuracy is higher, but need to eliminate edge effect by linear interpolation constructing virtual channel frequency response (VCFR) and the pilot tone that within coherence bandwidth, is spacedly distributed, and improve precision of channel estimation by the time domain noise that important tap detector (SCTD) or time domain low-pass filtering method reduce frequency domain LS method, so channel estimation process is comparatively loaded down with trivial details, and the reconstructed error of VCFR is bigger to the influence of channel estimating performance when signal to noise ratio is higher.
Summary of the invention
The purpose of this invention is to provide a kind ofly based on singular value decomposition frequency domain filtering mobile WiMAX downlink system channel estimation methods, avoiding constructing VCFR, simplify channel estimation process, solve the problem that there be serious " edge effect " in channel estimating.
For achieving the above object, of the present invention as follows based on singular value decomposition frequency domain filtering mobile WiMAX downlink system channel estimation methods technical scheme: this method at first obtains the channel frequency response at actual allocated frequency pilot sign subcarrier place estimation in each orthogonal frequency division multiplex OFDM symbol between dual-mode antenna with the least-squares estimation method in frequency domain; Then, the channel frequency response linear interpolation at each orthogonal frequency division multiplex OFDM symbol respective sub place in the channel frequency response at adjacent OFDM symbol subcarrier place is estimated by adjacent orthogonal frequency division multiplex OFDM symbol obtains; Again the channel frequency response of the frequency response estimation of actual pilot sub-carrier channels and linear interpolation in each orthogonal frequency division multiplex OFDM symbol is estimated to merge, and by sending in the lump after all sub-carrier indices value ascending orders arrangements through carrying out denoising in the frequency domain filter after the judgement of singular value threshold value; At last, the recycling linear interpolation obtains the final channel frequency response estimation at all data subcarrier places.
Further, the concrete steps of this method are as follows:
(1) transmitting terminal uses the sub-channel allocation scheme of sub-carrier structure to carry out the subcarrier mapping of data symbol and frequency pilot sign according to downlink portion in the IEEE 802.16e standard, forms an orthogonal frequency division multiplex OFDM symbol;
(2) transmitting terminal distributes frequency pilot sign to strange, even OFDM symbol respectively at the different sub carrier place, and each orthogonal frequency division multiplex OFDM symbol is made inverse Fourier transform, inserts Cyclic Prefix then and sends by transmitting antenna;
(3) the orthogonal frequency division multiplex OFDM symbol that obtains after the signal that receives is removed Cyclic Prefix and made Fourier transform of receiving terminal, the subcarrier mapped mode that uses according to transmitting terminal extracts the symbol at actual allocated pilot sub-carrier place in strange, the even OFDM symbol respectively;
(4) by the frequency pilot sign of step (3) and known transmitting terminal, calculate channel frequency response estimation in actual pilot subcarrier place in each orthogonal frequency division multiplex OFDM symbol by criterion of least squares; Each orthogonal frequency division multiplex OFDM symbol obtains in the channel frequency response at the adjacent orthogonal frequency division multiplex OFDM symbol pilot sub-carrier place channel frequency response linear interpolation by adjacent-symbol;
(5) channel estimating that merges actual pilot subcarrier least square channel estimating in each orthogonal frequency division multiplex OFDM symbol and obtained by the adjacent-symbol linear interpolation is sent into coefficient after its sub-carrier indices value by ascending order arranged and is
The frequency domain filter of process singular value decomposition threshold value judgement in carry out denoising; Wherein, part Fourier matrix
Element be
,
,
With
It is matrix
Unitary matrice after the singular value decomposition,
It is matrix
The pseudoinverse of singular value decomposition diagonal matrix
, matrix
Contain
In the matrix
Individual big singular value, wherein
Satisfy
And determined by threshold determination;
(6) will estimate that linear interpolation obtains in the symbol the final channel frequency response at all data subcarrier places and estimates through the channel frequency response of each orthogonal frequency division multiplex OFDM symbol of frequency domain filtering.
Further, described step (1) detailed process is: all useful subcarriers in each orthogonal frequency division multiplex OFDM symbol are divided into several bunches, bunch number depend on the size of Fourier transform, each bunch contains 12 data subcarriers and two pilot sub-carriers, even number OFDM symbol is different with the pilot sub-carrier position of odd number OFDM symbol, and remaining data subcarrier is used for different user and carries out transfer of data with the form of frequency division multiple access.
Further, the placement principle of pilot tone is in described strange, the even OFDM symbol: the actual pilot in the even number OFDM symbol in each bunch lays respectively at the 5th and the 9th subcarrier; Actual pilot in the odd number OFDM symbol in each bunch lays respectively at the 1st and the 13rd subcarrier.
Further, the concrete grammar of singular value decomposition is in the described step (5): at first with the part Fourier matrix
Carrying out singular value decomposition is
, matrix wherein
With
Dimension is respectively
With
, numerical value
It is matrix
Order, matrix
Be by
The diagonal matrix that singular value is formed
, so
, wherein
Then with matrix
Middle singular value and preset threshold
Compare, calculate satisfied
The singular value number of condition
, again will
Be modified as
, wherein
, be about to filter coefficient and be revised as
, parameter wherein
Span be
Of the present inventionly reduced The noise in the frequency domain least square channel estimating based on singular value decomposition frequency domain filtering mobile WiMAX downlink system channel estimation methods by using frequency domain filtering, and by to the frequency domain filter singular value decomposition and carry out the big singular value of threshold value judgement selected part, to reduce " edge effect " problem that pilot sub-carrier skewness that symbolic construction and subcarrier distribution scheme were caused is introduced.Whole process need not channel correlation properties information, and the frequency domain filtering based on singular value decomposition of use can make the minimum frequency domain least square method of complexity of the present invention and amount of calculation compare slightly to be increased.Yet the inventive method is used filtering and noise reduction owing to gathering around, thus obtained higher estimated accuracy than conventional method, and carry out simply, make it be applicable to actual application scenarios more.
The amount of calculation of the inventive method mainly comes from the frequency domain filter coefficient and the channel frequency response is estimated to carry out the calculating of filtering operation.In order to analyze for simplicity, the present invention is the high-order of the required multiplication number of times of each method relatively only.Because the frequency domain filter coefficient calculations of using among the present invention and channel are irrelevant, and only depend on the set of even symbol pilot sub-carrier and odd symbol pilot sub-carrier index place value, it is invariable, and it is known to be received machine, therefore this can be precomputed, so the amount of calculation of this part can be ignored.On the other hand, channel frequency response estimation is carried out the operation of filtering and can be taken advantage of realization by simple matrix, its amount of calculation is
O 
Rank.Traditional frequency domain least square method, can be so complexity is minimum owing to only need simple multiplication and division computing
O 
Rank.In addition, the DFT channel estimation methods amount of calculation of traditional use VCFR and the present invention are than lower slightly, and its complexity is O
Rank (wherein
Pilot tone number and virtual subnet carrier wave number sum after uniformly-spaced distributing).So, the inventive method is with the frequency domain least square method and use the DFT method of VCFR to compare, though complexity slightly increases, but compare with frequency domain least square method estimated performance and to have obtained great raising, compare with the DFT method of using VCFR that performance also makes moderate progress when high s/n ratio, the inventive method is easier to many antenna environment expansions simultaneously.
Description of drawings
Fig. 1 is the FB(flow block) of channel estimation methods of the present invention;
Fig. 2 is the present invention's idol symbol and the subcarrier distribution map of odd symbol in successive clusters;
Fig. 3 is conventional channel method of estimation and channel estimation methods bit error rate performance comparison diagram of the present invention under the PB 3km/h channel.
Embodiment
The inventive method has reduced The noise in the frequency domain least square channel estimating by using frequency domain filtering, and by to the frequency domain filter singular value decomposition and carry out the big singular value of threshold value judgement selected part, to reduce " edge effect " problem that pilot sub-carrier skewness that symbolic construction and subcarrier distribution scheme were caused is introduced.The present invention at first obtains the channel frequency response at actual allocated frequency pilot sign subcarrier place estimation in each orthogonal frequency division multiplex OFDM symbol between dual-mode antenna with the least-squares estimation method in frequency domain; Then, the channel frequency response linear interpolation at each orthogonal frequency division multiplex OFDM symbol respective sub place in the channel frequency response at adjacent OFDM symbol subcarrier place is estimated by adjacent orthogonal frequency division multiplex OFDM symbol obtains; Again the channel frequency response of the frequency response estimation of actual pilot sub-carrier channels and linear interpolation in each orthogonal frequency division multiplex OFDM symbol is estimated to merge, and by sending in the lump after all sub-carrier indices value ascending orders arrangements through carrying out denoising in the frequency domain filter after the judgement of singular value threshold value; At last, the recycling linear interpolation obtains the final channel frequency response estimation at all data subcarrier places.
Consider the descending mobile transmission system of single user WiMAX, its communication environment is to select comparatively serious PB channel frequently, and user's translational speed is 3km/h, and carrier frequency is that 2.5GHz and system bandwidth are 10MHz, the Fourier transform size is 1024, and circulating prefix-length is 128.Background noise is obeyed the being added with property Gaussian Profile of zero-mean.Data symbol is to be that the constellation mapping of 1/2 turbo coding, brachymemma, intra-frame interleaving and QPSK forms by binary number through code check.Adopt FB(flow block) that the inventive method carries out channel estimating as shown in Figure 1, concrete implementation step is as follows:
1) the transmitting terminal transmitting antenna uses the symbolic construction of subcarrier and sub-channel allocation scheme to carry out data and pilot sub-carrier mapping according to downlink portion in the IEEE 802.16e standard, forms an OFDM symbol.Concrete grammar is: be that all useful subcarriers in the OFDM symbol of 1024 subcarriers (getting rid of protection subcarrier and direct current subcarrier) are divided into 60 bunches with each size; each bunch contains 14 adjacent sub-carriers; wherein there are two subcarriers to be used for placing pilot tone; the placement principle is: the actual pilot in the even number OFDM symbol in each bunch lays respectively at the 5th and the 9th subcarrier, and forms the set that pilot tone in all bunches occupies the sub-carrier positions index and be
Actual pilot in the odd number OFDM symbol in each bunch lays respectively at the 1st and the 13rd subcarrier, and forms the set that pilot tone in all bunches occupies the sub-carrier positions index and be
At last, remaining subcarrier carries out transfer of data for different user with the form of frequency division multiple access.
2) do each OFDM symbol at transmitting antenna place contrary
NThe point Fourier conversion is inserted Cyclic Prefix then and is sent by transmitting antenna.Of even number and odd number OFDM symbol
pIndividual frequency pilot sign is expressed as respectively
With
, wherein
, continuously the pilot distribution structure in several bunches is as shown in Figure 2 for it.
3) the receiving terminal reception antenna need carry out the reception signal behind the removal Cyclic Prefix
NThe point Fourier conversion obtains the OFDM symbol through the wireless channel transmission, extracts the symbol of actual pilot symbol sub-carrier positions in each OFDM symbol respectively according to the subcarrier mapped mode of transmitting terminal use
If, constantly "
n" be even number, so
, the element of part fourier transform matrix
,
,
If odd number OFDM symbol is constantly,
,
,
,
Wherein, "
" the expression subtend measures diagonal matrix operation,
Expression the
nIndividual OFDM symbol channel impulse response constantly, and hypothesis channel exponent number
LFor known,
Be the noise vector that the reception antenna place obeys the multiple Gaussian Profile of zero-mean, its statistical property not with constantly "
n" variation and change.
4) by the frequency pilot sign of the known transmitting terminal of receiving terminal and step 3) together, calculate
nThe least-squares estimation of actual pilot subcarrier place channel frequency response in the individual OFDM symbol
, wherein, "
" represent that vector point is except operation.
5) the channel frequency response at adjacent OFDM symbol subcarrier place is obtained by the channel frequency response linear interpolation at respective sub place in the adjacent OFDM symbol in each OFDM symbol, and namely even number OFDM symbol is estimated as in the channel frequency response at odd number OFDM symbol pilot sub-carrier place
, and the channel frequency response at even number OFDM symbol pilot sub-carrier place is estimated as in the odd number OFDM symbol
6) actual pilot sub-carrier channels frequency response in each OFDM symbol is estimated
Estimate with the channel frequency response of linear interpolation
Merge, and according to all sub-carrier positions set ascending order orders of parity character
Reset and obtain the channel frequency response
, then, it is sent into carries out denoising in the frequency domain filter.Wherein, "
" expression set and operation, "
Sort" element of expression in will gather arrange by ascending order, gather
In
Individual element is
The frequency domain filter coefficient can be minimum and determine by following cost function, namely
, wherein,
Be the part fourier transform matrix
Element,
,
Like this, by finding the solution the filter coefficient that above-mentioned cost function calculation obtains be
Notice that because the position of pilot sub-carrier is not what be spacedly distributed, and also there is a large amount of protection subcarriers in entire spectrum here, so
Though reversible in theory, can present ill-condition, this will greatly influence the accuracy of channel estimating, also namely produce " edge effect " problem of channel estimating.For alleviating this ill-condition matrix inversion error to the influence of channel estimating performance, can adopt the method for following singular value decomposition: at first with the part Fourier matrix
Carrying out singular value decomposition is
, matrix wherein
With
Dimension is respectively
With
, numerical value
It is matrix
Order, matrix
Be by
The diagonal matrix that singular value is formed
, so
, wherein
Then, for increasing
The stability of inverting is with matrix
Middle singular value and preset threshold
Compare, calculate satisfied
The singular value number of condition
, again will
Be modified as
, wherein
, be about to filter coefficient and be revised as
, parameter wherein
Span be
So, actual pilot subcarrier place and the channel frequency response in its adjacent-symbol pilot sub-carrier position are corrected in each OFDM symbol
, the present invention claims its frequency domain filter based on singular value decomposition.At last, the recycling linear interpolation obtains the final channel frequency response estimation at all data subcarrier places.
Above-mentioned channel estimation process, by using frequency domain filtering based on the judgement of singular value decomposition threshold value that denoising is carried out in the channel frequency response and having eliminated " edge effect " that the ill-condition matrix inversion that caused by the pilot distribution inequality causes, improved performance for estimating channel further.Whole process is not used channel correlation properties knowledge and complicated matrix manipulation, therefore use channel estimation methods of the present invention to calculate frequency domain equalizer coefficients, not only can satisfy certain estimated accuracy, and be easy to carry out, be fit to the substandard downlink communication environment of IEEE 802.16e more.
Channel estimation methods, the frequency domain least square channel estimation methods that Fig. 3 adopts for the inventive method, do not carry out the least square channel estimation methods of singular value decomposition frequency domain filtering, use the comparative result of bit error rate performance under the conventional DFT low-pass filtering channel estimation methods of VCFR and the known perfect channel information.Wherein, threshold value T in the inventive method
h=0.5.Receiver has adopted simple zero forcing equalization method to resist the intersymbol interference that wireless fading channel produces.The channel frequency response that each user uses data symbol subcarrier place is obtained by the channel frequency response linear interpolation at the frequency pilot sign subcarrier place that estimates.Traditional DFT channel estimation methods is owing to use the VCFR of reconstruct, so bigger to the channel estimating performance influence at signal to noise ratio this reconstructed error when higher.Suppose that channel satisfies the piece fading characteristic.From the figure as can be seen, the bit error rate performance of channel estimation methods of the present invention obviously is better than traditional frequency domain least square channel estimation methods, at the DFT channel estimation methods of high s/n ratio end performance owing to use VCFR, and bit error rate performance is near perfect channel situation.Therefore, channel estimation methods of the present invention does not need all to carry out complicated matrix operation at every turn, need not to obtain in advance the correlation properties information of channel yet, has obtained certain estimated accuracy, and has been easy to practicability.
It should be noted last that: above embodiment is the non-limiting technical scheme of the present invention in order to explanation only, although with reference to above-described embodiment the present invention is had been described in detail, those of ordinary skill in the art is to be understood that; Still can make amendment or be equal to replacement the present invention, and not break away from any modification or partial replacement of the spirit and scope of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.
Claims (3)
1. one kind based on singular value decomposition frequency domain filtering mobile WiMAX downlink system channel estimation methods, it is characterized in that this method at first obtains the channel frequency response at actual allocated frequency pilot sign subcarrier place estimation in each orthogonal frequency division multiplex OFDM symbol between dual-mode antenna with the least-squares estimation method in frequency domain; Then, the channel frequency response linear interpolation at each orthogonal frequency division multiplex OFDM symbol respective sub place in the channel frequency response at adjacent OFDM symbol subcarrier place is estimated by adjacent orthogonal frequency division multiplex OFDM symbol obtains; Again the channel frequency response of the frequency response estimation of actual pilot sub-carrier channels and linear interpolation in each orthogonal frequency division multiplex OFDM symbol is estimated to merge, and by sending in the lump after all sub-carrier indices value ascending orders arrangements through carrying out denoising in the frequency domain filter after the judgement of singular value threshold value; At last, the recycling linear interpolation obtains the final channel frequency response at all data subcarrier places to be estimated,
Its concrete steps are as follows:
(1) transmitting terminal uses the sub-channel allocation scheme of sub-carrier structure to carry out the subcarrier mapping of data symbol and frequency pilot sign according to downlink portion in the IEEE802.16e standard, forms an orthogonal frequency division multiplex OFDM symbol;
(2) transmitting terminal distributes frequency pilot sign to strange, even OFDM symbol respectively at the different sub carrier place, and each orthogonal frequency division multiplex OFDM symbol is made inverse Fourier transform, inserts Cyclic Prefix then and sends by transmitting antenna;
(3) the orthogonal frequency division multiplex OFDM symbol that obtains after the signal that receives is removed Cyclic Prefix and made Fourier transform of receiving terminal, the subcarrier mapped mode that uses according to transmitting terminal extracts the symbol at actual allocated pilot sub-carrier place in strange, the even OFDM symbol respectively;
(4) by the frequency pilot sign of step (3) and known transmitting terminal, calculate channel frequency response estimation in actual pilot subcarrier place in each orthogonal frequency division multiplex OFDM symbol by criterion of least squares; Each orthogonal frequency division multiplex OFDM symbol obtains in the channel frequency response at the adjacent orthogonal frequency division multiplex OFDM symbol pilot sub-carrier place channel frequency response linear interpolation by adjacent-symbol;
(5) channel estimating that merges actual pilot subcarrier least square channel estimating in each orthogonal frequency division multiplex OFDM symbol and obtained by the adjacent-symbol linear interpolation is sent into coefficient after its sub-carrier indices value by ascending order arranged and is
The frequency domain filter of process singular value decomposition threshold value judgement in carry out denoising, singular value decomposition method is:
With the part Fourier matrix
Carrying out singular value decomposition is
Wherein matrix U and V dimension are respectively 2N
p* m and m * L, numerical value m is matrix
Order, matrix Σ be by
Diagonal matrix Σ=diag (σ that singular value is formed
1, σ
2, σ
m), so
Wherein
Then with singular value among the matrix Σ and a certain threshold value T
hCompare, calculate and satisfy σ
i〉=T
h, i=1 ..., the singular value number r of m condition will again
Be modified as
Wherein
Being about to filter coefficient is revised as
Wherein, part Fourier matrix
Element be
N represents N point Fourier transform, k
aFor occupying the set of sub-carrier positions index according to pilot tone in the tactic OFDM symbol of all sub-carrier positions of parity character set ascending orders,
Be k
aIn p' element, p'=1 ..., 2N
P, l=0 ..., L-1, V and U are matrixes
Unitary matrice after the singular value decomposition,
It is matrix
Singular value decomposition diagonal matrix Σ
rPseudoinverse, matrix Σ
rContain
R passing threshold judged the big singular value of choosing in the matrix, and r satisfies 0＜r≤min (2N
p, L), L is channel exponent number, 2N
pBe the frequency pilot sign number in the OFDM symbol, and determined by threshold determination;
2. according to claim 1 based on singular value decomposition frequency domain filtering mobile WiMAX downlink system channel estimation methods, it is characterized in that, described step (1) detailed process is: all useful subcarriers in each orthogonal frequency division multiplex OFDM symbol are divided into several bunches, bunch number depend on the size of Fourier transform, each bunch contains 12 data subcarriers and two pilot sub-carriers, even number OFDM symbol is different with the pilot sub-carrier position of odd number OFDM symbol, and remaining data subcarrier is used for different user and carries out transfer of data with the form of frequency division multiple access.
3. according to claim 2 based on singular value decomposition frequency domain filtering mobile WiMAX downlink system channel estimation methods, it is characterized in that the placement principle of pilot tone is in described strange, the even OFDM symbol: the actual pilot in the even number OFDM symbol in each bunch lays respectively at the 5th and the 9th subcarrier; Actual pilot in the odd number OFDM symbol in each bunch lays respectively at the 1st and the 13rd subcarrier.
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| CN103428127B (en) * | 2013-09-05 | 2016-08-17 | 电子科技大学 | A kind of CCFD system self-interference channel method of estimation based on SVD decomposition algorithm and device |
| CN105187337B (en) * | 2015-08-06 | 2018-09-18 | 青岛东软载波科技股份有限公司 | A kind of OFDM decision-aided channel estimation methods based on repeated encoding |
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