CN104883327A - Channel estimation method and system based on two-dimensional interpolation - Google Patents

Abstract

The invention provides a channel estimation method and a channel estimation system based on two-dimensional interpolation. The channel estimation method comprises the steps of: (1) establishing a channel model of an OFDM system; (2) adopting a rhombic pilot insertion style, and inserting pilot symbols in directions of time domain and frequency domain of OFDM symbols of the channel model respectively to obtain an original sending signal with two-dimensional interpolation; (3) carrying out channel estimation on the original sending signal received by a receiving end to obtain a pilot point position and an estimated channel value thereof; and (4) dividing a rhombic pilot plane into two regular sub-pilot planes according to the estimated channel value, conducting channel response interpolation on each sub-pilot plane, and calculating an average value to obtain a channel response estimated value. According to the technical scheme provided by the invention, the channel estimation is carried out by adopting the rhombic pilot insertion style combined with an improved bicubic two-dimensional interpolation method, the performance of channel estimation is improved, the complexity of the algorithm is low, and the channel estimation method and the channel estimation system are easy to implement.

Description

Based on channel estimation methods and the system of two-dimensional interpolation

Technical field

The present invention relates to communication technical field, particularly relate to a kind of channel estimation methods based on two-dimensional interpolation and system.

Background technology

In LTE standard, descending OFDM (OFDM) of taking is modulated, and uply takes single-carrier frequency division multiple access (SC-FDMA) modulation system.OFDM is a kind of multi-carrier modulation, is overcome the frequency selective fading of channel by the impact reduced and eliminate intersymbol interference, and its general principle is N number of subsignal by signal segmentation, then modulates N number of mutually orthogonal subcarrier respectively with N number of subsignal.Because the frequency spectrum of subcarrier is overlapped, thus higher spectrum efficiency can be obtained.

The intersymbol interference (ISI) that the multi-path delay spread of wireless channel causes seriously limits the data transmission rate on wireless channel, and OFDM technology can suppress intersymbol interference effectively, so earn widespread respect. because OFDM is to the orthogonality requirement between each subcarrier, make the receiving-transmitting sides of ofdm system (carrier synchronization must be comprised by stringent synchronization, sampling clock is synchronous), enough accurate channel estimating must be had simultaneously. due to the time variation of wireless channel, most of ofdm system all have employed the channel estimation methods based on pilot tone training signal, namely the known pilot signal of insertion is utilized to carry out channel rough estimate, then the total regression of channel is obtained by interpolation method.

Based on pilot aided channel estimating due to have simple, accurately and the feature such as high stability, become the channel estimating mode that OFDM is the most frequently used.So-called pilot tone is some special data, the position of receiving terminal these data known and numerical value.These data are inserted in initial data according to certain principle, then carry out IDFT conversion with initial data.At receiving terminal, after over-sampling and DFT conversion, utilize the known pilot signal of insertion to carry out channel rough estimate, then obtained the total regression of channel by certain process means (as interpolation, filtering), thus carry out equilibrium to received signal, improve systematic function.

Due to ofdm system have time, frequently two dimension, so can the decline of adaptive channel in time domain and frequency domain better based on the pilot tone of two-dimensional model, there is lower pilot density and the availability of frequency spectrum of Geng Gao.So the channel estimation methods based on pilot aided can be divided into two steps, the channel value at first step estimating pilot frequency point place, according to these values, the channel value of data estimator position.Second step needs to carry out interpolation to known estimated value in estimating, thus obtains the total regression of channel.

Common interpolation method comprises one dimension interpolation and two-dimensional interpolation, and wherein two-dimensional interpolation comprises network node interpolation and loose point interpolation two type.Network node interpolation comprises most neighbor interpolation, up interpolation, bilinear interpolation and bicubic interpolation etc.Loose point interpolation comprises revises Shepherd method etc.The complexity of the estimated accuracy that different interpolation methods obtains and realization is also not quite similar.

The channel estimation methods of current pilot aided mainly adopts four kinds of pilot frequency modes such as bulk, pectination, lattice shape and rhombus.When carrying out interpolation, take one dimension interpolation to make accuracy of channel estimation lower, although the loose point interpolation accuracy of two dimension is higher, the complexity realized is also correspondingly higher.

In sum, existing interpolation method, be difficult to the performance ensureing channel estimating, precision of channel estimation is lower, algorithm complex is higher, is unfavorable in realization.

Summary of the invention

Based on this, be necessary for above-mentioned technical problem, a kind of complexity is low, estimated accuracy the is higher channel estimation methods based on two-dimensional interpolation and system are provided.

Based on a channel estimation methods for two-dimensional interpolation, comprise the steps:

(1) channel model of ofdm system is set up;

(2) adopt rhombus pilots insertion pattern, in the time domain and frequency domain direction of the OFDM symbol of described channel model, insert frequency pilot sign respectively, obtain the original transmission signal of two-dimensional interpolation;

(3) the described original transmission signal received receiving terminal carries out channel estimating and obtains pilot point position and estimate channel value;

(4) rhombus pilot tone plane is divided into two regular sub-pilot tone planes according to described estimation channel value, respectively channel response interpolation carried out and calculating mean value to every sub-pilot tone plane, obtain channel response estimated value.

Based on a channel estimation system for two-dimensional interpolation, comprising:

Channel model creation module, for setting up the channel model of ofdm system;

Pilot tone model creation module, for adopting rhombus pilots insertion pattern, inserts frequency pilot sign respectively in the time domain and frequency domain direction of the OFDM symbol of described channel model, obtains the original transmission signal of two-dimensional interpolation;

Channel rough estimate module, the described original transmission signal for receiving receiving terminal carries out channel estimating and obtains pilot point position and estimate channel value;

Interpolation processing module, for according to described estimation channel value rhombus pilot tone plane being divided into two regular sub-pilot tone planes, carrying out channel response interpolation and calculating mean value to every sub-pilot tone plane respectively, obtaining channel response estimated value.

The above-mentioned channel estimation methods based on two-dimensional interpolation and system, rhombus pilots insertion pattern is adopted to insert frequency pilot sign, after carrying out channel rough estimate, rhombus pilot tone plane is divided into two regular sub-pilot tone planes, by taking the bicubic two-dimensional interpolation method improved to carry out channel estimating, respectively channel response interpolation being carried out to every sub-pilot tone plane and calculating mean value obtains final channel response estimated value, improve the performance of channel estimating, and algorithm complex is lower, be convenient to realize.

Accompanying drawing explanation

Fig. 1 is the channel estimation methods flow chart that the present invention is based on two-dimensional interpolation;

Fig. 2 is ofdm system model schematic;

Fig. 3 is rhombus pilot tone schematic shapes;

Fig. 4 is the second sub-pilot tone floor map;

Fig. 5 is the channel estimation system structural representation that the present invention is based on two-dimensional interpolation;

Fig. 6 is the structural representation of the interpolation processing module of an embodiment.

Embodiment

Be described in detail based on the channel estimation methods of two-dimensional interpolation and the embodiment of system of the present invention below in conjunction with accompanying drawing.

Shown in figure 1, Fig. 1 is the channel estimation methods flow chart that the present invention is based on two-dimensional interpolation, comprises the steps:

(1) channel model of ofdm system is set up.

At ofdm system, be utilize fast Fourier transform IFFT, in frequency domain, channel width is divided into multiple subchannel, every sub-channels adjusts with a subcarrier, mutually orthogonal between each subcarrier, parallel transmission.

Shown in figure 2, Fig. 2 is ofdm system model schematic.Binary data after coding is transformed into frequency domain data X (k), k=0,1 by modulation (as: QBSK) ..., N-1, N are the carrier numbers of OFDM.After frequency domain inserts pilot tone, utilize IFFT that X (k) is modulated into OFDM and meet; Then OFDM symbol inserts cyclic prefix CP in front end, and form protection interval, its length should be greater than the maximum delay τ of channel _max, to eliminate intersymbol interference ISI.The discrete form that after adding Cyclic Prefix, OFDM meets as shown in the formula:

$x\left(n\right)=\frac{1}{\sqrt{N}}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}X\left(k\right)e^{\frac{j2\mathrm{\&pi;kn}}{N}}-\mathrm{CP}<k\&le;N-1$

In formula, X (k) uploads defeated data symbol for a kth subcarrier, and it is the copy data generated by QBSK or other modulation system, and x (n) is the OFDM symbol in n moment.Channel is sent into after signal parallel serial conversion.Receiving terminal is removed after Cyclic Prefix, is converted signal to switch back to frequency domain and extract pilot signal to be used for channel estimating by FFT.After channel compensation, frequency domain data carries out demodulation, decodes with restoring user data.

In one embodiment, described step (1) can specifically comprise following process:

Set up multiple carrier channel model, each path arrives receiving terminal with different amplitudes, phase place, frequency displacement and time delay respectively, and the envelope in path is rayleigh distributed, that is:

A in formula _l, f _d,l, and τ _lthe amplitude of channel, Doppler frequency shift, phase place and time delay respectively, $\mathrm{\&delta;}(\mathrm{\&tau;}-{\mathrm{\&tau;}}_l)=\left\{\begin{array}{c}1,\mathrm{\&tau;}-{\mathrm{\&tau;}}_l\\ 0,\mathrm{other}\end{array}\right.$ For rectangular pulse.

(2) adopt rhombus pilots insertion pattern, in the time domain and frequency domain direction of the OFDM symbol of described channel model, insert frequency pilot sign respectively, obtain the original transmission signal of two-dimensional interpolation.

The channel frequency response CFR of ofdm system can be regarded as a 2D signal, thus in time domain and frequency domain both direction, can insert pilot signal regularly.

The insertion of pilot tone in OFDM symbol can be regarded as and sample to the two dimension of channel frequency response, and therefore pilots insertion demand fulfillment sampling thheorem to avoid frequency alias, at coherence bandwidth B _cin and coherence time T _cinside at least to insert a frequency pilot sign.

As a kind of execution mode, time, Nyquist interval df, dt frequently on direction and channel correlation bandwidth B _c, coherence time T _cbetween must meet following formula:

$\mathrm{df}\&le;\frac{1}{{\mathrm{\&Delta;f}}_{{\mathrm{\&tau;}}_{\max }}},\mathrm{dt}\&le;\frac{1}{{2f}_{d_{\max }}{T}_{\mathrm{symbol}}}$

In formula, τ _max, be respectively maximum delay and maximum doppler frequency, Δ f, T _symbolfor carrier spacing and the mark space of ofdm system.

Relative to pilot frequency modes such as employing bulk, pectination, lattice shape and rhombuses, adopt rhombus pilots insertion pattern can improve the performance of channel estimating, in the present invention, adopt the pilot tone shape of rhombus pilot tone as shown in Figure 3, Fig. 3 is rhombus pilot tone schematic shapes, in time, frequency two-dimension pilot frequency plane, white box is user data, and grey box is community particular interference signal.

(3) the described original transmission signal received receiving terminal carries out channel estimating and obtains pilot point position and estimate channel value.

In this step, be the rough estimate of channel, estimating pilot frequency point position and the channel value in data estimator position thereof.

In one embodiment, the estimation procedure of described step (3), mainly comprises as follows:

According to inserting frequency pilot sign in described original transmission signal, utilizing channel estimation methods to carry out channel estimating to the pilot point of the described original transmission signal that receiving terminal receives, obtaining channel estimation value.

Based on the channel estimation process of pilot aided, comprise the channel estimating of pilot point, two-dimensional interpolation.At this, by the frequency pilot sign inserted in the useful data sent, the channel estimation results of pilot frequency locations can be obtained;

Concrete, estimate the channel frequency response of pilot point, the method for channel estimating has a lot, as least-squares estimation, linearly minimumly divides equally estimation, maximal possibility estimation or Bayesian Estimation etc.; For least square (LS), underdraw channel estimation process.

If pilot symbol transmitted is p (k), receive frequency pilot sign position p ' (k), according to LS rule, the channel estimation value obtaining pilot point place is:

${\hat{H}}_p\left(k\right)=\frac{p^{\&prime;}\left(k\right)}{p\left(k\right)}$

$k=\mathrm{mL},m\&Element;[0,N_p-1],L=\frac{N}{N_p}$

In formula, N _pfor the number of pilot symbols inserted, L is pilot symbol interval.

(4) rhombus pilot tone plane is divided into two regular sub-pilot tone planes according to described estimation channel value, respectively channel response interpolation carried out and calculating mean value to every sub-pilot tone plane, obtain channel response estimated value.

In this step, utilize the channel rough estimate result of pilot frequency locations, interpolation is carried out to known estimated value, obtained the total regression estimated result of the channel of useful data position by interpolation, complete final channel response and estimate.

In order to the advantage that the frequency and time that make full use of pilot tone are equidistant, present invention improves over bicubic interpolation (Bicubic interpolation) method, and for carrying out interpolated channel estimation.

Bicubic interpolation is interpolation method the most frequently used in two-dimensional space, in this approach, function f is at point (x, y) value can be obtained by the weighted average of 16 sampled points nearest in rectangular mesh, need use two polynomial interopolation cubic functions here, each direction uses one.In mathematics, bicubic interpolation is the expansion of cube interpolation of interpolated data point on two-dimensional regular grid, relevant interpolation surface ratio bilinear interpolation and most neighbor interpolation smooth.

The present invention improves bicubic two-dimensional interpolation algorithm, and estimate the total regression of channel, the interpolation algorithm after improvement is mainly as follows: first rhombus pilot tone plane is divided into two parts; Then in every sub-pilot tone plane, bicubic interpolation algorithm is utilized to carry out channel response estimation; Again twice channel response is averaged, ask for final channel response and estimate.

Bulk, pectination, lattice shape and rhombus pilot frequency mode is better than owing to adopting rhombus pilot frequency mode, the performance of channel estimating can be improved, but this pilot frequency mode is also not exclusively even in the distribution of time orientation and frequency domain direction, is thus not suitable for directly taking gridding interpolation method.The present invention takes the pilot frequency mode of rhombus when inserting pilot signal.In order to better realize Interpolate estimation, by improvement bicubic interpolation and for channel estimating, pilot tone is split into two grid pilot tones, and then in each network pilot, utilize bicubic interpolation to carry out channel estimating respectively, averaged again, because these two grid pilot tones are then evenly distributed at time orientation and frequency domain direction, bicubic interpolation is utilized to obtain interpolation curved surface more smooth, Interpolate estimation precision is higher, simultaneously, two grid pilot tones are split into by just pilot tone, the uniformity of network interpolation can be made full use of, interpolation algorithm complexity is reduced greatly, be convenient to realize.

In one embodiment, described step (4) specifically can comprise the steps:

(4-1) obtain rhombus pilot tone plane according to described estimation channel value, rhombus pilot tone plane is divided into the first sub-pilot tone plane and the second sub-pilot tone plane of the rectangular mesh shape of rule.

As a kind of execution mode, rhombus pilot tone plane is divided into the first sub-pilot tone plane of rectangular mesh shape and the step of the second sub-pilot tone plane of rule, can comprises as follows:

1) odd-numbered line and the even number line at the particular interference signal place, community in rhombus pilot tone plane is extracted respectively, the equally distributed first sub-pilot tone of composition rule and the second sub-pilot tone.

Shown in figure 3, the odd-numbered line at the particular interference signal place, community in pilot tone plane and even number line, illustrate with the shape shown in Fig. 3 below.

2) odd-numbered line at the particular interference signal place, community of sub-for first in rhombus pilot tone pilot tone retained and removes even number line interference signal, forming the first sub-pilot tone plane of rectangular mesh shape.

The odd-numbered line at particular interference signal place, community keeps down, and even number line interference signal is removed.

3) even number line at the particular interference signal place, community of sub-for second in rhombus pilot tone pilot tone retained and removes odd-numbered line interference signal, forming the second sub-pilot tone plane of rectangular mesh shape.

Shown in figure 4, Fig. 4 is the second sub-pilot tone floor map, and as seen from the figure, the even number line at particular interference signal place, community keeps down, and odd-numbered line interference signal is removed.

Can find out after dividing, two sub-pilot tones are all the rectangular mesh planes of rule, thus bicubic interpolation algorithm can be utilized to carry out channel estimating.

(4-2) in the first sub-pilot tone plane and the second sub-pilot tone plane, utilize bicubic interpolation algorithm to carry out channel response estimation respectively, obtain the first response estimation value and the second response estimation value.

Can obtain a continuous print interpolating function by bicubic interpolation, its first-order partial derivative is continuous, and cross derivative everywhere continuous.

Suppose function f and derivative f thereof _x, f _yand f _x,yin four points (0,0), (1,0), the functional value on (0,1) and (1,1) is known, and functional value is plural number, then interpolation surface can be write as:

$p(x,y)=\underset{i=0}{\overset{3}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{3}{\mathrm{\&Sigma;}}}{a}_{\mathrm{ij}}{x}^i{y}^j$

Then interpolation problem is equivalent to solve 16 coefficient a _ij.Functional value is substituted into p (x, y), has:

1.f(0,0)＝p(0,0)＝a ₀₀

2.f(1,0)＝p(1,0)＝a ₀₀+a ₁₀+a ₂₀+a ₃₀

3.f(0,1)＝p(0,1)＝a ₀₀+a ₀₁+a ₀₂+a ₀₃

4. $f\left(\mathrm{1,1}\right)=p\left(\mathrm{1,1}\right)=\underset{i=0}{\overset{3}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{3}{\mathrm{\&Sigma;}}}{a}_{\mathrm{ij}}$

Similar, by the local derviation on x and y direction, 8 equations below can be obtained:

5.f _x(0,0)＝p _x(0,0)＝a ₁₀

6.f _x(1,0)＝p _x(1,0)＝a ₁₀+2a ₂₀+3a ₃₀

7.f _x(0,1)＝p _x(0,1)＝a ₁₀+a ₁₁+a ₁₂+a ₁₃

8. $f_x\left(\mathrm{1,1}\right)=p_x\left(\mathrm{1,1}\right)=\underset{i=0}{\overset{3}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{3}{\mathrm{\&Sigma;}}}{a}_{\mathrm{ij}}i$

9.f _y(0,0)＝p _y(0,0)＝a ₀₁

10.f _y(1,0)＝p _y(1,0)＝a ₀₁+a ₁₁+a ₂₁+a ₃₁

11.f _y(0,1)＝p _y(0,1)＝a ₀₁+2a ₀₂+3a ₀₃

12. $f_y\left(\mathrm{1,1}\right)=p_x\left(\mathrm{1,1}\right)=\underset{i=0}{\overset{3}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{3}{\mathrm{\&Sigma;}}}{a}_{\mathrm{ij}}j$

Similarly, the cross derivative about xy can obtain following four equations:

13.f _xy(0,0)＝p _xy(0,0)＝a ₁₁

14.f _xy(1,0)＝p _xy(1,0)＝a ₁₁+2a ₂₁+3a ₃₁

15.f _xy(0,1)＝p _xy(0,1)＝ ₃a ₁₁₃+2a ₁₂+3a ₁₃

16. $f_{\mathrm{xy}}\left(\mathrm{1,1}\right)=p_{\mathrm{xy}}\left(\mathrm{1,1}\right)=\underset{i=0}{\mathrm{\&Sigma;}}\underset{j=0}{\mathrm{\&Sigma;}}{a}_{\mathrm{ij}}\mathrm{ij}$

By solving above-mentioned 16 systems of linear equations, 16 coefficient a can be obtained _ij.The p (x, y) obtained like this is continuous print in interval [0,1] × [0,1], and has continuous print derived function.

Bicubic interpolation arbitrary intervals grid can be linked together by such bicubic surface, guarantees the requirement of derivative energy coincidence boundary.

If function is unknown in the derivative value of four points, then can obtain by being similar at the field functional value of these points.All coefficients are formed a vector:

α＝[a ₀₀a ₁₀a ₂₀a ₃₀a ₀₁a ₁₁a ₂₁a ₃₁a ₀₂a ₁₂a ₂₂a ₃₂a ₀₃a ₁₃a ₂₃a ₃₃] ^T

Order

X=[f (0,0) f (1,0) f (0,1) f (1,1) f _x(0,0) f _x(1,0) f _x(0,1) f _x(1,1) f _y(0,0) f _y(1,0) f _y(0,1) f _y(1,1) f _xy(0,0) f _xy(1,0) f _xy(0,1) f _xy(1,1)] ^tthen problem becomes the solution asking system of linear equations A α=x.

Utilize the frequency response values of three adjacent pilot frequencies positions that estimated and combine corresponding three different coordinate points along frequency interval, find out this third degree curve of 3 of a process, the junction that this curve meets two adjacent with it curves is smooth (namely the first derivative of two curves on a certain position is equal), carries out interpolation according to calculated third degree curve to the Data Position frequency response values between them.

(4-3) calculate the mean value of described first response estimation value and the second response estimation value, obtain the channel response estimated value of ofdm system.

To sum up embodiment, utilizes twice bicubic interpolation to estimate at two enterprising row interpolations of sub-pilot tone two dimensional surface respectively, and averages and obtain final channel response and estimate.Compared with other interpolation method, the interpolation curved surface that the bicubic interpolation of this improvement obtains is more smooth, and Interpolate estimation precision is higher.Meanwhile, prismatic pilot tone is split as two regular rectangle planes, the uniformity of network interpolation can be made full use of, interpolation algorithm complexity is reduced greatly.

Shown in figure 5, Fig. 5 is the channel estimation system structural representation that the present invention is based on two-dimensional interpolation, comprising:

Channel model creation module, for setting up the channel model of ofdm system;

Pilot tone model creation module, for adopting rhombus pilots insertion pattern, inserts frequency pilot sign respectively in the time domain and frequency domain direction of the OFDM symbol of described channel model, obtains the original transmission signal of two-dimensional interpolation;

Channel rough estimate module, the described original transmission signal for receiving receiving terminal carries out channel estimating and obtains pilot point position and estimate channel value;

Interpolation processing module, for according to described estimation channel value rhombus pilot tone plane being divided into two regular sub-pilot tone planes, carrying out channel response interpolation and calculating mean value to every sub-pilot tone plane respectively, obtaining channel response estimated value.

In one embodiment, described channel model creation module, is further used for the multiple carrier channel model setting up ofdm system, and wherein, each path arrives receiving terminal with different amplitudes, phase place, frequency displacement and time delay respectively, and the envelope in path is rayleigh distributed.

In one embodiment, described channel rough estimate module, being further used for according to inserting frequency pilot sign in described original transmission signal, utilizing channel estimation methods to carry out channel estimating to the pilot point of the described original transmission signal that receiving terminal receives, obtaining channel estimation value;

Wherein, described channel estimation methods comprises least squares estimate, linearly minimumly divides equally the estimation technique, maximum likelihood estimate or Bayes' assessment.

In one embodiment, shown in figure 6, Fig. 6 is the structural representation of the interpolation processing module of an embodiment, mainly comprises:

Pilot tone division unit, for obtaining rhombus pilot tone plane according to described estimation channel value, is divided into the first sub-pilot tone plane and the second sub-pilot tone plane of the rectangular mesh shape of rule by rhombus pilot tone plane;

Interpolation process unit, for utilizing bicubic interpolation algorithm to carry out channel response estimation in the first sub-pilot tone plane and the second sub-pilot tone plane respectively, obtains the first response estimation value and the second response estimation value;

Average calculation unit, for calculating the mean value of described first response estimation value and the second response estimation value, obtains the channel response estimated value of ofdm system.

As a kind of execution mode, described pilot tone division unit, the first sub-pilot tone plane of rectangular mesh shape and the process of the second sub-pilot tone plane that rhombus pilot tone plane are divided into rule comprise:

Extract odd-numbered line and the even number line at the particular interference signal place, community in rhombus pilot tone plane respectively, the equally distributed first sub-pilot tone of composition rule and the second sub-pilot tone;

The odd-numbered line at the particular interference signal place, community of sub-for first in rhombus pilot tone pilot tone is retained and removes even number line interference signal, forms the first sub-pilot tone plane of rectangular mesh shape;

The even number line at the particular interference signal place, community of sub-for second in rhombus pilot tone pilot tone is retained and removes odd-numbered line interference signal, forms the second sub-pilot tone plane of rectangular mesh shape.

Channel estimation system based on two-dimensional interpolation of the present invention and the channel estimation methods one_to_one corresponding based on two-dimensional interpolation of the present invention, the technical characteristic of setting forth in the embodiment of the above-mentioned channel estimation methods based on two-dimensional interpolation and beneficial effect thereof are all applicable to, in the embodiment based on the channel estimation system of two-dimensional interpolation, hereby state.

The above embodiment only have expressed several execution mode of the present invention, and it describes comparatively concrete and detailed, but therefore can not be interpreted as the restriction to the scope of the claims of the present invention.It should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.

Claims (10)

1. based on a channel estimation methods for two-dimensional interpolation, it is characterized in that, comprise the steps:

(1) channel model of ofdm system is set up;

(2) adopt rhombus pilots insertion pattern, in the time domain and frequency domain direction of the OFDM symbol of described channel model, insert frequency pilot sign respectively, obtain the original transmission signal of two-dimensional interpolation;

(3) the described original transmission signal received receiving terminal carries out channel estimating and obtains pilot point position and estimate channel value;

(4) rhombus pilot tone plane is divided into two regular sub-pilot tone planes according to described estimation channel value, respectively channel response interpolation carried out and calculating mean value to every sub-pilot tone plane, obtain channel response estimated value.

2. the channel estimation methods based on two-dimensional interpolation according to claim 1, is characterized in that, described step (1) comprising:

Set up the multiple carrier channel model of ofdm system, wherein, each path arrives receiving terminal with different amplitudes, phase place, frequency displacement and time delay respectively, and the envelope in path is rayleigh distributed.

3. the channel estimation methods based on two-dimensional interpolation according to claim 1, is characterized in that, described step (3) comprising:

According to inserting frequency pilot sign in described original transmission signal, utilizing channel estimation methods to carry out channel estimating to the pilot point of the described original transmission signal that receiving terminal receives, obtaining channel estimation value;

Wherein, described channel estimation methods comprises least squares estimate, linearly minimumly divides equally the estimation technique, maximum likelihood estimate or Bayes' assessment.

4. the channel estimation methods based on two-dimensional interpolation according to claim 1, is characterized in that, described step (4) comprising:

Obtain rhombus pilot tone plane according to described estimation channel value, rhombus pilot tone plane is divided into the first sub-pilot tone plane and the second sub-pilot tone plane of the rectangular mesh shape of rule;

In the first sub-pilot tone plane and the second sub-pilot tone plane, utilize bicubic interpolation algorithm to carry out channel response estimation respectively, obtain the first response estimation value and the second response estimation value;

Calculate the mean value of described first response estimation value and the second response estimation value, obtain the channel response estimated value of ofdm system.

5. the channel estimation methods based on two-dimensional interpolation according to claim 4, it is characterized in that, in described step (4), the first sub-pilot tone plane of rectangular mesh shape and the step of the second sub-pilot tone plane that rhombus pilot tone plane are divided into rule comprise:

Extract odd-numbered line and the even number line at the particular interference signal place, community in rhombus pilot tone plane respectively, the equally distributed first sub-pilot tone of composition rule and the second sub-pilot tone;

The odd-numbered line at the particular interference signal place, community of sub-for first in rhombus pilot tone pilot tone is retained and removes even number line interference signal, forms the first sub-pilot tone plane of rectangular mesh shape;

The even number line at the particular interference signal place, community of sub-for second in rhombus pilot tone pilot tone is retained and removes odd-numbered line interference signal, forms the second sub-pilot tone plane of rectangular mesh shape.

6. based on a channel estimation system for two-dimensional interpolation, it is characterized in that, comprising:

Channel model creation module, for setting up the channel model of ofdm system;

Pilot tone model creation module, for adopting rhombus pilots insertion pattern, inserts frequency pilot sign respectively in the time domain and frequency domain direction of the OFDM symbol of described channel model, obtains the original transmission signal of two-dimensional interpolation;

Channel rough estimate module, the described original transmission signal for receiving receiving terminal carries out channel estimating and obtains pilot point position and estimate channel value;

Interpolation processing module, for according to described estimation channel value rhombus pilot tone plane being divided into two regular sub-pilot tone planes, carrying out channel response interpolation and calculating mean value to every sub-pilot tone plane respectively, obtaining channel response estimated value.

7. the channel estimation system based on two-dimensional interpolation according to claim 6, it is characterized in that, described channel model creation module, be further used for the multiple carrier channel model setting up ofdm system, wherein, each path arrives receiving terminal with different amplitudes, phase place, frequency displacement and time delay respectively, and the envelope in path is rayleigh distributed.

8. the channel estimation system based on two-dimensional interpolation according to claim 6, it is characterized in that, described channel rough estimate module, be further used for according to inserting frequency pilot sign in described original transmission signal, utilize channel estimation methods to carry out channel estimating to the pilot point of the described original transmission signal that receiving terminal receives, obtain channel estimation value;

Wherein, described channel estimation methods comprises least squares estimate, linearly minimumly divides equally the estimation technique, maximum likelihood estimate or Bayes' assessment.

9. the channel estimation system based on two-dimensional interpolation according to claim 6, is characterized in that, described interpolation processing module comprises:

Pilot tone division unit, for obtaining rhombus pilot tone plane according to described estimation channel value, is divided into the first sub-pilot tone plane and the second sub-pilot tone plane of the rectangular mesh shape of rule by rhombus pilot tone plane;

Interpolation process unit, for utilizing bicubic interpolation algorithm to carry out channel response estimation in the first sub-pilot tone plane and the second sub-pilot tone plane respectively, obtains the first response estimation value and the second response estimation value;

Average calculation unit, for calculating the mean value of described first response estimation value and the second response estimation value, obtains the channel response estimated value of ofdm system.

10. the channel estimation system based on two-dimensional interpolation according to claim 9, is characterized in that, described pilot tone division unit, and the first sub-pilot tone plane of rectangular mesh shape and the process of the second sub-pilot tone plane that rhombus pilot tone plane are divided into rule comprise:

Extract odd-numbered line and the even number line at the particular interference signal place, community in rhombus pilot tone plane respectively, the equally distributed first sub-pilot tone of composition rule and the second sub-pilot tone;

The odd-numbered line at the particular interference signal place, community of sub-for first in rhombus pilot tone pilot tone is retained and removes even number line interference signal, forms the first sub-pilot tone plane of rectangular mesh shape;

The even number line at the particular interference signal place, community of sub-for second in rhombus pilot tone pilot tone is retained and removes odd-numbered line interference signal, forms the second sub-pilot tone plane of rectangular mesh shape.