CN104735016A - OFDM system fractional part of frequency offset estimation method and device based on multi-path channel - Google Patents

Abstract

The invention belongs to the technical field of OFDM, and provides an OFDM system fractional part of frequency offset estimation method and device based on a multi-path channel. The OFDM system fractional part of frequency offset estimation method based on the multi-path channel comprises the steps that an orthogonal frequency division multiplexing (OFDM) signal is obtained; the delay of the OFDM signal passing through the multi-path channel is estimated, and the maximum delay is obtained, wherein the maximum delay is the maximum delay time of the OFDM passing through the multi-path channel; according to the maximum delay and the OFDM signal, a sampling point, not being affected by intersymbol interferences, in a cyclic prefix is obtained; by means of the correlation between the copied partial data and the sampling point, not being affected by intersymbol interferences, in the cyclic prefix, fractional part of frequency offset estimation is carried out, wherein the copied partial data comprise received sampling points copied in the OFDM symbols. The fractional part of frequency offset estimation precision of the OFDM system is improved, and therefore the bit error rate of the OFDM system is lowered.

Description

A kind of ofdm system fractional part of frequency offset method of estimation based on multipath channel and device

Technical field

The invention belongs to OFDM technology field, particularly relate to a kind of ofdm system fractional part of frequency offset method of estimation based on multipath channel and device.

Background technology

OFDM (Orthogonal Frequency Division Multiplexing, OFDM) as a kind of quadrature carrier modulation technology, there is the higher availability of frequency spectrum and good anti-multipath jamming ability, be widely used in forth generation mobile communication (4G) and power line communication.OFDM modulation adopts the pattern of framing transmission, and an OFDM frame comprises the sinusoidal subcarrier of L MQAM or MPSK modulation.

But existing ofdm system, under multipath channel during the scene of high s/n ratio, the fractional part of frequency offset estimated accuracy of ofdm system is lower, makes the bit error rate of ofdm system higher.Its reason is, existing ofdm system does not consider the multipath effect occurred in multipath channel, and there is fractional part of frequency offset in ofdm system itself, energy leakage is had between subcarrier, because each subcarrier includes the interference from other subcarrier, therefore destroy the orthogonality between subcarrier, have impact on system bit error rate BER performance, make the bit error rate of ofdm system higher.

Summary of the invention

The object of the embodiment of the present invention is to provide a kind of ofdm system fractional part of frequency offset method of estimation based on multipath channel, be intended to solve existing ofdm system, under multipath channel during the scene of high s/n ratio, the fractional part of frequency offset estimated accuracy of ofdm system is lower, makes the problem that the bit error rate of ofdm system is higher.

The embodiment of the present invention is achieved in that a kind of ofdm system fractional part of frequency offset method of estimation based on multipath channel, comprising:

Obtain OFDM signal;

Estimate the time delay of described ofdm signal through multipath channel, obtain maximum delay, described maximum delay is through multipath channel maximum time of delay;

According to described maximum delay and described ofdm signal, obtain the sampled point of impact not affected by inter-symbol interference in Cyclic Prefix;

The sampled point utilizing impact not affected by inter-symbol interference in Cyclic Prefix and the correlation be replicated between partial data, carry out fractional part of frequency offset estimation, described in be replicated partial data and comprise the sampled point be replicated in the OFDM symbol received.

Another object of the embodiment of the present invention is to provide a kind of ofdm system fractional part of frequency offset estimation unit based on multipath channel, comprising:

Ofdm signal acquisition module, for obtaining OFDM signal;

Maximum delay estimation module, for estimating the time delay of described ofdm signal through multipath channel, obtains maximum delay, and described maximum delay is through multipath channel maximum time of delay;

Sampled point obtains module, for according to described maximum delay and described ofdm signal, obtains the sampled point of impact not affected by inter-symbol interference in Cyclic Prefix;

Fractional part of frequency offset estimation module, for the sampled point that utilizes impact not affected by inter-symbol interference in Cyclic Prefix and the correlation be replicated between partial data, carry out fractional part of frequency offset estimation, described in be replicated partial data and comprise the sampled point be replicated in the OFDM symbol received.

In embodiments of the present invention, the sampled point utilizing impact not affected by inter-symbol interference in Cyclic Prefix and the correlation be replicated between partial data, carry out fractional part of frequency offset estimation, solve existing ofdm system, under multipath channel during the scene of high s/n ratio, the fractional part of frequency offset estimated accuracy of ofdm system is lower, makes the problem that the bit error rate of ofdm system is higher.Under multipath channel high s/n ratio scene under, improve the fractional part of frequency offset estimated accuracy of ofdm system, thus reduce the bit error rate of ofdm system.

Accompanying drawing explanation

Fig. 1 is the structured flowchart of the ofdm signal baseband transmission model that prior art provides;

Fig. 2 is the realization flow figure of the ofdm system fractional part of frequency offset method of estimation based on multipath channel that the embodiment of the present invention provides;

Fig. 3 is the implementing procedure figure of the ofdm system fractional part of frequency offset method of estimation step S202 based on multipath channel that the embodiment of the present invention provides;

Fig. 4 is the implementing procedure figure of the step S301 that the embodiment of the present invention provides;

Fig. 5 a is the first structured flowchart of the OFDM symbol that the embodiment of the present invention provides;

Fig. 5 b is the second structured flowchart of the OFDM symbol that the embodiment of the present invention provides;

Fig. 6 is the first structured flowchart of the ofdm system fractional part of frequency offset estimation unit based on multipath channel that the embodiment of the present invention provides;

Fig. 7 is the second structured flowchart of the ofdm system fractional part of frequency offset estimation unit based on multipath channel that the embodiment of the present invention provides;

Fig. 8 is the 3rd structured flowchart of the ofdm system fractional part of frequency offset estimation unit based on multipath channel that the embodiment of the present invention provides;

Fig. 9 is the 4th structured flowchart of the ofdm system fractional part of frequency offset estimation unit based on multipath channel that the embodiment of the present invention provides.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

With reference to the structured flowchart that figure 1, Fig. 1 is the ofdm signal baseband transmission model that prior art provides;

As shown in Figure 1, in whole transmitting procedure, transmitting terminal is through N _cthe signal that some IDFT conversion generates was expressed as before carrying out up-conversion:

$x_{n,l}=\frac{1}{\sqrt{N_c}}\underset{k=0}{\overset{N_c-1}{\mathrm{\Σ}}}{c}_{n,k}\·e^{j\frac{2\mathrm{\πkl}}{N_c}}---\left(1\right)$

Wherein c _n,k(0≤k≤N _c-1) a kth subcarrier data of the n-th OFDM symbol is represented, and x _n,l(0≤l≤N _c+ N _g-1) l sampled data of the n-th OFDM symbol is represented.Due to separate between subcarrier data in prosign, when N is enough large, from formula (1) according to central-limit theorem (CLT), x _n,lapproximate obey the multiple Gaussian Profile that average is 0, but due to the existence of Cyclic Prefix, it not white.

Suppose that signal is by multipath channel, then channel can be modeled as FIR model, can be expressed as:

$h_l=\underset{m=0}{\overset{M-1}{\mathrm{\Σ}}}{h}_m\mathrm{\δ}(l-t_m)---\left(2\right)$

Wherein h _mfor decay factor, Rayleigh distributed and separate, supposes here t _mfor channel latency.The signal that the ofdm signal that ofdm signal receiving terminal receives obtains after down-conversion is:

$r_{n,l}=(x_{n,l}\⊗h_l)\·e^{-j\frac{{2\mathrm{\π\Δf}}_{c}l}{{\mathrm{\ΔfN}}_c}}+{\mathrm{\ω}}_{n,l}=\underset{m=0}{\overset{M-1}{\mathrm{\Σ}}}(x_{n,l-t_m}\·h_m)\·e^{-j\frac{2\mathrm{\π\ϵl}}{N_c}}+{\mathrm{\ω}}_{n,l}---\left(3\right)$

Wherein Δ f _crepresent carrier wave frequency deviation, Δ f represents the carrier spacing, ω _n,lrepresent that average is 0, variance is multiple Gaussian noise, fractional part of frequency offset after expression Δ f is normalized, represent convolution.

At this, acquiescence ofdm signal receiving terminal has reached that sampling clock is synchronous, sign synchronization and integer frequency offset are accurately estimated, only studies the estimation of the fractional part of frequency offset of the ofdm signal received.

embodiment one

Fig. 2 is the realization flow figure of the ofdm system fractional part of frequency offset method of estimation based on multipath channel that the embodiment of the present invention provides, and details are as follows:

In step s 201, OFDM signal is obtained;

In step S202, estimate, obtain maximum delay to the time delay of described ofdm signal through multipath channel, described maximum delay is through multipath channel maximum time of delay;

In step S203, according to described maximum delay and described ofdm signal, obtain the sampled point of impact not affected by inter-symbol interference in Cyclic Prefix;

In step S204, the sampled point utilizing impact not affected by inter-symbol interference in Cyclic Prefix and the correlation be replicated between partial data, carry out fractional part of frequency offset estimation, described in be replicated partial data and comprise the sampled point be replicated in the OFDM symbol received.

The sampled point utilizing impact not affected by inter-symbol interference in Cyclic Prefix and the sequence of correlation values be replicated between partial data, carry out fractional part of frequency offset estimation, described in be replicated partial data and comprise the sampled point be replicated in the OFDM symbol received.

Wherein, between the sampled point be replicated in the sampled point of impact not affected by inter-symbol interference and the OFDM symbol that receives, there is corresponding relation.

Wherein, before step S202 or S201, configuration sampled point scope Confirming model, described sampled point scope Confirming model is:

$\mathrm{\θ}\left(\mathrm{\λ}\right)=\frac{1}{P\·(N_g-\mathrm{\λ})}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}\underset{k=\mathrm{\λ}}{\overset{N_g-1}{\mathrm{\Σ}}}\left|r_{p,k}{r}_{p,k+N_c}^{*}\right|;$

${\mathrm{\λ}}_{\mathrm{opt}}=\arg \underset{\mathrm{\λ}\∈G_1\∪G_2}{\max }\left\{\mathrm{\θ}\left(\mathrm{\λ}\right)\right\};$

Wherein, λ is the Cyclic Prefix original position of setting, and P is the OFDM symbol number of carrying out related operation, N _gfor the sampled point number of Cyclic Prefix in OFDM symbol, r _p,kfor the kth sampled data in p symbol receiving, for r _p,kthe correlation being replicated data corresponding thereto, θ is the selected Cyclic Prefix part mean value being replicated the correlation of data corresponding thereto in P symbol, G ₁for being subject to last symbol-interference part in Cyclic Prefix, G ₂for part not affected by inter-symbol interference in Cyclic Prefix;

Wherein, λ _optfor preferred original position, i.e. G ₂original position, λ _optbe defined as λ from described G ₁be increased to described G ₂in make θ (λ) reach maximum first value.

In embodiments of the present invention, utilize the correlation of the sampled point be replicated in the sampled point of the impact not affected by inter-symbol interference OFDM symbol received corresponding with it, frequency deviation is estimated.Not needing the prior information of known channel, when being in high s/n ratio under multipath channel, can well estimate the fractional part of frequency offset of ofdm system.

embodiment two

Fig. 3 is the implementing procedure figure of the ofdm system fractional part of frequency offset method of estimation step S202 based on multipath channel that the embodiment of the present invention provides, and details are as follows:

In step S301, according to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determine the sampled point scope in Cyclic Prefix;

In step s 302, in described Cyclic Prefix, search sampled point according to described sampled point scope, obtain the sampled point of impact not affected by inter-symbol interference in described Cyclic Prefix.

In embodiments of the present invention, according to sampled point scope, in described Cyclic Prefix, to sampled point, the follow-up calculating carrying out correlation can be convenient to by fast searching.

embodiment three

Fig. 4 is the implementing procedure figure of the step S301 that the embodiment of the present invention provides, and details are as follows:

Step S401, according to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determines preferred original position;

Step S402, according to described preferred original position, determines the sampled point scope in Cyclic Prefix.

In embodiments of the present invention, determine the sampled point scope in Cyclic Prefix, be convenient to follow-up according to sampled point scope, can in described Cyclic Prefix fast searching to sampled point.

embodiment four

Present embodiment describes the ofdm system fractional part of frequency offset method of estimation based on multipath channel, implementing procedure in actual applications, details are as follows:

With reference to the first structured flowchart that figure 5a, Fig. 5 a is the OFDM symbol that the embodiment of the present invention provides;

With reference to the second structured flowchart that figure 5b, Fig. 5 b is the OFDM symbol that the embodiment of the present invention provides;

With reference to figure 5a, observe two symbols of the ofdm signal after sign synchronization received, the indexed set of define symbol is combined into:

$G_1\underset{=}{\mathrm{\Δ}}\{\mathrm{0,1},......,t_{M-1}-1\},---\left(4\right)$

$G_2\underset{=}{\mathrm{\Δ}}\{t_{M-1},......,N_g-1\},---\left(5\right)$

$G_3\underset{=}{\mathrm{\Δ}}\{N_g,......,{N_g+t}_{M-1}-1\}---\left(6\right)$

$G_i^{\′}\underset{=}{\mathrm{\Δ}}{G}_i+N_c,i=\mathrm{1,2,3}---\left(7\right)$

Wherein t _m-1for maximum delay, N _gfor the length of Cyclic Prefix, N _cfor valid data length.

Due to first OFDM symbol G _iin signal data be first and second OFDM symbol G _i' in the copying of signal data, utilize G _iin signal data and G _i' in the correlation of signal data, following correlation matrix can be obtained when ignoring intersymbol interference:

Wherein, r _{1, j}what represent is data after first symbol time delay on this sampled point, when k gets G ₃in data time, a jth sampled point, not in first symbol, supposes the G in second symbol here ₃' part is the virtual part of first symbol.

With reference to figure 5b, G ₁and G ₁', G ₃and G ₃' when carrying out related operation, there is the computing in sampled point and second OFDM symbol between sampled point in first OFDM symbol, this pattern (8) just can be rewritten as:

Wherein R _iSI1and R _iSI2be all the correlation introduced due to intersymbol related operation, be called intersymbol interference.

From analyzing above, when estimating frequency deviation, if to G _i, i=1,2, data all in 3 carry out related operation, can disturb, apply traditional frequency deviation estimating method based on maximum likelihood and can introduce error due to intersymbol interference between created symbol.

When carrying out related operation, can G only on impact not affected by inter-symbol interference ₂and G' ₂in data carry out computing, the fractional part of frequency offset estimated accuracy obtained like this will increase.

First need to search G ₂in data area, so define a new function # (λ) here.

$\mathrm{\θ}\left(\mathrm{\λ}\right)=\frac{1}{P\·(N_g-\mathrm{\λ})}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}\underset{k=\mathrm{\λ}}{\overset{N_g-1}{\mathrm{\Σ}}}\left|r_{p,k}{r}_{p,k+N_c}^{*}\right|---\left(10\right)$

Wherein λ is step-length, is a natural number, and θ can be used for finding G ₂in data.Can obtain according to the correlation between sampled point, as λ ∈ G ₁time, θ increases along with the increase of λ, when λ increases to G ₂time middle, θ reaches maximum, and no longer changes along with the increase θ of λ.These character proves as follows:

For single OFDM symbol, known according to formula (8), sequence along with the increase of k increases progressively, and when k increases to G ₂time middle, this sequence reaches maximum and no longer changes.For multinomial with if they to be write as the summation form of λ (k-λ) item, then each of front formula is greater than each of rear formula.Then can obtain

$\mathrm{\λ}\left(\underset{i=\mathrm{\λ}+1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\right)\≥(k-\mathrm{\λ})\left(\underset{i=1}{\overset{\mathrm{\λ}}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\right)---\left(11\right)$

$\mathrm{\λ}\left(\underset{i=\mathrm{\λ}+1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\right)+(k-\mathrm{\λ})\left(\underset{i=\mathrm{\λ}+1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\right)\≥(k-\mathrm{\λ})\left(\underset{i=1}{\overset{\mathrm{\λ}}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\right)+(k-\mathrm{\λ})\left(\underset{i=\mathrm{\λ}+1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\right)---\left(12\right)$

$k\left(\underset{i=\mathrm{\λ}+1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\right)\≥(k-\mathrm{\λ})\left(\underset{i=1}{\overset{\mathrm{\λ}}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\right)---\left(13\right)$

$\frac{\underset{i=\mathrm{\λ}+1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i}{k-\mathrm{\λ}}\≥\frac{\underset{i=1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i}{k}---\left(14\right)$

This character is generalized to P OFDM symbol, can obtains:

$\frac{1}{P(k-\mathrm{\λ})}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}\underset{i=\mathrm{\λ}+1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i\≥\frac{1}{P\·k}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}\underset{i=1}{\overset{k}{\mathrm{\Σ}}}{\mathrm{\γ}}_i---\left(15\right)$

Like this, the character that θ (λ) increases along with the increase of λ must be demonstrate,proved.

Here the correlation that intersymbol interference causes processed as noise, when channel maximum delay is much smaller than the Cyclic Prefix of OFDM symbol, its impact is herein negligible.According to the character that θ increases progressively, the fractional part of frequency offset method of estimation of the application can be obtained:

${\mathrm{\λ}}_{\mathrm{opt}}=\arg \underset{\mathrm{\λ}\∈G_1\∪G_2}{\max }\left\{\mathrm{\θ}\left(\mathrm{\λ}\right)\right\}---\left(16\right)$

Wherein, λ is the Cyclic Prefix original position of setting, and P is the OFDM symbol number of carrying out related operation, N _gfor the sampled point number of Cyclic Prefix in OFDM symbol, r _p,kfor the kth sampled data in p symbol receiving, for r _p,kthe correlation being replicated data corresponding thereto, θ is the selected Cyclic Prefix part mean value being replicated the correlation of data corresponding thereto in P symbol, G ₁for being subject to last symbol-interference part in Cyclic Prefix, G ₂for part not affected by inter-symbol interference in Cyclic Prefix;

Wherein, λ _optfor preferred original position, i.e. G ₂original position, λ _optbe defined as λ from described G ₁be increased to described G ₂in make θ (λ) reach maximum first value.

From analyzing above, λ _opt∈ G ₂, and when λ increases to G ₂time, reach maximum, no longer change.So λ _optthere is multiple value, here by λ _optbe defined as λ from G ₁be increased to G ₂in make θ (λ) reach maximum first value.

embodiment five

Fig. 6 is the first structured flowchart of the ofdm system fractional part of frequency offset estimation unit based on multipath channel that the embodiment of the present invention provides, and can should run in vehicle based on the ofdm system fractional part of frequency offset estimation unit of multipath channel.For convenience of explanation, illustrate only part related to the present embodiment.

With reference to Fig. 6, based on the ofdm system fractional part of frequency offset estimation unit of multipath channel, should comprise:

Ofdm signal acquisition module 61, for obtaining OFDM signal;

Maximum delay estimation module 62, for estimating the time delay of described ofdm signal through multipath channel, obtains maximum delay, and described maximum delay is through multipath channel maximum time of delay;

Sampled point obtains module 63, for according to described maximum delay and described ofdm signal, obtains the sampled point of impact not affected by inter-symbol interference in Cyclic Prefix;

Fractional part of frequency offset estimation module 64, for the sampled point that utilizes impact not affected by inter-symbol interference in Cyclic Prefix and the correlation be replicated between partial data, carry out fractional part of frequency offset estimation, described in be replicated partial data and comprise the sampled point be replicated in the OFDM symbol received.

In a kind of implementation of the present embodiment, in this ofdm system fractional part of frequency offset estimation unit based on multipath channel, the ofdm signal that described ofdm signal acquisition module is launched specifically for being received OFDM transmitter by antenna.

In a kind of implementation of the present embodiment, be the second structured flowchart of the ofdm system fractional part of frequency offset estimation unit based on multipath channel that the embodiment of the present invention provides with reference to figure 7, Fig. 7, described sampled point obtains module 63, comprising:

Sampled point scope determining unit 631, for according to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determines the sampled point scope in Cyclic Prefix;

Sampled point obtains unit 632, for searching sampled point according to described sampled point scope in described Cyclic Prefix, obtains the sampled point of impact not affected by inter-symbol interference in described Cyclic Prefix.

In a kind of implementation of the present embodiment, with reference to figure 8, Fig. 8 is the 3rd structured flowchart of the ofdm system fractional part of frequency offset estimation unit based on multipath channel that the embodiment of the present invention provides, and in this ofdm system fractional part of frequency offset estimation unit based on multipath channel, also comprises:

Configuration module 65, for configuring sampled point scope Confirming model, described sampled point scope Confirming model is:

$\mathrm{\θ}\left(\mathrm{\λ}\right)=\frac{1}{P\·(N_g-\mathrm{\λ})}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}\underset{k=\mathrm{\λ}}{\overset{N_g-1}{\mathrm{\Σ}}}\left|r_{p,k}{r}_{p,k+N_c}^{*}\right|;$

${\mathrm{\λ}}_{\mathrm{opt}}=\arg \underset{\mathrm{\λ}\∈G_1\∪G_2}{\max }\left\{\mathrm{\θ}\left(\mathrm{\λ}\right)\right\};$

Wherein, λ is the Cyclic Prefix original position of setting, and P is the OFDM symbol number of carrying out related operation, N _gfor the sampled point number of Cyclic Prefix in OFDM symbol, r _p,kfor the kth sampled data in p symbol receiving, for r _p,kthe correlation being replicated data corresponding thereto, θ is the selected Cyclic Prefix part mean value being replicated the correlation of data corresponding thereto in P symbol, G ₁for being subject to last symbol-interference part in Cyclic Prefix, G ₂for part not affected by inter-symbol interference in Cyclic Prefix;

Wherein, λ _optfor preferred original position, i.e. G ₂original position, λ _optbe defined as λ from described G ₁be increased to described G ₂in make θ (λ) reach maximum first value.

In a kind of implementation of the present embodiment, with reference to figure 9, Fig. 9 is the 4th structured flowchart of the ofdm system fractional part of frequency offset estimation unit based on multipath channel that the embodiment of the present invention provides, in this ofdm system fractional part of frequency offset estimation unit based on multipath channel, described sampled point scope determining unit 632, comprising:

First determines subelement 6321, for according to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determines preferred original position;

Second determines subelement 6322, for according to described preferred original position, determines the sampled point scope in Cyclic Prefix.

The device that the embodiment of the present invention provides can be applied in the embodiment of the method for aforementioned correspondence, and details, see the description of above-described embodiment, do not repeat them here.

Through the above description of the embodiments, those skilled in the art can be well understood to the mode that the present invention can add required common hardware by software and realizes.Described program can be stored in read/write memory medium, described storage medium, as random asccess memory, flash memory, read-only memory, programmable read only memory, electrically erasable programmable memory, register etc.This storage medium is positioned at memory, and processor reads the information in memory, performs the method described in each embodiment of the present invention in conjunction with its hardware.

The above; be only the specific embodiment of the present invention, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Claims (10)

1., based on an ofdm system fractional part of frequency offset method of estimation for multipath channel, it is characterized in that, comprising:

Obtain OFDM signal;

Estimate the time delay of described ofdm signal through multipath channel, obtain maximum delay, described maximum delay is through multipath channel maximum time of delay;

According to described maximum delay and described ofdm signal, obtain the sampled point of impact not affected by inter-symbol interference in Cyclic Prefix;

The sampled point utilizing impact not affected by inter-symbol interference in Cyclic Prefix and the correlation be replicated between partial data, carry out fractional part of frequency offset estimation, described in be replicated partial data and comprise the sampled point be replicated in the OFDM symbol received.

2., as claimed in claim 1 based on the ofdm system fractional part of frequency offset method of estimation of multipath channel, it is characterized in that, described acquisition OFDM signal, is specially:

The ofdm signal of OFDM transmitter transmitting is received by antenna.

3., as claimed in claim 1 based on the ofdm system fractional part of frequency offset method of estimation of multipath channel, it is characterized in that, described according to described maximum delay and described ofdm signal, obtain the sampled point of impact not affected by inter-symbol interference in Cyclic Prefix, be specially:

According to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determine the sampled point scope in Cyclic Prefix;

In described Cyclic Prefix, search sampled point according to described sampled point scope, obtain the sampled point of impact not affected by inter-symbol interference in described Cyclic Prefix.

4. as claimed in claim 3 based on the ofdm system fractional part of frequency offset method of estimation of multipath channel, it is characterized in that, described according to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, before determining the sampled point scope in Cyclic Prefix, comprising:

Configuration sampled point scope Confirming model, described sampled point scope Confirming model is:

$\mathrm{\θ}\left(\mathrm{\λ}\right)=\frac{1}{P\·(N_g-\mathrm{\λ})}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}\underset{k=\mathrm{\λ}}{\overset{N_g-1}{\mathrm{\Σ}}}\left|r_{p,k}{r}_{p,k+N_c}^{*}\right|;$

${\mathrm{\λ}}_{\mathrm{opt}}=\arg \underset{\mathrm{\λ}\∈G_1\∪G_2}{\max }\left\{\mathrm{\θ}\left(\mathrm{\λ}\right)\right\};$

Wherein, λ is the Cyclic Prefix original position of setting, and P is the OFDM symbol number of carrying out related operation, N _gfor the sampled point number of Cyclic Prefix in OFDM symbol, r _p,kfor the kth sampled data in p symbol receiving, for r _p,kthe correlation being replicated data corresponding thereto, θ is the selected Cyclic Prefix part mean value being replicated the correlation of data corresponding thereto in P symbol, G ₁for being subject to last symbol-interference part in Cyclic Prefix, G ₂for part not affected by inter-symbol interference in Cyclic Prefix;

Wherein, λ _optfor preferred original position, i.e. G ₂original position, λ _optbe defined as λ from described G ₁be increased to described G ₂in make θ (λ) reach maximum first value.

5. as claimed in claim 4 based on the ofdm system fractional part of frequency offset method of estimation of multipath channel, it is characterized in that, described according to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determine the sampled point scope in Cyclic Prefix, be specially:

According to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determine preferred original position;

According to described preferred original position, determine the sampled point scope in Cyclic Prefix.

6., based on an ofdm system fractional part of frequency offset estimation unit for multipath channel, it is characterized in that, comprising:

Ofdm signal acquisition module, for obtaining OFDM signal;

Maximum delay estimation module, for estimating the time delay of described ofdm signal through multipath channel, obtains maximum delay, and described maximum delay is through multipath channel maximum time of delay;

Sampled point obtains module, for according to described maximum delay and described ofdm signal, obtains the sampled point of impact not affected by inter-symbol interference in Cyclic Prefix;

Fractional part of frequency offset estimation module, for the sampled point that utilizes impact not affected by inter-symbol interference in Cyclic Prefix and the correlation be replicated between partial data, carry out fractional part of frequency offset estimation, described in be replicated partial data and comprise the sampled point be replicated in the OFDM symbol received.

7. as claimed in claim 6 based on the ofdm system fractional part of frequency offset estimation unit of multipath channel, it is characterized in that, the ofdm signal that described ofdm signal acquisition module is launched specifically for being received OFDM transmitter by antenna.

8., as claimed in claim 6 based on the ofdm system fractional part of frequency offset estimation unit of multipath channel, it is characterized in that, described sampled point obtains module, comprising:

Sampled point scope determining unit, for according to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determines the sampled point scope in Cyclic Prefix;

Sampled point obtains unit, for searching sampled point according to described sampled point scope in described Cyclic Prefix, obtains the sampled point of impact not affected by inter-symbol interference in described Cyclic Prefix.

9., as claimed in claim 8 based on the ofdm system fractional part of frequency offset estimation unit of multipath channel, it is characterized in that, the described ofdm system fractional part of frequency offset estimation unit based on multipath channel also comprises:

Configuration module, for configuring sampled point scope Confirming model, described sampled point scope Confirming model is:

$\mathrm{\θ}\left(\mathrm{\λ}\right)=\frac{1}{P\·(N_g-\mathrm{\λ})}\underset{p=1}{\overset{P}{\mathrm{\Σ}}}\underset{k=\mathrm{\λ}}{\overset{N_g-1}{\mathrm{\Σ}}}\left|r_{p,k}{r}_{p,k+N_c}^{*}\right|;$

${\mathrm{\λ}}_{\mathrm{opt}}=\arg \underset{\mathrm{\λ}\∈G_1\∪G_2}{\max }\left\{\mathrm{\θ}\left(\mathrm{\λ}\right)\right\};$

Wherein, λ is the Cyclic Prefix original position of setting, and P is the OFDM symbol number of carrying out related operation, N _gfor the sampled point number of Cyclic Prefix in OFDM symbol, r _p,kfor the kth sampled data in p symbol receiving, for r _p,kthe correlation being replicated data corresponding thereto, θ is the selected Cyclic Prefix part mean value being replicated the correlation of data corresponding thereto in P symbol, G ₁for being subject to last symbol-interference part in Cyclic Prefix, G ₂for part not affected by inter-symbol interference in Cyclic Prefix;

Wherein, λ _optfor preferred original position, i.e. G ₂original position, λ _optbe defined as λ from described G ₁be increased to described G ₂in make θ (λ) reach maximum first value.

10., as claimed in claim 9 based on the ofdm system fractional part of frequency offset estimation unit of multipath channel, it is characterized in that, described sampled point scope determining unit, comprising:

First determines subelement, for according to described maximum delay, described ofdm signal and pre-configured sampled point scope Confirming model, determines preferred original position;

Second determines subelement, for according to described preferred original position, determines the sampled point scope in Cyclic Prefix.