CN102025663A - Estimation method and device of orthogonal frequency division multiplexing (OFDM) synchronous position - Google Patents

Abstract

The embodiment of the invention discloses an estimation method and device of an orthogonal frequency division multiplexing (OFDM) synchronous position. The method comprises the following steps of dividing a signal to be segmented into a first segmentation signal and a second segmentation signal after receiving the cycle prefix (CP) of an OFDM symbol; respectively carrying out separation on training sequences and data symbols in the first segmentation signal and the second segmentation signal; calculating the signal to noise ratio of the first segmentation signal and the second segmentation signal according to the separated training sequences and data symbols; searching a synchronous reference position of the OFDM symbol according to a bisection recursion mode by comparing the signal to noise ratios of the first segmentation signal and the second segmentation signal; and obtaining a synchronous initial position of an effective data part of the OFDM symbol according to the synchronous reference position. The embodiment of the invention can start synchronous estimation once receiving the CP, obtains the synchronous initial position of an OFDM effective data symbol through a recursion method by comparing the signal to noise ratios of the segmentation signals and has the advantages that the structure is simple and the synchronization speed is rapid.

Description

OFDM sync bit method of estimation and device

Technical field

The application relates to communication technical field, particularly relates to a kind of OFDM based on CP (Cyclic Prefix, Cyclic Prefix) (Orthogonal Frequency Division Multiplexing, OFDM) location estimation method and device.

Background technology

OFDM is that a kind of data stream modulates with two-forty becomes a plurality of sub data flows than low rate, the technology that communicates by the physical channel that is divided into a plurality of sub-carriers again.The OFDM technology has been applied in such as in the communication systems such as data broadcasting and Digital Television, and among WLAN standard IEEE802.11 and the wireless MAN IEEE802.16.The OFDM symbol is made of a plurality of sub-carrier signal stacks, utilize orthogonality to distinguish between each subcarrier, therefore in order to ensure the orthogonality of ofdm system, need recipient and transmit leg to carry out strict time synchronized and carrier synchronization, could correctly receive data.

The inventor finds that in the research process to prior art ofdm system adopts the data supplementary mode to carry out synchronously usually in the prior art, and this mode need be used a plurality of OFDM transmission of data blocks frequency pilot signs or training sequence, causes the wasting of resources thus; And the recipient could start estimation synchronously, the loss that brings information rate thus after need receiving complete data.

Summary of the invention

In order to solve the problems of the technologies described above, the embodiment of the present application provides a kind of OFDM sync bit method of estimation and device, estimates that to solve existing sync bit mode causes the wasting of resources easily, and brings the problem of information rate loss.

The embodiment of the present application discloses following technical scheme:

A kind of OFDM sync bit method of estimation comprises:

Receive the cyclic prefix CP of OFDM symbol, described CP comprises training sequence and the data symbol with equal transmit power;

To treat that block signal is divided into two segment signals, and be respectively first segment signal and second segment signal, the described block signal for the treatment of belongs to described CP;

Respectively described first segment signal is separated with data symbol with training sequence in second segment signal;

Calculate the signal to noise ratio of described first segment signal and second segment signal according to training sequence separated and data symbol;

By the signal to noise ratio of more described first segment signal and second segment signal, search the reference synchronization position of described OFDM symbol according to the bisection recursive fashion;

Obtain the synchronous original position of described OFDM symbol valid data part according to described reference synchronization position.

The described signal to noise ratio of calculating described first segment signal and second segment signal according to training sequence separated and data symbol comprises:

Calculate the training sequence in described first segment signal and second segment signal and the auto-correlation function of data symbol respectively;

Respectively the estimation of the auto-correlation function of data symbol in first segment signal and second segment signal is estimated as signal power, and the estimation of training sequence is estimated as noise power;

The ratio that the signal power estimation and the noise power of described first segment signal and second segment signal are estimated is as the signal to noise ratio of described first segment signal and second segment signal respectively.

Described reference synchronization position of searching described OFDM symbol according to the bisection recursive fashion comprises:

When the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is in preset range, export the reference synchronization position of the position at first sampling point place behind described second segment signal as described OFDM symbol;

When the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is not in preset range, if the signal to noise ratio of described first segment signal is less than the signal to noise ratio of described second segment signal, extract described second segment signal as the described block signal for the treatment of, return the described block signal of will treating and be divided into the step of two segment signals;

When the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is not in preset range, if the signal to noise ratio of described first segment signal is greater than the signal to noise ratio of described second segment signal, extract described first segment signal as the described block signal for the treatment of, return the described block signal of will treating and be divided into the step of two segment signals.

The described synchronous original position that obtains described OFDM symbol valid data part according to described reference synchronization position comprises:

With the position at first sampling point place of described CP as the reference point, judge described reference synchronization position to the distance between the described reference point whether less than half of described CP length;

If described distance is less than half of described CP length, then described reference synchronization position is added position after the above CP length as the synchronous original position of described OFDM symbol valid data part, if described distance is greater than half of described CP length, then with the synchronous original position of described reference synchronization position as described OFDM symbol valid data part.

Described will treat that block signal is divided into two segment signals before, also comprise:

Judge that whether the described number of samples of block signal for the treatment of is greater than 1;

If described number of samples greater than 1, is then carried out the described block signal for the treatment of is divided into two segment signals,, then export the reference synchronization position of the position at described sampling point place as described OFDM symbol if described number of samples equals 1.

A kind of OFDM sync bit estimation unit comprises:

Receiving element is used to receive the cyclic prefix CP of OFDM symbol, and described CP comprises training sequence and the data symbol with equal transmit power;

Segmenting unit is used for being respectively first segment signal and second segment signal with treating that block signal is divided into two segment signals, and the described block signal for the treatment of belongs to described CP;

Separative element is used for respectively the training sequence of described first segment signal and second segment signal is separated with data symbol;

Computing unit is used for calculating according to training sequence separated and data symbol the signal to noise ratio of described first segment signal and second segment signal;

Search the unit, be used for signal to noise ratio, search the reference synchronization position of described OFDM symbol according to the bisection recursive fashion by more described first segment signal and second segment signal;

Obtain the unit, be used for obtaining the synchronous original position of described OFDM symbol valid data part according to described reference synchronization position.

Described computing unit comprises:

The auto-correlation function computing unit is used for calculating respectively the training sequence of described first segment signal and second segment signal and the auto-correlation function of data symbol;

Power estimation unit is used for respectively the estimation of the auto-correlation function of first segment signal and the second segment signal data symbol is estimated as signal power, and the estimation of training sequence is estimated as noise power;

The signal to noise ratio acquiring unit, be used for respectively the signal power of described first segment signal and second segment signal estimated and the ratio of noise power estimation as the signal to noise ratio of described first segment signal and second segment signal.

The described unit of searching comprises:

First comparing unit, whether the difference of signal to noise ratio that is used for the signal to noise ratio of comparison first segment signal and described second segment signal is in preset range;

First performance element, be used for difference when the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal in preset range the time, export the reference synchronization position of the position at first sampling point place behind described second segment signal as described OFDM symbol;

Second comparing unit is used for difference when the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal not in preset range the time, the signal to noise ratio of the signal to noise ratio of more described first segment signal and described second segment signal;

Second performance element, be used for when the signal to noise ratio of described first segment signal during less than the signal to noise ratio of described second segment signal, extract described second segment signal as the described block signal for the treatment of, and return described segmenting unit and carry out function corresponding, when the signal to noise ratio of described first segment signal during greater than the signal to noise ratio of described second segment signal, extract described first segment signal as the described block signal for the treatment of, return described segmenting unit and carry out function corresponding.

Described acquisition unit comprises:

Apart from judging unit, be used for position with first sampling point place of described CP as the reference point, judge described reference synchronization position to the distance between the described reference point whether less than half of described CP length;

The sync bit determining unit, if be used for described distance less than half of described CP length, then described reference synchronization position is added position after the above CP length as the synchronous original position of described OFDM symbol valid data part, if described distance is greater than half of described CP length, then with the synchronous original position of described reference synchronization position as described OFDM symbol valid data part.

Also comprise:

Judging unit is used to judge that whether the described number of samples of block signal for the treatment of is greater than 1;

Performance element if be used for described number of samples greater than 1, then trigger described segmenting unit and carries out function corresponding, if described number of samples equals 1, then exports the reference synchronization position of the position at described sampling point place as described OFDM symbol.

As can be seen from the above-described embodiment, after the embodiment of the present application receives the CP of OFDM symbol, to treat that block signal is divided into first segment signal and second segment signal, respectively first segment signal is separated with data symbol with training sequence in second segment signal, calculate the signal to noise ratio of first segment signal and second segment signal according to training sequence separated and data symbol, by comparing the signal to noise ratio of first segment signal and second segment signal, according to the reference synchronization position that the bisection recursive fashion is searched described OFDM symbol, obtain the synchronous original position of OFDM symbol valid data part according to the reference synchronization position.The embodiment of the present application just can start synchronously after receiving CP to be estimated, by the signal to noise ratio of block signal relatively, and draws the synchronous original position of OFDM valid data symbol by recursion method, calculating simply, synchronizing speed is fast; And compared with prior art,, reduced the redundancy of system, and can finish synchronously within a short period of time owing to need therefore can not influence the transmission rate of valid data part in the valid data partial stack training sequence and the pilot tone of transmission.

Description of drawings

In order to be illustrated more clearly in the embodiment of the present application or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is the first embodiment flow chart of the application OFDM sync bit method of estimation;

Fig. 2 A is the second embodiment flow chart of the application OFDM sync bit method of estimation;

Fig. 2 B is the structural representation of the application OFDM symbol;

Fig. 3 is the first embodiment block diagram of the application OFDM sync bit estimation unit;

Fig. 4 is the second embodiment block diagram of the application OFDM sync bit estimation unit.

Embodiment

The following embodiment of the present invention provides a kind of OFDM sync bit method of estimation and device.The synchronous original position of the signal to noise ratio difference estimating OFDM symbol valid data part between the signal after the segmentation is carried out in the embodiment of the present application utilization to CP.

In order to make those skilled in the art person understand technical scheme in the embodiment of the invention better, and the above-mentioned purpose of the embodiment of the invention, feature and advantage can be become apparent more, below in conjunction with accompanying drawing technical scheme in the embodiment of the invention is described in further detail.

Referring to Fig. 1, be the first embodiment flow chart of the application OFDM sync bit method of estimation.

Step 101: receive the CP of OFDM symbol, this CP comprises training sequence and the data symbol with equal transmit power.

In the embodiment of the present application, half is training sequence part for the data of Cyclic Prefix part, and half is the data symbol part.Therefore, transmitting terminal is when transmission OFDM symbol, and the training sequence in the Cyclic Prefix part and the transmitting power of data symbol are respectively half of total transmitting power.

Step 102: will treat that block signal is divided into first segment signal and second segment signal, this treats that block signal belongs to CP.

Step 103: respectively first segment signal is separated with data symbol with training sequence in second segment signal.

With first segment signal is example, when training sequence in separating first segment signal and data symbol, can adopt denoising to handle and obtain data symbol, deducts data symbol with first segment signal then, promptly obtains the training sequence of first segment signal.

Step 104: the signal to noise ratio of calculating first segment signal and second segment signal according to training sequence separated and data symbol.

Concrete, calculate the training sequence in described first segment signal and second segment signal and the auto-correlation function of data symbol respectively, respectively the estimation of the auto-correlation function of data symbol in first segment signal and second segment signal is estimated as signal power, and the estimation of training sequence estimated as noise power, respectively the signal power of described first segment signal and second segment signal is estimated and the ratio of noise power estimation as the signal to noise ratio of described first segment signal and second segment signal.

Step 105: by comparing the signal to noise ratio of first segment signal and second segment signal, the reference synchronization position of searching the OFDM symbol according to the bisection recursive fashion.

Concrete, when the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is in preset range, export the reference synchronization position of the position at first sampling point place behind described second segment signal as described OFDM symbol; When the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is not in preset range, if the signal to noise ratio of described first segment signal is less than the signal to noise ratio of described second segment signal, extract described second segment signal as the described block signal for the treatment of, return the described block signal of will treating and be divided into the step of two segment signals; When the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is not in preset range, if the signal to noise ratio of described first segment signal is greater than the signal to noise ratio of described second segment signal, extract described first segment signal as the described block signal for the treatment of, return the described block signal of will treating and be divided into the step of two segment signals.

Step 106: the synchronous original position that obtains OFDM symbol valid data part according to the reference synchronization position.

Concrete, with the position at first sampling point place of described CP as the reference point, judge described reference synchronization position to the distance between the described reference point whether less than half of described CP length; If described distance is less than half of described CP length, then described reference synchronization position is added position after the above CP length as the synchronous original position of described OFDM symbol valid data part, if described distance is greater than half of described CP length, then with the synchronous original position of described reference synchronization position as described OFDM symbol valid data part.

Referring to Fig. 2 A, be the second embodiment flow chart of the application OFDM sync bit method of estimation:

Step 201: receive the CP of OFDM symbol, this CP comprises training sequence and the data symbol with equal transmit power.

Referring to Fig. 2 B, be the structural representation of the application OFDM symbol.Each OFDM symbol partly is made up of Cyclic Prefix part and valid data, and wherein Cyclic Prefix partly is generally the end data of valid data part.In the embodiment of the present application, transmitting terminal need insert transmitting terminal and all known training sequence of receiving terminal in Cyclic Prefix before transmission OFDM symbol.Concrete operations are, training sequence is repeatedly repeated the sequence that equates with Cyclic Prefix, then this sequence and Cyclic Prefix are weighted, generate new Cyclic Prefix part, weight coefficient is 0.5, promptly shown in Fig. 2 B, half is training sequence part for the data of Cyclic Prefix part, and half is the data symbol part.Therefore, transmitting terminal is when transmission OFDM symbol, and the training sequence in the Cyclic Prefix part and the transmitting power of data symbol are respectively half of total transmitting power.Training sequence in the embodiment of the present application can be the time domain pseudo random sequence, satisfies mutually orthogonal characteristic, for example the m sequence.

At transmitting terminal, the modulation of OFDM symbol adopts IFFT (inverse fast fourier transform) to finish, so institute's OFDM symbols transmitted is discrete data, and discrete data is made up of some sampling points, so each OFDM symbol also can be regarded as by a plurality of sampling points and forms.

Receiving terminal is when receiving the OFDM symbol, at first receive the Cyclic Prefix part, usually the length of Cyclic Prefix can be set at 4 to 5 times of time delay expansion, so receiving terminal can be known according to the length (number of samples in other words) of received data and whether receives the Cyclic Prefix part.

Step 202: judge that whether the number of samples for the treatment of block signal is greater than 1, if then execution in step 203; Otherwise, execution in step 216.

In the embodiment of the present application, when initially receiving CP, treat that block signal is this complete CP, follow-up through signal to noise ratio relatively the block signal for the treatment of that returns is the part among the CP, promptly in the process of carrying out the bisection recurrence, treats that block signal all belongs to this CP.

Step 203: will treat that block signal is divided into first segment signal and second segment signal.

Step 204: respectively first segment signal is separated with data symbol with training sequence in second segment signal.

With first segment signal is example, when training sequence in separating first segment signal and data symbol, can adopt denoising to handle and obtain data symbol, deducts data symbol with first segment signal then, promptly obtains the training sequence of first segment signal.

Step 205: calculate the training sequence in first segment signal and second segment signal and the auto-correlation function of data symbol respectively.

With first segment signal is example, establishes that isolated data symbol is x (n) in first segment signal, and training sequence separated is r (n), and then Dui Ying auto-correlation function calculates according to following formula respectively:

R _xx(m)＝E[x ^*(n)x(n+m)]

R _rr(m)＝E[r ^*(n)r(n+m)]

In the following formula, R _Xx(m) be the auto-correlation function of data symbol, R _Rr(m) be the auto-correlation function of training sequence.Wherein, suppose total K sampling point in first segment signal, then m represents any one in K the sampling point.

The auto-correlation function computational process of the training sequence of second segment signal and data symbol is identical with first segment signal, does not repeat them here.

Step 206: respectively the estimation of the auto-correlation function of data symbol in first segment signal and second segment signal is estimated as signal power, and the estimation of training sequence is estimated as noise power.

Still be example with first segment signal, get data symbol in first segment signal and training sequence one sample time sequence, estimate according to the auto-correlation function of following formula calculated data symbol and training sequence with time averaging method:

${\hat{R}}_{\mathrm{xx}}\left(m\right)=\frac{1}{N}\underset{n=0}{\overset{N-1-\left|m\right|}{\mathrm{\Σ}}}x\left(n\right)x(n+m),\left|m\right|\≤N-1$

${\hat{R}}_{\mathrm{rr}}\left(m\right)=\frac{1}{N}\underset{n=0}{\overset{N-1-\left|m\right|}{\mathrm{\Σ}}}r\left(n\right)r(n+m),\left|m\right|\≤N-1$

In the following formula, N is the number of samples in sequence sample time, x (n)=x (0), x (1) ..., x (N-1) },

For the auto-correlation function of data symbol is estimated,

For the auto-correlation function of training sequence is estimated.

Further, according to following formula:

$x\left(n\right)*x(-n)=\underset{\mathrm{\τ}=-\∞}{\overset{\∞}{\mathrm{\Σ}}}x\left(\mathrm{\τ}\right)x(-m+\mathrm{\τ})=\underset{n=-\∞}{\overset{\∞}{\mathrm{\Σ}}}x\left(n\right)x(-m+n)$

Wherein, τ is-∞ any one integer the in+∞.

Can get following formula:

${\hat{R}}_{\mathrm{xx}}\left(m\right)=\frac{1}{N}x\left(n\right)*x(-n)$

${\hat{R}}_{\mathrm{rr}}\left(m\right)=\frac{1}{N}r\left(n\right)*r(-n)$

The estimation of signal power and noise power can be directly estimated draw by auto-correlation function, promptly as shown in the formula:

$\hat{S}={\hat{R}}_{\mathrm{xx}}\left(m\right)$

$\hat{N}={\hat{R}}_{\mathrm{rr}}\left(m\right)$

Wherein,

For signal power is estimated,

For noise power is estimated.Adopt said method to calculate the complexity that signal to noise ratio can simplified system, whole computational process relative error is less.

The signal power of second segment signal estimates that the computational process of estimating with noise power is identical with first segment signal, does not repeat them here.

Step 207: the ratio that the signal power estimation and the noise power of first segment signal and second segment signal are estimated is as the signal to noise ratio of described first segment signal and second segment signal respectively.

Signal to noise ratio is defined as the ratio of average power signal and noise average power, and establishing the signal to noise ratio that first segment signal calculates is SNR1, and then it calculates according to following formula:

$\mathrm{SNR}1=\frac{\hat{S}}{\hat{N}}$

In like manner, the signal to noise ratio that can try to achieve second segment signal is SNR2.

Step 208: whether the difference of signal to noise ratio of judging the signal to noise ratio of first segment signal and second segment signal is in preset range, if then execution in step 212; Otherwise, execution in step 209.

Promptly ask the absolute value of the signal to noise ratio difference of first segment signal and second segment signal, if the absolute value of this difference in preset range, then can be thought the snr value approximately equal of two segment signals.For example, SNR1 and SNR2 satisfy following approximation relation:

|SNR1-SNR2|≤0.01～0.09

Step 209: whether the signal to noise ratio of judging first segment signal is less than the signal to noise ratio of second segment signal, if then execution in step 210; Otherwise, execution in step 211.

Step 210: extract second segment signal as treating to return step 202 by block signal.

Step 211: extract first segment signal as treating to return step 202 by block signal.

Owing in the embodiment of the present application training sequence is inserted in the Cyclic Prefix, therefore can regard as in the data of Cyclic Prefix part and add noise, therefore the signal to noise ratio in the time of can be than plus noise not when receiving terminal calculates signal to noise ratio is little, and because the time delay expansion takes place, the data of other subcarriers if the data of the Cyclic Prefix that is therefore received part have superposeed, as effective data symbol etc., then can regard as has increased signal power, thereby signal to noise ratio can increase.Therefore in abovementioned steps 210 and step 211, take out the bigger segment signal of signal to noise ratio, continue to seek the reference synchronization position of OFDM symbol as treating to return step 202 by block signal.

Step 212: export the reference synchronization position of the position at first sampling point place behind second segment signal as the OFDM symbol.

Step 213: judge the reference synchronization position to the distance between the reference point whether less than half of CP length, if then execution in step 214; Otherwise, execution in step 215.

With the position at first sampling point place of CP as the reference point;

Step 214: the reference synchronization position is added that position after the CP length as the synchronous original position of OFDM symbol valid data part, finishes current flow process.

Step 215:, finish current flow process with the synchronous original position of reference synchronization position as OFDM symbol valid data part.

Step 216: export the reference synchronization position of the position at this sampling point place, return step 213 as the OFDM symbol.

When number of samples equals 1, illustrate that the judgement of bisection recurrence finishes, the position of this sampling point of being exported is the reference synchronization position of OFDM symbol.Since treat block signal before calculating signal to noise ratio through judgement, the number of samples of therefore treating block signal can be less than 1, so needn't consider that number of samples is less than 1 situation.

The foregoing description just can start synchronously after receiving CP to be estimated, by the signal to noise ratio of block signal relatively, and draws the synchronous original position of OFDM valid data symbol by recursion method, calculating simply, synchronizing speed is fast; And compared with prior art,, reduced the redundancy of system, and can finish synchronously within a short period of time owing to need therefore can not influence the transmission rate of valid data part in the valid data partial stack training sequence and the pilot tone of transmission.

Further, utilize the synchronous original position of the OFDM symbol valid data that obtain in the embodiment of the present application, calculate the position relation of synchronous start point and whole circulation prefix end, transmit this position relation information by processing section to the back-end, the reference that can be used as that subsequent communication channel is estimated and equilibrium etc. handled.Simultaneously, because the training sequence that inserts in the Cyclic Prefix is transmitting terminal and all known training sequence of receiving terminal, therefore can calculate performance index such as the error rate by with reference to the difference between training sequence that receives and the known training sequence.

Corresponding with the embodiment of the application OFDM sync bit method of estimation, the application also provides the embodiment of OFDM sync bit estimation unit.

Referring to Fig. 3, be the first embodiment block diagram of the application OFDM sync bit estimation unit:

This device comprises: receiving element 310, segmenting unit 320, separative element 330, computing unit 340, search unit 350 and obtain unit 360.

Wherein, receiving element 310 is used to receive the cyclic prefix CP of OFDM symbol, and described CP comprises training sequence and the data symbol with equal transmit power;

Segmenting unit 320 is used for being respectively first segment signal and second segment signal with treating that block signal is divided into two segment signals, and the described block signal for the treatment of belongs to described CP;

Separative element 330 is used for respectively the training sequence of described first segment signal and second segment signal is separated with data symbol;

Computing unit 340 is used for calculating according to training sequence separated and data symbol the signal to noise ratio of described first segment signal and second segment signal;

Search unit 350, be used for signal to noise ratio, search the reference synchronization position of described OFDM symbol according to the bisection recursive fashion by more described first segment signal and second segment signal;

Obtain unit 360, be used for obtaining the synchronous original position of described OFDM symbol valid data part according to described reference synchronization position.

Referring to Fig. 4, be the second embodiment block diagram of the application OFDM sync bit estimation unit:

This device comprises: receiving element 410, judging unit 420, performance element 430, segmenting unit 440, separative element 450, computing unit 460, search unit 470 and obtain unit 480.

Wherein, receiving element 410 is used to receive the cyclic prefix CP of OFDM symbol, and described CP comprises training sequence and the data symbol with equal transmit power;

Judging unit 420 is used to judge that whether the number of samples for the treatment of block signal is greater than 1;

Performance element 430 if be used for described number of samples greater than 1, then trigger described segmenting unit 440 and carries out function corresponding, if described number of samples equals 1, then exports the reference synchronization position of the position at described sampling point place as described OFDM symbol;

Segmenting unit 440 is used for being respectively first segment signal and second segment signal with treating that block signal is divided into two segment signals, and the described block signal for the treatment of belongs to described CP;

Separative element 450 is used for respectively the training sequence of described first segment signal and second segment signal is separated with data symbol;

Computing unit 460 is used for calculating according to training sequence separated and data symbol the signal to noise ratio of described first segment signal and second segment signal;

Search unit 470, be used for signal to noise ratio, search the reference synchronization position of described OFDM symbol according to the bisection recursive fashion by more described first segment signal and second segment signal;

Obtain unit 480, be used for obtaining the synchronous original position of described OFDM symbol valid data part according to described reference synchronization position.

Concrete, computing unit 460 can comprise (not shown among Fig. 4): the auto-correlation function computing unit is used for calculating respectively the training sequence of described first segment signal and second segment signal and the auto-correlation function of data symbol; Power estimation unit is used for respectively the estimation of the auto-correlation function of first segment signal and the second segment signal data symbol is estimated as signal power, and the estimation of training sequence is estimated as noise power; The signal to noise ratio acquiring unit, be used for respectively the signal power of described first segment signal and second segment signal estimated and the ratio of noise power estimation as the signal to noise ratio of described first segment signal and second segment signal.

Concrete, search unit 470 and can comprise (not shown among Fig. 4): first comparing unit, whether the difference of signal to noise ratio that is used for the signal to noise ratio of comparison first segment signal and described second segment signal is in preset range; First performance element, be used for difference when the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal in preset range the time, export the reference synchronization position of the position at first sampling point place behind described second segment signal as described OFDM symbol; Second comparing unit is used for difference when the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal not in preset range the time, the signal to noise ratio of the signal to noise ratio of more described first segment signal and described second segment signal; Second performance element, be used for when the signal to noise ratio of described first segment signal during less than the signal to noise ratio of described second segment signal, extract described second segment signal as the described block signal for the treatment of, and return described segmenting unit and carry out function corresponding, when the signal to noise ratio of described first segment signal during greater than the signal to noise ratio of described second segment signal, extract described first segment signal as the described block signal for the treatment of, return described segmenting unit and carry out function corresponding.

Concrete, obtain unit 480 and can comprise (not shown among Fig. 4): apart from judging unit, be used for position with first sampling point place of described CP as the reference point, judge described reference synchronization position to the distance between the described reference point whether less than half of described CP length; The sync bit determining unit, if be used for described distance less than half of described CP length, then described reference synchronization position is added position after the above CP length as the synchronous original position of described OFDM symbol valid data part, if described distance is greater than half of described CP length, then with the synchronous original position of described reference synchronization position as described OFDM symbol valid data part.

By as can be known to the description of above execution mode, after the embodiment of the present application receives the CP of OFDM symbol, to treat that block signal is divided into first segment signal and second segment signal, respectively first segment signal is separated with data symbol with training sequence in second segment signal, calculate the signal to noise ratio of first segment signal and second segment signal according to training sequence separated and data symbol, by comparing the signal to noise ratio of first segment signal and second segment signal, according to the reference synchronization position that the bisection recursive fashion is searched described OFDM symbol, obtain the synchronous original position of OFDM symbol valid data part according to the reference synchronization position.The embodiment of the present application just can start synchronously after receiving CP to be estimated, by the signal to noise ratio of block signal relatively, and draws the synchronous original position of OFDM valid data symbol by recursion method, calculating simply, synchronizing speed is fast; And compared with prior art,, reduced the redundancy of system, and can finish synchronously within a short period of time owing to need therefore can not influence the transmission rate of valid data part in the valid data partial stack training sequence and the pilot tone of transmission.

The technology that those skilled in the art can be well understood in the embodiment of the invention can realize by the mode that software adds essential general hardware platform.Based on such understanding, the part that technical scheme in the embodiment of the invention contributes to prior art in essence in other words can embody with the form of software product, this computer software product can be stored in the storage medium, as ROM/RAM, magnetic disc, CD etc., comprise that some instructions are with so that a computer equipment (can be a personal computer, server, the perhaps network equipment etc.) carry out the described method of some part of each embodiment of the present invention or embodiment.

Each embodiment in this specification all adopts the mode of going forward one by one to describe, and identical similar part is mutually referring to getting final product between each embodiment, and each embodiment stresses all is difference with other embodiment.Especially, for system embodiment, because it is substantially similar in appearance to method embodiment, so description is fairly simple, relevant part gets final product referring to the part explanation of method embodiment.

Above-described embodiment of the present invention does not constitute the qualification to protection range of the present invention.Any modification of being done within the spirit and principles in the present invention, be equal to and replace and improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1. an OFDM sync bit method of estimation is characterized in that, comprising:

Receive the cyclic prefix CP of OFDM symbol, described CP comprises training sequence and the data symbol with equal transmit power;

To treat that block signal is divided into two segment signals, and be respectively first segment signal and second segment signal, the described block signal for the treatment of belongs to described CP;

Respectively described first segment signal is separated with data symbol with training sequence in second segment signal;

Calculate the signal to noise ratio of described first segment signal and second segment signal according to training sequence separated and data symbol;

By the signal to noise ratio of more described first segment signal and second segment signal, search the reference synchronization position of described OFDM symbol according to the bisection recursive fashion;

Obtain the synchronous original position of described OFDM symbol valid data part according to described reference synchronization position.

2. method according to claim 1 is characterized in that, the described signal to noise ratio of calculating described first segment signal and second segment signal according to training sequence separated and data symbol comprises:

Calculate the training sequence in described first segment signal and second segment signal and the auto-correlation function of data symbol respectively;

Respectively the estimation of the auto-correlation function of data symbol in first segment signal and second segment signal is estimated as signal power, and the estimation of training sequence is estimated as noise power;

The ratio that the signal power estimation and the noise power of described first segment signal and second segment signal are estimated is as the signal to noise ratio of described first segment signal and second segment signal respectively.

3. method according to claim 1 is characterized in that, described reference synchronization position of searching described OFDM symbol according to the bisection recursive fashion comprises:

When the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is in preset range, export the reference synchronization position of the position at first sampling point place behind described second segment signal as described OFDM symbol;

When the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is not in preset range, if the signal to noise ratio of described first segment signal is less than the signal to noise ratio of described second segment signal, extract described second segment signal as the described block signal for the treatment of, return the described block signal of will treating and be divided into the step of two segment signals;

When the difference of the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal is not in preset range, if the signal to noise ratio of described first segment signal is greater than the signal to noise ratio of described second segment signal, extract described first segment signal as the described block signal for the treatment of, return the described block signal of will treating and be divided into the step of two segment signals.

4. method according to claim 1 is characterized in that, the described synchronous original position that obtains described OFDM symbol valid data part according to described reference synchronization position comprises:

With the position at first sampling point place of described CP as the reference point, judge described reference synchronization position to the distance between the described reference point whether less than half of described CP length;

If described distance is less than half of described CP length, then described reference synchronization position is added position after the above CP length as the synchronous original position of described OFDM symbol valid data part, if described distance is greater than half of described CP length, then with the synchronous original position of described reference synchronization position as described OFDM symbol valid data part.

5. method according to claim 1 is characterized in that, described will treat that block signal is divided into two segment signals before, also comprise:

Judge that whether the described number of samples of block signal for the treatment of is greater than 1;

If described number of samples greater than 1, is then carried out the described block signal for the treatment of is divided into two segment signals,, then export the reference synchronization position of the position at described sampling point place as described OFDM symbol if described number of samples equals 1.

6. an OFDM sync bit estimation unit is characterized in that, comprising:

Receiving element is used to receive the cyclic prefix CP of OFDM symbol, and described CP comprises training sequence and the data symbol with equal transmit power;

Segmenting unit is used for being respectively first segment signal and second segment signal with treating that block signal is divided into two segment signals, and the described block signal for the treatment of belongs to described CP;

Separative element is used for respectively the training sequence of described first segment signal and second segment signal is separated with data symbol;

Computing unit is used for calculating according to training sequence separated and data symbol the signal to noise ratio of described first segment signal and second segment signal;

Search the unit, be used for signal to noise ratio, search the reference synchronization position of described OFDM symbol according to the bisection recursive fashion by more described first segment signal and second segment signal;

Obtain the unit, be used for obtaining the synchronous original position of described OFDM symbol valid data part according to described reference synchronization position.

7. device according to claim 6 is characterized in that, described computing unit comprises:

The auto-correlation function computing unit is used for calculating respectively the training sequence of described first segment signal and second segment signal and the auto-correlation function of data symbol;

Power estimation unit is used for respectively the estimation of the auto-correlation function of first segment signal and the second segment signal data symbol is estimated as signal power, and the estimation of training sequence is estimated as noise power;

The signal to noise ratio acquiring unit, be used for respectively the signal power of described first segment signal and second segment signal estimated and the ratio of noise power estimation as the signal to noise ratio of described first segment signal and second segment signal.

8. device according to claim 6 is characterized in that, the described unit of searching comprises:

First comparing unit, whether the difference of signal to noise ratio that is used for the signal to noise ratio of comparison first segment signal and described second segment signal is in preset range;

First performance element, be used for difference when the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal in preset range the time, export the reference synchronization position of the position at first sampling point place behind described second segment signal as described OFDM symbol;

Second comparing unit is used for difference when the signal to noise ratio of the signal to noise ratio of described first segment signal and described second segment signal not in preset range the time, the signal to noise ratio of the signal to noise ratio of more described first segment signal and described second segment signal;

Second performance element, be used for when the signal to noise ratio of described first segment signal during less than the signal to noise ratio of described second segment signal, extract described second segment signal as the described block signal for the treatment of, and return described segmenting unit and carry out function corresponding, when the signal to noise ratio of described first segment signal during greater than the signal to noise ratio of described second segment signal, extract described first segment signal as the described block signal for the treatment of, return described segmenting unit and carry out function corresponding.

9. device according to claim 6 is characterized in that, described acquisition unit comprises:

Apart from judging unit, be used for position with first sampling point place of described CP as the reference point, judge described reference synchronization position to the distance between the described reference point whether less than half of described CP length;

The sync bit determining unit, if be used for described distance less than half of described CP length, then described reference synchronization position is added position after the above CP length as the synchronous original position of described OFDM symbol valid data part, if described distance is greater than half of described CP length, then with the synchronous original position of described reference synchronization position as described OFDM symbol valid data part.

10. device according to claim 6 is characterized in that, also comprises:

Judging unit is used to judge that whether the described number of samples of block signal for the treatment of is greater than 1;

Performance element if be used for described number of samples greater than 1, then trigger described segmenting unit and carries out function corresponding, if described number of samples equals 1, then exports the reference synchronization position of the position at described sampling point place as described OFDM symbol.

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