CN101310501A - Timing acquisition and mode and guard detection for an OFDM transmission - Google Patents

Abstract

Techniques for detecting mode and guard length and estimating timing offset for an OFDM transmission are described. Multiple hypotheses for different combinations of mode and guard length that might have been used for the OFDM transmission are evaluated. For each hypothesis, correlation is performed on received samples for a hypothesized guard interval to obtain correlation results. The energy of the hypothesized guard interval is determined. A first metric is derived based on the correlation results and the energy. The first metric may be filtered, e.g., averaged. Noise is estimated, e.g., based on a set of elements for the filtered first metric at locations determined by an estimated timing offset for the hypothesis. A second metric is derived based on the filtered first metric and the estimated noise. The second metric for all hypotheses may be used to determine the mode, guard length, and timing offset for the OFDM transmission.

Description

The timing that is used for the OFDM transmission is obtained and pattern and protection detection

The related application cross reference

What the present invention advocated to have precedence over application on September 20th, 2005 is entitled as " quick mode, protection and first arrive the path and obtain among the OFDM " (FAST MODE; GUARD AND FIRST ARRIVING PATHACQUISITION IN OFDM) United States Patent (USP) provisional application case the 60/718th; No. 988, it is assigned and is incorporated herein in the assignee of this paper and with way of reference.

Technical field

The present invention relates generally to communication, and more particularly relate to the technology of obtaining that is used for communication system.

Background technology

Orthogonal frequency multiplex (MUX) (OFDM) is the multi-carrier modulation technology that the superperformance of some wireless environment can be provided.Orthogonal subbands that OFDM can be divided into the whole system bandwidth a plurality of (K), described orthogonal subbands is also referred to as carrier wave, subcarrier, guiding or the like usually.For OFDM, each sub-band all is associated with the corresponding carriers that can use data to modulate.

In ofdm system, transmitter processes (for example, coding, staggered and modulation) business datum is to produce modulation symbol and further described modulation symbol to be mapped to described K sub-frequency bands.Then, transmitter transforms to described modulation symbol time domain and produces the OFDM symbol.Each OFDM symbol contains useful part and protection interval, and described protection is the repeating part of described useful part at interval.Ofdm system can be supported the different mode of different K values and the difference protection length of different protection interval duration.Then, transmitter will be according to producing the OFDM symbol through selection for pattern of using and protection length.Transmitter arrives receiver with described OFDM symbol transmission.

Receiver is to implementing complementary the processing from the OFDM symbol that described transmitter received.Receiver at first detects usually by employed pattern of described transmitter and protection length.Then, receiver is handled the OFDM symbol that each receives according to pattern that is detected and protection length.Can need also to detect reliably rapidly described pattern and protection length so that set about the processing of the OFDM symbol that receives as quickly as possible.

Therefore, need be in this technology in order to the technology of pattern in the detection ofdm system and protection length.

Summary of the invention

This paper sets forth and to be used for rapidly and the technology of the timing slip of the OFDM transmission that received of detecting pattern and protection length and estimating reliably.Described pattern is indicated the duration of the useful part of each OFDM symbol.The protection duration at interval of each OFDM symbol of protection Length Indication.Timing slip indicates each to receive the initial of OFDM symbol.

In one aspect, derive through improvement tolerance and it is used for mode detection, protection detection and/or timing slip and estimate.As used herein, tolerance is the function of one or more known parameters and the quantitative estimation that is used for one or more unknown parameters.In one embodiment, obtain the sample of the OFDM that receives of institute transmission, and the sample enforcement at suppose protection interval is correlated with (correlation) with acquisition correlated results (correlation result).Also definite energy of supposing the protection interval.Derive first/initial tolerance based on described correlated results and described energy.Described first tolerance can (for example) be passed through average and filtered.Based on (for example) one group of key element estimating noise by described first tolerance of the determined position of estimated timing slip.Then, based on derive second through filtering first tolerance and estimated noise/through improvement tolerance.Described second tolerance can be used for detecting the pattern of described OFDM transmission and protects length and estimate the timing slip that described OFDM transmits.Can as mentioned belowly calculate described relevant, the energy and first tolerance effectively.

In another aspect, can be effectively at reception OFDM transmission Implementation Modes and protection detection and timing slip estimation.Derive at least one tolerance (it can be described first and/or second tolerance) based on described sample and at a plurality of supposition.Each supposition is corresponding to the particular combinations of pattern of being supposed at described OFDM transmission and protection length.Then, detect the pattern and the protection length of described OFDM transmission, for example institute's detecting pattern and protection length by discerning most probable supposition based on described tolerance and the pattern and the protection length of described supposition being provided as described OFDM transmission based on described tolerance.Also can estimate the timing slip of described OFDM transmission based on described tolerance.Then, handle described sample according to institute's detecting pattern and protection length and estimated timing slip.

In aspect another, detect first and arrive path (FAP) and place the fast Fourier transform (FFT) window to realize superperformance in a certain mode.Can detect the pattern of described OFDM transmission and protect the same metric of length to detect described FAP based on being used to.In one embodiment, based on the gain calculating threshold value of measuring and indicating the target location of described FFT window.Then, based on described tolerance and the described FAP of described threshold test.Determine FFT based on described FAP, pattern and the protection length of detecting.Described FFT window has by the determined width of institute's detecting pattern and is placed on by detection FAP and the determined position of protection length.Sample is at selecting based on the treatment of selected of FFT window.

Hereinafter will set forth various aspects of the present invention and embodiment in more detail.

Description of drawings

In conjunction with each diagram reading detailed description hereinafter described, people will easilier understand feature of the present invention and character, and identical reference character identifies accordingly in all diagrams.

Fig. 1 shows the calcspar of transmitter and receiver.

Fig. 2 shows the calcspar of the OFDM modulator at transmitter place.

Fig. 3 shows the calcspar of the ofdm demodulator at receiver place.

Fig. 4 shows the segmentation calculating of the correlation of four protection length.

Fig. 5 A and 5B show that the FAP of single path and multi-path channel detects.

Fig. 6 Displaying timer obtains and the calcspar of pattern, protection and FAP detecting unit.

Fig. 7 shows the protection calcspar of correlator, protection energy calculation unit and metric calculation unit at interval.

Fig. 8 shows the process that is used for the tolerance of pattern and protection detection in order to derivation.

Fig. 9 shows in order to by selecting the process that derives tolerance.

Figure 10 shows in order to the process with the segmented mode calculating parameter.

Figure 11 shows the process in order to detecting pattern and protection length.

Figure 12 shows the process in order to the timing slip of detecting pattern and protection length and estimating OFDM transmission.

Figure 13 shows the process that is used for FAP detection and the placement of FFT window.

Embodiment

" exemplary " used herein speech meaning " as example, example or illustration ".In this article, the embodiment of any being called " exemplary " or design all may not be considered as than other embodiment or be designed to preferred or favourable.

The technology of obtaining described herein can be used for various communication systems, for example ofdm system, OFDM (OFDMA) system, single-carrier frequency division multiple access (SC-FDMA) system or the like.The OFDMA system utilizes OFDM.In general, by OFDM in frequency domain and in time domain, send modulation symbol by SC-FDMA.

For the purpose of clear, hereinafter particularly at two exemplary of the integrated service digital broadcasting (ISDB-T) of implementing handheld digital video broadcasting (DVB-H) and land television broadcasting based on the described technology of obtaining of systematically discussing of OFDM.DVB-H and ISDB-T support the Digital Transmission of multimedia on terrestrial communications network.What DVB-H was set forth in January calendar year 2001 in November, 2004 is entitled as " digital video broadcasting (DVB), framing structure, chnnel coding and the modulation of digital land TV " (Digital Video Broadcasting (DVB); Framing Structure, Channel Codingand Modulation for Digital Terrestrial Television) among the document ETSI EN 300 744.ISDB-T is set forth among the document ARIB STD-B31 that is entitled as " transmission system of Digital Terrestrial Television Broadcasting " (Transmission System forDigital Terrestrial Television Broadcasting) in July, 2003.Described file can openly obtain.

Fig. 1 shows the calcspar based on transmitter in the ofdm system 100 110 and receiver 150, and described system can implement DVB-H, ISDB-T and or some other design.At transmitter 110 places, emission (TX) data processor 120 is handled (for example format, encode, interlock and sign map) business datum and is produced data symbol.As used herein, data symbol is the modulation symbol of business datum, and frequency pilot sign is the modulation symbol (it is both data of a priori knowing of transmitter and receiver) of pilot tone, and nil symbol is a signal value of zero.OFDM modulator 130 receives data symbols and frequency pilot sign and it is multiplexed on the correct sub-band, and enforcements OFDM as mentioned below modulates, and an OFDM symbol is provided in each OFDM symbol period.OFDM symbol period (or being called symbol period simply) is the duration of an OFDM symbol.Transmitter unit (TMTR) 132 receives and handles (for example, being converted to analog signal, amplification, filtering and up-conversion) described OFDM symbol and produces through modulation signal, describedly transmits via antenna 134 through modulation signal.

At receiver 150 places, antenna 152 receives from transmitter 110 and describedly is provided to receiver unit (RCVR) 154 through modulation signal and with received signal.Receiver unit 154 is regulated (for example filtering, amplification, down-conversion and digitlization) received signal and sample is provided.Ofdm demodulator 160 (Demod) detects the pattern and the protection length of described OFDM transmission and estimates that further timing slip is correctly to be positioned over the FFT window in each OFDM symbol period.The ofdm demodulator 160 described samples of further processing as mentioned below also provide data symbol to estimate, described data symbol estimates it is the estimation of the data symbol that sent by transmitter 110.Receiving (RX) data processor 170 handles (for example symbol de-maps, release of an interleave, and decoding) described data symbol and estimates and provide through decoded data.In general, the processing complementation carried out with the OFDM modulator 130 and the TX data processor 120 at transmitter 110 places respectively of the processing carried out of ofdm demodulator 160 and RX data processor 170.

Controller/ processor 140 and 180 controls transmitter 110 and the operation of the each processing unit at receiver 150 places respectively.The data and the procedure code of memory 142 and 182 difference stored transmit machines 110 and receiver 150.

The calcspar of the OFDM modulator 130 at transmitter 110 places in Fig. 2 displayed map 1.In OFDM modulator 130, symbol receives data symbols and frequency pilot sign and it is mapped to K usable subband to sub-band map unit 210, nil symbol is mapped to N-K does not use sub-band, and provide N transmission symbol to total N sub-frequency bands.Each transmission symbol can be data symbol, frequency pilot sign or nil symbol.In each OFDM symbol period, unit 212 by contrary fast fourier transform (IFFT) of N point or contrary discrete Fourier transform (DFT) (IDFT) a described N transmission symbol is transformed to time domain and provide contain N time domain chip through figure shift.Each chip is the complex values that plan is transmitted in a chip period.Parallel-to-serial (P/S) transducer 214 is with each described N chip serialization through figure shift.Then, protection is inserted unit 216 at interval and is repeated each part through figure shift (or L chip) contains N+L chip with formation OFDM symbol.Each OFDM symbol contains N chip as available part and L chip as protection at interval.Intersymbol interference (ISI) and the inter-carrier interference that is caused expanded in the delay that described protection is used to keep out by communication channel at interval.DVB-H supports three kinds of FFT operator schemes of 2K, 4K and 8K size.ISDB-T also supports 256,512 and three kinds of FFT operator schemes of 1K size.DVB-H and ISDB-T also support the different protection length of four kinds of 1/4,1/8,1/16 and 1/32 OFDM symbol.Table 1 has provided some key parameter value of three kinds of patterns of DVB-H and ISDB-T.

In table 1, row 3 and 4 has provided the FFT size (with sample data) of three kinds of patterns of DVB-H and ISDB-T and the quantity of usable subband/carrier wave respectively.Row 5 to 8 has provided protection duration (with the quantity of sample) at interval of 1/4,1/8,1/16 and 1/32 protection length of three kinds of patterns of DVB-H and ISDB-T.In following explanation, m is that the index of pattern and g are the index of protection length, wherein m ∈ 1,2,3} and g ∈ 1,2,3,4}.More particularly, g=1 representative protection length is 1/4, and g=2 representative protection length is 1/8, and g=3 representative protection length is 1/16, and g=4 representative protection length is 1/32.As shown in table 1, the duration of useful part (or FFT size) is expressed as N _mAnd it only depends on mode m.The protection duration at interval is expressed as L _{M, g}And its depend on mode m and protection length g both.The OFDM symbol duration T of mode m and protection length g _{M, g}The FFT size that equals mode m adds the protection interval duration L of protection length g _{M, g}, or T _{M, g}=N _m+ L _{M, g}For instance, the OFDM symbol size of pattern 2 and protection length 1/16 is T in DVB-H _2,3=4096+256=4352.

The row 7 of table 1 have provided the OFDM symbol size T of pattern 1 and the different protection length of DVB-H _{1, g}(with sample size).Row 11 has provided the OFDM symbol size T of pattern 1 and the different protection length of ISDB-T _{1, g}

Table 1

The calcspar of an embodiment of the ofdm demodulator 160 at receiver 150 places in Fig. 3 displayed map 1.In ofdm demodulator 160, regularly obtain and pattern, protection and FAP detecting unit 310 based on from the institute's sample that the receives estimation timing slip and the detecting pattern of receiver unit 154 and protect length.Unit 310 also produces the FFT window, and described FFT window determines which sample will receive the OFDM symbol at each handles.

Preprocessor 320 handle the sample that receives and the input sample is provided.Preprocessor 320 can be implemented automatic gain control (AGC), regularly obtains, filtering, sample rate conversion, direct current (DC) remove, frequency errors estimation and removing and/or other function.Unit 322 removes N the incoming symbol that each receives the protection interval in the OFDM symbol and described OFDM symbol is provided based on described FFT window.This receives the OFDM symbol to each, and the 324 couples of described N in FFT unit incoming symbols are implemented N point FFT and N frequency domain institute receiving symbol is provided.Channel estimator 328 is derived channel estimating based on the reception frequency pilot sign.Described channel estimating can be that time domain channel impulse response estimation and/or frequency domain channel frequency response are estimated.Data demodulator 326 by described channel estimating to received data symbol implementation data demodulation/detect and provide data symbol to estimate.Though be not shown in for simplicity's sake among Fig. 3, ofdm demodulator 160 can comprise other processor unit that is used for frame detection, frame synchronizationization, time tracking, frequency-tracking and/or other function.

The received signal at receiver place can be expressed as:

R (k)=s (k-τ) e ^{J2 π ε k/N}+ w (k), equation (1)

Wherein s (k) is institute's transmit chip of the k of sample cycle,

R (k) is the sample that receives of the k of sample cycle,

τ is the timing slip of received signal,

ε is the frequency errors of received signal, and

W (k) is the noise of being observed by sample r (k).

For simplicity's sake, the sampling rate of following explanation hypothesis r (k) equals the spreading rate of s (k).This paper does not set forth in order to estimate that also the frequency of emending frequency mistake is obtained.

As shown in equation (1), received signal is the delayed version of institute's transmission signals.Institute's transmission signals is made up of a series of OFDM symbols.Each OFDM symbol is made up of T=N+L sample, and wherein N and L are by described OFDM transmission and described system (for example, DVB-H or ISDB-T) employed pattern and protect length to be determined.Described receiver can not known described system, described pattern and described protection length (for example, when just being powered on) and needs is checked and verify described parameter correctly to handle the signal that is received.

In general, receiver can be assessed the pattern and the protection supposition of arbitrary quantity.Each pattern and protection supposition have been used for the AD HOC and the specific protection length of received signal corresponding to supposition.Therefore, suppose that (m is g) corresponding to the supposition of using mode m and protection length g.For search fully, can be at all 12 kinds of supposition of DVB-H or 3 kinds of patterns of ISDB-T assessment and 4 kinds of protection length.For the part search, can assess a son group of described supposition.For concrete search, only assess a supposition (for example, at last pattern of obtaining and protection length).

As shown in Figure 2, each OFDM symbol contains useful part and protection interval.Because described useful part is showed the characteristic of complicated Gaussian process due to the N point IFFT of a large amount of independent data symbols at random.After inserting protection at interval, described OFDM symbol is not white process (white process) and shows the cyclic stationary statistical property that described characteristic can be through developing with detecting pattern and protecting length and estimate timing slip τ.In particular, the repeating part of OFDM symbol can be relevant with the initial protion at a distance of N sample.Can derive various tolerance and it is used for determining pattern, protection length and the timing slip of received signal based on correlated results.

Can be following the institute's sample that receives enforcement of mode m and protection length g be correlated with:

c _m(k)=r (k) r ^*(k-N _m), and equation (2)

$C_{m,g}\left(k\right)=\underset{i=0}{\overset{L_{m,g}-1}{\mathrm{\Σ}}}{c}_m(k-i),$ Equation (3)

C wherein _m(k) be r (k) and r ^*(k-N _m) product.

' * ' represents complex conjugate, and

C _{M, g}(k) be the correlated results of the k of sample cycle internal schema m and protection length g.

Can following computation schema m and the protection energy at interval of protection length g:

e _m(k)=| r (k) | ²+ | r (k-N _m) | ², and equation (4)

$E_{m,g}\left(k\right)=\underset{i=0}{\overset{L_g-1}{\mathrm{\Σ}}}{e}_m(k-i),$ Equation (5)

E wherein _m(k) be sample r (k) and r (k-N _m) energy, and

E _{M, g}(k) be the protection energy of mode m and protection length g among the k of sample cycle.

Arrive as shown in (5) C as equation (2) _{M, g}(k) and E _{M, g}(k) all depend on mode m and protection length g both.Mode m determines which sample will be used for calculating.Protection length g determines to add up to obtain C _{M, g}(k) and E _{M, g}(k) sample size.(m g), can obtain C in each k of sample cycle for each supposition _{M, g}(k) new value and can obtain E _{M, g}(k) new value.

Can followingly calculate C with recursive fashion _{M, g}(k) and E _{M, g}(k):

C _{M, g}(k)=C _{M, g}(k-1)+c _m(k)-c _m(k-L _{M, g}), and equation (6)

E _{M, g}(k)=E _{M, g}(k-1)+e _m(k)-e _m(k-L _{M, g}), equation (7)

As shown in equation (6), can be by adding the new c that calculates for the current k of sample cycle _m(k) and from L early _{M, g}Deduct old c in the individual sample cycle _m(k-L _{M, g}) calculate the C of each sample cycle _{M, g}(k).Can with C _{M, g}(k) similarly mode is calculated E _{M, g}(k).

In one embodiment, as shown in equation (3) and (5), by at L _{M, g}On the c that adds up respectively _m(k) and e _m(k) value is calculated C _{M, g}(k) and E _{M, g}(k).For each supposition (m, g), the c that will add up _m(k) and e _m(k) quantity L _{M, g}Depend on mode m and protection length g.

Being called another embodiment that protects the method for selecting, calculate C based on a fraction of usable samples _{M, g}(k) and E _{M, g}(k).For this embodiment, can be less than L by adding up respectively _{M, g}The c of value _m(k) and e _m(k) calculate C _{M, g}(k) and E _{M, g}(k).Can be with the used c that adds up _m(k) and e _m(k) value spreads over and wholely supposes in the protection at interval.For instance, can be by each c that adds up _m(k) value or c _m(k) to c _m(k-L _{M, 4}-1) C of the shortest protection length 1/32 of calculating _{M, 4}(k).Can be by adding up every a c _m(k) value or c _m(k), c _m(k-2) ..., c _m(k-L _{M, 3}-2) calculate the C that protects length 1/16 _{M, 3}(k).Can be by adding up every four c _m(k) value or c _m(k), c _m(k-4) ..., c _m(k-L _{M, 2}-4) calculate the C that protects length 1/8 _{M, 2}(k).Can be by adding up every eight c _m(k) value or c _m(k), c _m(k-8) ..., c _m(k-L _{M, 1}-8) calculate the C that protects length 1/4 _{M, 1}(k).Also can with C _{M, g}(k) similarly mode is calculated E by selecting method _{M, g}(k).C _{M, g}(k) and E _{M, g}(k) select the detection performance that calculation requirement that calculating can reduce receiver provides all protection length simultaneously with comparativity.The C of DVB-H _{M, g}(k) and E _{M, g}(k) can be through selecting C with coupling ISDB-T _{M, g}(k) and E _{M, g}(k).

As shown in table 1, the FFT of pattern 1 size and protection length are the FFT size of pattern 1 among the ISDB-T and 8 times of protection length in DVB-H.Therefore, for the detection performance that can compare with ISDB-T, can select C to DVB-T by the factor that is 8 to the maximum _{M, g}(k) and E _{M, g}(k).In general, any factor of selecting can be used for C _{M, g}(k) and E _{M, g}(k) in the calculating.

In the embodiment that is called segmentation calculating, can calculate the C of different protection length with segmented mode at set pattern _{M, g}(k) and E _{M, g}(k) to reduce amount of calculation.To as shown in (5), determine to calculate C as equation (2) by mode m _{M, g}(k) and E _{M, g}(k) used sample is further determined the counting period by protection length g simultaneously.Therefore, can calculate the C of the shortest protection length 1/32 _{M, g}(k) and E _{M, g}And the result of this protection length can be used to calculate the C of longer protection length 1/16,1/8 and 1/4 (k), _{M, g}(k) and E _{M, g}(k).

For instance, can two C that protect length g1 and g2 of following calculating _{M, g}(k), L wherein _G1=2L _G2:

$C_{m,g1}\left(k\right)=\underset{i=0}{\overset{L_{g1}-1}{\mathrm{\Σ}}}{c}_m(k-i)$

$=\underset{i=0}{\overset{{\mathrm{<figure-callout\; id="1"\; label="L\; g"\; filenames="A20068004255900281.png,A20068004255900311.png"\; state="\{\{state\}\}">L</figure-callout>}}_g/2-1}{\mathrm{\&Sigma;}}}{c}_m(k-i)+\underset{i={\mathrm{<figure-callout\; id="1"\; label="L\; g"\; filenames="A20068004255900281.png,A20068004255900311.png"\; state="\{\{state\}\}">L</figure-callout>}}_g/2}{\overset{L_{g1}-1}{\mathrm{\&Sigma;}}}{c}_m(k-i)$ Equation (8)

$=\underset{i=0}{\overset{L_{g2}-1}{\mathrm{\&Sigma;}}}{c}_m(k-i)+\underset{i={\mathrm{<figure-callout\; id="2"\; label="L\; g"\; filenames="A20068004255900281.png,A20068004255900301.png"\; state="\{\{state\}\}">L</figure-callout>}}_g}{\overset{2L_{g2}-1}{\mathrm{\&Sigma;}}}{c}_m(k-i)$

${=C}_{m,g2}\left(k\right)+C_{m,g2}(k-L_{g2}).$

As shown in equation (8), can be based on the short C that protects length of the k of sample cycle _{M, g2}(k) L early _G2The C of individual sample cycle _{M, g2}(k-L _G2) the long C that protects length of calculating _{M, g1}(k).

Fig. 4 shows the C based on the shortest protection length 1/32 _{M, 4}(k) C at four protection length of mode m is calculated in segmentation _{M, g}(k) embodiment.For this embodiment, as shown in equation (6), based on c _m(k) calculate the C of each k of sample cycle _{M, 4}(k).Then, based on the C of new calculating _{M, 4}(k) and stored C _{M, 4}(k-L _{M, 4}) calculating C _{M, 3}(k).Similarly, based on the C of new calculating _{M, 3}(k) reach the C that has stored _{M, 3}(k-L _{M, 3}) calculating C _{M, 2}(k).At last, based on the C of new calculating _{M, 2}(k) reach the C that has stored _{M, 2}(k-L _{M, 2}) calculating C _{M, 1}(k).For this embodiment, receiver can be stored C _{M, 4}(k) last L _{M, 4}Individual element, C _{M, 3}(k) last L _{M, 3}Individual element, and C _{M, 2}(k) last L _{M, 2}Individual element.

Can the memory effective means implement segmentation calculating.Can be by only storing C _{M, 4}Last L _{M, 1}All four protection supposition of the parallel assessment of individual value (just, the quantity of minimum protection correlation equals the length of maximum protection size).Fig. 4 indication can hierarchical approaches from C _{M, 4}Derive C _{M, 1}, C _{M, 2}And C _{M, 3}In each the institute important.Owing to only implement summation to move down described classification, so can be only with C _{M, 4}Value is stored in the memory and with each step and only stores C _{M, 4}Value.From C _{M, 4}Initial and move to the described classification ladder in lower edge, can obtain each next C by each summation level _{M, x}Value.

Also otherwise C is calculated in segmentation _{M, g}(k).Can with C _{M, g}(k) similarly E is calculated in the mode segmentation _{M, g}(k).

Can be based on C _{M, g}(k) and/or E _{M, g}(k) define various tolerance.In one embodiment, as the tolerance of giving a definition:

M _{M, g}(k ')=| C _{M, g}(k) |-ρ E _{M, g}(k), equation (9)

Wherein ρ is a proportionality factor.

K '=k mod T _{M, g}Be the index of described tolerance, and

M _{M, g}(k ') is the tolerance element that index k ' locates mode m and protection length g.

Because received signal is made up of a series of OFDM symbols, so expection tolerance M _{M, g}(k ') will repeat in each OFDM symbol period.Thereby, can be at T _{M, g}The M of inferior assumed calculation mode m and protection length g _{M, g}(k '), index k '=0 wherein ..., T _Mg-1.Described T _{M, g}Inferior supposition is corresponding to the T of the section start of reception OFDM symbol _{M, g}Individual possible position.

In one embodiment, can be as the proportionality factor ρ that gives a definition.

$\mathrm{\&rho;}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ Equation (10)

Wherein SNR is the signal to noise ratio of received signal.In other embodiments, can ρ being set to can be through selecting so that the fixing or configurable value of superperformance to be provided.For instance, can ρ be set to 0,1/4,1/2,1 or some other value.Can ρ be set to corresponding to described receiver expect the value of operation SNR.

Since due to the fading channel, correlated results C _{M, g}(k) can be along with the time changes.In equation (9), from described correlated results, deduct the protection ENERGY E _{M, g}(k) to take into account the influence of fading channel.

Can derive tolerance M based on the sample of an OFDM symbol period _{M, g}(k ').For the purpose of the detection performance of improvement, can be at a plurality of OFDM symbol period upward filtration waviness amount M _{M, g}(k ').In one embodiment, can implement filtering by following averaging:

${\tilde{M}}_{m,g}(k^{\&prime;},l)=\underset{i=0}{\overset{N_c-1}{\mathrm{\&Sigma;}}}{M}_{m,g}(k^{\&prime;},l-i),$ Equation (11)

M wherein _{M, g}The tolerance in (k ', 1) is-symbol cycle 1,

Measuring of is-symbol cycle 1 through filtering, and

N _cBe in order to average to obtain

The quantity of symbol period.

For all patterns and protection length, N _cIt can be fixed value.For instance, can be with N _cBe set to 1,2,4,8,16 or the like.Perhaps, N _cIt can be the configurable value that depends on mode m, protection length g, channel and noise conditions or the like.For instance, can be with the N of higher value _cBe used for short protection at interval, and with the N of smaller value _cBe used for long protection at interval.

In another embodiment, can followingly implement described filtering by infinite impulse response (IIR) filter:

${\tilde{M}}_{m,g}(k^{\&prime;},l)=\mathrm{\&alpha;}\&CenterDot;{\tilde{M}}_{m,g}(k^{\&prime;},l-1)+(1-\mathrm{\&alpha;})\&CenterDot;M_{m,g}(k^{\&prime;},l),$ Equation (12)

Wherein α is a coefficient of determining average magnitude.In general, 0＜α＜1, wherein big α is corresponding to average and vice versa.For the purpose of clear, in following explanation, omit notation index 1, and

Measuring of expression current sign cycle through filtering.

In one embodiment, at each pattern and protection supposition, storage tolerance T _{M, g}Individual element, wherein k '=0 ..., T _{M, g}-1.For this embodiment, can be at the element of different mode and protection supposition storing different numbers.

In being called another embodiment of dacimation-in-time method, at supposition (m, g) only storage tolerance

Described T _{M, g}Sub-fraction in the individual element.By only storing described T _{M, g}The child group of individual element reduces the quantity of possible timing slip (or time supposition).The dacimation-in-time method can be used for having the pattern (for example, pattern 2 and 3) of big FFT size.Can stride the element that whole OFDM symbol selection will be stored.

In one embodiment, but all T of memory module 1 _{1, g}Individual element is with the T every the mode memory module 2 of a timing slip _{2, g}/ 2 elements, and with the T every the mode memory module 3 of four timing slips _{3, g}/ 4 elements.For this embodiment, can be at the set element that comprises length g for all three pattern storage equal numbers.For DVB-H, receiver can be each storage in described three patterns at protection length 1/4 2568 elements, at 2304 elements of protection length 1/8 storage, at 2192 elements of protection length 1/16 storage, and at 2112 elements of protection length 1/32 storage, as shown in table 1.

The dacimation-in-time method has reduced

Calculating and memory requirement, provide the temporal resolution with comparativity (with respect to the OFDM symbol size) for all patterns simultaneously.The dacimation-in-time method can be used for the temporal resolution of DVB-H with coupling ISDB-T.

As shown in table 1, the FFT size of pattern 1 is 8 times of FFT size of pattern 1 among the ISDB-T in DVB-H.In one embodiment, in DVB-H, can the dacimation-in-time method be used for each of described three patterns with factor 8.For this embodiment, both patterns of DVB-H and ISDB-T 1 have identical temporal resolution, and the pattern 2 of two systems has the temporal resolution for the twice of pattern 1, and the mode 3 of two systems has four times temporal resolution for pattern 1.In another embodiment, the dacimation-in-time method is used for DVB-H and ISDB-T so that all patterns of described two systems all have the identical temporal resolution with respect to the OFDM symbol size.For this embodiment, in ISDB-T, with factor 2 and 4 the dacimation-in-time method is used for pattern 2 and 3 discriminably, and in DVB-H, with factor 8,16 and 32 the dacimation-in-time method is used for pattern 1,2 and 3 discriminably.In general, arbitrary dacimation-in-time amount can be used for arbitrary pattern and system.

The tolerance of each pattern and protection supposition

Element can be by vector

Expression.Each vector

In the quantity of element depend on mode m, protection length g and whether select method service time.

In one embodiment, tolerance

Be used for detecting pattern and protection length and estimate timing slip.For this embodiment, can followingly determine described pattern, protection length and timing slip:

$(\hat{m},\hat{g},\widehat{\mathrm{\&tau;}})=\arg \left(\underset{m,g,k^{\&prime;}}{\max }\right\{{\tilde{M}}_{m,g}\left(k^{\&prime;}\right)\left\}\right),$ Equation (13)

Wherein

Be the pattern that is detected,

Be the protection length that is detected, and

It is estimated timing slip.In the equation (13), discern all patterns and protection length Greatest member.Will

Index m, g and the k ' of this greatest member be provided as the pattern that is detected respectively The protection length that is detected

And estimated timing slip

As mentioned below, described estimated timing slip is indicated the section start of the OFDM symbol that receives.

Tolerance

The good estimation of timing slip τ can be provided.Yet, in some operational scenarios vacuum metrics

Can supply a pattern and protect the unreliable detection of length.For instance, pattern 2 and 3 the shortest protection length 1/32 and be lower than in the sight of SNR of 5dB tolerance in fading channel Often be claimed as pattern 1.This be because since by the sample of minimum number (for ISDB-T only 8 samples and for DVB-H 64 samples) on add up and produce C _{M, g}(k) and E _{M, g}(k) cause pattern 1 to have the statistics of noise maximum in all three patterns.

In another embodiment, with a plurality of step deterministic models, protection length and timing slip.For this embodiment, tolerance

Be the initial tolerance that is used to estimate timing slip.At first following each pattern of identification and protection supposition

Greatest member.

${\mathrm{\&tau;}}_{m,g}=\arg \left(\underset{k^{\&prime;}}{\max }\right\{{\tilde{M}}_{m,g}\left(k^{\&prime;}\right)\left\}\right),$ Equation (14)

τ wherein _{M, g}Be supposition (m, g)

The index of greatest member.τ _{M, g}As supposition (m, estimated timing slip g).

In one embodiment, can be used for measuring of pattern and protection length detection as giving a definition through improvement:

$D_{m,g}={\tilde{M}}_{m,g}\left({\mathrm{\&tau;}}_{m,g}\right)-W_{m,g},$ Equation (15)

W wherein _{M, g}Estimated or the average noise of mode m and protection length g, and

D _{M, g}Be that pattern and protection length detection are employed through improvement tolerance.

In equation (15), by obtaining

Greatest member and deduct noise W _{M, g}And acquisition D _{M, g}

Can suppose that (m g) calculates D at each _{M, g}In various channel circumstances, (comprise fading channel and low SNR), D _{M, g}Can supply a pattern and protect both accurate detections of length.

In one embodiment, can following estimating noise W _{M, g}:

$W_{m,g}=\frac{1}{N_a\&CenterDot;L_{m,g}}\&CenterDot;\underset{i=1}{\overset{N_a}{\mathrm{\&Sigma;}}}{\tilde{M}}_{m,g}\left(({\mathrm{\&tau;}}_{m,g}-T_{m,g}/2+i)\mathrm{mod}{T}_{m,g}\right),$ Equation (16)

N wherein _aBe the quantity of estimating the employed element of described noise.In equation (16), by to from length T _{M, g}The middle part of the OFDM symbol that receives obtained

N _aIndividual element is sued for peace and is obtained W _{M, g}Suppose that (m, the middle part of OFDM symbol g) is T _{M, g}(it is by τ for/2 section starts away from described OFDM symbol _{M, g}Indication) element.Obtain described N in a looping fashion _a, and the index i of summation holds mould T _{M, g}N _aCan be fixed value (for example, N _a=64) or depend on the configurable value of mode m or protection length g.For instance, can be with N _aBe set to N _m/ 4, N _m/ 8 or the like.

Can be following based on tolerance D _{M, g}Detecting pattern and protection length:

$(\hat{m},\hat{g})=\arg \left(\underset{m,g}{\max }\right\{D_{m,g}\left\}\right).$ Equation (17)

In equation (17), discern the D of all patterns and protection supposition _{M, g}Greatest member.Then, with D _{M, g}The index m and the g of greatest member be provided as the pattern that is detected respectively

And the protection length that is detected

Then, can be following based on producing D _{M, g}The index k ' estimation timing slip τ of greatest member:

$\widehat{\mathrm{\&tau;}}=\arg \left(\underset{k^{\&prime;}}{\max }\right\{{\tilde{M}}_{\hat{m},\hat{g}}\left(k^{\&prime;}\right)\left\}\right).$ Equation (18)

Replacement is searched in equation (18), can store each supposition (m, timing slip τ g) _{M, g}Then, can be with corresponding to D _{M, g}The timing slip τ of greatest member _{M, g}Be provided as estimated timing slip

The estimated timing slip that is obtained from equation (13) or (18) is respectively to produce

Or D _{M, g}The signal path of greatest member.Receiver can receive a plurality of duplicates of institute's transmission signals via a plurality of signal paths.Each signal path has specific complicated gain and the specific delays of being determined by communication environments.Can need to place the FFT window so that catch all or most of useful energy of all signal paths and eliminate or minimize the influence of ISI.

In one embodiment, after pattern and protection detection, implement FAP and detect, and the FAP that is detected is used to place described FFT window.Can implement FAP in every way detects.For the purpose of clear, hereinafter will set forth the specific embodiment that FAP detects.

Detect embodiment for this FAP, at first following calculated threshold:

${\mathrm{TH}}_{\mathrm{FAP}}={\tilde{M}}_{\hat{m},\hat{g}}\left(\widehat{\mathrm{\&tau;}}\right)-D_{\hat{m},\hat{g}}\&CenterDot;G,$ Equation (19)

Wherein

Be institute's detecting pattern and protection length

Greatest member.

Be the D of institute's detecting pattern and protection length _{M, g}Greatest member.

G is a yield value, and

TH _FAPBe that FAP detects employed threshold value.

As mentioned below, gain G influences the placement of described FFT window.Gain G can be fixed value or programmable value and can be through selecting to realize superperformance.For instance, can gain G be set to 7/8,1/2,1/4,1/8,1/16,0 or some other value.

Fig. 5 A shows that the FAP according to embodiment of the present invention detects.For the example shown in Fig. 5 A, show institute's detecting patterns and protection length by curve 510

Element, described curve is at estimated timing slip

The place has peak value.W _{M, g}Indicate estimated noise, and D _{M, g}Indicate the distance between described peak value and the described noise.Calculated threshold TH as shown in equation (9) _FAPAnd by horizontal line 512 expressions.

Discern estimated timing slip and be right after and reach estimated timing slip place left for detecting FAP

Individual element, and be expressed as

Arrive From index k ' initial from 0 to

Obtain described in a looping fashion Individual element, so that

Be The selected next element in back.Described

Individual element is in time early than greatest member

And expression detects the hunting zone of FAP thereon.

With described

Individual element and threshold value TH _FAPCompare, an element of time section start is an element the earliest

And court

Move.First element declaration that surpasses described threshold value is the element of described FAP, and the concordance list of this element is shown k _FAPDetermine index k _FAPWith estimated timing slip

Between distance and it is called FFT window compensation BO _WINOr ${\mathrm{BO}}_{\mathrm{WIN}}=\widehat{\mathrm{\&tau;}}{-k}_{\mathrm{FAP}}.$ If an element is only arranged, and (it is

) surpassing described threshold value, it is 0 minimum value that then described window compensation has.If (it is to select element the earliest

) surpass described threshold value, then described window compensation have for

Maximum.

Then, section start that can the described FFT window of following calculating:

As shown in equation (20) and Fig. 5 A, begin to place described FFT window from the protection interval on the right side of detection FAP.

Fig. 5 A has shown the situation under the mono signal path.Do not having under the situation of noise, when the original duplicate of whole protecting interval and its is relevant, obtaining Peak value, when this comes across index k ' corresponding to the section start of reception OFDM symbol/end, thereby

It is the estimation of the section start of OFDM symbol that receives.

Value along with k ' index little by little further away from each other

And dullness reduces, and this is because the relevant described protection part that little by little diminishes at interval.

If Only there is a signal path in the place and not having under the situation of noise, and is indicated in as Fig. 5 A,

The place have peak value and from

The both sides dullness reduce until approximate And

(it is away from described peak place

Individual sample cycle) locates to reach minimum value.

Be between described peak value and the average noise distance and with

Relevant.

Gain G is determined threshold value TH _FAP, it influences the detection of described FAP and the placement of described FFT window.For instance, if G=1/4, then described threshold value is arranged under the described peak value The place will be in about for waveform shown in Fig. 5 A

The place detects described FAP, and described FFT window will originate in through placement

(its section start apart from described useful part is at the place

).Thereby the section start that the gain of G=x causes described FFT window being positioned over the described useful part of distance is

The place.Thereby, gain G can be considered as " protection mark " compensating parameter.

If

Only there is a signal path in the place, then described FFT window can be positioned over Arrive

Scope in arbitrary place, and described FFT window is caught all useful energies of this signal path and is not produced ISI.Yet, can have a plurality of signal paths.In addition, noise can cause

The random fluctuation of institute's calculated value.Described FAP detects and the FFT window place can be through implementing so that can take into account multipath and because due to the noise

Uncertainty.

Fig. 5 B shows that the FAP of single path channel and three kinds of different multi-path channels detects and the FFT window is placed.For the example shown in Fig. 5 B, protection length is L=1024 sample.Curve 520 shows the single path channel

And in estimated timing slip

Place's (it is at index k '=512 places) has peak value.Curve 522 is presented at dual path channel under the situation of L/4 or the expansion of 256 sample delays

Curve 522 have from Arrive

Steady section.Curve 524 is presented at dual path channel under the situation of L/2 or 512 sample delays expansion

Curve 524 have from

Arrive

Steady section.Curve 526 is presented at dual path channel under the situation of 7L/8 or 896 sample delays expansion Curve 526 have from Arrive

Steady section.

In general, there is under the situation of multipath the relevant flat region that produces of the protection shown in equation (2) and (3) with size of expanding corresponding to the delay of described channel.Exist under the situation of noise, any point in the described flat region can be detected is peak value.Therefore, only to place the FFT window be not preferred and the performance that can cause demoting based on the institute detection peak for some channel.As mentioned below, FAP detection and window compensation can be used for taking into account the inexactness of estimated timing slip and different channels profile length.

Example for shown in Fig. 5 B is arranged at 1/4 with G, and the target window compensation is about 1/4 described protection interval.For the single path channel, the described threshold value of calculating as indicated above is in k _FAPDescribed FAP is detected at=260 places, and the FFT window originates in the 260+1024=1284 place.For the dual path channel that postpones at L/4 under the spread scenarios, described threshold value is lower because of lower peak value, at k _FAPDescribed FAP is detected at=304 places, and the FFT window originates in the 304+1024=1328 place.For the dual path channel that postpones at L/2 under the spread scenarios, at k _FAPDescribed FAP is detected at=344 places, and the FFT window originates in the 344+1024=1368 place.For the dual path channel that postpones at 7L/8 under the spread scenarios, at k _FAPDescribed FAP is detected at=392 places, and the FFT window originates in the 392+1024=1416 place.As illustrated, under the situation of long delay spread more, the more close useful part of described FFT is placed at longer channel profile by this example.As shown in Fig. 5 B, shorten window compensation (it is the distance between the section start of the section start of FFT window and useful part) at longer signal delay.Window compensation is very desirable and allows to catch the suitable safe clearance that more useful energy provides the FFT window to place simultaneously with the dynamic convergent-divergent of channel profile length.

Timings in the ofdm demodulator 160 in Fig. 6 displayed map 3 are obtained and the calcspar of an embodiment of pattern, protection and FAP detecting unit 310.In unit 310, sample buffer 602 receives sample r (k) and stores described sample for subsequent treatment from receiver unit 154.

For example, as shown in equation (2) and (3) or equation (6), protection 610 pairs of described samples of correlator is at interval implemented relevantly, and provides all patterns assessed and the correlated results C of supposition _{M, g}(k).For example, as shown in equation (4) and (5) or equation (7), protection energy calculation unit 620 is calculated protection energy and initial protion thereof at interval, and the E of all patterns and protection supposition is provided _{M, g}(k).For example, as shown in equation (8) and Fig. 4, unit 610 and 620 can be implemented relevant and energy calculating to the difference protection length of set pattern by segmented mode.For example, as shown in equation (9), unit 630 is based on key results C _{M, g}(k) and the protection ENERGY E _{M, g}(k) calculate the tolerance M that all patterns and protection are supposed _{M, g}(k ').640 pairs of tolerance of buffer/accumulator M _{M, g}(k ') implements filtering (for example IIR filtering shown in noncoherent accumulation shown in the equation (11) or the equation (12)), and obtains measuring through filtering of all patterns and protection supposition Buffer 640 storages

Element and as buffer control 642 guidances suitable element be provided.

Initial timing slip detector 650 (for example) is by discerning as shown in equation (14)

Greatest member estimate the timing slip of each pattern and protection supposition.Detector 650 provides the estimated timing slip τ of each pattern and protection supposition _{M, g}And greatest member

For example, as shown in equation (15), unit 660 is based on the greatest member that comes self-detector 650

And estimated noise W _{M, g}Calculate the tolerance D of each pattern and protection supposition _{M, g}For example, as shown in equation (16), unit 660 can be based on the estimated timing slip τ by described supposition _{M, g}Determined position

A group element estimate the noise W of each pattern and protection supposition _{M, g}For example, as shown in equation (17), detector 670 is based on tolerance D _{M, g}Detecting pattern and protection length, and institute's detecting pattern is provided

And the protection length that detects

Final timing slip detector 652 receives the timing slip τ of all patterns and protection supposition _{M, g}And the timing slip that will select pattern and protection supposition is provided as the estimated timing slip that the OFDM that receives of institute transmits

FAP detector 680 is implemented FAP and is detected.For example, as shown in equation (19), but detector 680 calculated threshold TH _FAPFor example, described at Fig. 5 A as mentioned, detector 680 can be then based on described threshold value and institute's detecting pattern and protection length Element detect FAP.Detector 680 provides the index k of the FAP that detects _FAP FFT window generator 690 is based on the index k that comes self-detector 680 _FAPAnd come institute's detecting pattern of self-detector 670 and protection length to produce the FFT window.For example, as shown in equation (20), generator 690 can calculate described FFT window section start and can be based on institute's detecting pattern

Calculate the size of described FFT window.

Buffer controller 642 produce the address (1) that is used for buffer 640 with the proper position at buffer 640 add up, average or filtering M _{M, g}(k), reach (2) from buffer 640 retrievals Correct element.Be that timing slip estimates, buffer 640 is with all patterns and protection supposition

All elements offer detector 650.Be that pattern and protection detect, buffer 640 is with each pattern in the noise-measuring window and protection supposition

Element offer unit 660, as by as described in the estimated timing slip τ of supposition _{M, g}Determine.Be that FAP detects, buffer 640 is with institute's detecting pattern in the described search window and protection length

Element offer FAP detector 680.

Fig. 7 shows the protection calcspar of an embodiment of correlator 610, protection energy calculation unit 620 and metric calculation unit 630 at interval.In correlator 610, unit 710 receives and conjugation sample r (k-N _m).Multiplier 712 multiply by conjugation sample r with sample r (k) ^*(k-N _m) and will export c _m(k) offer delay cell 714 and adder 716.Delay cell 714 provides L _{M, g}The delay of individual sample cycle and output c (k-L _Mg).Can implement delay cell 714 by the shift register that can be initialized as zero.Adder 716 is with c _m(k) with the output of register 718 mutually adduction its output is offered register 718 and adder 720.Adder 716 and register 718 form and add up from all c of multiplier 712 _m(k) Shu Chu accumulator.Adder 720 deducts c (k-L from the output of adder 716 _{M, g}) and correlated results C is provided _{M, g}(k).In each k of sample cycle, by adder 716 c that adds up _m(k) and by adder 720 deduct c (k-L _{M, g}).Unit 714 to 720 is jointly implemented to slide relevant to protection at interval.

In computing unit 620, unit 730a calculates the squared magnitudes of sample r (k), and unit 730b calculates sample r (k-N _m) squared magnitudes.Adder 732 is sued for peace the output of unit 730a and 730b and will be exported e _m(k) offer delay cell 734 and adder 736.Delay cell 734 provides L _{M, g}The delay of individual sample cycle and output e (k-L _{M, g}).Adder 736 is with e _m(k) add the output of register 728 and its output offered register 738 and adder 740.Adder 736 and register 738 form and add up from all e of adder 732 _m(k) Shu Chu accumulator.Adder 740 deducts e (k-L from the output of adder 736 _{M, g}) and the protection ENERGY E is provided _{M, g}(k).In each k of sample cycle, by adder 736 e that adds up _m(k) and by adder 740 deduct e (k-L _{M, g}).Unit 734 to 740 is jointly implemented protection slide energy at interval and is calculated.

What kind of is lost in 630 in calculating, the C of autocorrelator 610 is determined to come in unit 742 _{M, g}(k) value.Multiplier 744 will be from the E of unit 620 _{M, g}(k) multiply by proportionality factor ρ.742 output deducts the output of multiplier 744 and tolerance M is provided adder 746 from the unit _{M, g}(k).

Select method for protection, can institute be received sample r (k) down-sampled (for example, by taking a sample every D sample) to obtain through selecting sample r in sample buffer to select factor D _Dec(k), r wherein _Dec(k)=r (D.k).Then, can implement all calculating mentioned above (comprising recurrence) to institute's selecting sample.

For the dacimation-in-time method, because C _{M, g}(k) and E _{M, g}(k) recursive calculation, can the sample rate operation protection unit in correlator 610 and the protection energy calculation unit 620 at interval.Yet, sub-fraction operation metric calculation unit 630 that can described sample rate.

In one embodiment, in ISDB-T, the dacimation-in-time method can be used for pattern 2 and 3 temporal resolutions (with respect to the OFDM symbol size) with match pattern 1.In one embodiment, can fall protection selects method and time and selects method both are used for all three kinds of patterns of DVB-H.Also can otherwise fall protection and time selects method and is applied to various patterns in described two kinds of systems.

Fig. 6 and 7 Displaying timers obtain and the specific embodiment of pattern, protection and FAP detecting unit 310.Pattern and the protection supposition that can assess arbitrary quantity are transmitted employed pattern protection length to determine the OFDM that received.Can be successively (for example, by time division multiplexing hardware and may operate described hardware) and/or parallel (for example, by duplicate some or all described hardware) with higher clock rate assess described supposition.

Fig. 8 shows an embodiment of the process 800 that is used for derivation pattern and protection detection, timing slip estimation and/or the employed tolerance of other purpose.Can be to each pattern that will assess and protection supposition implementation process 800.For process 800, at interval sample is implemented relevant to obtain correlated results (square 812) at suppose protection.Also definite energy (square 814) of supposing the protection interval.For example as shown in equation (9), derive first/initial tolerance (square 816) based on described correlated results and described energy.For example, by average as shown in equation (11) or by first measuring (square 818) as described in the iir filter filtering as equation (12) described in.As shown in equation (16), for example, based on by estimated timing slip definite position first tolerance a group element estimating noise (square 820).Then, as shown in equation (15), based on derive second through filtering first tolerance and estimated noise/through improvement tolerance (square 822).Described second tolerance is used to detect at least one parameter (for example, pattern, protection length, timing slip or the like) of the transmission that receives.

Also can otherwise derive described tolerance.For instance, can omit suppose protection energy at interval.As another example, can omit described filtering.Described tolerance also can be incorporated the extraneous information of above not setting forth at Fig. 8 into.

Fig. 9 shows in order to an embodiment by the process 900 of selecting the method computation measure.Based on each at least one parameter (square 912) in the some supposition of sample calculation of reception OFDM transmission.Described parameter can comprise C _{M, g}(k), E _{M, g}(k) and/or some other parameter.For set supposition, can calculate described parameter (914) based on a fraction of usable samples.Select method for protection, the sample that can a fraction ofly can be used for set supposition is implemented relevant and energy calculating.Can stride suppose that protection obtaining at interval relevant and energy calculates employed sample.Also can implement relevant with the sample of equal amount and energy calculating at all supposition of assessing.

Be used for described supposition tolerance (square 916) based on the parameter derivation of each in a plurality of supposition.Described tolerance can be M _{M, g}(k ') or some other tolerance.For set supposition, can calculate a fraction of element that can be used for described tolerance and also store (square 918) for described supposition.For the dacimation-in-time method, can derive described tolerance at the sub-fraction in the possible timing slip of set supposition.Also can derive described tolerance to realize the identical temporal resolution of all supposition of assessing (with respect to the OFDM symbol size).

Figure 10 shows the embodiment of process 1000 be used for calculating with segmented mode the parameter of a plurality of supposition.For process 1000, the sample of reception OFDM transmission is implemented relevant to obtain first correlated results (square 1012) of first supposition under the first protection length.Described first correlated results has second correlated results of second supposition of the second protection length of being longer than (for example, twice) described first protection length with acquisition through combination.Can obtain the correlated results of longer protection length by the correlated results of the short protection length of combination.Calculate first protection energy (square 1016) at interval of first supposition.Described first protection energy is at interval protected energy (square 1018) at interval through combination to obtain second of second supposition.Can obtain longer protection energy at interval by the short protection of combination energy at interval.

Figure 11 shows and to be used to detect a pattern that the OFDM that receives of institute transmits and an embodiment who protects the process 1100 of length.Sample based on described OFDM transmission is derived at least one tolerance (square 1112).Described tolerance can be tolerance mentioned above (for example, M _{M, g}(k '),

And D _{M, g}) and/or some other tolerance in one or its arbitrary combination.Can derive the described tolerance of a plurality of patterns and protection supposition.

Detect the pattern and the protection length (square 1114) of OFDM transmission then based on described tolerance.Discern most probable supposition based on described tolerance, and the institute's detecting pattern and the protection length that the pattern and the protection length of this supposition can be provided as described OFDM transmission.Can estimate the timing slip (square 1116) of described OFDM transmission based on described tolerance.Can implement described pattern and protection detection and timing slip in one or more steps based on described tolerance estimates.For instance, as indicated above, can determine the timing slip of each supposition, can use the described timing slip detecting pattern and the protection length of described supposition, and after described pattern and protection detect, estimate the timing slip that described OFDM transmits.Then, handle described sample (square 1118) according to institute's detecting pattern and protection length and estimated timing slip.

Figure 12 shows and to be used to implement that timing that the OFDM that receives of institute transmits is obtained and an embodiment of the process 1200 of pattern and protection detection.Derive in a plurality of patterns and the protection supposition first/initial tolerance (for example, the M of each based on the sample of described OFDM transmission _{M, g}(k ')) (square 1212).Estimate the timing slip (square 1214) of each supposition based on described first tolerance of described supposition.Derive second of described supposition/based on described first tolerance of each supposition and estimated timing slip through improvement tolerance (for example, D _{M, g}) (square 1216).The noise that described first tolerance of each supposition and timing slip can be used for estimating described supposition, it can be used for deriving second tolerance of described supposition again.Detect the pattern and the protection length (square 1218) of described OFDM transmission based on described second tolerance.Then, estimate the timing slip (square 1220) of described OFDM transmission based on described first or second tolerance and institute's detecting pattern and protection length.

Figure 13 shows and to be used to implement that FAP detects and an embodiment of the process 1300 that the FFT window is placed.Based on the pattern that detects the OFDM that receives of institute transmission and protection length employed at least one measure detection FAP (square 1312).Described tolerance can be one or arbitrary combination in tolerance mentioned above and/or some other tolerance.For instance, can derive the tolerance M of the difference possibility timing slip of described OFDM transmission _{M, g}Each element of (k ') can be discerned M _{M, g}The greatest member of (k ') can be determined threshold value based on described greatest member and estimated noise, can select a plurality of elements early than described greatest member, can discern to surpass described threshold value and be the earliest element in chosen elements, can detect FAP based on institute's recognition element.Also can determine described threshold value based on the gain of the target location of indicating the FFT window.

Then, determine FFT window (square 1314) based on detection FAP, pattern and protection length.Described FFT window has the width of being determined by institute's detecting pattern and is positioned over the position determined by detects FAP and protection length (ratio late one of the FAP that detects protect the interval).Select for handling sample (square 1316) based on described FFT window.

The technology of obtaining described herein can be implemented by the whole bag of tricks.For instance, described technology may be implemented in hardware, software or its combination.For the hardware embodiment, estimate timing slip, detecting pattern and protect length, detect FAP and produce that the employed processing unit of FFT window may be implemented in one or more application-specific integrated circuit (ASIC)s (ASIC), digital signal processor (DSP), digital signal processing device (DSPD), programmable logic device (PLD), field programmable gate array (FPGA), processor, controller, microcontroller, microprocessor, other is designed in the electronic unit or its combination of implementing function described herein.

For firmware and/or software embodiment, can implement described technology by the module (for example program, function or the like) of implementing function described herein.Firmware and/or software code can be stored in the memory (for example, the memory among Fig. 1 182) and by processor (for example, processor 180) and carry out.Described memory both may be implemented in processor inside and also may be implemented in the processor outside.

The person of ordinary skill in the field provide above-mentioned explanation to announcement embodiment so that can make or use the present invention.The person of ordinary skill in the field will be easy to understand the various modifications of described embodiment, and General Principle defined herein is also applicable to other embodiment, and this does not deviate from the spirit or scope of the present invention.Thereby the present invention does not wish to be defined as embodiment illustrated herein, and should meet and principle disclosed herein and the corresponding to maximum magnitude of novel feature.

Claims (52)

1, a kind of equipment, it comprises:

At least one processor, it is configured to the protection of supposition is implemented at interval relevant to obtain correlated results, estimating noise is derived tolerance based on the noise of described correlated results and described estimation, and described tolerance is used to detect at least one parameter of the transmission that receives; And

One memory, it is coupled to described at least one processor.

2, the protection that equipment as claimed in claim 1, wherein said at least one processor are configured to determine described supposition at interval energy and further derive described tolerance based on described energy.

3, equipment as claimed in claim 1; wherein said at least one processor is configured to determine the protection energy at interval of described supposition; derive first tolerance based on described correlated results and described energy; described first tolerance is carried out filtering; estimate described noise based on described first group element of measuring, and derive described tolerance based on described first tolerance and described estimated noise through filtering through filtering.

4, a kind of method, it comprises:

The protection of one supposition is implemented at interval relevant to obtain correlated results;

Estimating noise;

Noise based on described correlated results and described estimation is derived tolerance; And

At least one parameter that described tolerance is used to detect the transmission that receives.

5, method as claimed in claim 4, it further comprises:

Determine the protection energy at interval of described supposition, and the described tolerance of wherein said derivation comprises based on the noise of described correlated results, described energy and described estimation and derives described tolerance.

6, a kind of equipment, it comprises:

Be used for the protection of supposition is implemented at interval relevant to obtain the device of correlated results;

The device that is used for estimating noise;

Be used for deriving the device of tolerance based on the noise of described correlated results and described estimation; And

Be used for described tolerance is used to detect the device of at least one parameter of the transmission that receives.

7, equipment as claimed in claim 6, it further comprises:

Be used for determining the device of the protection energy at interval of described supposition, and the wherein said device that is used to derive described tolerance comprises the device that is used for deriving based on the noise of described correlated results, described energy and described estimation described tolerance.

8, a kind of processor readable media that is used for store instruction, described instruction can operate with:

The protection of supposition is implemented at interval relevant to obtain correlated results;

Estimating noise;

Noise based on described correlated results and described estimation is derived tolerance; And

At least one parameter that described tolerance is used to detect the transmission that receives.

9, processor readable media as claimed in claim 8, and it is further used for store instruction, described instruction can operate with:

Determine the protection energy at interval of described supposition, and the described tolerance of wherein said derivation comprises based on the noise of described correlated results, described energy and described estimation and derives described tolerance.

10, a kind of equipment, it comprises:

At least one processor, it is configured to derive at least one tolerance based on the sample of the OFDM transmission that receives via communication channel, detect the pattern and the protection length of described OFDM transmission based on described at least one tolerance, reach according to described institute's detecting pattern and protection length and handle described sample, wherein said pattern is indicated the duration of the useful part of each OFDM symbol in the described OFDM transmission and the protection duration at interval of described each OFDM symbol of protection Length Indication; And

One memory, it is coupled to described at least one processor.

11, equipment as claimed in claim 10, wherein said at least one processor is configured to: for described at least one tolerance is derived in a plurality of supposition, each supposition is used for the various combination of the pattern and the protection length of described OFDM transmission corresponding to supposition; Based on the most probable supposition of described at least one tolerance identification; And the described pattern of described supposition through discerning is provided and protects described institute detecting pattern and the protection length of length as described OFDM transmission.

12, equipment as claimed in claim 11; wherein in described a plurality of supposition each; described at least one processor is configured to the protection of described supposition is implemented at interval relevant to obtain the correlated results of described supposition; estimate the noise of described supposition, and derive described at least one tolerance of described supposition based on the described correlated results of described supposition and the noise of described estimation.

13, equipment as claimed in claim 12; wherein in described a plurality of supposition each, the described protection that described at least one processor is configured to determine described supposition at interval energy and further derive described at least one tolerance of described supposition based on described energy.

14, equipment as claimed in claim 10, wherein said at least one processor are configured to estimate the timing slip of described OFDM transmission based on described at least one tolerance, and further handle described sample based on the timing slip of described estimation.

15, a kind of method, it comprises:

Sample based on the OFDM transmission that receives via communication channel is derived at least one tolerance;

Detect the pattern of described OFDM transmission and protect length based on described at least one tolerance, described pattern is indicated the duration of the useful part of each OFDM symbol in the described OFDM transmission and the protection duration at interval of described each OFDM symbol of protection Length Indication; And

Handle described sample according to described institute's detecting pattern and protection length.

16, method as claimed in claim 15; described at least one tolerance of wherein said derivation is included as a plurality of supposition and derives described at least one tolerance; each supposition is used for the various combination of the pattern and the protection length of described OFDM transmission corresponding to supposition, and the described pattern of wherein said detection and described protection length comprise:

Based on the most probable supposition of described at least one tolerance identification; And

The described pattern of described supposition through discerning and described institute's detecting pattern and the protection length that protection length is transmitted as described OFDM are provided.

17, method as claimed in claim 15, described at least one tolerance of wherein said derivation comprises:

The protection of described supposition is implemented at interval relevant obtaining the correlated results of described supposition,

Estimate the noise of described supposition, and

Derive described at least one tolerance of described supposition based on the described correlated results of described supposition and the noise of described estimation.

18, a kind of equipment, it comprises:

Be used for the device of deriving at least one tolerance based on the sample of the OFDM transmission that receives via communication channel;

Be used for detecting based on described at least one tolerance the device of the pattern and the protection length of described OFDM transmission, described pattern is indicated the duration of the useful part of each OFDM symbol in the described OFDM transmission and the protection duration at interval of described each OFDM symbol of protection Length Indication; And

Be used for handling the device of described sample according to described institute's detecting pattern and protection length.

19, equipment as claimed in claim 18; the wherein said device that is used to derive described at least one tolerance comprises the device that is used to a plurality of supposition to derive described at least one tolerance; each supposition is used for the various combination of the pattern and the protection length of described OFDM transmission corresponding to supposition, and the wherein said device that is used to detect described pattern and described protection length comprises:

Be used for device based on the most probable supposition of described at least one tolerance identification, and

Be used to provide the described pattern of described supposition and protect length as the described institute's detecting pattern of described OFDM transmission and the device of protection length through discerning.

20, equipment as claimed in claim 18, the wherein said device that is used to derive described at least one tolerance comprises:

Be used for relevant device with the correlated results that obtains described supposition is implemented in the protection of described supposition at interval,

Be used to estimate the device of the noise of described supposition, and

Be used for the device of deriving described at least one tolerance of described supposition based on the noise of the described correlated results of described supposition and described estimation.

21, a kind of equipment, it comprises:

At least one processor, its sample that is configured to based on the OFDM transmission that receives via communication channel is that first tolerance is derived in each supposition in a plurality of supposition, each supposition is used for the various combination of the pattern and the protection length of described OFDM transmission corresponding to supposition, estimate the timing slip of described supposition based on described first tolerance of each supposition, derive second tolerance of described supposition based on described first tolerance of each supposition and the timing slip of described estimation, and detect the pattern and the protection of described OFDM transmission based on described second tolerance; And

One memory, it is coupled to described at least one processor.

22, equipment as claimed in claim 21; wherein in described a plurality of supposition each; described at least one processor is configured to the protection of described supposition is implemented at interval relevant to obtain the correlated results of described supposition; determine the described protection energy at interval of described supposition, reach described first tolerance that derives described supposition based on the described correlated results and the described energy of described supposition.

23, equipment as claimed in claim 21, wherein in described a plurality of supposition each, described at least one processor is configured to described first tolerance of described supposition is carried out filtering, based on the described noise of estimating described supposition through first tolerance and the timing slip of described estimation of filtering of described supposition, and derive described second tolerance of described supposition through first tolerance of filtering and the noise of described estimation based on the described of described supposition.

24, equipment as claimed in claim 23, wherein in described a plurality of supposition each, described at least one processor is configured to estimate the timing slip of described supposition, and estimates the described noise of described supposition based on a group element of described first tolerance through filtering in the position of being determined by the timing slip of the described estimation of described supposition.

25, equipment as claimed in claim 21, wherein said at least one processor are configured to estimate based on described second tolerance timing slip of described OFDM transmission.

26, a kind of equipment, it comprises:

The sample that is used for based on the OFDM transmission that receives via communication channel is the device of each derivation first tolerance of a plurality of supposition, and each supposition is used for the various combination of the pattern and the protection length of described OFDM transmission corresponding to supposition;

Be used for estimating the device of the timing slip of described supposition based on described first tolerance of each supposition;

Be used for the device of deriving second tolerance of described supposition based on described first tolerance and the timing slip of described estimation of each supposition; And

Be used for detecting the pattern of described OFDM transmission and the device of protection based on described second tolerance.

27, equipment as claimed in claim 26, the wherein said device that is used to derive described first tolerance comprises:

Be used for relevant device with the correlated results that obtains described supposition is implemented in the protection of described supposition at interval,

Be used for determining the described device of protecting energy at interval of described supposition, and

Be used for the device of deriving described first tolerance of described supposition based on the described correlated results of described supposition and described energy.

28, equipment as claimed in claim 26, the wherein said device that is used to derive described second tolerance comprises:

Be used for the device that carries out filtering is measured in described first of described supposition,

Be used for the described device of estimating the noise of described supposition through first tolerance and the timing slip of described estimation of filtering based on described supposition, and

Be used for device based on described described second tolerance that derives described supposition through first tolerance and the noise of described estimation of filtering of described supposition.

29, a kind of equipment, it comprises:

At least one processor, its sample that is configured to based on the OFDM transmission that receives via communication channel is that in a plurality of supposition each is calculated at least one parameter, wherein each supposition is used for the various combination of the pattern and the protection length of described OFDM transmission corresponding to supposition, and be that in described a plurality of supposition each derives a tolerance based on described at least one parameter of described supposition, wherein at least one supposition, use the sub-fraction of described sample to calculate the sub-fraction that described at least one parameter or storage can be used for the element of described tolerance; And

One memory, it is coupled to described at least one processor.

30, equipment as claimed in claim 29, wherein at described at least one the supposition in each, described at least one processor is configured to use the sub-fraction of the sample that can be used for described supposition to implement to be correlated with.

31, equipment as claimed in claim 29, wherein in described at least one supposition each, described at least one processor is configured to use from the institute of described supposition suppose that the sub-fraction enforcement of the sample that protection obtains at interval is correlated with.

32, equipment as claimed in claim 29, wherein said a plurality of supposition cover at least two different protection length, and wherein said at least one processor is configured to implement relevant to the sample of the equal amount of described a plurality of supposition.

33, equipment as claimed in claim 29, wherein at described at least one the supposition in each, described at least one processor is configured to derive described tolerance for the sub-fraction of the possible timing slip of described supposition.

34, equipment as claimed in claim 29, wherein in described at least one supposition each, described at least one processor is configured so that derive described tolerance with the impartial temporal resolution with respect to the OFDM symbol size of described a plurality of supposition.

35, a kind of equipment, it comprises:

Each that is used for sample based on the OFDM transmission that receives via communication channel and is a plurality of supposition is calculated the device of at least one parameter, and wherein each supposition is used for the various combination of the pattern and the protection length of described OFDM transmission corresponding to supposition; And

Each that to be used for described at least one parameter based on described supposition be described a plurality of supposition derives the device of a tolerance, wherein at least one supposition, use the sub-fraction of described sample to calculate the sub-fraction that described at least one parameter or storage can be used for the element of described tolerance.

36, equipment as claimed in claim 35, the wherein said device that is used to calculate described at least one parameter comprise the sub-fraction that is used to use the sample that can be used for described supposition and implement relevant device.

37, equipment as claimed in claim 35, the wherein said device that is used to derive described tolerance comprise the device that the sub-fraction that is used to the possible timing slip of described supposition derives described tolerance.

38, a kind of equipment, it comprises:

At least one processor, it is configured to the sample of the OFDM transmission that receives via communication channel is implemented relevant first correlated results that has first supposition of the first protection length with acquisition, and making up described first correlated results to obtain to have second second correlated results of supposing of the second protection length, the described second protection length is longer than described first and is protected length; And

One memory, it is coupled to described at least one processor.

39, equipment as claimed in claim 38, the wherein said second protection length is two double-lengths of the described first protection length.

40, equipment as claimed in claim 38; wherein said at least one processor is configured to make up described second correlated results and obtains to have the third phase pass result that the 3rd of the 3rd protection length is supposed, described the 3rd protection length is longer than the described second protection length.

41, equipment as claimed in claim 38; wherein said at least one processor is configured to calculate first protection energy at interval of described first supposition, and described first protection of combination described energy at interval is to obtain second protection energy at interval of described second supposition.

42, a kind of equipment, it comprises:

At least one processor, it is configured to arrive path (FAP) based at least one tolerance detection first of pattern that is used to detect the OFDM transmission that receives via communication channel and protection length, FAP based on described detection determines the FFT window, and selects sample for handling based on described FFT window; And

One memory, it is coupled to described at least one processor.

43, equipment as claimed in claim 42; wherein said at least one processor is configured to implement relevant to obtain correlated results to the protection described sample of being supposed at interval; determine the described protection of supposing energy at interval; estimating noise reaches based on the noise of described correlated results, described energy and described estimation and derives described at least one tolerance.

44, equipment as claimed in claim 42, wherein said at least one processor are configured to based on the definite threshold value of described at least one tolerance and based on described at least one tolerance and the described FAP of described threshold test.

45, equipment as claimed in claim 44, wherein said at least one processor are configured to further determine described threshold value based on the gain of the target location of indicating described FFT window.

46, equipment as claimed in claim 42, wherein said at least one processor is configured to derive first a plurality of elements of measuring into a plurality of possible timing slip of described OFDM transmission, determine the greatest member of described first tolerance, determine threshold value based on the described greatest member of described first tolerance and the noise of estimation, select a plurality of elements early than described greatest member of described first tolerance, discern in described a plurality of element and to surpass described threshold value and be the earliest element, and detect described FAP based on described element through identification.

47, equipment as claimed in claim 42, wherein said at least one processor are configured to described FFT window is placed on by described FAP and the definite position of described protection length after testing.

48, equipment as claimed in claim 42, wherein said at least one processor are configured to described FFT window is placed on described FAP after testing protection length place afterwards.

49, a kind of equipment, it comprises:

Be used for arriving the device in path (FAP) based at least one tolerance detection first of pattern that is used to detect the OFDM transmission that receives via communication channel and protection length;

Be used for determining the device of FFT window based on described FAP after testing; And

Be used for selecting sample for the device of handling based on described FFT window.

50, equipment as claimed in claim 49, it further comprises:

Be used for implementing relevant to obtain the device of correlated results to the protection described sample of being supposed at interval;

Be used for determining the device of the described protection of supposing energy at interval;

The device that is used for estimating noise; And

Be used for deriving the device of described at least one tolerance based on the noise of described correlated results, described energy and described estimation.

51, equipment as claimed in claim 49, the wherein said device that is used to detect described FAP comprises:

Be used for based on described at least one tolerance and indicate the gain of the target location of described FFT window to determine the device of threshold value, and

Be used for device based on described at least one tolerance and the described FAP of described threshold test.

52, equipment as claimed in claim 49, the wherein said device that is used for determining described FFT window comprise be used for described FFT window be positioned over by described after testing FAP and the device of the position determined of described protection length.

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