CN101006676A - Time synchronization using spectral estimation in a communication system - Google Patents

Abstract

To perform time synchronization using spectral estimation, a receiver obtains a frequency response estimate for pilot symbols received on each set of frequency subbands used for pilot transmission. The receiver performs spectral estimation on frequency response estimates for different sets of subbands to obtain a measured arrival time for a transmission from a transmitter. The spectral estimation determines a dominant frequency component in the frequency response estimates and derives the measured arrival time based on this dominant frequency component. A time error between the measured arrival time and a desired arrival time is computed and possibly filtered. The filtered or unfiltered time error is scaled with a fixed or adjustable gain. A time adjustment is then generated based on the scaled time error and using linear and/or non-linear functions. The time adjustment is sent to the transmitter and used to adjust the transmit timing at the transmitter.

Description

In communication system, use the time synchronized of spectrum estimation

The cross reference of coherent reference

The exercise question that the application requires on June 18th, 2004 to submit to is the interim U.S. application No.60/580 of " TimeSynchronization Using Spectral Estimation ", 811 rights and interests.

Technical field

The present invention relates generally to communication, and more specifically, relate to the time synchronized in communication system.

Background technology

Multi-address communication system can be by sharing the communication of supporting a plurality of user terminals to free system resources (for example: time, frequency and/or transmitted power).Each user terminal communicates via the transmission on forward direction and reverse link and one or more base station.Forward link (perhaps down link) is meant the communication link from the base station to the user terminal, and reverse link (perhaps up link) is meant the communication link from user terminal to base station.

On reverse link, the base station can receive the transmission from a plurality of user terminals.Transmission from each user terminal is propagated via different signal path collection.Typically, the signal path that is used for different user terminals has different channel gains and propagation delay.Therefore, for the identical transmission time started, may arrive the base station in the different time from the transmission of these user terminals.If on the base station these transmission are not carried out time calibration rightly, they may interfere with each other so.This interference may influence the ability of base station recovery from the transmission of each user terminal unfriendly, and may reduce the performance of all affected user terminals.

Can service time control loop the timing of each user terminal is regulated, make it be transmitted in the appropriate time and arrive the base station.Because various factors, such as obtain in the transmission accurate measurement of the time of advent at need between the design of control loop may be challenging.This difficulty may be owing to the mode that transmission is sent out, disadvantageous channel condition etc. cause.

Therefore, in the art need be in communication system at the receiver place to accurately measure the time of advent and at the transmitter place to the technology of regularly appropriately regulating.

Summary of the invention

Here described and be used to use spectrum estimation to carry out the technology of time synchronized.Time synchronized need be determined the time of advent of transmission (perhaps signal) at the receiver place and regulate sending regularly at the transmitter place, makes the time that is transmitted in expectation arrive receiver.Typically, because transmitter may begin to send at any time and wireless channel may be introduced unknown delay, so do not know time of advent of transmitting before the receiver.Use spectrum estimation, receiver can obtain the relative accurate time of arrival from the transmission of transmitter is measured.

Using spectrum estimation to carry out among the embodiment of time synchronized, receiver obtains to estimate in the frequency response of the frequency pilot sign that is used for receiving on each sets of frequency subbands of pilot transmission.Receiver can be estimated for different subband set obtains different frequency responses.Then, receiver estimates to carry out spectrum estimation to frequency response, to obtain the measurement time of advent from the transmission of transmitter.As mentioned below, spectrum estimation is determined the main frequency component in the frequency response estimation, and obtains measuring the time of advent based on this main frequency component.The time error of measuring between the time of advent and the expected approach time is calculated, and can be carried out filtering to it with low pass filter.With the gain filtered or not filtered time error is carried out convergent-divergent, this gain can be fix or can be adjusted based on one or more standards.Then, based on the time error of convergent-divergent and use linearity and/or the nonlinear function rise time is regulated.For example, the time can be regulated in the value that is limited in (perhaps soaking into (saturate) exists) preset range, to solve possible inaccuracy in the measurement time of advent.To regulate the time and send to transmitter and use it at the transmitter place and to regulate sending regularly.

Hereinafter carried out more detailed description with embodiment to various aspects of the present invention.

Description of drawings

In conjunction with the accompanying drawings, feature of the present invention and characteristic will become more apparent from detailed description hereinafter, and in the accompanying drawings, similarly reference symbol runs through consistent in full, and wherein:

Fig. 1 shows wireless multiple-access communication system;

Fig. 2 shows and is used to regulate user terminal for the process to the timing of the transfer of data of base station;

Fig. 3 shows the model of time control loop (TCL);

Fig. 4 A and 4B show two kinds of exemplary transmission schemes;

Fig. 5 shows channel profile (profile) and measures response the time of advent;

Fig. 6 shows the step response for the time control loop of different TCL gains;

Fig. 7 shows and is used to use spectrum estimation to carry out the process of time synchronized;

Fig. 8 shows the block diagram of user terminal and base station;

Fig. 9 shows ofdm demodulator and time control unit.

Embodiment

Here employed word " exemplary " refers to " as example, example or illustration ".Here any embodiment or the design that are described as " exemplary " needn't be understood that with respect to other embodiment or design be preferred or favourable.

Fig. 1 shows wireless multiple-access communication system 100.System 100 comprises a plurality of base stations 110, and it supports the communication of a plurality of user terminals 120.Typically, the base station is to be used for the fixed station that communicates with user terminal, and can be called as access point, Node B or some other term.Typically, user terminal 120 is dispersed in the whole system, and each user terminal can be that fix or mobile.User terminal can also be called as travelling carriage, user's set (UE), Wireless Telecom Equipment or some other term.In any given moment, each user terminal can communicate with one or more base station on forward direction and reverse link.For for simplicity, Fig. 1 only shows the transmission on reverse link.For integrated system, system controller 130 is connected to the base station, and coordinates and control for these base stations provide.

Time synchronization technique as described herein can be used for various wireless and wired communication systems.For example, these technology can be used for OFDM (OFDMA) system, time division multiple access (TDMA) system, code division multiple access (CDMA) system, frequency division multiple access (FDMA) system etc.Other example of this multi-address system comprises CDMA multiple carrier (MC-CDMA), wideband CDMA (W-CDMA) and High Speed Downlink Packet Access (HSDPA).These technology can also be used for forward link regulates with the timing to the base station, and can be used for reverse link and regulate with the timing to user terminal.For clarity sake, be the reverse link that is used for wireless ofdma systems hereinafter with these technical descriptions.

The OFDMA system utilizes OFDM (OFDM).OFDM be with the whole system bandwidth efficient be divided into the multi-carrier modulation technology of a plurality of (N) orthogonal frequency sub-bands.These subbands also are called as tone, subcarrier, storehouse and frequency channels usually.Each subband is relevant with separately subcarrier, subcarrier and data can be modulated.In each OFDM symbol period, can all send nearly N modulation symbol on N subband.With N point quick Fourier inverse transformation (IFFT) these modulation symbols are transformed to time domain, comprise the figure shift of N time domain chip or sampling with generation.In order to resist the intersymbol interference (ISI) that causes by the frequency selective fading in the multipath channel, C chip of figure shift carried out repetition, comprise the OFDM symbol of N+C chip with formation, wherein, typically, C is the part of N.Usually, C chip that repeats is called Cyclic Prefix, and C is a circulating prefix-length.The OFDM symbol period is the duration of an OFDM symbol, and equals N+C chip period.

As shown in Figure 1, a plurality of user terminals can send to each base station.User terminal can be arranged in whole system, and can have the different propagation delay to the base station.Because the motion of user terminal, the variation of wireless channel etc., the propagation delay of each user terminal can also change in time.Can regulate timing, to solve the propagation delay that observes by this user terminal from the transmission of each user terminal.This guarantees to arrive each base station by the mode of time calibration and do not interfere with each other from the transmission of different user terminals.

Fig. 2 shows and is used to regulate the process of user terminal for the timing of the transfer of data from the reverse link of this user terminal to base station.At first, user terminal sends to the base station with request message.This message can ask the system of being linked into, request allow on reverse link, to send, or the like.Based on the transmission timing at the user terminal place, this message can comprise an indication information, the zero hour that its indication sends this message.The base station receives request message, and to measuring the time of advent from the transmission of user terminal.Subsequently, for example, based on by indicated transmission time started of request message and by base station measured time of advent, the initial time side-play amount is determined in the base station.This initial time side-play amount is for the base station was received the transmission from user terminal in the appropriate moment, and at the user terminal place to sending the regulated quantity of regularly regulating.The base station sends the initial time side-play amount via signaling channel (SCH).User terminal receives the initial time side-play amount, it is sent regularly regulate in view of the above, and use the initial time side-play amount that data are sent.

The base station receives the transfer of data from user terminal, and to measuring the time of advent of this transmission.After this final transmission, the propagation delay of user terminal may change.In this case, the time of advent of transfer of data can be different with the expected approach time of transfer of data, and the expected approach time of this transfer of data can be the beginning that the base station has been distributed to the time interval of user terminal.Calculate the difference or the error that record between the time of advent and the expected approach time base station, and the time of definite user terminal is regulated.Then, the base station is regulated via the SCH transmitting time.User terminal is regulated the time and is received, and it is sent regularly upgrade in view of the above, and use the time offset of upgrading that data are sent.

Typically, regularly adjustment process continues in from the whole data transmission procedure of user terminal.The base station is to measuring the time of advent of each transmission of receiving from user terminal, and definite time is regulated.Regularly regulate for each that receives from the base station, user terminal sends regularly it and upgrades.Regulate the current transmission timing of determining user terminal by the initial time side-play amount being added the institute that receives from the base station is free.User terminal regularly is used for current transmission the transmission of base station.

Fig. 3 shows the exemplary model 300 of the time control loop (TCL) between user terminal 120x and the base station 110x.User terminal uses its current transmission regularly to transmit on reverse link.This transmission observes the propagation delay by wireless channel, and the multipath in the wireless channel also may make transmission distortion.Propagation delay can change arbitrarily in time.

At base station place, 310 pairs of transmission from user terminal of the measuring unit time of advent receive, and institute is received measure the time of advent of transmitting, and measurement time of advent is provided.Adder 312 deducts from expected approach time measures the time of advent, and the time error of the transmission that receives is provided.Delay cell 314 provides the delay of a update cycle for the time control loop.Delay cell 314 is included in the model 300, is the delay of considering during the time control loop upgraded.This updating delay is caused by the following fact: till the next TCL update cycle, also do not reflected in the transmission regularly at the user terminal place in the measurement time of advent that current TCL did in the update cycle.To regulate the speed that sends to user terminal the time by the base station and determine the TCL renewal rate, and therefore determine the TCL update cycle.That the TCL renewal rate can be fixed or depend on that system design changes.

Multiplier 316 error time of delay of self-dalay unit 314 in the future gains with TCL and multiplies each other, and the time error behind the convergent-divergent is provided.As mentioned below, the loop characteristics of time control loop has been determined in the TCL gain.Time error behind 318 pairs of convergent-divergents of preprocessor quantizes, and quantized value is carried out reprocessing (if having reprocessing), and the time adjusting to receive transmission is provided.For example, preprocessor 318 can adopt saturated set and will regulate the time in the value that is limited in preset range.Time is regulated indicating user terminal and whether should shift to an earlier date or delay its transmission regularly, makes in expected approach time the transmission from user terminal to be received.The time that can provide with predetermined unit (for example: 8 chips are unit) is regulated.The base station will be regulated via forward link and send to user terminal the time.

At the user terminal place, 320 pairs of times from the base station of adder are regulated and receive, and this time is regulated and the regularly summation of previous transmission that is stored in the register 322, and provided current transmission regularly.Current transmission regularly is stored in the register 322, and uses it for the next one transmission of base station.Adder 320 and register 322 constitute accumulator, and this accumulator is regulated based on the time that receives from the base station transmission of user terminal is regularly upgraded.

Processing for the initial time side-play amount can be different with the processing of regulating for the time.For example, can be with 1 (rather than TCL gain) time error of first transmission of receiving from user terminal is carried out convergent-divergent, obtaining the initial time side-play amount, and can omit reprocessing.Adder 320 can with regulate identical mode for the time, initial time side-play amount and previous transmission are regularly sued for peace.

Fig. 3 shows the single order time control loop that has an accumulator in loop.Also can use control loop At All Other Times, the transmission at user terminal place is regularly regulated, to solve the propagation delay of introducing by wireless channel.For example, can also use second order time control loop.

Can use various technology to measuring the time of advent of transmission.Can be based on various factors, such as the mode that data and pilot tone are sent out, select appropriate measuring technique in system.Pilot tone is a given data processed in known manner and that send.Transmitter can send pilot tone, to help the various functions of receiver realization such as time synchronized, channel estimating, frequency correction, automatic gain control etc.Hereinafter described and be used for several exemplary transmission schemes that data and pilot tone are sent.

Fig. 4 A shows frequency hopping (FH) transmission plan 410 that can be used for the OFDMA system.Frequency hopping can be carried out randomization to interference, and the frequency diversity of the harmful path effects of antagonism is provided.Adopt frequency hopping, for each user terminal distributes different FH sequences, the particular sub-band that this FH sequence indication is used in each hop period.Each hop period can be crossed over one or more OFDM symbol period.Each FH sequence can select subband to be used for transmission in pseudorandom ground.The FH sequence mutually orthogonal that is used for the different user terminals that communicates with same base station, making does not have two user terminals to use identical subbands in any given hop period.Disturb " in the sub-district " between the user terminal that this has been avoided and same base station communicates.The FH sequence that is used for each base station is pseudorandom with respect to the FH sequence that is used for neighbor base station.This to and the user terminal that communicates of different base station between " minizone " disturb and carried out randomization.

For the example shown in Fig. 4 A, all N subbands are constituted the S subband set, and each collection comprises M subband, wherein, N=M * S, M 〉=1 and S＞1.M subband in each collection can be adjacent (shown in Fig. 4 A) or non-conterminous.In each hop period, can distribute a subband set for each user terminal.Shown in Fig. 4 A, data symbol (it is a modulation symbols for data) and frequency pilot sign (it is the modulation symbol of pilot tone) can be carried out Time Division Multiplexing.The reverse link that for example, transmission plan 410 can be used for the OFDMA system.

Fig. 4 B shows the transmission plan 420 that interweaves that also can be used for the OFDMA system.For the example shown in Fig. 4 B, constitute the S subband set, each collection comprises M subband.For frequency diversity is provided, can each M subband concentrating be evenly spaced apart with the spacing of S subband.Like this, shown in Fig. 4 B, the S subband set interweaves mutually.In each OFDM symbol period, a subband set can be used for pilot transmission, and remaining S-1 subband set is used for transfer of data.In different OFDM symbol periods, different subband set can be used for pilot transmission.Can select these subband set with pseudo-random fashion (for example: adopt the PN sequence) or definite mode (for example: shown in Fig. 4 B, adopting predetermined length is the sequence of S).The forward link that for example, transmission plan 420 can be used for the OFDMA system.

The combination of transmitted scheme of two kinds of schemes shown in Fig. 4 A and the 4B can be used for reverse link.For this transmission plan, for example, shown in Fig. 4 B, constitute S the subband set that interweaves.Yet for example, shown in Fig. 4 A, each hop period is crossed over a plurality of OFDM symbol periods, and in each hop period, on each subband data and pilot tone is carried out time division multiplexing.

Generally speaking, can constitute any number subband set, and each collection can comprise any combination of any number subband and subband.Depend on the specified scheme that is used for data and pilot transmission, can arrive time measurement and time synchronized in a different manner.

In one embodiment, use spectrum estimation to carry out time synchronized.Spectrum estimation can provide relative accurate time of arrival to measure based on narrowband pilot, wherein, each only on the part of whole system bandwidth, this narrowband pilot of transmission on M the subband in whole N subbands shown in Fig. 4 A or the 4B for example.Spectrum estimation can also be used for broadband pilots, wherein, for example in data TDM mode, this broadband pilots of transmission on all or most of subband of whole N subbands.

Can show the feature of wireless channel in the OFDMA system by channel impulse response or corresponding channel frequency response.As used herein, and it is consistent with conventional term, and channel impulse response is the time-domain response of wireless channel, and channel frequency response is the frequency domain response of channel.In sampled-data system, channel frequency domain response is the discrete Fourier transform (DFT) of channel impulse response.Channel impulse response is made up of " channel tap " sequence, postpones (perhaps abbreviating " tapped delay " as) by channel tap gain (perhaps abbreviating " tap gain " as) and channel tap each channel tap is defined.Channel frequency response is made of one group " channel gain ", and each channel gain is used for specific subband.

Channel impulse response has L interested channel tap, and for example L has the channel tap of sufficient intensity, wherein, and L≤N.Each channel tap has complex gain h _iAnd be positioned at and postpone d _iThe place.Usually, each channel tap can 1 and N between any position (perhaps 1≤d _i≤ N), wherein, N also is the time span or the length of wireless channel.L tap gain is expressed as { h _i, perhaps for i=1,2 ... the h of L _iL tapped delay is expressed as { d _i, perhaps for i=1,2 ... the d of L _iTap gain { h _iBe correlated random variables, this variable is expanded determined speed with the Doppler by wireless channel and is changed.L tap gain { h _iAnd L tapped delay { d _iBe unknown, and can as mentioned below it be estimated.

In the z territory, can represent channel impulse response by L tap finite impulse response (FIR) (FIR) filters H (z), as follows:

$H\left(z\right)=\underset{i=1}{\overset{L}{\mathrm{\Σ}}}{h}_i\·z^{-d_i}$ Formula (1)

Wherein, z ^-1Represent the delay of a chip period, and z ^-diRepresent the delay of i channel tap.Can represent channel impulse response by the vectorial h in L * 1, not have explicit reference tapped delay { d _i, as follows:

h=[h ₁h ₂... h _L] ^TFormula (2)

Wherein, " T " represents transposition.

Can the channel outline definition is as follows:

P=diag＜ h h ^TFormula (3)

Wherein,＜represent time average to operate;

Diag{ MBe only to have matrix MThe diagonal matrix of diagonal entry; And

PIt is the L * L diagonal matrix that is used for the channel profile.

Diagonal matrix comprises along the possible nonzero value of diagonal and the null value of other position. PDiagonal entry representative by hThe channel profile of definition.The long-term time average energy of channel tap in the impulse response of channel profile indicating channel.The channel profile does not comprise the short-term effect such as decline, Doppler etc.Therefore, the reflectance/transmittance of channel profile indication media, signal can be propagated via this media.

Can estimate the frequency domain channel gain for each subband that is used for pilot transmission, as follows:

$H_k=\frac{y_k}{p_k},k=\mathrm{1,2},...M$ Formula (4)

Wherein, y _kIt is the frequency pilot sign of the subband k that receives;

p _kIt is the frequency pilot sign that on subband k, sends; And

H _kThe channel gain that is subband k is estimated.

For for simplicity, for example, shown in Fig. 4 A, formula (4) is assumed to pilot transmission and uses M continuous subband, makes sub-band serial number k arrange from 1 to M.Generally speaking, can use any subband for pilot transmission, and known these subbands of receiver.

As shown in formula (4), can be based on the frequency pilot sign that on the M that is used for a pilot transmission subband, is received, to M channel gain { H of these subbands _kEstimate.Channel gain is a frequency domain value.Each channel gain can be expressed as the Fourier transform of L (the unknown) time domain channel tap, as follows:

$H_k=\underset{i=1}{\overset{L}{\mathrm{\&Sigma;}}}(h_i\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="A20058002793400341.png,A20058002793400351.png"\; state="\{\{state\}\}">e</figure-callout>}}^j+n_i)=\underset{i=1}{\overset{L}{\mathrm{\&Sigma;}}}(h_i\&CenterDot;e^{j{\mathrm{\&omega;}}_i(k-1)}+n_i),k=\mathrm{1,2},...M$ Formula (5)

Wherein, ω _i=2 π d _i/ N is the angular frequency (is unit with the radian) that is used for i channel tap; And n _iIt is the noise of i channel tap.

The factor " k-1 " (and not being " k " just) in the formula (5) in the index be since sub-band serial number since 1 rather than 0.Angular frequency _i, i=1,2 ... L is channel gain { H _kFrequency component, and directly related with the unknown tapped delay of channel impulse response.Like this, as mentioned below, by to channel gain { H _kCarrying out spectrum estimation, can estimate tapped delay.

Formula (5) can be expressed as matrix form, as follows:

Formula (6)

Perhaps H= Qh+ nFormula (7)

Wherein, HIt is M * 1 vector that comprises the channel gain estimation of M subband;

QIt is M * L " Fourier-type " matrix that comprises element shown in the formula (6); And nIt is L * 1 noise vector.

For example, shown in Fig. 4 A or 4B, in the different time intervals, can send pilot tone having on the difference collection of M subband.For the transmission plan shown in Fig. 4 A, can be at subband k=1 in a time interval, 2 ... the last transmission of M pilot tone, then in the next time interval at subband k=1+b, 2+b ... the last transmission of M+b pilot tone, or the like, wherein, b can be by the determined any offset value of FH sequence.At subband k=1+b, 2+b ... the channel gain of the pilot tone of the last transmission of M+b can be expressed as:

H _b= Q B h+ nFormula (8)

Wherein, B is L * L diagonal matrix, $\underset{\&OverBar;}{B}=\mathrm{diag}(e^{{\mathrm{jb\&omega;}}_1},e^{{\mathrm{jb\&omega;}}_2},...e^{{\mathrm{jb\&omega;}}_L}).$

Can with HRelevant (perhaps apposition) defined matrix of M * M be HH ^H, wherein, " H " represents conjugate transpose.With RRepresentative HThe long-term time average of correlation matrix, it can be expressed as:

R=＜ H H ^H〉= Q P Q ^H+ σ ² IFormula (9)

Wherein, IBe to have along cornerwise 1 and 0 unit matrix of other position; And σ ²It is the variance of noise.

Based on formula (3), (7) and (8) acquisition formulas (9).Can select different b offset value (for example :), feasible matrix corresponding to all different offset values with the pseudo-random fashion shown in Fig. 4 A or in the definite mode shown in Fig. 4 B BAverage out to 0.In this case, if the correlation matrix that obtains at interval at different time is carried out the average of capacity, matrix B is eliminated and is not existed so RThe middle appearance.Formula (9) supposes that also interchannel noise is additive white Gaussian noise (AWGN), and it has zero-mean, variances sigma ², and auto-covariance matrix  _Nn=σ ² I

Can be to matrix RCarry out eigen value decomposition, as follows:

R= V D V ^HFormula (10)

Wherein, VBe RThe M * M unitary matrice of eigenvector; And

DBe RThe M * M diagonal matrix of eigenvalue.

Unitary matrice MHas attribute M ^H M=I.Each row mutually orthogonal of unitary matrice, and every row have unimodular value (unit power).Gibert Strang is " Linear Algebra andIts Applications ", second edition, Academic Press at exercise question, in 1980 the book eigen value decomposition is described.

D MIndividual diagonal entry is called REigenvalue. V MIndividual row are called REigenvector. VEach row corresponding to DIn an eigenvalue.Like this, VFirst row or left column corresponding to DFirst row in diagonal entry, VSecondary series corresponding to DSecondary series in diagonal entry, or the like.

Can with DIn M eigenvalue from the minimum to the maximum, sort, and the ordering after it is expressed as { λ ₁, λ ₂... λ _M, wherein, λ ₁Be minimum eigenvalue and λ _MIt is maximum eigenvalue.When right DIn eigenvalue when sorting, right VIn eigenvector correspondingly sort.If M＞L, so DIn M-L minimum eigenvalue (promptly from λ ₁To λ _M-L) equal noise variance σ ², and be referred to as " noise " eigenvalue.Will VIn corresponding to M-L eigenvector of M-L noise eigenvalue (that is: after the ordering VThe most left M-L row) be called R" noise " eigenvector, and it is expressed as v ₁, v ₂... v _M-L.This noise eigenvector with QThe row quadrature.

L tap gain/power is included in matrix PIn, and L tapped delay be included in matrix QIn. QL row in every row have following form:

q _l=[1, e ^{J2 π (l-1)/N}, e ^{J2 π 2 (l-1)/N}... e ^{J2 π (M-1) (l-1)/N}] formula (11)

Wherein, l is the label of the unknown tapped delay of expression, and it is in 1 to N scope, perhaps l ∈ 1,2 ... N}.

Cost function can be defined as follows:

$C\left(l\right)=\frac{1}{\underset{k=1}{\overset{M-L}{\mathrm{\&Sigma;}}}{|{\underset{\&OverBar;}{q}}_l^H\&CenterDot;{\underset{\&OverBar;}{v}}_k|}^2},l=\mathrm{1,2},...N$ Formula (12)

As follows, can obtain L unknown tapped delay based on cost function C (l).Can be about N the probable value of l, i.e. l=1,2 ... N, in each value computational costs function.Each value representative of l is used for the supposition length of delay of channel tap.For each l value, determine vectorial q at first as the formula (11) _l, and in itself and M-L the noise eigenvector each multiplied each other, to obtain M-L inner product $g_k={\underset{\&OverBar;}{q}}_l^H\&CenterDot;{\underset{\&OverBar;}{v}}_k,$ k＝1，2，...M-L。Then, the mould (power) with each inner product is calculated as ${\left|g_k\right|}^2=g_k\&CenterDot;g_k^{*},$ Wherein, " ^*" represent complex conjugate.Then, the mould of M-L inner product is sued for peace, and the cost value C of the inverse conduct of the mould after the summation for this l value is provided _lFor N possible l value obtains N cost value C _l, l=1,2 ... N.

Because QRow and noise eigenvector quadrature, so QAny row and the inner product of any noise eigenvector is all very little or be zero.Therefore, QThe total mould value of M-L inner product of every row very little, and it is very big to amount to inverse of mould value.Then, identify N the maximum of the L among the cost value.Represent L unknown tapped delay of channel impulse response corresponding to L l value of this L costs on the higher scale value.This L l value that identifies is used to constitute matrix Q, and be used for constituting matrix with known b offset value BSo, can obtain L tap gain, as follows:

h _b= B ^-1 Q ^-1 H _bFormula (13)

Wherein, H _bBe to have M * 1 vector that the frequency response of a collection of M pilot subbands is estimated, and

h _bIt is L * 1 vector with channel impulse of L tap.

Can estimate H for frequency response _bCalculate impulse response and estimate h _b, H wherein _bBe to obtain according to the pilot transmission that on a subband set, is received.Can estimate to average to the impulse response of different sub-band collection, to obtain to have the average impulse response estimation of L tap.

In description above, the number that L representative will estimative channel tap, wherein, L≤M.Generally speaking, L can equal or can be not equal to the number (L of channel tap in the actual pulse response of wireless channel _Actual).If L=L _Actual＜M so can be as indicated above to L _ActualIndividual channel tap is estimated.If L ≠ L _ActualE L＜M, L the channel tap that so can acquisition as indicated above be used for the channel profile of wireless channel represented.Generally speaking,, can estimate, bring high accuracy and high-resolution more channel tap along with the increase of M.Equal or approach the broadband pilots of N for M, can estimate all channel impulse response based on broadband pilots with nearly N tap.

In order measuring the time of advent to the transmission that receives via wireless channel, can be set to equal 1 by L and to carry out the spectrum estimation technique shown in the formula (1) to (12).If L=1 supposes M greater than 1, spectrum estimation technique provides the individual channel tap that is positioned at channel profile center so.Tapped delay corresponding to this individual channel tap can be as the measurement time of advent of this transmission.

For the example wireless channel in the exemplary OFDMA system, for Computer Simulation has been carried out in the measurement time of advent of using spectrum estimation to carry out.This OFDMA system has the total system bandwidth of 5MHz and use and has 1024 subbands (N=1024) altogether, OFDM structure that each is concentrated 16 subbands (M=16) and has the circulating prefix-length of 48 chips (C=48).Each OFDM symbol period is 214.4 microseconds, perhaps (1024+48)/(5 * 10 ⁶).Each hop period is crossed over 7 OFDM symbol periods or 1.5 milliseconds.Shown in Fig. 4 A, in the middle of each hop period, send a frequency pilot sign.

Wireless channel has the channel profile of 38 chip lengths, perhaps { d _i}={ 1,2 ... 38}, it approximately is 80% of a circulating prefix-length.For each TCL update cycle, can carry out modeling to the channel profile with different random value sequences.The channel profile changes from a TCL update cycle to the next TCL update cycle with random fashion, and the feasible random value sequence that is used for the channel profile of current TCL update cycle is uncorrelated with being used for the random value sequence of previous TCL update cycle.Interchannel noise is the AWGN noise, and the signal to noise ratio (snr) that is used for the pilot tone that receives is 0 decibel (dB).

Arrive time measurement at each TCL in update cycle, make that measuring speed is identical with the TCL renewal rate.The TCL update cycle is 90 milliseconds, and each measurement time of advent is based on the frequency pilot sign that is received in 60 hop periods.For each hop period, obtain channel frequency response vector H based on the frequency pilot sign that in this hop period, is received _bIn each hop period, based on vector H _bTo matrix RUpgrade.After 60 hop periods, by carrying out formula (10) to (12) to calculating the time of advent with L=1.

Fig. 5 shows the curve 510 in TCL channel tap of wireless channel in the update cycle.For the TCL update cycle is selected 38 channel tap randomly.The curve 520 of measuring response the time of advent that provides by spectrum estimation technique also is provided Fig. 5.As estimated by spectrum estimation technique, the peak value of curve 520 is centers of channel profile.Fig. 5 illustrates: even in each hop period, the number that outnumbers the subband that is used for pilot transmission of channel tap, spectrum estimation technique also can be determined the center of channel profile.Provide corresponding to moment at channel profile center as measuring the time of advent.

Return with reference to figure 3, multiplier 316 carries out convergent-divergent with the TCL gain to the time error from adder 312.The damping coefficient of loop bandwidth and time control loop has been determined in TCL gain, the transient response of itself and then definite time control loop.Generally speaking, bigger TCL gain is corresponding to wideer loop bandwidth and response time faster, still for the noise wireless channel corresponding to more timing jitter.On the contrary, littler TCL gain is corresponding to narrower loop bandwidth and slower response time, still for the noise wireless channel corresponding to still less timing jitter.

About described exemplary OFDMA system of Fig. 5 and example wireless channel, the performance of time control loop is carried out emulation for above.For this emulation, be 0 chip offset the initial time of advent of the transmission that receives, and expected approach time is-15 chip offset.Each TCL update cycle (its for per 60 hop periods or per 90 milliseconds) is to measuring the time of advent, and also the time control loop upgraded in the update cycle at each TCL.

Fig. 6 shows for the step input with different TCL gains, the curve of the response of time control loop.Curve 610,620 and 630 shows the step response of the time control loop with TCL gain 0.1,1.0 and 1.5 respectively.Curve 610 shows the step response with about 3 second stabilization time, and it may be too slow.Curve 630 shows the step response with 8 chip overshoots and vibration, and it may not expected.Figure 62 0 shows has fast and stable to the expectation time of advent and there is not the step response of overshoot.Though do not illustrate in Fig. 6, the TCL gain with 0.5 can realize having the step response of about 200 milliseconds of time constants and noise still less.Preprocessor 318 by Fig. 3 does not have infiltration ground acquisition step response shown in Figure 6.

As shown in Figure 6, TCL gain effects loop characteristics, it has determined the response time and the noiseproof feature of time control loop.The TCL gain can be based on the selected fixed value of balance between these two performance standards.The TCL gain can also be based on the selected configurable value of channel condition.For example,, can use high TCL gain, and, can use low TCL gain for low SNR in order to improve noiseproof feature for high SNR in order to improve tracking performance.Can estimate SNR based on the pilot tone that receives.The height displacement speed that high TCL gain can also be used for the channel profile, and can be used for the low displacement speed of channel profile with hanging down the TCL gain.Can estimate the displacement speed in the channel profile time of advent based on measuring.For example, if a plurality of time errors (perhaps a high proportion of time error) occurred, can infer high displacement speed so for same direction.High TCL gain can also be used for the low variance of the measurement time of advent, and it can indicate the static relatively or static channel of user terminal fixing or Hypomobility.On the contrary, low TCL gain can be used for the high variance of the measurement time of advent, and it can indicate the fast-changing channel of the user terminal of high mobility.Can determine the displacement speed of channel profile, and use it for to TCL gain regulate and some characteristic of inferring wireless channel (for example: speed).

Can also gain to TCL based on operational mode and be configured.For example, high TCL gain can be used, and low TCL gain can be used at tracking phase at acquisition phase.Acquisition phase can be crossed over the first few TCL update cycle, and tracking phase can be crossed over the remaining TCL update cycle.

Spectrum estimation technique provides accurate time of arrival to measure usually, estimates extremely coarse time of advent but may produce once in a while.Typically, the constraint of velocity of user terminal the channel profile maximum rate that can be shifted.For example, spectrum estimation technique may produce to be estimated coarse time of advent, the several chips of its inaccuracy (for example: for by the sight of emulation, ± 4 chips).For each TCL update cycle, the maximum shift speed in the channel profile can be the part chip (for example: 0.1 chip).If spectrum estimation technique produces with measuring measures of dispersion the previous time of advent and measures the very big time of advent, so just very may there be the measurement inaccuracy.In this case, in the time control loop is upgraded, can give littler weight for the current measurement time of advent.Can the littler weight of accomplished in various ways.

In one embodiment, will soak in the value of preset range from the scaled time error of multiplier among Fig. 3 316 by preprocessor 318.Can select this scope based on the maximum shift speed in the channel profile.For example, if maximum shift speed is every TCL update cycle 0.1 chip, can be regulated being limited in so the time+1 chip is in the scope of-1 chip.This infiltration has reduced owing to estimate caused timing jitter amount coarse time of advent.

In another embodiment, if obtain a plurality of big time errors, preprocessor 318 provides the big time to regulate so.As indicated above, preprocessor 318 can be regulated the time that is used for first big time error and limit.If follow-up time error is also very big, preprocessor 318 can provide the big time to regulate so, and this can really appoint the accuracy of measuring the previous time of advent.Should " waits-affirmation " scheme can allow loop response faster, great time of advent of measure error is permitted in elimination simultaneously.

In another embodiment, replace delay cell 314 with low pass filter, this low pass filter carries out filtering to the time error from adder 312.The bandwidth of this low pass filter is enough wide, makes filter response not make unfavorable change to the closed loop characteristic of time control loop.

In another embodiment, (1) if the amplitude of time error in preset range, preprocessor 318 just (for example: linearity) regulated to the time based on first of time error by function call, and (2) if amplitude outside predetermined scope, preprocessor 318 is just regulated to the time based on second (for example: non-linear) function call of time error.Nonlinear function can be to block or soak into, and can be wait-affirmation scheme mentioned above, perhaps can be some other function.

Foregoing description supposition user terminal is regulated the time that is sent by the base station and is correctly received.Depend on how the time adjusting sends, may have error in regulating in the time that is received.Can the design time control loop so that solve these errors.For example, in order to reduce error rate, can send regularly regulating more continually and/or with higher transmitted power.

Fig. 7 shows and is used to use spectrum estimation to carry out regularly synchronous process 700.For obtaining frequency response, the frequency pilot sign that receives estimates (square frame 710) on each subband set.Can estimate for different subband set obtains different frequency responses.Then, frequency response is estimated to carry out spectrum estimation, measure the time of advent (square frame 712) with acquisition.Spectrum estimation has been determined the main frequency component in the frequency response estimation, and obtains measuring the time of advent based on this main frequency component.

Determine to measure the time error (square frame 714) between the time of advent and the expected approach time.Can carry out filtering to time error with low pass filter.With TCL gain filtered or not filtered time error is carried out convergent-divergent, this TCL gain can be a fixed value or based on channel condition and/or the determined adjustable value of selected operational mode (square frame 716).Then, regulate (square frame 718) based on scaled time error generation time.Time can be regulated in the value that is limited in preset range, perhaps generate this time adjusting, measure inaccuracy to solve based on linearity and/or nonlinear function.

In description above, the measurement time of advent is based on this understanding: the unknown tapped delay (d that will be determined _iI=1,2 ... L) be the unknown frequency component (ω that gains according to the frequency domain channel that the frequency pilot sign that receives obtains _iI=1,2 ... L).Then, carry out spectrum estimation (perhaps spectrum analysis), to determine the unknown frequency component of channel gain.In case determined these frequency components, these frequency components are just as the estimation of the unknown tapped delay of channel impulse.For measuring the time of advent, spectrum estimation technique provides the main frequency component of channel gain, uses it to obtain measuring the time of advent then.

Spectrum estimation technique can provide accurate time of arrival to measure for (1) each broadband pilots that only sends on whole or most of system bandwidths in the narrowband pilot that sends on the sub-fraction of system bandwidth and (2).For narrowband pilot, on any given time, only can observe the sub-fraction system bandwidth.Be used for the restriction that definite resolution of transmitting the time of advent is subjected to the bandwidth of channel observation.For example, if only send pilot tone on M subband at every turn, wherein, M can be much smaller than N, and so based on the pilot tone that is received on this M subband, receiver only can observed wireless channel on the arrowband relatively.Therefore, can obtain to have temporal resolution T based on have the narrowband pilot that is received on the collection of M subband at any one _OfdmMeasure the thick time of advent of/M, wherein, and T _OfdmIt is the duration of no Cyclic Prefix in OFDM System symbol.Spectrum estimation technique can provide has temporal resolution T _OfdmThe accurate time of arrival more of/N is measured.Example is illustrated as mentioned, if M much smaller than N, T so _Ofdm/ N can be than the temporal resolution T that is obtained with any one narrowband pilot transmission _Ofdm/ M is much meticulous.For time synchronized, minimize for fear of the interference between a plurality of transmitters or to the interference between a plurality of transmitters, and simultaneously, handle for receiver, in order to capture energy as much as possible in each received OFDM symbol, the accurate time of arrival measurement is important.

For clarity sake, above the specific frequency spectrum estimation technique that is commonly called Multiple Signal Classification (MUSIC) technology is described.Can also use other spectrum estimation technique to determine the frequency component that frequency response is estimated, and and then the tapped delay estimated of definite impulse response, and this is within the scope of the invention.For example, can carry out spectrum estimation based on periodogram technology, Prony estimator, Pisarenko harmonic wave decomposition technique etc.Typically, every kind of spectrum estimation technique utilizes certain type average, to obtain the good estimation to the frequency component of looking for.S.L.Marple Jr. is at " A Tutorial Overview of Modern SpectralEstimation ", Proc.IEEE, 1989, among the pp.2152-2157 and B.D.Kao and K.S.Arun at " Model Based Processing of Signals:A State SpaceApproach ", Proc.IEEE, Vol.80, No.2, Feb 1992, among the pp.283-309 these various spectrum estimation techniques that comprise the MUSIC technology are described.

Fig. 8 shows the block diagram of user terminal 120x and base station 110x.On reverse link,, send 810 pairs of business datums of (TX) data processor and receive, format, encode, interweave and sign map, and modulation symbol (perhaps data symbol) is provided at user terminal 120x place.820 pairs of data symbols of OFDM modulator and frequency pilot sign receive, and carry out the OFDM modulation, and OFDM is provided symbols streams.For example, shown in Fig. 4 A, can send pilot tone and data symbol in every way.822 pairs of OFDM symbols streams of transmitter unit (TMTR) receive and regulate (for example: transform to simulation, amplification, filtering and frequency up-converted), and generate reverse link signal, via antenna 824 this reverse link signal are sent to base station 110x.

At base station 110x place, 852 pairs of reverse link signal of antenna receive, and received signal is offered receiver unit (RCVR) 854.Receiver unit 854 is regulated (for example: filtering, amplification and frequency downconverted) to received signal, the signal after regulating is carried out digitlization, and the chip that receives is offered ofdm demodulator 856.The chip of 856 pairs of receptions of ofdm demodulator carries out the OFDM demodulation, the data symbol that receives is carried out Data Detection, and detected data symbol is provided, and this detected data symbol is to sending the estimation of data symbol.Receive 858 pairs of detected data symbols of (RX) data processor and carry out symbol de-maps, deinterleaving and decoding, to recover to send data.The processing of being undertaken by ofdm demodulator 856 and RX data processor 858 respectively be complementary at user terminal 120x place by the processing that OFDM modulator 820 and TX data processor 810 are carried out.

On the forward link, 882 pairs of business datums of TX data processor and control data are handled (for example: be used for the time adjusting), and data symbol is provided.884 pairs of data symbols of OFDM modulator receive, and itself and frequency pilot sign are carried out multiplexing, carry out the OFDM modulation, and OFDM is provided symbols streams.Can use same or different transmission plan for forward direction and reverse link.For example, the transmission plan shown in Fig. 4 A can be used for reverse link, and the transmission plan shown in Fig. 4 B can be used for forward link.886 pairs of OFDM symbols streams of transmitter unit receive and handle, and generate forward link signal, send it to user terminal via antenna 852.

At user terminal 120x place, 824 pairs of forward link signals from base station 110x of antenna receive, and receiver unit 842 handles it, with the chip that obtains to receive.The chip of 844 pairs of receptions of ofdm demodulator is handled, and detected data symbol is offered RX data processor 846.846 pairs of detected data symbols of RX data processor are handled, with the business datum of recovering to be sent by base station 110x.

Controller 830 and 870 is commanded the operation at user terminal 120x and base station 110x place respectively.Memory cell 832 and 872 is storage control 830 and 870 employed program code and data respectively. Time control unit 828 and 868 is carried out the time synchronized function that can be used for user terminal 120x and base station 110x respectively.Controller 830 and 870 can also be realized time control unit 828 and 868 respectively, and can be respectively terminal 120x and base station 110x time of implementation synchronizing function.

Fig. 9 shows at the ofdm demodulator 856 at base station 110x place and the embodiment of time control unit 868.In ofdm demodulator 856, cp removal unit 912 removes the Cyclic Prefix that is attached on each OFDM symbol based on the measurement time of advent that is provided by time control unit 868.Then, FFT unit 914 usefulness N point FFT transform to frequency domain with N chip that receives of the figure shift of each reception, obtain N receiving symbol of N subband.FFT unit 914 offers time control unit 868 with the frequency pilot sign that receives, and the data symbol that receives is offered data detector 916.Data detector 916 usefulness frequency responses are estimated the data symbol that receives is detected (for example: matched filtering or equilibrium), and the data symbol that detects is offered RX data processor 858.

The time control loop of 868 pairs of reverse links from user terminal 120x to base station 110x of time control unit carries out receiver side to be handled.The time of advent, measuring unit 920 obtained the frequency pilot sign that receives, and to measuring the time of advent from the transmission of user terminal 120x.In unit 920, pilot processor 922 removes the modulation on each reception set of pilot symbols, and estimates for the reverse link that is used for user terminal 120x provides frequency response.The frequency response of 924 pairs of different set of pilot symbols of spectral estimator (for example: send in different hop periods) is estimated to carry out Frequency Estimation, and provides the measurement time of advent from the transmission of user terminal 120x.Adder 930 deducts from expected approach time measures the time of advent, and time error is provided.Controller 870 can be based upon definite expected approach time of time that user terminal 120x is dispatched.Though do not illustrate in Fig. 9, low pass filter can carry out filtering to time error, and filtered time error is provided.Multiplier 932 will multiply each other with the TCL gain from the time error of adder 930 the filtered time error of low pass filter (perhaps from), and the time error behind the convergent-divergent is provided.

Time error behind 940 pairs of convergent-divergents of preprocessor receives, and is to regulate the user terminal 120x rise time.Preprocessor 940 can be carried out as described above such as any technology in the technology such as infiltration, wait-affirmation.Time is regulated indicating user terminal 120x with its timing advance or delay, and makes it be transmitted in expected approach time and arrives base station 110x.

942 pairs of channel detectors such as SNR, reverse link from the transmission that user terminal 120x received are that channel condition such as static or fast-changing detects.TCL gain selector 944 receives detected channel condition from detector 942, and slave controller 870 is received as the selected operational mode of time control loop (for example: catch or tracing mode), and/or receive other input.944 pairs of TCL gains of gain selector are regulated, to realize the desired performance of time control loop.

If desired, can be to realize being used for the time control loop of forward link with the similar mode of mode that is used for reverse link mentioned above.For this time control loop, for example, user terminal 120x uses spectrum estimation to measuring the time of advent of the transmission that receives from base station 110x.Then, user terminal was regulated based on the time that the measurement time of advent and the expected approach time of this forward link transmissions generates this forward link.The base station is regularly regulated the transmission that it is used for user terminal, makes forward link transmissions arrive user terminal in expected approach time.

Can realize Time synchronization technique as described herein by variety of way.For example, can make up these technology that realizes with hardware, software or its.Realize for hardware, can be at one or more application-specific integrated circuit (ASIC)s (ASIC), digital signal processor (DSP), digital signal processor spare (DSPD), programmable logic device (PLD), field programmable gate array (FPGA), processor, controller, microcontroller, microprocessor, other is designed to realize that realization in the electronic unit of function as described herein or its combination is used for carrying out at the receiver place processing unit of time synchronized.Also can in one or more ASIC, DSP etc., realize being used for carrying out the processing unit of time synchronized at the transmitter place.

Realize for software, can realize Time synchronization technique with the module (for example: program, function etc.) of carrying out function as described herein.(for example: the memory cell 872 among Fig. 8), and pass through processor (for example, controller 870) and carry out this software code software code can be stored in memory cell.Can be in processor inside or the outside memory cell of realizing of processor.

Any technical staff of this area provides the above-mentioned explanation of disclosed embodiment, so that can both realize or use the present invention.The various modifications of these embodiment will be conspicuous to one skilled in the art, and under the situation that does not break away from the spirit or scope of the present invention, the General Principle that defines can be applied to other embodiment here.Therefore, the present invention is not the embodiment shown in will being restricted to here, but will meet and principle disclosed herein and the corresponding to wide region of novel feature.

Claims (42)

1, a kind of method of carrying out time synchronized in communication system comprises:

Use spectrum estimation to measure the time of advent of the transmission that receives via communication channel;

Determine the described measurement time of advent of described transmission and the time error between the expected approach time; And

Regulate based on the described time error rise time.

2, the method for claim 1, wherein the step of measuring the described time of advent of described transmission is comprised:

Obtain the channel estimating of described communication channel; And

Described channel estimating is carried out spectrum estimation, to obtain the described measurement time of advent of described transmission.

3, method as claimed in claim 2, wherein, the step that obtains the described channel estimating of described communication channel comprises:

The a plurality of frequency responses that obtain a plurality of sets of frequency subbands estimate that wherein, described channel estimating comprises described a plurality of frequency response estimation.

4, method as claimed in claim 2, wherein, the step of described channel estimating being carried out spectrum estimation comprises:

Determine the main frequency component in the described channel estimating; And

Derive described measurement time of advent based on described main frequency component.

5, the method for claim 1 also comprises:

With gain described time error is carried out convergent-divergent, and wherein, generate described time adjusting based on the time error behind the described convergent-divergent.

6, method as claimed in claim 5 also comprises:

At least one condition based on described communication channel is regulated described gain.

7, method as claimed in claim 5 also comprises:

Based on the operational mode of from a plurality of operational modes that comprise acquisition mode and tracing mode, selecting described gain is regulated.

8, method as claimed in claim 5 also comprises:

Displacement speed in the channel profile of determining to obtain according to described spectrum estimation; And

Based on the described displacement speed in the described channel profile described gain is regulated.

9, the method for claim 1, wherein generating the step that described time regulates based on described time error comprises:

Described time error is carried out filtering; And

Deriving the described time based on described filtered time error regulates.

10, the method for claim 1 also comprises:

Described time adjusting is limited in the value of preset range.

11, the method for claim 1, wherein generating the step that described time regulates based on described time error comprises:

Determine the amplitude of described time error;

If the described amplitude of described time error in preset range, just generates described time adjusting based on first function; And

If the described amplitude of described time error outside described preset range, just generates described time adjusting based on second function.

12, a kind of device that is used for carrying out in communication system time synchronized comprises:

Measuring unit is used to use spectrum estimation to measure the time of advent of the transmission that receives via communication channel;

Adder is used to provide the described measurement time of advent of described transmission and the time error between the expected approach time; And

Preprocessor is used for regulating based on the described time error rise time.

13, device as claimed in claim 12, wherein, described measuring unit comprises:

Pilot processor is used to receive the pilot tone that sends via described communication channel, and derives the channel estimating of described communication channel; And

Spectral estimator is used for described channel estimating is carried out spectrum estimation, to obtain the described measurement time of advent of described transmission.

14, device as claimed in claim 13, wherein, described pilot processor derives a plurality of frequency responses of a plurality of sets of frequency subbands to be estimated, and wherein, described channel estimating comprises described a plurality of frequency response estimation.

15, device as claimed in claim 14, wherein, described pilot processor receives the frequency pilot sign on each of described a plurality of sets of frequency subbands, and estimates based on the frequency response that the frequency pilot sign of the described reception of each sets of frequency subbands is derived this sets of frequency subbands.

16, device as claimed in claim 14, wherein, each subband set comprises the subclass of whole N subbands in the described system, wherein, N is the integer greater than 1.

17, device as claimed in claim 14, wherein, each subband set comprises M continuous subband in the described system, wherein, M is the integer greater than 1.

18, device as claimed in claim 14, wherein, each subband set is included in an equally distributed M subband on whole N the subbands in the described system, and wherein, M and N are the integers greater than 1, and M is less than N.

19, device as claimed in claim 14, wherein, described a plurality of subband set are to be determined by the pseudo random sequence that is used for frequency hopping.

20, device as claimed in claim 13, wherein, described pilot processor receives the broadband pilots that sends via described communication channel, and derives described channel estimating based on described broadband pilots.

21, device as claimed in claim 13, wherein, described spectral estimator is determined the main frequency component in the described channel estimating, and derives described measurement time of advent based on described main frequency component.

22, device as claimed in claim 13, wherein, described spectral estimator uses Multiple Signal Classification (MUSIC) technology, periodogram technology, Prony estimator or Pisarenko harmonic wave decomposition technique that described channel estimating is carried out spectrum estimation.

23, device as claimed in claim 12 also comprises:

Multiplier is used for utilizing gain that described time error is carried out convergent-divergent, and wherein, and the time error of described preprocessor after based on described convergent-divergent generates the described time and regulate.

24, device as claimed in claim 23 wherein, is regulated described gain based at least one condition of described communication channel.

25, device as claimed in claim 23 wherein, is regulated described gain based on the signal to noise ratio (snr) of described transmission.

26, device as claimed in claim 23 also comprises:

Controller is used for selecting an operational mode from a plurality of operational modes, and based on the operational mode of described selection described gain is regulated.

27, device as claimed in claim 12 also comprises:

Filter carries out filtering to described time error.

28, device as claimed in claim 12, wherein, described preprocessor is regulated the described time and is limited in the value of preset range.

29, device as claimed in claim 12, wherein, described preprocessor is determined the amplitude of described time error; If the described amplitude of described time error in preset range, just generates described time adjusting based on first function; And if the described amplitude of described time error just generates described time adjusting based on second function outside described preset range.

30, device as claimed in claim 12, wherein, described preprocessor generates described time adjusting based on described time error and according to the first-order loop that is used for described time synchronized.

31, device as claimed in claim 12, wherein, described preprocessor generates described time adjusting based on described time error and according to the second-order loop that is used for described time synchronized.

32, device as claimed in claim 12, wherein, described communication system is utilized OFDM (OFDM).

33, device as claimed in claim 12, wherein, described communication system is OFDM (OFDMA) system.

34, a kind of device that is used for carrying out in communication system time synchronized comprises:

Be used to use spectrum estimation to measure the module of the time of advent of the transmission that receives via communication channel;

Be used for determining the described measurement time of advent of described transmission and the module of the time error between the expected approach time; And

Be used for module based on the adjusting of described time error rise time.

35, device as claimed in claim 34, wherein, the described module that is used to measure the described time of advent of described transmission comprises:

Be used to obtain the module of the channel estimating of described communication channel; And

Be used for the enterprising line frequency spectrum of described channel estimating is estimated, to obtain the described module of measuring the time of advent of described transmission.

36, device as claimed in claim 35, wherein, the described module that is used to obtain the described channel estimating of described communication channel comprises:

Be used to obtain the module that a plurality of frequency responses of a plurality of sets of frequency subbands are estimated, wherein, described channel estimating comprises that described a plurality of frequency response estimates.

37, device as claimed in claim 35, wherein, the described module that is used for described channel estimating is carried out spectrum estimation comprises:

The module that is used for the main frequency component of definite described channel estimating; And

Be used for deriving the described measurement module of the time of advent based on described main frequency component.

38, device as claimed in claim 34 also comprises:

Be used to utilize gain that described time error is carried out the module of convergent-divergent, and wherein, generate described time adjusting based on the time error behind the described convergent-divergent.

39, device as claimed in claim 34 also comprises:

Be used for described time is regulated module in the value that is limited in preset range.

40, a kind of measurement in communication system arrives time method, comprising:

Obtain the channel estimating of communication channel;

Described channel estimating is carried out spectrum estimation, to determine the main frequency component in the described channel estimating; And

Measure the time of advent based on described main frequency component derivation.

41, method as claimed in claim 40, wherein, the step that obtains the described channel estimating of described communication channel comprises:

The a plurality of frequency responses that obtain a plurality of sets of frequency subbands are estimated, and wherein, described channel estimating comprises described a plurality of frequency response estimation.

42, a kind of device of measuring the time of advent in communication system comprises:

Be used to obtain the module of the channel estimating of communication channel;

Be used for described channel estimating is carried out spectrum estimation, to determine the module of the main frequency component in the described channel estimating; And

Be used for deriving the module of measuring the time of advent based on described main frequency component.

Images