WO1999053645A1 - Procede de synchronisation fine sur un signal recu d'un canal de transmission - Google Patents
Procede de synchronisation fine sur un signal recu d'un canal de transmission Download PDFInfo
- Publication number
- WO1999053645A1 WO1999053645A1 PCT/FR1999/000835 FR9900835W WO9953645A1 WO 1999053645 A1 WO1999053645 A1 WO 1999053645A1 FR 9900835 W FR9900835 W FR 9900835W WO 9953645 A1 WO9953645 A1 WO 9953645A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- transmission channel
- characterization
- eigenvalues
- matrix
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/04—Speed or phase control by synchronisation signals
- H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
- H04L7/042—Detectors therefor, e.g. correlators, state machines
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
- H04L7/0334—Processing of samples having at least three levels, e.g. soft decisions
Definitions
- the present invention relates to a method of fine synchronization on a reception signal corresponding to a reference signal transmitted in a transmission channel.
- a transmitter transmits a reference signal in a transmission channel intended for a receiver.
- One of the first operations that the receiver must perform is synchronization on the reception signal.
- This problem is well known to those skilled in the art and it is therefore not necessary to recall here the different techniques which are used to obtain this synchronization.
- the signals are digital, it is customary to evaluate the synchronization difference by means of a time unit, the bit time, which is the time difference separating two successive bits of a signal.
- bit time which is the time difference separating two successive bits of a signal.
- This precision may prove to be insufficient in certain cases.
- it is synchronization which gives the signal journey time in the transmission channel or, in other words, the transmission time between the transmitter and the receiver.
- This is important because, in a duplex radiocommunication system where a base station is in communication with a terminal, each piece of equipment being provided with a transceiver, the terminal must operate so that the signal it transmits arrives at a precise instant with reference to the time base of the base station. To do this, it is of course necessary for the terminal to know the time it takes for this signal to reach the base station. On the other hand, this transmission time directly reflects the distance between the transmitter and the receiver.
- the present invention thus relates to a synchronization method whose precision is much greater than the bit time.
- the fine synchronization method on a reception signal corresponding to a reference signal transmitted in a transmission channel comprises the following steps: - selection of a source signal producing a characterization signal following its passage through the transmission channel,
- the time increment adopted for the calculation of the correlation function is chosen to be sufficiently small, in any case much less than a bit time, this method makes it possible to obtain very good precision.
- the number of these dominant eigenvalues is predetermined. Typically, this number represents around 20 to 30% of the dimension of the characterization matrix.
- the ratio of the sum of the dominant eigenvalues to the sum of all the eigenvalues is greater than or equal to a predetermined number.
- the number chosen will often be greater than 90%, 95% for example.
- the method further comprising a step of estimating the additive noise in the transmission channel, the dominant eigenvalues are such that their sum is less than or equal to the sum of all the eigenvalues minus the additive noise.
- the estimation of the additive noise is carried out by normalizing the instantaneous noise which is evaluated by means of the reception signal, the reference signal and an estimation of the impulse response of the transmission channel.
- the characterization matrix results from a smoothing operation.
- the characterization signal is an estimate of the impulse response of the transmission channel.
- the characterization signal is the reception signal.
- FIG. 1 a first alternative embodiment of the invention
- the receiver has already acquired coarse synchronization on the reception signal, of the order of bit time, using any of the solutions available.
- This reception signal corresponds to a reference signal produced by the transmitter and known to the receiver.
- This reference signal can be known a priori, that is to say that it is a learning sequence formed from identified symbols. It can also be known a posteriori by means of techniques generically referred to as the blind survey. In this case, during the synchronization procedure, the receiver regenerates the series of symbols forming the reference signal from the reception signal.
- a source signal is selected which, produced by the transmitter, gives to the receiver, after transmission in the channel, a characterization signal.
- this characterization signal is the reception signal itself.
- this is not always the optimal solution as regards the complexity and performance of the process of the invention.
- Another solution consists in retaining a modulated pulse as the source signal, the characterization signal then becoming the impulse response of the transmission channel.
- the GSM digital cellular radio system uses a learning sequence of 26 symbols, the impulse response being generally estimated with 5 coefficients since it is admitted that the dispersion of the channel is worth 4.
- the reception signal has a maximum dimension of 22 which is significantly larger than that of the impulse response.
- this technique uses a measurement matrix A constructed at from the training sequence TS of length n.
- This matrix includes (n-d) rows and (d + 1) columns, d representing the dispersion of the channel.
- the element appearing in the ith line and in the jth column is the (d + i- j) th symbol of the training sequence, that is to note a ⁇ the th symbol of a TS sequence of 26 symbols:
- the learning sequence is chosen such that the matrix A ⁇ A is invertible where the operator represents the transposition.
- the reception signal S the first four symbols S Q to S3 are not taken into account because these also depend on unknown symbols transmitted before the learning sequence, since the dispersion of the channel is worth 4.
- the reception signal By an abuse of language one will henceforth define the reception signal as a vector S having for components the symbols received, S4, S5, s_, ..., S25. Consequently, the estimation of the impulse response X takes the following form:
- the next step of the method of the invention consists in establishing a statistic of this impulse response.
- statistic we mean a set of data reflecting the average value of this response over an analysis period.
- a first example of smoothing consists in carrying out the average of the matrix XX n over the analysis period assumed to include m learning sequences:
- the operator .h represents the Hermitian transformation or complex conjugation transposition.
- a second smoothing example consists in updating, after receipt of the ith training sequence, the smoothing matrix Li_ ⁇ (XX n ) obtained in the (il) th training sequence by means of a multiplicative coefficient ⁇ , this factor being generally known as smoothing forget factor and being between 0 and 1:
- Li (XX h ) ⁇ XiXi h + (l- ⁇ ) Li _! (XX h )
- Initialization can be done by any means, in particular by means of the first estimate X obtained or by an average obtained as above for a low number of training sequences.
- the smoothing matrix L (XX n ) which is in fact a statistical characterization matrix, will henceforth be denoted L.
- the method then comprises a step of searching for the pairs (eigenvalue, eigenvector) of the characterization matrix.
- the eigenvalues ⁇ ⁇ are now classified, in descending order. Indeed, the sum of these values corresponds to the energy of the characterization signal X composed partly of a useful signal which is the image of the source signal and partly of the additive noise N of the transmission channel. It follows that the dominant eigenvalues, those which are the highest, represent the useful signal, while the weakest eigenvalues represent the noise.
- the method consists in retaining a predetermined number of dominant eigenvalues. For example, for an impulse response to
- the useful signal has an energy which is a predetermined fraction f of the energy of the characterization signal.
- the fraction f can be set a priori, to a value of 95% for example. This fraction can also be derived the signal-to-noise ratio of the reception signal obtained elsewhere.
- the additive noise N is estimated directly from the reception signal and from the measurement matrix A.
- N Q the noise vector affecting the reception signal
- the dominant eigenvalues are therefore obtained from a direct estimate of the noise.
- the next step of the method consists in calculating the correlation function of the source signal with the sum of the eigenvectors VJ_ associated with the dominant eigenvalues ⁇ j_.
- the source signal is oversampled with respect to the bit time and it will therefore be noted g (t) where t which represents the time is a discrete variable whose quantization step is, for example, 1/32 bit time. It is represented by a vector of the same dimension as the characterization signal, ie 5 in the example adopted.
- the point appearing between the source signal g (t) and the eigenvector v ⁇ classically represents the scalar product.
- the last step of the process consists in finding the value t 0 of t closest to zero which corresponds to the first relative maximum of the correlation function c (t).
- the characterization signal is the reception signal S, so that the source signal is now the reference signal, ie in the case of GSM, the modulated TS training sequence GMSK (for "Gaussian Minimum Shift Keying").
- GMSK for "Gaussian Minimum Shift Keying"
- the statistics of the characterization signal are therefore estimated by means of a characterization matrix which is now obtained by smoothing the various occurrences of the reception signal S.
- smoothing is considered in a very general sense.
- the characterization matrix L therefore takes the following form: h 1 m V.
- Li (SS n ) ⁇ S S n + (l- ⁇ ) Li_ ⁇ (SS n )
- the invention can thus be implemented in different ways, the essential point being to have a source signal and the result of its transmission, namely the characterization signal.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
- Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP99914586A EP1084547A1 (fr) | 1998-04-10 | 1999-04-09 | Procede de synchronisation fine sur un signal recu d'un canal de transmission |
CA002328293A CA2328293A1 (fr) | 1998-04-10 | 1999-04-09 | Procede de synchronisation fine sur un signal recu d'un canal de transmission |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9804782A FR2777408B1 (fr) | 1998-04-10 | 1998-04-10 | Procede de synchronisation fine sur un signal recu d'un canal de transmission |
FR98/04782 | 1998-04-10 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1999053645A1 true WO1999053645A1 (fr) | 1999-10-21 |
WO1999053645A8 WO1999053645A8 (fr) | 2001-03-08 |
Family
ID=9525334
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FR1999/000835 WO1999053645A1 (fr) | 1998-04-10 | 1999-04-09 | Procede de synchronisation fine sur un signal recu d'un canal de transmission |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1084547A1 (fr) |
CN (1) | CN1300488A (fr) |
CA (1) | CA2328293A1 (fr) |
FR (1) | FR2777408B1 (fr) |
WO (1) | WO1999053645A1 (fr) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006510321A (ja) * | 2002-12-22 | 2006-03-23 | フラクタス・ソシエダッド・アノニマ | 移動通信デバイス用のマルチバンド・モノポール・アンテナ |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2857102B1 (fr) | 2003-07-04 | 2007-06-15 | Nortel Networks Ltd | Procede de mesure de l'instant d'arrivee d'un signal radio recu, dispositif de mesure et dispositif de localisation d'une station mobile pour la mise en oeuvre du procede |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5001747A (en) * | 1990-01-22 | 1991-03-19 | Racal Data Communications Inc. | Frequency offset estimator for data modem |
FR2696604A1 (fr) * | 1992-10-07 | 1994-04-08 | Alcatel Radiotelephone | Dispositif d'estimation d'un canal de transmission. |
EP0802656A2 (fr) * | 1996-04-19 | 1997-10-22 | Wavecom | Signal numérique à blocs de référence multiples pour l'estimation de canal, procédés d'estimation de canal et récepteurs correspondants |
-
1998
- 1998-04-10 FR FR9804782A patent/FR2777408B1/fr not_active Expired - Fee Related
-
1999
- 1999-04-09 CA CA002328293A patent/CA2328293A1/fr not_active Abandoned
- 1999-04-09 WO PCT/FR1999/000835 patent/WO1999053645A1/fr not_active Application Discontinuation
- 1999-04-09 CN CN 99806098 patent/CN1300488A/zh active Pending
- 1999-04-09 EP EP99914586A patent/EP1084547A1/fr not_active Withdrawn
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5001747A (en) * | 1990-01-22 | 1991-03-19 | Racal Data Communications Inc. | Frequency offset estimator for data modem |
FR2696604A1 (fr) * | 1992-10-07 | 1994-04-08 | Alcatel Radiotelephone | Dispositif d'estimation d'un canal de transmission. |
EP0802656A2 (fr) * | 1996-04-19 | 1997-10-22 | Wavecom | Signal numérique à blocs de référence multiples pour l'estimation de canal, procédés d'estimation de canal et récepteurs correspondants |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006510321A (ja) * | 2002-12-22 | 2006-03-23 | フラクタス・ソシエダッド・アノニマ | 移動通信デバイス用のマルチバンド・モノポール・アンテナ |
Also Published As
Publication number | Publication date |
---|---|
FR2777408A1 (fr) | 1999-10-15 |
CN1300488A (zh) | 2001-06-20 |
WO1999053645A8 (fr) | 2001-03-08 |
CA2328293A1 (fr) | 1999-10-21 |
EP1084547A1 (fr) | 2001-03-21 |
FR2777408B1 (fr) | 2000-06-23 |
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