WO1991007831A1 - Procede servant a determiner des points d'echantillonage dans le temps - Google Patents

Procede servant a determiner des points d'echantillonage dans le temps Download PDF

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Publication number
WO1991007831A1
WO1991007831A1 PCT/SE1990/000697 SE9000697W WO9107831A1 WO 1991007831 A1 WO1991007831 A1 WO 1991007831A1 SE 9000697 W SE9000697 W SE 9000697W WO 9107831 A1 WO9107831 A1 WO 9107831A1
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WO
WIPO (PCT)
Prior art keywords
sampling time
symbol
time points
time point
channel
Prior art date
Application number
PCT/SE1990/000697
Other languages
English (en)
Inventor
Lars Gustav Larsson
Original Assignee
Telefonaktiebolaget Lm Ericsson
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget Lm Ericsson filed Critical Telefonaktiebolaget Lm Ericsson
Priority to KR1019910700725A priority Critical patent/KR970007612B1/ko
Priority to CA002044599A priority patent/CA2044599C/fr
Publication of WO1991007831A1 publication Critical patent/WO1991007831A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/0054—Detection of the synchronisation error by features other than the received signal transition
    • 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

Definitions

  • the present invention relates to a method of determining sampling time point when transmitting symbol sequences with recurrent synchronization sequences, wherein the symbol sequences are transmitted as analog signals over a channel and are liable to be subjected to disturbances during said transmission, said method comprising the steps of:
  • the trans ⁇ mitted, unknown information can be interpreted by the receiver with the aid of the impulse response, and can be converted to an acoustic signal for instance, through a plurality of signal processing stages.
  • a further example of the difficulties ex ⁇ perienced with signal transition is one of controlling the re- ceiver frequency in time with the transmitter frequency. This difficulty has been recognized and a number of well-known methods are found for controlling the frequency of the receiver.
  • One problem, on the other hand, which would not appear to have awakened any particular interest is that of optimally utilizing the signal strength of thetransmitted signal during the aforesaid transmission of digital information. It should be observed in this respect that in the case of multipath propagation a transmitted signal can be refound at several mutually different receiver time points. Despite research, both in the patent literature and in other sources, no publication has been foundwhich deals with this problem.
  • the present invention is based on the concept of optimally utilizing the signal strength of a transmitted signal for the purpose of simplifying the signal processing necessary in a receiver. This optimization is achieved by selecting a time point for sampling the tranmitted symbols. This choice is based on a comparison of the energy content of different parts of the channel impulse response.
  • the invention has the characterizing features set forth in the accompanying Claims.
  • Figure 1 is a block schematic illustrating a part of a mobile telephony system
  • Figure 2 illustrates time slots for time-shared transmission of information
  • Figure 3 illustrates symbol sequences transmitted in a time- shared time slot
  • Figure 4 illustrates a complex number plan with symbol values
  • Figure 5 is a block schematic illustrating a channel estimation filter
  • Figure 6 is a diagram with an impulse response for the trans ⁇ mission channel.
  • FIG. 1 schematically illustrates a radio transmission system.
  • Signal processing, for instance channel coding, of the information to be transmitted is effected in a unit 1 and the information is sent to a digital/analog converter D/A in the form of digital signals.
  • the converter sends analog signals to a transmitting radio unit RA1, which transmits the signals over a channel to a receiving radio unit RA2.
  • This unit sends the received signals to an analog/digital converter A/D, in which sampling of the signal takes place at a relatively high rate. Sampling takes place at regular intervals at signal sampling time points, the number of which is generally referenced n, so as to obtain a sampled signal S(n). That part of the radio transmission system described hitherto is well known to the person skilled in this art.
  • Synchro ⁇ nization, channel correlation and sampling of the signal S(n) takes place in a correlation-and-synchronization circuit KS, as described in more detail hereinafter.
  • the actual method in which a sampling time point is selected during a sampling operation is the object of the present invention.
  • the sampling signals are sent from the circuit KS for further signal processing, in the case of the illustrated embodiment to an equalizer V, which produces estimated symbols U.
  • the inventive method of selecting sampling time points provides improved signal processing in the equalizer V.
  • the aforedescribed radio transmission system may, for instance, form a part of a time-shared mobile telephony system. Subscribers in this system are regularly assigned recurring time slots 1,— —, P as illustrated in Figure 2, in which T signifies time.
  • T signifies time.
  • One of the subscribers has been assigned the time slot numbered H and the symbol sequences designated SSI, SS2, SS3, , aretransmitted inthis time slot.
  • Each symbol sequence includes a synchronization sequence SY and a data sequence D and together take up the length of a time slot designated TO in Figure 3.
  • the transmitted signals maybemodulated inaccordancewithQPSK-modulation, as illusrated in Figure 4, for instance.
  • the impulse response of the channel is determined in a known manner for each signal sequence. This is achieved by correlating the known synchronization sequence SY in the receiver with the received, sampled values S(n) in the synchronization sequence. Correlation is carried out in a filter, as illustrated in Figure 5.
  • the filter has delay units 2, filter coefficients 3 and summators 4.
  • the filter coefficients have the values SY O-. SYJ ⁇ .—1.
  • the received, sampled synchronization word S(n) is delayed in the delay unit 2, so as to subsequently obtain signals S(n-N) S(n-(K-1)N) which are stepwise delayed by one symbol sampling interval.
  • the delayed signals are multiplied with their respective coefficients and summated inthe summator 4. Subsequent to dividing with the value K in a circuit 5, the values
  • Figure 6 illustrates the sampled impulse response obtained in the aforedescribed manner for the synchronization sequence in the
  • T designates the time and C generally designates the energy for the discrete correlation values of the impulse response, -these values being marked with columns at the signal sampling time point n.
  • the impulse response has a length of L+M x N sample, which have been numbered from 0 to L-l+M x N in the Figure.
  • N designates the number of signal sampling time points n for each symbol and according to the illustrative example N is equal to 2.
  • the length of a channel estimate for the equilizer V in symbol times Ts is designated M, and in the case of the illustrative example, M is equal to 3.
  • the length M x Ts of the channel estimate is determined by the magnitude of the time dispersion possessed by the channel, so that the equilizer V will be able to equalize dispersions which range up to M x Ts.
  • sampling of the signal S(n) takes place in the correlation-and-synchronization circuit KS.
  • This sampling takes place in step with the symbol timing at symbol sampling time points having an interval of one symbol time Ts between two mutually adjacent samples.
  • the sampling time point can also be calculated in the following alternative manner. That signal sampling time point of the signal sampling time points n in which the impulse response has maximum amplitude C 2 ma ⁇ ( n ) is sought and constitutes the selected sampling timepoint.
  • the comparisonvalue in this sampling time point can be expressed with the simple relationship
  • I I value E ke (n) and the comparison value E t (n) are calculated in accordance with the aforegoing. The largest of these values E is selected and the corresponding signal sampling time point n constitutes the selected sampling time point.
  • the aforedescribed inventive method of selecting a sampling time point for one of the signal sequences according to the example SSI has the advantage of simplifying the following signal processing step in, for instance, the equalizer V. It is possible, however, that the transmitted signal of the Figure 1 illustration has been subjected to fading, i.e. the signal strength has fallen radically over a short time interval due to signal interference. If the fadingoccurs duringthe synchronization sequence SY, the selected channel estimate and the selected sampling time point will not be representative of the remainder of the symbol sequence. This weakness is particularly noticeable in transmission systems which have long symbol sequences extending over several milliseconds.
  • This weakness is counteracted in accordance with the present invention by calculating an estimated value n ⁇ st (j) f° r the sampling time point iteratively.
  • the maximum energy value, for instance and the corresponding sampling time point n beauma v x is subsequently calculated for the sequences SSI, SS2, SS3 .
  • the estimated sampling time point n t (j) will lie between two signal sampling time points n and the signal sampling time point which lies nearest *n es ⁇ .(j) i selected as the sampling time point.
  • time points of the receiver are calculated in relation to a synchronizatio time point T of a frame clock, which is controlled in a known manner.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Time-Division Multiplex Systems (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Des séquences de symboles présentant des séquences de synchronisation sont transmises sur un canal radio. Les signaux reçus sont échantillonés à intervalles aux points d'échantillonage de signaux dans le temps (n) et une réponse de canal (C2) est obtenue par corrélation. La réponse des impulsions est échantillonée (Ts) pendant une période (M x N) qui correspond à la dispersion dans le temps du canal. Pour des échantillons séparés ayant des points de départ séparés (n), on obtient des estimations de canal (n = 0, 2, 4, 6, N = 1, 3, 5, 7...) dont on calcule les valeurs d'énergie, et on sélectionne l'estimation (n = 8, 10, 12, 14) ayant le plus d'énergie. On sélectionne le premier point dans le temps (n = 8) de cette estimation comme point d'échantillonage dans le temps pour la séquence des symboles. Dans une variante, on sélectionne le point d'échantillonage de signaux dans le temps (n = 9) ayant la valeur d'énergie maximale (C2 max). En comparant ces valeurs d'énergie, on peut sélectionner l'un ou l'autre de ces points d'échantillonage de signaux dans le temps (n = 8, n = 9) comme point d'échantillonage dans le temps pour la séquence des symboles. Pour les séquences consécutives, on calcule une valeur moyenne relative aux points d'échantillonage dans le temps. Un maximum d'énergie pour les symboles reçus et une simplification du traitement des signaux sont ainsi obtenues.
PCT/SE1990/000697 1989-11-15 1990-10-26 Procede servant a determiner des points d'echantillonage dans le temps WO1991007831A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
KR1019910700725A KR970007612B1 (ko) 1989-11-15 1990-10-26 표본화(標本化) 타임포인트의 결정방법
CA002044599A CA2044599C (fr) 1989-11-15 1990-10-26 Methode de determination des temps d'echantillonnage

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8903842A SE465005B (sv) 1989-11-15 1989-11-15 Foerfarande att bestaemma samplingstidpunkt
SE8903842-6 1989-11-15

Publications (1)

Publication Number Publication Date
WO1991007831A1 true WO1991007831A1 (fr) 1991-05-30

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1990/000697 WO1991007831A1 (fr) 1989-11-15 1990-10-26 Procede servant a determiner des points d'echantillonage dans le temps

Country Status (7)

Country Link
JP (1) JP2994748B2 (fr)
KR (1) KR970007612B1 (fr)
AU (1) AU628238B2 (fr)
CA (1) CA2044599C (fr)
NZ (1) NZ235749A (fr)
SE (1) SE465005B (fr)
WO (1) WO1991007831A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5365549A (en) * 1993-05-24 1994-11-15 Motorola, Inc. Complex signal correlator and method therefor
US5465412A (en) * 1993-05-19 1995-11-07 Motorola, Inc. Apparatus and method for determining a point in time for detecting a sampled signal in a receiver
EP0711049A1 (fr) * 1994-11-07 1996-05-08 Alcatel Telspace Procédé de détection de symboles de référence pour récepteur de données numériques
WO1998000992A2 (fr) * 1996-06-28 1998-01-08 Harris Corporation Ameliorations concernant un procede et un appareil permettant de determiner la synchronisation des symboles dans un systeme de transmission sans fil, utilisant un canal de commande reutilisable et reduisant la puissance
WO1998027684A1 (fr) * 1996-12-18 1998-06-25 Ericsson Inc. Systeme et procede de syncrhonisation temps et frequence d'un systeme de radiocommunications
FR2773029A1 (fr) * 1997-12-23 1999-06-25 Telecommunications Sa Procede de synchronisation d'un recepteur sur des donnees numeriques transmises par paquets
WO2000018158A1 (fr) * 1998-09-24 2000-03-30 Ericsson Inc. Recepteur radio a balayage pour systeme de communication sans fil
EP1094631A1 (fr) * 1999-10-20 2001-04-25 Koninklijke Philips Electronics N.V. Recherche de l'instant d'échantillonnage optimal dans un système de transmissions par paquets TDMA

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993026106A1 (fr) * 1992-06-18 1993-12-23 Oki Electric Industry Co., Ltd. Dispositif et procede d'estimation de sequence probabiliste maximale

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4768208A (en) * 1987-03-09 1988-08-30 Motorola, Inc. Mid-symbol sampling timing estimator
US4823382A (en) * 1986-10-01 1989-04-18 Racal Data Communications Inc. Echo canceller with dynamically positioned adaptive filter taps

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4823382A (en) * 1986-10-01 1989-04-18 Racal Data Communications Inc. Echo canceller with dynamically positioned adaptive filter taps
US4768208A (en) * 1987-03-09 1988-08-30 Motorola, Inc. Mid-symbol sampling timing estimator

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
IEE PROCEEDINGS, Vol. 131, No. 5, August 1984, A.P. CLARK et al., "Adaptive Adjustment of Receiver for Distorted Digital Signals", pages 526-536. *
SIGNAL PROCESSING, 2, 1980, A.P. CLARK et al., "Estimation of the Sampled Impulse-Response of a Channel", pages 39-53. *

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5465412A (en) * 1993-05-19 1995-11-07 Motorola, Inc. Apparatus and method for determining a point in time for detecting a sampled signal in a receiver
US5365549A (en) * 1993-05-24 1994-11-15 Motorola, Inc. Complex signal correlator and method therefor
EP0711049A1 (fr) * 1994-11-07 1996-05-08 Alcatel Telspace Procédé de détection de symboles de référence pour récepteur de données numériques
FR2726711A1 (fr) * 1994-11-07 1996-05-10 Alcatel Telspace Procede de detection de symboles de reference pour recepteur de donnees numeriques
US5732114A (en) * 1994-11-07 1998-03-24 Alcatel Telspace Method of detecting reference symbols for a digital data receiver
WO1998000992A3 (fr) * 1996-06-28 1998-06-25 Harris Corp Ameliorations concernant un procede et un appareil permettant de determiner la synchronisation des symboles dans un systeme de transmission sans fil, utilisant un canal de commande reutilisable et reduisant la puissance
WO1998000992A2 (fr) * 1996-06-28 1998-01-08 Harris Corporation Ameliorations concernant un procede et un appareil permettant de determiner la synchronisation des symboles dans un systeme de transmission sans fil, utilisant un canal de commande reutilisable et reduisant la puissance
WO1998027684A1 (fr) * 1996-12-18 1998-06-25 Ericsson Inc. Systeme et procede de syncrhonisation temps et frequence d'un systeme de radiocommunications
US6023477A (en) * 1996-12-18 2000-02-08 Ericsson Inc. System and method of time and frequency synchronization in a radiocommunication system
FR2773029A1 (fr) * 1997-12-23 1999-06-25 Telecommunications Sa Procede de synchronisation d'un recepteur sur des donnees numeriques transmises par paquets
EP0926858A1 (fr) * 1997-12-23 1999-06-30 Sagem Sa Procédé de synchronisation d'un récepteur sur des données numériques transmises par paquets
WO2000018158A1 (fr) * 1998-09-24 2000-03-30 Ericsson Inc. Recepteur radio a balayage pour systeme de communication sans fil
US6453156B1 (en) 1998-09-24 2002-09-17 Ericsson Inc. Scanning radio receiver for a wireless communication system
EP1094631A1 (fr) * 1999-10-20 2001-04-25 Koninklijke Philips Electronics N.V. Recherche de l'instant d'échantillonnage optimal dans un système de transmissions par paquets TDMA
US6674822B1 (en) 1999-10-20 2004-01-06 Koninklijke Philips Electronics N.V. Searching the optimal sampling instant in a TDMA packet transmission system

Also Published As

Publication number Publication date
JP2994748B2 (ja) 1999-12-27
KR920702119A (ko) 1992-08-12
KR970007612B1 (ko) 1997-05-13
JPH04503143A (ja) 1992-06-04
SE465005B (sv) 1991-07-08
CA2044599A1 (fr) 1991-05-16
SE8903842D0 (sv) 1989-11-15
AU6741590A (en) 1991-06-13
AU628238B2 (en) 1992-09-10
SE8903842L (sv) 1991-05-16
NZ235749A (en) 1993-01-27
CA2044599C (fr) 2001-01-09

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