[go: up one dir, main page]

WO2000048334A1 - Acquisition de frequence et de base de temps dans un systeme de transmission radio - Google Patents

Acquisition de frequence et de base de temps dans un systeme de transmission radio Download PDF

Info

Publication number
WO2000048334A1
WO2000048334A1 PCT/GB1999/004296 GB9904296W WO0048334A1 WO 2000048334 A1 WO2000048334 A1 WO 2000048334A1 GB 9904296 W GB9904296 W GB 9904296W WO 0048334 A1 WO0048334 A1 WO 0048334A1
Authority
WO
WIPO (PCT)
Prior art keywords
frequency
received signal
offset
timebase
receiver
Prior art date
Application number
PCT/GB1999/004296
Other languages
English (en)
Inventor
Peter William Stephens
Original Assignee
Simoco International Limited
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 Simoco International Limited filed Critical Simoco International Limited
Priority to AU18718/00A priority Critical patent/AU1871800A/en
Publication of WO2000048334A1 publication Critical patent/WO2000048334A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile

Definitions

  • the present invention relates to a method of, and an apparatus for, frequency and timebase acquisition in a radio communications system, and in particular to such a method and apparatus suitable for use in a TDMA (Time Division Multiple Access) radio system, such as the TETRA (TErrestrial Trunked RAdio) system.
  • TDMA Time Division Multiple Access
  • TETRA TErrestrial Trunked RAdio
  • the mobile radio stations In mobile radio systems, the mobile radio stations must be able to synchronise their own frequency and timing to the frequency and timing of the signal transmitted by the base station to allow them to decode the received signals correctly and/or make transmissions correctly to the base station.
  • a mobile station must tune to a received reference frequency and timing is when mobile stations are in direct radio communication without the presence of a base station (e.g. Direct Mode in TETRA) .
  • a base station e.g. Direct Mode in TETRA
  • one mobile station defines the frequency and timing reference and the other mobile station tunes to that reference.
  • the mobile station In a TDMA radio system, the mobile station usually receives signals in discrete bursts (e.g. timeslots or groups of timeslots, usually spaced in time), and each individual burst presents an opportunity for the mobile station to determine and then tune to the received signal frequency and timing.
  • the mobile station will attempt to tune its local frequency and timing references by estimating its frequency and timing offsets or errors relative to the received signal and use those estimates to adjust its local frequency and timing references accordingly. This means that at the next received burst the mobile station should be better tuned to the received signal and therefore ideally able to decode it.
  • the mobile station is not typically able to decode the first received burst, since its local frequency and timing references have not been adjusted at that stage.
  • a method of receiving a radio signal in a radio receiver having local frequency and timebase references comprising: receiving a transmitted radio signal burst; estimating the frequency and/or timebase offset between the received signal and the radio receiver's local frequency and timebase references; and adjusting the received signal burst in frequency and/or timing position on the basis of the estimated frequency and/or timebase offset, respectively.
  • a radio receiver comprising: a local frequency reference; a local timebase reference; means for receiving a transmitted radio signal burst ; means for estimating the frequency and/or timebase offset between the received signal and the radio receiver's local frequency and timebase references; and means for adjusting the received signal burst in frequency and/or timing position on the basis of the estimated frequency and/or timebase offset, respectively.
  • the determined timing and/or frequency offsets for a received signal burst are used to adjust the frequency and/or timing of the received signal burst from which the offsets are determined, rather than simply being used to apply a correction to the receiver's (e.g. mobile station's) local frequency and timebase references.
  • the receiver's e.g. mobile station's
  • subsequent signal processing steps in the receiver can be carried out using a "corrected" version of the received signal burst and so the chances of the receiver being able to correctly decode the received signal burst are increased, such that the receiver may not have to wait for the next burst before it can decode -the received signal correctly.
  • each received burst will usually contain useful information, it is advantageous to be able to decode bursts straight away, rather than having to wait for the next burst. This can therefore permit faster and improved readiness for operation and faster call set-up for a radio receiver in a mobile radio communications system.
  • the frequency and timebase offsets estimated are preferably also used to adjust the local frequency and timebase references of the radio receiver, as is known in the art, so as to tune and lock those references to the received signal.
  • the frequency and/or timing of at least the initial received burst or bursts should be adjusted until the receiver's local references are in lock (whereafter the adjustment may not be needed) .
  • estimates of the offsets for each received burst are made, and each received burst is adjusted appropriately, even after the receiver is in lock.
  • the frequency and timebase offsets can be estimated and adjusted for in any way known in the art.
  • coarse frequency and timing offsets are estimated from a predetermined portion of the received signal burst from which appropriate frequency and timing information can be derived, such as the frequency correction field in
  • This coarse offset estimation and correction is preferably no longer performed once the receiver's local frequency and timebase references are sufficiently close to the received signal timing and frequency (e.g. are within a predetermined margin of these parameters), i.e. the receiver is "in lock", as it is then not entirely necessary.
  • finer estimates of the frequency and timing offsets are preferably also made after the above coarse estimation, to further refine the adjustment and tuning process.
  • An advantage of correcting the received signal burst as in this embodiment of the present invention is that the coarse offset is removed first, therefore allowing a further, finer estimate of the residual or remaining offset to be made. This means that more accurate adjustments to the receiver's local frequency and timebase references can be made over fewer received signal bursts, such that faster frequency and timebase lock to the received signal can be achieved.
  • a further timing offset estimation is made by estimating the position of symbols, or bits, etc in the received signal burst relative to their expected positions. This can be done by, for example, as is known in the art, searching the received signal burst for, or correlating the received signal burst with, a predetermined sequence, such as a training sequence, over a window of time at plural predetermined time delays relative to the start of the window. This yields a finer timing offset that can be used to advance or retard the received signal burst by an amount appropriate to remove the offset .
  • a finer frequency offset can be estimated (preferably after the coarse offset has been removed) by considering the ideal (i.e. transmitted) phases of the received symbols and the actual phases the symbols in the signal burst are received at, e.g. by comparing the phase that each symbol is actually received at and the phase that the symbol would have been received at under ideal conditions (i.e. the phase at which it was or should have been transmitted) , preferably over a group of plural symbols.
  • These finer offset estimations are preferably performed and used to adjust each received signal burst, even after the receiver has achieved 'lock in'.
  • All of the above estimations are preferably also used to adjust the receiver's local timebase and frequency references.
  • the coarser offsets estimated and any finer offsets estimated are used together to adjust the receiver's local references appropriately.
  • the coarser estimates need no longer be used, but preferably the finer estimate, if any, is always used to make any appropriate fine adjustments to the receiver's local frequency and timing references. It is believed that using an appropriate combination of coarser and finer offset estimates to tune a radio receiver's local frequency and/or timing references is advantageous in its own right .
  • a radio receiver comprising : a local frequency reference; means for receiving a transmitted radio signal; means for detecting a predetermined portion of the received signal from which information relating to the frequency of the received signal can be derived and for estimating therefrom a first frequency offset of the receiver's local frequency reference relative to the received signal; means for estimating a further frequency offset in the received signal from the expected transmitted phase and the actual received phase of the symbols in the received signal; means for using the first estimated frequency offset and the further estimated frequency offset to determine an overall frequency offset and for using the overall frequency offset to adjust the local frequency reference of the receiver.
  • a method of operating a radio receiver having a local frequency reference comprising: receiving a transmitted radio signal; detecting a predetermined portion of the received signal from which information relating to the frequency of the received signal can be derived and estimating therefrom a first frequency offset of the receiver's local frequency reference relative to the received signal; estimating a further frequency offset in the received signal on the basis of the ideal and actual phases of the symbols in the received signal; using the first estimated frequency offset and the further estimated frequency offset to determine an overall frequency offset and using the overall frequency offset to adjust the local frequency reference of the receiver .
  • the above third and fourth aspects of the invention estimate the frequency of a received signal more accurately and therefore can be used to tune the local frequency reference of the receiver more accurately. This permits faster frequency lock to the received signal, and therefore improved readiness for operation of the receiver and faster call setup.
  • the receiver or method of the third or fourth aspect of the invention further includes a local timebase reference and appropriate timing offset estimation processes or means, such as any one or more of the timing offset estimation processes or stages discussed above.
  • a radio receiver comprising: a local timebase reference; means for receiving a transmitted radio signal; means for detecting a predetermined portion of the received signal from which information relating to the timing of the received signal can be derived and for estimating therefrom a first timing offset of the receiver's local timebase reference relative to the received signal; means for searching the received signal for a predetermined signal sequence over a window of time at a plurality of predetermined time delays relative to the start of the time window to thereby estimate a further timing offset; means for using the first timing offset and the further timing offset to determine an overall timing offset and for using that overall timing offset to adjust the local timebase reference of the receiver.
  • the fifth and sixth aspects of the invention estimate the timing of a received signal more accurately, and therefore can be used to tune the local timebase reference of the receiver more accurately. This permits faster timebase lock to the received signal, and therefore improved readiness for operation of the receiver and faster call set-up.
  • the receiver or method of the fifth or sixth aspect of the invention further includes a local frequency reference and appropriate frequency offset estimation processes or means, such as any one or more of the frequency offset estimation processes or stages discussed above .
  • a radio receiver comprising: a local frequency reference; a local timebase reference; means for receiving a transmitted radio signal; means for detecting a predetermined portion of the received signal from which information relating to the frequency and timing of the received signal can be derived and for estimating therefrom a first frequency offset and a first timing offset of the receiver's local frequency and timebase references relative to the received signal; means for estimating a further frequency offset in the received signal from the expected transmitted phase and the actual received phase of the symbols in the received signal; means for searching the received signal for a predetermined signal sequence over a window of time at a plurality of predetermined time delays relative to the start of the time window to thereby estimate a further timing offset; means for using the first timing offset and the further timing offset to determine an overall timing offset and for using that overall timing offset to adjust the local timebase reference of the receiver; means for using the first estimated frequency offset and the further estimated frequency offset to determine an overall frequency offset and for using the overall frequency offset to adjust the local timebase reference of the receiver; means for using the first estimated frequency offset
  • a method of operating a radio receiver having a local frequency reference and a local timebase reference comprising: receiving a transmitted radio signal; detecting a predetermined portion of the received signal from which information relating to the frequency and timing of the received signal can be derived and determining therefrom a first frequency offset and a first timing offset of the receiver's local frequency and timebase references relative to the received signal; estimating a further frequency offset in the received signal on the basis of the ideal and actual phases of the symbols in the received signal; searching the received signal for a predetermined signal sequence over a window of time at a plurality of predetermined time delays relative to the start of the time window to thereby estimate a further timing offset; using the first timing offset and the further timing offset to determine an overall timing offset and using that overall timing offset to adjust the local timebase reference of the receiver; using the first estimated frequency offset and the further estimated frequency offset to determine an overall frequency offset and using the overall frequency offset to adjust the local frequency reference of the receiver.
  • the above third to eighth aspects of the invention preferably further comprise using each estimated frequency or timing offset to adjust the received signal in time or frequency appropriately, most preferably before that signal is passed to the next offset estimation stage.
  • the methods in accordance with the present invention may be implemented at least partially using software e.g. computer programs. It will thus be seen that when viewed from further aspects the present invention provides computer software specifically adapted to carry out the methods hereinabove described when installed on data processing means, and a computer program element comprising computer software code portions for performing the methods hereinabove described when the program element is run on a computer.
  • the invention also extends to a computer software carrier comprising such software which when used to operate a radio system or receiver comprising a digital computer causes in conjunction with said computer said system or receiver to carry out the steps of the method of the present invention.
  • a computer software carrier could be a physical storage medium such as a ROM chip, CD ROM or disk, or could be a signal such as an electronic signal over wires, an optical signal or a radio signal such as to a satellite or the like.
  • FIG. 1 shows a radio receiver in accordance with the present invention
  • Figure 2 is a drawing of the complex plane showing ideal and exemplary received TETRA symbols in each quadrant.
  • the present embodiment is described with reference to the TETRA system, which is a TDMA (time division multiple access) radio system. It should be noted that the present invention is, of course, applicable to other radio systems (and not just TDMA systems) as well.
  • TDMA time division multiple access
  • Figure 1 shows a radio receiver which receives at RF receiver subsystem 1 a radio frequency (RF) input signal . That signal is captured and down converted into a digital complex baseband representation of the signal by the RF receiver subsystem 1. This received complex baseband signal is then passed through a series of stages in the receiver which are used to estimate accurately the frequency and timebase offsets from the received signal, to adjust the received signal for these offsets internally, and to tune the receiver's local internal frequency and timebase references for subsequent transmission or reception.
  • the receiver operates in one of two modes . When the receiver is not tuned to the transmitted signal frequency and timing, i.e. it is out of lock, it must first synchronise itself to the relevant base station. It therefore searches incoming radio signals for base station synchronisation signals which it can attempt to lock to.
  • RF radio frequency
  • the receiver is initially configured by a control subsystem 2, and its local timing reference T ref , local frequency reference F ref and DC null which are needed to control the RF receiver subsystem 1 are set at default levels which are approximately in the middle of their tunable ranges .
  • the received RF input signal burst is down converted by the RF receiver subsystem 1 into a digital complex baseband representation of that signal .
  • the baseband representation is then input to a DC null stage 3 which is responsible for measuring, tracking and removing DC offsets which may be present in the complex baseband signal from the receiver subsystem 1.
  • the DC null stage 3 estimates DC offsets from the complex baseband signal and subtracts them digitally from the baseband signal before passing it to the next stage.
  • the DC offset value may be applied to the receiver subsystem hardware where the offset may be removed.
  • the output from the DC null stage in this synchronisation mode is then passed to a frequency correction field detection stage 4, which is responsible for searching the incoming signal for a predetermined signal portion from which information regarding the frequency and timing of the transmitted signal can be derived.
  • this signal portion is the frequency correction field which is a portion of one type of burst transmitted by a base station (or another mobile station when operating in direct mode) in TETRA. Detection of this field in the signal can be used to yield coarse frequency and timing offset estimates ( ⁇ F and ⁇ T) as follows.
  • FCF 'frequency correction field'
  • This field s detected by carrying out an integration over the signal 2.25 kHz above the carrier frequency:
  • N 32 (the duration of the signal portion 2.25 kHz above the carrier frequency of the frequency correction field)
  • y 1 is the current complex symbol, sampled at the local symbol rate
  • z is a complex decision variable which reaches a maximum at the position of the frequency correction field
  • * denotes the complex conjugate.
  • T is the symbol duration
  • the timing error or offset ⁇ T is estimated as follows.
  • the ideal position or time, t fcf , of the frequency correction field in a synchronisation burst is fixed and predetermined and thus known to the receiver.
  • This time, t £cf will be the position or time, t pk , of the peak or maximum of the above decision variable Z (which can be derived from the above analysis) if the receiver is locked to the timing of the transmitted signal.
  • the coarse offsets estimated are used by the frequency correction field detection stage 4 to shift the received signal up or down in frequency and adjust its timing position by an appropriate amount to remove the estimated frequency and timing offsets before the signal is passed on to the next stage of the receiver, i.e. before any subsequent processing of the received signal burst.
  • the estimated frequency offset ⁇ F is removed from the received samples by correcting them with a rotating complex phasor p k as follows:
  • the estimated timing offset ⁇ T can be removed from the captured signal burst by advancing or retarding the start position of that signal burst in the receiver's memory by an appropriate amount .
  • the coarse frequency and timing offsets derived are also supplied to the timebase estimator 13 and automatic frequency control stage 15, which will be discussed further below.
  • the next stage of the receiver is a square timing recovery stage 5.
  • This stage estimates a finer timing error, ⁇ , which it derives from the phase of the received signal averaged over a burst. It also estimates the optimum sampling point of a received symbol in the signal (i.e. the positions of the symbols in the signal) , and decimates the signal from four complex samples per symbol to one complex sample per symbol.
  • That method comprises estimating the timing error, ⁇ , by estimating, over a burst, the phase of the square magnitude of the received signal at the symbol rate using a discrete Fourier Transform.
  • the received samples are also interpolated to an optimum sampling point (which is defined to be that sampling point which maximises the signal to noise ratio) and decimated from four samples per symbol to one sample per symbol during the interpolation process.
  • the derived error value ⁇ is provided to the timebase estimator 13, and also used to interpolate the received signal digitally to the optimum sampling point before it is passed onto the next stage of the receiver.
  • a less complex square timing recovery arrangement could be used which estimates the sampling instant, but does not necessarily interpolate the received samples to the optimum sampling time on the current burst. (This arrangement would have to iterate timebase corrections over successive bursts to achieve timing lock (frequency lock would not be affected) , thereby taking longer to achieve timing lock, and is therefore not preferred.)
  • the next stage of the receiver is the digital frequency correction stage 6.
  • This stage estimates and removes any residual frequency offset, ⁇ F, in the signal on the basis of the estimated ideal phases and the actual received phases of the received symbols in the signal. It preferably considers the whole signal burst to estimate the residual frequency offset, ⁇ F. (There may be a residual frequency offset at this stage for a number of reasons, such an inaccurate previous estimate, Doppler Shift or noise.)
  • This digital frequency correction can be carried out in the TETRA system as follows.
  • differential demodulation is carried out:
  • the demodulated symbols, z i f are complex numbers whose phase (under ideal conditions) will correspond to the transmitted phase. However, in practice the phase of the received signal will include errors due to noise, fading and frequency offset .
  • the digital frequency correction stage subtracts the ideal phase from the received phase (i.e. the phase that the symbol is actually received at) for each symbol and integrates over the burst of N symbols:
  • the received signal is shifted up or down in frequency by the digital frequency correction stage 6 by the appropriate amount to remove the estimated frequency offset before it is passed onto the next stage.
  • the correction can be performed with a rotating complex phasor p k as described above for the frequency correction field detection stage 4, but using ⁇ f for the frequency offset .
  • the fine frequency offset ⁇ F is also provided to the automatic frequency control stage 15.
  • the digital frequency correction stage is not essential, although it is strongly preferred, since it is a very useful step in achieving fast frequency-lock.
  • the next stage in the receiver is the slot synchronisation stage 7. This stage is responsible for locating the precise position (timing) of the slots
  • timing offset estimate ⁇ T and a training sequence identity, TS .
  • the received signal is advanced or retarded by the appropriate amount to remove the estimated timing offset before it is passed onto the next stage.
  • the estimated timing offset ⁇ T is also provided to the timebase estimator 13.
  • stages comprise a differential demodulator 8 which converts the complex signal information it receives from the signal into soft decision values, each value representing one bit of the signal .
  • the soft decision value is then passed to the burst demultiplexer 9 which splits the received soft decision values into appropriate streams for the logical channel decoders 10, 11, 12, based on the training sequence identified by the symbol synchronisation unit 7 and the initial system configuration.
  • the logical channel decoders 10, 11, 12 decode the signal and provide the appropriate output bits.
  • the estimated frequency and timing offsets are also used to adjust the local internal frequency and timebase references of the receiver, to try to tune them to the received signal.
  • the local timebase reference or system timebase 14 of the receiver is adjusted by the timebase estimator 13.
  • the timebase estimator 13 combines the coarse timing estimate ⁇ T from the frequency correction field detection stage 4, the symbol timing estimate ⁇ T from the symbol synchronisation stage 7, and the fine timing phase ⁇ from the square timing recovery stage 5 into an overall timing offset.
  • This overall timing offset is applied to the system timebase 14 at the appropriate time to synchronise the receiver's timebase to the base station's timebase such that the timebases are in lock. If desired, the applied timing offset may be smoothed to remove jitter. It should be noted that the adjustment to the system timebase 14 only affects signals which are received after the adjustment is made. Thus prior to this the receiver must rely on its ability to make timing adjustments within the processing stages as described above .
  • the receiver's local frequency reference or system frequency reference 16 is adjusted by the automatic frequency control stage 15 on the basis of the coarse frequency estimate ⁇ F and the fine frequency estimate ⁇ F.
  • the automatic frequency control stage 15 combines the coarse frequency estimate ⁇ F and the fine frequency estimate ⁇ F into an overall frequency offset . This is applied to the system frequency reference oscillator to remove the offset. This process tunes the radio receiver's frequency reference to the base station. If desired, the applied frequency offset may be smoothed to remove jitter. (Again it should be noted that the adjustment to the system frequency reference 16 only affects signals which are received after the adjustment is made. Prior to this the receiver must rely on the frequency adjustments made within the signal processing stages as described above .
  • the automatic frequency control stage 15 also estimates if the frequency is in lock (at which point transmissions are allowed to be made) . It provides a signal F lock to the control subsystem 2 to indicate lock status .
  • the receiver's local frequency and timebase references are sufficiently close to the received signal frequency and timing (e.g. within a predetermined margin of those parameters), i.e. the receiver is in lock, it is no longer necessary to estimate and apply the coarse frequency and timing offsets ⁇ T, ⁇ F performed by the frequency correction field detection stage 4.
  • the receiver switches to normal or lock mode in which incoming signals pass through the DC null stage 3, but by-pass the frequency correction field detection stage 4, before passing onto the subsequent stages. This is because in this mode it is necessary to make only small corrections to frequency and timebase digitally to the received signal since the receiver is already in lock. Small corrections are also made in the analogue domain to the system time base.
  • the above embodiment provides a baseband receiver architecture for a mobile radio system in which the frequency and timing of a received signal can be measured accurately and used to tune local frequency and timebase references to enable the mobile station to be ready for subsequent transmission or reception rapidly.
  • typically the described baseband receiver architecture nearly always enables the mobile station to receive and decode the initial burst received, and, having adjusted its frequency and timebase reference, to receive further signals or make transmissions at the first opportunity (i.e. within one burst) .
  • the receiver uses two different frequent estimates and three different timebase estimates to configure the mobile ' s frequency and timing references.
  • faster frequency and timebase lock to base station or mobile station in direct mode
  • the present invention is particularly applicable to mobile radio stations operating in direct mode (i.e. in which mobile stations communicate directly over the air interface without the presence of a base station) , since in that mode of operation the frequency and timing reference is generally not as stable as that originating from a mobile station from a fixed base station. In this case the frequency and timebase agility of the receiving mobile station must be higher. The present invention provides this .

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Circuits Of Receivers In General (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)

Abstract

Un récepteur radio reçoit en un sous-système de réception RF (1) un signal d'entrée haute fréquence (RF). Le signal est capté et la fréquence en est abaissée en une représentation de signal complexe en bande de base du signal par le sous-système de réception RF (1). Ce signal complexe en bande de base transite ensuite par une série d'étapes dans le récepteur, comprenant une étape de détection de correction de champ de fréquence (4), une étape de récupération de rythme en quadrature (5), une étape de correction de fréquence numérique (6) et une étape de synchronisation des intervalles de temps (7), qui sont utilisées pour une estimation précise des décalages de la fréquence et de la base de temps à partir du signal reçu, afin d'ajuster de manière interne le signal reçu concernant ces décalages, et d'accorder les références (14, 16) locales et internes de fréquence et de base de temps du récepteur pour transmission et réception ultérieures.
PCT/GB1999/004296 1999-02-08 1999-12-17 Acquisition de frequence et de base de temps dans un systeme de transmission radio WO2000048334A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU18718/00A AU1871800A (en) 1999-02-08 1999-12-17 Frequency and timebase acquisition in a radio communications system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9902754.2 1999-02-08
GBGB9902754.2A GB9902754D0 (en) 1999-02-08 1999-02-08 Frequency and timebase acquisition in a radio communications system

Publications (1)

Publication Number Publication Date
WO2000048334A1 true WO2000048334A1 (fr) 2000-08-17

Family

ID=10847312

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/004296 WO2000048334A1 (fr) 1999-02-08 1999-12-17 Acquisition de frequence et de base de temps dans un systeme de transmission radio

Country Status (3)

Country Link
AU (1) AU1871800A (fr)
GB (2) GB9902754D0 (fr)
WO (1) WO2000048334A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002025839A1 (fr) * 2000-09-15 2002-03-28 Koninklijke Philips Electronics N.V. Station secondaire et procede d'operation d'une telle station
WO2002032067A1 (fr) * 2000-10-11 2002-04-18 Nokia Corporation Procede de regulation de frequence automatique
EP1392008A1 (fr) * 2002-08-23 2004-02-25 Teltronic S.A.U. Synchronisation dans un système de communication selon le standard TETRA

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0355587A2 (fr) * 1988-08-15 1990-02-28 Nortel Networks Corporation Récupération d'horloge et de porteuse pour AMRT sans séquence de préambule
US5276706A (en) * 1992-05-20 1994-01-04 Hughes Aircraft Company System and method for minimizing frequency offsets between digital communication stations
US5390216A (en) * 1991-11-02 1995-02-14 Robert Bosch Gmbh Synchronization method for a mobile radiotelephone
US5625573A (en) * 1995-03-01 1997-04-29 Hughes Electronics Fast acquisition of GMSK-modulated signal for CDPD applications
DE19639309A1 (de) * 1996-09-25 1998-04-02 Rohde & Schwarz Verfahren zur Rahmensynchronisation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0355587A2 (fr) * 1988-08-15 1990-02-28 Nortel Networks Corporation Récupération d'horloge et de porteuse pour AMRT sans séquence de préambule
US5390216A (en) * 1991-11-02 1995-02-14 Robert Bosch Gmbh Synchronization method for a mobile radiotelephone
US5276706A (en) * 1992-05-20 1994-01-04 Hughes Aircraft Company System and method for minimizing frequency offsets between digital communication stations
US5625573A (en) * 1995-03-01 1997-04-29 Hughes Electronics Fast acquisition of GMSK-modulated signal for CDPD applications
DE19639309A1 (de) * 1996-09-25 1998-04-02 Rohde & Schwarz Verfahren zur Rahmensynchronisation

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002025839A1 (fr) * 2000-09-15 2002-03-28 Koninklijke Philips Electronics N.V. Station secondaire et procede d'operation d'une telle station
WO2002032067A1 (fr) * 2000-10-11 2002-04-18 Nokia Corporation Procede de regulation de frequence automatique
US6628926B1 (en) 2000-10-11 2003-09-30 Nokia Networks Oy Method for automatic frequency control
EP1392008A1 (fr) * 2002-08-23 2004-02-25 Teltronic S.A.U. Synchronisation dans un système de communication selon le standard TETRA
WO2004019516A1 (fr) * 2002-08-23 2004-03-04 Teltronic S.A.U. Mecanisme de synchronisation dans un systeme de communication tetra

Also Published As

Publication number Publication date
GB2347050A (en) 2000-08-23
GB9929975D0 (en) 2000-02-09
AU1871800A (en) 2000-08-29
GB9902754D0 (en) 1999-03-31
GB2347050B (en) 2001-04-25

Similar Documents

Publication Publication Date Title
US5541552A (en) Method of and apparatus for demodulating a signal conveyed by multiple carrier
US6567480B1 (en) Method and apparatus for sampling timing adjustment and frequency offset compensation
US5936961A (en) Signalling packet for communication system with reference modulated in accordance with a time-dependent law
US6704374B1 (en) Local oscillator frequency correction in an orthogonal frequency division multiplexing system
EP0896457B1 (fr) Synchronisation de symbole pour signaux multiporteurs à intervalle de garde
US7453792B2 (en) Receiver architecture for pilot based OFDM systems
EP1618696B1 (fr) Appareil de synchronisation de frequence et procede de synchronisation de frequence
US20020065047A1 (en) Synchronization, channel estimation and pilot tone tracking system
US20040013209A1 (en) GFSK receiver
WO1996002990A2 (fr) Procede et dispositif de synchronisation d'un emetteur et d'un recepteur dans un systeme numerique
EP0186691A1 (fr) Technique pour obtenir une synchronisation temporelle et en frequence pour des modems utilisant des symboles connus (a l'exception des donnees a traiter) faisant partie de leur format normal de transmission des donnees
US6590945B1 (en) Method and apparatus for frequency offset compensation
US5732105A (en) Method of estimating signal quality in a DPSK demodulator
US20050084023A1 (en) Method for the frequency and time synchronization of an odm receiver
US6373858B1 (en) Burst format and associated signal processing to improve frequency and timing estimation for random access channels
US7167535B2 (en) Circuit sharing for frequency and phase error correction
JPH11252038A (ja) デジタル放送の受信機
EP0895388B1 (fr) Synchronisation de symbôles et détéction de mode pour signaux multiporteurs
US7075997B1 (en) OFDM frame synchronization
EP1402698B1 (fr) Correction de frequence pour un systeme a ondes porteuses multiples
WO2000048334A1 (fr) Acquisition de frequence et de base de temps dans un systeme de transmission radio
US7529295B1 (en) Acquiring frequency and phase offset estimates using frequency domain analysis
EP1157464B1 (fr) Boucle de poursuite de frequence et procede de poursuite de frequence
CN104717169A (zh) 一种lte-tdd频偏校正装置和方法
EP1042876B1 (fr) Procede d'estimation d'erreurs de frequence

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AL AM AT AU AZ BA BB BG BR BY CA CH CN CR CU CZ DE DK DM EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SK SL TJ TM TR TT TZ UA UG US UZ VN YU ZA ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

CR1 Correction of entry in section i

Free format text: PAT. BUL. 27/2001 UNDER (81) ADD "AU, NZ"

122 Ep: pct application non-entry in european phase