WO1996019056A1 - Method at ofdm-reception for correction of frequency, time window, sampling clock and slow phase variations - Google Patents
Method at ofdm-reception for correction of frequency, time window, sampling clock and slow phase variations Download PDFInfo
- Publication number
- WO1996019056A1 WO1996019056A1 PCT/SE1995/001413 SE9501413W WO9619056A1 WO 1996019056 A1 WO1996019056 A1 WO 1996019056A1 SE 9501413 W SE9501413 W SE 9501413W WO 9619056 A1 WO9619056 A1 WO 9619056A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- frequency
- phase error
- amplitude
- reference symbols
- carriers
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/02—Channels characterised by the type of signal
- H04L5/06—Channels characterised by the type of signal the signals being represented by different frequencies
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2662—Symbol synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2668—Details of algorithms
- H04L27/2673—Details of algorithms characterised by synchronisation parameters
- H04L27/2675—Pilot or known symbols
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/261—Details of reference signals
- H04L27/2613—Structure of the reference signals
Definitions
- the present invention relates to a method at digital system for correction of frequency, sampling clock and phase error which varies slowly with time, i.e. low- frequency phase noise.
- the receiver is a so called OFDM- receiver which receives digital information in frames.
- OFDM Orthogonal Frequency Division Multiplex
- COFDM Coded Orthogonal Frequency Division Multiplex
- the Patent document EP 448493 describes a system for transmission of TV digitally.
- the picture information is transmitted to a mobile user and is divided into two parts; one is used to recreate a normal TV-picture and the other together with the first one to create a larger picture.
- a receiver for digital radio signals The receiver utilizes a window method to minimize the intersymbol interference arising at multipath propagation.
- the receiver will be equipped with a time window module which is used to extract usable samples from the received signal.
- the American document US 5 228 025 describes a method to transmit digital data via radio, preferably to mobile receivers.
- the method transmits a synchronization sequence in the form of at least one frequency which varies in one for the receiver known way.
- the synchronization sequence is utilized for tuning the local oscillator.
- the first prototype for transmission and reception of DAB Digital Audio Broadcasting
- the first is called zero symbol and contains nothing but is used by the receiver on one hand for symbol synchronization, and on the other for estimation of interference in the channel.
- the second symbol consists of a so called chirp or sine sweep signal which is a sine shaped signal, the frequency of which changes linearly with time and which sweeeps over the whole channel width. This is used by the receiver on one hand for adjustment of the location of the time window, i.e. division of the received signal in segments which are each processed by means of FFT, and on the other for estimation of the transmission function of the channel and estimation of deviations in the carrier frequency, if any.
- TFPC-signal Time Frequency Phase Control
- CAZAC-symbol which is used by the receiver both for timing, frequency adjustment and for estimation of the transmission function.
- the present invention relates to a method for correction of frequency, time window, sampling clock and time variable phase error at OFDM-reception.
- One from a transmitter transmitted signal is received by the OFDM- receiver.
- the signal which is divided into consecutive frames, which each in its turn is divided into symbols, contains with certains intervals reference symbols with a predetermined content.
- Each frame is divided into a number of symbols which regarding time follow each other.
- Respective symbol is allotted a serial number, and the mentioned reference symbols are preferably transmitted in pairs.
- the receiver analyzes the different reference symbols.
- the signals in the reference symbols consist of so called chirp signals, i.e. so called sine sweeep signals which are sine signals the frequency of which is linearly changed with the time and which sweeps over the whole channel width.
- One of the chirp signals goes from the highest frequency to the lowest in time, and the other chirp signal from the lowest frequency to the highest frequency.
- the relation between the contents of the reference symbols in pair regarding time and frequency is utilized for adjustment of the frequency of the receiver.
- the impulse response is calculated from the signals of the received reference frames at which correction of time window and sampling clock can be performed.
- the main focus of the impulse response is determined, at which the real position of the time window can be determined.
- the position of the time window is adjusted in relation to wished position by the sampling clock being adjusted in relation to the difference between the mentioned main focus and wished position.
- Each symbol consists of a number of superimposed carriers with among themselves different frequencies.
- each of the carriers further is arranged that its phase and amplitude, which can also be described by its real and imaginary part, is modulated by the data information which shall be transmitted.
- the mentioned real and imaginary parts are allotted a definite position in a matrix system, in the matrix system real and imaginary parts are allowed to take different positions which are accepted.
- the relation between the point which is indicated by received real and imaginary part and the ideal position in the matrix indicates an angle difference to the ideal position which is utilized for correction of the phase error at reception.
- the indicated method gives a possibility to make accurate adjustments of the receiver in a way which has not previously been possible and which gives increased robustness at OFDM-reception.
- the method further allows that the necessary adjustments in the receiver are possible to perform in a simple way.
- the method thus allows that the program transmission can be performed with the high precision which is expected in these connections.
- Figure 1 shows schematically how the receiver at first locates the chirp signals by means of a set of binary correlators and after that precision adjusts time window, carrier frequency and phase according to the invention.
- Figure 2 shows how the OFDM-signal is created by means of IFFT (Invers Fast Fourier Transform). Each entry on the IFFT corresponds to a carrier.
- IFFT Invers Fast Fourier Transform
- Figure 3 shows the matrix for estimation of phase error with points according to the 16QAM-system and illustrates the angle relation between the real position of the received vector and the ideal position.
- a signal sequence is transmitted from a transmitter and received by a receiver.
- the signal sequence comprises a number of symbols which are arranged to a frame. At the beginning of each frame one or more synchronization symbols are arranged. At least two of the mentioned synchronization frames contain so called chirp signals.
- a chirp signal is a sine signal the frequency of which is changed linearly with time.
- a set of correlators are used in order to detect the position of the chirp signal .
- the auto correlation for a chirp signal has a very acute maximum.
- the symbol bit of the chirp signal is received and is compared with a stored signal. The signal is compared by being processed through a number of XNOR-gates. The number of equal bits, i.e.
- the hamming weight of the resulting vector is obtained as an output signal from the correlator.
- the synchronization signals which at that are obtained in 1 in Figure 1 are brought back to a frame structure generator, 2 in Figure 1, which controls division of the incoming signal in frames and symbols, and numbers the individual samples within each symbol.
- the frame structure generator in this way controls the division of the signal in appropriate time windows to the FFT (Fast Fourier Transform) .
- the symbols coming out from the FFT are after that forwarded to among other things a signal processor, 3 in Figure 1, where correction values for carrier frequency and the frequency of the sampling clocks is calculated.
- the transmitted signal from the transmitter has been created by means of an IFFT (Inverse Fast Fourier Transform) according to Figure 2.
- IFFT Inverse Fast Fourier Transform
- each of the carriers has been given an amplitude and phase according to he formula e j ⁇ ⁇ / N ⁇ W here j ⁇ corresponds to the number of the carrier, and N the number of carriers.
- a down-chirp signal is created in a similar way but with negative phase; consequently the formula becomes e -:, ⁇ /N.
- the received signal is made subject to a Fast Fourier Transform (FFT) in the receiver.
- FFT Fast Fourier Transform
- the correction calculations which are performed in unit 3 in Figure 1 implies that a multiplication by the for the carrier allotted inverse angle is performed by received up-chirp being multiplied by an ideal down-chirp, and that received down-chirp is multiplied with an ideal up- chirp.
- signals which we call de-rotated chirps, each constitutes an estimate of the transmission function of the channel. For an ideal channel these estimates become equal to 1 for all carriers. If a shift of the carrier frequency has occurred somewhere in the channel, the de-rotated chirps will have a remaining phase shift which is linearly depending on the serial number of the carrier. The changes get different symbols in the up- and the down- chirp.
- the phase positions of the de-rotated chirps are also influenced by frequency selective fading and by wrong setting of the time window, but this influence has the same symbol in both chirps. Therefore the carrier error can be extracted by subtraction of the de-rotated phase positions of one of the chirps from the other.
- the numerical value of the carrier error can in one in itself known way be estimated from the phase position's linear depending on the carrier number. The obtained number is after that utilized in an in itself known way to correct the frequency.
- the impulse response of the channel is obtained by an IFFT-transform on the de-rotated chirps.
- the impulse response is multiplied with a weighting function before the position of the main focus is calculated.
- the difference between this position and a predetermined wished position constitutes a correction signal which after filtering controls the clock-frequency of the A/D-converter, at which the correction value successively will be adjusted towards zero. Consequently the time window will land up in wished position.
- the impulse response of the channel can be estimated both from received up-chirp and down-chirp. It is to advantage to use the sum of these two estimates at the main focus calculation because an error in carrier frequency will influence the position of the main focus with different symbols depending on whether it is calculated on an up-chirp or on a down-chirp. The main focus position of the sum of the two impulse responses will therefore be insensible to errors in carrier frequency because the error will neutralize itself.
- the received carriers are arranged in a matrix system with respect to their imaginary respective real part. These points are in the complex number plan allotted an area within which they are allowed to exist. A point in the complex number plan which occur within the mentioned area is regarded to symbolize a certain transmitted data sequence.
- the relation of the point to the ideal position indicates an angle relation between the ideal position and the real position.
- the mentioned angle difference indicates the phase error in the reception.
- the average of the angle differences calculated from all the different carriers in the same symbol constitutes an estimate of the phase error.
- the in this way obtained phase error can after that be combined with previously obtained phase errors and be utilized for phase correction of all carriers in the symbol in question, and for estimation of the expected phase error at the reception of next symbol. It can also be used for estimation of small frequency deviations because these give rise to phase errors with constant change from symbol to symbol.
- the mentioned method for estimation of the phase error can be further developed in different ways. Two different improvements of the method have been identified. One or both improvements can be applied.
- the first improvement is based on the fact that the amplitude of the received signal on one and the saute occasion can be of different strength for different carriers, frequencies. This is due to interference from reflections of the signal, so called multipath propagation, or interference from other transmitters which transmits the same signal in a so called single frequency network.
- the carriers which are subject to destructive interference are weakened and get a worse signal/noise-relation than the other.
- the frequency depending transmission function for the channel can be calculated in the receiver by analysis of the received chirps. At calculation of the average of the angle differences the values from the different carriers can be weighted with the calculated transmission function at which angle differences from carriers with high attenuation in the channel is given a lower weight than those with low attentuation.
- the strong noise from the attenuated carriers can by that be made to have a minimal influence on the estimation of the phase error.
- the second improvement is based on the fact that one and the same noise effect in the received signal gives different uncertainty in the estimation of the phase error for signals far from or close to the origin of coordinates.
- the mentioned angle relations are weighed in relation to the distance to the origin of coordinates.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP8518667A JPH10510958A (en) | 1994-12-14 | 1995-11-27 | Method for correcting frequency, time window, sampling clock and gradual phase fluctuation in OFDM reception |
AU42751/96A AU4275196A (en) | 1994-12-14 | 1995-11-27 | Method at ofdm-reception for correction of frequency, time window, sampling clock and slow phase variations |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE9404356A SE504787C2 (en) | 1994-12-14 | 1994-12-14 | Method of OFDM reception for correction of frequency, time window, sampling clock and slow phase variations |
SE9404356-9 | 1994-12-14 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1996019056A1 true WO1996019056A1 (en) | 1996-06-20 |
Family
ID=20396337
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE1995/001413 WO1996019056A1 (en) | 1994-12-14 | 1995-11-27 | Method at ofdm-reception for correction of frequency, time window, sampling clock and slow phase variations |
Country Status (6)
Country | Link |
---|---|
JP (1) | JPH10510958A (en) |
KR (1) | KR980700750A (en) |
CN (1) | CN1170486A (en) |
AU (1) | AU4275196A (en) |
SE (1) | SE504787C2 (en) |
WO (1) | WO1996019056A1 (en) |
Cited By (40)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1997007620A1 (en) * | 1995-08-16 | 1997-02-27 | Philips Electronics N.V. | Transmission system with improved symbol processing |
EP0818904A2 (en) * | 1996-07-12 | 1998-01-14 | Roke Manor Research Limited | Timing recovery for DAB receivers |
EP0829988A2 (en) * | 1996-09-16 | 1998-03-18 | NOKIA TECHNOLOGY GmbH | Symbol synchronization and sampling frequency adjustment in an OFDM receiver |
EP0837582A2 (en) * | 1996-10-18 | 1998-04-22 | Alpine Electronics, Inc. | Symbol synchronization in a DAB receiver |
EP0859494A2 (en) * | 1997-02-17 | 1998-08-19 | Matsushita Electric Industrial Co., Ltd. | Synchronisation of the local oscillator in multicarrier systems |
FR2765058A1 (en) * | 1997-06-24 | 1998-12-24 | Thomson Csf | METHOD AND DEVICE FOR FREQUENCY CORRECTION IN VARIABLE CARRIER FREQUENCY MODULATION AND SEVERAL SUBCARRIERS |
EP0930751A1 (en) * | 1998-01-19 | 1999-07-21 | Victor Company Of Japan, Limited | Method and apparatus for receiving orthogonal frequency division multiplexed signal |
EP0952713A2 (en) * | 1998-04-24 | 1999-10-27 | Nec Corporation | A frequency and timing synchronization circuit making use of a chirp signal |
WO1999057819A1 (en) * | 1998-05-01 | 1999-11-11 | Telefonaktiebolaget Lm Ericsson (Publ) | Search window delay tracking in code division multiple access communication systems |
WO2000002325A1 (en) * | 1998-07-01 | 2000-01-13 | Zenith Electronics Corporation | Receiver synchronizer using chirps sequences |
WO2000031898A1 (en) * | 1998-11-24 | 2000-06-02 | Hughes Electronics Corporation | Acquisition mechanism for a mobile satellite system |
WO2000031899A1 (en) * | 1998-11-24 | 2000-06-02 | Hughes Electronics Corporation | Synchronization in mobile satellite systems using dual-chirp waveform |
EP1006699A2 (en) * | 1998-11-30 | 2000-06-07 | Kabushiki Kaisha Toshiba | Symbol synchronisation for multicarrier transmission |
EP1011234A1 (en) * | 1998-12-18 | 2000-06-21 | Sony International (Europe) GmbH | Synchronisation of a RF receiver using chirp signals with a passive correlator |
US6104767A (en) * | 1997-11-17 | 2000-08-15 | Telefonaktiebolaget Lm Ericsson | Method and apparatus for estimating a frequency offset |
EP1033872A2 (en) * | 1999-03-03 | 2000-09-06 | Hitachi, Ltd. | Receiving apparatus and receiving method |
EP1039713A2 (en) * | 1999-03-26 | 2000-09-27 | Nec Corporation | Reduction of delay in multicarrier receivers |
EP1041790A2 (en) * | 1999-03-30 | 2000-10-04 | Nec Corporation | Symbol timing recovery for OFDM demodulator |
US6156181A (en) * | 1996-04-16 | 2000-12-05 | Caliper Technologies, Corp. | Controlled fluid transport microfabricated polymeric substrates |
EP1063824A2 (en) * | 1999-06-22 | 2000-12-27 | Matsushita Electric Industrial Co., Ltd. | Symbol synchronisation in multicarrier receivers |
WO2001089168A2 (en) * | 2000-05-17 | 2001-11-22 | Zenith Electronics Corporation | Compound chirp and synchronizer for using same |
GB2364221A (en) * | 2000-03-15 | 2002-01-16 | Mitsubishi Electric Corp | Clock recovery circuit and method for OFDM |
US6396866B1 (en) * | 1998-05-01 | 2002-05-28 | Trw Inc. | Symmetric chirp communications acquisition method and apparatus |
WO2002049265A2 (en) * | 2000-12-15 | 2002-06-20 | Valence Semiconductor, Inc. | Fully digital symbol synchronization technique |
WO2002051086A2 (en) * | 2000-12-18 | 2002-06-27 | Schlumberger Canada Limited | Estimation and correction of sampling timing error in discrete multitone (dmt) receiver by an iterative process over individual carriers |
US6628697B1 (en) * | 1999-10-21 | 2003-09-30 | Cisco Technology, Inc. | Subscriber unit ranging in a point to multipoint system |
US6731622B1 (en) | 1998-05-01 | 2004-05-04 | Telefonaktiebolaget Lm Ericsson (Publ) | Multipath propagation delay determining means using periodically inserted pilot symbols |
WO2005041514A1 (en) * | 2003-10-18 | 2005-05-06 | Technische Universität Dresden | Method for synchronisation on transmission of ofdm signals |
US6907245B2 (en) | 2000-12-04 | 2005-06-14 | Telefonaktiebolaget Lm Ericsson (Publ) | Dynamic offset threshold for diversity handover in telecommunications system |
US6954644B2 (en) | 2000-12-04 | 2005-10-11 | Telefonaktiebolaget Lm Ericsson (Publ) | Using geographical coordinates to determine mobile station time position for synchronization during diversity handover |
US6980803B2 (en) | 2000-12-04 | 2005-12-27 | Telefonaktiebolaget Lm Ericsson (Publ) | Using statistically ascertained position for starting synchronization searcher during diversity handover |
EP1659750A3 (en) * | 2004-11-18 | 2006-08-30 | Pioneer Corporation | Detection of carrier-frequency offset in a multicarrier receiver |
WO2007060221A1 (en) * | 2005-11-25 | 2007-05-31 | Thales | Method for underwater transmission of data packets |
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EP2429101A1 (en) * | 2010-09-08 | 2012-03-14 | University College Cork-National University of Ireland, Cork | Multi-carrier system and method for use in an optical network |
EP3002884A1 (en) * | 2014-09-30 | 2016-04-06 | Semtech Corporation | Wireless communication method |
WO2018207359A1 (en) * | 2017-05-12 | 2018-11-15 | 三菱電機株式会社 | Wireless communication device, transmission method and reception method |
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US7142502B2 (en) * | 2001-08-30 | 2006-11-28 | Intel Corporation | Technique for continuous OFDM demodulation |
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Cited By (79)
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---|---|---|---|---|
US5848107A (en) * | 1995-08-16 | 1998-12-08 | U. S. Philips Corporation | Transmission system with improved symbol processing |
WO1997007620A1 (en) * | 1995-08-16 | 1997-02-27 | Philips Electronics N.V. | Transmission system with improved symbol processing |
US6156181A (en) * | 1996-04-16 | 2000-12-05 | Caliper Technologies, Corp. | Controlled fluid transport microfabricated polymeric substrates |
EP0818904A2 (en) * | 1996-07-12 | 1998-01-14 | Roke Manor Research Limited | Timing recovery for DAB receivers |
EP0818904A3 (en) * | 1996-07-12 | 2001-01-24 | Roke Manor Research Limited | Timing recovery for DAB receivers |
EP0829988A2 (en) * | 1996-09-16 | 1998-03-18 | NOKIA TECHNOLOGY GmbH | Symbol synchronization and sampling frequency adjustment in an OFDM receiver |
EP0829988A3 (en) * | 1996-09-16 | 1998-03-25 | NOKIA TECHNOLOGY GmbH | Symbol synchronization and sampling frequency adjustment in an OFDM receiver |
US6125124A (en) * | 1996-09-16 | 2000-09-26 | Nokia Technology Gmbh | Synchronization and sampling frequency in an apparatus receiving OFDM modulated transmissions |
EP0837582A3 (en) * | 1996-10-18 | 2001-08-22 | Alpine Electronics, Inc. | Symbol synchronization in a DAB receiver |
EP0837582A2 (en) * | 1996-10-18 | 1998-04-22 | Alpine Electronics, Inc. | Symbol synchronization in a DAB receiver |
EP0859494A3 (en) * | 1997-02-17 | 2000-08-23 | Matsushita Electric Industrial Co., Ltd. | Synchronisation of the local oscillator in multicarrier systems |
EP0859494A2 (en) * | 1997-02-17 | 1998-08-19 | Matsushita Electric Industrial Co., Ltd. | Synchronisation of the local oscillator in multicarrier systems |
EP1933516A3 (en) * | 1997-05-02 | 2009-03-04 | LSI Logic Corporation | Demodulating video broadcast signals |
FR2765058A1 (en) * | 1997-06-24 | 1998-12-24 | Thomson Csf | METHOD AND DEVICE FOR FREQUENCY CORRECTION IN VARIABLE CARRIER FREQUENCY MODULATION AND SEVERAL SUBCARRIERS |
WO1998059475A1 (en) * | 1997-06-24 | 1998-12-30 | Thomson-Csf | Method and device for modulation frequency correction with variable carrier frequency and several subcarriers |
US6104767A (en) * | 1997-11-17 | 2000-08-15 | Telefonaktiebolaget Lm Ericsson | Method and apparatus for estimating a frequency offset |
EP0930751A1 (en) * | 1998-01-19 | 1999-07-21 | Victor Company Of Japan, Limited | Method and apparatus for receiving orthogonal frequency division multiplexed signal |
EP0952713A2 (en) * | 1998-04-24 | 1999-10-27 | Nec Corporation | A frequency and timing synchronization circuit making use of a chirp signal |
US6498822B1 (en) | 1998-04-24 | 2002-12-24 | Nec Corporation | Frequency and timing synchronization circuit making use of a chirp signal |
EP0952713A3 (en) * | 1998-04-24 | 2002-07-03 | Nec Corporation | A frequency and timing synchronization circuit making use of a chirp signal |
AU755811B2 (en) * | 1998-05-01 | 2002-12-19 | Telefonaktiebolaget Lm Ericsson (Publ) | Search window delay tracking in code division multiple access communication systems |
WO1999057819A1 (en) * | 1998-05-01 | 1999-11-11 | Telefonaktiebolaget Lm Ericsson (Publ) | Search window delay tracking in code division multiple access communication systems |
US6396866B1 (en) * | 1998-05-01 | 2002-05-28 | Trw Inc. | Symmetric chirp communications acquisition method and apparatus |
US6731622B1 (en) | 1998-05-01 | 2004-05-04 | Telefonaktiebolaget Lm Ericsson (Publ) | Multipath propagation delay determining means using periodically inserted pilot symbols |
US6370397B1 (en) | 1998-05-01 | 2002-04-09 | Telefonaktiebolaget Lm Ericsson (Publ) | Search window delay tracking in code division multiple access communication systems |
WO2000002325A1 (en) * | 1998-07-01 | 2000-01-13 | Zenith Electronics Corporation | Receiver synchronizer using chirps sequences |
US6304619B1 (en) | 1998-07-01 | 2001-10-16 | Zenith Electronics Corporation | Receiver synchronizer |
US6418158B1 (en) | 1998-11-24 | 2002-07-09 | Hughes Electronics Corporation | Synchronization in mobile satellite systems using dual-chirp waveform |
WO2000031898A1 (en) * | 1998-11-24 | 2000-06-02 | Hughes Electronics Corporation | Acquisition mechanism for a mobile satellite system |
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Also Published As
Publication number | Publication date |
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SE9404356L (en) | 1996-06-15 |
SE9404356D0 (en) | 1994-12-14 |
SE504787C2 (en) | 1997-04-28 |
AU4275196A (en) | 1996-07-03 |
JPH10510958A (en) | 1998-10-20 |
KR980700750A (en) | 1998-03-30 |
CN1170486A (en) | 1998-01-14 |
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