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公开(公告)号：AT233451T
公开(公告)日：2003-03-15
申请号：AT97937935
申请日：1997-09-01
Applicant: ST MICROELECTRONICS NV
Inventor： ISAKSSON MIKAEL , JOHANSSON MAGNUS , TONVALL HARRY , OLSSON LENNART , STEFANSSON TOMAS , OEHMAN HANS , BAHLENBERG GUNNAR , ISAKSSON ANDERS , OEKVIST GOERAN , LJUNGGREN LIS-MARIE , NORDSTROEM TOMAS , ISAKSSON LARS-AKE , BENGTSSON DANIEL , HAKANSSON SIWERT , WEN YE
Abstract: A multi-carrier transmission system using orthogonal carriers with high order QAM constellations for the transmission of multiple bits per carrier and symbol. Such systems place high demands on the synchronization of the receiver with the transmitter. The maximum permitted deviation from exact synchronization is usually a small fraction of a sampling interval. A reserve carrier, the pilot carrier, which is given a fixed phase, is usually used as the reference to achieve this high accuracy. The receiver sampling clock oscillator is phase locked to the pilot carrier. It is therefore necessary to estimate the phase of the pilot carrier. Using a bandpass filter to recover the pilot carrier, regardless of the frame structure of the DMT signal, does not eliminate the influence of neighboring carriers on the pilot carrier.
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公开(公告)号：DE69718799D1
公开(公告)日：2003-03-06
申请号：DE69718799
申请日：1997-09-01
Applicant: ST MICROELECTRONICS NV
Inventor： ISAKSSON MIKAEL , JOHANSSON MAGNUS , TONVALL HARRY , OLSSON LENNART , STEFANSSON TOMAS , OEHMAN HANS , BAHLENBERG GUNNAR , ISAKSSON ANDERS , OEKVIST GOERAN , LJUNGGREN LIS-MARIE , NORDSTROEM TOMAS , ISAKSSON LARS-AKE , BENGTSSON DANIEL , HAKANSSON SIWERT , WEN YE
Abstract: A multi-carrier transmission system, such as a DMT system. A receiver must be able to recover a sampling clock that is very accurately synchronized to a transmitter sampling clock. Typically, synchronization is achieved by using a reserved carrier, the pilot carrier, which is transmitted with a fixed phase. The receiver sampling clock is then phase locked to the pilot carrier. Frame timing can be recovered by using a correlation technique. Thus an improved method of recovering a sample clock and phase locking the sampling clock to a pilot carrier is provided.
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公开(公告)号：DE69905040D1
公开(公告)日：2003-02-27
申请号：DE69905040
申请日：1999-05-11
Applicant: ST MICROELECTRONICS NV
Inventor： JOHANSSON MAGNUS , OLSSON LENNART , BAHLENBERG GUNNAR , BENGTSSON DANIEL , ISAKSSON MIKAEL , OLOFSSON SVEN-RUNE , OEKVIST GOERAN
Abstract: In a multi-carrier system employing OFDM, for example DMT, an adaptive channel equalizer is normally used, operating in the frequency domain. The sampling clock is controlled so that the time delay between the transmitter and the receiver is effectively eliminated. If the information used to control the sampling clock is received from the equalized data stream, it will introduce an ambiguity between the operation of the channel equalizer and the mechanism used to control the sampling clock. Operation of the equalizer can mask an increasing time difference, between transmitter and receiver, which the sample clock controller should be tracking. The present invention eliminates the ambiguities in the operation of the equalizer and sample clock controller by preventing the equalizer accepting time differences which should be corrected by operation of the sample clock controller.
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公开(公告)号：DE69810251D1
公开(公告)日：2003-01-30
申请号：DE69810251
申请日：1998-02-27
Applicant: ST MICROELECTRONICS NV
Inventor： OLSSON LENNART , BAHLENBERG GUNNAR , BENGTSSON DANIEL , HAKANSSON SIWERT , ISAKSSON ANDERS , ISAKSSON LARS-AKE , ISAKSSON MIKAEL , JOHANSSON MAGNUS , LAHTI MAURITZ , LJUNGGREN LIS-MARIE , LUNDBERG HANS , NORDSTROEM TOMAS , OLOFSSON SVEN-RUNE , STEFANSSON TOMAS , OEMAN HANS , OEKVIST GOERAN
Abstract: With OFDM systems the frequency domain data is the Fourier transform of the received time domain OFDM frames. The time domain frames must be sampled, at the receiver, in synchronism with the transmitter, so that each received frame contains data from only a single transmitted frame. It is vital for this synchronism to be maintained in order to maintain the orthogonality of the frames. A typical multi-carrier system, of the OFDM type, which uses a cyclic prefix permits orthogonality to be maintained when there is a small deviation from exact frame synchronisation. Because the signalling interval includes both an entire frame and the cyclic prefix, which is a repetition of part of the frame, a frame sampled within the signalling interval will contain data from only one frame. Since the signalling interval is greater than the frame period, this gives some leeway in frame alignment. In a multi-carrier system of the OFDM type, an adaptive channel equalizer, operating in the frequency domain, is often used. The internal parameters in such an equalizer contain, in addition to information about the characteristics of the channel, information which can be interpreted as the time deviation between the sampling clocks of the transmitter and the receiver. The present invention utilizes this information to control the sampling clock of the receiver in a more robust way than has previously been possible with known techniques. The present invention is particularly suitable for use in ADSL and VDSL modems which can be used to give broadband access over copper networks. The invention is also of relevance to broadband transmission in mobile and semi-mobile systems for transmission over the radio channels.
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公开(公告)号：DE69904026D1
公开(公告)日：2003-01-02
申请号：DE69904026
申请日：1999-01-28
Applicant: ST MICROELECTRONICS NV
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Patent Agency Ranking
公开(公告)号：DE69717285D1
公开(公告)日：2003-01-02
申请号：DE69717285
申请日：1997-09-01
Applicant: ST MICROELECTRONICS NV
Inventor： ISAKSSON MIKAEL , JOHANSSON MAGNUS , TONVALL HARRY , OLSSON LENNART , STEFANSSON TOMAS , OEHMAN HANS , BAHLENBERG GUNNAR , ISAKSSON ANDERS , OEKVIST GOERAN , LJUNGGREN LIS-MARIE , NORDSTROEM TOMAS , ISAKSSON LARS-AKE , BENGTSSON DANIEL , HAKANSSON SIWERT , WEN YE
Abstract: A multi-carrier transmission system such as a DMT based VDSL system. The system uses orthogonal carriers with high order QAM constellations for the transmission of multiple bits per carrier and symbol. This estimate includes digital receiver and transmitter units with the receiver unit including a symbol detection unit. This system is adapted to determine a parameter for each single carrier with the parameter being indicative of a deviation of a received signal from a corresponding constellation point. It compares the parameter with an upper lower limit and if the parameter is outside the limits, changes the constellation used to modulate the carrier to a neighboring constellation. The symbol detection unit may be used to determine a parameter such as the ratio d2/sigma2, where d is the shortest distance between neighboring constellations, sigma is a standard deviation and sigma2 is the variance of the deviations of the input and output signal values of the symbol detection unit.
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公开(公告)号：AT227912T
公开(公告)日：2002-11-15
申请号：AT97937936
申请日：1997-09-01
Applicant: ST MICROELECTRONICS NV
Inventor： ISAKSSON MIKAEL , JOHANSSON MAGNUS , TONVALL HARRY , OLSSON LENNART , STEFANSSON TOMAS , OEHMAN HANS , BAHLENBERG GUNNAR , ISAKSSON ANDERS , OEKVIST GOERAN , LJUNGGREN LIS-MARIE , NORDSTROEM TOMAS , ISAKSSON LARS-AKE , BENGTSSON DANIEL , HAEKANSSON SIWERT , WEN YE
Abstract: A two-way multi-carrier transmission system, such as a DMT system. If there are dynamic changes in the transmission parameters, synchronization must be maintained between the transmitter and the receiver when the transmission parameters changed. The first stage of such a process requires that the changes of parameter be notified by one transceiver to others involved in an active communication process over a slow transmission channel such as the control channel. Subsequently, the synchronization transceiver is adjusted simultaneously, i.e., from a predetermined DMT symbol. Such adjustments in time synchronization must be achieved with a minimum of overhead.
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公开(公告)号：DE69807486D1
公开(公告)日：2002-10-02
申请号：DE69807486
申请日：1998-06-10
Applicant: ST MICROELECTRONICS NV
Inventor： OLOFSSON SVEN-RUNE , JOHANSSON JOACHIM , ISAKSSON MIKAEL , OEHMAN HANS , BENGTSSON DANIEL , OLSSON LENNART , ISAKSSON ANDERS , OEKVIST GOERAN , LJUNGGREN LIS-MARI , LUNDBERG HANS , STEFANSSON TOMAS , BAHLENBERG GUNNAR , HAKANSSON SIVERT , JOHANSSON MAGNUS
Abstract: An arrangement for synchronization of nodes in VDSL-systems, or more exactly, synchronization of optical VDSL-nodes which share a common part of a cable in the access network between subscribers and a local station. A time synchronization is provided towards an external system, for instance GPS, which gives a time reference by which the different nodes can be synchronized. The synchronization reduces the near end cross-talk between the VDSL-systems in the different nodes. Preferably, each respective node includes a receiver for a synchronization signal and an internal oscillator with high stability to deliver a stable clock signal.
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公开(公告)号：DE69912148T2
公开(公告)日：2004-07-08
申请号：DE69912148
申请日：1999-11-18
Applicant: ST MICROELECTRONICS NV
Inventor： SJOEBERG FRANK , WILSON KATE , NILSSON RICKARD , BENGTSSON DANIEL , ISAKSSON MIKAEL , NORDSTROEM TOMAS , OEDLING PER , BAHLENBERG GUNNAR , JOHANSSON MAGNUS , OLSSON LENNART , OEKVIST SVEN-GOERAN
IPC: H04J11/00 , H04B3/04 , H04B3/32 , H04L29/10 , H04M20060101
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公开(公告)号：DE69910015D1
公开(公告)日：2003-09-04
申请号：DE69910015
申请日：1999-05-11
Applicant: ST MICROELECTRONICS NV
Inventor： BOERJESSON OLA , ISAKSSON MIKAEL , OEDLING PER , BENGTSSON DANIEL , BAHLENBERG GUNNAR , JOHANSSON MAGNUS , OLSSON LENNART , OEKVIST GOERAN
IPC: H03M1/12
Abstract: A circuit, for digitizing an analogue signal includes an analogue to digital converter, a clip processor adapted to estimate a value for clipped digital signal samples, and a buffer adapted to dynamically store a plurality of digitized samples produced by the analogue to digital converter. The clip processor is adapted to read digitized samples from the buffer and replace clipped digitized samples with the estimated values, thereby mitigating the effects of clipping in an output of the circuit.
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