公开(公告)号：EE9900579A

公开(公告)日：2000-08-15

申请号：EEP9900579

申请日：1998-06-10

Applicant: TELIA AB

Inventor： SVEN-RUNE OLOFSSON ,  JOACHIM JOHANSSON ,  MIKAEL ISAKSSON ,  HANS OEHMAN ,  DANIEL BENGTSSON ,  LENNART OLSSON ,  ANDERS ISAKSSON ,  GAERAN OEKVIST ,  LIS-MARI LJUNGGREN ,  HANS LUNDBERG ,  TOMAS STEFANSSON ,  GUNNAR BAHLENBERG ,  SIWERT HAAKANSSON ,  MAGNUS JOHANSSON

IPC: H04J11/00 ,  H04L1/00 ,  H04L29/10 ,  H04M11/00 ,  H04M11/06

Abstract: A VDSL-modem which is divided into an analog part which is placed in an optical node and a digital part which is placed in a local station. The analog part of the VDSL-modem includes an A/D-converter and D/A-converter, a filter, an amplifier, a hybrid/balun, an adaptive noise attenuator, an optical interface, and possibly an echo canceller. The digital part of the modem includes an FFT/IFFT-processor, a synchronizer, an equalizer, an interleaving unit, an error correction unit, a protocol manager, and an optical interface. The VDSL-modem simplifies synchronization of the modem and reduces power consumption in the optical node. A multiplexor function in the optical node in addition is simpler because it need not manage a protocol.

公开(公告)号：EE9900609A

公开(公告)日：2000-08-15

申请号：EEP9900609

申请日：1998-06-10

Applicant: TELIA AB

Inventor： SVEN-RUNE OLOFSSON ,  JOACHIM JOHANSSON ,  MIKAEL ISAKSSON ,  HANS OEHMAN ,  DANIEL BENGTSSON ,  LENNART OLSSON ,  ANDERS ISAKSSON ,  OEKVIST GAERAN ,  LJUNGGREN LIS-MARI ,  LUNDBERG HANS ,  STEFANSSON TOMAS ,  BAHLENBERG GUNNAR ,  HAAKANSSON IWERT ,  JOHANSSON MAGNUS

IPC: H04B10/00 ,  H04J3/06 ,  H04L7/00 ,  H04N1/00 ,  H04L7/08

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.

公开(公告)号：SE511521C3

公开(公告)日：1999-11-22

申请号：SE9704256

申请日：1997-11-18

Applicant: TELIA AB

Inventor： MIKAEL ISAKSSON ,  MAGNUS JOHANSSON ,  LENNART OLSSON ,  TOMAS STEFANSSON ,  HANS OEHMAN ,  BAHLENBERG KJELL G ,  ISAKSSON ANDERS I ,  OEKVIST SVEN G ,  LJUNGGREN KARIN L-M ,  DANIEL BENGTSSON ,  SVEN-RUNE OLOFSSON ,  JOACHIM JOHANSSON ,  BOERJESSON PER O ,  NIKLAS GRIP ,  RICKARD NILSSON ,  FRANK SJOEBERG ,  WILSON SARAH K ,  PER OEDLING

IPC: H04B1/12 ,  H04B15/00 ,  H04B3/32 ,  H04L25/10 ,  H04L27/26

Abstract: A RFI canceller, for use in a subscriber line system using multi-carrier modulation, measures a RFI disturbance in carriers falling within a band of frequencies causing the RFI. The RFI ingress into carriers outside the band of frequencies is estimated, and an error correcting signal derived from the estimation of the RFI ingress is subtracted from a received signal. The subscriber line system may be a VDSL system and the multi-carrier modulation may be DMT. The RFI canceller includes a demodulator for demodulating an incoming data stream to provide a first parallel data stream. A parallel to serial convertor converts the first parallel data stream to a first serial data stream. A digital to analogue convertor converts the first serial data stream to a first analogue signal. An analogue RFI canceller circuit combines the analogue signal with an analogue error correcting signal, to produce a second analogue signal. An analogue to digital convertor converts the second analogue signal to a second serial data signal. A serial to parallel convertor converts the second serial data stream to a second parallel data stream. A modulator modulates the second parallel data stream onto a multiplicity of carriers.

公开(公告)号：EE9800374A

公开(公告)日：1999-04-15

申请号：EEP9800374

申请日：1998-02-27

Applicant: TELIA AB

Inventor： LENNART OLSSON ,  GUNNAR BAHLENBERG ,  DANIEL BENGTSSON ,  SIWERT HAAKANSSON ,  ANDERS ISAKSSON ,  LARS-KE ISAKSSON ,  MIKAEL ISAKSSON ,  MAGNUS JOHANSSON ,  MAURITZ LAHTI ,  LIS-MARI LJUNGGREN ,  HANS LUNDBERG ,  TOMAS NORDSTRAEM ,  SVEN-RUNE OLOFSSON ,  TOMAS STEFANSSON ,  HANS OEHMAN ,  GAERAN OEKVIST

IPC: H04L27/26 ,  H04L5/06

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.

公开(公告)号：EE9800375A

公开(公告)日：1999-04-15

申请号：EEP9800375

申请日：1998-02-27

Applicant: TELIA AB

Inventor： LENNART OLSSON ,  GUNNAR BAHLENBERG ,  DANIEL BENGTSSON ,  SIWERT HAAKANSSON ,  ANDERS ISAKSSON ,  LARS-KE ISAKSSON ,  MIKAEL ISAKSSON ,  MAGNUS JOHANSSON ,  MAURITZ LAHTI ,  LIS-MARI LJUNGGREN ,  HANS LUNDBERG ,  TOMAS NORDSTRAEM ,  SVEN-RUNE OLOFSSON ,  TOMAS STEFANSSON ,  HANS OEHMAN ,  GAERAN OEKVIST

IPC: H04L27/26 ,  H04L5/22

Abstract: A mechanism for achieving frame synchronization in the frequency domain. In order to synchronize a receiver with a transmitter, on signal acquisition, the interval in which orthogonality exists is determined. Once this has been achieved, an argument function is calculated from the received frame. This argument function can then be used to improve the synchronization. This system is particularly suitable for use in ADSL and VDSL modems which can be used to give broad band access over copper networks. It is also relevant to broad band transmission in mobile and semi-mobile systems for transmission over radio channels.