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    31.
    发明专利
    未知

    公开(公告)号：NO985029D0

    公开(公告)日：1998-10-29

    申请号：NO985029

    申请日：1998-10-29

    Applicant: TELIA AB

    Inventor： OLSSON LENNART ,  BAHLENBERG GUNNAR ,  BENGTSSON DANIEL ,  HOKANSSON SIWERT ,  ISAKSSON ANDERS ,  ISAKSSON LARS-KE ,  ISAKSSON MIKAEL ,  JOHANSSON MAGNUS ,  LAHTI MAURITZ ,  LJUNGGREN LIS-MARIE ,  LUNDBERG HANS ,  NORDSTR M TOMAS ,  OLOFSSON SVEN-RUNE ,  STEFANSSON TOMAS ,  IMAN HANS ,  IKVIST G RAN

    IPC: H04L27/26 ,  H04L

    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.

    33.
    发明专利
    未知

    公开(公告)号：SE9801150D0

    公开(公告)日：1998-04-01

    申请号：SE9801150

    申请日：1998-04-01

    Applicant: TELIA AB

    Inventor： ISAKSSON MIKAEL ,  BENGTSSON DANIEL ,  SJOEBERG FRANK ,  OEDLING PER ,  NILSSON RICKARD ,  BAHLENBERG GUNNAR ,  JOHANSSON MAGNUS ,  OLSSON LENNART ,  OEKVIST SVEN GOERAN

    IPC: H04L5/14 ,  H04L27/26 ,  H04M

    Abstract: Zipper is the time-synchronized frequency-division duplex implementation of discrete multi-tome (DMT) modulation. Two communicating Zipper modems transmit DMT symbols simultaneously with a common clock. When all transmitters are time synchronized, the near end cross-talk (NEXT) and near end echoes injected into the received signal are orthogonal to the desired signal. The present invention provides a telecommunications transmission system using zipper and having at least two VDSL systems. Each VDSL system comprises a pair of zipper modems communicating over a cable transmission path. The telecommunications transmission system handles zipper transmission transmitted over the common cable; at least partly mitigates NEXT; and permits transmissions in a first VDSL system which are asynchronous with transmissions in a second VDSL system.

    34.
    发明专利
    未知

    公开(公告)号：SE9700905D0

    公开(公告)日：1997-03-13

    申请号：SE9700905

    申请日：1997-03-13

    Applicant: TELIA AB

    Inventor： THOLIN PER ,  BAHLENBERG GUNNAR ,  DILLNER ERIK ,  JOHANSSON MAGNUS ,  LJUNGGREN LIS-MARIE ,  TONWALL HARRY ,  WESTER PER-OLA

    IPC: H04L20060101 ,  H04L47/43 ,  H04N19/89 ,  H04L

    Abstract: The MPEG-2 decoding system has an MPEG-2 decoder and a video and audio decoder. The MPEG-2 decoder has a system layer demultiplexer and a mechanism for adding a status byte prior to the transmission of an ATM adaptive layer (AAL) payload to the system layer demultiplexer. A bit of the status byte acts as an ATM cell loss flag. The system level demultiplexer on receipt of the status byte with the ATM cell loss flag to the video and/or audio decoder. The MPEG-2 decoder employs AAL1. The video and/or audio decoder on receipt of a cell loss flag switches to an error concealment mode.

    35.
    发明专利
    未知

    公开(公告)号：SE514016C2

    公开(公告)日：2000-12-11

    申请号：SE9801150

    申请日：1998-04-01

    Applicant: TELIA AB

    Inventor： ISAKSSON MIKAEL ,  BENGTSSON DANIEL ,  SJOEBERG FRANK ,  OEDLING PER ,  NILSSON RICKARD ,  BAHLENBERG GUNNAR ,  JOHANSSON MAGNUS ,  OLSSON LENNART ,  OEKVIST SVEN GOERAN

    IPC: H04L5/14 ,  H04L27/26 ,  H04L5/06

    Abstract: Zipper is the time-synchronized frequency-division duplex implementation of discrete multi-tome (DMT) modulation. Two communicating Zipper modems transmit DMT symbols simultaneously with a common clock. When all transmitters are time synchronized, the near end cross-talk (NEXT) and near end echoes injected into the received signal are orthogonal to the desired signal. The present invention provides a telecommunications transmission system using zipper and having at least two VDSL systems. Each VDSL system comprises a pair of zipper modems communicating over a cable transmission path. The telecommunications transmission system handles zipper transmission transmitted over the common cable; at least partly mitigates NEXT; and permits transmissions in a first VDSL system which are asynchronous with transmissions in a second VDSL system.

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