Stmicroelectronics N.v.

Stmicroelectronics S.a.

Telia Ab

Sven-Rune Olofsson

Lennart Olsson

Mikael Isaksson

Daniel Bengtsson

Magnus Johansson

Gunnar Bahlenberg

Anders Isaksson

Tomas Stefansson

Goran Okvist

Lis-Marie Ljunggren

Hans Ohman

Joachim Johansson

Hans Lundberg

Tomas Nordstrom

Lars-Ake Isaksson

Siwert Hakansson

Mauritz Lahti

Per Odling

Hans Oman

Lis-Mari Ljunggren

Bo Engstrom

Sarah Kate Wilson

Roger Larsson

Christer Ostberg

Sven-Göran Ökvist

Siwert H&aring;kansson

Michael Unneback

Hans &Ouml;hman

G&ouml;ran &Ouml;kvist

Sivert H&aring;kansson

Goran Oqvist

Niklas Grip

Per Ola Borjesson

Richard Nilsson

Hans Lungberg

Franck Sjöberg

Petra Dentgen

Sven Göeran Öekvist

Mikael R Isakssaon

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.

Telecommunications transmission systems

When delivering a broadband service, such as xDSL, without inband POTS, it is necessary to separate the analogue POTS signal and the xDSL signal from each other at both the CO (Central Office) and the CP (Customer's Premises). This can be achieved by using an active POTS splitter. The present invention incorporates test functionality for the line between the CP and the CO, or ONU (Optical Network Unit), in the POTS splitter. This enables two-sided measurements on the line, both during installation and during operation. The measurements are performed at the CO and upon request, or when the test device automatically sends a test message/signal. In this way there is no need for field technicians at the CP side. The POTS splitter can have a unique identity code that is transmitted to the CO each time a test is started, or on receipt of a request from the CO.

Telecommunications

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 from accepting time differences which should be corrected by operation of the sample clock controller.

The hybrid circuit can be used to substantially reduce near echo signals. The circuit includes a balanced 2-wire to 4-wire hybrid for interconnecting a two wire receive path and a two wire transmit path to a two wire transmission line. The two wire receive path connects the balanced hybrid to an A/D converter and the two wire transmit path connects a D/A converter to the balanced hybrid. The two wire receive path contains a filter, dimensioned to remove signals transmitted from the D/A converter. The invention is particularly adapted for use with FDD and OFDD.

Near-echo suppression

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.

VDSL modem divided into a digital and an analog part

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.

Synchronisation

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.

Subscriber line transmission systems

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.

Arrangement for synchronization of nodes in VDSL-systems

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.

Synchronization

Method for synchronization of transmitter and receiver at mobile radio

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Lulea, Sweden

Sven-Rune Olofsson