Abstract: For synchronisation purposes, a transmitter (TX) multiplexes a pilot carrier with carriers whereon data elements (DATA) are modulated, and transmits the pilot carrier together with the modulated carriers to a receiver (RX). The immunity of the pilot carrier for interferers, such as radio amateur signals, is improved by modulating the pilot carrier with a non-constant signal, for instance a random signal, an alternating signal or even scrambled data elements (DATA), before transmission thereof. Since demodulation of the pilot carrier in the receiver (RX) and averageing successive demodulated pilot carriers reduces the effect of the interference induced on the non-constantly modulated pilot carrier, the degradation of the synchronisation between transmitter (TX) and receiver (RX) is reduced significantly.

Abstract: In a telephone system where frequency multiplexed analog telephone signals and digital data signals are transmitted over a line, incoming calls are announced to the customer installation by a ringing indication signal having an amplitude between 1 and 30 V RMS, which is much less than the regular ringing and therefore easier to be generated, and moreover having a smoother shape than a rectangular shape. Upon receiving the ringing indication signal, the customer installation locally generates and provides a full ringing signal to a telephone. The amplitude of this local ringing signal is higher than the amplitude of the ringing indication signal, but the line with the digital data signal is isolated from the customer telephone equipment at the time the ringing signal is generated, so as to avoid disturbance of the digital data transmission by the ringing current, which is a source of impulsive noise.

Abstract: For synchronization purposes, a transmitter (TX) multiplexes a pilot carrier with carriers whereon data elements (DATA) are modulated, and transmits the pilot carrier together with the modulated carriers to a receiver (RX). The immunity of the pilot carrier for interferers, such as radio amateur signals, is improved by modulating the pilot carrier with a non-constant signal, for instance a random signal, an alternating signal or even scrambled data elements (DATA), before transmission thereof. Since demodulation of the pilot carrier in the receiver (RX) and averaging successive demodulated pilot carriers reduces the effect of the interference induced on the non-constantly modulated pilot carrier, the degradation of the synchronization between transmitter (TX and receiver (RX) is reduced significantly.

Abstract: In a full power state, data packet are transferred at full power from a transmitter to a receiver, whereas in a low power state data packet s are transferred at low power from the transmitter to the receive. To transit fast from the low power state to the full power state, the transmitter interrupts transmission of the currently transmitted low power data symbol and transmits a copy of the currently transmitted low power symbol at full power to the receiver.

Abstract: A filter arrangement particularly adapted to be used in a “splitter” of an ADSL system where several POTS equipment, e.g., subscriber sets, are connected to a same telecommunication line. The arrangement, located at the customer premises, includes for each POTS equipment a distinct low-pass filter circuit to separate low frequency POTS signals from high frequency ADSL signals simultaneously transmitted over the same copper twisted-pair telecommunication line. Each low-pass filter circuit is provided with a current sensing circuit, e.g., an electrical relay, which activates a switch when the current flowing through the filter exceeds a predetermined value. Since several high order filter circuits can not be put in parallel, mainly because their capacitive values will then add, the present filter circuit is basically a 1st order filter that comprises the series connection of two transformers separated by the coil of the relay. When the current increases, i.e.

Abstract: A time error compensation arrangement (TCOMP) that compensates for a time error (&egr;, &Dgr;k) between a transmitter sample clock in a multi-carrier transmitter and a receiver sample clock (CLK) in a multi-carrier receiver (RX1, RX2) includes a digital time correction filter (FILTER, FILTER′), operative in time domain, to compensate for a linearly increasing contribution (&Dgr;k) in the time error (&egr;, &Dgr;k) and rotation means (ROTOR), operative in frequency domain, to compensate for a second, remaining contribution (&egr;) in said time error (&egr;, &Dgr;k).

Abstract: An apparatus for use in an all digital loop contains a first network node (30), a second network node (31), and a data transmission line (32) there between. Each one of the first and second network nodes (30, 31) is operable to transmit to the other at least one digitised telephone signal with other digital data via a set of carriers. One of the first and second network nodes (30, 31) thereto includes or is associated with means which in the event of power failure at the first network node (30), is operable selectively to provide power to the first node (30) such that the first node (30) operates only via a limited subset of said carriers. This limited subset is such as to minimise the power required for the transmission of a telephone lifeline signal between the first and second nodes (30, 31).

Abstract: For synchronization purposes, a transmitter (TX) multiplexes a pilot carrier with carriers whereon data elements (DATA) are modulated, and transmits the pilot carrier together with the modulated carriers to a receiver (RX). The immunity of the pilot carrier for interferers, such as radio amateur signals, is improved by modulating the pilot carrier with a non-constant signal, for instance a random signal, an alternating signal or even scrambled data elements (DATA), before transmission thereof. Since demodulation of the pilot carrier in the receiver (RX) and averaging successive demodulated pilot carriers reduces the effect of the interference induced on the non-constantly modulated pilot carrier, the degradation of the synchronization between transmitter (TX and receiver (RX) is reduced significantly.

Abstract: In a multicarrier transmission system, a transmitter (T, T′) sends digital data packets (D) modulated on a set of carriers to a receiver (R, R′). A subset of the carriers constituting the set of carriers has frequencies (f1, f2, f3, f4) in predetermined frequency ranges (Amateur Radio Band) with high risk for being affected by narrowbanded interference (RFI), e.g. originating from radio amateur transmission. The data bits of the digital data packets (D) that are allocated to the subset of carriers having frequencies (f1, f2, f3, f4) within these predetermined frequency ranges (Amateur Radio Band), are allocated thereto in a redundant way. Via an allocation message (AM) communicated between the transmitter (T, T′) and the receiver (R, R′) both are aware of the redundancy in the bit allocations.

Abstract: For synchronisation purposes, a transmitter (TX) multiplexes a pilot carrier with carriers whereon data elements (DATA) are modulated, and transmits the pilot carrier together with the modulated carriers to a receiver (RX). The immunity of the pilot carrier from interference, such as radio amateur signals, is improved by modulating the pilot carrier with a non-constant signal, for instance a random signal, an alternating signal or even scrambled data elements (DATA), before transmission thereof. Since demodulation of the pilot carrier in the receiver (RX) and averaging successive demodulated pilot carriers reduces the effect of the interference induced on the non-constantly modulated pilot carrier, the degradation of the synchronisation between transmitter (TX) and receiver (RX) is reduced significantly.

Abstract: In a multicarrier transmission system, a transmitter (T, T′) sends digital data packets (D) modulated on a set of carriers to a receiver (R, R′). A subset of the carriers constituting the set of carriers has frequencies (f1, f2, f3, f4) in predetermined frequency ranges (Amateur Radio Band) with high risk for being affected by narrowbanded interference (RFI), e.g. originating from radio amateur transmission. The data bits of the digital data packets (D) that are allocated to the subset of carriers having frequencies (f1, f2, f3, f4) within these predetermined frequency ranges (Amateur Radio Band), are allocated thereto in a redundant way. Via an allocation message (AM) communicated between the transmitter (T, T′) and the receiver (R, R′) both are aware of the redundancy in the bit allocations.

Abstract: An apparatus for use in an all digital loop contains a first network node (30), a second network node (31), and a data transmission line (32) there between. Each one of the first and second network nodes (30, 31) is operable to transmit to the other at least one digitised telephone signal with other digital data via a set of carriers. One of the first and second network nodes (30, 31) thereto includes or is associated with means which in the event of power failure at the first network node (30), is operable selectively to provide power to the first node (30) such that the first node (30) operates only via a limited subset of said carriers. This limited subset is such as to minimise the power required for the transmission of a telephone lifeline signal between the first and second nodes (30, 31).

Abstract: A pipelined Fast Fourier Transform Processor includes, besides a memory arrangement, a cascade of a first arithmetic unit, a scratch memory and a second arithmetic unit. One of both arithmetic units can only perform at least one type of butterfly Fast Fourier Transform arithmetic calculations, whereas the other one can perform, besides this at least one type of butterfly Fast Fourier Transform arithmetic calculations, at least one second type of butterfly Fast Fourier Transform arithmetic calculations. This architecture optimises both timing as well as circuit restrictions.

Abstract: A telecommunication transmitter (TU) for a multi-carrier transmission system of the Digital Subscriber Line [DSL] type and which includes a coding circuit (MMC) able to generate “symbols” derived from carriers (Cl-Cn) modulated by incoming data, and a line driver circuit (LDC) to amplify these symbols. When idle data are received, the power dissipated in the transmitter is reduced because the symbols are then merely derived from a few or even a single carrier (the “pilot tone”) instead as from all the available carriers. The power dissipated is even more reduced because the line driver circuit is formed by a parallel connection of a high voltage but low efficiency (LL) and a lower voltage but higher performance (LH) line amplifier. The higher performance, and thus less power consuming, amplifier (LH) is used when idle data are received at the input (IN).

Abstract: A windowing unit (WFU) improves band-limited noise immunity of a fourier transformer (FT) of which it is a part. The windowing unit (WFU) comprises a digital window filter (WI) and a folding processor (F). The window function (W) of the digital window filter (WI) consists of a window head (HEAD), a window body (BODY), and a window tail (TAIL), and the shape of the window function (W) is chosen so that the window head (HEAD) is complementary to a tail (BODY TAIL) of a window body (BODY), and similarly the window tail (TAIL) is complementary to a head (BODY HEAD) of the window body (BODY). The folding processor (F) performs the task of mapping the information received in the window head (HEAD) on to the tail (BODY TAIL) of the window body (BODY) and mapping the information received in the window tail (TAIL) on to the head (BODY HEAD) of the window body (BODY).

Abstract: A modulator/demodulator (MODEM) is equipped with a rotation circuit (TROT) in its transmitting part (TP) and a rotation circuit (RROT) in its receiving part (RP). To compensate for clock speed differences between the clocks of two communicating modems, the receive rotation circuit (RROT) of one of them rotates the phase of received data carriers in proportion to their respective frequencies. Furthermore, to align transmit data symbols with received data symbols, the transmit rotation circuit (TROT) of one of the modems rotates the phase of the transmit data symbols. Thereto, the phase rotation applied to each carrier whereon the transmit data symbols are modulated, is proportional to the frequency of this carrier and to a phase difference measured between a received pilot carrier (PT) and an expected received pilot carrier (PT.sub.-- E).

Abstract: The present invention concerns a signal processor module (SPU,AVF) which is adapted to check if a received vector (RV) representing a received signal in a QAM signal vector plane is located in the intersection zone of a first and second zone (ABCDEF,ab) of this signal vector plane. The intersection zone is well chosen so that the phase angle difference (Da) between the received vector (RV) and an expected vector (EV) which represents a signal which should have been received instead of the received signal and which is located in the intersection zone, is limited.