British Telecommunications Public Limited Company

British Telecommunications Corporation

John Wolsey Cook

Christopher Marcus Croot

Trevor Philip Linney

Ashley Pickering

Philip Antony Everett

Philip Anthony Everett

Robert H Kirkby

A method of operating an access network including a plurality of data connections () between end-user devices () and an aggregation transceiver device () at which the connections () are aggregated for onward connection through the access network, the method comprising storing a plurality of different profiles, each profile specifying values for parameters associated with each connection (); and, for each connection, obtaining connection data relating to a monitoring period, said monitoring period comprising a plurality of shorter periods, said connection data comprising, for each of said shorter periods, an indication of whether said connection has experienced instability during said shorter period, and an indication of user activity on said connection during said shorter period; monitoring the performance of the connection in dependence on said connection data; selecting one of said stored profiles to be applied to the connection in dependence on the results of said monitoring; and applying the selected profile to the connection.

Data communication

A Digital Subscriber Line Access Multiplexor (DSLAM) for operation within an access network includes a plurality of digital subscriber line modems for terminating a plurality of corresponding digital subscriber lines and aggregating them for onward connection through the access network. The DSLAM is operable, each time a data connection is established or re-established over one of the digital subscriber lines, to generate line data about the data connection at the DSLAM, to store the line data, to wait a predetermined period of time, to determine if the data connection is still operating successfully since the establishment of the connection without having suffered loss of connection during the predetermined period and then to transmit the line data to a management device which performs dynamic line management based on the data.

Dynamic line management of digital subscriber line connections

In a method and system for operating an ADSL access network which has a plurality of data connections () between the access network and end user devices (), and in which the access network controls the rate at which data is transferred between the user devices and an onward connection (), the access network stores a plurality of capped profiles each of which specifies a respective upper data rate to which the connection is limited and which is below the maximum achievable rate for the connection. The access network operates using a Dynamic Line Management (DLM) algorithm which, for a given data connection, operates to enable data transfer at a variable data rate up to the maximum rate, monitors the error performance and signal to noise margin variation for different data rates and, in the event that one or both are outside respective limits for a predetermined period, selects and applies one of the capped profiles to limit the upper data rate, selection being determined by the highest data rate achieved for which the error performance was within acceptable limits.

Data communications

A management device for use in an access network including a plurality of data connections between end user devices and an aggregation transceiver device where the connections are aggregated for onward connection through the access network, the access network storing in association with each data connection a Dynamic Line Management, DLM, profile which specifies a set of values for a plurality of parameters associated with the respective data connection, together with a stability level specifying a desired level of stability for the data connection. The device comprises means for receiving monitoring data specifying the stability of each respective data connection over a predetermined period of time; means for selecting a DLM profile to be applied to the connection in dependence on both the monitoring data and the stored stability level associated with the data connection; and means for requesting an OSS system of the access network to apply the selected profile to the data connection.

Monitoring data communications in an access network

Multiple carriers are generated, modulated by data to be transmitted, as shown by oscillators and modulators (or using Fourier transform techniques). They follow two paths. One path via an adder takes a set of carriers at integer multiples of a windowing frequency where the odd carriers have some reference phase and the even carriers are in phase quadrature. The other path via an adder takes a second set of carriers, again at integer multiples of the windowing frequency. The even carriers have a reference phase and the odd carriers are in phase quadrature therewith. In the first path, the signal is multiplied by a windowing function with a period equal to the reciprocal of the windowing frequency. In the second path, the signal is multiplied by a similar function which is time-shifted (by a delay) by half of the period.

Multicarrier modulation

Carrierless signals of first and second channels pass via filters having quadrature responses and are then added for transmission. A receiver uses adaptive filters which also need quadrature responses to separate the channels effectively. To accommodate misconvergence of the filters giving rise to (a) inverted responses, (b) differential delays, (c) similar or identical responses and/or (d) transposed responses, --and hence incorrect decoding: (a) the transmitter and receiver may employ different coding in each channel, (b) the receiver may calculate the group delay of its filters and correct any error, (c) the receiver may compare the filtered signals and if similar replace one filter response with a quadrature response calculated from the other and/or (d) the receiver may respond to a failure to recognize expected synchronization words by transposing the responses of the filters.

Transmitting digital signals

A phase shifter system includes a number of gates 40, 41 for receiving a reference clock and a number of gates 30-33 for receiving a predicted desired phase. The reference clock is manipulated by latches 43-46 and further gates 48, 49 so as to produce quadrature derivatives and these are connected across the resistor chain R1-R9 to produce multilevel waveforms, the steps being selected by selector 36 connected to the resistor nodes under the control of the predicted phase information from gates 30-33. Filtering and reshaping via comparator 50 provides an output clock pulse of desired phase. The output clock can be used to provide phase control in a transmission/reception system on a communications network.

Generation of phase shifted clock using selected multi-level reference

A twisted-pair telephone line is connected to a conventional telephone via a low-pass filter and equipment for receiving signals in an upper frequency range, e.g., 25-1000 kHz via a high-pass filter. The low-pass filter is primarily passive (to allow passage of line power, ringing and signalling voltages) but, to improve matching to non-resistive line and telephone impedances, at least the main part of the filter is flanked by impedance convertors in which amplifiers having an appropriate transfer function feed voltages back into the line via transformers through which power, ringing and dialing may pass unimpeded.

Two port signalling voltages filter arrangement

Interface circuit

An oscillating input signal is applied to the 4-wire input terminals which is monitored while the 4-wire output terminals and the 2-wire terminals are also monitored. This procedure is performed with a first known reference impedance connected across the 2-wire terminals and then repeated with a second reference impedance similarly connected. A plurality of input frequencies may be applied over the range of 400 Hz to 4000 Hz.

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Ipswich, United Kingdom

John Wolsey Cook