Multi-carrier modem transmitter with controlled transmit signal quality degradation

Abstract

A telecommunication system with a modem (MCO) having a controlling module (CCO) coupled to a data transmission module (DTM) comprising a transmitter (TX) adapted to transmit channels via a communication line (LN), the channels transporting user data (UD) by means of signals (STX) with modulation having a bitload that is modifiable. The data transmission module comprises an artificial noise generator (ANG) coupled to the transmitter and controlled by the controlling module to inject an artificial noise (AN) into the transmitter. The artificial noise is used to influence the signals transmitted by the data transmission module to the communication line and may be added to the data signals either in the transmit time domain processing module (TXTDP) or in the transmit frequency domain processing module (TXFDP) of the transmitter. The system is particularly advantageous for DSL applications where the margin is larger than 3 dB. This corresponds to distances lower than 4000 meter for an ADSL cable with 50 users.

Description

technical field [0001] The invention relates to a telecommunication system with a modem having a control module connected to a data transmission module comprising a transmitter suitable for transmitting via a communication line at least one channel suitable for transmission by means of a modulated signal To transmit user data, the modulation has a variable bitload. Background technique [0002] Such telecommunication systems with modems capable of operating with different bit loads / data rates are generally known in the prior art. Wherein the bit load / data rate is based on the current channel conditions, usually due to size. [0003] The "bit load" will be defined later. If the modulation is baseband modulation (BBM) or single carrier modulation (SCM), the bit loading corresponds to the number of information bits per modulation symbol, also called modulation or signaling slot. If the modulation is multi-carrier modulation (MCM), the bit loading corresponds to a set of numb...

AI Technical Summary

Problems solved by technology

However, in some crosstalk situations where the noise conditions change rapidly, the proposed solution is too slow to react in time to avoid bit errors and / or avoid reinitialization

The reason for this is that the crosstalk noise from the newly switched on xDSL modem increases the instantaneous value

[0016] A second known solution that can limit the modem's vulnerability to rapidly increasing noise levels that may be missing at initialization time is to use an a priori determined limit on some maximum data rate

Due to the dependence on other xDSLs present in the cable or communication line and the varying types of xDSLs used in a particular network, a single a priori model is not suitable

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