Telefonaktiebolaget Lm Ericsson (publ)

Stefan Barkar&ouml;

Torbj&ouml;rn Randahl

Albin Johansson

For signal level adjustment of a multitone signal received over a transmission line ( ) during a training sequence in a DSL system, a programmable high-pass filter ( ) is connected to the transmission line ( ). A programmable gain control unit ( ) is connected between the filter ( ) and an A/D converter ( ). A digital signal processor ( ) is connected with its inputs to the A/D converter ( ), with control outputs ( ) to control inputs ( ) of the filter ( ), and with control outputs ( ) to control inputs ( ) of the gain control unit ( ). The processor ( ) detects signal level differences between the highest and the lowest tone of the multitone signal and programs the filter ( ) to make the signal levels of the highest and the lowest tone equal. The processor ( ) furthermore programs the gain control unit ( ) to adjust its total signal output level to coincide with the dynamic range of the A/D converter ( )

Signal level adjustment arrangement

To secure an ADSL connection between a first ADSL transceiver ( ) in a central office and a second ADSL transceiver ( ) on a subscriber's premises on a telephone line ( ) between a SLIC ( ) in the central office and a telephone ( ), a request to the SLIC ( ) to apply a ringing signal to the telephone line ( ) is detected. In response to such detection, the first ADSL transceiver ( ) switches from a normal bit rate to a lower bit rate for the ADSL connection, and orders the second ADSL transceiver ( ) to do the same before the ringing signal is applied. In response to an off-hook condition, the lower bit rate is maintained for the ADSL connection. In response to an on-hook condition after the off-hook condition as well as in response to a disappearance of the ringing request without an off-hook condition, the first ADSL transceiver ( ) switches back to the normal bit rate and orders the second ADSL transceiver ( ) to do the same.

Method and an arrangement for securing an ADSL connection

At the output of a line driver ( ) connected to a long transmission line, signals received on the transmission line are only a fraction of signals transmitted by the line driver on the transmission line. To minimize the transmitted signal with its distortion and noise in the receive path of the line driver, an additional driver ( ) having the same voltages and currents in the signal path, is added. The additional driver ( ) drives an additional load (Z ). The signal transmitted to the transmission line together with its superimposed received signal, is subtracted from the signal from the additional driver ( ), which is not superimposed on any received signal. The resulting signal is reduced from transmitted signal, transmitted distortion and transmitted noise. To minimize die size and power consumption, the additional driver ( ) is scaled, but the distortion remains unchanged compared to the &ldquo;normal&rdquo; line driver.

Echo and distortion cancellation arrangement

To secure an ADSL connection to an ADSL transceiver connected to a telephone line to be used also by an associated telephone, the telephone is normally kept disconnected from the telephone line and a predetermined number of bits is allocated to the ADSL connection. Upon an off-hook condition of the telephone in connection with an outgoing call, and upon a presence of a ringing signal on the telephone line or an off-hook condition of the telephone in connection with an incoming call, a predetermined lower number of bits is allocated to the ADSL connection before the telephone is connected to the telephone line.

In an arrangement for securing an ADSL connection to an ADSL transceiver connected together with a telephone to a common telephone line; there are devices for setting a first number and a second, lower number, respectively, of bits to be allocated to the ADSL connection. Moreover, there are devices for detecting whether or not a ringing signal is present on the line and whether the telephone is in the off-hook or the on-hook condition. The first number of bits is allocated when neither the ringing signal nor the off-hook condition is detected, and the second, lower number of bits is allocated when the ringing signal and/or the off-hook condition is detected.

Method and arrangement for securing an ADSL connection

To reduce power dissipation in a line driver connected to a transmission line for transmitting multitone signals in the form of successive symbols separated by cyclic prefixes and generated by a digital signal processor, a controllable voltage supply is connected with its output terminal to a supply voltage terminal of the line driver. In response to an expected peak-to-peak value of the next symbol to be transmitted, the digital signal processor controls the controllable voltage supply during each cyclic prefix to set an appropriate supply voltage to the line driver.

Growing community of inventors

Solna, Sweden

Stefan Barkarö

Growing community of inventors

Solna, Sweden

Stefan Barkar&ouml;

Stefan Barkarö