System for data channel level control

In a bi-directional cable television system comprising a system manager for controlling a plurality of television terminals over a cable television signal distribution system, a method for automatically calibrating a particular optimum transmit level for transmitting data from the television terminals to the system manager, the automatic level calibration method comprising the steps of:

• transmitting an addressed command from the system manager to a particular television terminal to transmit a reply communication at a particular calibration frequency,
• transmitting said reply communication having a plurality of levels from the addressed terminal if the address transmitted with the command matches an address for the terminal,
• receiving the reply communication at the particular calibration frequency at the system manager,
• determining an indication of received signal strength for each received level, and
• determining an optimum transmit level for transmissions from the addressed terminal from said determined signal strengths.

In a bi-directional cable television system comprising a system manager for controlling a plurality of television terminals over a cable television signal distribution system, a method for automatically calibrating a particular optimum transmit level for transmitting data from the television terminals to the system manager, the automatic level calibration method comprising the steps of:

• transmitting an addressed command from the system manager to a particular television terminal to transmit a sequence of levels at a particular calibration frequency,
• transmitting a communication including the sequence of levels from the addressed terminal if the address transmitted with the command matches an address for the terminal,
• receiving the sequence of levels at the particular calibration frequency at the system manager,
• determining an indication of received signal strength for each received level of the sequence of received levels,
• determining an optimum transmit level for transmissions from the addressed terminal from said determined sequence of signal strengths,
• maintaining a received signal strength indication for each message received from the particular terminal, and
• determining a slope/tilt characteristic for data channel frequency versus signal strength indication.

In a bi-directional cable television system comprising a system manager for controlling a plurality of television terminals over a cable television signal distribution system, apparatus for automatically calibrating a particular optimum transmit level for transmitting data from the television terminals to the system manager, the automatic level calibration apparatus comprising:

• programmable transmitter apparatus located at said television terminals for transmitting a communication including a sequence of levels at a particular calibration frequency in response to an addressed command generated by the system manager;
• programmable receiver apparatus located at said system manager for receiving the sequence of levels at the particular calibration frequency and for determining an indication of received signal strength for each received level of the sequence of received levels;
• a controller coupled to said receiver for determining an optimum transmit level for operation of the programmable transmitter apparatus at the calibration frequency from said sequence of determined signal strengths;
• and
• wherein said sequence of levels comprises eight levels and the optimum transmit level is related to an optimum received level of approximately 12 dBmV.

In a bi-directional cable television system comprising a system manager for controlling a plurality of television terminals over a cable television signal distribution system, apparatus for automatically calibrating a particular optimum transmit level for transmitting data from the television terminals to the system manager, the automatic level calibration apparatus comprising:

• programmable transmitter apparatus located at said television terminals for transmitting a communication including a sequence of levels at a particular calibration frequency in response to an addressed command generated by the system manager;
• programmable receiver apparatus located at said system manager for receiving the sequence of levels at the particular calibration frequency and for determining an indication of received signal strength for each received level of the sequence of received levels;
• a controller coupled to said receiver for determining an optimum transmit level for operation of the programmable transmitter apparatus at the calibration frequency from said sequence of determined signal strengths;
• and
• wherein the calibration frequency is selected from frequencies in the high frequency portion of the T8 frequency band.

In a bi-directional cable television system comprising a system manager for controlling a plurality of television terminals over a cable television signal distribution system, apparatus for automatically calibrating a particular optimum transmit level for transmitting data from the television terminals to the system manager, the automatic level calibration apparatus comprising:

• programmable transmitter apparatus located at said television terminals for transmitting a communication including a sequence of levels at a particular calibration frequency in response to an addressed command generated by the system manager;
• programmable receiver apparatus located at said system manager for receiving the sequence of levels at the particular calibration frequency and for determining an indication of received signal strength for each received level of the sequence of received levels, said programmable receiver apparatus comprising a plurality of data channel receivers including a channel calibration receiver, a signal strength analyzer associated with the calibration channel frequency receiver, and a received signal strength indicator associated with each of the plurality of data channel receivers including the calibration channel frequency receiver;
• and
• a controller coupled to said receiver for determining an optimum transmit level for operation of the programmable transmitter apparatus at the calibration frequency from said sequence of determined signal strengths.