Adaptive rate control for echo cancelling modem

A method for use in a modem of the kind which receives data signals from a remote device over a channel in accordance with one of a range of available modulation schemes which are suitable, respectively, for different levels of channel quality, a higher level modulation scheme being suitable for a higher channel quality, said modulation schemes including coded and uncoded modulation modes, comprising

• initializing said modem using a threshold having a selected one of two values, one value corresponding to a change to a coded modulation mode and a different value corresponding to a change to an uncoded modulation mode,
• monitoring the quality of the channel based on received data signals,
• determining when a change to a higher level modulation scheme would be permissible based on when the monitored channel quality exceeds the threshold,
• requesting the remote device to change to a higher level modulation scheme employing the modulation mode corresponding to the selected value when a change to the higher level modulation scheme is determined to be permissible, and
• reinitializing said modem so as to set the threshold to the other value in response to an indication from the remote device that the requested modulation mode is not available.

A modem which receives data signals from a remote device over a channel in accordance with one of a range of available modulation schemes suitable, respectively, for a range of different channel qualities, a higher level modulation scheme being suitable for a higher channel quality, said modem comprising:

• quality monitoring logic for monitoring the quality of the channel,
• a fall forward flag register for storing a fall forward flag,
• conditioning logic for conditioning the fall forward flag to indicate whether an opportunity exists for the modulation scheme to fall forward to a higher modulation scheme,
• rate adjustment logic responsive to the quality monitoring logic for determining that the channel will support a fall forward to a higher level modulation scheme,
• rate setting logic responsive to the rate adjustment logic for sending a subsequent fall forward request to the remote device wherein the rate setting logic sends the subsequent fall forward request only if the fall forward flag is conditioned to indicate that an opportunity to fall forward exits.

A modem which receives data signals from a remote device over a channel in accordance with one of a range of available modulation schemes which are suitable, respectively, for different levels of channel quality, a higher level modulation scheme being suitable for a higher channel quality, said modulation schemes including coded and uncoded modulation modes, the modem comprising:

• initialization logic for initializing said modem using a threshold having a selected one of two values, one value corresponding to a change to a coded modulation mode and a different value corresponding to a change to an uncoded modulation mode,
• quality monitoring logic for monitoring the quality of the channel based on received data signals,
• fall forward logic for determining when a change to a higher level modulation scheme would be permissible based on when the monitored channel quality exceeds the threshold,
• request logic for requesting the remote device to change to a higher level modulation scheme employing the modulation mode corresponding to the selected one of two values when a change to the higher level modulation scheme is determined to be permissible,
• reinitialization logic for causing a reinitialization of said modem so as to set the threshold to the other value in response to an indication from the remote device that the requested modulation mode is not available.