Method and apparatus for upstream burst transmission synchronization in cable modems

A method in a network interface unit for synchronizing data transmissions from multiple network interface units to a network controller, the method comprising;

• receiving synchronizing messages from the network controller, the synchronizing messages including synchronizing information comprising an offset from the beginning of a received frame marker and a number of a transmit slot relative to the offset in which to transmit;
• recording local times of arrival of the synchronizing messages at the interface unit;
• determining local transmit times for transmission to the network controller corresponding to said synchronizing messages in accordance with the offset, transmit slot number and local time of arrival of the synchronizing messages;
• determining an upcoming local transmit time corresponding to a most recent synchronizing message in accordance with local transmit times corresponding to previously received messages and synchronizing information of the most recent synchronizing message;
• and
• transmitting data to the network controller in accordance with said upcoming local transmit time;
• and
• accepting phase adjustment information from a ranging phase adjustment message,
• wherein said local transmit times and said upcoming local transmit time are determined in accordance with corresponding offsets, transmit slot numbers, local times of arrival, and said phase adjustment information, and
• wherein said phase adjustment information comprises a measure of fixed transmission delay between the network interface apparatus and the network controller.

A network interface apparatus for providing data transmissions to a network controller that are synchronized with transmissions from other network interface apparatuses to the network controller, the apparatus comprising:

• at least one processor;
• and
• computer readable media coupled to the at least one processor and containing programming instructions for performing processing comprising:
• receiving synchronizing messages from the network controller, the synchronizing messages including synchronizing information comprising an offset from the beginning of a
• received frame marker and a number of a transmit slot relative to the offset in which to transmit;
• recording local times of arrival of the synchronizing messages at the interface unit;
• determining local transmit times for transmission to the network controller corresponding to said synchronizing messages in accordance with the offset, transmit slot number and local time of arrival of the synchronizing messages;
• determining an upcoming local transmit time corresponding to a most recent synchronizing message in accordance with local transmit times corresponding to previously received messages and synchronizing information of the most recent synchronizing message;
• and
• transmitting data to the network controller in accordance with said upcoming local transmit time,
• wherein said processing further comprises accepting phase adjustment information from a ranging phase adjustment message,
• wherein said local transmit times and said upcoming local transmit time are determined in accordance with corresponding offsets, transmit slot numbers, local times of arrival, and said phase adjustment information, and
• wherein said phase adjustment information comprises a measure of fixed transmission delay between the network interface apparatus and the network controller.

A network interface apparatus for providing data transmissions to a network controller that are synchronized with transmissions from other network interface apparatuses to the network controller, the apparatus comprising:

• a clock from which the network interface unit obtains a local time;
• a message receiver for receiving messages from the network controller;
• a time tag generator for recording local times of arrival of synchronizing messages at the interface unit, the synchronizing messages containing synchronizing information comprising an offset from the beginning of a received frame marker and a number of a transmit slot relative to the offset in which to transmit;
• a phase lock loop for accepting time tag information and synchronizing information corresponding to synchronizing messages and generating corresponding local transmit times therefrom;
• an extrapolator for determining an upcoming local transmit time corresponding to a most recent synchronizing message in accordance with local transmit times corresponding to previously received messages and synchronizing information of the most recent synchronizing message;
• and
• a transmission unit for generating a data transmission from the network interface unit to the network control unit in accordance with said upcoming local transmit time;
• wherein the phase lock loop further accepts phase adjustment information from ranging phase adjustment messages and generates local transmit time information from time tag information and synchronizing information and said phase adjustment information;.
• wherein said phase adjustment information comprises a measure of a fixed transmission delay between the network interface apparatus and the network controller.

A network interface apparatus for providing data transmissions to a network controller that are synchronized with transmissions from other network interface apparatuses to the network controller, the apparatus comprising:

• a clock from which the network interface unit obtains a local time;
• a message receiver for receiving messages from the network controller;
• a time tag generator for recording local times of arrival of synchronizing messages at the interface unit, the synchronizing messages containing synchronizing information comprising an offset from the beginning of a received frame marker and a number of a transmit slot relative to the offset in which to transmit;
• a phase lock loop for accepting time tag information and synchronizing information corresponding to synchronizing messages and generating corresponding local transmit times therefrom;
• an extrapolator for determining an upcoming local transmit time corresponding to a most recent synchronizing message in accordance with local transmit times corresponding to previously received messages and synchronizing information of the most recent synchronizing message;
• and
• a transmission unit for generating a data transmission from the network interface unit to the network control unit in accordance with said upcoming local transmit time;
• wherein said offset comprises a number of received symbols.
• wherein determining said upcoming local transmit time comprises:
• determining an average elapsed local time per symbol from local transmit times and corresponding synchronizing information of previously received synchronizing messages;
• and
• determining said upcoming local transmit time in accordance with said average elapsed local time per symbol and synchronizing information of a most recent synchronizing message.

A method in a network interface unit for synchronizing data transmissions from multiple network interface units to a network controller, the method comprising;

• receiving synchronizing messages from the network controller, the synchronizing messages including synchronizing information comprising an offset from the beginning of a received frame marker and a number of a transmit slot relative to the offset in which to transmit;
• recording local times of arrival of the synchronizing messages at the interface unit;
• determining local transmit times for transmission to the network controller corresponding to said synchronizing messages in accordance with the offset, transmit slot number and local time of arrival of the synchronizing messages;
• determining an upcoming local transmit time corresponding to a most recent synchronizing message in accordance with local transmit times corresponding to previously received messages and synchronizing information of the most recent synchronizing message;
• and
• transmitting data to the network controller in accordance with said upcoming local transmit time;
• wherein said offset comprises a number of received symbols.
• wherein determining said upcoming local transmit time information comprises:
• determining an average elapsed local time per symbol from local transmit times and corresponding synchronizing information of previously received synchronizing messages;
• and
• determining said upcoming local transmit time in accordance with said average elapsed local time per symbol and synchronizing information of a most recent synchronizing message.

A network interface apparatus for providing data transmissions to a network controller that are synchronized with transmissions from other network interface apparatuses to the network controller, the apparatus comprising:

• at least one processor;
• and
• computer readable media coupled to the at least one processor and containing programming instructions for performing processing comprising:
• receiving synchronizing messages from the network controller, the synchronizing messages including synchronizing information comprising an offset from the beginning of a received frame marker and a number of a transmit slot relative to the offset in which to transmit;
• recording local times of arrival of the synchronizing messages at the interface unit;
• determining local transmit times for transmission to the network controller corresponding to said synchronizing messages in accordance with the offset, transmit slot number and local time of arrival of the synchronizing messages;
• determining an upcoming local transmit time corresponding to a most recent synchronizing message in accordance with local transmit times corresponding to previously received messages and synchronizing information of the most recent synchronizing message;
• and
• transmitting data to the network controller in accordance with said upcoming local transmit time;
• wherein said offset comprises a number of received symbols;
• and
• wherein determining upcoming local transmit time information comprises:
• determining an average elapsed local time per symbol from local transmit times and corresponding synchronizing information of previously received synchronizing messages;
• and
• determining said upcoming local transmit time in accordance with said average elapsed local time per symbol and synchronizing information of a most recent synchronizing message.