Timing system for modular cable modem termination system
First Claim
1. A modular cable modem termination system (CMTS), comprising:
- at least one packet shelf operating a data over cable service interface specifications (DOCSIS) media access controller (MAC), wherein the MAC is configured to frame received data with DOCSIS frames and mark the DOCSIS framed data with destination addresses corresponding to downstream cable modems;
one or more physical interface (PHY) shelves exchanging communications with the packet shelf over a packet switched network, wherein the one or more PHY shelves are configured to quadrature amplitude modulate the DOCSIS framed data for transmission over RF channels extending from the PHY shelves to the cable modems;
wherein the functions of DOCSIS framing the data and conducting the quadrature amplitude modulation are distributed across the packet switched network, and wherein the packet switched network contains packet switching accruements configured to forward individually addressed packets such that different ones of the packets can traverse the packet switched network in different amounts of time;
a timing system configured to measure a time delay associated with transporting the packets over the packet switched network between the packet shelf and at least one of the PHY shelves;
the timing system configured to identify timestamp values included in the DOCSIS framed data; and
the timing system configured to synchronize DOCSIS timing between the packet shelf and the one or more PHY shelves according to the measured time delay, wherein said synchronization includes dynamically adjusting the timestamp values on an individual basis according to the amount of delay experienced during the corresponding DOCSIS frame'"'"'s traversal of the packet switched network.
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Accused Products
Abstract
A modular Cable Modem Termination System (CMTS) includes a packet shelf operating a Data Over Cable Service Interface Specifications (DOCSIS) Media Access Control (MAC) framer. One or more downstream Physical Interface (PHY) shelves receive DOCSIS data from the packet shelf over a packet switched network and modulate the DOCSIS data for sending on a downstream path of a cable plant. One or more upstream PHY shelves send DOCSIS data received from an upstream path of the cable plant over the packet switched network to the packet shelf. By separating the PHY components from the MAC and from the system software, the PHY components for a Hybrid Fiber Coax (HFC) plant may be replaced with different PHY components for other access technologies such as wireless, Digital Subscriber Lines (DSL), Ethernet-to-the-Home, Fiber-to-the-Home, or fiber Passive Optical Networks (PONs).
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Citations
10 Claims
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1. A modular cable modem termination system (CMTS), comprising:
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at least one packet shelf operating a data over cable service interface specifications (DOCSIS) media access controller (MAC), wherein the MAC is configured to frame received data with DOCSIS frames and mark the DOCSIS framed data with destination addresses corresponding to downstream cable modems; one or more physical interface (PHY) shelves exchanging communications with the packet shelf over a packet switched network, wherein the one or more PHY shelves are configured to quadrature amplitude modulate the DOCSIS framed data for transmission over RF channels extending from the PHY shelves to the cable modems; wherein the functions of DOCSIS framing the data and conducting the quadrature amplitude modulation are distributed across the packet switched network, and wherein the packet switched network contains packet switching accruements configured to forward individually addressed packets such that different ones of the packets can traverse the packet switched network in different amounts of time; a timing system configured to measure a time delay associated with transporting the packets over the packet switched network between the packet shelf and at least one of the PHY shelves; the timing system configured to identify timestamp values included in the DOCSIS framed data; and the timing system configured to synchronize DOCSIS timing between the packet shelf and the one or more PHY shelves according to the measured time delay, wherein said synchronization includes dynamically adjusting the timestamp values on an individual basis according to the amount of delay experienced during the corresponding DOCSIS frame'"'"'s traversal of the packet switched network. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A modular Cable Modem Termination System (CMTS), comprising:
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a core device configured to receive data over a first network and format the data for communication over a second cable network, wherein the core device is configured to frame the received data with DOCSIS frames and mark the DOCSIS framed data with destination addresses corresponding to downstream cable modems; a timing system configured to measure a time delay associated with transporting the DOCSIS framed data over a variable delay portion of the second cable network; an edge device operating as a gateway between a constant delay portion of the second cable network and the variable delay portion of the second cable network, the edge device configured to receive the DOCSIS framed data from the core device over the variable delay portion and to quadrature amplitude modulate the DOCSIS framed data for downstream transmission over RF channels extending through the constant delay portion and to the cable modems; wherein the functions of DOCSIS framing the data and conducting the quadrature amplitude modulation are distributed across a packet switched network, and wherein the packet switched network contains packet switching accruements configured to forward individually addressed packets such that different ones of the packets can traverse the packet switched network in different amounts of time; the timing system configured to identify timestamp values included in the DOCSIS framed data; and the timing system configured to synchronize DOCSIS timing between the core device and the edge device according to the measured time delay, wherein said synchronization includes dynamically adjusting the timestamp values on an individual basis according to the amount of delay experienced during the corresponding DOCSIS frame'"'"'s traversal of the variable delay portion of the second cable network. - View Dependent Claims (10)
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Specification