Downstream remote physical interface for modular cable modem termination system
First Claim
1. A modular Cable Modem Termination System (CMTS), comprising:
- a packet shelf operating a Data Over Cable Service Interface Specification (DOCSIS) Media Access Control (MAC) framer, the packet shelf configured to operate on a gateway between a first access network and a second cable network, the DOCSIS MAC framer configured to frame communications received over the first access network into a DOCSIS format before communicating those DOCSIS framed communications over a variable delay packet switched portion of the second cable network;
wherein DOCSIS timestamps are inserted by the DOCSIS MAC framer, the DOCSIS timestamps usable for frequency locking downstream cable modems with the modular CMTS;
one or more downstream DOCSIS Physical Interface (PHY) shelves configured to receive the DOCSIS framed communications over the variable delay packet switched portion of the second cable network and from the packet shelf the DOCSIS PHY shelves configured to modulate the DOCSIS framed communications for sending on a constant delay portion of the second cable network;
wherein the variable delay packet switched portion of the second cable network contains packet switching accruements configured to forward individually addressed packets such that different ones of the packets can traverse the variable delay packet switched portion in different amounts of time, and wherein the DOCSIS MAC framer is separated from at least one of the DOCSIS PHY shelves by at least one of the packet switching accruements; and
a timing shelf in communication with the one or more DOCSIS PHY shelves, the timing shelf configured to replace the DOCSIS timestamps as the DOCSIS framed communications are introduced into the constant delay portion of the second cable network;
wherein said DOCSIS timestamp replacement by the timing shelf maintains the frequency lock between the modular CMTS and the downstream cable modems regardless of the variability of delays associated with transmitting the DOCSIS framed communications between the DOCSIS MAC framer and the one or more downstream DOCSIS PHY shelves through the variable delay packet switched network portion operating there between.
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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
13 Claims
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1. A modular Cable Modem Termination System (CMTS), comprising:
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a packet shelf operating a Data Over Cable Service Interface Specification (DOCSIS) Media Access Control (MAC) framer, the packet shelf configured to operate on a gateway between a first access network and a second cable network, the DOCSIS MAC framer configured to frame communications received over the first access network into a DOCSIS format before communicating those DOCSIS framed communications over a variable delay packet switched portion of the second cable network; wherein DOCSIS timestamps are inserted by the DOCSIS MAC framer, the DOCSIS timestamps usable for frequency locking downstream cable modems with the modular CMTS; one or more downstream DOCSIS Physical Interface (PHY) shelves configured to receive the DOCSIS framed communications over the variable delay packet switched portion of the second cable network and from the packet shelf the DOCSIS PHY shelves configured to modulate the DOCSIS framed communications for sending on a constant delay portion of the second cable network; wherein the variable delay packet switched portion of the second cable network contains packet switching accruements configured to forward individually addressed packets such that different ones of the packets can traverse the variable delay packet switched portion in different amounts of time, and wherein the DOCSIS MAC framer is separated from at least one of the DOCSIS PHY shelves by at least one of the packet switching accruements; and a timing shelf in communication with the one or more DOCSIS PHY shelves, the timing shelf configured to replace the DOCSIS timestamps as the DOCSIS framed communications are introduced into the constant delay portion of the second cable network; wherein said DOCSIS timestamp replacement by the timing shelf maintains the frequency lock between the modular CMTS and the downstream cable modems regardless of the variability of delays associated with transmitting the DOCSIS framed communications between the DOCSIS MAC framer and the one or more downstream DOCSIS PHY shelves through the variable delay packet switched network portion operating there between. - View Dependent Claims (2, 3, 4, 5)
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6. A modular cable downstream Physical Interface (PHY), comprising:
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a packet switched network interface for receiving Data Over Cable Service Interface Specification (DOCSIS) frames over a variable delay packet switched portion of a cable network; one or more Quadrature Amplitude Modulators (QAMs) for modulating information in the DOCSIS frames received over the packet switched network interface onto a downstream frequency channel; and timing adjustment circuitry configured to adjust DOCSIS timestamps included in the DOCSIS frames subsequent to the variable delay transmission and as the DOCSIS frames are introduced into a constant delay portion of the cable network, wherein the timing adjustment circuitry is configured to perform the DOCSIS timestamp adjustment on an individual basis according to the amount of delay experienced during the corresponding DOCSIS frame'"'"'s traversal of the variable delay packet switched portion of the cable network. - View Dependent Claims (7, 8, 9)
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10. A method for operating a downstream Physical Interface (PHY) in a cable network, comprising:
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receiving Data Over Cable Service interface Specification (DOCSIS) frames from a DOCSIS Media Access Controller (MAC) over a variable delay packet switched network; receiving the DOCSIS frames over different tunnels associated with different Quality of Service (QoS) levels and processing the DOCSIS frames according to the QoS levels for the associated tunnels; adjusting DOCSIS timestamps included in the DOCSIS frames subsequent to the variable delay transmission and just prior to introducing the DOCSIS frames into a constant delay portion of the cable network, wherein the DOCSIS timestamp adjustment is performed on an individual basis according to the amount of delay experienced during the corresponding DOCSIS frame'"'"'s traversal of the variable delay packet switched network; and after adjusting the DOCSIS timestamps, modulating information in the DOCSIS frames for transporting over the constant delay portion of the cable network. - View Dependent Claims (11, 12)
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13. A system for operating a downstream Physical Interface (PHY) in a cable network, comprising:
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means for receiving Data Over Cable Service Interface Specification (DOCSIS) frames from a DOCSIS Media Access Controller (MAC) over a variable delay packet switched network; means for receiving the DOCSIS frames over different tunnels associated with different Quality of Service (QoS) levels and processing the DOCS1S frames according to the QoS levels for the associated tunnels; means for adjusting DOCSIS timestamps included in the DOCSIS frames on an individual basis according to the amount of delay experienced during the corresponding DOCSIS frame'"'"'s traversal of the variable delay packet switched network subsequent to the variable delay transmission and just prior to introducing the DOCSIS frames into a constant delay portion of the cable network; and means for modulating information in the DOCSIS frames for transporting over the constant delay portion of the cable network.
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Specification