Patent ID: 7688828
Filing Date: 2010-03-30
Classification: H04L

Abstract:
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.