Apparatus of synchronization for DOCSIS upstream signal transmission through optical IP network and method of the same

A synchronization apparatus for transmitting a Data Over Cable Service Interface Specification (DOCSIS) upstream signal, comprising:

• a communication unit for communicating with a Cable Modem Termination System (CMTS), a Radio over Internet Protocol (RoIP) headend device, and a Cable Modem (CM);
• a synchronization unit for synchronizing a clock and generating a reference time by receiving a synchronization (SYNC) message periodically sent from the CMTS;
• and
• a signal conversion unit for converting a ranging request signal, which is delivered from the CM and is a Radio Frequency (RF) signal, including information about a time at which the ranging request signal is received and information about a start time of an allocated ranging interval, into an Internet Protocol (IP) packet in order to transmit the ranging request signal to the RoIP headend device,
• wherein the synchronization unit performs a clock synchronization with the CM, and
• wherein the RoIP headend device performs a clock synchronization with the CMTS.

A synchronization method for transmitting a Data Over Cable Service Interface Specification (DOCSIS) upstream signal, which is performed by a Radio over Internet Protocol (RoIP) headend device, comprising:

• receiving a synchronization (SYNC) message periodically sent from a Cable Modem Termination System (CMTS) and thereby synchronizing a clock and generating a reference time;
• receiving a ranging request signal, which is an Internet Protocol (IP) packet including information about a start time of an allocated ranging interval, from an RoIP terminal over an IP network, the ranging request signal being transmitted from a Cable Modem (CM);
• converting the ranging request signal into a Radio Frequency (RF) signal;
• and
• transmitting the RF signal to the CMTS,
• wherein the RoIP terminal performs a clock synchronization with the CM, and
• wherein the RoIP headend device performs a clock synchronization with the CMTS.