Apparatus of synchronization for docsis upstream signal transmission through optical ip network and method of the same

A synchronization apparatus for transmitting a DOCSIS upstream signal, comprising:

• a communication unit for communicating with a Cable Modem Termination System (CMTS), an 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 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 IP packet in order to transmit the ranging request signal to the RoIP headend device.

A synchronization method for transmitting a DOCSIS upstream signal, which is performed by an 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 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 an RF signal;
• and
• transmitting the RF signal to the CMTS.