Data Over Cable Service Interface Specification (DOCSIS)

Data over cable service interface specification (DOCSIS) is an international telecommunications standard to provide high speed data to cable TV system over its existing hybrid fiber-coaxial (HFC) infrastructure. It is used for providing cable Internet access as well as supporting high definition televisions.

Versions of DOCSIS

• DOSCIS 1.0 − It was the first version for cable modem system

• DOSCIS 2.0 − It enhanced upstream data from computer to the operator to allow services requiring equal data transfer in both uplink and downlink, like IP telephony.

• DOSCIS 3.0 − It supports IPv6 standard. It is marked by increase in transmission speed for both uplink and downlink.

• DOSCIS 3.1 Full Duplex − It uses full cable spectrum simultaneously for both uplink and downlink data transfer.

Features of DOSCIS

• Downstream data rate is typically 6MHz. Upstream data rate is upto 3.2MHz for DOCSIS 1.0 and 6.4MHz for later versions.

• They use modulation techniques QAM-64 or QAM-256 for downlink and QAM-16, QAM-32 or QAM-64 for uplink.

• For simultaneous multiple transmissions, time division multiple access (TDMA) and code division multiple access (CDMA) are used.

• It supports channel bonding that allows a subscriber to use multiple downstream and upstream channels simultaneously.

• It supports applications requiring low latency like Voice over IP.

• DOCSIS modems are managed by IP addresses.DOCSIS 3.0 and above supports IPv6.