DOCSIS – Towards a Gigabit Future

DOCSIS – Towards a Gigabit Future

DOCSIS stands for Data Over Cable Service Interface Specification. It’s an international telecommunications standard which enables the addition of high-bandwidth data transfer to an existing cable system which was traditionally dedicated to TV and dial-up internet. The earliest version of DOCSIS was introduced in 1997.

DOCSIS 3.1 is the most recent of these technical specifications and will enable a new generation of cable services, allowing cable operators to meet future consumer demand for high speed connections and advanced applications. The specification is an evolution of the successful DOCSIS and EuroDOCSIS specifications 1.0, 2.0 and 3.0, and introduces a new generation of hardware that can deliver up to 10Gbps broadband speeds on hybrid fibre-coaxial (HFC) networks.

Full Duplex (FDX) is an extension to the DOCSIS 3.1 standard which allows 10Gbps symmetrical speed on cable networks. FDX allows the upstream and downstream to share the same frequency band. This extension will offer more upstream bandwidth and higher speeds than previously possible with DOCSIS.


Another important characteristic of DOCSIS 3.1 is Active Queue Management (AQM). Cable networks rely on two types of equipment to provide broadband services:  1) the cable modem which is installed at a customer’s premises and 2) the Cable Modem Termination System (CMTS) which is installed at the cable operator premises and controls all cable modems. AQM enables the cable modem and CMTS to monitor how full their buffers are getting.  A buffer is a memory space for storing packets of data and ensures the continuity of the service by smoothing out packet transmission.   AQM ensures that appropriate buffer levels are maintained.


Cable networks are always ahead of consumer demand thanks to regular network upgrades which can be achieved by:

  • Upgrading to the latest DOCSIS specification. This can be done by changing all required equipment, or incrementally by upgrading selected equipment following demand from the market. At this point operators can also choose to expand the amount of frequencies they use.
  • Splitting nodes. This is a process that deploys fibre closer to the customer’s premises and increases the capacity available to each customer served.
  • Rearranging the frequencies. Cable operators use radio spectrum inside their cables.  Switching off legacy services such as analogue TV releases spectrum which can be used for broadband services.

These upgrades can be done simultaneously or independently from each other. This flexibility gives cable an edge in serving different market configurations.

The evolution of DOCSIS

Source: Cablelabs