New-Tech Europe Magazine | April 2019

DOCSIS* - The Data Over Cable Standard

Nehorai Vaisler, Intel

The History of DOCSIS Data Over Cable Service Interface Specification, known as DOCSIS, is a specification invented in 1997 that defines the communication between all the components of the systems that enable passing data information through coax cables 1 . The cable network consists of coaxial cables which transmit the TV streaming in the homes and pass electronic energy as radio frequency in a different spectrum of signals. This means letting radio waves pass through cables instead of passing in the air.

Introduction Many homes are connected to broadband internet on the cable network – an alternative to ADSL internet over telephone lines - and enjoy high speed internet. However, not many know that this internet communication is made possible by a modem that is connected to the coax cable on one end and various consumer electronic devices on the other end. This article describes the international DOCSIS* specification that helps set up the communication network – via the modem - to pass the information between the network and devices.

Through these cables, it is possible to pass internet, video, and VoIP calls in parallel. In Israel, this solution is commonly known as the triple package deal. The DOCSIS specification was invented, and continues to be modified and improved, by Cable Television Laboratories, Inc, known as CableLabs*, as an alternative to telephony services that were previously the only way to deliver digital data to homes. CableLabs is a cable operators consortium and currently manages both the specification and certification programs to signify whether or not a

1 https://www.zcorum.com/wp-content/uploads/DOCSIS-Evolution-and-How-3.1-Will-Change-Everything.pdf 2 OFDM - Orthogonal frequency-division multiplexing enables the collection of dense channels in 25 KHz compared to Europe 8MHz / US 6MHz of single carrier channels, thus allowing for better utilization of the magnetic medium on top of the cables. Since the OFDM does not use frequency margins and the receiver detects a signal like a single carrier channel, it is possible to compress more channels, thereby increasing the bandwidth. Combining the FEC (Forward Error Correction) with OFDM enables the use of the existing cable infrastructure without the need to upgrade the infrastructure. This greatly contributed to the easier integration of the technology, and also improves the cost of each bit using AQM (Active Queue Management) mechanisms that enable better system queue management. This, in turn, greatly improves the latency response time.

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