Data Centre

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CableLabs signs off MAC spec for DOCSIS full duplex

Fibre, schmibre: existing cable TV networks edge closer to symmetric 10 Gbps capabilities

By Richard Chirgwin

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US standards outfit CableLabs has added another piece to the Full Duplex DOCSIS 3.1 jigsaw, with the release of the key MAC layer specification for the standard.

DOCSIS 3.1 Full Duplex is designed to push symmetric 10 Gbps over the world's cable (or hybrid fibre-coax, HFC) networks.

The spec expands the existing DOCSIS media access control layer with messages specific to setting up full duplex communications between the cable modem and the upstream cable modem termination system (CMTS).

As CableLabs architect Karthik Sundaresan explained here, the MAC layer changes let a cable modem acquire and initialise a full duplex channel, as well as supporting new processes including sounding, echo cancellation training, and resource block assignment.

Sounding refers to how the system identifies groups of modems that will interfere with each other if they receive and transmit at the same time in any sub-band of the system. Echo cancellation is a common mechanism to prevent interference between upstream and downstream communications.

Resource block assignment refers to how the CMTS assigns frequency bands to cable modems for full-duplex communication.

With the MAC layer work complete for now, CableLabs expects silicon design to accelerate, and starting this month the organisation is running interoperability events.

Sundaresan added that the work-in-progress includes incorporating OSS support in the full duplex spec, further development in the physical layer, and refinements to PHY and MAC specs once vendors start hooking products together. ®

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