What is DOCSIS 4.0?

What is DOCSIS 4.0? How is it different from DOCSIS 3.1?

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- everything RF

Nov 5, 2022


DOCSIS 4.0 (D4.0) is the latest version of DOCSIS which is an international telecommunications standard that adds high-bandwidth data transfer capability to an existing cable television (CATV) system. It was released in October 2017. DOCSIS 4.0 is used by cable television operators to provide cable Internet access over their existing hybrid fiber-coaxial (HFC) cables with the addition of an Internet cable modem.

DOCSIS 4.0 retains backward compatibility with DOCSIS 3.1 and uses the same physical layer (PHY) which integrates the OFDM (Orthogonal Frequency Division Multiplexing) and FEC (Forward Error Correction) mechanisms. The main difference between D3.1 and D4.0 is that DOCSIS 4.0 expands the total amount of spectrum available for upstream and downstream transmissions. While D3.1 uses frequencies ranging from 258 MHz to 1794 MHz for downstream and up to 204 MHz for upstream, D4.0 uses frequencies ranging from 108 to 1794 MHz for downstream and 5 to 684 MHz for upstream. D4.0 uses the full spectrum of the cable plant (0 MHz to ~1.8 GHz) at the same time in both upstream and downstream directions. This data transmission technique is called frequency division duplex (FDD) and enables multi-gigabit symmetrical (upstream/downstream) services. Where version 3.1 supported bandwidths of 1 or 2 Gbit/s upstream and up to 10 Gbit/s downstream, DOCSIS 4.0 delivers data rates of up to 10 Gbps in downstream and up to 6 Gbps in upstream.

DOCSIS 3.1 vs DOCSIS 4.0

Frequency Band
108 to 1794 MHz
258 MHz to 1794 MHz
Upstream Frequency
5 to 684 MHz
up to 204 MHz
Downstream Frequency
108 to 1794 MHz
258 MHz to 1794 MHz
Upstream Data Rate
up to 6 Gbps
1 or 2 Gbps
Downstream Data Rate
up to 10 Gbps
up to 10 Gbps

This latest version of DOCSIS enables coaxial cable technology to stay relevant even with the introduction of faster forms of data transfer mediums like optical fiber, wireless etc. It enables fast Internet access on par with other forms of technology while avoiding the challenging and costly task of replacing the whole well-established physical network infrastructure of coaxial cables.