what is full duplex docsis 3.1


For the first 30 years, say the mid-60’s to the mid-90’s, the cable plant was just a cable plant. There was no fiber and generally there was no upstream return path. When VOD services where introduced in the 80s and 90s, there was a need for upstream signaling for STB and an upstream OOB carrier was established (there was already a broadcast downstream OOB carrier).

This large coax system would not scale for data. In the 1990’s optical nodes where deployed to create a Hybrid Fiber-Coaxial (HFC) plant that had a limited number of households passed in a coax segment. This was to ensure that the noise funneling from the homes was tolerable enough that data could be passed over the upstream path.


Data started off with a shared 2.5 Mbps upstream channel. That later grew to 10 Mbps with DOCSIS 1.0 and to 30 Mbps with DOCSIS 2.0. The number of channels that the silicon could support also grew from one to four. Today with bonding and DOCSIS 3.0, the return path data capacity is around 90 Mbps in a 42 MHz or 65 MHz return path. In practice, the spectrum below 42 MHz is full of legacy traffic and will likely stay as ATDMA traffic.

Although the OFDMA traffic from DOCSIS 3.1 could theoretically be mixed with the ATDMA traffic, the bandwidth gain provided by OFDMA and LDPC would be quickly offset by the time and frequency guard time requirements that must exist between DOCSIS 3.0 and DOCSIS 3.1 spectrum. With DOCSIS 3.0 and DOCSIS 3.1, it is possible to run a higher frequency upstream return path.

The two favorite options are 85 MHz and 204 MHz. Both these return paths push the start of the downstream spectrum to a higher frequency. In todays FDD (Frequency Division Duplex) system, new upstream spectrum is taken from existing downstream spectrum.


The Cable Industry is now a recognized leader in the delivery of Last-Mile Services to residential subscribers, and it is continually expanding its access to business subscribers. The offered services include Video, Voice, and Broadband Data services.

While the Cable network started out as a simple coaxial infrastructure optimized for the delivery of Analog Video, it has evolved into a powerful Hybrid Fiber-Coaxial (HFC) system over the years to support these many varied service types. The HFC network has proven time and time again that it is an extremely flexible and robust infrastructure that can be morphed to accommodate the unique and continually changing needs of the subscribers and the different services.

The addition of amplifiers for longer reach was the beginning of this evolution. That was followed by spectral expansions to deliver more TV channels. Then by the addition of fiber to further increase reach and reduce the effects of electrical interference. The addition of DOCSIS for Voice and Broadband service was another powerful modification.

Fiber Deep solutions (based on continual node-splits) have carried the network to its current state of existence. DOCSIS 3.1 augmentations will expand the spectrum and the spectral efficiency of the HFC network to support ~10 Gbps Downstream bandwidth capacity and ~2 Gbps Upstream bandwidth capacity on a 1.2 GHz plant with a 204 MHz high-split.


Full Duplex DOCSIS 3.1 technology is an extension of the DOCSIS 3.1 specification that significantly increases upstream capacity and enables symmetric multi-Gigabit services over existing HFC networks. DOCSIS 3.1 enabled the potential of 10Gbps downstream and 1 Gbps upstream broadband. With Full Duplex DOCSIS 3.1 technology, the upstream and downstream traffic has the potential to flow at up to 10 Gigabits concurrently, doubling the efficiency of spectrum use.

Full Duplex DOCSIS technology allows future applications that need high speed symmetric services or high upstream speeds to work equally well. It’s the difference from a moveable median barrier, to full double-decker lanes! Full Duplex DOCSIS 3.1 Press Release