What are Mid-Split and High-Split DOCSIS?

Splits refer to the separation between Return/Upstream and Forward/Downstream spectrum allocation in DOCSIS. Mid and High refer to moving that separation higher, allocating more bandwidth to the Return channels for more upload capacity (speed).

DOCSIS_ESD-Extended_Band_Samples-1Figure 1. Examples of mid/high-split and extended spectrum DOCSIS. They offer significant improvements to upstream and downstream bandwidth and performance.

"Split" is a reference to the separation or spectrum allocation between Return (Upstream) and Forward (Downstream) signals in DOCSIS coaxial cable plants (HFC, R-PHY, DAA).

  • In the original spectral allocation splits, the Return (US) signals were limited to around 42 MHz (USA) or 65 MHz (Europe). 
  • Mid-Split allocates a bit more spectral bandwidth to the Return signals, to around 85 MHz, allowing faster and more reliable upstream data rates.
  • High-Split moves the Return spectrum allocation even higher, to around 204 MHz, giving more bandwidth to the upstream (US) for more speed. This is normally combined with 1.2 GHz Extended Spectrum DOCSIS 3.1 (ESD) for the Downstream (DS), to offer much higher (more competitive) upstream and downstream data rates.
  • Ultra High-Split moves the spectrum allocation even higher, to around 684 MHz, giving a significant amount of bandwidth to the upstream for much more speed. This is planned to be combined with 1.8 GHz Extended Spectrum DOCSIS 4.0 (ESD) for the downstream, to offer much higher (more competitive) upstream and downstream data rates and certain symmetric high-speed services.

Of course, the implementation of new bandwidth allocations requires updating, validating and troubleshooting all new passive and active elements in the coax plant, to make sure they comply with the new bandwidth requirements. For modern hybrid R-PHY/DAA/PON networks, this can be verified by (frequency) sweeping the coax segments with a new generation of portable meters (test sets) supporting the new extended frequency ranges. Portability is key because the fiber feeders are now digital and the remaining coaxial segments are at the edge of the HFC network. 

For more details, refer to the Extended Spectrum DOCSIS (ESD) & High Split Article

Related Test Solutions

  • SWP-BOX Portable Sweep Generator (supports extended spectrum)
  • CX380C Advanced Plant Maintenance Meter (handheld sweep receiver)

Related Information & Reference Materials