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Radisys Series — Who Disaggregated My RAN?
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Chapter 3:
Open RAN and Fronthaul: The Last Mile
As we saw in the last article in this blog series, the disaggregation of the RAN has opened up a number of new and
exciting opportunities for a larger ecosystem to grow and thrive. But nowhere has the momentum been felt more
than in the last mile, specifically with regard to Fronthaul and with the Radio itself.
Traditional Fronthaul Technologies
Most of the current deployments of LTE macro cell sites consist of base station equipment located at the bottom
of a tower and the radio or Remote Radio Head (RRH) located at the top. The base station, or Base Band Unit (BBU),
and RRH are typically connected through a high bandwidth fiber connection – what we call Fronthaul.
As we have seen, the traditional RAN evolved into a Centralized RAN
(C-RAN). In C-RAN deployments, the base station is located a few miles
away from the radios and is linked to the RRH by an optical fiber based
fronthaul.
A few protocol standards enabled this fronthaul transport to carry data
between the base stations and the remote radio heads. These standards
include:
• Common Public Radio Interface (CPRI)
• Open Base Station Architecture Initiative (OBSAI)
• Open Radio Equipment Interface (ETSI-ORI)
CPRI emerged as the most popular option for LTE and is the standard we think about most often when discussing
fronthaul. The standard was developed by vendors in the optical technology space, and as it matured, it became the
de facto standard for fronthaul. CPRI allowed for a great deal of customization, and traditional RAN vendors began
Figure 1: Traditional Fronthaul
