radisys.com 4
Radisys Series — Who Disaggregated My RAN?
eBook
The Industry Begins to Solve the Problem
The first steps toward disaggregation started with the C-RAN (Cloud RAN or centralized RAN) initiative from IBM,
Intel and China Mobile. C-RAN resulted in a deployment model where a baseband unit (that hosted all of the base
station function except the radio) could be located in a data center or a far-edge location, while the radio – Remote
Radio Head (RRH) – was connected to the baseband unit via a dedicated high-bandwidth connection.
This wasn't without its challenges. The C-RAN model required a new Fronthaul interface, and various industry
standards such as the Common Public Radio Interface (CPRI) and the Next Generation Fronthaul Interface (NGFI)
evolved to enable these new interfaces between the base stations and the RAN.
As a natural evolution of C-RAN, multiple companies and industry initiatives started looking into splitting/
disaggregating RAN functionalities. There were multiple study reports published that looked at the merits and
challenges of various options:
• Small Cell Forum (SC159): Small cell virtualization functional splits and use cases (2015)
• Telecom Infra Project (TIP) openRAN project charter on 4G RAN disaggregation (2017)
• 3GPP technical report (38.801) on radio access architecture (2017)
These standards organizations began to prove that these initial steps towards disaggregated architecture
were technically sound. Base stations (LTE and 5G) began to evolve, and three important elements of a fully
disaggregated RAN began to emerge: the Centralized Unit (CU), the Distributed Unit (DU), and the Radio Unit (RU).
Figure 1: Traditional Base Station with RRH (left) and Centralized RAN with multiple RRHs (right)
