Describing what Open RAN is (which we will do shortly) is important, but it is probably more important to describe why Open RAN was created. We will start there because it is easier to understand what Open RAN is if we first know why it is being built.
Most of operators’ costs (CapEx and OpEx) are in the RAN, and 5G requires a massive increase in the number of cells, types of cells, and radio types, which further raises RAN costs.
In recent years, the number of RAN providers has declined, which has reduced market competition.
Open RAN (ORAN) attempts to solve this problem. By disaggregating and dividing the RAN, supporting standardized, open, and interoperable interfaces, and enabling key functions such as virtualized software functions on vendor-neutral hardware, an evolving environment is created in which networks can be deployed with a more modular design. This offers the option of not depending on a single vendor and, in turn, provides multiple benefits.
ORAN vs. OpenRAN vs. vRAN
No discussion of the Open RAN (ORAN) technology movement is complete without the context of virtual RAN (vRAN).Both ORAN and vRAN are technological approaches. Rather than traditional RAN supplied by a single vendor using proprietary hardware and software, both ORAN and vRAN are technological approaches that differ from traditional RAN supplied by a single vendor using proprietary hardware.
Open RAN focuses on opening protocols and interfaces between the various disaggregated RAN subcomponents to drive radio, hardware, and software from multiple vendors.
vRAN is similar in that it focuses on decoupling RAN software features from custom hardware platforms to allow proprietary software to run on generic hardware computing platforms.
Specific aspects of Open RAN include:
O-RAN: O-RAN is a standards organization (the O-RAN Alliance) focused on publishing specifications for a new open RAN for 4G and 5G. O-RAN also focuses on facilitating testing of new ORAN devices.
OpenRAN: OpenRAN is a standard led by the Telecom Infra (TIP) project. Its goal is
“accelerate innovation and commercialization in the RAN space with interoperable products and solutions that are easy to integrate into the operator’s network and are verified for different deployment scenarios”. It has committed to creating an open RAN for 2G, 3G, 4G, and 5G.
(Note: “ORAN” is also an acronym for TIP groups. To avoid confusion, in this e-book “ORAN” will only be used to refer to the Open RAN movement).
In practice, there may be overlap between Open RAN and vRAN. The reality is that it is not exclusively an “either/or” approach, but one in which “the whole can be greater than the sum of its parts,” and some experts suggest they are destined to inevitably combine.
RU (Radio Unit)
These RF transceivers form part of the base station, located next to the antennas that capture (or transmit) signals (to or from) end-user equipment.The RU is where radiofrequency signals are transmitted, received, amplified, and digitized.
The RU is located near the antenna or integrated into it.
DU (Distributed Unit)
The DU is where real-time baseband processing functions reside. The DU can be centralized or located near the cell site and works with the lower layers of the protocol stack (RLC, MAC, and physical layer). It is commercial off-the-shelf (COTS) hardware, which can also be virtualized or containerized. It consolidates and processes incoming traffic from, or processes, separates, and distributes traffic to multiple business units.The processing performed by DUs is beyond the scope of this explanation, but it is important to note that the segment composed of the RU, the DU, and the transport between them is collectively called fronthaul. In particular, O-RAN calls this the lower layer split (LLS).
CU (Centralized Unit)
The CU sits between the DUs and the core network. The CU handles the upper layers of the protocol stack, where processing functions are less time-sensitive (SDAP, RRC, and PDCP). A single CU handles many DUs.Open DU and CU can run as virtualized software functions on vendor-independent hardware. CUs are also virtualized and run on low-cost COTS hardware.
Links:
- Open Fronthaul. The RU, the DU, and the transport between them, including use of the enhanced public radio interface (eCPRI), constitute the open fronthaul network.
- Open Midhaul. The RU, the CU, and the transport between the two comprise the open midhaul segment.
- Open Backhaul. The transport between the CU and the mobile core network comprises the open backhaul.
OPEN RAN Advantages
It offers lower costs for vendors and operators.More vendors = more competition. And greater competition drives down prices. Additionally, virtualization of the various RAN components enables operators to use COTS hardware, which further reduces costs.
It provides the ability to serve smaller and tightly defined 5G networks.
By reducing RAN costs, vendors can serve cost-sensitive 5G network use cases, such as rural markets or private 5G networks (for example, in a factory). A major driver for cloud service providers (CSPs) is coverage of traditional macrocell networks.
It drives innovation and accelerates time to market.
Increased competition naturally accelerates innovation. Virtualization of RAN systems enables innovation to be implemented in software, which is faster to deliver than hardware changes. As traditional RAN continues to innovate, it promotes greater ORAN participation, which further stimulates innovation. In this dynamic environment, more and new actors will innovate independently and offer richer solutions at a much faster pace, thus reducing time to market for new offerings.
It facilitates new monetization opportunities.
Open RAN will help stimulate a vibrant ecosystem of vendors, quickly offering new services to customers, reducing the risk of “vendor lock-in,” and introducing best-in-class network solutions, thus facilitating new monetization opportunities.
The advantages of open RAN are clear and compelling, with the promise of lower costs, diverse supply chains, and interoperable equipment. However, building a new ORAN from scratch and ensuring it works as intended is a massive undertaking, especially when combined with the transition to 5G, which is already pushing technical limits. With this background, we will examine precisely what ORAN is.
The advantages of Open RAN are clear and compelling, but even building a new ORAN from scratch and ensuring it works as intended is a gigantic task.