What is Radio Access Network (RAN)?

With the increased prevalence of mobile networks, user equipment (UE) must be seamlessly connected to a core network to facilitate rapid communication of data. 

In this blog, you'll learn what RAN (radio access network) is, how it works, the different variations, and why it is an integral component of 5G technology. 

What is RAN?

A RAN (radio access network) is a type of network infrastructure used commonly for mobile networks that consist of radio base stations with large antennas.

The primary purpose of a RAN is to wirelessly connect user equipment. 

How does RAN work?

In a RAN, the radio unit (RU) processes digital radio signals and transmits, receives, and converts the signals for the RAN base station. 

When the RU receives signal information from the antennas, it communicates with the baseband unit (BBU) using the Common Public Radio Interface (CPRI). 

The BBU takes the signal information and processes it, so it can be forwarded to the core network. Data returns to the user via the reverse process. 

The amount of area that a RAN node can cover varies depending on the capabilities of the antennas, RAN hardware, and software at the node.

In mobile networks, 60 to 65 percent of the total cost of ownership of a network is in the RAN. 

What are the variations of RAN?

D-RAN (Distributed RAN) 

This is the traditional RAN setup where a remote radio unit (RRU) and baseband unit (BBU) are co-located at every cell site. 

The RRU filters and amplifies the RF (radio frequency) signal, deciding the coverage of the system; it also converts the RF signal to digital data for processing. 

The CPRI (Common Public Radio Interface) is the protocol for frontal communications between the towers and base stations. 

Each cell site has a BBU, which manages the entire base station, operating/maintenance, and signaling processing. It decides the capacity of the system. 

Backhaul is the interface that is formed between the BBU pool and the core node (network).

C-RAN (Centralized RAN) 

With C-RAN, the BBU moves to a centralized location and the cell site has only the antenna and the RRU. 

The BBU pool is a pool of BBUs in a centralized location. 

Fronthaul is an interface that is formed between the RRU and BBU pool, and backhaul serves as an interface between the BBU pool and the core node. 

The primary benefit of C-RAN is that it reduces deployment and maintenance cost per cell site because BBUs are centralized.

Additionally, it improves spectral efficiency and reduces interference as BBU pools can share resources dynamically among the multiple RRUs. 

You also have another option to split BBUs into centralized units (CUs) and decentralized units (DUs) to split tasks, reduce costs, and improve efficiency even further. Midhaul is the interface between DU and CU. 

DU is software deployed on a COTS (commercial/customizable-off-the shelf) server that is controlled by the CU that controls the RLC (radio link control)/MAC (medium access control) block and parts of the PHY (physical) layer. 

The RLC/MAC block is the basic transport unit on the air interface that is used between the mobile and the network. 

In essence, the DU helps to split tasks rather than having it all in a BBU pool. This just allocates resources to specific tasks. 

The CU is software that runs the RRC (radio resource control)/PDCP (packet data convergence protocol). 

The RRC conducts many functions like information broadcasting, establishing and releasing connections between the user equipment and the RAN, and controlling the quality of service. 

The PDCP compresses and decompresses IP data stream headers and transfers user data, among other technical functions. 

The CU can remain at the base station or it can be placed at a more central aggregation site. A DU, however, is kept at a base station that is not at an aggregation or core network location.      

vRAN (Virtualized RAN) 

vRAN is a type of C-RAN with its networking functions separated from the hardware that it runs on. In this case, the BBU is what is separated through virtualization. 

The control planes--which control how data is forwarded--and the data planes--which actually forward data--are also separated. 

This type of RAN is often found in 5G technology architectures because the networks need virtualization to support the uses cases and performance requirements of 5G. 

How does vRAN work? 

Network functions virtualization (NFV) is the practice of turning hardware-based functions into software. In an NFV architecture, the hardware is typically COTS (commercial-off-the-shelf) hardware.

Virtualizing the RAN makes it more agile, flexible, cost-effective, and scalable than a hardware-based RAN.

A vRAN can adapt to changes in the network faster, including intelligent load balancing and allocating resources on demand; it also allows change without having to replace expensive hardware throughout the entire infrastructure, only needing to update software. 

Upgrading the RAN software can improve the network's connectivity, efficiency, or security, among other functions.

With a vRAN infrastructure, network operators can keep up with security better than network operators still using a non-virtualized RAN because bugs and other security issues can be fixed by updating software instead of having to replace hardware on a large scale. 

A secure network attracts more customers because the more trust the customer base has in a product like a network, the more likely they are to use it. 

This type of RAN, however, puts a strain on servers, as it requires massive amounts of compute power. This is where edge computing comes into play. 

OpenRAN 

Operators today want a more diverse ecosystem of vendors and are redefining their RAN requirements.

OpenRAN is a term used for industry-wide standards for RAN interfaces that support interoperating between vendors' equipment and offer network flexibility. (Think of O-RAN in the same sense as the open architectures SOSA/MOSA are introducing into their respective fields.) 

The main purpose of OpenRAN is to have an interoperability standard for RAN elements including non-proprietary white box hardware and software from different vendors.

OpenRAN is divided into three main building blocks: an O-RU, an O-DU, and an O-CU.

OpenRAN standards are being developed using vRAN principles and technologies to help improve network malleability, enhance security, and reduce costs. 

Network operators that opt for OpenRAN can avoid being stuck with one vendor's proprietary hardware and software. This leaves more room for innovation and competition, lower equipment costs, and improved network performance, as more vendors can provide the building blocks and add new services.

The OpenRAN Alliance allows customers to mix and match components from different vendors without being locked into one; it releases open software for the RAN, supporting its members in the integration and testing of their implementations.

Read more about OpenRAN here. 

RAN and 5G Technology

The amount of data available daily has grown rapidly, and as devices become more interconnected with each other and the larger network, data is being generated and transmitted at immense volumes. 

5G connectivity integrated with edge computers requires RAN virtualization (vRANs) because 5G demands more visibility, automation, and adaptability that traditional hardware-based RANs cannot provide.

The ability to scale and intelligently adjust the network to changing conditions is significant when the demands on 5G networks increase from both mobile phone users and, more significantly, IoT (Internet of Things) devices. 

Network administrators must be able to update a vRAN remotely because it enables improvement as technology advances. This a key component of 5G RANs because the component technologies involved are expected to change over the coming years. 

Final thoughts

RAN is a critical component in enabling the rapid transfer of data to core networks and user devices. 

Through distributed, centralized, virtualized, and open infrastructures, RAN can be amended and modified to fit the requirements of different operators and technologies. 

At Trenton, our high-performance computers are able to apply network virtualization to run multiple RAN infrastructures in a hyper-converged environment running on the same piece of hardware. 

This helps to improve connectivity at large, reduce hardware costs and downtime, and enable remote management of devices in the field. 

The different variations of RAN will help increase flexibility, maximize efficiency, and reduce costs, delivering unmatched performance for a variety use cases and applications across a wide range of industries.

Interested in learning more about 5G? Check out some other key 5G technologies that enhance compute architectures here.

• "What Is the Radio Access Network (RAN)?" - SDX Central