What is Radio Network Controller and Guide

A brief guide to understanding the importance of radio network controllers. Explaining the difference between radio network controllers and base station controllers.

Understanding the technical inner workings of the radio and mobile technology can be very overwhelming for a person who has not been formally trained in this field or dedicated a great amount of time to it. Even when you are well-versed in this area, constant changes and upgrades are being made on a regular basis so that it requires constant learning to remain up-to-date on all the current mechanisms and terms.

This article will attempt to explain in as simple terms as possible what a Radio Network Controller (RNC) is, what role it plays in governing radio access and why it has been such an improvement. Because understanding exactly what an RNC does requires relatively extensive knowledge about the mechanisms of radio technology, we will do our best to provide context without confusing you too much with unnecessary and overly technical terms.

However, there is no way to fully grasp the role of the RNC without also having some understanding of its place within the overall radio access network. Thus, essential terms will be highlighted throughout the article with the goal of helping you to learn exactly what an RNC is in a simple, yet comprehensive way.

What Is a Radio Network Controller (RNC)?

A Radio Network Controller is in charge of the use and distribution of all the radio resources of the Radio Network System (RNS) that it belongs to. The RNC carries out radio resource management, several of the mobility management functions, and encrypts data and information before that user data is sent to and from a mobile device.

The RNC also manages the user voice and packet data traffic, performing the actions on the user data streams that are required in order to access the radio bearers. The RNC connects to the Circuit Switched Core Network through Media Gateway (MGW) and to the SGSN (Serving GPRS Support Node) in the Packet Switched Core Network.

It serves as a governing element in the Universal Mobile Telecommunications Systems (UMTS) radio access network and its role within the system is to control the Node Bs that are connected to it. The job of the Node B is to then initiate radio transmission and reception in one or more cells to and from the user equipment (UE).

The best way to visualize how an RNC works is through a pyramid model, with the RNC positioned at the top of the pyramid. One RNC can control hundreds of Node Bs at one time. Those Node Bs then communicate with thousands of cells which organize tens of thousands of active calls in any given moment. This means that hundreds of thousands of users in a certain geographical range are supported by a single RNC.

what is radio network controller
Photo: semanticscholar.org

An RNC has three different logical functions through which it operates:

  • Controlling RNC (C-RNC): Each Node B (or base station) has a single RNC to which it responds that controls that Node B as well as all of the calls that belong to it
  • Serving RNC (S-RNC): When a piece of the equipment is connected to a network, it is always connected to just one specific S-RNC
  • Drift RNC (D-RNC): Drift RNC operates in a scenario in which the S-RNC has a connection to the ain user equipment through a cell that is managed by a different RNC. That other RNC is then C-RNC for that cell and simultaneously serves as the D-RNC for the user equipment

RNCs vs. BSCs

RNCs were developed as an improved replacement for the Base Station Controller (BSC) because the architects of the BSC did not anticipate just how much traffic volume would increase in the future. The goal in creating the RNC was to create a more complex system that could adapt to increasing traffic volume as well and new and previously unanticipated functions.

As the name suggests, BSCs were initially designed as part of second-generation cellular systems for controlling Base Stations (BTS). At the time, they enabled the industry to grow and expand, but eventually, he need to separate subscriber aspects from radio aspects pointed to a need for improvement.

BSCs were designed to control a single node, which quickly made them more and more obsolete as traffic grew and more functions had to be incorporated into the system. Architects designing the third-generation cellular system developed the RNC as a way to expand the capabilities that were lacking in the BSC as well as add a few additional and crucial functions.

In addition to the role played by the BSC, RNCs also have the following advantages:

  • Soft handover: By introducing the operating and serving functions of the RNC, distribution of traffic volume is more easily managed because the RNCs are allowed to compensate where another is lacking
  • Future-Proof Interfaces: Interfaces in this third-generation model have been designed so that the introduction of future services will not affect them as they did with BSCs
  • Packet Transport Network: RNCs also enabled the use of packet transmission technology through which larger volumes are packaged together and transmitted in a more efficient fashion

Staying Current

If you are reading this article, you are likely someone who is either studying telecommunications technology or is already involved in the field and wants to better educate yourself on the more recent evolution in cellular systems. As technology is constantly evolving, architects are continuously striving to anticipate future challenges and develop more complex, adequate systems to meet increasing and changing demands.

Though it seems that RNCs are sufficient to support today’s telecommunications demands, much like the architects of the BSC, it is impossible to totally anticipate what alterations will be required to accommodate the future.

Therefore, if this is your field, it is crucial to pay attention as much as possible to the ways in which telecommunication is changing and what they may require in terms of changes to cellular systems.

The Value of Understanding the Now

It appears that this third-generation cellular systems model and the role of the RNC is here to stay for the immediate future, so there’s no better time than the present to familiarize yourself with its technical structure. We hope that this breakdown of RNCs and this brief history of telecommunication systems’ evolution has provided you with a more well-rounded understanding of the role of RNCs and why their development was so important.

Any Further Questions?

Q-1. When were the UMTS system and the introduction of the RNC?

The first UMTS system was introduced in Norway in December of 2001 and has become the standard cellular system model over the past two decades.

Q-2. What new technologies that I might be familiar with were made possible by the change to the UMTS system?

UMTS systems emerged in order to accommodate the introduction of 3G cellular technology. Now, much of the world has moved on to 4G, offering greater access at higher speeds and will likely remain the standard as we begin to introduce 5G capabilities worldwide.


  • https://en.wikipedia.org
  • https://www.idt.com
  • https://www.sciencedirect.com
  • https://www.ti.com
  • https://pdfs.semanticscholar.org

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