A brief history of the radio access network

How did openness and virtualization become key to mobile connectivity? Time to explore the evolution of RAN technology and the current state of play involving SDN, NFV and multi-vendor ecosystems.
A book and glasses

My column this month is perhaps not for the faint-hearted. In the past, I’ve avoided some technical babble but I think, on this occasion, it is warranted.

ADVA joins the O-RAN Alliance

You see, I plan to write a series of posts that tackle a lesser known yet significant component of the cellular network infrastructure, namely the radio access network (RAN). The RAN has garnered some momentum and attention this year, due to the excitement surrounding 5G – the next generation of cellular technology. In particular, we’ve seen the emergence of several new software algorithms and buzzwords, such as Open RAN, the O-RAN Alliance (not to be confused with Open RAN, but more about this in another post); virtual RAN (vRAN) and cloud RAN (cRAN), which all seem to be a collective melting pot of confusion. 

So, this is where I would like to provide clarity as to the various options that are available to vendors. But first, I’d like to explore the cellular infrastructure and, in particular, to take a closer look at the technological marvel of the RAN, exploring its history and the evolutionary steps that have led us to today’s 5G RAN over a series of three of four columns, along with exploring ADVA’s recent announcement regarding the O-RAN Alliance. 

The shift from analog to digital

The RAN has been intrinsic to all generations of cellular technology, that is, from the first (1G) through to today’s fifth generation (5G). It has, likewise, evolved gradually over a number of years where the Third-Generation Partnership Program (3GPP) has extended its functionality, as well as the core network (CN) to provide extended network operations and applications. The evolutionary shift started to emerge with the introduction of packet-switched data in the core network, which was prominent in the second generation (2G) RAN technology and, in turn, improved data traffic throughput. 

With the arrival of third generation (3G) cellular technology, additional evolutionary steps resulted in several algorithms being developed to aid in providing lower redundancy and higher spectral efficacy which, in turn, improved data ranges and cemented the foundation for realizing a tangible reality for mobile broadband. It wasn’t until the appearance of the fourth generation (4G) technology however, that the 3GPP introduced the Long-Term Evolution (LTE) RAN where the RAN itself and the core network differed from earlier systems. 

Moreover, the existing telecommunications system would respectively carry voice and data separately over a circuit- and packet-switched channel, of sorts; and, as maintaining these delivery techniques over 3G had proved difficult to manage, a change in transmission was needed with the introduction of 4G.

Virtualizing the 5G RAN affords flexibility

You might recall that circuit-switching techniques were used in early telephone systems, where the same technique was carried over to cellular phones. A circuit would be established and routed to its destination, but the connection remained static and the resources could not be reused by any other device once established and in use. As such, with LTE, the 3GPP decided to disband circuit-switching and instead utilize packet-switching only, for both voice and data. However, legacy support is still needed if a 4G cellular device needs to handover from 4G to a 3G network. 4G wholly relies on packet-switching technology for both voice and data over an IP network.

The 5G RAN has been completely remodeled, especially considering the introduction of newer techniques such as software-defined networking (SDN) and network functions virtualization (NFV), which are promoted by the O-RAN Alliance. Using both SDN and NFV provides flexibility in terms of scalability as the network grows, with open source and open interfaces, in turn, easing the distribution of new technology and services. The O-RAN Alliance, for example, are eager to support an open ecosystem, enabling multi-vendor development using off-the-shelf hardware, which allows greater interoperability of multi-vendor components for the cellular network. A virtualized RAN inevitably assures cost-effectiveness from both a software and hardware perspective, in turn, affording your ecosystem that flexibility needed when deploying and developing new services and applications that might utilize the network.

Until next time …

Admittedly there are many terms that I have touched upon and not explained fully in this column, but I will break these down in my forthcoming posts exploring the RAN and its peripheral components over the next two or three months. I’ve described the evolutionary steps taken towards 5G and the upgrades that have realized today’s RAN, as well as other dependent components of the network. So in February, I’ll explain the key components further and breakdown their individual responsibility, revealing how, holistically, they provide us with a seamless cellular service. 

Let’s be honest, 2020 has largely been cancelled for most of us but now, with the emanation of several Covid-19 vaccines, we can all hope to return to some kind of normal in 2021. With this in mind, for my next post, I’ll be heavily armed with a crystal ball when I take a peek into what we can expect from the wireless and telecommunications sector next year.

So, this is where your “predicting the future” Dr. G signs off.

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