Is it Finally Time to Switch off Circuit Switched Networks?

By Mika Skarp

Originally mobile networks were simply built to transmit voice from subscriber A to subscriber B. Today, strange as it may seem, this is the prime bestowed purpose and dominant theme in most network and business planning though the lion's share of the value has moved away from voice and into the cloud of connected devices. And while so far combining Circuit Switched voice and text and Packet Switched data has been fairly seamless, very soon we will have to revisit the core principals that drive network strategic planning in the face of stark financial realities and ever more demanding customers. 

As we speak, most mobile operators worldwide have two completely separate networks; a Circuit Switched network (for voice and text) and a Packet Switched (for data and VoIP). Circuit Switched networks are based on GSM and WCDMA air interface technologies and a common Core Network. The Packet Switched network is based on the LTE (Long-Term Evolution) standard.  Circuit Switched networks have been in development and use going on 20 years now, and are the true workhorses in the system; they are sturdy and reliable, but not very fast or agile. Their younger cousin, LTE, has benefited from the experience of building its predecessor’s networks while being spared the strain of providing basic connectivity or voice. Further still, the network is designed to provide Circuit Switched connectivity as a fallback from LTE if something goes wrong. Again, the older sibling analogy is a good one. Might we say it's maybe about time for LTE to start standing on its own two feet?

While this two-tiered network has up until now been a necessity, running two parallel networks is expensive. As such, it would make great financial sense to shutter the lights on Circuit Switched networks quickly. On the other hand, some Circuit Switched equipment has yet to be completely amortized so they would appear to have some “value” yet un-claimed on the balance sheet. Additionally, there are still huge volumes of subscribers who only use Circuit Switched devices, so the possibility of large scale customer churn is at stake. 

In the latest discussions, it has become evident that Network Slicing has to be kicked off on LTE technology if we want to begin leveraging its benefits any time soon. This is because, according to 3GPP, 5G technology won’t have the required coverage or device penetration for native end-to-end Dynamic Network Slicing prior to 2025 or so. Add to this the fact that from the perspective of Network Slicing, Circuit Switched technology is problematic, especially wherever human users are “at the switch”. Imagine that you have been provided a dedicated a slice that enables you to receive a large data file and then all of a sudden you receive a text message or phone call. As the device is suddenly moved over to the Circuit Switched network, you lose your slice.

Technically, you can solve this problem by allowing "4G-only" mode for the devices getting slices. But the next logical question becomes; why if we can handle the whole works in 4G do we need Circuit Switched networks at all? As networks they are far less efficient. Closing them down would only provide more capacity and at the same time reduce operational strain and expenditure. And the savings would actually be quite high. This is because in our LTE-only situation there would be fewer costly antennas, less floor space needed and less electricity required etc.

To solve the problem of the Circuit Switched (voice and text only) customer, we should provide them with basic LTE phones to keep them happy and less likely to churn. At the same time we can take those frequencies now freed from the Circuit Switched clutches to build more coverage, particularly in urban indoors as well as rural and remote regions, and improve the LTE user experience across the board. This would be only the very starting point for the introduction of new, high value Network Slicing use cases. And while operational cost would lower significantly, customer satisfaction would increase and new revenues stream from Network Slicing would start materializing in short order. If it sounds to good to be true, why not try it and see?