SMS and 5G: What You Need to Know

A Q&A with John Hurley of Enghouse Networks

John, can you briefly share a little bit about who you are and what your role is at Enghouse?

I am Chief Product Manager of the VAS and Security Division of Enghouse Networks, which was formerly Jinny Software before it was acquired. I have been involved in and around mobile messaging since 1998, which at times is hard to believe.

SMS is considered a bit of an older technology, but I understand that you believe it’s still evolving. Why is that?

I don’t think SMS itself has really changed that much, but the use cases for it have changed quite a bit.

There are many aspects and uses for SMS that are invisible to people. Two examples are when SMS is used for setting up a new SIM card. or for updating roaming information. The content of these messages is binary code, rather than human-readable text, and they can be targeted to specific ports in the handset that ensure they do not appear on the screen or create alerts like normal SMS messages. Overnight a phone may receive hundreds of binary messages and the owner will never be aware until they are prompted to restart the phone or find it has restarted itself.

If you’ve ever noticed that your phone has restarted in the morning, your operator may have updated its configuration over the air by SMS. In fact, binary SMS messages can be sent over the air to millions of devices and machines at once to update their configurations or prompt them to ‘wake up’ and perform a task.

This is often typical when IoT devices are operating in a low energy mode to conserve power, but when they receive an SMS it triggers them to ‘wake up’ and perform a function, which may even be based on a different technology, such as wireless data. Once that task is complete, they go back to sleep and return to their low-energy mode.

This is an example of how an older technology like SMS can be used to support a new technology like IoT. It’s a small but important role.

So, let’s back up for a moment. You’re saying that our phones are having secret conversations while we’re sleeping? That’s my takeaway.

Yes, in fact, there are millions of machines out there having secret conversations right now. Things like irrigation systems, oil or gas pumping stations, streetlights, and motor vehicles can have mobile modules capable of receiving instructions or reporting their status via SMS.

Railways are another example. There’s a protocol called GSM-R that specifies a special radio network for railways. Within the GSM-R standards, there are a lot of different functions that must be performed by train dispatchers. They have certain safety and performance protocols they must follow. For example, someone must physically stand on the platform and check that all passengers are on the train before closing the doors, and so forth. They push a button every time each of these status items is completed. That button sends a predefined text message to central control, so the guard doesn’t have to type and say, ‘I’m now closing the door and the time is 19:05:52’. Instead, all that information gets recorded automatically and is sent to the lead engineer who oversees that everything is running OK, and the train can go to the next station.  Or an operations center may send an SMS to a signal box to notify train drivers to slow down because there’s congestion or an accident on the rail up ahead, or that crews are working on another rail line.

All of these can be sent via SMS over the GSM-R network. These standardized messages go to terminals that automatically accept and translate them into richer content. It may surprise a lot of people to think that our railways are being controlled by text messages, but that’s the way it is.

Let’s switch gears from train networks and jump into the topic of 5G telecom networks. Right now, many operators are starting to roll out their 5G networks, and some are even looking at private 5G for enterprise customers. What are some of the challenges that they’re going to be facing with regard to SMS? It sounds like many IoT-related devices will still be dependent on this technology. What do operators need to be aware of?

In every market, you have early adopters of new technologies. Some are chomping at the bit to get their hands on a 5G phone to see if it improves their movie viewing or gaming experience. Most of the networks that cater to consumers are hybrid networks that include elements of 4G, and maybe even 3G.  SMS works fine in these hybrid environments using an SMSC – Short Message Service Center, with IMS as the bearer protocol. These have been in use for years and IMS continues to support SMS interworking in hybrid 4G/5G networks.

A new challenge arises in standalone 5G networks – those without 3G and 4G. For SMS to work in 5G standalone, 3GPP has specified a new node called the SMSF. This stands for Short Message Service Function, and it communicates with the legacy SMSC at one end and with nodes of the 5G core via the NAS (non-access stratum) to enable SMS interworking to and from 5G devices. Non-access means it operates outside the radio access portion of the network. Instead, the functionality resides at the network core. The SMSF acts as a transparent router between an SMSC and an AMF in the 5G core, allowing each SMS to get properly routed.

What about private 5G networks? Is an SMSF required here as well?

Most of the interest in private 5G networks comes from private enterprises or from educational institutions. Let’s say there’s a university campus that’s in quite a remote area and they decide they want to have a private network. This is one case for SMSF, but I think the majority will be in the industrial space; manufacturing companies that have robots operating their production lines, or wherever there are difficult tasks that humans simply can’t do.

During production, there may be times when these robots and other machines need to be reprogrammed. Instead of a person manually doing this one by one, instructions can be sent instantly over SMS. If these robots are indoors this could be done over a broadband Wi-Fi network instead. It wouldn’t necessarily have to be SMS. But for machines or ‘things’ that are moving around and not part of a Wi-Fi network, over-the-air (OTA) programming through SMS would be vital. And SMS tends to be more reliable and requires less power than data, so that should be factored into any decision as well.

Oil and gas exploration companies are another prime example where SMS makes sense. They may be pumping gas across pipelines, or have drills located in remote areas and need to monitor criteria like pipe pressure, throughput, and temperature. 5G coverage can be placed along these pipelines to monitor sensors without using a great deal of energy the way earlier generations might have required. 5G is also suitable for providing IoT coverage along railways and roadways for devices that need to report back about status or perform certain tasks.