IoT: Solving the problem of connectivity on the move

Twilio's 2018 Signal event had a lot to offer the IoT world, with two new additions to its Programmable Wireless family.
Written by Simon Bisson, Contributor

Mobile devices are everywhere, embedded in everything from cars to homes and beyond. We're soon going to be living in a world where billions of devices share the same mobile networks as our phones. It's going to be crowded out there.

That brings us to an interesting set of questions. If we're going to have billions of connected devices, how are we going to connect them, and how are we going to manage them?

I recently attended telephony API specialist Twilio's annual conference, Signal. Along with enhancements to its familiar set of telephony APIs, the company used the event to announce two new additions to its Programmable Wireless range of products, continuing a focus on connecting and managing the wider Internet of Things.

One problem facing developers building cellular-connected IoT devices is roaming. Connecting devices to one network makes it expensive to roam globally, with international data costs quickly adding up. One option is multi-SIM devices, like Apple's newest iPhones, but there you're having to add additional hardware to support each SIM, and software that can switch providers as required.

​Twilio's new Narrowband LTE SIM

Twilio's new Narrowband LTE SIM


Instead, in its new Super SIM, Twilio is implementing multi-IMSI support. The IMSI is the network identifier used to associate a SIM with an operator. By programming multiple IMSIs onto a single SIM, it can automatically switch to the most appropriate operator, taking advantage of local rates. The company's original SIM, while offering competitive global rates via T-Mobile, wasn't able to get the same reach as one that also works with global carriers Three, Singtel, and Telefonica. With four carrier options, each with its own roaming services, Twilio can use software on the SIM to switch to the appropriate carrier based on where it is.

As it's using software and a table of appropriate operators, it's easy enough to update the on-SIM tooling to handle new partners and new roaming arrangements. All that Twilio needs to do is add new IMSI information to its SIMs when it inks new deals.

You can think of the Super SIM as a SIM that self-arbitrages its connectivity to the most cost-effective operator, backed up by a cloud service to manage and control the SIMs. Mixing cloud and mobile gives Twilio access to a significant amount of debugging information, letting it improve its routing tables and providing better access to the Internet by managing the APNs associated with an IMSI.

The Super SIM also extends Twilio's existing Programmable Wireless APIs, giving you global access to your devices either via IP connections or by sending SMS messages. SIMs can also be pre-programmed with X.509 certificates to improve application and device security -- including support for VPN tunnels. The APIs give you access to your SIMs, the account details associated with an individual SIM (including its rate plans), as well as control over your devices via low level commands.

SEE: Cybersecurity in an IoT and mobile world (ZDNet special report) | Download the report as a PDF (TechRepublic)

SIM-level commands are a useful tool for controlling devices out-of-band. Your IP-based networking code in an IoT app won't be able to control the cellular network connection, so SMS-based connection queries can check the APN settings of a device that's on but not on line, and if necessary change them to an APN that will work.

The Super SIM is interesting, and solves a lot of mobile connectivity issues for IoT hardware. But not all IoT systems need a full IP connection, whether it's slow 2G or high speed LTE. That's where Twilio's other Programmable Wireless announcement comes in, with support for the Narrowband LTE standard.

Narrowband LTE is an interesting approach to delivering mobile connectivity. Instead of taking the whole broad LTE band, it uses a much narrower set of frequencies to handle low-bandwidth connections. There's a lot to like here, as it's more than a radio channel, it's also a set of protocols that work together to significantly increase battery life for mobile devices. It's much easier to set up and tear down connections, and support for non-IP protocols mean bandwidth requirements can be significantly reduced.

Bundling all this together results in surprisingly long battery life. An IoT device that's just sending simple alerts to a central service can offer up to 10 years life with jut two AA batteries. That's a significant saving, especially when we think about devices that will be placed on-site and left unmaintained for years at a time. With Narrowband LTE low-cost radios and cheap connectivity should come together to offer IoT manufacturers a sweet spot that can encourage developers to add sensors to devices that traditionally were uneconomical to monitor.

Working with T-Mobile and Taiwanese maker-board vendor Seeed, Twilio gave developers at its event one of the first publicly available Narrowband IoT developer boards. A simple Arduino-based device, it comes with a Narrowband IoT SIM and a low-cost developer subscription. 2MB of data per month may seem to be very little, but it's more than enough when you're transmitting a few bytes of data a day. You're also operating in licensed frequencies, unlike other IoT wireless standards and services which often need to coexist with other services in unlicensed frequencies.


The Narrowband LTE developer kit Twilio handed out at Signal 2018


The Twilio developer board gives a picture of what you might build and deploy over Narrowband LTE. It comes with a handful of sensors, using Seeed's Grove connector. These include ultrasound, temperature and humidity, and a button. There's also GPS support. It's easy to see how these might be used to build alarms, sensors, and basic location systems; all where the data sent back can be kept small and infrequent.

While Narrowband LTE is gaining some industry traction, it's not the only option. One alternative, LTE-M builds on familiar LTE hardware to deliver higher bandwidth services. As always there's a tradeoff, as it needs to share bandwidth with voice and other data services. A more complex radio environment also means more complex and more expensive radio hardware, making the tradeoff between the two technologies as much economical as it is technological.

With the Super SIM and with Narrowband LTE connections, Twilio now has a suite of offerings that cover much of the IoT mobility spectrum. When combined with the rest of its platform, developers have an interesting set of tools for building apps, and managing the underlying hardware, all through the same set of APIs and in one control panel. That's a very attractive proposition, especially in the fragmented world of IoT networking.


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