Cellular IoT Testing: Things that Go Glitch in the Night

Navigation system in an automobile

Recently I was with an automotive Tier 1 in the Detroit area. They are infotainment experts, and their latest product integrates an LTE cellular module to deliver streaming radio and other services. The development team, experienced hardware and software developers all around, were using the real cellular network in their local areas to check out functionality. And why not use Sprint or Verizon or whatever fine local network is nearby? It’s certainly cost effective to test cellular IoT devices using this type of connectivity.

The challenges of testing cellular IoT devices on a live network

There was an insidious problem. The QA lead conceded that they were seeing rare intermittent issues and they were eventually writing them off as problems with the cellular network. What kind of issues? Once in a while, the Pandora playback would stutter, or the Wi-Fi connectivity would lock up for a bit.

Debugging an intermittent communication issue is hard enough on a good day. At least with a short-range technology like Wi-Fi, you can lay out all the elements (device-under-test, network, cloud server) in your lab and isolate issues. But if you’re testing on a live cellular network, you can see the packets up to the device-under-test’s modem, and you can see what hits the cloud server, but you can’t see what’s happening “on the wire” (or in this case, over the air).

So figuring out if the issue is truly a network “glitch” is too hit and miss. And designing software that is robust to network glitches is almost impossible, as you can’t predict if or when the live network reaching your test lab will experience high cell loads, RF interference, core packet loss, or a myriad of other issues.

“Why not use a network emulator?” I asked. The team felt that network emulators were too complex, and wicked expensive. “The RF compliance team uses them, but they’re not practical for dev teams.”

Network emulators save time and money during cellular IoT testing

Times have changed. Spirent has helped teams like this cut months off their development time and avoid potentially harrowing field issues that come with cellular deployments. Because nowadays there are desktop network emulators that are the size of a set-top box and affordable for almost any development team. Spirent’s Elevate IoT Device Test Solution, for example, gives repeatable connectivity right out of the box, lets you see the packets that your device exchanges across the wireless link, and allows you to put your design through the conditions it’ll see in the real world.  Read more about how this solution saved time and effort for one IoT app developer in our connected car case study.


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