Chris Kelly

Preparing Your IoT Designs for the Interference of Things

Blog Post created by Chris Kelly Employee on Dec 21, 2016

Future projections for the Internet of things (IoT) are staggering: billions of devices around the world, with 500 residing in a typical home. That’s why the wireless designers I know are preparing their devices for the Interference of Things—and they’re doing it early in the development process. This is especially important for IoT widgets intended for mission-critical applications.

 

A recent customer visit drove this point home. They had released a new healthcare-related IoT device that uses Wi-Fi to send information to a centralized database. Even though testing in the lab went well, the device was consistently losing connections due to interference from myriad onsite devices—literally 913 devices on Wi-Fi alone in one hospital. When we met, our customer had an urgent need to resolve this problem and recover from the figurative black eye it had received from hospital administrators.

 

Troubleshooting with 20:20 hindsight

After the fact, avoidable problems in receivers, transmitters and the RF environment may suddenly seem obvious. In a receiver, blocking is related to its ability to tolerate strong or local signals on adjacent channels that use the same standard or protocol. When an adjacent signal is too strong, the receiver becomes so desensitized that it can’t recognize an on-channel signal.

 

An ill-behaved transmitter has a poor adjacent-channel power ratio (ACPR) when too much of its signal spills into neighboring channels. That’s one reason why we see ACPR in virtually every wireless standard. In a noisy wireless environment like a hospital, better ACPR helps improve overall system behavior.

 

In today’s airwaves, one issue keeps cropping up: the overabundance of standards- and non-standards-based devices clogging up the industrial, scientific and medical (ISM) band at 2.4 GHz. Devices that use different standards simply see each other as interference and thus don’t play well together.

 

Using foresight to design for interference

Long before a wireless device enters field trials, developers can explore potential issues using the latest design, simulation and test tools. These enable such extensive wringing-out—ranging from obvious to insidious—that a manufacturer can send its prototype into the field with much greater confidence that it will perform as intended.

 

Of course, there’s an important reality check: Where does your IoT device reside on the continuum between mission-critical and throwaway? The economics change significantly if your device trends towards either end of that spectrum.

 

The IoT device in my story would have fared much better in the Interference of Things if it had been debugged early on using a more thorough approach to design, simulation, emulation, test and analysis. An integrated IoT solution is a crucial step toward overcoming likely IoT challenges—and setting up your IoT end users for success.

 

What approaches have you used to set yourself up for success in IoT and other wireless products?

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