If the projections for the volume of the Internet of Things (IoT) actually happen, we will have tens of billions of devices, mostly wireless, vying for spectrum space amongst what will be an increasingly noise environment. That’s the bad news. The good news is that the IoT movement is going to be good for most players in the electronic industry. How do we deal with the potential bad news?
Noise is unwanted signals generated by electrical and electronic equipment. Interference is one signal on the same or a nearby frequency that disrupts the transmission. Let’s talk about the noise first. It comes from many sources. A large percentage is derived from the ac power line. Impulse noise caused by high-voltage transformers with poor connections; motors and other devices turning off or on; fluorescent and neon lights, welders, CFLs, light dimmers, HVAC systems, and connected appliances like microwave ovens make up most of it. But now we have to include practically every electronic product, most of which have a switching power supply. TV sets, computers, printers, audio systems, and smartphones all have a switch-mode power supply (SMPS). We also have inverters in UPS and solar power systems. Switch-mode power supplies are major generators of impulse noise with heavy harmonic output.
What all these devices do is collectively produce a noise floor above the natural thermal noise floor all radios have to deal with. And imagine this noise floor continuing to increase year after year as more and more electrical and electronic devices are put into service. The result is that wireless communications will be disrupted. Some transmissions will fail completely. Some will make it through after several tries. Others will endure a lower data rate or just be delayed.
Luckily, most of this noise is worse at the lower frequencies, less than, say, a few hundred MHz. Noise tapers off above that as harmonic content amplitude of impulses continues to decline with frequency. Good design will also help mitigate noise. Use the three standard solutions to EMI—shielding, filtering, and good grounding—and it will help.
As for interference, it is a fact of life in the shared unlicensed spectrum. If two radios are near one another and on the same or close frequency, both radios will be affected. Most wireless technologies incorporate some co-existence methods to reduce interference. Furthermore, the use of low power helps. The range is also limited so interference is usually only a problem with devices that are very close.
Up to now interference has not been a major problem. But when the number of devices increases by an order of magnitude or more, this will become a major issue. And it will be especially felt as multiple IoT radios will be interfering with one another as well as increasing the impulse noise level as they turn lights, HVAC, door locks, and appliances off or on.
My guess is that this may not be as bad as it sounds, but the whole issue is something to think about as you design your IoT products.