You’re sitting with a friend at a café chatting about the latest viral YouTube video, when the lady at the table next to yours begins to talk on her phone.
Only she isn’t talking, she’s yelling. Her voice is far too loud and it’s obnoxious. You can’t even understand your friend anymore. In technical terms, this lady’s voice is causing interference to your conversation. M2M and IoT devices using wireless connectivity deal with the same thing, only Loud Voice lady is some other device hanging around.
In a prior post, we talked about why Ingenu unabashedly loves the 2.4 GHz band. Sometimes we get asked about how busy that band can be and what we do to deal with interference. In this post, we’re going to tell you all about how we handle interference on the 2.4 GHz band when it happens (and it does sometimes).
Interference is an issue any wireless technology will have to deal with, the question is, can it deal with it effectively.
Unlike you and your friend who can just find a table further away, many devices stay right where they are. One of the simplest ways to deal with interference is channel coding, also known as forward error correction (FEC). FEC is kind of like scrambling your message in a fancy and efficient redundant way, and then sending the scrambled message. Sure, some of the packets might get shot out of the air like clay pigeons in a Texan sky, but you are much more likely to get the message through.
The issue some LPWA providers face with FEC (that RPMA doesn’t) is the fact that it requires capacity throughput, that they just don’t have, to encode the data in a redundant way. In other words, dealing with interference is partly a function of your technology’s throughput. RPMA’s throughput is >40,000 bps uplink, and >20,000 bps downlink (FCC). Cellular providers don’t have this issue of course being consumer focused. LPWA providers however, struggle to provide this kind of interference protection with only 1-5% of RPMA’s uplink capacity and 0.02% of RPMA’s downlink capacity. This means RPMA has plenty of room to provide extremely robust transmissions and many other capabilities such as enterprise grade security and firmware downloads. Take that Loud Voice lady!
A naïve approach to protecting against interference like that is simply repeating the message a set number of times, hoping the message makes it through. That’s like you sitting there, blindly repeating what you said from start to finish several times, even if your friend got it the first time, or still repeating the whole thing even if they heard the first half but not the second half. Not only would you have a bewildered buddy, but you would also have wasted everyone’s time and energy. Waste not want not, right? But there’s more to this story.
Continue learning how RPMA intelligently handles interference, by reading our followup blog post, Dealing with Interference, Part 2.