Solving The Next Great Wi-Fi Challenge: Interference
Radio-frequency interference is the carbon monoxide of the wireless world – invisible, tasteless, odorless, arriving without warning, and with the ability to really ruin your day – unless you know the symptoms and have the right tools at your disposal. And that’s just what we have for you in this new series of articles from noted wireless expert Craig Mathias of Farpoint Group.
Over the past 25 years, the spec’ed throughput of wireless-LAN systems has increase by a factor of roughly 7,000 – from less than a megabit when Farpoint Group was founded in 1991 to today’s close-to-seven Gbps possible with 802.11ac and .11ad products.
And while performance numbers of this type are at the very least fun to discuss, they also represent the upper bound on speed – what I like to call the performance level that the marketing department at a given system vendor guarantees their product will never exceed. And, indeed, we’re all used to get less than full rated performance given the many vagaries of radio itself – but mobility and convenience go a long way towards helping us live with all this variability.
Still, we’re always working to minimize the impact that radio-related issues have on throughput and especially capacity. We’ve improved radio architectures, antennas, protocols, and much more. But it’s, again, the fundamental nature of radio itself that gets us – and the biggest problem of all here is the little-understood element of radio (or RF) interference.
What is interference? Well, it’s two radio signals at the same frequency attempting to coexist simultaneously in physical proximity and causing attempted communications to fail. A simple example: how come we can’t see the stars during the daytime? The Sun is “broadcasting” on the same frequency as the stars, but with a relatively much more powerful signal. The stars are still shining away, but the Sun is interfering.
The same can happen in radio communications as well – one signal overwhelms or at least damages the other. Sometimes interference is mutual and nobody goes home happy.
And – here’s the bad news – with the overwhelming success of wireless communications, the problem is getting worse. Fortunately, as we’ll discuss in this series of articles, the interference challenge can be addressed, albeit with a little bit of work.
But let’s start with the basics. There are, in general two kinds of bandwidth (or spectrum) where radio waves can operate: licensed and unlicensed.
- Licensed bands of spectrum are assigned, for example, to cellular carriers who pay very big bucks for them, and interference is easier to manage here – as in there really shouldn’t be any, and, if there is, a law is likely being broken.
- The unlicensed bands, on the other hand, are made available on an as-is basis, and the potential for interference fundamentally comes with the territory. Wi-Fi and other devices operating in these bands (and these are the only bands we have) must accept and deal with interference as a matter of law.
Most interference is unintentional – other Wi-Fi systems attempting to peacefully coexist, incompatible and thus uncooperative technologies like Bluetooth, and a wide variety of other consumer and business products, not all of which are used for communications.
It is also possible to generate intentional interference, as in jamming – but such is usually illegal and, as we’ll discuss in a subsequent article, fairly easy to detect. And I’ve personally never experience intentional interference in the wild, so hopefully this form of electronic warfare will remain strictly in the domain of military applications.
But by far the biggest problem we face today is simply the large number of independent systems – and again, not just Wi-Fi – competing for capacity in the unlicensed bands. This is, of course, a symptom of success; Wi-Fi is today, after all, really the only access that matters. But, make no mistake – there’s a big threat here, and we’ll explore the issues, opportunities, and, yes, solutions in this series of articles.
Just like real estate, they’re not making any more radio spectrum, so, one way or another, understanding and managing this issue should have priority in every organization today.
In my next installment of this 5-part series on the challenge interference poses to Wi-Fi, I will cover symptoms and detection.
All Posts In This Series: