Worldwide Interoperability for Microwave Access, since you ask. It's overseen by The WiMax Forum, an alliance of more than 400 companies working towards compatibility under the IEEE 802.16 standard. It's a bit like Wi-Fi (a.k.a. 802.11), but, for one thing, the range is calculated in kilometres (theoretically about 50) rather than metres. It's also far more reliable than Wi-Fi, especially when using applications such as VoIP that require high bandwidth and consistent quality of service (QoS).
Why should I worry about it?
Chances are you may not need to lose any sleep for a while yet. That's because the current standard, 802.16-2004, only deals with fixed systems and is probably going to prove most useful for communications companies. For example, it's a quick and relatively cheap way to provide high-speed "last-mile" connectivity (also known as backhaul) between remote rural areas and the main backbone of the internet.
Similarly, it makes a lot of sense as a solution for areas which lack a decent existing communications grid, such as vast swathes of South-East Asia and Africa. Why invest billions in copper wiring when you can skip to the wireless generation for a lower cost?
However, the next amendment to the standard — 802.16e — is a different story. That's when WiMax goes mobile as well as fixed, and you start to see people talking about maintaining a seamless broadband connection while travelling from office to office on the train.
While you can already buy 802.16-2004 equipment, 802.16e kit is just starting to appear. You can expect to see lots of it in the next couple of years, though, as it's being heavily backed by the likes of Intel and Motorola. Look out for PCMCIA cards and USB dongles by the end of 2006, 802.16e-enabled laptops next year and phones by 2008. It's important to note that 802.16-2004 and 802.16e equipment are incompatible.
We just started using 3G! Why not stick with that?
This is currently the million-dollar question. As 3.5G (or HSDPA, or super-3G) rolls out this year, users will see "broadband-equivalent" speeds on their laptops and phones. The network operators have already spent a fortune on their 3G licences and, for them, switching to 3.5G involves little more than a software upgrade. Installing a WiMax network would mean spending money on a whole new infrastructure, so if the customers don't notice the difference, why worry? This is, for now, the big obstacle to the uptake of WiMax in the UK (although it is worth noting that players like BT, who lack a mobile arm in their portfolio, are enthusiastic members of the WiMax Forum — stay tuned).
On the other hand, even 3.5G becomes problematic when you want to use bandwidth-hungry applications such as VoIP, which also require consistently good QoS. For instance, Skype will work through HSDPA (if your network doesn't block it for fear of losing voice revenue), it just won't provide the consistency of quality that many business users expect from their telephones. It'll also work on a Wi-Fi-enabled "dual mode" phone (such as those emerging from Nokia and Netgear) but, if the hotspot is relying on asymmetric ADSL, the upload speed and general reliability are still lacking. WiMax, on the other hand, is symmetric, making it the ideal backhaul for future-proof hotspots.
It's 802.16e that could turn out to be the real 3.5G-killer, though. It's more secure than either fixed WiMax or 3.5G, it has better coverage than fixed WiMax (thanks to MIMO technology) and, above all, its speed and reliability make it true mobile broadband.
Is WiMAX a replacement for fixed broadband then?
Yes and no. It's certainly worth it if you live in an area where high-speed fixed broadband is a tricky proposition. It's also great if you want to get home broadband but can't be bothered with getting cable or a phone line. However, if you already have faster than 10Mbps connectivity through a fixed line, it may not make sense just yet to downgrade to 2Mbps (WiMax's speed, according to real-world tests) to go wireless.
There's one more major factor to consider: if mobile WiMax does everything its promoters claim it will, then customers might be attracted to the prospect of getting one bill for one connection that covers home, mobile, wireless and even office-based connection. You can already get telephony software that can...