Corporate wireless and alphabet soup

Which explains why Meru is doing a big propaganda campaign to get corporates signed up to the new technology, because Meru believes it has the answer: the "virtual cell" - which means you can forget about the wired network and go all-wireless.

You can get all the information you need about virtual cells, on a technical level, from Meru Networks direct. Suffice it to say, here, that it makes planning your office network easier, because it means the net looks like a single access point on a single channel, with the same service ID - and so "roaming" from one to the next is far simpler, without massive work done planning the layout. Normal wireless networks have to avoid overlap; the virtual cell effectively eliminates that problem.

It's my own judgement that Meru has leapfrogged the competition here. That's not to say that rivals like Trapeze and Aruba can't compete, just that they have to polish up their PowerPoint presentations to cover this threat. But all of them are, still, in the same boat when it comes to the problem we started off with: Wi-Fi phones.

The thing about 11n is that it uses ferocious amounts of air spectrum. Earlier versions were positively anti-social, using reflected signals and multi-path channel bonding tricks to soak up every bit of available bandwidth and, in the process, blotting out any 11b and 11g devices in the area.

Meru believes it has a solution to that, but if you talk to its engineers it quickly emerges that they're assuming two things, which may be optimistic.

First, they're assuming that people will use the 5 GHz spectrum normally reserved for 11a. And second, they're assuming that 11b is obsolete and will go away any day now.

The 11a problem is a story for another day. 11n does, in theory, have the ability to select all Wi-Fi channels; the 2.4 GHz channels one through 13 as well as the wide range of 5 GHz channels. Normally, 11b and 11g are stuck in the 2.4 G spectrum; 11a is stuck in the 5 G spectrum.

But 11n can switch between them (although, not in a neat, seamless, virtual cellular way) and so if it finds that there simply isn't any available 11b or 11g spectrum it jumps up and uses the high frequency.

Back to our Wi-Fi phone! Right now, every Wi-Fi phone in existence uses 11b, not the faster 11g. And there's a simple reason for that: battery power. The 11g technology gets its extra speed from a modulation system called orthogonal frequency division modulation, OFDM - a technology that applies to WiMAX too. It works, but there's no free lunch. To get more bandwidth, you have to use more power.

Take a Nokia E61 Wi-Fi phone. It's the basic Truphone toy and I've been happily making VoIP calls over my office Wi-Fi system using it for the last three months without any ill effects. But there is a problem: you have to recharge the thing every night if you use the internet phone call ability. Restrict it to cellular, and the battery lasts most of a week; but even sitting in a Wi-Fi hotspot means you use battery power at four times the rate. Talk, and it obviously burns the battery up faster.

Nobody is going to predict how much battery an 11g Wi-Fi phone would burn, but one engineer described it as "at least double" and then said "and that's probably a conservative effort, assuming that someone actually develops a low-power 11g chip, which they haven't yet." Which probably explains why there aren't any. Imagine a Wi-Fi phone that flattens your mobile phone battery in half a day? Nobody would buy it.

Which means that if Wi-Fi mobiles increase - as everybody seems to believe they will - then 11b is not going to go away. And that means that in the 2.4 G field where 11b operates, throughput will remain low as long as there's an 11b device switched on. The whole network runs at 11b speeds while they're operating in most instances.

So ignore all the optimistic predictions about how fast 11n will go until you've actually tested it. Make sure it will run in both 2.4 and 5 GHz spectrum areas (not all 11n devices do). Make sure it will support your 11a devices if you have any. And test it while your Wi-Fi phone users are making internet calls.

If it can jump through those hoops, buy it. I'm betting a lot of 11n gear won't pass those tests for another two years. ®