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Monday, 21 May 2012

New 802.11ac routers herald next-gen Gigabit Wifi

I've had a few press releases about new 802.11ac ('Gigabit Wifi') routers recently, which is great news - you don't get a brand new generation of wireless networks appearing every day. Although it's largely based on 802.11n, but with wider channels (it only uses the 5GHz frequency), 802.11ac adds some other interesting tricks to improve throughput and reliability. But until I see some actual products, it's fairly obvious that I can't say how well they are going to work in practice.

Using the 5GHz band exclusively might give a little less interference in those places where 5GHz is currently viewed as witchcraft, but in my home there are at least 2 other 5GHz routers nearby that sometimes cause me headaches during router testing. Virgin Media and BT both now supply dual-band routers as standard, I believe. And as device penetration increases, it won't be long before the 5GHz band is just as crowded as the 2.4GHz band (if router manufacturers only enabled the 2.4GHz band by default, the situation wouldn't be as bad, but I can't see them doing that and risking the irate 'where's my 5GHz??!!' support calls). Add to that the fact that a single router could in theory use up the entire 160MHz spectrum in the UK, and it's going to be fun. There's talk of it becoming the standard in mobile devices, set-top boxes and other consumer electronic items, which will only add to the congestion.

Netgear's R6300 could be one of the first 802.11ac routers to hit the UK

There are lots of technical options, such as short guard intervals and modulation schemes, for giving a wide variety of link rates from a single configuration in 802.11ac, which will probably mean great confusion at the lower end of the market with single-stream products. The real benefit of 802.11ac will probably come with multi-stream devices that can implement the multi-user MIMO (MU-MIMO) part of the spec and  use beamforming to more accurately target clients.

This should improve reliability, if not throughput, but there's not much that can be done to improve the range of 5GHz signals, given the UK regulations on transmitter power . In some of the white papers I've read, they seem to suggest by starting with a higher throughput, the fall-off takes longer to happen, effectively increasing range. Perhaps, but you still need a signal to get any throughput at all. Let's see what happens when 802.11ac meets the two brick cavity walls and glass patio door in my standard test area (otherwise known as my home). So far, the best 5GHz 802.11n systems I've tested have matched the best 2.4GHz results at 25m range, but that's quite rare - most routers I've seen struggle to connect at more than about 10-15m. Interestingly, the ones that worked best at 5GHz were Belkin's latest models (particularly the Play N750-DB) which use some kind of beamforming.

But let's not get too alarmist before we've seen the actual products in action - and that might be a couple of months yet. The three companies who have made announcements all vaguely talk about the third quarter of 2012 before products arrive in the UK, so hopefully I can get  my hands on some during the summer. In the meantime, you can read a little more about the promised products in a piece I wrote for ZDNet's Firsdt Take blog.

For those interested in the technicalities of 802.11ac, there are a couple of decent white papers here and here.

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