Does 320Mbit Wifi spell double trouble?

US Wifi specialist Proxim claims its mew Orinoco AP-8000 802.11n access point can deliver a throughout of 320Mbits/sec – more than three times faster than a wired network.

The company argues that it is so fast that companies can consider using 11n Wifi instead of a wired network. But the top speed is achieved by using a dual-radio – in effect by using two 11n links at once, and reviving a controversy that dogged earlier Wifi implementations.

Originally 11b Wifi used 20MHz channels in the 2.4GHz band. But by the time 11a and 11g came along, these were being "channel bonded" into 40MHz channels, doubling the throughput but increasing the scope for airwave congestion.

Current 2.4GHz implementations are supposed to revert to 20MHz if there are other networks within range, which is nearly always the case in cities. This is because there are only three non-overlapping channels for networks to choose from at 2.4GHz.

Links using 11a and 11g flavours of Wifi are free to double up to 40MHz in the 5GHz bands, where there are up to 24 20MHz channels available – or 12 40MHz channels. Sorting all this out took a lot of tussling in the standards committees.

But the Proxim access points are aggregating two 40MHz channels, which if everyone followed suit would leave just six-non-overlapping channels at 5GHz.

At the same time the 11n flavour of Wifi is said to double the effective range of the link, which in theory quadruples the area over which frequency contention is likely to occur. And the range is also extended vertically – between, say, the floors of a block of flats.

It has to be said that reports of current 11n deployments are positive, and even using a single radio Proxim claims an impressive 170Mbits/sec throughput. This is the maximum rated speed of its AP-800 access point, sister to the AP-8000, which has only a single radio.

Both are software switchable between 2.4GHz and 5GHz and so can be used with legacy devices.

Comment: Keep Wifi at the edge, Test Bed

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