What's next for Wireless?

Posted on 7 Aug 2007 at 17:48

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The 40MHz channels that 802.11n uses are twice as wide as the 20MHz channels used by older devices. The limitation of the 2.4GHz frequency (smaller channel sizes) means that channel overlapping is more likely. Using the 5GHz frequency, and the much wider channels, virtually eliminates this problem, but it also reduces backwards compatibility. If you drop back to the 20MHz channels on an n network to enable the router to talk to older devices, you'll run into the same interference problems again.

Antennas integrated into 802.11n devices can be used in one of two ways: to boost data transfer rates or to boost signal range. In practice, it is possible for antennas to perform both functions at once. For example, a laptop with two antennas can connect to an access point with three antennas, although the devices can use only two spatial streams. This leaves a spare, unused antenna on the access point, which the device can use to increase the range of its wireless signal. It can also combine two spatial streams into one, which achieves the same effect.

More power

The 802.11n standard is backwards-compatible with a, b and g devices, which means its equipment can operate at either 2.4GHz or 5GHz. When the standard is finalised in 2008, only dual-band equipment will get the official logo, complete with 'n' badge (above). Always keep an eye out for the appropriate letter. Draft-N-compliant equipment may still display the WiFi logo, but it will be tagged with only the letters of the standards the device supports. For example, a Draft 2.0-certified device would have the letters a, b, and g, as well as a little 'draft' next to the WiFi symbol (above).

As has always been the case, if you mix networking standards - such as using g and n devices - you won't gain the full performance benefits of the newer standard. For maximum performance, you need a network made up solely of 802.11n devices.

The g standard has a maximum data transfer rate of 54Mbit/s and an indoor range of 30 metres. Comparing this with the 802.11n standard's performance is tricky because it supports a varying number of antennas and a variety of optional features that users can employ to improve performance or interoperability. This means there is no real standard level of performance for such devices, either in terms of transfer rates or range.

Having said that, the possible maximum performance promised by drafts of the n standard released so far is five times the data throughput and twice the range of the g standard. However, recent tests carried out in the Shopper labs show that rates will probably be much slower in practice. Netgear's RangeMax Next wireless router, which received our Best Buy award (Labs, Shopper, June 2007), managed a transfer rate of 44.77Mbit/s at 15 metres. This test was carried out using a CardBus adaptor of the same brand. In the same tests, the best throughput of an 802.11g product (Buffalo's Wireless G Broadband ADSL2+ Modem Router) at the same range using its own-brand adaptor was 22.09Mbit/s.

Security

Security has always been of paramount importance when it comes to networking, and this applies even more strongly to wireless connections. Despite the fairly limited range of the typical wireless router, there is still the potential for neighbours to connect to a nearby network without permission. The vast majority of networking hardware is distributed with any security features it supports disabled by default, and numerous websites list the default login password for a number of routers, so it is hardly surprising that bandwidth theft is on the rise. In early 2007, two people were cautioned by police after being found logging on to the internet from a car using someone else's connection. The charge was 'dishonestly obtaining electronic communications services with intent to avoid payment'.