High-speed Wi-Fi raises early concerns

The new high-speed Wi-Fi standard, 802.11n, has been controversial to say the least. Although the standard is only due to be ratified in 2009, a plethora of 802.11n-based products is already on the market, leading the Wi-Fi Alliance to start "certifying" equipment that conforms to a draft version of the standard.

The controversy and doubt around 802.11n has led some vendors, including Motorola, to turn their backs on the standard until it is ratified, while companies such as Dell have leapt to its defence, claiming it is sufficiently stable.

Chia Chee Kuan is chief technology officer and co-founder of AirMagnet, which makes products to help IT professionals plan, deploy and monitor wireless networks. ZDNet.co.uk caught up with him on Monday to discuss the advantages and pitfalls that await those considering early adoption of 802.11n.

Q: Has AirMagnet taken the leap to 802.11n yet?
A: As a vendor in the Wi-Fi space we very much support 802.11n. We have that commitment to our customers. We haven't announced any 802.11n products yet, but we are working on it. There is hardware available for us to use, and we monitor 802.11n traffic even though our customers are not deploying it yet. The way we look at 802.11n, there are several issues we need to help our customers resolve.

Even though they may not be interoperable, there are 802.11n products on the market. We haven't seen our customers jumping in and deploying 802.11n yet, but a lot of our sites do see 802.11n products being put in by their neighbours, which could interfere with their 802.11a/b/g usage. In theory they should not [interfere] but, at this point, no-one knows how the vendors are implementing 802.11n, so we are very closely monitoring Layer 1 and Layer 2 to spot issues.

What issues have you spotted so far?
Right now we're not ready to identify any problems, although we do see suspicious areas that, if not implemented carefully, could cause some interference. Although 802.11n has a lot of built-in backwards-compatibility features, what we are watching out for is [whether this is] being implemented correctly. [The issues] are vendor-specific and we are not ready to name vendors at this point.

Are these products certified by the Wi-Fi Alliance?
I am not sure if they are certified or not. It is likely that they are not, as the equipment was acquired before the certification programme was announced. But a lot of these products are already on the market.

What pitfalls should IT professionals look out for if they are deploying 802.11n?
Once enterprise starts to want to deploy 802.11n, there are deployment differences between "n" and the rest of 802.11 technology. The first thing that people would usually need to think about is channel usage. 802.11n has an optional feature called "wide channel", which operates at 40MHz as opposed to the 20MHz used by 802.11b/g.

The implication is that, if you really want high throughput, you need to consider using the wider channel, but you [would therefore] have fewer channels to use. For example, at 20MHz per channel in 802.11g, you have three non-interfering channels, but you only have two such channels for 802.11n if you want to use 40MHz for higher throughput. By using [wide channel], you could potentially interfere with other devices, so the rule is: don't go into wide channel unless the channel is clear.

The other example is that 802.11n has beam-forming capability — it has the antenna that can beam the radio frequency signal directly to the recipient. By doing so it reaches further and is more efficient, but [this is a] different characteristic to 802.11b/g. If you currently have 802.11b/g and want to upgrade to 802.11n, you cannot necessarily put an 802.11n access point in the same location as the 802.11b/g access point — you may have to do a different kind of deployment planning.