By Yuval Shavit, Features Writer
If your client is thinking about installing a new wireless LAN (WLAN) or upgrading an existing one, you need to consider which wireless protocol to use. Although there are several benefits to the latest WLAN standard, 802.11n, there are also some drawbacks -- most notably the extra power its access points (APs) require. It's important to plan ahead so that your client can make the most of the benefits of 11n, either immediately or in the future.
802.11n is the latest wireless standard
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The primary benefits of 11n are increased capacity and range. Although numbers vary, many analysts say 802.11n has a throughput about four to six times that of 802.11g and about twice the range. A typical 11n AP will be able to support about twice as many devices as an 11b or 11g AP, said Lisa Phifer, vice president of Core Competence Inc., a Chester Springs, Pa., networking and security consultancy.
The downside is that 11n APs also use about twice as much power as 11g, which means they can't be powered by standard Power over Ethernet (PoE). Because most enterprise APs are installed in office ceilings, running a separate power cord to each one would not be practical, said Steven Schuchart, an analyst for the enterprise network systems group at Current Analysis.
Although 11n APs would be able to run off of a proposed extension to PoE, 802.3AT, that extension isn't standardized yet, said Craig Mathias, principal at Farpoint Group, an Ashland, Mass.-based analyst firm specializing in WLANs. Vendors have taken various approaches to this, including extra power injectors, but each has its "gotcha" and isn't necessarily compatible with other vendors' solutions, Schuchart said.
Your client may also have to upgrade its wired infrastructure to realize all of the benefits of 11n, analysts said. Because APs sit on the LAN, a 100BASE-T backbone may not be able to carry all of the increased capacity 802.11n provides. Upgrading to Gigabit Ethernet requires installing new switches, which may be a costly capital expense. On the other hand, installing 11n APs on a 100BASE-T backbone won't cause any harm, other than the backbone ending up as a bottleneck for the WLAN.
You should also consider which your client is planning on upgrading first, its APs or client devices -- or both at once. 802.11n devices are backwards-compatible with the older a, b and g standards on both the receiving and transmitting ends; an 11n AP can also support 11a/b/g devices, and an 11n card can still connect to older APs. Connecting on the old protocols means you won't get the benefits of 11n, but because 11n APs represent the latest technology, even their 11b and 11g connections are faster, said Michael Brandenburg, another analyst for the enterprise network systems group at Current Analysis.
Because you will most likely have to support legacy devices -- either for your client's own use or in case your client wants to allow guest access for people who may have older wireless cards -- you will need to develop a strategy for maintaining 11g and 11n on the APs. 11n APs can operate in dual mode, supporting both standards simultaneously, but you will have to separate the channels for each protocol.
One option is to continue transmitting the legacy 11a/b/g protocols on 2.4 GHz and use the 5 GHz band for 11n, Mathias said. As your client refreshes its mobile devices and more of them support 11n, you can either switch to using 11n on the 2.4 GHz band or keep it reserved for older devices as needed. If you do operate 11n in the 5 GHz band, it's important to do a site survey to make sure appliances like microwaves don't interfere with the frequency, Brandenburg said.
This was first published in February 2008