Six steps to create a wireless LAN

Wireless LANs are deceptively simple to create. Follow our guide to ensure your WLAN has perfect coverage, can handle your applications and is easy to manage.

Wireless connections are moving out of business's conference rooms and becoming a primary method of connecting to the Internet in the office. But while putting a wireless access point (AP) in a conference room is fairly easy, setting up a pervasive wireless LAN for businesses requires careful planning that involves six steps

Step One: Determine your required capacity

Your first step should be to figure out how much capacity you need and where it will be needed. In many cases, just getting APs to cover your office isn't all that difficult -- the challenge is to make sure there are enough access points, and in the right places, to accommodate your client's needs.

Capacity planning has several elements.

For instance, in areas where the WLAN will be used as the primary mode of accessing the LAN for mission-critical situations, you should ensure that there is enough redundancy so that no single point of failure or congestion can take down the connection, said Craig Mathias, principal at Farpoint Group, an analyst firm specializing in wireless LAN for businesses.

A typical density is one AP per about 280 square metres, Mathias said, although in some situations companies may have an AP for as few as 90 square metres. Ensuring redundancy doesn't necessarily mean getting more APs, he said; your client should also consider an AP with multiple radios, in case one fails.

Because different WLAN devices have different capacity needs -- and abilities -- you should also talk with your client to understand what will be connecting to the WLAN and how that is expected to change in the future, said Lisa Phifer, vice president of Core Competence, a networking and security consultancy. It's important to find out not only what devices will be used, but what traffic they'll generate. For instance, some laptops may be used just for occasional email checks or light Web surfing, while others may be downloading streaming video. If you are considering a Voice over wireless LAN (VoWLAN) system, you should know how many devices they'll need and where they're likely to be concentrated.

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Step Two: Site survey

Once you have a sense of your needs, you should do a site survey, Phifer said. A site survey consists of deploying a few APs in key areas around your office and testing signal strength throughout the area. That is usually done by installing surveying software onto a laptop or other mobile device and walking around the site, letting the software log signal strength as you go.

Doing a site survey can prevent deploying a WLAN that ends up having some areas with poor performance or no coverage at all, Phifer said. It can also identify rogue access points that could pose a security risk. Most of the time, those aren't installed with any bad intent, Mathias said: An employee may have just brought one from home. Still, an unauthorised access point on the network provides an opportunity for hackers to break into the network.

Site surveys can be costly, and coverage isn't a difficult problem with wireless LAN for businesses, Mathias said. He suggested doing only a rough survey or none at all unless your client's building has features that may interfere with coverage. For instance, a hospital may have thicker walls or lead shielding in radiology rooms that can interfere with radio frequency (RF) signals. If your client's site is just a standard office with open space except for a few steel beams, you should focus more on capacity planning, Mathias said.

Step Three: Refine your survey to take your applications into account

A site survey is especially important if you plan to use voice-over-WLAN (VoWLAN), said Michael Brandenburg, an analyst for the enterprise network systems group at Current Analysis. Setting up VoWLAN means you will have to ensure coverage for your client not just in the usual places, but in harder-to-reach spaces like stairwells, he said. One vendor found that only about 15% of businesses had the full coverage needed for VoWLAN, Brandenburg said.

Step Four: Install the access points

Once you have a sense of where to put access points, the installation itself is fairly straightforward for an engineer trained for the hardware, Brandenburg said. But after you deploy the access points, it's important to revisit the site survey to make sure the APs are covering real usage, which can be hard to accurately predict. Planning a business wireless LAN is only about 90% accurate, he said, so you should assume you'll need a few more APs than your calculations suggest. It's a good idea to buy about 20% more APs than you anticipate needing, Mathias said.

Step Five: Consider interoperability

Another important factor is compatibility with other infrastructure, such as the existing wired LAN. As you consider which WLAN vendors' products to use, you should take into account what vendors you already work with for switches and other network hardware, said Steven Schuchart, another analyst for the enterprise network systems group at Current Analysis.

This can be especially important with VoWLAN since each vendor's products have quirks. Even if your WLAN and VoWLAN devices are both standards-compliant, you should make sure they're certified to work with each other, Schuchart said.

Step Six: Consider management and maintenance

Lastly, don't overlook the maintenance software. Ongoing maintenance and configuration is a major cost of running a wireless LAN for businesses, so make sure your vendor's tools fit your client's needs. WLAN management tools are for the most part separate from those of a standard LAN, although some of the larger vendors -- which manufacture both wired LAN and WLAN products -- have begun integrating the two, experts said.

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