How to survey your site for WLAN

Everywhere you turn the buzz is about wireless LANs. Companies are deploying them everywhere: from boardrooms to branch offices to warehouses. But it’s important to remember that the technology is only as good as the original site survey.

Tom Henderson, principal at ExtremeLabs and member of Network World’s Global Test Alliance, and I just wrapped up Network World’s four-city Wireless LAN Technology Tour. And in each city we encountered network executives who had forged ahead with wireless LANs only to encounter problems that forced them to backtrack.

For instance, one attendee who works for a tool manufacturer said he wanted to add wireless in a company warehouse so he bought the equipment and went about setting it up. But he quickly found the high metal shelves caused severe interference – a problem that is forcing him to rethink his overall strategy.

A wireless site survey would have saved him the hassle. And from what Henderson pointed out on the tour, conducting surveys is not that difficult.

The first thing to determine is how much signal noise you’re going to encounter. If you’re deploying 802.11b equipment, you obviously want to avoid microwave ovens, cordless phones and other devices that operate in the crowded 2.4 GHz frequency range. But you also need to think about physical obstacles such as shelves and even elevator shafts. Henderson says to pay attention to everything, even wireless surveillance cameras and neighboring 802.11a/b networks.

Next you want to determine your access point layout.  The site survey will help you determine where you need nodes to achieve the coverage desired, but you also have to take into account simple connectivity, both to the wired network and to power sources.  Regarding the latter, some systems let you run power over Ethernet connections, which simplifies wiring requirements.

Keep in mind that difficult situations might call for alternative tools.  For example, rather than putting up unnecessary access points, you might be able to employ specialized antennas to cover greater spans.

Once you’ve laid out your criteria and taken note of interference issues, physically map it all out and make several copies – one for contractors, one for the physical plant staff, one for your staff and one for safekeeping.

If you take these steps, chances are you’ll have a more successful wireless experience than if you were to proceed ad hoc. Backtracking, after all, is always more difficult than preplanning.