Site Surveys and VoFi

I think everyone knows by now that I am not a big fan of site surveys for wireless LANs - in fact, I think they are almost always a bad idea, exchanging cheap hardware for expensive labor of doubtful value. Sure, in pathological buildings, a cursory site survey might be useful. And I like doing RF sweeps (with a spectrum analyzer) if interference is suspected. But in the vast majority of open-office installations, site surveys are a waste of time and especially money. One can always compensate for errors in coverage or capacity by simply adding a few more APs - indeed, one should always count on needing to do this whether a site survey is performed or not, because site surveys only take coverage, and not capacity, into account. Yes, I know the installer community makes a lot of money doing site surveys and for them the issue is practically cultural. But think about ROI - do site surveys deliver? Usually not. And please note here I'm taking just about the install-an-AP-and-walk-around site survey, not the overall WLAN installation planning process. The latter remains essential and must consider not just coverage, but also and especially capacity.

But VoFi may be another matter altogether. Because whereas data communications usually has a pretty good tolerance for latency (even if users themselves do not), voice, and, indeed, any time-bounded communications will fail unless the capacity and coverage required are there. No retries - it works, or it doesn't. And it may be desirable to light up areas where users might be only briefly - stairwells, for example. These can be very tough from an RF perspective.

This implies that some form of site survey may be important in the case of VoFi. I've often noted that coverage near the edges of a given structure can be a bit sparse, as there's no point in illuminating the parking lot, and, indeed, lots of good reasons not to. But this sparseness might adversely affect voice coverage, and, as any cell phone user knows, an out-of-range condition is cause for bad language.

So, as voice becomes more often than not a driver of enterprise Wi-Fi installations, the site survey may make a comeback. Note, however, that they're still not essential in my book. After all, adding another AP for voice is no more complex than adding another AP for any other application. But a little more labor (just a little) up front at the edges of the intended coverage area can help keep the environment civil and everyone productive.

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