Recently I conducted some comparative research on how Wi-Fi vendors price their wireless LAN systems, and it was quite an eye-opener. There are notable variations among vendors, for example, as to what they include in their basic systems and what they charge extra for.

Certainly, it makes sense to have some separately priced, optional features, so only users who need them pay for them. Depending on how much a la carte shopping the vendor requires and the depth of your needs, though, extensive comparison-shopping could become an exhausting nickel-and-dime exercise that makes cross-vendor cost comparisons less than straightforward.

Consider the following:

* In controller-based architectures, vendors generally charge per-AP license fees for basic controller usage. Some, but not all, add another round of per-AP fees for add-on network management software. You might need these extra management features if you want to manage more than one controller from a single console or if you need site survey, troubleshooting, historical data reporting and other advanced features.

* Some vendors promote special features for, say, video, voice, location, add-on security and other types of application-specific support. Note, though, that these features often require separately priced software modules or appliances.

* Do you want mesh capabilities? If you're looking at indoor 802.11n, for example, the situation varies. Depending on vendor: 1) mesh might not be available yet; 2) you might get the capability bundled in for free; 3) you might be charged tens of thousands of dollars for it.

* A given vendor might supply single-radio 802.11n APs only while others might allow both radios in a dual-radio AP to support 802.11n. The total throughput potential per AP thus differs and should be taken into account both when comparing AP capital prices and determining how many of them you'll need if you wish to maintain a minimum capacity.

* The cost of building a redundant architecture depends in part on whether you have to buy licenses for standby equipment or not, another inter-vendor inconsistency. Perhaps most appealing are the virtual cluster controller setups from at least two vendors, Motorola and Trapeze. You can install a multi-controller "farm" at the back end, yet pay just one set of per-AP licensing fees regardless of whether the APs associate to different controllers at different times because of failures or for load-balancing purposes.

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.