The latest Wi-Fi specification is . Like its predecessors 802.11b and 802.11g, 802.11n travels over a 2.4GHz radio signal. The 802.11n spec uses a multiple-antenna system that provides greater range than 802.11g, and it can transfer data at speeds of up to 300 mbps, compared to 802.11g's maximum rate of 54 mbps. And since 802.11n devices are backward-compatible with 802.11b/g devices, there's no reason to look at any APs other than 802.11n devices unless you're bound by a previous purchasing contract.
A involves more than just tossing a few APs around and hoping for the best. To start with, you should consider where to place the APs, what the interior walls are composed of, and how many APs need to be installed. Locating the Wi-Fi APs is a critical aspect of the wireless deployment. One option is to use centrally located APs through the floor to provide "inside out" coverage; another is to go "outside in" by placing the APs in corners and along outside offices, with the APs looking in to the user area. If your building setup doesn't permit placing APs in the user space, you can use high-end outdoor APs to "light up" the building from outside the physical walls; this is particularly useful in multiple-tenant situations. Of course, you can always combine approaches to get the exact coverage you need. I've found that, except in the case of floor plans where the center of the building is filled with elevator shafts or other equipment, an inside-out approach provides the best coverage and is easier to deploy.
It may sound obvious, but make sure that you've planned for a sufficient number of APs. I've seen many Wi-Fi installations fail because the company used too few APs to cover the user space, with some overlap. in the open, a typical AP can cover a radius of approximately 300 feet. Indoors, 50 to 100 feet is the usable maximum.
The composition of your walls plays a big role in how far Wi-Fi travels indoors. Wood construction is best; walls attached to steel studs are bad; and concrete walls with steel rebar are the worst. One or two walls can greatly reduce a Wi-Fi signal. And if the path to an AP traverses a wall at an angle, the signal is likely to degrade even more. A number of tools--from handheld scanners to iPhone and Android applications--are available to help admins check wireless signal strength at various points in a building. Use these tools to achieve optimal AP placement.