Chapter 6 Deploying Wireless Networks for FortiOS 5.0 : Introduction to wireless networking : Deployment considerations : Deployment methodology : Evaluating the coverage area environment
  
Evaluating the coverage area environment
Consider the following factors:
Size of coverage area — Even under ideal conditions, reliable wireless service is unlikely beyond 100 metres outdoors or 30 metres indoors. Indoor range can be further diminished by the presence of large metal objects that absorb or reflect radio frequency energy. If wireless users are located on more than one floor of a building, a minimum of one WAP for each floor will be needed.
Bandwidth required — Wireless interface data rates are between 11 and 150 Mb/s, depending on the 802.11 protocol that is used. This bandwidth is shared amongst all users of the wireless data stream. If wireless clients run network-intensive applications, fewer of them can be served satisfactorily by a single WAP.
Note that on some FortiWiFi units you can define up to four wireless interfaces, increasing the available total bandwidth.
Client wireless capabilities — The 802.11n protocol provides the highest data rates and has channels in the less interference-prone 5GHz band, but it is supported only on the latest consumer devices. The 802.11g protocol is more common but offers lower bandwidth. Some older wireless client equipment supports only 802.11b with a maximum data rate of 11Mb/s. WAP radios support the protocol that you select with backward compatibility to older modes. For example, if you select 802.11n, clients can also connect using 802.11g or 802.11b.
The most important conclusion from these considerations is whether more than one WAP is required.