An RF site survey should be accomplished in the WLAN design phase and this should be accomplished by certified wireless professionals. The RF site survey consists of five steps:
- Define the customer’s requirements
- Identify coverage areas and user density
- Determine the preliminary locations and requirements of the access points (including necessary antenna types and wired connections)
- Accomplish the actual survey and identify elements that might interfere with the WLAN signal and components
- Document the process (including access point locations, data, and signal rates)
From a design standpoint you might also be in a situation of having to configure and plan an outdoor wireless mesh configuration. This includes several components:
- The wireless control system
- Wireless LAN controllers
- External access point bridge (rooftop access points)
- Outdoor mesh access points
An important design for outdoor wireless mesh scenarios refers to the existence of a 2 to 3 ms latency value per hop, so the recommendation is to have fewer than four hops to ensure a good level of performance. Another recommendation is to have no more than 20 mesh access point nodes per external access point bridge for best performance.
The most important wireless campus design considerations include the following:
- The number of APs: Sufficient access points should be included to ensure RF coverage for all the wireless clients in all enterprise areas. Cisco recommends 20 data devices per access point.
- The placement of APs: Access points should be placed in the central locations of different enterprise areas to ensure proper user connectivity.
- Power options for APs: Access points can be powered by traditional methods or by using PoE (Power over Ethernet) capabilities.
- The number of WLCs: The number of wireless LAN controllers depends on the redundancy model chosen and (based on the client requirements) the number of access points. The recommended redundancy model is deterministic redundancy.
- The placement of WLCs: Wireless LAN controllers should be placed in secured wiring closets, server rooms, or data centers. WLCs can be placed in a central location or they can be distributed throughout the campus Distribution Layer. Inter-controller roaming should be minimized.