Wireless Surveys and Heat Maps

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Factors to consider when designing a wireless network:

• range
• interference
• signal strength
• number of devices in close proximity
  • device density
• how much devices move
• special traffic requirements
  • voice or video conferencing

A wireless survey is documentation about a location for the purposes of building an ideal wireless infrastructure; it often contains optimum locations for wireless antenna and access point placement to provide the required coverage for clients and identify sources of interference.

• aka site survey
• area served by a single AP is referred to as a basic service area (BSA)
• area where stations can roam between access points to stay connected to the same ESSID is an extended service area (ESA)
• wireless site survey ensures that these areas are properly sized
• used to measure signal strength and channel usage throughout the area to cover

A heat map In a Wi-Fi site survey, is a diagram showing signal strength and channel utilization at different locations.

Conduct a Survey

1. examining the blueprints or floor plans of the premises
   • understand the layout and to identify features that might produce radio frequency interference (RFI)
   • can be backed up by a visual inspection
     • can be backed up by a visual inspection
   • need obtain plans that show the locations of available ports
     • Each AP mounting point needs a network port and power jack
2. create a new plan on which you will mark the basic service areas and associated APs and booster antennae
   • place APs:
     • close enough together to avoid dead zones
       • areas where connectivity is difficult or data transfer rates are below an acceptable tolerance level
     • far enough apart that
       • one AP does not interfere with another
       • that one AP is not overutilized and a nearby one underutilized
3. place and test each AP
   • use a laptop with a wireless adapter and a wireless survey tool to
     • record signal strength and supported data rate at various points in the intended BSA
   • heat map shows areas with
     • strong signal in greens and yellows
     • oranges and reds where signal strength drops off
   • Neighboring APs should be configured with non-overlapping channels
     • avoid interference
   • may need to adjust AP transmit power to size its BSA appropriately

Info

• network design may need different power levels for different bands
  • e.g.,
    • lower power on the 2.4 GHz band to reduce its range and make it more likely that clients will connect on the 5 GHz band
    • Alternatively, may configure band steering, or use different ESSIDs for 2.4 GHz and 5 GHz networks