In order to ensure proper Wi-Fi coverage and performance, RF site surveys should be performed before and after WLAN installations and modifications. Though you can walk around and do simple signal checks and throughput tests using free software on your laptop, using Wi-Fi surveying software provides much better testing and reporting.
You load your floor plans (or maps for outdoors) into Wi-Fi surveying software and after walking around taking measurements you'll have visualizations on many Wi-Fi aspects--basically weather maps of your Wi-Fi environment. Signal, noise, signal-to-noise ratio (SNR), and data rates are some of the most basic measurements you'll see. The tools offer additional visualizations, like channel overlaps, capacity, VoWLAN or RLTS (real-time location system) details, and other Wi-Fi health attributes.
Wi-Fi surveying software also allows you to create completely simulated Wi-Fi environments within the software. You place virtual access points on your floor plan or map, defining antenna and power specs, and then specify wall types and other RF attenuators so the signal propagation can be better predicted.