Site surveys

Wireless Head provide the following site surveys:

Passive site survey
This survey discovers Wi-Fi currently visible across a site, including Wi-Fi from neighbours and rogue Wi-Fi equipment within the site. As a result this kind of survey allows us to detect some current and potential problems. If you plan to have Wi-Fi installed we recommend a passive site survey with test Wi-Fi equipment deployed at a number of locations across the site. This use of a passive site survey is called a pre-deployment survey. It allows us to judge more accurately the appropriate Wi-Fi equipment to use and its necessary installation locations to ensure the WLAN meets requirements.
Predictive site survey
Unlike the other surveys listed here a site visit is not essential, although it is very useful. Using a floor plan and some knowledge of the building structure a predictive site survey attempts to predict the findings of a passive site survey with theoretical Wi-Fi equipment in place. Obviously this is not as accurate as a passive site survey with real Wi-Fi equipment in place, and it cannot discover other Wi-Fi from neighbours and rogue Wi-Fi equipment on site. Nonetheless it can be useful where site access is problematic, and to reduce survey costs in predictable environments like sites with only lightweight partition walls, open plan offices, and in open spaces such as venues halls and outside. It is also useful for planning pre-deployment surveys as it can be used to decide where test equipment might be best placed. This is particularly true for buildings with many rooms, and even more so when the walls are very solid.
Active site survey
This survey measures the data transfer performance that is actually achieved by a Wi-Fi system, as opposed to what is theoretically possible. It can be used to check a Wi-Fi system conforms to performance requirements, to track down suspected performance problems, and to proactively detect as yet unrecognised problems. If Wi-Fi data transfer performance is important this is an essential survey.
Wi-Fi traffic analysis
This monitors Wi-Fi traffic in detail to track down the cause of difficult to understand problems, such as intermittent throughput problems with a specific access point. The behaviour of Wi-Fi is due to network equipment and the clients that use it. A client can degrade the behaviour of the access point it connects to for all clients, usually inadvertently. Once the cause has been established steps can be taken to ameliorate the problem. This can be the only decisive way to address difficult to understand problems with Wi-Fi. Rather than look at individual items of traffic, protocol analysis detects patterns that are indicative of events. So protocol analysis is often a good starting point to find elusive causes of problems.
Spectrum analysis
This survey records Wi-Fi and non-Wi-Fi based emissions across the radio spectrum used by Wi-Fi. This survey can highlight if current or planned Wi-Fi is likely to suffer from interference or contention, whatever the source. As two bands of spectrum are available to Wi-Fi this survey is essential to prevent the expensive mistake of using a problematic band. This kind of survey is becoming more common as the spectrum used by Wi-Fi is increasingly crowded with emissions from many kinds of equipment.

Free and low cost versions of some of these site survey services are also available.