For new installations, extensions or large-scale systems, the access points’ location is not only crucial for performance, but also ensures the greatest possible coverage of a WLAN network. To determine the best location, we carry out detailed measurements on site, hence why they’re called «site surveys». Over the course of this interview, Armin Walt, Systems Engineer at onway (schweiz) ag, explains what site surveys are all about.
Armin, not everyone who uses a WLAN network thinks specifically about the fact that the coverage at their property might not be perfect everywhere. Many people think that it is sufficient to simply place one or more access points to communicate wirelessly. Where or when does it make sense to do a site survey?
Armin Walt: Doing a site survey makes sense if you want to use your WLAN network professionally and are not sure where access points are best placed and whether there are structural obstacles that could impair reception quality. We strongly recommend taking measurements in production halls, high-bay warehouses, factory halls and large premises such as galleries, exhibition centres and museums.
A site survey should also be carried out urgently in older buildings, as the building materials used in the past attenuate radio signals very differently and can therefore severely impair the performance of the WLAN. In office buildings built more recently, only a reference measurement is necessary to determine the wall attenuation. A single measurement is sufficient for objects of identical construction. For example, hospital rooms are usually all the same – here it is enough to only measure one ward or floor.
However, most importantly, we always carry out an on-site inspection BEFORE estimating the cost of a larger project.
What is particularly important when you plan a site survey for a client?
For us, it is particularly important to know a customer’s exact WLAN network requirements. For pure data coverage, we only need to focus on signal strength. For voice-over-WLAN coverage, i.e. if telephone calls are to be made via WLAN, the roaming paths are also important otherwise calls can break up or interruptions can occur. What’s more, too many devices cannot communicate via an access point at the same time, so the load must be optimally distributed among different transmitters.
In addition, we need as much information as possible about the conditions on site before completing the site survey. For example: Is there already WLAN on site? What is the coverage like currently? Do staircases, lifts, outdoor areas, or wet rooms need to be included? Is there any hardware already in use that needs to be planned for as the access points are already fixed? Are there any problems anywhere?
Before effectively planning the site survey, we also need the building plans as a CAD file or high-resolution PDF/image, as well as all other information regarding access and potential risks on site.
Are site surveys always based on existing plans?
No, definitely not. As mentioned previously, we visit the building in advance with a person who is familiar with it. This allows us to build up a realistic picture and include any disruptive elements – which the client may not have noticed yet – directly into our planning. We also discuss the installation options directly on site. We pay special attention to particular areas such as high-bay warehouses, small parts warehouses and heavily frequented areas. Following the on-site visit, we can assess where it is possible to build and install at all and where, on the other hand, it would be too costly.
Is a site survey time-consuming?
This always depends on the scope and area of the building to be surveyed. When completing a site survey for a rather small building, we spend most of our time assessing the demand for WLAN coverage, the entire planning and the preparatory work.
The client also needs to be on hand when assessing requirements as they may need to further clarify certain plans, rooms or areas. There can often be a discrepancy between need and what is feasible with reasonable effort. This should be clarified before the site survey to ensure measurements are not carried out more than once.
We provide our customers with a checklist prior to the on-site visit so that there are no surprises during the on-site inspection and to avoid that the survey cannot be carried out due to missing information.
What are some of the points that need to be considered?
Often, clients’ security concepts prescribe certain checks or employees have to be informed in advance. Sometimes special protective equipment is needed to enter sensitive areas (such as intensive care units or operating theatres). Or in halls, we often have to take measurements at heights of over 4.5 metres. For this purpose, a lifting platform is required on site, for example.
How does a site survey actually work?
We prepare all the required materials the day before the site survey at the very latest. In addition to a laptop, access points and antennas, this also includes laser range finders, screwdrivers and cable ties – this means we’re equipped for every eventuality. (laughs)
In general, the measurements are always carried out by two people. Using a Sidekick – a special device with highly sensitive antennas – and Ekahau software, we record the signal strength as we walk. In doing so, the Sidekick continuously scans all WLAN channels and records the coverage along the route.
A multi-page site survey report is provided once the WLAN measurements are complete. The customer receives a measurement report and a documentation in which we would recommend where to install the access points. For larger site surveys or in case of ambiguities, we also include photo documentation of the installation locations for the electrician.
Thank you, Armin, for this informative interview.