Q: Is there a tool that we can use in the designing of a WLAN implementation that helps simulate the environment where the access points (either 802.11a, b or g) will be located, and the behaviour of these access points given the map of the area (including obstacles). As a result of the tool, we could estimate more accurately if a specific theoretical design is accurate. Any help?
- Rami P.
The wizards gaze into their crystal ball and respond:
Bob Friday, Airespace
RF prediction tools estimate the coverage of your access points through a computer simulation of your RF environment and the transmit power of the access point antennas. Most systems use a two-part process to provide you with a detailed map for placement of access points with performance estimations. First, you modify a graphic of your floor plans with editing software to create a mapping that accurately describes the RF characteristics of your building's walls. Then you can start your prediction by virtually placing access points on the map, and generating the graphical coverage plot of the expected average signal strength intensity experienced by users in various building locations.
Comparatively, a site survey measures actual signal strength intensity of physically placed access points across your coverage area to verify assumptions made in the planning phase. There are two site survey approaches, which both require you to first arrange your network of access points based on the planning findings. One method will automatically conduct the survey across all access points. However, there is no quality substitute for walking through your network area with a client (laptop, PDA) that has survey software. After data is collected, good systems will provide you tools to ensure that the number, placement and channel configuration of your access points provide your required network quality.
Jason Luther, AirWave
There are many commercial planning tools you can use to simulate the RF environment. Some are highly sophisticated (and complicated) tools that take into account building materials, physical obstacles, etc. Others are less precise (but much easier to use) and provide a rougher estimation of coverage areas and the RF environment. Keep in mind that any of these tools provides a "best guess" snapshot for a particular point in time. The RF environment and usage patterns are constantly changing.
While it is great to have a good RF planning tool, it's much more important for you to be able to continuously monitor the RF airspace and adjust your network setup dynamically in response to changing conditions. The key to this is to ensure that your access points themselves have the ability to gather and report real-time data about the RF environment (most enterprise-grade access points can) and that you have a centralised WLAN management system that analyzes this information and lets you control all RF settings dynamically.
Joel Vincent, Meru Networks
Traditional WLAN vendors will often employ site survey and channel planning tools that do exactly what you're looking for. These tools, packages with enterprise access points, are more often than not re-branded from popular planning tool companies such as Ekahau and its competitors. The limitation of doing a complex site plan like the one you describe is the fact that the RF environment is not static, so as soon as you plan/predict the RF propagation, it will change if anything moves or is added to the environment (such as a filing cabinet or a desk). This would require a re-plan and possibly a new site survey.
Another route is to use a system that can automatically do channel planning and prediction, and coordinate the access points in the system to maximise coverage without the need for prediction software. WLAN architectures that operate as a full system and eliminate co-channel interference (and the need for channel and RF planning) maintain a continuous interference map, which dynamically adjusts for changing environments. Because RF is complex and dynamic, this is the future for building a reliable WLAN without the management becoming prohibitively expensive (people-hours for maintenance).