Site surveys can take the following three basic forms and we would recommend that at least two of these are carried out for any large deployment:
- Predictive survey
This is performed using software tools such as the Ekahau Site survey and Planning Tool or the free ZyXEL Wireless Optimizer, in which detailed plans of the deployment site are constructed and then different WLAN configurations simulated to predict the optimal number and location of APs of your chosen brand and model. The value of such a survey will depend to a large degree on the quality of the information input. Greater precision, not only for the various room dimensions but also for the thickness and construction of the walls and ceilings that separate them, will increase the overall predictive accuracy.
- Pre-deployment survey
This is a physical survey performed on-site using one or more test APs, together with hardware or pc-based software tools, allowing you to test various AP placements and then, by walking through the building with the laptop or tablet, record and map the resulting signal strength at surrounding points. The resulting map correlating signal strength with a detailed plan of the site, is often referred to as a ‘heat map’. Another useful tool at this stage is a spectrum analyzer, which can help to identify potential sources of interference and measure their likely impact on the network. These tools (also available from vendors such as Ekahau) typically consist of a small USB device working in concert with pc-based software.
- Post-deployment / Validation survey
This is a survey performed after full installation of the WLAN, where actual coverage and signal strength is verified at all necessary locations within the building, typically using the same kind of pc-based software tools as in a pre-deployment survey. This type of survey can also be useful when planning an upgrade to an existing WLAN.
In cases where detailed building plans are available, and especially if already familiar with the construction and intended usage of the site, then a predictive survey may be sufficient to broadly estimate the size and scope of a new deployment.
However, in most cases, the greater predictive accuracy achieved through an on-site pre-deployment survey will more than repay the additional investment in time.