A Wi-Fi coverage is an essential element to ensure the proper functioning of equipment. This requires an optimized positioning of the access points in relation to the different environment (wall, interferences, …). To achieve this, we will rely on different studies: Plan survey, AP on a stick survey and active and passive survey. These different surveys have their own advantages and disadvantages, but above all they have different objectives and are generally complementary. We will therefore list and present them in the rest of this article:
Plan survey
A plan survey is a study that allows, with the help of a software that simulates the propagation of radio waves, to position the Wi-Fi terminals in the right places, taking into account the constraints of the site. These constraints, such as walls, exclusion zones or on the contrary higher densities, must be indicated by the engineer in charge of the study. The accuracy of this study depends directly on the quality of the values indicated, which is why this methodology is often used in addition to another audit that will serve to validate the accuracy of the values. Once the various constraints have been entered, this audit methodology offers the possibility to quickly simulate several scenarios and installations.
AP on a stick survey
An AP on a stick survey is an on-site survey, carried out with the help of an access point that will be used during the installation, as well as a battery and a pole that will allow the access point to be temporarily installed at the various recommended locations and to be easily moved. The purpose of this study can be to measure the attenuation of the walls, to validate that the signal propagation simulated by the software is consistent. Using this methodology brings precision to an audit on plan by allowing the use of more precise values, because measured directly on site.
Active vs. passive survey
Once the solution is installed, there are two types of audits, active and passive. These surveys can be performed to validate a Wi-Fi coverage or to identify possible interferences or disturbances. The active study is based on exchanges between the access point and the measurement tool and therefore requires to be connected. This type of audit is therefore relatively limited, because the analysis is only done on the access point to which we are connected and not on all the access points. This type of audit is therefore rarely performed alone, but rather as a complement to a passive study.
Unlike active audits, passive audits do not require any authentication and simply listen to all 802.11 frames and allow you to see all the surrounding channels and networks (depending on the capabilities of your measurement tool). This type of audit allows you to observe, among other things, possible co-channel interference.
It is also recommended in parallel to these surveys to perform a spectral analysis to identify any interference not related to Wi-Fi. The radio frequency environments on the frequency bands related to Wi-Fi is constantly evolving, and many terminals are added. It is therefore essential that the audit process is carried out regularly to anticipate problems.
The realization of these audits allows deploying and validate a good Wi-Fi coverage, however the realization of functional tests is necessary. Indeed, the reality of the measurement tools is not always that of the different terminals even if some tools allow applying compensations. The functional validation also allows validating that the whole communication chain is good and that all the equipments support the protocols and encryption proposed by the Wi-Fi terminals.