The Importance Of Pre- And Post-Site Surveys; Wlan Dynamics; Troubleshooting Implications And Wlan Design - ASCOM Myco 3 Troubleshooting Manual

WLAN Overview
3.3

The Importance of Pre- and Post-Site Surveys

Modern site survey tools are valuable for pinpointing potential RF propagation problems, especially for
large sites.
Modern site survey tools can do a lot more than just create the traditional heat maps that show the RF
coverage areas from all access points. They can display co-channel interference areas, Signal-to-noise ratio
(SNR levels), rogue access points and more.
Furthermore, most tools also include a pre-site survey WLAN CAD planning tool which a designer can use
to do a simulation of RF coverage by using building drawings for a site. This computer based plan must be
verified on place, once the APs have been installed and configured, by doing a live site survey at the site.
This pre-site survey is an aid to help the designer to plan for the placements of the APs in a new installation.
The designer should make sure that:
• The information gathered about the site is accurate and complete regarding the layout of the site.
• The materials use in the construction of the building and their effects on RF propagation are fully
appreciated.
• The types of antennas to be used and deployed are provisioned for.
• The power levels to use are fully understood.
Otherwise, the result of the survey will not accurately represent the anticipated RF propagation at the site.
Performance problems will immediately manifest themselves once the WLAN is commissioned.
If a pre-site survey was performed in the traditional way, it should be followed up with a post-site survey
after a network is deployed. This can be done by an installer requesting the site survey report and using the
report to check that the installation is optimized for voice and that AP configurations are consistent and
compliant with the vendors recommendations.
If the support engineer is subsequently required to visit a site to troubleshoot problems, he or she should
initially verify that the content of the site survey still is accurate when it comes to AP placements, traffic load,
and channel plans, etcetera. Special attention should be paid to areas where the layout of the building or
concentration of VoWiFi clients may cause problems. The site survey features built into the handset
described later in this guide are very useful in verifying the accuracy of the coverage predicted in the site
survey and can, in some situations, quickly identify holes in the RF coverage.
3.4

WLAN Dynamics

Consideration must also be made that a WLAN is not a one-time installation. It changes constantly as
people move around. The physical characteristics of the site may also change over time as furniture is
moved, office partitions are redesigned and walls are build or removed. All of these factors can affect the
propagation of RF signals.
3.5

Troubleshooting Implications and WLAN Design

It is beyond the scope of this guide to provide information about setting up a new WLAN to accommodate
voice traffic or upgrading a legacy WLAN to do the same, except to emphasize the importance of those
issues described in previous sections. In general, the role of the support engineer should be one of
troubleshooting a system that once appeared to adequately meet the requirements of the enterprise
(otherwise it wouldn't have been signed off) but is now experiencing problems because of physical site
changes, increasing personnel numbers, new applications and other factors that were never envisaged.
Documentation that was completed during the setting up and deployments of the new site can therefore be
a valuable reference in troubleshooting subsequent problems:
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TROUBLESHOOTING GUIDE
TD 93297EN / 19 December 2019 / Ver. B
Ascom Myco 3