WLAN Overview
TROUBLESHOOTING GUIDE
Ascom Myco 3
3 WLAN Overview
A WLAN enables various devices, or WLAN clients, to communicate across Radio Frequency (RF) channels
through APs. APs provide RF coverage throughout the site covered by the WLAN and this enables users,
and their devices, to move around the site without being disconnected from the network. Each AP is
identified by a hard-coded MAC address.
Initially, WLANs were designed to allow users to send and receive data from devices such as laptop
computers but increasingly WLANs are being required to support different and more demanding types of
traffic such as voice and multimedia. A VoWiFi system is illustrated in Figure 1. VoWiFi Overview, page 4.
Figure 1. VoWiFi Overview
LAN
Handsets
Location Server
Controller
optional equipment
required equipment
AP
AP
IP-PBX
3.1 The Problem of Legacy WLANs
Legacy WLAN systems were designed for transmitting data packets; support for voice and other multimedia
was never envisaged when these systems were designed, deployed and commissioned. So many
traditional cell-based WLAN topologies proved unsuitable for handling channelization issues, AP-to-AP
handoffs, and the unpredictably of system bandwidth that are introduced when VoWiFi is implemented.
Voice is very susceptible to such issues being addressed satisfactorily. A WLAN that does not support
VoWiFi but is being upgraded to do therefore requires very careful planning, design, provisioning and
hardware deployment to get the level of performance to adequately support voice. These problems are
multiplied when different traffic types such as voice, video and data all contend for the same airspace.
Adding voice to a WLAN may require radical changes of the APs placement and the amount of APs needed.
If this is not considered feasible to undertake in a current installation VoWiFi may never perform as
expected.
It follows that if a legacy WLAN is to support VoWiFi then an assessment of how suitable the WLAN is to
support VoWiFi must be made. The number and deployment of additional devices involved in the WiFi
solution must be carefully assessed. For example, the assessment should consider the adequacy of the
current deployment in meeting cell boundary requirements because adequate cell overlap is a fundamental
requirement for a voice system. The assessment should conclude with a readiness report documenting the
suitability of the WLAN for both the wired and the wireless part of the network. The required parameter
settings of the devices supporting the WiFi system should also be documented.
The following table lists some of the topics that should be included in an assessment document:
4
TD 93297EN / 19 December 2019 / Ver. B
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