TD 92685EN
28 June 2012 / Ver. A
Troubleshooting Guide
Ascom i62 VoWiFi Handset
30
4. Factors Affecting RF
4.2 Troubleshooting Methodology
There are many troubleshooting models that can be used by a support engineer.
Many methods are based on a layered communication model with the root in the OSI or
TCP/IP stack model and the models can be addressed as top-down or bottom-up
approaches. Troubl
eshooting models also includes steps to take to try to define and isolate
the problem area.
This guide does not describe troubles
hooting theories in details, rather it will describe a
suggested method that has successfully been used by the Ascom support team.
If the problem is in the LAN and WLAN infrastructure the s
upport engineer has to learn the
troubleshooting procedure that different vendors suggest in their operational guides. There
is however usually a general approach that applies to most situations.
A very common method is a cycle mod
el as illustrated below:
• Problem Reporting: Define the nature of the problems that users experience and the
circumstances in which the problems arise. Problem types usually involve interruptions in
the audio stream, disconnections, distortions such as echo and clicking noises, and
delays. The user experiences that small discrete parts of the conversation are missing.
• Get the Picture: Try and elicit add
i
tional information from the user to try and picture the
context and circumstances in which the problem occurs. For example, was the user
stationary or roaming or in the proximity of other non 802.11 devices generating RF
signals?
• Ascertain what is Working: In a complex installation like a VoW
i
Fi system it is important
to rule out the devices that are functional at an early stage of the troubleshooting
process. Why a handset is not functioning when making a call depends on the correct
function of several other devices.
• Form a Hypothesis: Make a list of possible causes. The fault is maybe on a device not
primary a part o
f
the solution, like a nonfunctional DHCP-server.
• Prioritize where to start. Eliminate causes that are quick to check first and do the mo
re
time-consuming later. Also eliminate causes that make less impact for the users first.
Remember that whatever action you take may cause an interruption in the services.
Make one change at a time and if problem is not solved unroll your new settings.
Document what changes were done.
• Test and check: Make sure the appropriate to
ols a
re available for testing a proposed
solution. If modifications to the LAN or WLAN are needed, liaise closely with those
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