Reconnect; Configured Channels And Scanning Intervals; Power Save Mode; Roaming - ASCOM Myco 3 Troubleshooting Manual

TROUBLESHOOTING GUIDE
Ascom Myco 3
4.3.3

Reconnect

When disconnected from the Wi-Fi networking, a frequent scan period is triggered to regain the connection
if the screen is active. During the 160 second period scanning for Wi-Fi is done every ten seconds. When
the handset is in sleep mode (the screen is locked), the Wi-Fi scanning is performed approximately with a
300-seconds interval.
4.3.4

Configured Channels and Scanning Intervals

When a handset is started from power off mode the procedure to find an AP to associate with depends on
the parameter and protocol settings in the handset.
One of the default protocols that are used by the handset is 802.11d. This protocol transports regulatory
domain information based on country information stored in the AP which is sent out in the beacon. 802.11d
is not allowed in the USA.
The correct channel set up in a WLAN is quite important. The channels set up to be used by the handset on
any of the 2.4 GHz or 5GHz has impact on the performance of the handset.
To be able to detect APs when in passive scanning mode the handset must listen to each channel slightly
longer than the beacon interval, to be sure not to miss any beacon. The handset then has to switch the
radio channel and starts to listen again on the new channel.
For performance reasons when scanning, the amount of channels should be minimized and only
include the channels that are used in the WLAN.
Active scanning of the 5 GHz UNII-2 and UNII-2e, the DFS-channels are not permitted in the 802.11 standard,
so those channels will only be scanned in passive mode. If in passive scanning was determined to permit to
send traffic, an active scanning is made.
The handset can use the DFS channels, but the voice quality may be distorted. For additional
information, see the section
4.4

Power Save Mode

Maintaining connection to the Access Point at all times can run the battery down significantly. Ascom Myco
3 is using legacy power save mode until there are packets to transmit or receive. If no packet transmission
has happened during the next 500 ms, the handset goes back to the power save mode.
4.5

Roaming

One of the most important design criteria for good functionality in a voice system is to deploy sufficient APs
to create adequate RF coverage throughout a site. In addition, the coverage areas provided by the
individual APs must be deployed in such a way as to allow a user to roam throughout the site without any
deterioration in the quality of an ongoing call. The user must also remain connected to the network at all
times even when the handset is in idle mode. Failure to adequately support roaming may result in audible
clicks and other disturbances in a voice call.
Roaming can be described as disconnecting from the current AP as the user moves away from it and the
signal attenuates. The user then connects to a new AP that offers an increasingly stronger signal as the
handset is carried towards it. As a user moves away from an AP of decreasing received signal strength and
towards one of increasing signal strength, it is predictable enough to be able to apply a roaming algorithm
based on the measurement of received signal strength at fixed time intervals, for example, every 4 seconds.
TD 93297EN / 19 December 2019 / Ver. B
4.6 DFS Channel Probing, page
The Handset as a WLAN Wireless Client
12.
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