User manual

Chapter 2 - Managing a Single Device/Cell Air Interface General Page
AlvariCRAFT Device Manager 36 User Manual
2.3.2 Cell Distance Parameters (BreezeACCESS VL)
The higher the distance of an SU from the AU that is serving it, the higher the time
it takes for messages sent by one of them to reach the other. To ensure
appropriate services to all SUs regardless of their distance from the AU, while
maintaining a high overall performance level, two parameters are adapted to the
distances of SUs from the serving AU:
1 The time that a unit waits for a response message before retransmission (ACK
timeout) should take into account the round trip propagation delay between
the AU and the SU (The one-way propagation delay at 5 GHz is 3.3
Lost Beacon Watchdog
Threshold
Applicable only for AU and BU. When it is unable to send beacon
frames for a predetermined period of time, such as in the case of
interferences, the AU/BU resets itself. The Lost Beacon Watchdog
Threshold parameter defines the number of consecutive lost beacons
after which the unit will reset itself.
The configurable range for this parameter is 100 - 1000. When the
checkbox is unchecked, the parameter is set to 0, disabling the
feature (internal refresh will never be performed). To activate the
feature, check the checkbox.
Wireless Trap Threshold
(%)
Applicable only for AU and BU. The Wireless Trap Threshold
parameter defines the threshold for the wireless quality trap,
indicating that the quality of the wireless link has dropped below (On
trap) or has increased above (Off trap) the specified threshold.
The Wireless Trap Threshold is in percentage of retransmissions, and
the range is from 1 to 100 (%).
Scanning Mode Applicable only for SU and RB. The Scanning Mode parameter
defines whether the device will use Passive or Active scanning when
searching for an AU/BU.
In passive scanning, the device "listens" to the wireless medium for
approximately two seconds at each frequency, searching for
beacons. The disassociation period, which is the time from the
moment the link was lost until the device decides that it should start
searching for another AU/BU, is approximately seven seconds.
In some situations when there is a high probability that SU/RB may
need to roam among different AUs/BUs, the use of active scanning
enables to significantly reduce the link establishment time. This is
achieved by using shorter dwell periods, transmitting a Probe
Request at each frequency. This reduces the time spent at each
frequency as well as the disassociation period.
When DFS is supported by the Country Code being used by the unit,
Scanning Mode is forced to Passive.