Installation guide

46
Wi-Fi Location-Based Services—Design and Deployment Considerations
OL-11612-01
Installation and Configuration
RSSI Cutoff
In addition to enforcing the aforementioned relative and absolute time constraints against received RSSI
reports, the location appliance also applies a parameter known as the RSSI cutoff. Subject to the time
constraints described in RSSI Discard Times, page 45, the location appliance retains the four highest
signal strength reports plus any signal strength reports that meet or exceed the value specified for RSSI
cutoff. The default value for RSSI cutoff is -75 dBm.
The application of RSSI cutoff is illustrated in the following examples (assume the default RSSI cutoff
value):
• Four RSSI reports of -68dBm, -70dBm, -72dBm, and -80dBm—All four reports are retained
because they are the four highest reports.
• Five RSSI reports of -66dBm, -68dBm, -70dBm, -72dBm, and -74dBm—All five reports are
retained because they all meet or exceed the RSSI cutoff.
• Five RSSI reports of -66dBm, -68dBm, -70dBm, -72dBm, and -80dBm—The first four reports are
retained, the fifth report of -80dBm is discarded because it does not meet the RSSI cutoff of -75 dBm
and there are four other signal reports that meet or exceed the RSSI cutoff.
Configuring Location Server Notification Parameters
The configuration of Location Server > Administration > Notification Parameters is discussed in Cisco
Wireless Location Appliance Configuration Guide: Configuring Notification Parameters at the following
URL:
http://www.cisco.com/en/US/products/ps6386/products_configuration_guide_chapter09186a00806b5d
5b.html#wp1053921.
Further clarification regarding some of these parameters is provided in the following sections.
Queue Limit
The Queue Limit parameter specifies the size of the output notification queue of the location server. This
value normally defaults to 500. The location server drops any outbound notifications above this limit if
the output notification queue size is exceeded. Therefore, if you notice that some outbound notifications
are being dropped (via the Notifications Dropped field), you may want to increase the queue limit size.
Retry Limit
The retry limit specifies the number of times an event notification is generated during each refresh cycle.
This parameter can be used to generate more than one copy of an event notification, providing an
additional level of message redundancy to counter any message loss experienced en route to WCS. Keep
in mind that copies of transmitted event notifications are not retained by the location appliance; that is,
each copy of an event notification is “fired and forgotten” by the location appliance. The default is to
send one event notification copy each refresh cycle.
Refresh Time
Refresh time specifies the time interval the location server waits before restarting the notification event
refresh cycle. If the condition that caused the original notification event is still present when the event
refresh cycle is restarted, the location server once again sends the number of notification event messages
specified by the retry limit (see Retry Limit, page 46). This continues until the condition that caused the
event to be sent originally is cleared.