Monday, November 30, 2009

WCS Client Calibration + RFID Tags

Open caveat with dual band client calibration cscsh88795 – calibrate one band at a time or use two client devices to calibrate both bands simultaneously.  CCXv1 or Non CCX clients will be forced to reassociate/reauthenticate to generate probe requests.  They do not respond to unicast radio measurement requests

When doing calibration – temporarily disable TPC, ensure WLAN calibration client connects to is configured to support Aironet IE.

To use a “test point” in WCS – Advanced Debug must be enabled on the location appliance/MSE

802.11b asset tags that transmit messages using L2 multicasts will not cause the initiation of any 802.11g protection mode under any circumstances.  This includes CCXv1 tags.
    - A probe request from an 802.11b tag that is not associated to an AP does not cause protection mode.  Not until the asset tag associates to the cell in question, or an adjacent cell on the same channel.  APs not on the same channel as the tag or not an adjacent RF, no protection mode is enabled.

Enable Asset tag RF Data timeout – (valid range: 60-7200) (default: 1200)
-    recommended to be set to a minimum of 3x to a maximum of 8x the longest tag transmission interval found in the general tag population.  This should be inclusive of any stationary and “in-motion” transmission intervals.

RFID data timeout should always be greater than the asset tag polling interval on the location appliance/MSE

Recording asset tag location history is disabled by default.
The archival interval between writes of historical data to the database is 720 seconds by default.

Tag activator range = 3 feet

Transmission parameters:
-    message repetitions: change from default value of 1 to 3 to overcome the tags’ transmissions being lost due to lost RSSI readings.  Settings above 5 are not necessary.

LOCP Echo Request: 100 bytes transmitted on TCP destination port 16113
LOCP Echo Response: 100 bytes
LOCP Info. Request: From location appliance to WLC, 106 bytes on TCP destination port 16113
LOCP Info. Response: from WLC to location appliance, if no tags are detected – 113 bytes, one tag detected – 144 bytes, two tags detected – 175 bytes (example tag tx not including telemetry data)

Tag high priority notifications:
When a call button is depressed on an asset tag (CCX compliant) a LOCP Information Notification is transmitted by the WLC to the location appliance/MSE.  The basic size is 130 bytes
This transmission is sent to the location appliance/MSE for each high priority notification sreceived by EACH of the WLC’s registered APs.

Chokepoint triggers in WCS
Range value set on chokepoints is only for a visual aide of the chokepoint range.  The vendor’s management application is what truly adjusts the chokepoint range.

Chokepoint usage – checkbox must be enabled in order for the location appliance/MSE to use chokepoint location techniques to localize tags.

Chokepoint out of range timeout – this is the timer that is used to age the last “in-range” report received from  or received for an asset tag that is being localized using chokepoint location techniques

AeroScout T2 tags
The typical size of the tag multicast frame emitted when in the proximity of a chokepoint trigger = 71 bytes
The routine periodic transmission = 56 bytes
There are an extra 8 bytes of vendor specific information included

CCX allows tags to communicate historical information about the chokepoints they traverse to CUWN.  This can increase the size of the frame by 10 bytes per chokepoint trigger (depending on number of historical entries maintained)

The number of LOCP measurement notification generated by one or more WLCs for a single tag transmits multicast frames indicating it has been triggered by a chokepoint depends on:
-    the number of registered APs within range of the tag that detected the chokepoint event
-    the number of times the tag will transmit a multicast frame on each configured 802.11 channel in response to the chokepoint trigger

The repetition count of the multicast frames sent after an exciter event is managed independent of the repetition count for other tag events.  This is configured on a per-exciter basis

A tag sends one multicast frame from an exciter event – the WLC parses it into two separate LOCP notifications
    LOCP measurement notification – contains chokepoint group information = 160 bytes
LOCP information notification – contains vendor specific information = 138 bytes in length

The fragment number should always start from zero even if the burst length is zero.
For a packet burst, the fragment number should be set to N where N is the packet index within the burst starting from zero.

show RFID summary
show RFID config
config advanced location expiry {calibrating client|client|rogue-APs|tags}
config advanced location RSSI-half-life {calibrating client|client|rogue-APs|tags}

If tag detection is enabled and the asset tag is configured to transmit on the channel the AP is configured for, check to see that the AP is forwarding the multicast packet to the WLC by using this debug:
debug dot11 dot11radio0 trace print mcast
    *as of code version 4.1 – this command must be entered at the AP console, it cannot be entered remotely at the WLC.

verify asset tag telemetry and events:
debug MAC addr [MAC address]
debug dot11 RFID enable
show LOCP status
debug LOCP event enable

v4.2 of CUWN introduces an enhancement that allows for individual limits to be placed on what portion of the location appliances’ aggregate tracked device capacity is allocated to each tracked device category (clients, tags, rogues)

1 comment:

  1. Thank you for the info. It sounds pretty user friendly. I guess I’ll pick one up for fun. thank u