CCX Radio Management
You can configure two parameters that affect client location calculations:
Radio measurement requests
These parameters are supported in Cisco Client Extensions (CCX) v2 and later releases. They are designed to enhance location accuracy and timeliness for participating CCX clients.
For the location features to operate properly, the access points must be configured for Local, Monitor, or FlexConnect mode. Location features will not work on FlexConnect APs that have lost their controller connection and entered Standalone mode.
This section contains the following subsections:
Radio Measurement Requests
When you enable the radio measurement requests feature, lightweight access points issue broadcast radio measurement request messages to clients running CCXv2 or later releases. The access points transmit these messages for every SSID over each enabled radio interface at a configured interval. In the process of performing 802.11 radio measurements, CCX clients send 802.11 broadcast probe requests on all the channels specified in the measurement request. Cisco location appliances use the uplink measurements based on these requests received at the access points to quickly and accurately calculate the client location. You do not need to specify on which channels the clients are to measure. The controller, access point, and client automatically determine which channels to use.
The radio measurement requests feature enables the controller to also obtain information on the radio environment from the client’s perspective (rather than from just that of the access point). In this case, the access points issue unicast radio measurement requests to a particular CCXv4 or v5 client. The client then sends various measurement reports back to the access point and on to the controller. These reports include information about the radio environment and data used to interpret the location of the clients. To prevent the access points and controller from being overwhelmed by radio measurement requests and reports, only two clients per access point and up to 20 clients per controller are supported. You can view the status of radio measurement requests for a particular access point or client as well as radio measurement reports for a particular client from the controller CLI.
The controller software improves the ability of the location appliance to accurately interpret the location of a device through a CCXv4 feature called location-based services. The controller issues a path-loss request to a particular CCXv4 or v5 client. If the client chooses to respond, it sends a path-loss measurement report to the controller. These reports contain the channel and transmit power of the client.
Non-CCX and CCXv1 clients ignore the CCX measurement requests and do not participate in the radio measurement activity.
For CCX clients that need to be tracked more closely (for example, when a client calibration is performed), the Cisco WLC can be configured to command the access point to send unicast measurement requests to these clients at a configured interval and whenever a CCX client roams to a new access point. These unicast requests can be sent out more often to these specific CCX clients than the broadcast measurement requests, which are sent to all clients. When location calibration is configured for non-CCX and CCXv1 clients, the clients are forced to disassociate at a specified interval to generate location measurements.