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CCNP Enterprise Core (350-401) Cisco Wireless

Locating Wireless Network Devices

Device location can be important to a business or enterprise network. A large store may be interested in tracking protentional customers as they walk around the store, or a museum as they walk around exhibits to present relevant content.

A client can be located to which access point they are associated too, but it can get more granular with the use of received signal strength.

A clients distance can be calculated using the received signal strength between the access point and the client.

In case of a single access point through, with an omnidirectional antenna, the client could be anywhere with-in a certain distance of a circle from the antenna of the access point.

By using three or more access points, the calculated signal strength can be combined to more accurately determine where the clients device may be located.

This information can be combined with other technologies to provide a real time location service.

Cisco access points and their wireless controllers can integrated with other Cisco technologies such as DNA Centre with location servers such as Cisco Mobility Services Engine, MSE or Cisco Connection Mobile Experiences, CMX, to gather and display location information in real time.

Real time location is not something that was intended to be part of wireless network infrastructure.

The access points interface directly with the client devices and handle normal data forwarding, but the wireless LAN controllers can forward information such as client probing, joining and leaving, their RSS values along to the DNA centre platform for location calculation.

Calculations can be easily done if a device is in free space open air, but with walls and furniture in between an access point and a client device it can be make accurate pin-pointing of a device location more complicated.

Areas can be calibrated by an administrator walking through an area taking measurements with a device to get a real world view of a signals strength in a particular area.

A client device can be discovered and their location calculated by several different access points at the same time.

When a client sends out a 802.11 Probe Request to discover any access points that may be nearby, it will be sent on every channel and band that the client device can support. Multiple access points will pick up on this request as it is sent out by the client, which can be measured and a user device accurately tracked.

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