Installation guide

D-14 Motorola RF Switch System Reference Guide
D.2.1 Wi-Fi Location Determination
To provide 802.11 locationing, the integrated RTLS engine uses a signal propagation model which is
constantly updated using real time values of RSSI measurements from APs and trilateration to determine
client location. Using this signal propagation model, the integrated RTLS engine can avoid time consuming
calibration.
The RTLS processing consists of several discrete steps:
• Devices transmit probe requests to APs.
• APs forward these probes to the integrated RTLS engine on the RF Switch.
• The integrated RTLS Engine collects the RSSI values from all the APs that are within reach of each client.
• The RTLS engine computes the location of each client using the RSSI values and trilateration.
The integrated RTLS engine uses RSSI information received from clients 802.11 Probe Requests to compute
a client's location. For the RTLS engine to update the clients location in real-time, it needs to constantly
receive Probe Request packets from the clients. However, the transmission of Probe Request packets is
client-dependent and may only occur when a client roams. Consequently, Motorola recommends Wi-Fi
clients run the following client software to ensure the periodic transmission of 802.11 Probe Request
packets:
• Motorola Handhelds - MUSTAT.exe
• Non Motorola Wi-Fi Clients - NetStumbler
D.2.2 Location Presentation
Once the RTLS engine has been enabled, the RF Switch discovers clients and computes each client's location
to provide an estimated X/Y coordinate for the clients.