Business Communication and the Technology context

To be able to determine the location of a mobile device in the environment illustrated in Figure 1, the device that performs the location calculation (typically a location server) must know the location of all measurement devices (in this example, the access points). When the mobile device transmits a packet, that packet may be detected by one or more access points listening on the same RF channel that the packet was transmitted on. When the access point listens to the packet, it measures the signal strength of the packet and forwards that measurement to the location calculation engine. The location server then correlates the various measurements and calculates the location of the transmitter using triangulation or other advanced techniques.

If there is a direct line of sight between the transmitter and the measurement point, a simplifying assumption is that the lower the received signal strength of the packet at any particular measurement point, the further away the transmitting device is from that measurement point. Figure 2 shows an example in which two devices are transmitting to the measurement device, one close to the measurement device and a second further away. The measurement device receives the transmissions of both devices, but at different signal strengths. The signal strength of the object that is further away from the measurement device is lower. Based on this information, the distance between the devices and the measurement point can be calculated.