Time Difference of Arrival

     How does TDoA work?

     The best way to describe TDoA is to give a reference of yourself and the way you hear things. The human ear is very remarkable by nature because it is used by the body to turn the head and eyes toward a sound that is heard. The really cool thing of this is that both ears hear the sound and process it over and over as they hear it (if it repeats or sustains). The reason why we are able to turn and look at what caused the noise is TDoA.

     Time difference of arrival is math calculations that take place on frequencies heard by both ears to determine which ear is closer to the frequency, which direction the noise is coming from, and how far away the noise is.

     When both ears hear the noise and the left ear heard it 5 micro seconds before the right ear heard it, then the math begins to direct the eyes to the left because TDoA determined that the noise came in to the left ear quicker than it did the right.

     The TDoA calculations in 802.11 wireless location services operate similarly in the same manner. The signal from the same transmitting device is picked up from multiple access points and/or antennas and the calculations determine which access point the device is closer to as well as the direction the device is from each access point, resulting in calculating the location of a device.

   There are several more cool factors in location services, but hopefully you now have an idea of what TDoA is and how it works.