| 摘要 |
Wireless local area networks (WLANs) provide wireless communication between various wireless devices. Frames are acknowledged (ACKed) after a short and predefined MAC idle time. The MAC idle time varies with 1) the physical distance between wireless devices, caused by the delay of wireless signal propagation, and 2) the time to detect the ACK at the local wireless device, which varies with the signal strength of the incoming ACK. Embodiments present CAESAR (CArriEr Sense-bAsed Ranging), which combines time of flight (TOF) and signal-to-noise ratio (SNR) measurements to calculate the distance between two wireless devices. CAESAR measures the distance by estimating the MAC idle time in a data/ACK communication at a particular clock resolution and the ACK detection time on a per-frame basis. Performance measurements confirm the accuracy of the solution and show the capability to track the distance to WLAN smart phones at pedestrian speeds.
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