Precision software defined DSSS radio frequency ranging

This work presents a software-defined wireless RF round-trip time-of-flight ranging system. Range measurements are performed using half-duplex direct sequence spread spectrum (DSSS) communications operating in the 915 MHz ISM band. Baseband clock offsets are directly tracked during each measurement, obviating a need for precise time synchronization as a prerequisite for ranging. Ranging performance of better than 7 cm in 1 standard deviation at over 100 meters separation distance has been measured using a prototype radio implementation with +15 dBm RF transmit power, 13-chip PN code, and 512 PN code copies in the ranging preamble.