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Method for reducing radio ranging errors due to clock frequency offsets

Method for reducing radio ranging errors due to clock frequency offsets description/claims

The present invention relates generally to radio communication systems, and more particularly to determining distances between transceivers using two-way ranging, which is known as radio ranging.

As shown in FIG. 1, a conventional communication frame 100 for a wireless network: includes as fields: a preamble 110, a start of frame delimiter (SFD) 120, a physical layer header (PHR) 130, and a physical layer sevice data unit (PSDU) 140.

The PSDU typically includes a payload, see IEEE 802.15.4a-D7 standard, November 2006, incorporated by reference. The preamble 110 can be used for acquisition and ranging. The SFD 120 is used for frame synchronization. The detection of the SFD indicates the beginning of the PHR 130 and the PSDU 140. The frame 100 has a time duration of T1 160, and a time duration of the PHR and PSDU is T2 150.

FIG. 2 shows a conventional ranging method. To estimate a distance between a first transceiver A 210 and a second transceiver B 220 in a wireless communications network, the first transceiver A 210 transmits 201 a request frame to the second transceiver B 220. FIG. 2 also shows a time axis 240 for the transceiver A and a time axis 250 for the transceiver B 220. The transceiver A 210 records a time t1 that the request frame was transmitted according to a clock of the transceiver A 210. Upon receiving the request frame, the transceiver B 220 transmits 202 a reply frame to the transceiver A 210. The transceiver A 210 measures the time of arrival (TOA) t2 of the reply frame according to its clock.

A delay at the transceiver B 220 between receiving the request frame and transmitting the reply frame is TtaB 250. The transceiver B 220 transmits 205 the delay 250 to the transceiver A 210 in a timestamp report. An estimate of the distance D between the transceiver A 210 and the transceiver B 220 is the time for the round trip TroundA 270 minus the delay at the transceiver B 220 divided by two and multiplied by the speed of light.

D = (

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Previous Patent Application:
Radar device and method for adjusting among radar sites
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Polarimetric selectivity method for suppressing cross-track clutter in sounding radars
Industry Class:
Communications: directive radio wave systems and devices (e.g., radar, radio navigation)

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