Waveform design for Wi-Fi time-of-flight estimation

Patent metadata

Field	Value
Publication number	US-10034133-B2
Application number	US-201615218434-A
Country	US
Kind code	B2
Filing date	Jul 25, 2016
Priority date	Dec 23, 2015
Publication date	Jul 24, 2018
Grant date	Jul 24, 2018

Abstract

Some embodiments relate to a waveform design for time-of-flight estimation in a wireless communication system. The waveform may include a number N of signal tones, wherein the number N of signal tones is greater than a number M of signal tones that the receiving wireless device is configured to decode. Upon receipt of the waveform, the receiving wireless device may store a timestamp which indicates a time of receipt of the waveform. The receiving wireless device may decode M of the N signal tones. For example, the receiving wireless device may decode the middle M signal tones of the N signal tones. One or more of the transmitting or receiving wireless devices may then estimate a distance between them based at least in part on the timestamp.

First claim

We claim:

1. A wireless device, comprising:
a radio; and
a processing element operably coupled to the radio;
wherein the radio and the processing element are configured to:
receive, from a transmitting wireless device, a waveform for use in performing a time-of-flight estimation, wherein the waveform comprises a number N of signal tones generated in N corresponding frequency bins, wherein the number N of signal tones is greater than a number M of signal tones that the wireless device is configured to decode;
store a timestamp which indicates a time of receipt of the waveform;
decode M of the signal tones; and
transmitting the timestamp to the transmitting wireless device for use in estimating a distance between the wireless device and the transmitting wireless device.

2. The wireless device of claim 1 ,
wherein the wireless device conforms to a wireless standard that specifies a first type of encoding;
wherein the waveform is encoded using a second different type of encoding.

3. The wireless device of claim 1 ,
wherein the waveform is encoded using quaternary phase shift keying (QPSK) modulation.

4. The wireless device of claim 1 ,
wherein the waveform comprises two consecutive groups of N signal tones, wherein the number N of signal tones in each group is greater than a number M of signal tones that the wireless device is configured to decode;
wherein said decoding comprises decoding M signal tones in each of the groups of N signal tones.

5. The wireless device of claim 4 ,
wherein the two consecutive groups of N signal tones comprise a first group of N signal tones encoded using phase shift keying on an in-phase axis and a second group of N signal tones encoded using phase shift keying on a quadrature axis.

6. The wireless device of claim 1 ,
wherein the waveform comprises a cyclic prefix sent immediately prior to the N signal tones;
wherein the cyclic prefix is comprised of a portion of the N signal tones;
wherein the timestamp is created at a time interval between the cyclic prefix and a start of the N signal tones.

7. The wireless device of claim 6 ,
wherein the waveform comprises a cyclic postfix sent immediately after the N signal tones;
wherein the cyclic postfix is comprised of a portion of the N signal tones.

8. The wireless device of claim 1 ,
wherein bits in the waveform are randomized.

9. A wireless device, comprising:
a radio; and
a processing element operably coupled to radio;
wherein the radio and the processing element are configured to:
transmitting, to a receiving wireless device, a waveform for use in performing a time-of-flight estimation, wherein the waveform comprises a number N of signal tones generated in N corresponding frequency bins, wherein the number N of signal tones is greater than a number M of signal tones that a receiving wireless device is configured to decode;
generating a first time stamp indicating a time at which the waveform was transmitted;
receiving, from the receiving wireless device, a second time stamp indicating a time at which the waveform was received by the receiving wireless device;
estimating, based at least partly on the first time stamp and the second time stamp, a distance between the wireless device and the receiving wireless device.

10. The wireless device of claim 9 ,
wherein the wireless device conforms to a wireless standard that specifies a first type of encoding;
wherein the radio and the processing element are configured to encode the waveform using a second different type of encoding.

11. The wireless device of claim 9 ,
wherein the radio and the processing element are configured to encode the waveform using quaternary phase shift keying (QPSK) modulation.

12. The wireless device of claim 9 ,
wherein the waveform comprises two consecutive groups of N signal tones, wherein the number N of signal tones in each group is greater than a number M of signal tones that the receiving wireless device is configured to decode.

13. The wireless device of claim 12 ,
wherein the radio and the processing element are configured to encode a first group of N signal tones using phase shift keying on an in-phase axis and to encode a second group of N signal tones using phase shift keying on a quadrature axis.

14. The wireless device of claim 9 ,
wherein the waveform comprises a cyclic prefix sent immediately prior to the N signal tones;
wherein the cyclic prefix is comprised of a portion of the N signal tones.

15. The wireless device of claim 9 ,
wherein the waveform comprises a cyclic postfix sent immediately after the N signal tones;
wherein the cyclic postfix is comprised of a portion of the N signal tones.

16. The wireless device of claim 9 ,
wherein bits in the waveform are randomized.

17. A non-transitory computer accessible memory medium that is comprised in a transmitting wireless device, wherein the memory medium stores:
a waveform for use in a wireless transmission to a receiving wireless device to perform time-of-flight estimation, wherein the waveform comprises a cyclic prefix and a number N of signal tones generated in N corresponding frequency bins, wherein the number N of signal tones is greater than a number M of signal tones that a receiving wireless device is configured to decode, wherein the cyclic prefix is comprised of a portion of the N signal tones;
wherein the waveform is useable by at least one of the transmitting wireless device or the receiving wireless device in performing time-of-flight estimation.

18. The non-transitory computer accessible memory medium of claim 17 ,
wherein the receiving wireless device conforms to a wireless standard that specifies a first type of encoding;
wherein the waveform is encoded using a second different type of encoding.

19. The non-transitory computer accessible memory medium of claim 17 ,
wherein the waveform comprises two consecutive groups of N signal tones, wherein the number N of signal tones in each group is greater than a number M of signal tones that the receiving wireless device is configured to decode.

20. The non-transitory computer accessible memory medium of claim 17 ,
wherein the memory medium further stores program instructions executable to perform time of flight estimation using a timestamp generated upon receipt of the waveform.

Assignees

• Apple Inc

Inventors

• Mujtaba Syed Aon
• Wang Xiaowen

Classifications

• G01S17/26

  wherein the transmitted pulses use a frequency-modulated or phase-modulated carrier wave, e.g. for pulse compression of received signals · CPC title

• H04L27/0008

  arrangements for allowing a transmitter or receiver to use more than one type of modulation (negotiating modulation type for two-way transmission paths H04L5/1453) · CPC title

• H04W4/023 Primary

  using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds · CPC title

• H04L27/34

  Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems · CPC title

• H04L27/2607

  Cyclic extensions · CPC title