BROADCASTING SHORT INTERFRAME SPACE INFORMATION FOR LOCATION PURPOSES

• US 20140269400A1
• Filed: 03/14/2013
• Published: 09/18/2014
• Est. Priority Date: 03/14/2013
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Zhang, Xiaoxin, ALDANA, Carlos Horacio, Sridhara, Vinay, Fischer, Sven, Chao, Hui, Homchaudhuri, Sandip, Cho, James Simon
• Application Number:
  US13/826,116
• Publication Number:
  US 20140269400A1
• Time in Patent Office: Days
• US Class Current: 370/253
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/0236 Assistance data, e.g. base station almanac
• CPC Class Codes: H04W 48/12 using downlink control channel
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method and apparatus for broadcasting short interframe space information to aid in determining a round trip time are provided. The round trip time is used as an aid in locating nodes within a WiFi or WLAN network. The method begins with capturing a time of transmission of a frame by a transmitting station. The receiving station then captures the time of arrival of the frame just sent by the transmitting station. The receiving station replies with a received frame message and the time of departure is captured. The transmitting station then captures the time of arrival of the received frame message. The captured arrival and departure times of the frame and the received frame message allow the round trip time to be computed. The RTT may then be included as part of a network message.

Claims

1. A method for estimating a position of a wireless node in a communication system, comprising:

computing a round trip time (RTT) of a frame using a turn-around calibration factor (TCF);

comparing the computed RTT with RTTs of other nodes in the communication system;

estimating the position of the node based on the comparison of the RTTs.

2. The method of claim 1, further comprising;

recording a departure time for a transmit event; and

refraining from sending replicas of transmit packets from multiple transmit/receive chains to ensure that the departure time is correctly recorded in a timestamp.

3. The method of claim 1, further comprising:

computing an arrival time of a packet, wherein the packet is transmitted as a replica from multiple antennas of a target node.

4. The method of claim 1, where the TCF is a short interframe space (SIFS).

5. The method of claim 1, where the SIFS includes uncertainty in time of arrival.

6. The method of claim 1, wherein the TCF is a time difference between a last symbol of a transmit packet received at an antenna of a target node and a beginning of a preamble of a response packet.

7. The method of claim 6, where the response packet is an acknowledgement message.

8. The method of claim 7, wherein the received frame message is returned at a predetermined interval.

9. The method of claim 1, where the TCF includes an uncertainty in a time of arrival of a frame.

10. The method of claim 5, wherein the SIFS information is provided in a broadcast message header.

11. The method of claim 10, wherein a field bit indicates if the SIFS range is enabled or not enabled.

12. The method of claim 5, wherein minimum and maximum variance of the SIFS value is transmitted.

13. The method of claim 5, wherein the SIFS value is provided in at least one of the following formats:

SIFS minimum, SIFS maximum, mean and standard deviation of the SIFS.

14. A method for estimating a round trip time (RTT), comprising:

capturing a time of transmission of a frame by a transmitting station;

capturing a time of arrival of the frame sent by the transmitting station by a receiving station;

capturing a time of departure of a received frame message by the transmitting station;

capturing the time of arrival of the received frame message by the transmitting station; and

computing a RTT based on the captured time of arrival and the captured time of departure of both the frame and the received frame message and a turn-around calibration factor (TCF).

15. The method of claim 14 wherein the RTT includes information on compensation in the turn-around calibration factor.

16. The method of claim 15 wherein if the SIFS value is less than a predetermined threshold, the node is deemed RTT capable.

17. The method of claim 16, wherein a standard deviation is included in the turn-around calibration factor, and transmitted in a beacon message.

18. An apparatus for estimating a position of a wireless node in a communication system, comprising:

a processor for computing a round trip time (RTT) of a frame using a turn-around calibration factor (TCF);

a processor for comparing the computed RTT with RTTs of other nodes in the communication system; and

a processor for estimating the position of the node based on the comparison of the RTTs.

19. An apparatus for estimating a round trip time, comprising:

a processor for capturing a time of transmission of a frame;

a processor for capturing a time of arrival of a frame;

a receiver for receiving a time of arrival of a frame;

a processor for computing a round trip time using a turn-around calibration factor (TCF); and

a transmitter for transmitting a computed round trip time as part of a network message.

20. An apparatus for estimating a position of a wireless node in a communication system, comprising:

means for computing a round trip time (RTT) of a frame using a turn-around calibration factor (TCF);

means for comparing the computed RTT with RTTs of other nodes in the communication system; and

means for estimating the position of the node based on the comparison of the RTTs.

21. An apparatus for estimating a position of a wireless node in a communication system, comprising:

means for capturing a time of transmission of a frame by a transmitting station;

means for capturing a time of arrival of the frame sent by the transmitting station by a receiving station;

means for capturing a time of departure of a received frame message by the transmitting station;

means for capturing the time of arrival of the received frame message by the transmitting station; and

means for computing a RTT based on the captured time of arrival and the captured time of departure of both the frame and the received frame message and a turn-around calibration factor (TCF).

22. The apparatus of claim 21, further comprising:

means for recording a departure time for a transmit event; and

refraining from sending replicas of transmit packets from multiple transmit/receive chains to ensure that the departure time is correctly recorded in a timestamp.

23. The apparatus of claim 22, further comprising means for computing an arrival time of a packet, wherein the packet is transmitted as a replica from multiple antennas of a target node.

24. The apparatus of claim 22, wherein the means for computing RTT uses a short interframe space (SIFS) as the TCF.

25. A non-transitory computer-readable medium containing instructions, which when executed by a processor, cause the processor to perform the steps of:

computing a round trip time (RTT) of a frame using a turn-around calibration factor (TCF);

comparing the computed RTT with RTTs of other nodes in the communication system; and

estimating the position of the node based on the comparison of the RTTs.

26. A non-transitory computer-readable medium containing instructions, which when executed by a processor, cause the processor to perform the steps of:

capturing a time of transmission of a frame by a transmitting station;

capturing a time of arrival of the frame sent by the transmitting station by a receiving station;

capturing a time of departure of a received frame message by the transmitting station;

capturing the time of arrival of the received frame message by the transmitting station; and

computing a RTT based on the captured time of arrival and the captured time of departure of both the frame and the received frame message and a turn-around calibration factor (TCF).