Passive positioning utilizing round trip time information

• US 9,445,227 B2
• Filed: 05/02/2014
• Issued: 09/13/2016
• Est. Priority Date: 08/30/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Aldana, Carlos Horacio
• Primary Examiner(s): SHIVERS, ASHLEY L
• Application Number:
  US14/268,978
• Publication Number:
  US 20150063138A1
• Time in Patent Office: 865 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308
• CPC Class Codes: H04L 67/52 specially adapted for the location of the user terminal
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Techniques for passive positioning of a client station are disclosed. In an example a passive positioning scheme may include detecting an incoming message from an access point, determining a Round Trip Time (RTT) value associated with the access point, generating an acknowledgment message, calculating a time of departure for the acknowledgment message based on the RTT value, and sending the acknowledgment message at the time of departure.

Claims

1. A method for exchanging positioning messages between access points, including:

detecting, with a transceiver, an incoming message from an access point;

determining a Round Trip Time (RTT) value associated with the access point;

generating an acknowledgment message;

calculating a time of departure for the acknowledgment message based, at least in part, on the RTT value; and

sending, with the transceiver, the acknowledgment message at the time of departure.

2. The method of claim 1 further comprising computing a First Arrival Correction (FAC) for the incoming message.

3. The method of claim 2 wherein the time of departure for the acknowledgment message is based at least in part on the FAC.

4. The method of claim 1 further comprising determining a Short Inter-Frame Space (SIFS) value;

and wherein calculating the time of departure is based on the RTT value and the SIFS value.

5. The method of claim 4 wherein calculating the time of departure for the acknowledgment message is performed according to:

t3=t2+SIFS−

RTT/2+L_M

wherein,

t3 is the time of departure;

t2 is a time the in coming message is detected;

SIFS is the Short Inter-Frame Space value associated with the access point;

RTT/2 is a time difference between a time instance when the incoming message was sent and a time instance when the incoming message is detected; and

L_M is a length of the incoming message.

6. The method of claim 1 further comprising determining a message length of the incoming message.

7. The method of claim 1 wherein the incoming message is a QoSNull message.

8. A method of positioning on a client station utilizing inter-access point messaging, comprising:

detecting, at a client station, a broadcast message from a first access point indicating a message exchange with a second access point;

detecting a first message, wherein the first message is sent from the first access point to the second access point;

detecting a second message, wherein the second message is sent from the second access point to the first access point;

determining location information associated with the first access point and the second access point;

determining a Short Inter-Frame Space (SIFS) value;

determining a message length value for the first message;

determining time difference of arrival (TDOA) information based, at least in part, on the detecting of the first message and the second message; and

calculating a position estimate based on the location information associated with the first access point and the second access point, the TDOA information, the SIFS value, and the message length value.

9. The method of claim 8 wherein the first message is a fine timing message.

10. The method of claim 8 wherein the first message is a QoSNull message.

11. The method of claim 8 wherein the broadcast message includes the location information associated with the first access point and the second access point.

12. The method of claim 8 wherein the broadcast message includes Round Trip Time (RTT) information associated with the first access point and the second access point.

13. The method of claim 8 wherein the broadcast message includes the SIFS value.

14. A system to exchange messages for use in passive positioning of a mobile unit, comprising:

a memory unit;

a transceiver;

at least one processor coupled to the memory unit and the transceiver, and configured to;

detect, with the transceiver, an incoming message from an access point;

determine a Round Trip Time (RTT) value associated with the access point;

generate an acknowledgment message;

calculate a time of departure for the acknowledgment message based on the RTT value; and

send, with the transceiver, the acknowledgment message at the time of departure.

15. The system of claim 14 wherein the at least one processor is further configured to compute a First Arrival Correction (FAC) for the incoming message.

16. The system of claim 14 wherein the at least one processor is further configured to calculate the time of departure for the acknowledgment message based at least in part on the FAC.

17. The system of claim 14 wherein the at least one processor is further configured to determine a Short Inter-Frame Space (SIFS) value and calculate the time of departure based on the RTT value and the SIFS value.

18. The system of claim 17 wherein the at least one processor is further configured to calculate the time of departure for the acknowledgment message according to:

t3=t2+SIFS−

RTT/2+L_M

wherein,

t3 is the time of departure;

t2 is a time the incoming message is detected;

SIFS is the Short Inter-Frame Space value associated with the access point;

RTT/2 is a time difference between a time instance when the incoming message was sent and a time instance when the incoming message is detected; and

L_M is a length of the incoming message.

19. The system of claim 14 wherein the at least one processor is further configured to determine a message length of the incoming message.

20. The system of claim 14 wherein the at least one processor is further configured to detect a QoSNull message as the incoming message from the access point.

21. A client station comprising:

a processor;

a positioning unit coupled to the processor and configured to;

detect a broadcast message from a first access point indicating a message exchange with a second access point;

detect a first message, wherein the first message is sent from the first access point to the second access point;

detect a second message, wherein the second message is sent from the second access point to the first access point;

determine location information associated with the first access point and the second access point;

determine a Short Inter-Frame Space (SIFS) value;

determine a message length value for the first message;

determine time difference of arrival (TDOA) information based, at least in part, the detecting of the first message and the second message; and

calculate a position estimate based on the location information associated with the first access point and the second access point, the TDOA information, the SIFS value, and the message length value.

22. The client station of claim 21 wherein the positioning unit is further configured to detect a fine timing message as the first message.

23. The client station of claim 21 wherein the positioning unit is further configured to detect a QoSNull message as the first message.

24. The client station of claim 21 wherein the positioning unit is further configured to detect the location information associated with the first access point and the second access point in the broadcast message.

25. The client station of claim 21 wherein the positioning unit is further configured to detect Round Trip Time (RTT) information associated with the first access point and the second access point in the broadcast message.

26. The client station of claim 21 wherein the positioning unit is further configured

to detect the SIFS value in the broadcast message.