Determining Distances Between Wireless Devices

Abstract

A method includes transmitting frames from a first device to a second device, where a first frame is transmitted at a first value for a particular transmission parameter, and where a second frame is transmitted at a second value for the particular transmission parameter that is different than the first value. For each of the transmitted frames, a determination is made if a corresponding Acknowledgement (ACK) frame, as defined by IEEE 802.11 standards, is received by the first device from the second device. Based on the IEEE 802.11 ACK frames received by the first device from the second device, a distance estimate is calculated from the first device to the second device.

1 . A non-transitory machine readable medium comprising a set of instructions which, when executed by one or more hardware processors causes a set of operations to be performed comprising:
 transmitting a first plurality of frames from a first device to a second device, wherein a first frame of the first plurality of frames is transmitted at a first value for a particular transmission parameter, and wherein a second frame of the first plurality of frames is transmitted at a second value for the particular transmission parameter that is different than the first value;   for each of the first plurality of frames: determining if a corresponding Acknowledgement (ACK) frame, as defined by IEEE 802.11 standards, is received by the first device from the second device;   based on the IEEE 802.11 ACK frames received by the first device from the second device, calculating a distance estimate from the first device to the second device.   
     
     
         2 . The machine readable medium of  claim 1 , wherein calculating the distance estimate from the first device to the second device based on the IEEE 802.11 ACK frames received by the first device comprises: (a) identifying a particular frame of the first plurality of frames with a lowest transmit power for which a corresponding IEEE 802.11 ACK was received by the first device and (b) calculating the distance estimate based on a particular distance stored in association with the lowest transmit power. 
     
     
         3 . The machine readable medium of  claim 1 , wherein calculating the distance estimate from the first device to the second device based on the IEEE 802.11 ACK frames received by the first device comprises: (a) identifying a particular frame of the first plurality of frames with a highest data transmission rate for which a corresponding IEEE 802.11 ACK was received by the first device and (b) calculating the distance estimate based on a particular distance stored in association with the highest data transmission rate. 
     
     
         4 . The machine readable medium of  claim 1 , wherein at least one IEEE 802.11 ACK frame, used to calculate the distance estimate from the first device to the second device, has a 01 type value and a 1101 subtype value. 
     
     
         5 . The machine readable medium of  claim 1 , wherein at least one of the first plurality of frames is a NULL-DATA frame. 
     
     
         6 . The machine readable medium of  claim 1 , wherein the operations further comprise:
 transmitting a second plurality of frames from a third device to the second device, wherein a first frame of the second plurality of frames is transmitted at a third value for the particular transmission parameter and a second frame of the second plurality of frames is transmitted at a fourth value for the particular transmission parameter different than the third value;   for each of the second plurality of frames: determining if a corresponding Acknowledgement (ACK) frame, as defined by IEEE 802.11 standards, is received by the third device from the second device;   based on the ACK frames, as defined by the IEEE 802.11 standards, that were received by the third device from the second device: calculating a distance estimate from the third device to the second device;   based at least on (a) the distance estimate between the first device and the second device and (b) the distance estimate between the third device and the second device: calculating a location of the second device.   
     
     
         7 . The machine readable medium of  claim 1 , wherein the operations further comprise:
 determining a distance estimate between a third device and the second device;   determining a distance estimate between a fourth device and the second device;   determining a location estimate of the second device based on: (a) the distance estimate between the first device and the second device, (b) the distance estimate between the third device and the second device, and (c) a distance estimate between the fourth device and the second device.   
     
     
         8 . The machine readable medium of  claim 1 , wherein the particular transmission parameter is a transmit power level for transmitting the first plurality of frames from the first device to the second device. 
     
     
         9 . The machine readable medium of  claim 1 , wherein the particular transmission parameter is a data transmission rate for transmitting the first plurality of frames from the first device to the second device. 
     
     
         10 . A system comprising:
 a first device comprising a hardware processor;   the system being configured to perform operations comprising:   transmitting a first plurality of frames from the first device to a second device, wherein a first frame of the first plurality of frames is transmitted at a first value for a particular transmission parameter, and wherein a second frame of the first plurality of frames is transmitted at a second value for the particular transmission parameter that is different than the first value;   for each of the first plurality of frames: determining if a corresponding Acknowledgement (ACK) frame, as defined by IEEE 802.11 standards, is received by the first device from the second device;   based on the IEEE 802.11 ACK frames received by the first device from the second device, calculating a distance estimate from the first device to the second device.   
     
     
         11 . The system of  claim 10 , wherein calculating the distance estimate from the first device to the second device based on the IEEE 802.11 ACK frames received by the first device comprises: (a) identifying a particular frame of the first plurality of frames with a lowest transmit power for which a corresponding IEEE 802.11 ACK was received by the first device and (b) calculating the distance estimate based on a particular distance stored in association with the lowest transmit power. 
     
     
         12 . The system of  claim 10 , wherein calculating the distance estimate from the first device to the second device based on the IEEE 802.11 ACK frames received by the first device comprises: (a) identifying a particular frame of the first plurality of frames with a highest data transmission rate for which a corresponding IEEE 802.11 ACK was received by the first device and (b) calculating the distance estimate based on a particular distance stored in association with the highest data transmission rate. 
     
     
         13 . The system of  claim 10 , wherein at least one IEEE 802.11 ACK frame, used to calculate the distance estimate from the first device to the second device, is an IEEE 802.11 control frame with a 01 type value and a 1101 subtype value. 
     
     
         14 . The system of  claim 10 , wherein at least one of the first plurality of frames is a NULL-DATA frame. 
     
     
         15 . The system of  claim 10 , wherein the system further comprises a third device, and wherein the operations further comprise:
 transmitting a second plurality of frames from the third device to the second device, wherein a first frame of the second plurality of frames is transmitted at a third value for the particular transmission parameter and a second frame of the second plurality of frames is transmitted at a fourth value for the particular transmission parameter different than the third value;   for each of the second plurality of frames: determining if a corresponding Acknowledgement (ACK) frame, as defined by IEEE 802.11 standards, is received by the third device from the second device;   based on the ACK frames, as defined by the IEEE 802.11 standards, that were received by the third device from the second device: calculating a distance estimate from the third device to the second device;   based at least on (a) the distance estimate between the first device and the second device and (b) the distance estimate between the third device and the second device: calculating a location of the second device.   
     
     
         16 . The system of  claim 10 , wherein the system further comprises a third device and a fourth device, and wherein the operations further comprise:
 determining a distance estimate between a third device and the second device;   determining a distance estimate between a fourth device and the second device;   determining a location estimate of the second device based on: (a) the distance estimate between the first device and the second device, (b) the distance estimate between the third device and the second device, and (c) a distance estimate between the fourth device and the second device.   
     
     
         17 . The system of  claim 10 , wherein the particular transmission parameter is a transmit power level for transmitting the first plurality of frames from the first device to the second device. 
     
     
         18 . The system of  claim 10 , wherein the particular transmission parameter is a data transmission rate for transmitting the first plurality of frames from the first device to the second device. 
     
     
         19 . A method comprising:
 transmitting a first plurality of frames from a first device to a second device, wherein a first frame of the first plurality of frames is transmitted at a first value for a particular transmission parameter, and wherein a second frame of the first plurality of frames is transmitted at a second value for the particular transmission parameter that is different than the first value;   for each of the first plurality of frames: determining if a corresponding Acknowledgement (ACK) frame, as defined by IEEE 802.11 standards, is received by the first device from the second device;   based on the IEEE 802.11 ACK frames received by the first device from the second device, calculating a distance estimate from the first device to the second device;   wherein the first device comprises a hardware processor.   
     
     
         20 . The method of  claim 19 , wherein calculating the distance estimate from the first device to the second device based on the IEEE 802.11 ACK frames received by the first device comprises at least one of:
 (a) identifying a first frame of the first plurality of frames with a lowest transmit power for which a corresponding IEEE 802.11 ACK was received by the first device and calculating the distance estimate based on a first distance stored in association with the lowest transmit power; or   (a) identifying a second frame of the first plurality of frames with a highest data transmission rate for which a corresponding IEEE 802.11 ACK was received by the first device and calculating the distance estimate based on a second distance stored in association with the highest data transmission rate.