Method and system for collecting locationing information in a wireless local area network
A technique is provided for determining estimated location of a wireless communication device (WCD) in a network. A first AP transmits a first RSSI data request message, including a BSSID to the WCD at a first time over a radio channel. The WCD then transmits a first response message to the first AP, which then transmits a first measured RSSI value to a trilateration engine (TE). At a different, second time, a second AP can switch to the radio channel and transmit a second RSSI data request message that includes the BSSID of first AP to the WCD over the radio channel. In response, the WCD transmits a second response message to the second AP, which then transmits a second measured RSSI value to the TE. A third AP performs a similar message exchange. This technique collects RSSI information from the WCD at the APs without disrupting any of their connections.
1. A method for determining estimated location of a wireless communication device operating in a network comprising a first access point that the wireless communication device is currently associated with, a second access point, and a third access point, the method comprising:
transmitting, from the first access point to the wireless communication device at a first time over a radio channel, a first Received Signal Strength Indicator (RSSI) data request message comprising a basic service set identifier (BSSID) of the first access point; transmitting a first response message from the wireless communication device to the first access point; and transmitting a first measured RSSI value from the first access point to a trilateration engine in response to the first response message;
switching, at the second access point, from a normal radio channel of the second access point to the radio channel, and transmitting a second RSSI data request message from the second access point to the wireless communication device over the radio channel at a second time different than the first time, wherein the second RSSI data request message comprises the BSSID of first access point; transmitting, in response to the second RSSI data request message, a second response message from the wireless communication device to the second access point; and transmitting a second measured RSSI value from the second access point to the trilateration engine in response to the second response message; and
switching, at the third access point, from another normal radio channel of the third access point to the radio channel, and transmitting a third RSSI data request message from the third access point to the wireless communication device over the radio channel, wherein the third RSSI data request message comprises the BSSID of the first access point; transmitting, in response to the third RSSI data request message, a third response message from the wireless communication device to the third access point, and transmitting a third measured RSSI value from the third access point to the trilateration engine in response to the third response message.
2. A method according to claim 1 , wherein each response message comprises a RSSI data response message, and wherein the step of transmitting a first RSSI data response message from the wireless communication device to the first access point, comprises the steps of:
measuring, at the wireless communication device in response to the first RSSI data request message, a first RSSI value for the first RSSI data request message to generate a first measured RSSI value, and
transmitting a first RSSI data response message from the wireless communication device to the first access point, wherein the first RSSI data response message comprises: the first measured RSSI value for the first RSSI data request message; and,
wherein the step of transmitting a second RSSI data response message from the wireless communication device to the second access point, comprises the steps of:
measuring, at the wireless communication device in response to the second RSSI data request message, a second RSSI value for the second RSSI data request message to generate a second measured RSSI value, and
transmitting a second RSSI data response message from the wireless communication device to the second access point, wherein the second RSSI data response message comprises: the second measured RSSI value for the second RSSI data request message; and,
wherein the step of transmitting a third RSSI data response message from the wireless communication device to the third access point, comprises the steps of:
measuring, at the wireless communication device in response to the third RSSI data request message, a third RSSI value for the third RSSI data request message to generate a third measured RSSI value, and
transmitting a third RSSI data response message from the wireless communication device to the third access point, wherein the third RSSI data response message comprises: the third measured RSSI value for the third RSSI data request message.
3. A method according to claim 2 , further comprising the step of:
converting, at the trilateration engine, the first measured RSSI value into a first estimated distance value that indicates the distance between the wireless communication device and first access point, the second measured RSSI value into a second estimated distance value that indicates the distance between the wireless communication device and second access point, and the third measured RSSI value into a third estimated distance value that indicates the distance between the wireless communication device and the third access point.
4. A method according to claim 3 , wherein the step of converting, comprises:
converting, at the trilateration engine, the first measured RSSI value into a first estimated distance value that indicates the distance between the wireless communication device and first access point based on a function that specifies distance between the wireless communication device and the first access point as a function of RSSI and at least one other variable;
converting, at the trilateration engine, the second measured RSSI value into a second estimated distance value that indicates the distance between the wireless communication device and second access point based on a function that specifies distance between the wireless communication device and the second access point as a function of RSSI and the at least one other variable; and
converting, at the trilateration engine, the third measured RSSI value into a third estimated distance value that indicates the distance between the wireless communication device and the third access point based on a function that specifies distance between the wireless communication device and the third access point as a function of RSSI and the at least one other variable.
5. A method according to claim 3 , wherein the trilateration engine stores coordinates of the first access point, the second access point, and the third access point, and further comprising the step of:
determining, at the trilateration engine, the estimated location of the wireless communication device based on the coordinates of the first access point, the second access point, and the third access point, the first estimated distance value, the second estimated distance value, and the third estimated distance value.
6. A method according to claim 5 , wherein the step of determining, at the trilateration engine, the estimated location of the wireless communication device, comprises:
defining, at the trilateration engine, a first circle having a radius equal to the first estimated distance value and being centered at the coordinates of the first access point, a second circle having a radius equal to the second estimated distance value and being centered at the coordinates of the second access point, and a third circle having a radius equal to the third estimated distance value and being centered at the coordinates of the third access point; and
determining, at the trilateration engine based on trilateration, a point within an intersection between the first circle, the second circle and the third circle, wherein the point corresponds to the estimated location of the wireless communication device with respect to the first, second and third access points.
7. A method according to claim 1 , wherein each response message comprises an acknowledgment (ACK) message, and further comprising the steps of:
receiving the first ACK message at the first access point, and measuring, at the first access point, a first RSSI value for the first ACK message to generate a first measured RSSI value to be sent to the trilateration engine;
receiving the second ACK message at the second access point, and measuring, at the second access point, a second RSSI value for the second ACK message to generate a second measured RSSI value to be sent to the trilateration engine; and
receiving the third ACK message at the third access point, and measuring, at the third access point, a third RSSI value for the third ACK message to generate a third measured RSSI value to be sent to the trilateration engine.
8. A method according to claim 7 , further comprising the step of:
converting, at the trilateration engine, the first measured RSSI value into a first estimated distance value that indicates the distance between the wireless communication device and first access point, the second measured RSSI value into a second estimated distance value that indicates the distance between the wireless communication device and second access point and the third measured RSSI value into a third estimated distance value that indicates the distance between the wireless communication device and the third access point.
9. A method according to claim 8 , wherein the step of converting, comprises:
converting, at the trilateration engine, the first measured RSSI value into a first estimated distance value that indicates the distance between the wireless communication device and first access point based on a function that specifies distance between the wireless communication device and the first access point as a function of RSSI and at least one other variable;
converting, at the trilateration engine, the second measured RSSI value into a second estimated distance value that indicates the distance between the wireless communication device and second access point based on a function that specifies distance between the wireless communication device and the second access point as a function of RSSI and the at least one other variable; and
converting, at the trilateration engine, the third measured RSSI value into a third estimated distance value that indicates the distance between the wireless communication device and the third access point based on a function that specifies distance between the wireless communication device and the third access point as a function of RSSI and the at least one other variable.
10. A method according to claim 8 , wherein the trilateration engine stores coordinates of the first access point, the second access point, and the third access point, and further comprising the step of:
determining, at the trilateration engine, the estimated location of the wireless communication device based on the coordinates of the first access point, the second access point, and the third access point, the first estimated distance value, the second estimated distance value, and the third estimated distance value.
11. A method according to claim 10 , wherein the step of determining, at the trilateration engine, the estimated location of the wireless communication device, comprises:
defining, at the trilateration engine, a first circle having a radius equal to the first estimated distance value and being centered at the coordinates of the first access point, a second circle having a radius equal to the second estimated distance value and being centered at the coordinates of the second access point, and a third circle having a radius equal to the third estimated distance value and being centered at the coordinates of the third access point; and
determining, at the trilateration engine, a point within an intersection between the first circle, the second circle and the third circle, wherein the point corresponds to the estimated location of the wireless communication device with respect to the first, second and third access points.
12. A method according to claim 1 , wherein the trilateration engine is implemented at the wireless switch.
13. A method according to claim 1 , wherein the trilateration engine is implemented at a network server.
14. A wireless network for determining estimated location of a wireless communication device operating in the network, comprising:
a wireless communication device;
a network infrastructure computer comprising a trilateration engine;
a first access point that the wireless communication device is currently associated with, the first access point designed to: transmit to the wireless communication device at a first time over a radio channel, a first Received Signal Strength Indicator (RSSI) data request message comprising a basic service set identifier (BSSID) of the first access point; receive a first response message transmitted from the wireless communication device; determine a first measured RSSI value from the first response message; and transmit a first measured RSSI value to the trilateration engine in response to the first response message;
a second access point designed to switch from a normal radio channel of the second access point to the radio channel and then transmit a second RSSI data request message to the wireless communication device over the radio channel at a second time different than the first time, wherein the second RSSI data request message comprises the BSSID of first access point; receive a second response message from the wireless communication device in response to the second RSSI data request message; determine a second measured RSSI value from the second response message; and transmit a second measured RSSI value to the trilateration engine in response to the second response message;
a third access point designed to switch from another normal radio channel of the third access point to the radio channel and then transmit a third RSSI data request message to the wireless communication device over the radio channel, wherein the third RSSI data request message comprises the BSSID of the first access point; receive a third response message from the wireless communication device in response to the third RSSI data request message, determine a third measured RSSI value from the third response message; and transmit a third measured RSSI value to the trilateration engine in response to the third response message.
15. A wireless network according to claim 14 , wherein each response message comprises a RSSI data response message, wherein the wireless communication device is designed to:
measure, in response to the first RSSI data request message, a first RSSI value for the first RSSI data request message to generate a first measured RSSI value, and transmit a first RSSI data response message to the first access point, wherein the first RSSI data response message comprises: the first measured RSSI value for the first RSSI data request message; and,
measure, in response to the second RSSI data request message, a second RSSI value for the second RSSI data request message to generate a second measured RSSI value, and transmit a second RSSI data response message to the second access point, wherein the second RSSI data response message comprises: the second measured RSSI value for the second RSSI data request message; and,
measure, in response to the third RSSI data request message, a third RSSI value for the third RSSI data request message to generate a third measured RSSI value, and transmit a third RSSI data response message to the third access point, wherein the third RSSI data response message comprises: the third measured RSSI value for the third RSSI data request message.
16. A wireless network according to claim 15 , wherein the trilateration engine is designed to: convert the first measured RSSI value into a first estimated distance value that indicates the distance between the wireless communication device and first access point, convert the second measured RSSI value into a second estimated distance value that indicates the distance between the wireless communication device and second access point, and convert the third measured RSSI value into a third estimated distance value that indicates the distance between the wireless communication device and the third access point.
17. A wireless network according to claim 16 , wherein the trilateration engine stores coordinates of the first access point, the second access point, and the third access point, and determines the estimated location of the wireless communication device based on the coordinates of the first access point, the second access point, and the third access point, the first estimated distance value, the second estimated distance value, and the third estimated distance value.
18. A wireless network according to claim 14 , wherein each response message comprises an acknowledgment (ACK) messages, and wherein the first access point, upon receiving the first ACK message, measures a first RSSI value for the first ACK message to generate a first measured RSSI value and sends the first measured RSSI value to the trilateration engine; wherein the second access point, upon receiving the second ACK message, measures a second RSSI value for the second ACK message to generate a second measured RSSI value and sends the second measured RSSI value to the trilateration engine; and wherein the third access point, upon receiving the third ACK message, measures a third RSSI value for the third ACK message to generate a third measured RSSI value and sends the third measured RSSI value to the trilateration engine.
19. A wireless network according to claim 18 , wherein the trilateration engine is designed to: convert the first measured RSSI value into a first estimated distance value that indicates the distance between the wireless communication device and the first access point based on a function that specifies distance between the wireless communication device and first access point as a function of RSSI and at least one other variable; convert the second measured RSSI value into a second estimated distance value that indicates the distance between the wireless communication device and the second access point based on a function that specifies distance between the wireless communication device and second access point as a function of RSSI and the at least one other variable; and convert the third measured RSSI value into a third estimated distance value that indicates the distance between the wireless communication device and the third access point based on a function that specifies distance between the wireless communication device and the third access point as a function of RSSI and the at least one other variable.
20. A wireless network according to claim 19 , wherein the trilateration engine is designed to determine the estimated location of the wireless communication device by defining a first circle having a radius equal to the first estimated distance value and being centered at the coordinates of the first access point, a second circle having a radius equal to the second estimated distance value and being centered at the coordinates of the second access point, and a third circle having a radius equal to the third estimated distance value and being centered at the coordinates of the third access point; and determining a point within an intersection between the first circle, the second circle and the third circle, wherein the point corresponds to the estimated location of the wireless communication device with respect to the first, second and third access points.