Systems and methods to facilitate location determination by beamforming of a positioning reference signal
Techniques are provided for positioning of a mobile device in a wireless network using directional positioning reference signals (PRS), also referred to as PRS beamforming. In an example method, a plurality of directional PRSs are generated for at least one cell for a base station, such that each of the plurality of directional PRSs comprises at least one signal characteristic and a direction of transmission, either or both of which may be distinct or unique. The plurality of directional PRSs is transmitted within the at least one cell, such that each of the plurality of directional PRSs is transmitted in the direction of transmission. A mobile device may acquire and measure at least one of the directional PRSs which may be identified using the associated signal characteristic. The measurement may be used to assist position methods such as OTDOA and ECID and to mitigate multipath.
1. A method, at a first base station, for supporting positioning of a mobile device, the method comprising:
generating a plurality of directional positioning reference signals (PRSs) for at least one cell for the first base station, wherein each of the plurality of directional PRSs comprises at least one signal characteristic and a direction of transmission, wherein the at least one signal characteristic and the direction of transmission for each of the plurality of directional PRSs is unique for any other directional PRS tyransmitted by the first base station and other nearby base stations;
transmitting each of the plurality of directional PRSs within the at least one cell, wherein each of the plurality of directional PRSs is transmitted in the direction of transmission;
obtaining at least one Round Trip Time (RTT) measurement from a mobile device for at least one of the plurality of directional PRSs transmitted from the first base station; and
obtaining a position of the mobile device based at least in part on the direction of transmission and the RTT measurement.
2. The method of claim 1 , wherein the at least one signal characteristic comprises a frequency, a frequency shift, a code sequence, a muting pattern, a transmission time, or any combination thereof.
3. The method of claim 1 , wherein transmitting the plurality of directional PRSs within the at least one cell comprises:
directing the plurality of directional PRSs through a controllable antenna array configured to beamform each directional PRS in the direction of transmission.
4. The method of claim 3 , wherein the direction of transmission comprises a continuous range of horizontal angles, a continuous range of vertical angles, or a combination thereof.
5. The method of claim 1 , wherein at least one of the plurality of directional PRSs is detectable by the mobile device to facilitate location determination of the mobile device at a location-capable device based on an observed time difference of arrival (OTDOA) position method, an angle of departure (AOD) position method, or an Enhanced Cell ID (ECID) position method, or any combination thereof.
6. The method of claim 5 , wherein the at least one of the plurality of directional PRSs is detectable by the mobile device based on the direction of transmission for the at least one of the plurality of directional PRSs, the at least one signal characteristic for the at least one of the plurality of directional PRSs, or a combination thereof.
7. The method of claim 6 and further comprising:
sending at least one of the direction of transmission for the at least one of the plurality of directional PRSs or the at least one signal characteristic for the at least one of the plurality of directional PRSs to the mobile device.
8. The method of claim 7 , wherein the sending is based on broadcast within the at least one cell.
9. The method of claim 5 , wherein the location determination at the location-capable device includes determining a presence or absence of multipath for the least one of the plurality of directional PRSs based on the direction of transmission for the least one of the plurality of directional PRSs and an approximate location for the mobile device, wherein the determining a location of the mobile device at the location-capable device is based, at least in part, on the determined presence or absence of multipath.
10. The method of claim 9 , wherein the approximate location for the mobile device is based, at least in part, on a serving cell for the mobile device.
11. The method of claim 5 , wherein the location-capable device comprises the mobile device, a Location Management Function (LMF), or a second base station different to the first base station, and wherein the method further comprises:
sending the direction of transmission for the at least one of the plurality of directional PRSs to the location-capable device.
12. The method of claim 1 , wherein the at least one cell is a serving cell for the mobile device.
13. A method, at a location-capable device, for supporting positioning of a mobile device, the method comprising:
obtaining at least one first measurement from the mobile device for a first directional positioning reference signal (PRS) transmitted by a first base station in at least one cell for the first base station, wherein the first directional PRS comprises at least one first signal characteristic and a first direction of transmission, wherein at least one of the at least one first signal characteristic and the first direction of transmission for the first directional PRS is unique for any other directional PRS transmitted by the first base station and other nearby base stations;
obtaining at least one second measurement from the mobile device for a second directional PRS transmitted by a second base station in at least one cell for the second base station, wherein the second directional PRS comprises at least one second signal characteristic and a second direction of transmission, and wherein the at least one second signal characteristic and the second direction of transmission for the second directional PRS are, respectively, different from the at least one first signal characteristic and the first direction of transmission for the first directional PRS; and
determining a location of the mobile device based, at least in part, on the at least one first measurement, the at least one second measurement, the first direction of transmission for the first directional PRS and the second direction of transmission for the second directional PRS.
14. The method of claim 13 , wherein the at least one first signal characteristic comprises a carrier frequency, a frequency shift, a code sequence, a muting pattern, a bandwidth, a transmission time, or any combination thereof.
15. The method of claim 13 , wherein the first directional PRS is transmitted from the first base station through a controllable antenna array configured to beamform the first directional PRS in the first direction of transmission.
16. The method of claim 15 , wherein the first direction of transmission comprises a continuous range of horizontal angles, a continuous range of vertical angles, or a combination thereof.
17. The method of claim 13 , wherein the location-capable device comprises the mobile device, and wherein the method further comprises:
receiving the at least one first signal characteristic and the first direction of transmission from the first base station or from a Location Management Function (LMF).
18. The method of claim 17 , wherein the first direction of transmission is received from the first base station by receiving a broadcast signal from the first base station.
19. The method of claim 13 , wherein the location-capable device comprises the first base station, or a Location Management Function (LMF), and wherein the method further comprises:
receiving the at least one first measurement from the mobile device.
20. The method of claim 19 , further comprising:
sending the at least one first signal characteristic to the mobile device.
21. The method of claim 13 , wherein the at least one first measurement for the first directional PRS comprises a Time Of Arrival (TOA), a Reference Signal Time Difference (RSTD), a Received Signal Strength Indication (RSSI), a Reference Signal Received Power (RSRP), a Reference Signal Received Quality (RSRQ), an Angle of Arrival (AOA), a signal propagation time, a detection of the at least one first signal characteristic, or any combination thereof.
22. The method of claim 21 , wherein determining the location of the mobile device is based on an observed time difference of arrival (OTDOA) position method, an angle of departure (AOD) position method, or an Enhanced Cell ID (ECID) position method, or any combination thereof.
23. The method of claim 22 , and further comprising:
determining a presence or absence of multipath for the first directional PRS based on the first direction of transmission and an approximate location for the mobile device, wherein determining the location of the mobile device is based, at least in part, on the determined presence or absence of multipath.
24. The method of claim 23 , wherein the approximate location for the mobile device is based, at least in part, on a serving cell for the mobile device.
25. The method of claim 13 , wherein the at least one cell for the first base station is a serving cell for the mobile device.
26. A method, at a mobile device, for supporting positioning of the mobile device, the method comprising:
receiving, at the mobile device, a first directional positioning reference signal (PRS) transmitted by a first base station within at least one cell for the first base station, wherein the first directional PRS comprises at least one first signal characteristic and a first direction of transmission, wherein at least one of the at least one first signal characterstic and the first direction of transmission for the first directional PRS is unique for any other directional PRS transmitted by the first base station and other nearby base stations;
obtaining at least one first measurement for the first directional PRS based, at least in part, on the at least one first signal characteristic;
receiving, at the mobile device, a second directional PRS transmitted by a second base station within at least one cell for the second base station, wherein the second directional PRS comprises at least one second signal characteristic and a second direction of transmission, and wherein the at least one second signal characteristic and the second direction of transmission for the second directional PRS are, respectively, different from the at least one first signal characteristic and the first direction of transmission for the first directional PRS;
obtaining at least one second measurement for the second directional PRS based, at least in part, on the at least one second signal characteristic; and
facilitating location determination for the mobile device based, at least in part, on the at least one first measurement, the at least one second measurement, the first direction of transmission for the first directional PRS and the second direction of transmission for the second directional PRS.
27. An apparatus for supporting positioning of a mobile device, comprising:
means for receiving a first directional positioning reference signal (PRS) transmitted by a first base station within at least one cell for the first base station, wherein the first directional PRS comprises at least one first signal characteristic and a first direction of transmission, wherein at least one of the at least one first signal characteristic and the first direction of transmission for the first directional PRS is unique for any other directional PRS transmitted by the first base station and other nearby base stations;
means for obtaining at least one first measurement for the first directional PRS based at least in part on the at least one first signal characteristic;
means for receiving a second directional PRS transmitted by a second base station within at least one cell for the second base station, wherein the second directional PRS comprises at least one second signal characteristic and a second direction of transmission, and wherein the at least one second signal characteristic and the second direction of transmission for the second directional PRS are, respectively, different from the at least one first signal characteristic and the first direction of transmission for the first directional PRS;
means for obtaining at least one second measurement for the second directional PRS based, at least in part, on the at least one second signal characteristic; and
means for facilitating location determination for the mobile device based, at least in part, on the at least one first measurement, the at least one second measurement, the first direction of transmission for the first directional PRS and the second direction of transmission for the second directional PRS.