Method, apparatus and system for defining positioning configuration in a wireless network

• US 20110105144A1
• Filed: 08/19/2010
• Published: 05/05/2011
• Est. Priority Date: 11/03/2009
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Kangas, Ari, Siomina, Iana
• Granted Patent: US 8,600,398 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/0236 Assistance data, e.g. base station almanac
• CPC Class Codes: G01S 5/0268 by deriving positions from different combinations of signals or of estimated positions in a single positioning system
• 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 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 72/54 based on quality criteria

Abstract

GPS and A-GPS based positioning methods can be used to determine UE locations to enable location based services to be provided. However, if a UE does not have such receivers or the wireless network is not able to provide assistance, these methods will not be applicable. An alternative is to use OTDOA measurements using positioning reference signals transmitted by cells of the network. By optimizing the set of cells transmitting their positioning reference signals on different positioning occasions and properly configuring the muting patterns, interference can be minimized and the UE location can be readily determined.

Claims

1. A method for defining positioning configuration in the wireless network, wherein some or all cells of the network are capable of wirelessly transmitting positioning reference signals (PRS) during positioning occasions, the PRS being usable to determine a location of a user equipment (UE), each positioning occasion being composed of a predetermined number N_PRS consecutive subframes having a predetermined periodicity of N subframes, N>

N_PRS, such that the N_PRS positioning subframes repeat every N subframes, both N and N_PRS being integers greater than zero, the method comprising;

determining, by a first network node, muting patterns of one or more cells of the wireless network; and

providing assistance information from a second network node to the UE,

wherein the muting pattern of a cell indicates a plurality of positioning occasions in which the cell will transmit its PRS and a plurality of positioning occasions in which the cell will mute its transmission of the PRS,

wherein a number of muted positioning occasions is greater than zero, and

wherein the assistance information includes the muting pattern of at least one cell determined by the first network node.

2. The method of claim 1, wherein for at least one cell, the first and second network nodes are the same node.

3. The method of claim 1,

wherein for at least one cell, the first and second network nodes are different nodes, and

wherein the method further comprises communicating the muting pattern of the cell by the first network node to the second network node.

4. The method of claim 3, wherein the first network node is a base station.

5. The method of claim 3, wherein the second network node is a positioning node.

6. The method of claim 1,

wherein in the step of determining the muting pattern of a cell, one or more positioning parameters of the cell are determined,

wherein the positioning parameters include any one or more of a skip indicator, a transmit positioning occasion indicator, a transmit subframe indicator, and a positioning occasion periodicity indicator,

wherein the skip indicator, when determined, indicates a number of consecutive muted positioning occasions that subsequently follow each transmit positioning occasion such that the transmit positioning occasions for the cell regularly repeats,

wherein the transmit positioning occasion indicator, when determined, indicates which of the positioning occasions are the transmit positioning occasions for the cell,

wherein the transmit subframe indicator, when determined, indicates which subframe within the transmit positioning occasion will be used by the cell to transmit its PRS, and

wherein the positioning occasion periodicity indicator, when determined, indicates the predetermined periodicity N.

7. The method of claim 6,

wherein the positioning parameters for the cell includes at least a step factor k as the skip indicator and a shift Δ

_PRS as the transmit positioning occasion indicator,

wherein k is a non-negative integer,

wherein Δ

_PRS is an integer between 0 and 2^k−

1, and

wherein the transmit positioning occasions of the cell are defined by r2^k+Δ

_PRS, r being a non-negative integer.

8. The method of claim 7, wherein the shift Δ

_PRS is determined based on a physical cell identity (PCI) of the cell, a PRS frequency reuse factor for PRS signals of the network, and the step factor k.

9. The method of claim 8, wherein the shift Δ

_PRS of the cell is determined also based on an antenna index which uniquely identifies a location of an antenna corresponding to the antenna index.

10. The method of claim 7,

wherein the cell is associated with a relay device arranged to relay signals to and from a base station, and

wherein the shift Δ

_PRS for the cell in which the positioning reference signal from the base station is relayed by the relay device is set such that the transmit positioning occasion of the relay device does not overlap with the transmit positioning occasion of at least one cell associated with the base station.

11. The method of claim 7,

wherein the positioning parameters for the cell further includes a transmit subframe index Δ

as the transmit subframe indicator,

wherein Δ

is an integer between 0 and N_PRS, and

wherein the suframes in which the cell transmits its PRS signal are defined by N(r2^k+Δ

_PRS)+Δ

.

12. The method of claim 11,

wherein the positioning parameters for the cell further includes a periodicity factor n as the positioning occasion periodicity indicator,

wherein n is a non-negative integer, and

wherein N and n are related according to N=a2ⁿ, a being a number of subframes in a frame.

13. The method of claim 6,

wherein the assistance information provided to the UE comprises assistance information of one or more cells for which the muting pattern has been determined and whose PRS transmissions are to be measured by the UE, and

wherein the assistance information for each cell comprises any one or more of the skip indicator, the transmit positioning occasion indicator, the transmit subframe indicator, and the positioning occasion periodicity indicator.

14. The method of claim 13, wherein the cells whose PRS transmissions are to be measured by the UE include a serving cell and/or one or more cells neighboring the serving cell.

15. The method of claim 13,

wherein the network is an asynchronous network, and

wherein the assistance information includes the transmit subframe indicator and the positioning occasion periodicity indicator of the cells.

16. The method of claim 13,

wherein the network is a synchronous network,

wherein the transmit positioning occasions coincide for all cells to be measured by the UE, and

wherein the assistance information includes

the transmit subframe indicator and the positioning occasion periodicity indicator of a reference cell, and

the skip indicators and the transmit positioning occasion indicators of all cells.

17. The method of claim 16, wherein the reference cell is a serving cell.

18. The method of claim 1, wherein the step of determining the muting patterns comprises:

grouping a plurality of cells into a plurality of cell sets, each cell set comprising cells with same PRS pattern Ω

(s), s being a PRS pattern ID; and

for each cell set Ω

, performing the steps of;

subdividing the cell set to a plurality of cell groups; and

assigning transmit positioning occasions to each of the cell groups such that transmit positioning occasions of cells in different groups do not overlap in time.

19. The method of claim 18, wherein the step of subdividing the cell set to the plurality of cell groups comprises:

for a plurality of cell pairs i and j in the set, determining a set of interference cost parameters c_ij (c_ijε

Ω

^(s));

determining a set of graph edges give a maximum sum of edge weights, each graph edge describing the isolation between two cells in the set and the edge weights representing interference costs based on the interference cost parameters; and

partitioning the cells into groups so as to separate cells of edges contributing to the maximum sum of edge weights into different cell groups,

wherein the interference cost parameter c_ij between cells i and j are determined based on any combination of PRS transmit power levels of the cells, signal-to-interference ratio of the link between the two cells, and signal-to-interference-plus-noise ratio of the link between the two cells.

20. The method of claim 19, wherein the cost parameter cy is determined by a base station corresponding to cell i or cell j, the method further comprising the base station exchanging the cost parameter information with other base stations.

21. The method of claim 20,

wherein for at least one cell, the step of determining the muting pattern comprises determining the muting pattern of the cell by a base station corresponding to the cell based on the cost parameter information exchanged with other base station, and

wherein the method further comprises:

communicating, by the base station, the muting pattern of the cell to a positioning node; and

communicating, by the positioning node, the muting pattern of the cell to the serving cell.

22. The method of claim 1, wherein each positioning occasion is composed of N_PS consecutive positioning subframes of N_PRS subframes such that N_PRS=bN_PS, b being an integer greater than 1.

23. The method of claim 1,

wherein for at least one cell, the predetermined periodicity of one cell is greater than the predetermined periodicity of at least one other cell, and

wherein a node corresponding to the one cell transmits its PRS at every positioning occasion.

24. The method of claim 23, wherein the node corresponding to the one cell is a beaconing device.

25. A network node for defining positioning configuration in a wireless network, wherein some or all cells of the network are capable of wirelessly transmitting positioning reference signals (PRS) during positioning occasions, the PRS being usable to determine a location of a user equipment (UE), each positioning occasion being composed of a predetermined number N_PRS consecutive subframes having a predetermined periodicity of N subframes, N>

N_PRS, such that the N_PRS positioning subframes repeat every N subframes, both N and N_PRS being integers greater than zero, the network node comprising;

a muting pattern determining unit arranged to determine muting patterns of one or more cells of the wireless network; and

a communication unit arranged to communicate the muting pattern of at least one cell to another network node;

wherein the muting pattern of a cell indicates a plurality of positioning occasions in which the cell will transmit its PRS and a plurality of positioning occasions in which the cell will mute its transmission of the PRS, and

wherein a number of muted positioning occasions is greater than zero.

26. The network node of claim 25,

wherein the network node is a base station,

wherein the muting pattern determining unit determines the muting pattern of at least one cell corresponding to the base station, and

wherein the communication unit sends the muting pattern of the cell to the another network node.

27. The network node of claim 25,

wherein the muting pattern determining unit determines one or more positioning parameters of the cell,

wherein the positioning parameters include any one or more of a skip indicator, a transmit positioning occasion indicator, a transmit subframe indicator, and a positioning occasion periodicity indicator,

wherein the skip indicator, when determined, indicates a number of consecutive muted positioning occasions that subsequently follow each transmit positioning occasion such that the transmit positioning occasions for the cell regularly repeats,

wherein the transmit positioning occasion indicator, when determined, indicates which of the positioning occasions are the transmit positioning occasions for the cell,

wherein the transmit subframe indicator, when determined, indicates which subframe within the transmit positioning occasion will be used to by the cell to transmit its PRS, and

wherein the positioning occasion periodicity indicator, when determined, indicates the predetermined periodicity N.

28. The network node of claim 27,

wherein the positioning parameters for the cell includes at least a step factor k as the skip indicator and a shift Δ

_PRS as the transmit positioning occasion indicator,

wherein k is a non-negative integer,

wherein Δ

_PRS is an integer between 0 and 2^k−

1, and

wherein the transmit positioning occasions of the cell are defined by r2^k+Δ

_PRS, r being a non-negative integer.

29. The network node of claim 28, wherein the muting pattern determining unit determines the shift Δ

_PRS based on a physical cell identity (PCI) of the cell, a PRS frequency reuse factor for PRS signals of the network, and the step factor k.

30. The network node of claim 29, wherein the muting pattern determining unit determines the shift Δ

_PRS of the cell also based on an antenna index which uniquely identifies a location of an antenna corresponding to the antenna index.

31. The network node of claim 28,

wherein the cell is associated with a relay device arranged to relay signals to and from a base station, and

wherein the shift Δ

_PRS for the cell in which the positioning reference signal from the base station is relayed by the relay device is set such that the transmit positioning occasion of the relay device does not overlap with the transmit positioning occasion of at least one cell associated with the base station.

32. The network node of claim 28,

wherein the positioning parameters for the cell further includes a transmit subframe index Δ

as the transmit subframe indicator,

wherein Δ

is an integer between 0 and N_PRS, and

wherein the suframes in which the cell transmits its PRS signal are defined by N(r2^k+Δ

_PRS)+Δ

.

33. The network node of claim 32,

wherein the positioning parameters for the cell further includes a periodicity factor n as the positioning occasion periodicity indicator,

wherein n is a non-negative integer, and

wherein N and n are related according to N=a2ⁿ, a being a number of subframes in a frame.

34. The network node of claim 27,

wherein the communication unit provides assistance information to the UE,

wherein the assistance information includes the muting patterns of one or more cells for which the muting pattern have been determined and whose PRS transmissions are to be measured by the UE, and

wherein the assistance information for each cell comprises any one or more of the skip indicator, the transmit positioning occasion indicator, the transmit subframe indicator, and the positioning occasion periodicity indicator.

35. The network node of claim 34, wherein the communication unit is arranged to receive muting patterns of one or more cells of the wireless network from at least one other network node.

36. The network node of claim 35, wherein the network node is a positioning node.

37. The network node of claim 34, wherein the cells whose PRS transmissions are to be measured by the UE include a serving cell and/or one or more cells neighboring the serving cell.

38. The network node of claim 34,

wherein the network is an asynchronous network, and

wherein the assistance information includes the transmit subframe indicator and the positioning occasion periodicity indicator of the cells.

39. The network node of claim 34,

wherein the network is a synchronous network,

wherein the transmit positioning occasions coincide for all cells to be measured by the UE, and

wherein the assistance information includes

the transmit subframe indicator and the positioning occasion periodicity indicator of a reference cell, and

the skip indicators and the transmit positioning occasion indicators of all cells.

40. The network node of claim 39, wherein the reference cell is a serving cell.

41. The network node of claim 25, wherein each positioning occasion is composed of N_PS consecutive positioning subframes of N_PRS subframes such that N_PRS=bN_PS, b being an integer greater than 1.

42. The network node of claim 25,

wherein for at least one cell, the predetermined periodicity of one cell is greater than the predetermined periodicity of at least one other cell, and

wherein a node corresponding to the one cell transmits its PRS at every positioning occasion.

43. The network node of claim 25, wherein the node corresponding to the one cell is a beaconing device.

44. A method of determining a location of a user equipment (UE) based on positioning reference signals (PRS) wirelessly transmitted from cells of a wireless network, wherein some or all cells of the network are capable of wirelessly transmitting the PRS during positioning occasions, each positioning occasion being composed of a predetermined number N_PRS consecutive subframes having a predetermined periodicity of N subframes, N>

N_PRS, such that the N_PRS positioning subframes repeat every N subframes, both N and N_PRS being integers greater than zero, the method comprising;

receiving, by the UE, the PRS transmitted from a plurality of network nodes corresponding to a plurality of cells; and

determining, by the UE, an observed timed difference of arrival (OTDOA) of the PRS transmissions from the plurality of network nodes based on muting patterns of the plurality of cells, the muting patterns of the plurality of cells having been provided to the UE by the network,

wherein the muting pattern of a cell indicates a plurality of positioning occasions in which the cell will transmit its PRS and a plurality of positioning occasions in which the cell will mute its transmission of the PRS, and

wherein a number of muted positioning occasions of the cell is greater than zero.

45. The method of claim 44, further comprising determining, by the UE, a location of the UE based on the OTDOA information.

46. The method of claim 44, further comprising providing the OTDOA information from the UE to the network.

47. A user equipment (UE) arranged to its location based on positioning reference signals (PRS) wirelessly transmitted from cells of a wireless network, wherein some or all cells of the network are capable of wirelessly transmitting the PRS during positioning occasions, each positioning occasion being composed of a predetermined number N_PRS consecutive subframes having a predetermined periodicity of N subframes, N>

N_PRS, such that the N_PRS positioning subframes repeat every N subframes, both N and N_PRS being integers greater than zero, the UE comprising;

a communication unit arranged to receive the PRS transmitted from a plurality of network nodes corresponding to a plurality of cells; and

an observed timed difference of arrival (OTDOA) determining unit arranged to determine OTDOA of the PRS transmissions from the plurality of network nodes based on muting patterns of the plurality of cells, the muting patterns of the plurality of cells having been provided to the UE by the network,

wherein the muting pattern of a cell indicates a plurality of positioning occasions in which the cell will transmit its PRS and a plurality of positioning occasions in which the cell will mute its transmission of the PRS, and

wherein a number of muted positioning occasions of the cell is greater than zero.

48. The UE of claim 47, further comprising a location determining unit arranged to determine a location of the UE based on the OTDOA information.

49. The UE of claim 47, wherein the communication unit is arranged to provide the OTDOA information to the network.