Multipath detection

• US 9,961,666 B2
• Filed: 10/30/2014
• Issued: 05/01/2018
• Est. Priority Date: 10/30/2014
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Ubeda Castellanos, Carlos, Vera Nadales, M Josefa
• Primary Examiner(s): Ly, Nghi H
• Application Number:
  US15/521,661
• Publication Number:
  US 20170230931A1
• Time in Patent Office: 1,279 Days
• Field of Search: 455418, 455421, 455423, 455424
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination

Abstract

The invention relates to a method for detecting multipath propagation in RF signals exchanged between a mobile entity (10) and different cells (31, 32) of a cellular network. The method comprises the steps of obtaining cell location information for a plurality of cells; obtaining a measurement report reported by the mobile entity (10) to the cellular network for a first cell (31) and a second cell (32) of the plurality of cells, the measurement report comprising a parameter related to a first time delay occurring for the RF signal travelling between the first cell (31) and the mobile entity (10), and a parameter related to a second time delay occurring for the RF signal travelling between the second cell (32) and the mobile entity (10). A time delay difference is calculated between the first time delay and the second time delay, and a distance difference is deduced from the time delay difference taking into account the speed of the RF signals travelling between the first cell (31) and the mobile entity (10) and between the second cell (32) and the mobile entity (10). An inter-cell distance between the first cell (31) and the second cell (32) is calculated based on the cell location information for the first cell and the second cell. The inter-cell distance is compared to the distance difference, wherein the multipath propagation is detected based on the result of the comparison.

Claims

1. A method for detecting multipath propagation in RF signals exchanged between a mobile entity and different cells of a cellular network, comprising the steps of:

obtaining cell location information for a plurality of cells,

obtaining a measurement report reported by the mobile entity to the cellular network for a first cell and a second cell of the plurality of cells, the measurement report comprising a parameter related to a first time delay occurring for the RF signal travelling between the first cell and the mobile entity and a parameter related to a second time delay occurring for the RF signal travelling between the second cell and the mobile entity,

calculating a time delay difference between the first time delay and the second time delay,

calculating a distance difference from the time delay difference taking into account the speed of the RF signals travelling between the first cell and the mobile entity and between the second cell and the mobile entity,

calculating an inter-cell distance between the first cell and the second cell based on the cell location information for the first cell and the second cell, and

comparing the inter-cell distance to the distance difference, wherein the multipath propagation is detected based on the result of the comparison.

2. The method according to claim 1, wherein if an absolute value of the distance difference is larger than the inter-cell distance, it is concluded that multipath propagation is present, wherein if the absolute value of the distance difference is smaller or equal than inter-cell distance, it is concluded that no multipath propagation is present.

3. The method according to claim 1, wherein it is deduced from an algebraic sign of the distance difference whether the multipath propagation is present in the propagation between the first cell and the mobile entity or between the second cell and the mobile entity.

4. The method according to claim 1, wherein the cellular network is an asynchronous network, further comprising the step of determining a first synchronization time parameter for the first cell and a second synchronization parameter for the second cell, wherein a synchronization time difference is determined between the two synchronization parameters, and the distance difference is calculated taking into account the synchronization time difference.

5. The method according to claim 4, wherein the synchronization time difference is received from a location measurement node of the cellular network.

6. The method according to claim 4, wherein the first synchronization time parameter and the second synchronization time parameter are received from a location measurement node of the cellular network.

7. The method according to claim 1, wherein the parameter related to the first time delay and the parameter related to the second time delay are deduced from Radio Resource Control measurement reports transmitted from the mobile entity to the cellular network.

8. The method according to claim 1, wherein the parameter related to the first time delay and the parameter related to the second time delay are both a Tm parameter defined by the equation:

T_m=T_UETx−

T₀−

TR_xSFN, with

T_UETx being a time when the mobile entity transmits an uplink Dedicated Physical Channel, T_RxSFN being a time at which the mobile entity receives a primary common control channel frame most recent in time before the time instant T_UETx−

T₀, and T₀ being a constant.

9. The method according to claim 1, further comprising a step of determining a relative time difference between the first cell and the second cell as the difference between a system frame number “

SFN”

transmit time of the first cell and an SFN transmit time of the second cell.

10. The method according to claim 9, wherein the distance difference is calculated by multiplying the addition of the time delay difference and the relative time difference by a constant value.

11. A computer program comprising program code to be executed by at least one processor of a system of a cellular network, wherein execution of the program causes the at least one processor to perform steps of a method according to claim 1.

12. A computer program product comprising program code to be executed by at least one processor of a system of a cellular network, wherein execution of the program causes the at least one processor to perform steps of a method according to claim 1.

13. A system configured to detect multipath propagation in RF signals exchanged between a mobile entity and different cells of a cellular network, comprising:

a receiver configured to receive cell location information for a plurality of cells, a measurement report reported by the mobile entity to the cellular network for a first cell and a second cell of the plurality of cells, the measurement report comprising a parameter related to a first time delay occurring for the RF signal travelling between the first cell and the mobile entity and a parameter related to a second time delay occurring for the RF signal travelling between the second cell and the mobile entity,

a processor configured to calculate a time delay difference between the first time delay and the second time delay, to calculate a distance difference from the time delay difference taking into account the speed of the RF signals travelling between the first cell and the mobile entity and between the second cell and the mobile entity, to calculate an inter-cell distance between the first cell and the second cell based on the cell location information for the first cell and the second cell, and to compare the inter-cell distance to the distance difference, wherein the processor is configured to detect the multipath propagation based on the result of the comparison.

14. The system according to claim 13, wherein the processer is configured to determine an absolute value of the distance difference, wherein if the processor determines that the absolute value is larger than the inter-cell distance it concludes that multipath propagation is present, wherein if the processor determines that the absolute value of the propagation distance is smaller or equal than the inter-cell distance it concludes that no multipath propagation is present.

15. The system according to claim 13, wherein the processor is configured to deduce from an algebraic sign of the distance difference whether the multipath propagation is present in the propagation between the first cell and the mobile entity or between the second cell and the mobile entity.

16. The system according to claim 13, wherein the cellular network is an asynchronous network, wherein the processor is configured to determine a first synchronization time parameter for the first cell and a second synchronization parameter for the second cell, to determine a synchronization time difference between the two synchronization parameters, and to calculate the distance difference taking into account the synchronization time difference.

17. The system according to claim 13, wherein the processor is configured to determine a relative time difference between the first cell and the second cell as the difference between a system frame number “

SFN”

transmit time of the first cell and an SFN transmit time of the second cell.

18. The system according to claim 17, wherein the processor is configured to calculate the distance difference by multiplying the addition of the time delay difference and the relative time difference by a constant value.