INITIATING BLIND HANDOVER

• US 20180070279A1
• Filed: 03/17/2015
• Published: 03/08/2018
• Est. Priority Date: 03/17/2015
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: JALDN, Niklas, STJERNHOLM, Paul, VON BUTOVITSCH, Peter
• Granted Patent: US 10,728,822 B2
• Time in Patent Office: Days
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/24 Reselection being triggered by specific parameters
• CPC Class Codes: H04W 36/362 Conditional handover

Abstract

The disclosure relates to a method (20) for initiating a blind handover of a terminal (2) in a wireless communications system (1). The terminal (2) is served by a first cell using a first frequency band and a first radio access technology, wherein the wireless communications system (1) employs a method for dynamically changing coverage in at least one of the first cell and a second cell. The method (20) comprises estimating (21) the coverage in the second cell, wherein at least one of a second frequency band and a second radio access technology of the second cell may differ from the first frequency band and the first radio access technology, an initiating (22) the blind handover for the terminal (2) to the second cell only if the estimated coverage in the second cell meets a criterion. A wireless communications system (1), computer programs and computer program products are also provided.

Claims

1. A method for initiating a blind handover of a terminal in a wireless communications system, the terminal being served by a first cell using a first frequency band and a first radio access technology, wherein the wireless communications system employs a method for dynamically changing coverage in at least one of the first cell and a second cell, the method comprising:

estimating the coverage in the second cell, wherein at least one of a second frequency band and a second radio access technology of the second cell may differ from the first frequency band and the first radio access technology; and

initiating the blind handover for the terminal to the second cell only if the estimated coverage in the second cell meets a criterion.

2. The method of claim 1, wherein the estimating the coverage in the second cell comprises estimating a link quality metric at the terminal in the second cell.

3. The method of claim 2, wherein the estimating comprises estimating a link quality metric at the terminal in the second cell by performing a process comprising:

establishing spatial channel information for a downlink transmission in the second cell, and

estimating, based on the spatial channel information, a link quality metric of the terminal in the second cell.

4. The method of claim 2, wherein the link quality metric at the terminal in the second cell is estimated by using:

a spatial channel estimate in the first cell based on uplink measurements in the first cell on an uplink frequency band of the first cell, the spatial channel estimate being normalized with respect to an uplink beamformer used in the first cell, and

a cell-shaping vector used in the second cell.

5. The method of claim 4, comprising, for the case that the uplink frequency band in the first cell and a downlink frequency band in the second cell are different and separated by a set spectral distance, performing an uplink to downlink frequency transformation.

6. The method of claim 2, wherein the first cell and second cell are controlled by a first network node and wherein the link quality metric at the terminal in the second cell is estimated based on spatial channel information established by the first network node for one or more previous terminals at the approximate current location of the terminal.

7. The method of claim 2, wherein the link quality metric at the terminal in the second cell is estimated based on spatial channel information established for one or more previous terminals at the approximate current location of the terminal in relation to two or more network nodes.

8. The method of claim 2, wherein the initiating the blind handover comprises initiating the blind handover only if the estimated link quality metric meets a criterion.

9. The method of claim 1, wherein the estimating the coverage in the second cell comprises using a coverage map, created based on spatial channel information for terminal locations in the second cell, and a weight vector used over antenna elements for downlink transmission of the second cell.

10. The method of claim 1, comprising initiating a measurement based handover of the terminal if the estimated coverage fails to meet the criterion.

11. A computer program product comprising a non-transitory computer readable medium storing a computer program for a wireless communications system for initiating a blind handover of a terminal, the computer program comprising computer program code, which, when executed on at least one processor of the wireless communications system causes the wireless communications system to perform the method of claim 1.

12. (canceled)

13. A wireless communications system for initiating a blind handover of a terminal, the terminal being served by a first cell using a first frequency band and a first radio access technology, wherein the wireless communications system employs a method for dynamically changing coverage in at least one of the first cell and a second cell, the wireless communications system being configured to:

estimate the coverage in the second cell, wherein at least one of a second frequency band and a second radio access technology of the second cell may differ from the first frequency band and the first radio access technology, and

initiate the blind handover for the terminal to the second cell only if the estimated coverage in the second cell meets a criterion.

14. The wireless communications system of claim 13, wherein the wireless communications system is configured to estimate the coverage in the second cell by estimating a link quality metric at the terminal in the second cell.

15. The wireless communications system of claim 14, wherein the wireless communications system is configured to estimate a link quality metric at the terminal in the second cell by performing a process comprising:

establishing spatial channel information for a downlink transmission in the second cell, and

estimating, based on the spatial channel information, a link quality metric of the terminal in the second cell.

16. The wireless communications system of claim 14, wherein the wireless communications system is configured to estimate the link quality metric at the terminal in the second cell by:

a spatial channel estimate in the first cell based on uplink measurements in the first cell on an uplink frequency band of the first cell, the spatial channel estimate being normalized with respect to an uplink beamformer used in the first cell, and

a cell-shaping vector used in the second cell.

17. The wireless communications system of claim 16, wherein the wireless communications system is configured t0, for the case that the uplink frequency band in the first cell and a downlink frequency band in the second cell are different and separated by a set spectral distance, perform an uplink to downlink frequency transformation.

18. The wireless communications system of claim 14, wherein the wireless communications system is configured to control the first cell and second cell by a first network node and configured to estimate the link quality metric at the terminal in the second cell based on spatial channel information established by the first network node for one or more previous terminals at the approximate current location of the terminal.

19. The wireless communications system of claim 14, wherein the wireless communications system is configured to estimate the link quality metric at the terminal in the second cell based on spatial channel information established for one or more previous terminals at the approximate current location of the terminal in relation to two or more network nodes.

20. The wireless communications system of claim 14, wherein the wireless communications system is configured to the initiate the blind handover comprises initiating the blind handover only if the estimated link quality metric meets a criterion.

21. The wireless communications system of claim 13, wherein the wireless communications system is configured to estimate the coverage in the second cell by using a coverage map, created based on spatial channel information for terminal locations in the second cell, and a weight vector used over antenna elements for downlink transmission of the second cell.

22. The wireless communications system of claim 13, wherein the wireless communications system is configured to initiate a measurement based handover of the terminal if the estimated coverage fails to meet the criterion.