METHOD AND APPARATUS FOR SELECTING REFERENCE TAG USED FOR POSITIONING

• US 20130088334A1
• Filed: 11/28/2012
• Published: 04/11/2013
• Est. Priority Date: 02/24/2011
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Pan, Lujia, Chen, Ai
• Granted Patent: US 9,202,088 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G06K 7/00 Methods or arrangements for sensing record carriers, e.g. for reading patterns methods or arrangements for marking the record carrier in digital fashion G06K1/00; pattern recognition G06F18/00; arrangements for image or video recognition or understanding G06V10/00; character recognition, recognising digital ink or document-oriented image-based pattern recognition G06V30/00
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method and an apparatus for selecting a reference tag used for positioning are provided. The method includes: obtaining first signal strength emitted by a reference tag and second signal strength emitted by a tag to be positioned, where the first signal strength and the second signal strength are detected by each radio frequency reader; comparing the first signal strength with the second signal strength to determine a boundary of the radio frequency readers, and dividing a network into a first area and a second area with the boundary; determining an estimated direction of the tag to be positioned relative to the reference tag according to a relative position of the reference tag and the boundary; and according to the estimated direction and according to the specified number of reference tags, selecting a valid reference tag group as the reference tag used for positioning.

Claims

1. A method for selecting a reference tag used for positioning, the method comprising:

obtaining first signal strength emitted by a reference tag and second signal strength emitted by a tag to be positioned, wherein the first signal strength and the second signal strength are detected by each radio frequency reader;

comparing the first signal strength with the second signal strength to determine a boundary of each radio frequency reader, and dividing a network into a first area and a second area with the boundary;

determining an estimated direction of the tag to be positioned relative to the reference tag according to a relative position of the reference tag and the boundary; and

according to the estimated direction and the specified number of reference tags, selecting a valid reference tag group as the reference tag used for positioning.

2. The method according to claim 1, wherein in a situation that multiple valid reference tag groups exist, the selecting the valid reference tag group as the reference tag used for positioning comprises:

according to a Euclidean distance between every two reference tags in the multiple valid reference tag groups, selecting an optimal valid reference tag group as the reference tag used for positioning.

3. The method according to claim 1, wherein in a situation that the valid reference tag group does not exist, the selecting the valid reference tag group as the reference tag used for positioning comprises:

reducing the specified number of reference tags, and according to the number of reference tags after reducing, selecting the valid reference tag group as the reference tag used for positioning.

4. The method according to claim 1, wherein if the number of reference tags in a pre-selected valid reference tag group is greater than or equal to three, the selecting the valid reference tag group according to the estimated direction and the specified number of reference tags comprises:

according to the number of the reference tags in the pre-selected valid reference tag group, selecting reference tags and forming a reference tag group to be determined; and

judging whether the estimated directions determined for each reference tag in the reference tag group to be determined all point to the inside of a polygon using each reference tag as a vertex, and if yes, determining the reference tag group to be determined as the valid reference tag group.

5. The method according to claim 1, wherein if the number of reference tags in a pre-selected valid reference tag group is two, the selecting the valid reference tag group according to the estimated direction and the specified number of reference tags comprises:

computing a weight of each reference tag relative to the tag to be positioned; and

selecting two reference tags with weights satisfying a preset condition to form the valid reference tag group.

6. The method according to claim 5, wherein if the number of the reference tags in the pre-selected valid reference tag group is two, determine a position of the tag to be positioned according to the following manner:

solving

7. The method according to claim 1, wherein the reference tag is located in the first area, and the determining the estimated direction of the tag to be positioned relative to the reference tag according to the relative position of the reference tag and the boundary comprises:

determining a direction perpendicular to the boundary and pointing to the second area as the estimated direction of the tag to be positioned relative to the reference tag.

8. An apparatus for selecting a reference tag used for positioning, the apparatus comprising:

a signal strength obtaining unit, configured to obtain first signal strength emitted by a reference tag and second signal strength emitted by a tag to be positioned, wherein the first signal strength and the second signal strength are detected by each radio frequency reader;

a boundary determining unit, configured to compare the first signal strength with the second signal strength to determine a boundary of each radio frequency reader, and divide a network into a first area and a second area with the boundary;

an estimated direction determining unit, configured to, according to a relative position of the reference tag and the boundary, determine an estimated direction of the tag to be positioned relative to the reference tag; and

a reference tag selecting unit, configured to, according to the estimated direction and the specified number of reference tags, select a valid reference tag group as the reference tag used for positioning.

9. The apparatus according to claim 8, wherein in a situation that multiple valid reference tag groups exist, the apparatus comprises:

an optimizing unit, configured to, according to a Euclidean distance between every two reference tags in the multiple valid reference tag groups, select an optimal valid reference tag group as the reference tag used for positioning.

10. The apparatus according to claim 8, wherein in a situation that the valid reference tag group does not exist, the apparatus comprises:

a reselecting unit, configured to reduce the specified number of reference tags, and according to the number of reference tags after reducing, select a valid reference tag group as the reference tag used for positioning.

11. The apparatus according to claim 10, wherein if the number of reference tags in a pre-selected valid reference tag group is greater than or equal to three, the reference tag selecting unit comprises:

an initial selecting subunit, configured to, according to the number of the reference tags in the pre-selected valid reference tag group, select reference tags to form a reference tag group to be determined; and

a judging subunit, configured to judge whether estimated directions determined for each reference tag in the reference tag group to be determined all point to the inside of a polygon using each reference tag as a vertex, and if yes, determine the reference tag group to be determined as the valid reference tag group.

12. The apparatus according to claim 10, wherein if the number of reference tags in a pre-selected valid reference tag group is two, the reference tag selecting unit comprises:

a computing subunit, configured to compute a weight of each reference tag relative to the tag to be positioned; and

a determining subunit, configured to select two reference tags with weights satisfying a preset condition to form the valid reference tag group.

13. The apparatus according to claim 10, wherein the reference tag is located in the first area, and the estimated direction determining unit is specifically configured to:

determine a direction perpendicular to the boundary and pointing to the second area as the estimated direction of the tag to be positioned relative to the reference tag.