Method for small cell discovery in heterogeneous network
Methods for small cell discovery in heterogeneous networks are proposed for efficient cell search and better power saving. In one novel aspect, a user equipment (UE) measures small cells only when the UE enters into the vicinity of the small cells. For example, the UE detects the proximity of small cells and reports proximity indication information to the network. Based on the vicinity indication, the network provides suitable measurement configuration for small cells. In a second novel aspect, the UE performs guided search for small cell discovery. In a third novel aspect, the UE increases search rate for small cells when it is in the vicinity of small cells, and decreases search rate for small cells when it is not in the vicinity of small cells. The detection may be based on location information provided by the network or based on vicinity detection information autonomously stored by the UE.
1. A method, comprising:
receiving a measurement configuration from a base station by a user equipment (UE) in radio resource control (RRC) connected mode in a mobile communication network, wherein the measurement configuration comprises a plurality of measurement objects and at least one of the measurement objects is related to small cell measurements;
determining whether the UE is in vicinity of a small cell;
changing mobility measurements of the small cell by the UE based on said determination and the measurement configuration before receiving a subsequent measurement configuration from the base station;
increasing search rate for small cells if the UE is in vicinity of the small cell; and
decreasing search rate for small cells if the UE is not in vicinity of the small cell, wherein the UE is capable of determining whether the UE is in vicinity of the small cell.
2. The method of claim 1 , further comprising:
transmitting proximity indication information to the base station, wherein the proximity indication information includes at least a carrier frequency of the small cell, wherein the proximity indication information is transmitted in response to receiving a proximity request from the base station.
3. The method of claim 1 , further comprising:
receiving cell ID information, about one or multiple neighbor small cells, from the base station such that the UE can detect and identify the small cells faster and with less battery consumption.
4. The method of claim 1 , further comprising:
receiving location information from the base station such that the UE can determine whether the UE moves into the vicinity of the small cell.
5. The method of claim 4 , further comprising:
receiving frequency information about the small cells, or reference to measurement objects configured for the UE, such that the UE can search for the small cells.
6. The method of claim 4 , wherein the location information contains radio signal parameters of neighboring cells related to coverage of the small cell.
7. The method of claim 4 , wherein the location information contains a geographical area configuration based on latitude and longitude.
8. The method of claim 1 , wherein the determining is based on vicinity detection information autonomously stored by the UE, and wherein the small cell is not a closed subscriber group (CSG) cell.
9. The method of claim 8 , wherein the UE stores the vicinity detection information only for cells that the UE has received a signaling indication that the UE may store said information.
10. The method of claim 8 , wherein the stored vicinity detection information contains a location of the small cell and/or the radio signal measurements of neighboring cells of the small cell.
11. A user equipment (UE), comprising:
a receiver that receives a measurement configuration in radio resource control (RRC) connected mode from a base station in a mobile communication network, wherein the measurement configuration comprises a plurality of measurement objects and at least one of the measurement objects is related to small cell measurements;
a cell vicinity-detection module that determines whether the UE is in vicinity of a small cell;
a transmitter that transmits proximity indication information to the base station, wherein the proximity indication information includes at least a physical cell ID and a carrier frequency of the small cell;
a measurement module that performs measurements over the carrier frequency of the small cell, wherein the UE increases search rate for small cells if the UE is in vicinity of the small cell, and wherein the UE decreases search rate for small cells if the UE is not in vicinity of the small cell before receiving a subsequent measurement configuration from the base station.
12. The UE of claim 11 , wherein the receiver receives cell ID information about one or multiple neighbor small cells from the base station such that the UE can identify the small cell.
13. The UE of claim 11 , wherein the receiver receives at least location information from the base station such that the UE can determine whether the UE moves into the vicinity of the small cell.
14. The UE of claim 13 , wherein the receiver receives at least frequency information about the small cells, or reference to measurement objects configured for the UE, such that the UE can search for the small cells.
15. The UE of claim 13 , wherein the location information contains at least a location of the small cell and coverage information of neighboring cells of the small cell.
16. The UE of claim 11 , wherein the determining is based on vicinity detection information autonomously stored by the UE, and wherein the small cell is not a closed subscriber group (CSG) cell.
17. The UE of claim 16 , wherein the UE stores vicinity detection information only for cells that the UE has received a signaling indication that the UE may store said information.
18. The UE of claim 16 , wherein the stored vicinity detection information contains a location of the small cell and coverage information of neighboring cells of the small cell.
19. A method, comprising:
receiving measurement configuration and a proximity request from a base station by a user equipment (UE) in radio resource control (RRC) connected mode in a mobile communication network, wherein the measurement configuration includes a measurement object configured for a preferred cell with at least a cell ID and location information;
in response to receiving the proximity request, applying proximity detection on whether the UE is in vicinity of the preferred cell based on the location information; and
performing measurements for the preferred cell based on the measurement configuration, wherein the UE continues to perform measurements for the preferred cell when the radio signal strength/quality of a serving cell is better than a stop-measurement threshold if the UE is in vicinity of the preferred cell, and wherein the UE stops measurements for the preferred cell when the radio signal strength/quality of the serving cell is better than the stop-measurement threshold if the UE is not in vicinity of the preferred cell.
20. The method of claim 19 , wherein the location information contains at least a GPS location of the preferred cell and radio signal parameters of neighboring cells related to coverage of the preferred cell.
21. A user equipment (UE), comprising:
a receiver that receives measurement configuration from a base station in a mobile communication network in radio resource control (RRC) connected mode, wherein the measurement configuration includes a measurement object configured for a preferred cell with at least a cell ID and location information;
a cell vicinity-detection module that determines whether the UE is in vicinity of the preferred cell based on the location information; and
a measurement module that performs measurements for the preferred cell based on the measurement configuration, wherein the UE continues to perform measurements for the preferred cell when the radio signal strength/quality of a serving cell is better than a stop-measurement threshold if the UE is in vicinity of the preferred cell, and wherein the UE stops measurements for the preferred cell when the radio signal strength/quality of the serving cell is better than the stop-measurement threshold if the UE is not in vicinity of the preferred cell.
22. The UE of claim 21 , wherein the location information contains at least a GPS location of the preferred cell and radio signal parameters of neighboring cells related to coverage of the preferred cell.