# US 8,787,915 B2 · Method of cell selection in heirarchical cell structure based on cell quality

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- Number: US 8,787,915 B2
- Document ID: US8787915B2
- Status: Granted
- Kind: B2
- Application number: 13/720,839
- Filed: 2012-12-19
- Published: 2013-05-02
- Granted: 2014-07-22
- Earliest claimed: 2008-03-17
- Assignees: LG Electronics Inc.
- Applicants: LG Electronics Inc.
- Inventors: Sung-Duck Chun; Seung-June Yi; Sung-Jun Park; Young-Dae Lee
- Web page: https://patentgrep.com/patent/US8787915B2

## CPC

- H04W 24/08: Testing, {supervising or monitoring} using real traffic
- H04J 11/0069: {Cell search, i.e. determining cell identity [cell-ID] (design of multiplexing codes H04J13/00; processing access restriction or access information H04W48/16; discovery of network devices for network data management H04W8/005; sounding signals for channel estimation H04L25/0226; structure of reference signals in multicarrier modulation systems H04L27/2613; frame, time or carrier synchronisation in multicarrier modulation systems H04L27/2655)}
- H04W 48/20: Selecting an access point
- H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports}
- H04W 28/18: Negotiating wireless communication parameters
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

A cell selection method where, if a hierarchical cell structure (HCS) is used, a first ranking procedure is performed if the UE has low mobility, and a second ranking procedure is performed if the UE has high mobility. When the UE has low mobility, the first ranking procedure is performed for all measured cells that have a highest HCS priority among those cells that fulfill a criterion S and a criterion H≧0, or the ranking procedure is performed for all measured cells regardless of HCS priorities if no cell fulfills the criterion S and the criterion H≧0. When the UE has high mobility, the second ranking procedure is performed for all measured cells, and if there are cells with lower HCS priority than the serving cell that fulfills the criterion S and the criterion H≧0, the ranking procedure is performed for all cells that have the highest HCS priority.

## Claims

### Claim 1

A method of cell reselection for a user equipment (UE) in a network, the method comprising:
performing, by the UE, a measurement of cells;
determining, by the UE, whether a hierarchical cell structure (HCS) is used in a serving cell;
if the HCS is not used in the serving cell, performing ranking of the measured cells satisfying a first criterion, wherein the first criterion is a cell selection criterion S that is used to select measured cells satisfying a minimum quality condition;
if the HCS is used in the serving cell, performing ranking of the measured cells satisfying both the first criterion and a second criterion, wherein the second criterion is a quality level threshold criterion H that is used to determine whether a prioritized ranking according to hierarchical cell reselection rules apply; and
performing, by the UE, cell reselection to a best cell in ranking of the measured cells satisfying both the first criterion and the second criterion,
wherein the first criterion is considered prior to the second criterion when performing ranking of the measured cells.

### Claim 2 (depends on 1)

The method of claim 1, wherein the HCS defines a number of overlapping cells of different sizes that form multiple cell layers.

### Claim 3 (depends on 1)

The method of claim 1, wherein the second criterion is not considered if the HCS is not used in the serving cell.

### Claim 4 (depends on 1)

The method of claim 1, the UE is considered to have low mobility or a high mobility based on a number of cell reselections during a certain time period or based on RRC (radio resource control) signaling from the network.

### Claim 5 (depends on 1)

The method of claim 1, wherein the measured cells are determined by performing signal measurement procedures with a base station in all searchable frequency bands, and then a cell having a strongest signal characteristics value is selected among cells that satisfy certain cell selection conditions and an access to the selected cell is performed.

### Claim 6 (depends on 5)

The method of claim 5, wherein at least one of CPICH RSCP (Common Pilot Channel Received Signal Code Power), CPHIC Ec/N0 (carrier to noise ratio) and Carrier RSSI (Received Signal Strength Indicator) is used in the signal measurement procedures.

### Claim 7 (depends on 1)

The method of claim 1, wherein the second criterion is calculated based on information sent in system information and on measurements from a CPICH/P-CPCCH (Common Pilot Channel/Primary-Common Control Physical Channel) of the candidate cell.