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Cell search control method, mobile station and mobile communications system
| Details |
Inventors: Ishikawa, Yoshihiro; Imai, Tetsuro; Sawahashi, Mamoru; Onoe, Seizo;
Assignee: NTT DoCoMo, Inc. (Tokyo, JP)
Primary Examiner: Orgad; Edan
Assistant Examiner:
Attorney, Agent or Firm: Workman Nydegger
A cell search control method, a mobile station and a mobile communications system can save consumption power with maintaining high accuracy for selecting a base station. The mobile station measures receiving quality (highest received power and the like) of a currently captured perch channel of a base station; automatically makes a decision as to whether the mobile station is located at a cell periphery in which the need for searching for a new perch channel is great, or located in neighborhood of a base station in which the need is little; and increases the frequency of the search at a location where the need is great and decreases it at a location where the need is little. |
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DETAILED DESCRIPTION The present invention is implemented to solve the foregoing problems.
It is therefore an object of the present invention to provide a (peripheral) cell search control method of a mobile station capable reducing the consumption power with maintaining the accuracy of selecting a best base station.
FIG.
3 is a schematic diagram illustrating the operation of the present invention.
As shown in this figure, consider a case in which a mobile station 312 moves along the arrow through areas covered by four base stations 311-1 311-4, and assume that the mobile station 312 captures the perch channels of the three base stations 311-1 311-3, but not the perch channel of the base stations 311-4.
When the mobile station 312 is close to one of the base stations, at the start position, for example, it can receive the perch channel from the base stations 311-1 in a good condition.
Accordingly, the need for searching for better base stations is low, and hence reducing the frequency of the search little affects the receiving quality.
However, when the mobile station is close to a boundary between a plurality of cells, the need increases for switching to the perch channel of another better base station, and the probability also increases of receiving a perch channel of a new base station such as the base station 311-4 whose perch channel is not captured.
The received power (received level) of a perch channel is high when the mobile station is close to the base station, while it is low when the mobile station is at a cell periphery, that is, near a cell boundary between a plurality of cells.
When the mobile station is close to one of the base stations, since the received power of the perch itself is high, and the probability is low of receiving interference from perches of other stations, the received SIR (Signal to Interference power Ratio) of the perch channel is high.
On the contrary, when the mobile station is at the cell periphery, that is, near the cell boundary between a plurality of cells, since the received power itself of the perch channels is low, and the probability is high of receiving interference from perches of other base stations, the received SIR of the perch channels is low
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Cell Phones 
