Method of selecting a cell to connect by radio with a mobile station and a mobile communications terminal therefor

• US 20050170857A1
• Filed: 12/15/2004
• Published: 08/04/2005
• Est. Priority Date: 01/30/2004
• Status: Active Grant

• Current Assignee: LAPIS Semiconductor Co., Ltd. (ROHM Co., Ltd.)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Akahori, Hiroji, Atsumi, Tsuyoshi
• Granted Patent: US 7,171,232 B2
• Time in Patent Office: Days
• US Class Current: 455/525
• CPC Class Codes: H04B 1/7083 Cell search, e.g. using a three-step approach
• CPC Class Codes: H04W 48/20 Selecting an access point

Abstract

A mobile communications system includes an RF processor for transmitting and receiving radio signals to and from a base station, and a base-band processor for spread-spectrum coding a frame signal to be transmitted to transfer it to the RF processor and spread-spectrum decoding a signal transferred from the RF processor to extract a frame signal. The base-band processor includes a rake receiver for demodulating the received signal and a cell selector and processor for selecting a cell to be connected based upon the propagation path and the power of the received signal. The cell selector and processor includes a search circuit for detecting a cell from the received signal, a cell operator for determining a cell from which received is a signal associated with a shorter propagation path, based on the reception timing of the received signal, and a connecting cell selector for selecting a cell to be connected.

Claims

1. A method of selecting a cell formed by a base station to which a mobile station is to be connected, comprising the steps of:

preparing a mobile communications system having a plurality of cells formed by a corresponding plurality of base stations and a mobile station travelable in a radio service area covered by the plurality of cells to communicate by radio with one of the plurality of base stations;

detecting a reception timing of a signal received by the mobile station;

calculating a difference in reception timing between the signals received from any of the plurality of cells;

determining a cell from which the signal was received and with which a shorter propagation path is associated, based on the difference calculated; and

selecting the determined cell as the cell to which the mobile station is to be connected.

2. The method in accordance with claim 1, further comprising the step of connecting by radio the mobile station to the base station forming the selected cell.

3. The method in accordance with claim 1, wherein, when the mobile station is located commonly in at least two of the plurality of cells, a cell is selected which is associated with a shorter propagation path of the received signal than a cell associated with the received signal having a higher reception power.

4. A mobile communications terminal travelable in a radio service area covered by a plurality of cells formed by a corresponding plurality of base stations for selecting one of the plurality of cells which is formed by a base station to be connected, comprising:

a transmitter/receiver for transmitting and receiving a radio signal to and from any of the plurality of base stations; and

a base-band processor for spread-spectrum coding a frame signal to be transmitted to deliver the coded frame signal to said transmitter/receiver, and spread-spectrum decoding the signal received by said transmitter/receiver to then extract the frame signal,

said base-band processor comprising;

a signal receiver for demodulating the received signal; and

a cell selecting and processing circuit for selecting a cell to be connected on a basis of a propagation path associated with the received signal and an electric power of the received signal.

5. The mobile communications terminal in accordance with claim 4, wherein said cell selecting and processing circuit comprises:

a detector for generating a time slot for detecting a reception timing of the received signal to detect the reception timing of the received signal;

a cell operator for calculating a difference in reception timing between signals received from at least two of the plurality of cells to determine a cell from which the signal was received which is associated with a shorter propagation path; and

a correlator for finding out correlation of the received signals to calculate the electric power of the received signal.