Transmission method, radio base station and mobile station

• US 8,948,096 B2
• Filed: 04/22/2010
• Issued: 02/03/2015
• Est. Priority Date: 10/25/2007
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Tanaka, Yoshinori
• Primary Examiner(s): Yao, Kwang B
• Assistant Examiner(s): RAHGOZAR, OMEED DANIEL
• Application Number:
  US12/765,644
• Publication Number:
  US 20100254338A1
• Time in Patent Office: 1,748 Days
• Field of Search: 370329-330, 370/341, 370/431, 370/436, 370437-439, 370/458, 370/498, 370/503, 370/507, 370/509, 370510-514, 370/520
• US Class Current: 370/329
• CPC Class Codes: 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
• CPC Class Codes: H04J 13/0003 Code application, i.e. aspects relating to how codes are applied to form multiplexed channels
• CPC Class Codes: H04J 13/0062 Zadoff-Chu
• CPC Class Codes: H04W 28/16 Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
• CPC Class Codes: H04W 48/12 using downlink control channel
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 8/005 Discovery of network devices, e.g. terminals
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

In a transmission method, a service area covered by a first cell is provided with a plurality of second cells with a smaller radius than the first cell. A first radio base station belongs to a first cell while the second radio base stations belong to different second cells. A transmitter of the first radio base station transmits a synchronization channel in a given band while a transmitter of each second radio base station transmits a synchronization channel in a band that is different from the given band and also from those of other second radio base stations. A control unit of a mobile station narrows down bands to be observed for detecting synchronization channels to the given band or, if there are some of the second cells that the mobile stations are allowed to access, to the given band and the bands corresponding to the accessible second cells.

Claims

1. A transmission method of transmitting a synchronization channel in a radio communication system where a first cell and a second cell are provided, the transmission method comprising:

allocating the first cell to a first transmission band and allocating the second cell to a second transmission band that is different from the first transmission band and overlaps with the first transmission band;

transmitting, in the first cell, a first synchronization channel by using a first partial band of the first transmission band, the first partial band being a central band of the first transmission band; and

transmitting, in the second cell, a second synchronization channel by using a second partial band of the second transmission band, the second partial band being a central band of the second transmission band and different from the first partial band,

wherein an area of the second cell is smaller than an area of the first cell,

wherein the second transmission band of the second cell includes the first partial band used for transmitting the first synchronization channel, and

wherein the first partial band and the second partial band partly overlap each other while a center frequency of the first partial band and a center frequency of the second band are different.

2. A radio base station of a second cell in a radio communication system where a first cell and the second cell are provided, the first cell is allocated to a first transmission band, the second cell is allocated to a second transmission band that is different from the first transmission band and overlaps with the first transmission band, and a first synchronization channel is transmitted in a first partial band of the first transmission band, the radio base station comprising:

a transmitter configured to transmit a second synchronization channel in a second partial band of the second transmission band, the second partial band being a central band of the second transmission band and different from the first partial band,

wherein an area of the second cell is smaller than an area of the first cell,

wherein the first partial band used for transmitting the first synchronization channel is a central band of the first transmission band, and the second transmission band of the second cell includes the first partial band, and

wherein the first partial band and the second partial band partly overlap each other while a center frequency of the first partial band and a center frequency of the second band are different.

3. A mobile station in a radio communication system where a first cell and a second cell are provided, the first cell is allocated to a first transmission band, the second cell is allocated to a second transmission band that is different from the first transmission band and overlaps with the first transmission band, and a first synchronization channel is transmitted in a first partial band of the first transmission band, the mobile station comprising:

a controller configured to control bands used for detecting synchronization channels in a cell search, within the first partial band or, within the first partial band and a second partial band which is a central band of the second transmission band and used for transmitting a second synchronization channel in the second cell to which the mobile station is admitted to access,

wherein an area of the second cell is smaller than an area of the first cell,

wherein the first partial band used for transmitting the first synchronization channel is a central band of the first transmission band, and the second transmission band of the second cell includes the first partial band, and

wherein the first partial band and the second partial band partly overlap each other while a center frequency of the first partial band and a center frequency of the second band are different.

4. A radio communication system comprising a first radio base station of a first cell, a second radio base station of a second cell, and a mobile station, wherein

the first cell is allocated to a first transmission band, and the second cell is allocated to a second transmission band that is different from the first transmission band and overlaps with the first transmission band,

the first radio base station comprises a transmitter configured to transmit a first synchronization channel in a first partial band of the first transmission band, the first partial band being a central band of the first transmission band,

the second radio base station comprises a transmitter configured to transmit a second synchronization channel in a second partial band of the second transmission band, the second partial band being a central band of the second transmission band and different from the first partial band,

an area of the second cell is smaller than an area of the first cell,

the second transmission band of the second cell includes the first partial band used for transmitting the first synchronization channel, and

the first partial band and the second partial band partly overlap each other while a center frequency of the first partial band and a center frequency of the second band are different.

5. The radio communication system according to claim 4, wherein the mobile station comprises a controller configured to search the first and second synchronization channels.

6. The radio communication system according to claim 5, wherein the controller controls bands used for detecting the first and second synchronization channels, within the first partial band or, within the first partial band and the second partial band.