MOBILE COMMUNICATION SYSTEM

• US 20100027483A1
• Filed: 06/14/2007
• Published: 02/04/2010
• Est. Priority Date: 06/19/2006
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Sawahashi, Mamoru, Ofuji, Yoshiaki, Higuchi, Kenichi
• Granted Patent: US 8,520,608 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04J 13/0059 CAZAC [constant-amplitude and zero auto-correlation]
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0051 of dedicated pilots, i.e. pilots destined for a single user or terminal
• CPC Class Codes: H04L 5/0091 Signaling for the administration of the divided path
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning

Abstract

A mobile communication system in which a finite number of reference signal sequences used for uplink channel estimation or the like are reused among multiple cells includes a determining unit configured to determine a frequency band used by user terminals to which a reference signal sequence with a predetermined sequence length is assigned in each of the cells within an interference area, wherein the frequency band is determined to be different from frequency bands used in the other cells. Alternatively, the mobile communication system includes a changing unit configured to autonomously change to another of the reference signal sequences which does not cause interference, upon detecting interference from another of the cells to which the same reference signal sequence is assigned; a determining unit configured to randomly determine a frequency band or a reference signal sequence used by user terminals to which one of the reference signal sequences with a predetermined sequence length is assigned in each of the cells within an interference area; or a shifting unit configured to shift transmission timings of radio subframes in each of the cells within an interference area.

Claims

1. A mobile communication system in which a finite number of reference signal sequences used for uplink channel estimation or the like are reused among multiple cells, comprising:

a determining unit configured to determine a frequency band used by user terminals to which a reference signal sequence with a predetermined sequence length is assigned in each of the cells within an interference area, wherein the frequency band is determined to be different from frequency bands used in the other cells.

2. The mobile communication system as claimed in claim 1, wherein:

for all the cells within the interference area, the frequency band is determined to be different from frequency bands used in all the other cells within the interference area.

3. The mobile communication system as claimed in claim 1, wherein:

for each of the cells to which the same reference signal sequence is assigned within the interference area, the frequency band is determined to be different from frequency bands used in the other cells to which the same reference signal sequence is assigned within the interference area.

4. The mobile communication system as claimed in claim 1, wherein:

the frequency band used in each of the cells is semi-statically determined slowly.

5. The mobile communication system as claimed in claim 1, wherein:

the frequency band used in each of the cells is dynamically determined at each subframe.

6. The mobile communication system as claimed in claim 1, wherein:

the frequency band used in each of the cells is determined based on information signaling to and from the other cells.

7. The mobile communication system as claimed in claim 1, wherein:

the frequency band used in each of the cells is autonomously determined without information signaling to and from the other cells.

8. The mobile communication system as claimed in claim 1, wherein:

the frequency band used in each of the cells is semi-statically determined slowly,

the frequency band used in each of the cells is determined based on information signaling to and from the other cells, and

the frequency band is selected by sharing frequency bands used or unused in the respective cells by means of the signaling.

9. The mobile communication system as claimed in claim 1, wherein:

the frequency band used in each of the cells is semi-statically determined slowly,

the frequency band used in each of the cells is determined based on information signaling to and from the other cells, and

the frequency band is selected by sharing priorities for using frequency bands in the respective cells by means of the signaling.

10. A mobile communication system in which a finite number of reference signal sequences used for uplink channel estimation or the like are reused among multiple cells, comprising:

a changing unit configured to autonomously change to another of the reference signal sequences which does not cause interference, upon detecting interference from another of the cells to which the same reference signal sequence is assigned.

11. A mobile communication system in which a finite number of reference signal sequences used for uplink channel estimation or the like are reused among multiple cells, comprising:

a determining unit configured to randomly determine a frequency band or a reference signal sequence used by user terminals to which one of the reference signal sequences with a predetermined sequence length is assigned in each of the cells within an interference area.

12. A mobile communication system in which a finite number of reference signal sequences used for uplink channel estimation or the like are reused among multiple cells, comprising:

a shifting unit configured to shift transmission timings of radio subframes in each of the cells within an interference area.

13. The mobile communication system as claimed in claim 12, further comprising:

a detecting unit configured to detect collision between a reception timing of a reference signal within an own-cell and a reception timing of another reference signal received from another of the cells;

wherein

the shifting unit shifts the transmission timings when the collision is detected.

14. The mobile communication system as claimed in claim 13, further comprising:

a transmitting unit configured to transmit information about the shifted transmission timings to the other cell.

15. The mobile communication system as claimed in claim 13, wherein:

the shifting unit shifts the transmission timings in consideration of control delay when the collision is detected.

16. The mobile communication system as claimed in claim 13, wherein:

information about the shifted transmission timings is included in control bits used for synchronizing reception timings of uplink signals from user terminals in the cell.