Radio communication system, communication terminal apparatus, base station apparatus, and transmission power control method

• US 7,190,930 B2
• Filed: 08/09/2002
• Issued: 03/13/2007
• Est. Priority Date: 08/10/2001
• Status: Expired due to Fees

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Otsu, Toru, Ohkubo, Shinzo, Kikuchi, Shiro, Yoshino, Hitoshi
• Primary Examiner(s): Anderson; Matthew
• Assistant Examiner(s): PHU, SANH D
• Application Number:
  US10/398,216
• Publication Number:
  US 20040009784A1
• Time in Patent Office: 1,677 Days
• Field of Search: 455/522, 455/503, 455/69, 455/67.11, 455/67.14, 370/318, 370/252, 370/332, 370/333, 370/335, 370/390
• US Class Current: 455/67.11
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/245 taking into account received signal strength
• CPC Class Codes: H04W 52/248 where transmission power control commands are generated based on a path parameter
• CPC Class Codes: H04W 52/327 Power control of multicast channels
• CPC Class Codes: H04W 52/54 Signalisation aspects of the TPC commands, e.g. frame structure

Abstract

The present invention relates to a radio communication system comprising base stations and mobile stations and a method for controlling transmission power in the system where the base station is able to perform multi-point transmission for transmitting the same signal to a plurality of the mobile stations. In the present invention, the mobile station targeted for the multi-point transmission provides the base station of an increase request or a decrease request of the transmission power by respectively transmitting or not transmitting a predetermined signal to the base station.

Claims

1. A method for controlling transmission power in a radio communication system comprising a base station and a mobile station where the base station is able to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station, wherein:

the mobile station targeted for the multi-point transmission provides the base station with an increase request or a decrease request of the transmission power by respectively transmitting or not transmitting a predetermined signal to the base station;

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the predetermined signal is different for each multi-point transmission group.

2. The method for controlling the transmission power as claimed in claim 1, wherein:

the multi-point transmission target mobile station provides the base station of the increase request or the decrease request of the transmission power by respectively transmitting or not transmitting a predetermined code sequence to the base station.

3. The method for controlling the transmission power as claimed in claim 2, wherein:

the multi-point transmission target mobile station determines contents of the transmission power control to be requested to the base station on the basis of receiving quality of received signal from the base station, and transmits the predetermined code sequence to the base station when the contents of the transmission power control is determined to be the increase request of the transmission power to the base station; and

the base station calculates correlation between the signal received from the multi-point transmission target mobile station and the predetermined code sequence pre-stored, and increases the transmission power to the multi-point transmission target mobile station if the correlation value exceeds a predetermined threshold and decreases the transmission power if the correlation value does not exceed the predetermined threshold.

4. A method for controlling transmission power in a radio communication system comprising a base station and a mobile station where the base station is able to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station, wherein:

the base station controls the transmission power in the multi-point transmission in accordance with a transmission power control request of which the request amount of control is the largest in the transmission power control requests from the multi-point transmission target mobile stations; and

the multi-point transmission target mobile station transmits a different code sequence in accordance with the amount of control of the transmission power requested to the base station.

5. The method for controlling the transmission power as claimed in claim 4, wherein:

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the multi-point transmission target mobile station transmits to the base station the code sequence different in accordance with the multi-point transmission group to which that mobile station belongs and the amount of control of the transmission power requested to the base station.

6. The method for controlling the transmission power as claimed in claim 4, wherein:

the multi-point transmission target mobile station does not transmit the code sequence to the base station when that mobile station requests the base station to decrease the transmission power.

7. The method for controlling the transmission power as claimed in claim 4, wherein:

the multi-point transmission target mobile station selects one code sequence from a set of the code sequences in accordance with the amount of control of the transmission power requested to the base station where each code sequence in the set of the code sequences is associated with a different amount of control of the transmission power in advance, and transmits the selected code sequence to the base station; and

the base station calculates correlation between the signal received from the multi-point transmission target mobile station and each code sequence in the set of the code sequences pre-stored, and controls the transmission power to the multi-point transmission target mobile station in accordance with the amount of control of the transmission power that is associated with the code sequence of which the correlation value exceeds a predetermined threshold.

8. The method for controlling the transmission power as claimed in claim 7, wherein:

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the predetermined code sequence is different for each multi-point transmission group.

9. A method for controlling transmission power in a radio communication system comprising a base station and a mobile station where the base station is able to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station, wherein:

the base station controls the transmission power in the multi-point transmission in accordance with a transmission power control request of which the request amount of control is the largest in the transmission power control requests from the multi-point transmission target mobile stations; and

the multi-point transmission target mobile station transmits a predetermined signal to the base station after spreading that signal with a code sequence different in accordance with the amount of control of the transmission power requested to the base station.

10. The method for controlling the transmission power as claimed in claim 9, wherein:

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the multi-point transmission target mobile station transmits a predetermined signal to the base station after spreading that signal with a code sequence different in accordance with the multi-point transmission group to which that mobile station belongs and the amount of control of the transmission power requested to the base station.

11. The method for controlling the transmission power as claimed in claim 9, wherein:

the multi-point transmission target mobile station does not transmit the signal spread with the code sequence to the base station when that mobile station requests the base station to decrease the transmission power.

12. The method for controlling the transmission power as claimed in claim 9, wherein:

the multi-point transmission target mobile station selects one code sequence from a set of the code sequences in accordance with the amount of control of the transmission power requested to the base station where each code sequence in the set of the code sequences is associated with a different amount of control of the transmission power in advance, and transmits a predetermined signal to the base station after spreading that signal with the selected code sequence; and

the base station calculates correlation between the signal received from the multi-point transmission target mobile station and each code sequence in the set of the code sequences pre-stored, performs bit decision to decide whether the correlated received signal is the predetermined signal or not, and controls the transmission power to the multi-point transmission target mobile station in accordance with the amount of control of the transmission power that is associated with the code sequence of which the correlated received signal is decided to be the predetermined signal.

13. The method for controlling the transmission power as claimed in claim 12, wherein:

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the set of the code sequences is different for each multi-point transmission group.

14. A method for controlling transmission power in a radio communication system comprising a base station and a mobile station where the base station is able to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station, wherein:

the base station controls the transmission power in the multi-point transmission in accordance with an amount of control of the transmission power requested from the most mobile stations in the transmission power control requests from the multi-point transmission target mobile stations; and

the multi-point transmission target mobile station transmits a different code sequence in accordance with the amount of control of the transmission power requested to the base station.

15. The method for controlling the transmission power as claimed in claim 14, wherein:

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the multi-point transmission target mobile station transmits to the base station the code sequence different in accordance with the multi-point transmission group to which that mobile station belongs and the amount of control of the transmission power requested to the base station.

16. The method for controlling the transmission power as claimed in claim 14, wherein:

the multi-point transmission target mobile station does not transmit the code sequence to the base station when that mobile station requests the base station to decrease the transmission power.

17. The method for controlling the transmission power as claimed in claim 14, wherein:

the multi-point transmission target mobile station selects one code sequence from a set of the code sequences in accordance with the amount of control of the transmission power requested to the base station where each code sequence in the set of the code sequences is associated with a different amount of control of the transmission power in advance, and transmits the selected code sequence to the base station; and

the base station calculates correlation between the signal received from the multi-point transmission target mobile station and each code sequence in the set of the code sequences pre-stored, and controls the transmission power to the multi-point transmission target mobile station in accordance with the amount of control of the transmission power that is associated with the code sequence of which the correlation value exceeds a predetermined threshold.

18. The method for controlling the transmission power as claimed in claim 17, wherein:

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the set of the code sequences is different for each multi-point transmission group.

19. A method for controlling transmission power in a radio communication system comprising a base station and a mobile station where the base station is able to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station, wherein:

the base station controls the transmission power in the multi-point transmission in accordance with an amount of control of the transmission power requested from the most mobile stations in the transmission power control requests from the multi-point transmission target mobile stations; and

the multi-point transmission target mobile station transmits a predetermined signal to the base station after spreading that signal with a code sequence different in accordance with the amount of control of the transmission power to the base station.

20. The method for controlling the transmission power as claimed in claim 19, wherein:

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the multi-point transmission target mobile station transmits a predetermined signal to the base station after spreading that signal with a code sequence different in accordance with the multi-point transmission group to which that mobile station belongs and the amount of control of the transmission power requested to the base station.

21. The method for controlling the transmission power as claimed in claim 19, wherein:

the multi-point transmission target mobile station does not transmit the signal spread with the code sequence to the base station when that mobile station requests the base station to decrease the transmission power.

22. The method for controlling the transmission power as claimed in claim 19, wherein:

the multi-point transmission target mobile station selects one code sequence from a set of the code sequences in accordance with the amount of control of the transmission power requested to the base station where each code sequence in the set of the code sequences is associated with a different amount of control of the transmission power in advance, and transmits a predetermined signal to the base station after spreading that signal with the selected code sequence; and

the base station calculates correlation between the signal received from the multi-point transmission target mobile station and each code sequence in the set of the code sequences pre-stored, performs bit decision to decide whether the correlated received signal is the predetermined signal or not, and controls the transmission power to the multi-point transmission target mobile station in accordance with the amount of control of the transmission power that is associated with the code sequence of which the correlated received signal is decided to be the predetermined signal.

23. The method for controlling the transmission power as claimed in claim 22, wherein:

a set of the mobile stations consisting of the multi-point transmission target mobile stations to which the base station transmits the same signal is referred to as a multi-point transmission group; and

the set of the code sequences is different for each multi-point transmission group.

24. A communication terminal device acting as a mobile station communicating with a base station in a radio communication system where the base station is able to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station and comprising a transmission power control requesting part for requesting the base station to increase or decrease the transmission power on the basis of a receiving quality of a received signal from the base station, wherein:

the transmission power control requesting part provides the base station with an increase request or a decrease request of the transmission power by respectively transmitting or not transmitting a predetermined signal to the base station; and

upon being targeted for the multi-point transmission where the same signal is transmitted from the base station, the transmission power control requesting part uses, in signals provided to be different for each multi-point transmission group, a signal assigned for the multi-point transmission group as the predetermined signal.

25. A communication terminal device acting as a mobile station communicating with a base station in a radio communication system where the base station is able to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station and comprising a transmission power control requesting part for requesting the base station to increase or decrease the transmission power on the basis of a receiving quality of a received signal from the base station, wherein:

the transmission power control requesting part provides the base station with an increase request or a decrease request of the transmission power by respectively transmitting or not transmitting a predetermined signal to the base station; and

the predetermined signal is a predetermined code sequence.

26. A communication terminal device acting as a mobile station communicating with a base station in a radio communication system where the base station is configured to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station and comprising a transmission power control requesting part for requesting the base station to increase or decrease the transmission power on the basis of a receiving quality of a received signal from the base station, wherein:

the transmission power control requesting part transmits a different code sequence in accordance with an amount of control of the transmission power requested to the base station.

27. The communication terminal device as claimed in claim 26, wherein:

upon being targeted for the multi-point transmission where the same signal is transmitted from the base station, the transmission power control requesting part uses, in code sequences provided to be different for each multi-point transmission group, a code sequence assigned for the multi-point transmission group as the code sequence.

28. The communication terminal device as claimed in claim 26, wherein:

the communication terminal device does not transmit the code sequence to the base station when that mobile station requests the base station to decrease the transmission power.

29. A communication terminal device acting as a mobile station communicating with a base station in a radio communication system where the base station is configured to perform multi-point transmission for transmitting a same signal to intended target mobile stations among a plurality of mobile stations located in a coverage area of the base station and comprising a transmission power control requesting part for requesting the base station to increase or decrease the transmission power on the basis of receiving quality of received signal from the base station, wherein:

the transmission power control requesting part transmits a predetermined signal to the base station after spreading that signal with a code sequence different in accordance with the amount of control of the transmission power requested to the base station.

30. The communication terminal device as claimed in claim 29, wherein:

upon being targeted for the multi-point transmission where the same signal is transmitted from the base station, the transmission power control requesting part uses, in code sequences provided to be different for each multi-point transmission group, a code sequence assigned for the multi-point transmission group as the code sequence.

31. The communication terminal device as claimed in claim 29, wherein:

the communication terminal device does not transmit the predetermined signal spread with the code sequence to the base station when that mobile station requests the base station to decrease the transmission power.