Base station transmission power control system, mobile station and base station

• US 20060183481A1
• Filed: 04/13/2006
• Published: 08/17/2006
• Est. Priority Date: 02/16/1998
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Hamabe, Kojiro, Furukawa, Hiroshi, Yoshida, Shousei
• Granted Patent: US 7,203,495 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• 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 52/40 during macro-diversity or soft handoff
• CPC Class Codes: H04W 76/10 Connection setup

Abstract

In soft hand over in a code division multi access mobile radio communication system, interference in a down link caused by transmission from a plurality of base stations for one mobile station, can be restricted. Control of transmission power is performed according to command from the mobile station only in the base station serving as a primary base station which has minimum propagation loss with the mobile station during soft hand over, and the base stations other than the primary base station perform transmission with restricting output. In comparison with the transmission power control performed by the conventional plural base station transmission, interference for the peripheral mobile station can be reduced to achieve higher down link capacity. Also, upon restricting transmission power of the base station other than the base stations having small propagation loss with the mobile station among base station group in soft hand over, by moderately attenuating the transmission power instead of restricting abruptly, degradation of the reception quality can be prevented when error is caused in selection of the base station.

Claims

1. A mobile station in a code division multi access cellular mobile radio communication system comprising a plurality of base stations respectively announcing unique pilot signals, said mobile station being capable of simultaneously establishing connection with a soft hand over base station group comprising some of base stations out of said plurality of base stations in the system, said mobile station comprising;

a primary base station detecting means for detecting primary base station which transmits a pilot signal of the maximum reception level at said mobile station among received pilot signals from said base stations in said soft hand over base station group;

a base station transmission power control signal determining means for setting a base station transmission power control signal indicating to increase or decrease a transmission power; and

a control signal transmitting means for transmitting primary base station information detected by said primary base station detecting means and said base station transmission power control signal determined by said base station control signal determining means to said base station group in soft hand over.

2. A mobile station according to claim 1, said mobile station further comprising

a reception quality detecting means for detecting a communication reception quality,

wherein said base station transmission power control signal determining means sets the base station transmission power control signal for increasing the transmission power in the event that the communication reception quality detected by said reception quality detecting means does not exceed a desired quality and sets the base station transmission power control signal for decreasing the transmission power in the event that the communication reception quality detected by said reception quality detecting means exceeds a desired quality.

3. A mobile station according to claim 1, wherein said control signal transmitting means continuously transmits said base station transmission power control signal determined by said base station control signal determining means to the base station group in soft hand over or intermittently transmits the primary base station information detected by said primary base station detecting means and said base station transmission power control signal determined by said base station control signal determining means to said base station group in soft hand over.

16. A mobile station according to claim 1, said mobile station further comprising

a reception quality detecting means for detecting a communication reception quality,

wherein said base station transmission power control signal determining unit sets the base station transmission power control signal for increasing the transmission power in the event that the communication reception quality detected by said reception quality detecting unit does not exceed a desired quality and sets the base station transmission power control signal for decreasing the transmission power in the event that the communication reception quality detected by said reception quality detecting unit exceeds a desired quality.

4. A base station transmission power control system in a code division multi access cellular mobile radio communication system, said communication system comprising:

a plurality of base stations respectively announcing unique pilot signals and

a mobile station which is capable of simultaneously establishing connection with a soft hand over base station group comprising some of base stations out of said plurality of base stations,

said mobile station detects a primary base station, a reception level of a pilot signal received from the primary base station is maximum level among reception levels of pilot signals received from respective base stations in soft hand over base station group,

said mobile station sets one of a power increasing symbol and a power decreasing symbol in said transmission power control bit, and transmits said transmission power control bit and primary base station information to said soft hand over base station group, and

each base station of said soft hand over base station group receives a transmission power control signal which includes said primary base station information, and restricts a transmission power of a transmission signal to the mobile station in the event that said primary base station information is not consistent with a base station information of said base stations.

5. A base station transmission power control system according to claim 4, wherein

said mobile station detects a communication reception quality, and

said mobile station sets said power increasing symbol in said transmission power control bit in the event that said communication reception quality does not exceed a desired quality, and sets said power decreasing symbol in said transmission power control bit in the event that said communication reception quality exceeds said desired quality.

6. A base station transmission power control system according to claim 4, wherein said mobile station intermittently transmits said primary base station information to said soft hand over base station group.

7. A base station transmission power control system according to claim 4, wherein said base station controls the transmission power of the transmission signal to the mobile station according to one of said power increasing symbol and said power decreasing symbol in the event that said primary base station information in the transmission power control signals is consistent with the base station information of said base station.

8. A base station transmission power control system according to claim 4, wherein the restricted transmission power is a minimum transmission power.

9. A communication control method in a code division multi access cellular mobile radio communication system, said communication system comprising a plurality of base stations respectively announcing unique pilot signals and

a mobile station which is capable of simultaneously establishing connection with a soft hand over base station group comprising some of base stations out of said plurality of base stations, said communication control method comprises:

a step of detecting a primary base station among said base stations, a reception level of a pilot signal received from the primary base station which is the maximum level among reception levels of pilot signals received from respective base stations in said soft hand over base station group;

a step of setting one of a power increasing symbol and a power decreasing symbol in a transmission power control bit; and

a step of transmitting said transmission power control bit and primary base station information to said soft hand over base station group.

10. A communication control method according to claim 9, further comprising:

a step of detecting a communication reception quality,

a step of receiving a transmission power control signal which includes said primary base station information, and

a step of restricting a transmission power of a transmission signal to the mobile station in the event that said primary base station information is not consistent with the base station information of said base station.

11. A communication control method according to claim 9, wherein said power increasing symbol is set in said transmission power control bit in the event that said communication reception quality does not exceed a desired quality, and said power decreasing symbol is set in said transmission power control bit in the event that said communication reception quality exceeds said desired quality.

12. A communication control method according to claim 9, wherein in said primary base station information is intermittently transmitted to said soft hand over base station group.

13. A communication control method according to claim 9, further comprising a step of controlling said transmission power of the transmission signal to the mobile station according to one of said power increasing symbol and said power decreasing symbol in the event that said primary base station information in the transmission power control signal is consistent with the base station information of said base station.

14. A communication control method according to claim 10, wherein the restricted transmission power is a minimum transmission power.

15. A mobile station in a code division multi access cellular mobile radio communication system comprising a plurality of base stations respectively announcing unique pilot signals, said mobile station being capable of simultaneously establishing connection with a soft hand over base station group comprising some of base stations out of said plurality of base stations in the system, said mobile station comprising;

a primary base station detecting unit which detects primary base station which transmits a pilot signal of the maximum reception level at said mobile station among received pilot signals from said base stations in said soft hand over base station group;

a base station transmission power control signal determining unit which sets a base station transmission power control signal indicating to increase or decrease a transmission power; and

a control signal transmitting unit which transmits primary base station information detected by said primary base station detecting means and said base station transmission power control signal determined by said base station control signal determining means to said base station group in soft hand over.

17. A mobile station in a code divisional multi access cellular mobile radio communication system comprising a plurality of base stations respectively announcing unique pilot signals, said mobile station being capable of simultaneously establishing connection with a soft hand over base station group comprising some of base stations out of said plurality of base stations in the system, said mobile station comprising:

a reception quality detecting unit which detects a communication reception quality,

a primary base station detecting unit which detects primary base station which transmits a pilot signal of the maximum reception level at said mobile station among received pilot signals from said base stations in said soft hand over base station group;

a base station transmission power control signal determining unit which sets a base station transmission power control signal indicating to increase or decrease a transmission power; and

a control signal transmitting unit which transmits a primary base station information detected by said primary base station detecting unit and said base station transmission power control signal determined by said base station control signal determining unit to said base station group in soft hand over;

wherein said control signal transmitting unit transmits said base station transmission power control signal determined by said base station control signal determining unit to the base station group in soft hand over or intermittently transmits the primary base station information detected by said primary base station detecting unit and said base station transmission power control signal determined by said base station control signal determining unit to said base station group in soft hand over.

18. A communication control method in a code division multi access cellular mobile radio communication system, said communication system comprising a plurality of base stations respectively announcing unique pilot signals, said mobile station being capable of simultaneously establishing connection with a soft hand over base station group comprising some of base stations out of said plurality of base stations in the system, said control method comprising the steps of:

detecting a primary base station which transmits a pilot signal of the maximum reception level at said mobile station among received pilot signals from said base stations in said soft hand over base station group;

setting a base station transmission power control signal indicating to increase or decrease a transmission power; and

transmitting primary base station information corresponding to said detected primary base station and said base station transmission power control signal to the soft hand over base station group.

19. A communication control method to claim 18, further comprising the step of:

detecting a communication reception quality,

wherein said base station transmission power control signal is set for increasing the transmission power in the event that the detected communication reception quality does not exceed a desired quality and said base station transmission power control signal is set for decreasing the transmission power in the event that detected communication reception quality exceeds the desired quality.

20. A communication control method to claim 18, wherein said base station transmission power control signal is continuously transmitted to said base stations in said soft hand over base station group or the primary base station information detected is intermittently transmitted to said base stations in said soft hand over base station group.