Transmission power control method for a wireless communication system

• US 20030086375A1
• Filed: 11/05/2002
• Published: 05/08/2003
• Est. Priority Date: 11/05/2001
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yano, Takashi, Tamaki, Satoshi
• Granted Patent: US 7,428,264 B2
• Time in Patent Office: Days
• US Class Current: 370/235
• CPC Class Codes: H04W 52/242 taking into account path loss
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 52/247 where the output power of a terminal is based on a path parameter sent by another terminal
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment

Abstract

Transmission power relative to a propagation path having a variation in gain is controlled to increase communication channel capacity, and a data rate is controlled in accordance with the variation of the increased communication channel capacity. In order to increase the communication channel capacity, the transmission power is determined so that the sum of noise power (=received noise power/propagation path gain) converted into one at a transmitter and the transmission power becomes constant. As a result, contrary to the background art, the transmission power is controlled to be reduced when the propagation path gain decreases and to be increased when the propagation path gain increases.

Claims

1. A communication control method for a wireless communication system constituted by a plurality of Wireless Communication Stations, comprising the steps of:

measuring a propagation path gain and reception quality in a first one of said Wireless Communication Stations;

transmitting information of said measured propagation path gain and information of said measured reception quality in said first Wireless Communication Station;

receiving said transmitted propagation path gain information and said transmitted reception quality information in a second one of said Wireless Communication Stations;

making transmission power control in said second Wireless Communication Station so as to increase transmission power thereof when said propagation path gain becomes high, and to reduce said transmission power when said propagation path gain becomes low; and

making data rate control so as to increase a data rate when said reception quality is good, and so as to reduce said data rate when said reception quality is not good.

2. A wireless communication system comprising first and second Wireless Communication Stations, wherein:

said first Wireless Communication Station includes;

a measuring portion for measuring a propagation path gain and reception quality;

a control signal generating portion for generating a transmission control signal in accordance with said measured propagation path gain and said measured reception quality; and

a transmitting portion for transmitting said transmission control signal; and

said second Wireless Communication Station includes;

a receiving portion for receiving said transmission control signal; and

a control portion for controlling transmission power and a data rate in accordance with said transmission control signal.

3. A wireless communication system according to claim 2, wherein said control signal generating portion includes:

a power control signal generating portion for generating a power control signal in accordance with said propagation path gain;

a reception quality information generating portion for generating a signal indicating reception quality based on an error of a received signal; and

a multiplexing portion for multiplexing said signals from said power control signal generating portion and said reception quality information generating portion.

4. A wireless communication system according to claim 3, wherein said power control signal is a signal for giving an instruction to increase or reduce said transmission power.

5. A wireless communication system according to claim 3, wherein said reception quality information includes presence/absence of any decoding error or the number of decoding errors.

6. A wireless communication system according to claim 2, wherein said control portion makes control to increase said data rate when said reception quality is good and to reduce said data rate when said reception quality is not good, and makes control to increase said transmission power of said second Wireless Communication Station when said propagation path gain becomes high and to reduce said transmission power of said second Wireless Communication Station when said propagation path gain becomes low.

7. A wireless communication system according to claim 6, wherein said control portion sets an average data rate to be high when said propagation path gain becomes high, and sets said average data rate to be low when said propagation path gain becomes low.

8. A wireless communication system according to claim 2, wherein said second Wireless Communication Station suspends transmission of codes to thereby increase said data rate when said reception quality is good.

9. A wireless communication system according to claim 2, wherein said second Wireless Communication Station transmits codes to thereby reduce said data rate when said reception quality is not good, said codes being encoded out of information identical to information which has already been transmitted.

10. A wireless communication system according to claim 2, wherein said first Wireless Communication Station has means for measuring noise power, so as to reduce said transmission power of said second Wireless Communication Station when said noise power becomes high and so as to increase said transmission power of said second Wireless Communication Station when said noise power becomes low.

11. A second Wireless Communication Station in a wireless communication system constituted by first and second Wireless Communication Stations, comprising:

a receiving portion for receiving a transmission control signal transmitted from said first Wireless Communication Station, said transmission control signal reflecting a propagation path gain and reception quality; and

a control portion for controlling transmission power and a data rate in accordance with said transmission control signal.

12. A communication method for Wireless Communication Stations, comprising the steps of:

transmitting error-correction-encoded transmission data in a transmission-side one of said Wireless Communication Stations;

increasing transmission power of said transmission-side Wireless Communication Station when a propagation path gain between said Wireless Communication Stations becomes high;

reducing said transmission power when said propagation path gain becomes low; and

applying iterative decoding to a reception signal in a reception-side one of said Wireless Communication Stations so as to correct reception errors.

13. A wireless communication method according to claim 12, wherein:

control information for giving an instruction to increase said transmission power is received from said reception-side Wireless Communication Station when said propagation path gain becomes high, and control information for giving an instruction to reduce said transmission power is received when said propagation path gain becomes low.

14. A wireless communication method according to claim 12, wherein:

a data rate is set to be high when said propagation path gain becomes high; and

said data rate is set to be low when said propagation path gain becomes low.

15. A wireless communication method for Wireless Communication Stations, comprising the steps of:

receiving control information for giving an instruction to increase transmission power when a propagation path gain measured by a reception-side one of said Wireless Communication Stations becomes higher than a predetermined value; and

increasing said transmission power in accordance with said control information.

16. A wireless communication method in a wireless communication system having a first Wireless Communication Station and a second Wireless Communication Station, comprising the steps of:

measuring a propagation path gain in said first Wireless Communication Station;

transmitting control information generated in accordance with said propagation path gain from said first Wireless Communication Station to said second Wireless Communication Station; and

transmitting transmission data in said second radio communication tool with transmission power based on said control information, said transmission data being subjected to error correction encoding effective for iterative decoding, said transmission power being increased when said propagation path gain becomes high and being reduced when said propagation path gain becomes low.

17. A wireless communication method according to claim 16, wherein:

a data rate is set in said second Wireless Communication Station so as to be high when said propagation path gain becomes high and so as to be low when said propagation path gain becomes low.

18. A wireless communication system comprising:

a first Wireless Communication Station; and

a second Wireless Communication Station;

said first Wireless Communication Station including;

means for measuring a propagation path gain;

a transmission power control information generating portion for generating transmission power control information using said measured propagation path gain;

means for transmitting said transmission power control information; and

means for carrying out error correction decoding by iterative decoding;

said second Wireless Communication Station including;

means for carrying out error correction encoding; and

a transmission power control portion for controlling transmission power in accordance with said transmission power information received from said first Wireless Communication Station;

said transmission power control portion increasing said transmission power when said propagation path gain becomes high, and reducing said transmission power when said propagation path gain becomes low.

19. A wireless communication system according to claim 18, wherein:

said second Wireless Communication Station includes an encoder for setting a data rate to be high when said propagation path gain becomes high, and setting said data rate to be low when said propagation path gain becomes low.

20. A wireless communication system according to claim 19, wherein:

said second Wireless Communication Station includes a multiplexing portion for transmitting transmission data multiplexed with information about said data rate set by said encoder; and

said first Wireless Communication Station includes;

a separating portion for separating said information about said data rate multiplexed with Received Data; and

a decoder for decoding said Received Data based on said separated information about said data rate.

21. A Wireless Communication Station comprising:

means for measuring received power of a signal received from another Wireless Communication Station so as to obtain a propagation path gain;

means for transmitting control information to said another Wireless Communication Station when said propagation path gain becomes higher than a predetermined value, said control information giving an instruction to increase transmission power; and

means for carrying out error correction decoding by iterative decoding.