Wireless communication system and transmission power control method therefor

• US 20040037248A1
• Filed: 12/31/2002
• Published: 02/26/2004
• Est. Priority Date: 08/23/2002
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yano, Takashi, Tamaki, Satoshi
• Granted Patent: US 7,233,582 B2
• Time in Patent Office: Days
• US Class Current: 370/332
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels

Abstract

The total amount of power for communications transmitted over channels susceptible to quality fluctuation is decreased to reduce the interference with the other communications and increase the system'"'"'s overall capacity. When channel-encoded data is to be transmitted, the quality of a transmission channel is judged. The data is transmitted when the judged quality is higher than predefined. However, if the quality is lower than predefined, the data transmission to a wireless section is suppressed to avoid a signal transmission that cannot effectively be used at a receiving station, decrease the average transmission power, and reduce the interference with the other communications. Even if the channel quality is lower than predefined at the time of assigning a code word created by channel encoding, the same code word assignment operation as for a transmission portion is performed with respect to a no-transmission portion that a transmitting station does not send to a wireless section. This ensures that when the channel code is decoded at a receiving station, the receiving station can accomplish its reception without having to know which portion was not sent to a wireless section.

Claims

1. A wireless communication system for transmitting data from a first wireless station to a second wireless station,

wherein said first wireless station or said second wireless station includes a channel quality judgment module for judging the quality of a channel between said first wireless station and said second wireless station;

wherein said first wireless station includes a channel coding module for encoding a data signal and a transmission determination module for determining, at predetermined intervals and in accordance with the channel quality judged as described above, whether or not to transmit said encoded data signal;

wherein said second wireless station includes an error correction module for correcting errors by decoding an encoded data signal received from said first wireless station; and

wherein said first wireless station, if said transmission determination module concludes that said encoded data signal should be transmitted, transmits said encoded data signal for at least a predetermined period of time and, if said transmission determination module concludes that said encoded data signal should not be transmitted, suppresses from transmitting said encoded data for a predetermined period of time and transmits a portion after said encoded data signal, which was not sent during the period when said transmission was not made, at the time of sending a transmission during a predetermined period after the predetermined period during which said transmission was not made.

2. The wireless communication system according to claim 1, wherein the length of said period when said transmission was not made is smaller than the code length of said encoded data signal.

3. The wireless communication system according to claim 1, wherein said first wireless station includes a channel quality judgment module, and wherein said channel quality judgment module judges said channel quality in accordance with the channel gain of a channel from said second wireless station to said first wireless station.

4. The wireless communication system according to claim 1, wherein said second wireless station includes a channel quality judgment module, and wherein said channel quality judgment module judges said channel quality in accordance with the channel gain of a channel from said first wireless station to said second wireless station.

5. The wireless communication system according to claim 1, wherein said channel quality judgment module judges said channel quality in accordance with the signal-to-noise power ratio of a received signal.

6. The wireless communication system according to claim 1, wherein the channel quality judgment criteria selected for said channel quality judgment module are based on the code for said encoding.

7. The wireless communication system according to claim 1, wherein the code length of the code used for said encoding varies with said channel quality.

8. The wireless communication system according to claim 1, wherein said first wireless station and said second wireless station establish multicarrier communication to transmit data with a plurality of channels, and wherein said transmission determination module determines whether or not to transmit said encoded data signal on each of said plurality of channels.

9. A transmitting station of a wireless communication system for transmitting data from a transmitting station to a receiving station, comprising:

a channel coding module for encoding a data signal; and

a transmission determination module for determining, at predetermined intervals and in accordance with the channel quality prevailing between said transmitting station and a receiving station, whether or not to transmit said encoded data signal,

wherein said transmitting station, if said transmission determination module concludes that said encoded data signal should be transmitted, transmits said encoded data signal for at least a predetermined period of time and, if said transmission determination module concludes that said encoded data signal should not be transmitted, suppresses from transmitting said encoded data for a predetermined period of time and transmits a portion after said encoded data signal, which was not sent during the period when said transmission is not made, at the time of sending a transmission during a predetermined period after the predetermined period during which said transmission was not made.

10. The transmitting station according to claim 9, further comprising:

a channel quality judgment module, wherein said channel quality judgment module judges said channel quality in accordance with the condition of a channel from said receiving station to said transmitting station.

11. The transmitting station according to claim 9, wherein the length of said period when said transmission is not made is smaller than the code length of said data signal.

12. The transmitting station according to claim 9, wherein a plurality of channels are used for data transmission, and wherein said transmission determination module determines whether or not to transmit said encoded data signal on each channel.

13. The transmitting station according to claim 9, further comprising:

an interleave module for interleaving said encoded data signal, wherein said transmitting station transmits said encoded-and-interleaved signal.

14. A method for transmitting data to a receiving station from a transmitting station for wireless communication, comprising the steps of:

encoding a data signal;

determining, at predetermined intervals and in accordance with the channel quality prevailing between said transmitting station and said receiving station, whether or not to transmit said encoded data signal;

transmitting said encoded data signal for at least a predetermined period of time when it is concluded that said encoded data signal should be transmitted;

refraining from transmitting said encoded data for a predetermined period of time when it is concluded that said encoded data signal should not be transmitted; and

transmitting a portion after said encoded data signal, which was not sent during the period when said transmitting station refrained from transmitting said encoded data, at the time of sending a transmission during a predetermined period after the predetermined period during which the transmitting station refrained from transmitting said encoded data.