Communication terminal and method used therein

• US 20050078674A1
• Filed: 10/07/2004
• Published: 04/14/2005
• Est. Priority Date: 10/09/2003
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ohmi, Shinichiro, Yoshida, Shigeo, Yasukawa, Tohru, Koide, Youhei
• Granted Patent: US 7,187,657 B2
• Time in Patent Office: Days
• US Class Current: 370/389
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/20 using signal quality detector

Abstract

The present invention is a communication terminal which modulates and demodulates a packet for transmission and reception based on a communication parameter for modulation and demodulation determined according to a communication-medium characteristic. The communication terminal according to the present invention includes: information-element extracting means which extracts, with each predetermined cycle, information indicative of either one of transmission efficiency and reception quality of the packet as an information element; difference calculating means which calculates, with each said cycle, a difference between a first information element extracted by the information-element extracting means and a second information element previously extracted by the information-element extracting means; and detecting-scheme performance determining means which determines, based on the difference between the first information element and the second information element calculated by the difference calculating means, with each said cycle, whether a scheme of detecting the communication-medium characteristic for changing the communication parameter is to be performed.

Claims

1. A communication terminal which modulates and demodulates a packet for transmission and reception based on a communication parameter for modulation and demodulation determined according to a communication-medium characteristic, comprising:

information-element extracting means which extracts, with each predetermined cycle, information indicative of either one of transmission efficiency and reception quality of the packet as an information element;

difference calculating means which calculates, with each said cycle, a difference between a first information element extracted by the information-element extracting means and a second information element previously extracted by the information-element extracting means; and

detecting-scheme performance determining means which determines, based on the difference between the first information element and the second information element calculated by the difference calculating means, with each said cycle, whether a scheme of detecting the communication-medium characteristic for changing the communication parameter is to be performed.

2. The communication terminal according to claim 1, wherein

the communication terminal is at a side of transmitting the packet, and

the information-element extracting means extracts a ratio of occurrence of retransmission of a transmission packet and an average number of packets not yet transmitted as the information element indicative of the transmission efficiency of the packet.

3. The communication terminal according to claim 1, wherein

the communication terminal is at a side of receiving the packet, and

the information-element extracting means extracts an error correction rate of a reception packet as the information element indicative of the reception quality of the packet.

4. The communication terminal according to claim 1, wherein

the communication terminal is at a side of transmitting the packet, and

the information-element extracting means extracts the information element indicative of the reception quality of the packet based on characteristic information indicative of the reception quality of the packet contained in an ACK packet returned from a communication terminal at a side of receiving the packet.

5. The communication terminal according to claim 2, wherein

the difference calculating means calculates a difference in the ratio of occurrence of retransmission and a difference in the average number of packets not yet transmitted, and

the detecting-scheme performance determining means determines that the detecting scheme is to be performed when the difference in the ratio of occurrence of retransmission is equal to or larger than a predetermined threshold of the difference in the ratio of occurrence of retransmission or the difference in the average number of packets not yet transmitted is larger than a predetermined threshold of the difference in the average number of packets not yet transmitted.

6. The communication terminal according to claim 5, wherein

the detecting-scheme performance determining means further

determines that the detecting scheme is to be performed when a transmission-speed setting value is smaller than a threshold of the transmission-speed setting value.

7. The communication terminal according to claim 3, wherein

the difference calculating means calculates a difference in the error correction rate, and

the detecting-scheme performance determining means determines that the detecting-scheme is to be performed when the difference in the error correction rate is equal to or larger than a threshold of the difference in the error correction rate.

8. The communication terminal according to claim 4, wherein

the characteristic information is information indicative of a size of a portion requiring error correction in the packet received by the communication terminal at the receiving side.

9. The communication terminal according to claim 8, wherein

the information-element extracting means extracts an error correction rate indicative of the reception quality of the received packet as the information element based on the size.

10. The communication terminal according to claim 9, wherein

the difference calculating means calculates a difference in the error correction rate, and

the detecting-scheme performance determining means determines that the detecting-scheme is to be performed when the difference in the error correction rate is equal to or larger than a threshold of the difference in the error correction rate.

11. The communication terminal according to claim 4, wherein

the packet contains a simple evaluation series having a predetermined pattern for evaluating the reception quality,

data of the simple evaluation series is smaller in size than data of an evaluation series which is used when the detecting scheme is performed for evaluating the communication-medium characteristic, and

the characteristic information is any one of a CINR value, an SINR value, and a reception signal intensity calculated based on the data of the simple evaluation series contained in the packet received by the communication terminal at the receiving side.

12. The communication terminal according to claim 11, wherein

the information-element extracting means extracts any one of an average value of a plurality of said CINR values, an average value of a plurality of said SINR values, and an average value of a plurality of said reception signal intensities as the information element indicative of the reception quality of the received packet.

13. The communication terminal according to claim 12, wherein

the difference calculating means calculates any one of a difference in the average value of the CINR values, a difference in the average value of the SINR values, and a difference in the average value of the reception signal intensities, and

the detecting-scheme performance determining means determines that the detecting scheme is to be performed when any calculated one of the difference in the average value of the CINR values, the difference in the average value of the SINR values, and the difference in the average value of the reception signal intensities is equal to or larger than a predetermined threshold.

14. The communication terminal according to claim 1, wherein

the detecting scheme is performed with each predetermined basic cycle, and

the predetermined cycle is shorter than the predetermined basic cycle.

15. The communication terminal according to claim 1, wherein

the predetermined cycle is variable.

16. The communication terminal according to claim 1, further comprising

detecting-scheme performing means which transmits an evaluation-series packet for evaluating the communication-medium characteristic to a communication terminal at a receiving side when the detecting-scheme performance determining means determines that the detecting scheme is to be performed, receives an evaluation-result packet including results of evaluation of the communication-medium characteristic returned from the communication terminal at the receiving side, and changes the communication parameter based on the evaluation-result packet.

17. A method of determining timings of performing a scheme of detecting a communication-medium characteristic for determining a communication parameter for use in modulation and demodulation of a packet, comprising the steps of:

extracting, with each predetermined cycle, information indicative of either one of transmission efficiency and reception quality of the packet as an information element;

calculating, with each said cycle, a difference between a first information element extracted in the information-element extracting step and a second information element previously extracted in the information-element extracting step; and

determining, based on the difference between the first information element and the second information element calculated in the calculating step, with each said cycle, whether a scheme of detecting the communication-medium characteristic for changing the communication parameter is to be performed.

18. The method according to claim 17, wherein

in the information-element extracting step, the information element indicative of the reception quality of the packet is extracted based on characteristic information indicative of the reception quality of the packet contained in an ACK packet returned from a communication terminal at a side of receiving the packet.