Wireless communication system, wireless communication apparatus and wireless communication method, and computer program

• US 20050185628A1
• Filed: 02/02/2005
• Published: 08/25/2005
• Est. Priority Date: 02/06/2004
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sakoda, Kazuyuki, Watanabe, Kazuhiro
• Granted Patent: US 7,715,337 B2
• Time in Patent Office: Days
• US Class Current: 370/347
• CPC Class Codes: H04W 56/002 Mutual synchronization
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

A wireless communication system is constructed by autonomous distributed operation of communication stations without having a relation of a controlling station and controlled stations. In the wireless communication system, each communication station checks a state of time synchronization with a neighboring station, determines whether the time synchronization needs to be corrected, and carries out one of methods of surely performing a time synchronization correcting process and performing the correcting process with a predetermined probability when the time synchronization needs to be corrected.

Claims

1. A wireless communication system constructed by autonomous distributed operation of communication stations without having a relation of a controlling station and controlled stations,

wherein each communication station checks a state of time synchronization with a neighboring station, determines whether the time synchronization needs to be corrected, and carries out one of methods of surely performing a time synchronization correcting process and performing the correcting process with a predetermined probability when the time synchronization needs to be corrected.

2. A wireless communication system constructed by autonomous distributed operation of communication stations without having a relation of a controlling station and controlled stations,

wherein each communication station estimates a parameter indicating a difference in synchronization timing from a neighboring station, determines a communication station as a reference for time synchronization on a basis of the estimated parameter, and achieves time synchronization with the communication station as the reference.

3. The wireless communication system as claimed in claim 2,

wherein each communication station operates on a basis of time slots and exchanges predetermined packets with each neighboring station in a predetermined cycle including a number of time slots, estimates time slot start timing of each neighboring station with respect to time clock timing of the own station from a time of reception of a packet from the neighboring station, sets one of a communication station having most delayed time slot start timing and a communication station having most advanced time slot start timing within a certain time interval as the communication station as the reference for time synchronization, and synchronizes the time slots of the own station with the communication station as the reference for time synchronization.

4. The wireless communication system as claimed in claim 3,

wherein each communication station adds a flag indicating whether a beacon is transmitted at an intended time to beacon information;

and

a station side receiving the beacon refers to the flag and reduces frequency of synchronizing with incorrectly estimated time slots.

5. The wireless communication system as claimed in claim 2,

wherein when a state continues in which the own station cannot transmit a beacon at an intended time, and when a time synchronization deviation from the neighboring station is detected, even if time slot start timing of the own station is most delayed as compared with the neighboring station within a certain time interval, the own station is synchronized with time slot timing of an other station.

6. The wireless communication system as claimed in claim 5,

wherein when a time synchronization deviation is detected, a communication station performs a probabilistic process so as to prevent a steady pattern from occurring in timing of correction of time synchronization with the neighboring station.

7. The wireless communication system as claimed in claim 6,

wherein each communication station can operate in intermittent reception mode in which the communication station performs data reception for only a certain interval and performs only beacon transmission during other times;

and

an intermittently receiving communication station performs a time synchronization process earlier than a normal communication station in correction of time slot timing of the own station which correction is performed with a probability α

(0<

α

<

1), and a threshold value is provided for a time from detection of a time synchronization deviation to correction of time synchronization.

8. The wireless communication system as claimed in claim 2,

wherein when a time synchronization deviation continues, or when beacon transmission and reception at other than intended times continues, the communication station performs a time synchronization correction process with a predetermined probability.

9. A wireless communication apparatus operating in a wireless communication environment without a relation of a controlling station and controlled stations, said wireless communication apparatus comprising:

communication means for transmitting and receiving radio data;

communication control means for controlling operation of transmitting and receiving the radio data by said communication means;

time synchronization checking means for checking a state of time synchronization with a neighboring station; and

synchronization achieving means for determining whether the time synchronization needs to be corrected on a basis of a result of the checking by said time synchronization checking means, and carrying out one of methods of surely performing a time synchronization correcting process and performing the correcting process with a predetermined probability when the time synchronization needs to be corrected.

10. A wireless communication apparatus operating in a wireless communication environment without a relation of a controlling station and controlled stations, said wireless communication apparatus comprising:

communication means for transmitting and receiving radio data;

communication control means for controlling operation of transmitting and receiving the radio data by said communication means;

estimating means for estimating a parameter indicating a difference in synchronization timing from a neighboring station; and

synchronization achieving means for determining a communication station as a reference for time synchronization on a basis of the estimated parameter, and achieving time synchronization with the communication station as the reference.

11. The wireless communication apparatus as claimed in claim 10, further comprising:

beacon information generating means for generating predetermined beacon information; and

beacon information analyzing means for analyzing beacon information received from an other station;

wherein said communication control means operates on a basis of time slots and performs an operation of exchanging beacon information with each neighboring station in a predetermined cycle composed of a number of time slots;

said estimating means estimates time slot start timing of each neighboring station with respect to time clock timing of the own station from a time of reception of a beacon information from the neighboring station; and

said synchronization achieving means synchronizes the time slots of the own station with one of a communication station having most delayed time slot start timing and a communication station having most advanced time slot start timing within a certain time interval.

12. The wireless communication apparatus as claimed in claim 10,

wherein said beacon information generating means adds a flag indicating whether a beacon is transmitted at an intended time to beacon information;

and

one of said estimating means and said synchronization achieving means refers to a flag and reduces frequency of synchronizing with incorrectly estimated time slots.

13. The wireless communication apparatus as claimed in claim 10,

wherein when a state continues in which an own station cannot transmit a beacon at an intended time, and when a time synchronization deviation from the neighboring station is detected, even if time slot start timing of the own station is most delayed as compared with the neighboring station within a certain time interval, said synchronization achieving means synchronizes the own station with time slot timing of an other station.

14. The wireless communication apparatus as claimed in claim 13,

wherein when a time synchronization deviation is detected, said synchronization achieving means performs a probabilistic process so as to prevent a steady pattern from occurring in timing of correction of time synchronization with the neighboring station.

15. The wireless communication apparatus as claimed in claim 14,

wherein said communication control means can control operation in intermittent reception mode in which data reception is performed for only a certain interval and only beacon transmission is performed during other times;

and

said synchronization achieving means operates such that an intermittently receiving communication station performs a time synchronization process earlier than a normal communication station in correction of time slot timing of the own station which correction is performed with a probability α

(0<

α

<

1), and provides a threshold value for a time from detection of a time synchronization deviation to correction of time synchronization.

16. The wireless communication apparatus as claimed in claim 10,

wherein when a time synchronization deviation continues, or when beacon transmission and reception at other than intended times continues, said synchronization achieving means performs a time synchronization correction process with a predetermined probability.

17. A wireless communication method for operating in a wireless communication environment without a relation of a controlling station and controlled stations, said wireless communication method comprising:

a time synchronization checking step for checking a state of time synchronization with a neighboring station; and

a synchronization achieving step for determining whether the time synchronization needs to be corrected on a basis of a result of the checking in said time synchronization checking step, and carrying out one of methods of surely performing a time synchronization correcting process and performing the correcting process with a predetermined probability when the time synchronization needs to be corrected.

18. A wireless communication method for operating in a wireless communication environment without a relation of a controlling station and controlled stations, said wireless communication method comprising:

an estimating step for estimating a parameter indicating a difference in synchronization timing from a neighboring station; and

a synchronization achieving step for determining a communication station as a reference for time synchronization on a basis of the estimated parameter, and achieving time synchronization with the communication station as the reference.

19. A computer program described in a computer readable form so as to perform a process on a computer system for operating in a wireless communication environment without a relation of a controlling station and controlled stations, said computer program comprising:

an estimating step for estimating a parameter indicating a difference in synchronization timing from a neighboring station; and

a synchronization achieving step for determining a communication station as a reference for time synchronization on a basis of the estimated parameter, and achieving time synchronization with the communication station as the reference.