Pulse or digital communications – Spread spectrum – Frequency hopping
Reexamination Certificate
1997-03-19
2001-08-14
Zimmerman, Brian (Department: 2635)
Pulse or digital communications
Spread spectrum
Frequency hopping
C340S870030, C370S350000
Reexamination Certificate
active
06275517
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to frequency changeover when performing wireless communication using frequency hopping.
In a wireless communication system performing wireless communication using frequency hopping, an originating terminal and a destination terminal change to the same frequency for communication by using the following two methods. In the first method, the originating terminal transmits information on the frequency to be used in the next communication frame and information on when to change (i.e., information on a frequency to be “hopped” and the changeover time when changing to that frequency) in each communication frame, then the destination terminal changes the frequency in accordance with the received information. In the second method, the originating terminal and the destination terminal store an identical hopping pattern, synchronize to each other, then change the frequencies at the same timing.
In the first method, however, their information in each communication frame is not always received without an error. If an error occurs in the information of the received communication frame, the destination station can not obtain information on the frequency to be used and information on time of changing the frequency, thereby the destination terminal can not follow frequency changeover thereafter.
In the second method, the originating terminal and the destination terminal store the identical hopping pattern and synchronize timing to change frequencies by synchronizing to each other. If any frequency or frequencies used in the hopping pattern become useless because of noises, for example, it is not impossible to replace the useless frequencies. Accordingly, there are problems in which it may become even impossible to communicate depending upon the number of useless frequencies, and substantial drop in transmission rate because the number of times for resending information which were not communicated increases.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to definitely perform frequency changeover in frequency hopping.
Further, it is another object of the present invention to make it possible to change frequency even in a case where an error occurred in control information transmitted from an originating station.
Furthermore, it is still another object of the present invention to prevent the transmission rate from falling in a case where a frequency or frequencies are replaced during communication.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
REFERENCES:
patent: 4850036 (1989-07-01), Smith
patent: 5442659 (1995-08-01), Bauchot et al.
patent: 5541954 (1996-07-01), Emi
patent: 5581548 (1996-12-01), Ugland et al.
patent: 5640415 (1997-06-01), Pandula
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Zimmerman Brian
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