Communication system, communication apparatus, and communication method
First Claim
1. A communication system comprising first and second communication devices,, wherein said first and second communication devices comprise:
- modulating means for sending data at one of a plurality of transfer rates by modulating an electromagnetic wave;
demodulating means for obtaining data sent from another device at one of the plurality of transfer rates by demodulating the electromagnetic wave; and
detecting means for detecting the electromagnetic wave, and wherein said first communication device starts to output the electromagnetic wave when said detecting means does not detect the electromagnetic wave at the level of a first threshold or more, and said second communication device requires the electromagnetic wave at the level of a second threshold higher than said first threshold so that said demodulating means obtains the data.
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Abstract
The present invention relates to a communication system, a communication device, and a communication method for easily solving a problem of a hidden terminal. Communication devices 1 and 3 determine whether or not an electromagnetic wave at the level of a magnetic-flux density TH1 or more for determining the suppression of the output of carrier. When the electromagnetic wave at the level of the magnetic-flux density TH1 or more for determining the suppression of the output of the carrier is not detected, the communication devices 1 and 3 start the output of the electromagnetic wave. A communication device 2 needs the electromagnetic wave at the level of a magnetic-flux density TH2 or more of the carrier at an operating limit, which is higher than the magnetic-flux density TH1 for determining suppression of the output of carrier so as to obtain data via the electromagnetic wave. The present invention is applied to, e.g., an IC (Integrated Circuit) card system.
53 Citations
12 Claims
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1. A communication system comprising first and second communication devices,,
wherein said first and second communication devices comprise: -
modulating means for sending data at one of a plurality of transfer rates by modulating an electromagnetic wave;
demodulating means for obtaining data sent from another device at one of the plurality of transfer rates by demodulating the electromagnetic wave; and
detecting means for detecting the electromagnetic wave, and wherein said first communication device starts to output the electromagnetic wave when said detecting means does not detect the electromagnetic wave at the level of a first threshold or more, and said second communication device requires the electromagnetic wave at the level of a second threshold higher than said first threshold so that said demodulating means obtains the data. - View Dependent Claims (2, 3, 4, 5)
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6. A communication device for receiving and sending data by modulating and demodulating an electromagnetic wave, comprising:
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electromagnetic-wave generating means for generating an RF (Radio Frequency) field by generating the electromagnetic wave;
modulating means for sending the data at any of a plurality of transfer rates by modulating the electromagnetic wave;
demodulating means for obtaining the data sent from another device at any of a plurality of transfer rates by demodulating the electromagnetic wave; and
detecting means for detecting the electromagnetic wave, wherein the output of the electromagnetic wave starts when said detecting means does not detect the electromagnetic wave at the level of a first threshold or more, and the data is communicated with said other device at the position where the electromagnetic wave reaches at the level of a second threshold or more that is higher than said first threshold.
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7. A communication method for receiving and sending data by modulating and demodulating an electromagnetic wave, comprising:
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an electromagnetic-wave generating step of generating an RF (Radio Frequency) field by generating the electromagnetic wave;
a modulating step of sending the data by any of a plurality of transfer rates by modulating the electromagnetic wave;
a demodulating step of obtaining the data sent from another device by any of a plurality of transfer rates by demodulating the electromagnetic wave; and
a detecting step of detecting the electromagnetic wave, wherein the output of the electromagnetic wave starts when said detecting step does not detect the electromagnetic wave at the level of a first threshold or more, and the data is communicated with said other device at the position where the electromagnetic wave reaches at the level of a second threshold or more that is higher than said first threshold.
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8. A communication device for receiving and sending data by modulating and demodulating an electromagnetic wave, comprising:
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modulating means for sending data by one of a plurality of transfer rates by modulating the electromagnetic wave; and
demodulating means for obtaining data sent from another device at one of the plurality of transfer rates by modulating the electromagnetic wave;
wherein when said other device checks that the electromagnetic wave at the level of a first threshold does not exist and starts to output the electromagnetic wave, the acquisition of data by said demodulating means requires the electromagnetic wave at the level of a second threshold higher than said first threshold or more. - View Dependent Claims (9, 10, 11)
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12. A communication method for receiving and sending data by modulating and demodulating an electromagnetic wave, comprising:
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a modulating step of sending data at one of a plurality of transfer rates by modulating the electromagnetic wave; and
a demodulating step of obtaining the data sent from another device at one of the plurality of transfer rates by demodulating the electromagnetic wave, wherein when said-other device checks that the electromagnetic wave at the level of a first threshold or more does not exist and the output of the electromagnetic wave starts, the data acquisition in said demodulating step requires the electromagnetic wave at the level of a second threshold or more higher than said first threshold.
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Specification