JP2010171881A - Communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively perform carrier sensing in a communication apparatus through any of a plurality of existing channels. <P>SOLUTION: The communication apparatus has a narrow-band carrier sensing unit to detect a receiving strength in a frequency corresponding to an arbitrary desired channel; a wide-band carrier sensing unit to detect the receiving strength in all bands of the existing channels; a means for giving approval to transmission through a desired channel, when the receiving strength detected by the wide-band carrier sensing unit exceeds no predetermined level in all the bands of the existing channels; and a means for giving approval to transmission through the desired channel, if the receiving strength exceeds no predetermined level in the frequency corresponding to the desired channel detected by the narrow-band carrier sensing unit, when the receiving strength detected by the wide-band carrier sensing unit exceeds the predetermined level in all the bands. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a communication apparatus that performs communication using any one of a plurality of predetermined channels, such as communication with an IC tag in an RFID system, for example, in order to avoid a communication collision in the same channel. The present invention relates to a communication device having a talk (LBT) function.

  In an RFID system, when a modulated or non-modulated radio wave is transmitted from a reader / writer as a communication device and the IC tag receives the radio wave, an electromotive force is generated in the IC tag, and data from the IC tag is generated by the electromotive force. It is transmitted as a response signal, and the response signal is received by the reader / writer.

  For example, in the Japanese Radio Law, a frequency of 950 to 956 MHz is assigned to UHF band RFID, and is a predetermined channel of 200 channels at intervals of 200 KHz, 14 channels for low output and 9 channels for large output. Are prepared, and this common channel is used by a plurality of communication devices in a time-sharing manner.

  In order to avoid communication collisions due to the use of the same channel in an environment where such a plurality of communication devices are used, a listen before talk function is incorporated into the communication device, and carrier sense is performed before using a desired channel. Is required.

  As a carrier sense circuit of this communication apparatus, there is one proposed in Patent Documents 1 to 4.

  In Patent Document 1, in the RFID transceiver device that demodulates the received signal using the frequency of the local oscillation signal of the set frequency, the local oscillation signal of the reference frequency is output during normal communication, and at the time of carrier sense, A local oscillation signal having a frequency shifted by a predetermined frequency with respect to the reference frequency is output.

  In Patent Document 2, when performing carrier sense, the frequency of the high-frequency signal of the local oscillator is shifted by Δf from the reception frequency, and the carrier is determined by the amplitude of the received high-frequency signal and the beat frequency Δf generated by the high-frequency signal generated from the local oscillator. I have a sense.

  In Patent Document 3, a local signal having a frequency different from that of the received RF signal is generated, the received RF signal and the local signal are mixed, and the frequency of the difference between the received RF signal and the local signal is passed through the bandpass filter.

  In Patent Document 4, a local signal of a local oscillator is modulated, and carrier sense is performed by an output of a receiver obtained by modulating the local signal.

JP 2006-295287 A JP 2007-28583 A JP 2008-85669 A Japanese Patent Laid-Open No. 2-100521

  As described above, according to the conventional proposal, carrier sense can be performed even for modulated or non-modulated radio waves. When it can be determined that there is a received signal based on the strength of the received signal, the channel is changed and carrier sense is performed again.

  An object of the present invention is to provide a communication apparatus capable of performing carrier sense processing more efficiently.

In order to achieve the above object, the present invention is a communication device that performs communication using any one of predetermined channels.
A narrowband carrier sense unit for detecting the reception intensity at a frequency corresponding to an arbitrary desired channel;
A broadband carrier sense unit for detecting reception intensity in the entire band of the predetermined all channels;
Means for permitting communication using a desired channel when the reception intensity detected by the broadband carrier sense unit does not exceed a threshold level over the entire band;
When the reception intensity detected by the broadband carrier sense unit exceeds the threshold level in the entire band, the reception intensity at the frequency corresponding to the desired channel detected by the narrow band carrier sense unit is the threshold value. Means for permitting communication using the desired channel when the level is not exceeded;
It is characterized by providing.

  The invention according to claim 2 is the one according to claim 1, wherein when the reception intensity at a frequency corresponding to a desired channel detected by the narrowband carrier sense unit exceeds a threshold level, the threshold level is exceeded. It is further characterized by further comprising means for changing a channel whose reception strength is detected by the narrowband carrier sense unit until a desired channel having a low reception strength is found.

The invention according to claim 3 is a communication device that performs communication using any one of a predetermined plurality of channels,
A broadband carrier sense unit for detecting reception intensity in the entire band of the predetermined all channels;
A first means for permitting communication using a desired channel when the reception intensity detected by the broadband carrier sense unit does not exceed a threshold level over the entire band;
A narrowband carrier sense unit for detecting the reception intensity at a frequency corresponding to an arbitrary desired channel;
Second means for permitting communication using the desired channel when the reception intensity at the frequency corresponding to the desired channel detected by the narrowband carrier sense unit does not exceed a threshold level;
And switching between one of the first means and the second means, or one of the wideband carrier sense unit and the first means, the narrowband carrier sense unit, and the second means. Features.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, when the reception intensity at a frequency corresponding to a desired channel detected by the narrowband carrier sense unit exceeds a threshold level, the threshold level is exceeded. It is further characterized by further comprising means for changing a channel whose reception strength is detected by the narrowband carrier sense unit until a desired channel having a low reception strength is found.

The invention according to claim 5 is a communication device that performs communication using any one of predetermined channels.
A broadband carrier sense unit for detecting reception intensity in the entire band of the predetermined all channels;
Means for permitting communication using a desired channel when the reception intensity detected by the broadband carrier sense unit does not exceed a threshold level over the entire band;
Means for disallowing communication when the received intensity detected by the broadband carrier sense unit exceeds a threshold level in the entire band;
It is characterized by providing.

The invention according to claim 6 is a communication device that performs communication using any one of predetermined channels.
A carrier sense unit for detecting the reception intensity in the vicinity of the center frequency of any desired channel;
Storage means for storing a change in the received intensity with respect to the frequency in the vicinity of the center frequency of the channel when a channel is not used and a channel adjacent to the channel is used;
Means for permitting communication using a desired channel when the reception intensity at the center frequency of the desired channel detected by the carrier sense unit does not exceed a threshold level;
When the reception intensity at the center frequency of the desired channel detected by the carrier sense unit exceeds the threshold level and is equal to or lower than the second threshold level, the reception intensity near the center frequency of the desired channel detected by the carrier sense unit The change tendency with respect to the frequency of the received intensity in the vicinity of the center frequency of the desired channel detected by the carrier sense unit is compared with the change tendency with respect to the frequency and the corresponding change tendency stored in the storage means is stored in the storage means. Determining whether or not it matches the trend, and when determining that it matches, means for permitting communication using the desired channel;
It is characterized by providing.

The invention according to claim 7 is a communication device that performs communication using any one of a predetermined plurality of channels,
A carrier sense unit for detecting a beat signal between a received signal in a frequency region of any desired channel and at least a part of a frequency region of a channel adjacent thereto and a signal shifted by Δf from the center frequency of the desired channel; ,
Means for detecting the temporal change from the envelope of the beat signal;
Means for permitting communication using a desired channel when it is detected by the means for detecting the change that there is no temporal change in the envelope of the beat signal;
Means for determining whether a time change of the envelope of the beat signal follows a period of 1 / Δf;
Means for disabling communication using a desired channel when the time change of the envelope of the beat signal follows the period of 1 / Δf by the means for determining;
Means for determining whether the time change of the envelope of the beat signal regularly follows a period of 1 / (2Δf);
Means for permitting communication using a desired channel when the time variation of the envelope of the beat signal regularly follows the period of 1 / (2Δf) by the determining means;
Means for disallowing communication using a desired channel when the time change of the envelope of the beat signal does not regularly follow the period of 1 / (2Δf) by the determining means;
It is characterized by providing.

  According to the first and second aspects of the present invention, the wideband carrier sense unit and the narrowband carrier sense unit are provided, and the reception intensity detected by the wideband carrier sense unit does not exceed the threshold level over the entire band. In this case, since it can be determined that none of the predetermined plurality of channels is used, the desired channel of the plurality of predetermined channels is used regardless of the detection result by the narrowband carrier sense unit. Communication is possible. Thereby, the processing for carrier sense can be made efficient.

  According to the third to fourth aspects of the present invention, either the first means or the second means, or any one of the broadband carrier sense unit and the first means and the narrow band carrier sense unit and the second means is switched. Thus, efficient carrier sense according to the situation can be performed.

  According to the fifth aspect of the present invention, when the reception intensity detected by the broadband carrier sense unit does not exceed the threshold level over the entire band, none of the predetermined plurality of channels is used. Since it can be determined, carrier sense for each channel can be made unnecessary. Thereby, the processing for carrier sense can be made efficient.

  According to the sixth aspect of the present invention, the adjacent channel is used even though the desired channel is not used by another communication apparatus, and the center frequency of the desired channel exceeds the threshold level due to the influence of the adjacent channel. Therefore, it is possible that the use of the desired channel is possible. Therefore, the frequency change tendency of the reception intensity in the vicinity of the center frequency of the desired channel in a state where the adjacent channel is used is previously determined. When the center frequency of the desired channel does not exceed the second threshold level and the change tendency matches, the communication using the desired channel is permitted, The probability of using a channel can be increased, and the accuracy and efficiency of carrier sense can be increased.

  According to the seventh aspect of the present invention, when a desired channel is not used by another communication apparatus but an adjacent channel is used, there is a possibility that the desired channel can be used. From the tendency of the beat signal with the signal shifted by Δf from the center frequency of the desired channel, it is determined whether the desired channel is used or only the adjacent channel is used, and only the adjacent channel is used. In some cases, by allowing communication using a desired channel, the probability of using the desired channel can be increased, and the accuracy and efficiency of carrier sense can be increased.

1 is an overall block diagram of a communication apparatus according to the present invention. 1 is a block circuit diagram illustrating a first embodiment of a communication device according to the present invention. It is a spectrum figure showing the relationship of the receiving intensity between adjacent channels when the channel which performs a carrier sense in a narrow band carrier sense part is channel 5. It is a timing chart of the carrier sense by a narrow band carrier sense part. It is a timing chart of the carrier sense by a broadband carrier sense part. It is a flowchart showing the suitable procedure in the case of using it combining a narrow band carrier sense part and a wide band carrier sense part. It is a block diagram concerning other embodiments of the present invention. It is a flowchart showing the process of the signal processing and control part which concerns on another embodiment of this invention. It is a spectrum figure explaining the principle which concerns on embodiment of FIG. It is a flowchart showing the process of the signal processing and control part which concerns on another embodiment of this invention. It is a wave form diagram explaining the principle which concerns on embodiment of FIG. It is a wave form diagram explaining the principle which concerns on embodiment of FIG. It is a wave form diagram explaining the principle which concerns on embodiment of FIG. It is a modification of the flowchart of FIG.

Hereinafter, the present invention will be described with reference to the drawings.
1 and 2 are block diagrams showing a communication apparatus according to the present invention. In this example, the direct conversion method is adopted.

  As shown in FIG. 1, the communication apparatus includes a signal processing / control unit 10, a transmission unit 12, an antenna unit 14, a reception unit 16, a narrowband carrier sense unit 18, a wideband carrier sense unit 20, and a listen device. And a switching unit 22 that switches between a before talk (LBT) function and a normal reception function.

  The signal processing / control unit 10 can include a logic circuit 102 and a CPU 104. The logic circuit 102 can be configured as software in addition to an integrated circuit.

  Based on the control signal from the signal processing / control unit 10, the transmission unit 12 generates a frequency synthesizer 122 as a high frequency generation source that generates a high frequency signal of a designated frequency, and a modulation signal from the signal processing / control unit 10. Based on this, a modulator 124 that performs modulation, a band-pass filter 126, a power amplifier 128, and a low-pass filter 130 are provided.

  The antenna unit 14 includes a circulator 142 that switches between transmission and reception, and an antenna 144.

  The receiving unit 16 includes an IQ demodulator 162 that performs demodulation using the high-frequency signal from the frequency synthesizer 122 as a local signal, a low-pass filter 164, and a low-frequency amplifier 166.

  The narrowband carrier sense unit 18 that performs the LBT function includes an IQ demodulator 162, a bandpass filter 182, an amplifier 184, and a peak detector 186, and shares the receiving unit 16 and the IQ demodulator 162. Yes. As the band-pass filter 182, an active filter or a passive filter composed of an LC circuit can be used. An active filter is suitable for semiconductorization.

  The broadband carrier sense unit 20 that performs the LBT function includes a band pass filter 202, a low noise amplifier 204, and an RF detector 206. As the band pass filter 202, a SAW filter or a dielectric filter can be used.

  The switching unit 22 includes a first switch 222 and a second switch 228. During normal reception, the first switch 222 and the second switch 228 shown in FIG. 2 are switched to the upper contacts, and when the LBT function is executed, the first switch 222 and the second switch 228 are switched to the lower contacts.

(Narrow-band carrier sense operation)
Hereinafter, the operation of the narrowband carrier sense unit 18 will be described.
It is assumed that a desired channel for performing carrier sense determined by the signal processing / control unit 10 is CHN. In response to the control signal from the logic circuit 102, the frequency synthesizer 122 outputs a signal having a frequency of Fchn + Δf (or Fchn−Δf) in which the frequency is shifted by Δf with respect to the center frequency Fchn of the desired channel. The demodulator 162 demodulates. Assuming that the channel CHN is in use, a beat signal having a frequency Δf is output from the band pass filter 182. This signal is amplified, the peak is detected by the peak detector 186, and converted to a DC signal corresponding to the received intensity. If the DC signal is above a predetermined level, it is determined that the channel CHN is being used.

  FIG. 3 is a spectrum diagram showing the relationship of the reception intensity between the channel 5 and the adjacent channels 4 and 6 when the threshold level of the reception intensity is −64 dBm.

  The solid line represents an unmodulated wave, and the alternate long and short dash line represents a modulated wave. Although the channel 5 itself is not used, the influence of the adjacent channel is large (for example, the modulation wave of the adjacent channel), and if the threshold level is exceeded at the center frequency F5 of the channel 5 (case (1) in FIG. 3), the channel Communication with 5 is not possible. Of course, even if the adjacent channel is not used, if the channel 5 itself is used (case (2) in FIG. 3), communication on the channel 5 is not possible.

  On the other hand, the channel 5 itself is not used, the influence of the adjacent channel is small (for example, the adjacent channel is a non-modulated wave), and the threshold level is not exceeded at the center frequency F5 of the channel 5 ((( Case 3), communication on channel 5 is possible. If the adjacent channel is not used and the channel 5 itself is used but the distance is long and the reception strength is low (case (4) in FIG. 3), the communication on the channel 5 is It becomes possible.

  FIG. 4 is a timing chart of carrier sense by the narrowband carrier sense unit 18. The communication device transmits for 1 second and stops for at least 100 milliseconds. While communication device A is communicating using channel 5 (center frequency F5), if communication device B performs channel 5 carrier sense for 10 milliseconds, it is determined that communication on channel 5 is not possible. The After a certain period of time, when communication device B performs carrier sense of channel 5 again while communication device A is not communicating, communication using channel 5 is permitted.

  If communication device A performs carrier sense on channel 6 while communication device B is communicating, channel 6 is free, so communication on channel 6 is permitted.

  When switching from carrier sensing to normal communication, switching by the switching unit 22 is performed, and a control signal from the signal processing / control unit 10 is also switched. In the carrier sense, a local signal of frequency F5 ± Δf is output from the frequency synthesizer 122 to the IQ modulator 162, whereas in the normal communication, the frequency synthesizer 122 outputs a frequency signal from the frequency synthesizer 122 to the IQ modulator 162. Control is performed so that a local signal of F5 is output. As a result, the narrow band carrier sense unit 18 and the receiving unit 16 can share the same IQ demodulator 162.

(Broadband carrier sense operation)
Next, the operation of the broadband carrier sense unit 20 will be described.
The high frequency signal received by the antenna 144 is filtered by the band pass filter 202. The pass band of the band pass filter 202 corresponds to the entire band of all channels (for example, 950 to 956 MHz). The amplifier 204 amplifies the signal that has passed through the bandpass filter 202, and the RF detector 206 converts it into a DC signal. If the DC signal corresponding to the received intensity is equal to or higher than a predetermined level, it is determined that one of the channels is being used.

  FIG. 5 is a timing chart of carrier sense by the broadband carrier sense unit 20. If communication device B performs carrier sense while communication device A is performing communication using channel 4 (center frequency F4), communication device B is performing communication. Is determined to be unable to communicate. After a certain period of time, if communication device B performs carrier sense again while communication device A is not communicating, since no communication device is communicating, communication using channel 5 of communication device B is permitted. Become. If communication device A performs carrier sense while communication device B is communicating, it is determined that communication device A cannot communicate.

  In carrier sense by the broadband carrier sense unit 20, if any communication apparatus uses any channel, other communication apparatuses cannot be used. If the number of communication devices is small, the broadband carrier sense unit 20 alone is sufficient, thereby simplifying the circuit configuration.

(Narrowband carrier sense and wideband carrier sense)
As described above, in the communication apparatus including both the narrow band carrier sense unit 18 and the wide band carrier sense unit 20, the narrow band carrier sense and the wide band carrier sense are selectively switched or used. It becomes possible to use a combination of carrier senses. Hereinafter, various forms will be described.

(1) Form in which narrowband carrier sense and wideband carrier sense are used in combination A preferred procedure of a form in which narrowband carrier sense and wideband carrier sense are used in combination will be described with reference to the flowchart of FIG.

  First, the DC signal from the peak detector 186 that has undergone the processing by the broadband carrier sense unit 20 (step S12) is compared with a predetermined level, and it is determined whether or not the reception intensity is −64 dBm or less (step S14). In this determination, if the reception strength is −64 dBm or less, the narrowband carrier sense is omitted, the channel is determined, and transmission is started (step S30). Here, the processes in steps S14 and S30 function as a means for permitting communication.

  If it is determined in step S14 that the reception intensity exceeds -64 dBm, it means that another communication apparatus is communicating. Therefore, a desired channel on which carrier sense is to be performed is determined and a narrowband carrier is determined. The DC signal from the peak detector 186 that has undergone the processing by the sensing unit 18 (step S16) is compared with a predetermined level, and it is determined whether or not the reception intensity is −64 dBm or less (step S18). If the received intensity exceeds -64 dBm, the channel is in use, so the desired channel is changed to another channel (step S22), and processing by the narrowband carrier sense unit 18 is performed. If it is −64 dBm or less, narrowband carrier sensing is repeated until a predetermined time of 10 ms elapses (step S20), and then backoff time and narrowband carrier sensing are performed again (steps S24 to S28). The back-off time is set to a random time, thereby preventing a collision with another communication device that is simultaneously performing carrier sense of the same channel.

  When the determination in S28 is Yes, the desired channel transmission is performed for 1 second (steps S30 and 32), and is stopped for 100 ms or longer (step S34).

  Here, the processes of steps S18, S20, S26, S28, and S30 function as a means for permitting communication. Step S22 functions as a means for changing the channel.

  In this way, carrier sense efficiency can be improved by combining wideband carrier sense with priority and narrowband carrier sense. Instead of changing the desired channel to another channel in step S22, the desired channel may be fixed and the narrowband carrier sense in steps 16 to 20 may be repeated after a predetermined time has elapsed.

(2) When switching between narrowband carrier sense and wideband carrier sense, the signal processing / control unit 10 can selectively capture signals from the narrowband carrier sense unit 18 and the wideband carrier sense unit 20. Switching between the band carrier sense and the broadband carrier sense is performed, and the switching means can be realized by software.

  In this case, when narrowband carrier sense is selected, steps S16 to S28 of FIG. 6 are performed, and the processes of steps S18, S20, S26, S28, and S30 function as a means for permitting communication. Step S22 functions as a means for changing the channel. When broadband carrier sense is selected, steps S12 to S14 in FIG. 6 are performed, and the processes in steps S14 and S30 function as a means for permitting communication.

  Alternatively, by separately providing a switch (functioning as a switching means) for switching between the narrowband carrier sense unit 18 and the wideband carrier sense unit 20, switching between the narrowband carrier sense and the wideband carrier sense is performed. In addition to realizing the switching means, the signal processing / control unit 10 can also realize the switching means in software.

  By such switching means, switching can be performed according to the situation in which the communication device is used. For example, in a situation where there are not a large number of communication devices, there is a high possibility that there is an idle time during which no communication device is communicating, so that only the detection by the broadband carrier sense unit 20 is sufficient. On the other hand, in a situation where there are a large number of communication devices and any one of the communication devices is expected to be communicating at all times, the detection by the narrowband carrier sense unit 18 is sufficient.

  Thus, by switching between wideband carrier sense and narrowband carrier sense according to the situation, efficient carrier sense according to the situation can be performed.

(3) Mode in which only wideband carrier sense is performed Depending on the predicted situation, it is possible to adopt a configuration in which the narrowband carrier sense unit 18 itself is deleted in the communication device. In this case, the signal processing / control unit 10 performs steps S12 to S14 in FIG. 6, and the processing in steps S14 and S30 functions as a means for permitting communication.
This eliminates the need for carrier sensing for individual channels, and makes it possible to improve the efficiency of carrier sensing processing.

(Other embodiments)
FIG. 7 is a block circuit diagram according to another embodiment of the present invention. In this embodiment, a digital filter 168 is used instead of the low-pass filter 164 of the receiving unit 16 in the embodiment of FIG. 2, and the cut-off frequency can be changed by a control signal from the signal processing / control unit 10. Then, instead of providing the band pass filter 182 and the amplifier 184 of the narrow band carrier sense unit 18, the digital filter 168 and the amplifier 166 of the receiving unit 16 are commonly used.

  When narrowband carrier sensing is performed, the digital filter 168 is switched to a pass band that allows Δf to pass, and is switched to a pass band that allows a baseband signal to pass during reception. Thus, the narrow band carrier sense unit 18 and the receiving unit 16 can share one more circuit component.

(Other embodiment 2)
FIG. 8 is a flowchart showing the processing of the signal processing / control unit 10 according to still another embodiment of the present invention, and FIG. 9 is a spectrum diagram showing the principle according to still another embodiment of the present invention. is there. In this embodiment, the circuit configuration diagram of FIG. 2 or preferably FIG. 7 can be used.

  When interference waves of adjacent channels (channels 4 and 6) of a desired channel (channel 5 in FIG. 9) in which carrier sense is performed exist, interference of the adjacent channel is not used even though the desired channel is not used. Under the influence of the wave, the reception intensity at the center frequency of the desired channel may exceed the threshold level (−64 dBm) and may be determined to be unusable.

  However, if there is an S / I (Signal / Interference) ratio of about 10 to 15 dB even if there is an interference wave of an adjacent channel, it is possible to receive up to about -50 dBm of reception strength, so use a desired channel. It is thought that you can.

  Therefore, when the desired channel is not used and is affected by the interference wave of the adjacent channel, the change tendency of the reception intensity near the center frequency of the desired channel is stored in advance, and this stored change tendency is In this comparison, a situation in which the desired channel is not used and only the adjacent channel is used is identified.

  The reception intensity in the vicinity of the center frequency of the desired channel is such that the local signal from the frequency synthesizer 122 is continuous within a range of ± Δf (for example, ± 50 kHz) with respect to the center frequency Fchn of the desired channel in the narrowband carrier sense unit 18. The DC signal from the peak detector 186 shown in FIG. 7 or FIG. 2 is taken in and A / D converted to obtain the DC signal. Alternatively, the amount of change and the differential value can be acquired by taking a deviation from adjacent data in the acquired data.

  Data of an average change tendency in the vicinity of the center frequency ± Δf when a certain channel is not used and only an adjacent channel is used is acquired in advance. As shown in FIG. 9B, when only channel 4 is used, it is considered that the change within ± Δf is monotonously decreased. Also, as shown in FIG. 9C, when only channel 6 is used, it is considered that the change within ± Δf is monotonically increasing. Further, as shown in FIG. 9 (d), data of an average change tendency when both two adjacent channels exist is also acquired. In this case, the change within ± Δf is considered to increase monotonically after decreasing monotonously.

  The data of the above change tendency can be, for example, the amount of change, the differential value (change rate), the number of extreme values, or “monotonically increasing”, “monotonically decreasing”, “monotonically increasing after monotonically decreasing” It can also be set as such data. Any of these change tendency data is stored in a memory as a storage means.

  When performing carrier sense, the narrowband carrier sense unit 18 continuously changes the local signal from the frequency synthesizer 122 within a range of ± Δf (for example, ± 50 kHz) with respect to the center frequency Fchn of the desired channel. The DC signal from the peak detector 186 is taken in, A / D converted, and data of the change tendency at the time of carrier sense is acquired (S102).

  Then, it is determined whether the reception sensitivity at the center frequency Fchn of the desired channel exceeds a predetermined threshold level (for example, −64 dBm) (S104). If not, communication using the desired channel is permitted (S104, S120 to S124).

  If the reception sensitivity exceeds a predetermined threshold level, it is determined whether it exceeds a second predetermined threshold level (for example, −50 dBm) (S106).

  If the reception intensity exceeds the second predetermined threshold level, the desired channel is changed to another channel (S108), and the processing of the narrowband carrier sense unit 18 (S102) is performed. If not exceeded, the change tendency data at the time of carrier sense is compared with the change tendency data stored in the memory (S110).

  If the change tendency data at the time of carrier sense matches the change tendency data when only the adjacent channel stored in the memory exists, it is determined that the desired carrier is not used, and the desired Communication using the channel is permitted (S110, S120 to S124).

  On the other hand, if communication on a desired channel (dotted line in FIG. 9A) is superimposed in a state where an adjacent channel exists, a change appears in the change tendency. As shown in FIGS. 9E and 9F, two extreme values appear near the center frequency F5 (= 953 MHz), or three or more extreme values appear as shown in FIG. 9G. . Therefore, if the data of the change tendency at the time of carrier sense does not coincide with the data of the change tendency when only the adjacent channel stored in the memory exists, it is determined that the desired channel is used, The desired carrier is changed to another channel (S108).

  Through the above processing, the probability of using a desired channel can be increased, and the accuracy of carrier sense can be increased.

(Other embodiment 3)
FIG. 10 is a flowchart showing processing of the signal processing / control unit 10 according to still another embodiment of the present invention. In this embodiment, the circuit configuration diagram of FIG. 2 or preferably FIG. 7 can be used.

  In this embodiment, the filter band of the digital filter 168 in FIG. 7 (or the band-pass filter 182 in FIG. 2) can be a wide band, rather than a band that sharply attenuates, and / or corresponds to the desired channel. In addition to whether or not transmission using a frequency is possible, when a response frequency from a communication partner such as an IC tag is applied to an adjacent channel, communication using a desired channel is performed in consideration of the influence of an interference wave in the adjacent channel. It can be determined whether or not it is permitted.

  FIGS. 11 to 13 show beat signals after passing through a filter having a wide band when there is a carrier only in the adjacent channel and there is no carrier in the desired channel and when there are carriers in both the adjacent channel and the desired channel. Represents a waveform.

  FIG. 11A and FIG. 12A show a case where there is a carrier only in the adjacent channel. In this case, only the beat signal from the carrier of the high-frequency adjacent channel appears, whereas FIG. ) And FIG. 12B show a case where there is a carrier in both the adjacent channel and the desired channel, and a beat signal by the carrier of the desired channel of the low frequency of Δf is superimposed on the beat signal by the carrier of the high frequency adjacent channel. appear. In the example of FIG. 12, the intensity of the beat signal by the carrier of the adjacent channel is higher than that of FIG. 11, but the tendency itself is the same regardless of the magnitude of the beat signal.

  On the other hand, FIG. 13A shows a case where there is a carrier in the adjacent channel on both sides and no carrier in the desired channel. In this case, in addition to the beat signal by the carrier of the adjacent channel on both sides, A 2 × Δf low-frequency beat signal based on the difference between carriers appears superimposed. FIG. 13B shows a case where there are carriers in both the adjacent channel and the desired channel on both sides. In this case, since a low-frequency beat signal of Δf is further superimposed, irregular amplitude changes Appears.

  Based on the above tendency, the signal processing / control unit 10 determines whether or not the desired channel can be used according to the condition of the adjacent channel. First, the signal processing / control unit 10 determines a desired channel on which carrier sense is to be performed. After processing by the band carrier sense unit 18, time-series data obtained by A / D converting the DC signal from the peak detector 186 that detects the envelope of the beat signal is captured (S202), and the received intensity of the data is a predetermined threshold value. It is determined whether the level (for example, −64 dBm) is exceeded (S204). If not, communication using the desired channel is permitted (S204, S220 to S224).

If the reception sensitivity of the time series data exceeds a predetermined threshold level, it is determined whether it exceeds a second predetermined threshold level (for example, −50 dBm) (S206).
If the time-series data exceeds the second predetermined threshold level, it is determined that the reception strength of either the adjacent channel or the desired channel is high, and the desired channel is changed to another channel (S208), and the narrowband carrier Processing of the sensing unit 18 (S202) is performed. However, the determination in S206 can be arbitrarily omitted. In the situation where communication is possible when a desired channel is not used even if an interference signal from an adjacent channel exists, the second is performed. Even if the predetermined threshold level is exceeded, if it can be determined that the desired channel is not being used by the following processing, communication may be permitted.

  Next, it is determined whether the change of the time series data is within a predetermined range (S210). When the change of the time series data is within a predetermined range, in other words, when there is no change of the time series data and the reception intensity is almost constant (for example, FIG. 11A), the desired channel is used. It is determined that it is not, and communication using the desired channel is permitted (S210, S220 to S224). Here, the predetermined range is an allowable range that can be regarded as constant.

  On the other hand, when the change of the time series data is not within the predetermined range, in other words, when the time series data fluctuates, it is determined whether or not the change of the period of 1 / Δf is performed (S212).

  If the time-series data has a period change of 1 / Δf, it means that the desired channel is used, and therefore the desired channel is changed to another channel (S208).

  On the other hand, if the time-series data has not changed the period of 1 / Δf, the period of 1 / (2Δf) has further changed from the change of the time-series data and whether the period is regular or not. Is determined (S214). Here, as an example of regularity, it is possible to exemplify that the variation in the period or the variation of the maximum value or the minimum value that is periodically repeated in the time series data is within a predetermined range.

  If the time-series data has a regular period change of 1 / (2Δf), it can be determined that there is no carrier of the desired channel, although there are carriers of adjacent channels on both sides. Is determined not to be used, and communication using the desired channel is permitted (S214, S220 to S224).

  On the other hand, if the time-series data does not change the regular 1 / (2Δf) period, it is determined that the desired channel is being used, and the desired channel is changed to another channel (S208). .

  Thus, carrier sense including the adjacent channel can be performed.

  FIG. 14 is a modification of the flowchart of FIG. Since the basic concept is the same as in FIG. 10, detailed description thereof is omitted. In this example, the threshold level for permitting use is changed between when it is determined that a desired channel is used and when it is determined that a desired channel is not used (S211). And the third predetermined threshold level of S215> the second predetermined threshold level of S213 and S217), if it is determined that the desired channel is not used, the communication of the desired channel is performed even if the interference wave level is somewhat high. Is allowed.

  For example, even if the interference wave is equal to or higher than a second predetermined threshold level (for example, −50 dBm), when an IC tag that is a communication partner approaches, the S / I ratio is improved, so that demodulation is possible. In such a case, the carrier sense efficiency and the selection channel efficiency can be further improved by permitting communication through the desired channel.

DESCRIPTION OF SYMBOLS 10 Signal processing / control part 12 Transmission part 14 Antenna part 16 Reception part 18 Narrow band carrier sense part 20 Wide band carrier sense part

Claims (7)

A communication device that performs communication using any one of a plurality of predetermined channels,
A narrowband carrier sense unit for detecting the reception intensity at a frequency corresponding to an arbitrary desired channel;
A broadband carrier sense unit for detecting reception intensity in the entire band of the predetermined all channels;
Means for permitting communication using a desired channel when the reception intensity detected by the broadband carrier sense unit does not exceed a threshold level over the entire band;
When the reception intensity detected by the broadband carrier sense unit exceeds the threshold level in the entire band, the reception intensity at the frequency corresponding to the desired channel detected by the narrow band carrier sense unit is the threshold value. Means for permitting communication using the desired channel when the level is not exceeded;
A communication apparatus comprising:   When the reception intensity at the frequency corresponding to the desired channel detected by the narrowband carrier sense unit exceeds a threshold level, the narrowband carrier sense unit is found until a desired channel having a reception intensity not exceeding the threshold level is found. The communication apparatus according to claim 1, further comprising means for changing a channel for detecting the reception strength by means of. A communication device that performs communication using any one of a plurality of predetermined channels,
A broadband carrier sense unit for detecting reception intensity in the entire band of the predetermined all channels;
A first means for permitting communication using a desired channel when the reception intensity detected by the broadband carrier sense unit does not exceed a threshold level over the entire band;
A narrowband carrier sense unit for detecting the reception intensity at a frequency corresponding to an arbitrary desired channel;
Second means for permitting communication using the desired channel when the reception intensity at the frequency corresponding to the desired channel detected by the narrowband carrier sense unit does not exceed a threshold level;
And switching between one of the first means and the second means, or one of the wideband carrier sense unit and the first means, the narrowband carrier sense unit, and the second means. A communication device.   When the reception intensity at the frequency corresponding to the desired channel detected by the narrowband carrier sense unit exceeds a threshold level, the narrowband carrier sense unit is found until a desired channel having a reception intensity not exceeding the threshold level is found. 4. The communication apparatus according to claim 3, further comprising means for changing a channel for detecting the reception intensity according to. A communication device that performs communication using any one of a plurality of predetermined channels,
A broadband carrier sense unit for detecting reception intensity in the entire band of the predetermined all channels;
Means for permitting communication using a desired channel when the reception intensity detected by the broadband carrier sense unit does not exceed a threshold level over the entire band;
Means for disallowing communication when the received intensity detected by the broadband carrier sense unit exceeds a threshold level in the entire band;
A communication apparatus comprising: A communication device that performs communication using any one of a plurality of predetermined channels,
A carrier sense unit for detecting the reception intensity in the vicinity of the center frequency of any desired channel;
Storage means for storing a change in the received intensity with respect to the frequency in the vicinity of the center frequency of the channel when a channel is not used and a channel adjacent to the channel is used;
Means for permitting communication using a desired channel when the reception intensity at the center frequency of the desired channel detected by the carrier sense unit does not exceed a threshold level;
When the reception intensity at the center frequency of the desired channel detected by the carrier sense unit exceeds the threshold level and is equal to or lower than the second threshold level, the reception intensity near the center frequency of the desired channel detected by the carrier sense unit The change tendency with respect to the frequency of the received intensity in the vicinity of the center frequency of the desired channel detected by the carrier sense unit is compared with the change tendency with respect to the frequency and the corresponding change tendency stored in the storage means is stored in the storage means. Determining whether or not it matches the trend, and when determining that it matches, means for permitting communication using the desired channel;
A communication apparatus comprising: A communication device that performs communication using any one of a plurality of predetermined channels,
A carrier sense unit for detecting a beat signal between a received signal in a frequency region of any desired channel and at least a part of a frequency region of a channel adjacent thereto and a signal shifted by Δf from the center frequency of the desired channel; ,
Means for detecting the temporal change from the envelope of the beat signal;
Means for permitting communication using a desired channel when it is detected by the means for detecting the change that there is no temporal change in the envelope of the beat signal;
Means for determining whether the time change of the envelope of the beat signal follows a period of 1 / Δf;
Means for disallowing communication using a desired channel when the time change of the envelope of the beat signal follows the period of 1 / Δf by the means for determining;
Means for determining whether the time change of the envelope of the beat signal regularly follows a period of 1 / (2Δf);
Means for permitting communication using a desired channel when the time variation of the envelope of the beat signal regularly follows the period of 1 / (2Δf) by the means for determining;
Means for disallowing communication using a desired channel when the time variation of the envelope of the beat signal does not regularly follow the period of 1 / (2Δf) by the means for determining;
A communication apparatus comprising:

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