JP2008103845A - Wireless communication system, ofdm communication apparatus, and ask communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system capable of reducing interference between an OFDM communication apparatus and an ASK communication apparatus although both the apparatuses are available, and the OFDM communication apparatus and ASK communication apparatus constituting the wireless communication system. <P>SOLUTION: An OOK wireless apparatus 100 is provided with an OOK demodulator 106 which subjects a reception signal to OOK demodulation, a reference signal generator 108 which generates a reference signal in a state wherein a known signal pattern included in a preamble of an OFDM signal has been subjected to OOK demodulation, a correlation acquiring means (a multiplier 109 and an integrator 110) of acquiring a correlation result between the demodulated signal demodulated by the OOK demodulator 106 and the reference signal, a threshold decision unit 111 which decides whether there is the OFDM signal in the reception signal, and a communication controller 112 which controls transmission of an OOK modulated signal on the basis of the decision result. The OFDM wireless apparatus 200 transmits the OFDM signal having the known signal pattern included in the preamble. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio communication system, an OFDM communication apparatus constituting the radio communication system, and an ASK communication apparatus.

  In recent years, UWB (Ultra Wide Band) has attracted attention as an ultra-low power consumption wireless system that can be mounted on portable devices such as mobile phones at high speed. A wireless system currently used communicates using a frequency band of about several tens of MHz, whereas UWB is a wireless system that communicates using a band of several hundred MHz to several GHz. With the announcement of the legislation of the framework to allow short pulse communication using the frequency band of 3.1 to 10.6 GHz as UWB communication if it is below the unnecessary radiation level such as PC from US FCC in 2002, Each company has started standardization activities centering on IEEE802.15.3a and is actively investigating commercialization. In Japan, revisions of related ministerial ordinances are scheduled in the frequency bands of 3.4 GHz to 4.8 GHz and 7.25 GHz to 10.25 GHz, and practical application of UWB communication in the microwave band is near.

  In addition to the microwave band, there are quasi-millimeter wave band (22.0 to 29.0 GHz) and millimeter wave band (59.0 GHz to 66.0 GHz) as frequency bands for which the use of UWB communication is being studied. Utilization scenes and technical considerations, proposal activities for international standards (IEEE 802.15.3c, etc.) are being conducted mainly by the National Institute of Information and Communications Technology (NICT). The millimeter-wave UWB has fewer coexistence systems than the microwave band and can use a wider occupied band, and the radio waves have features such as straightness and high attenuation. The movement toward practical application of high-speed millimeter-wave UWB wireless systems is rapidly spreading.

  As modulation schemes used in the millimeter wave UWB, impulse radio schemes, spread spectrum schemes for direct spread modulation, and multicarrier schemes such as OFDM are candidates. A discussion on which modulation system to adopt is underway in IEEE 802.15.3c. However, considering that IEEE 802.15.3a, which had been standardizing microwave UWB, abandoned standardization in January 2006 and dissolved, the modulation system is not necessarily standardized even in millimeter wave UWB. In such a situation, a plurality of modulation schemes are mixedly used in the same frequency band, which may cause interference with each other.

In order to avoid interference, it is necessary to notify the presence of the wireless communication apparatus having a different modulation method. However, communication is not possible between wireless communication devices with different modulation schemes. As a method of confirming the existence of each other between wireless communication apparatuses having different modulation methods, there is a method of providing a common part in a transmission frame (see Patent Document 1). The common unit is modulated by a modulation scheme common to all wireless communication devices, and can be demodulated by all wireless communication devices. In this way, the common part can be demodulated in both wireless communication apparatuses, so that the existence of each other can be notified.
Japanese Patent No. 3604536

  However, in the conventional communication method, all wireless communication apparatuses must support the modulation scheme used for the common unit only for demodulating the common unit. For example, consider a case where an OOK wireless device that performs wireless communication using an OOK modulation method that is a binary ASK (Amplitude Shift Keying) modulation method and an OFDM wireless device that performs wireless communication using an OFDM modulation method are mixed. . When the common part is modulated by OOK, the OFDM radio apparatus must include OOK modulation / demodulation means in addition to the OFDM modulation / demodulation means. Conversely, when the common part is OFDM-modulated, the OOK radio apparatus adds OFDM modulation / demodulation means to the OOK modulation / demodulation means. Must be provided. This means an increase in circuit scale and power consumption. In particular, since the OFDM modulation scheme is more complicated than the OOK modulation scheme, it is a serious problem for the OOK radio apparatus to include OFDM modulation / demodulation means.

  The present invention has been made in view of such a point, and reduces interference between both apparatuses without providing a new modulation / demodulation means in common to both apparatuses, even though OFDM communication apparatuses and ASK communication apparatuses are mixed. It is an object of the present invention to provide a wireless communication system that can perform communication, an OFDM communication apparatus and an ASK communication apparatus that constitute the wireless communication system.

  An ASK communication apparatus according to the present invention includes an ASK demodulating means for ASK demodulating a received signal, a reference signal generating means for generating a reference signal in a state where a known signal pattern included in a preamble of an OFDM signal is ASK demodulated, and the ASK demodulating means A correlation acquisition unit that acquires a correlation result between the demodulated signal demodulated by the unit and the reference signal, a determination unit that determines presence or absence of the OFDM signal in the received signal based on the correlation result, and the determination And a communication control means for controlling the transmission of the ASK modulation signal based on the result.

  The wireless communication system of the present invention comprises frame generating means for generating a transmission frame including a known signal pattern in a preamble, and OFDM signal forming means for forming an OFDM signal by performing inverse Fourier transform on the transmission frame. OFDM communication apparatus, ASK demodulating means for ASK demodulating the received signal, reference signal generating means for generating a reference signal in a state where the known signal pattern included in the preamble of the OFDM signal is ASK demodulated, and demodulated by the ASK demodulating means A correlation acquisition unit that acquires a correlation result between the demodulated signal and the reference signal, a determination unit that determines presence or absence of the OFDM signal in the received signal based on the correlation result, and a result of the determination Communication control means for controlling transmission of the ASK modulation signal based on A configuration that includes the ASK communication device, the.

  The OFDM communication apparatus according to the present invention includes a frame generation unit that generates a transmission frame including a known signal pattern in a preamble, an OFDM signal formation unit that forms an OFDM signal by performing inverse Fourier transform on the transmission frame, and the known An amplitude fluctuation level control means for switching the amplitude fluctuation level of the signal pattern is adopted.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless communications system which can reduce the interference between both apparatuses, without newly providing a modulation / demodulation means common to both apparatuses, although OFDM communication apparatus and ASK communication apparatus coexist, An OFDM communication apparatus and an ASK communication apparatus that constitute a communication system can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals, and the description thereof will be omitted because it is duplicated.

(Embodiment 1)
FIG. 1 is a diagram showing an example of a usage environment of millimeter wave UWB in Embodiment 1 of the present invention. As shown in FIG. 1, in the present embodiment, an OOK radio apparatus 100 that communicates using an OOK modulation scheme as binary ASK modulation and an OFDM radio apparatus 200 that communicates using an OFDM modulation scheme coexist. Is assumed.

  FIG. 2 is a diagram illustrating an example of a frequency spectrum of an OOK modulated signal transmitted by the OOK wireless device 100 and an OFDM modulated signal transmitted by the OFDM wireless device 200. In the figure, a spectrum 400 is a spectrum of an OOK modulation signal, and spectra 401, 402, 403, and 404 are spectra of an OFDM modulation signal. If each of the OOK radio apparatus 100 and the OFDM radio apparatus 200 starts communication of a transmission signal having a frequency spectrum as shown in the figure (that is, a transmission signal in the same frequency band) without permission, they interfere with each other. become. Therefore, in the present embodiment, the OOK wireless apparatus 100 can avoid interference by detecting the OFDM modulation signal. This will be specifically described below.

  As shown in FIG. 3, the OFDM radio apparatus 200 includes a subcarrier modulation unit 201, a frame generation unit 202, a frame control unit 203, an inverse Fourier transform (IFFT) unit 204, a power amplifier (PA) 205, an antenna, 206. In the figure, the portion related to the present invention is mainly shown. Each component of the OFDM radio apparatus 200 shown in the figure can be realized by hardware, software, or a combination thereof.

  Subcarrier modulation section 201 divides input transmission data into subcarriers for modulation, and outputs a subcarrier modulation signal to frame generation section 202.

  The frame generation unit 202 frames the subcarrier modulation signal according to a predetermined procedure in accordance with the frame control signal input from the frame control unit 203, and outputs the obtained frame signal to the inverse Fourier transform unit 204.

  Specifically, the frame generation unit 202 generates a frame signal having a basic frame configuration of MB-OFDM (MultiBand-OFDM) using the OFDM modulation scheme as shown in FIG. 4, and reverses the generated frame signal. Output to the Fourier transform unit 204. The frame generation unit 202 stores, for example, the subcarrier signal in the payload unit 303 and includes a PHY / MAC header + HCS unit 302 and a preamble 301 including a PHY / MAC header and an HCS (header check sequence) before the pay lobe unit 303. Is added to generate a frame signal.

  The PHY / MAC header + HCS unit 302 stores information such as a destination address, a transmission data rate, and a frame length.

  The preamble section 301 stores signals for packet synchronization, frame synchronization, and channel estimation. Here, the preamble section 301 stores a known fixed signal sequence defined on the time axis, that is, a known signal pattern (for example, a signal sequence in which “1” and “0” are alternately repeated). .

  The frame control unit 203 controls the frame signal generation in the frame generation unit 202 by outputting a frame control signal to the frame generation unit 202.

  The inverse Fourier transform unit 204 performs inverse Fourier transform on the frame signal from the frame generation unit 202 and outputs the obtained OFDM modulated signal to the power amplifier 205.

  The power amplifier (PA) 205 amplifies the OFDM modulated signal from the inverse Fourier transform unit 204 to a predetermined signal level. The amplified OFDM modulation signal is transmitted to the communication partner via the antenna 206.

  As shown in FIG. 5, the OOK radio apparatus 100 includes a gain control unit 102, a detection unit 103, a sampling unit 104, a clock generation unit 105, an OOK demodulation unit 106 as an ASK demodulation unit, and an OFDM signal detection unit 107. And a communication control unit 112. FIG. 5 mainly shows the part related to the present invention. Moreover, each component of the OOK wireless apparatus 100 shown in the figure can be realized by hardware, software, or a combination thereof.

  A signal transmitted from the communication partner is input to the gain control unit 102 as a received signal via the antenna 101.

  The gain control unit 102 amplifies the reception signal, thereby adjusting the amplitude of the reception signal so that the input signal level of the detection unit 103 is constant.

  The detection unit 103 performs envelope detection on the reception signal input via the gain control unit 102 and outputs a detection signal as a detection result to the sampling unit 104. Envelope detection can be realized, for example, by half-wave rectification using a diode and high-frequency component removal using a low-pass filter.

  The sampling unit 104 samples the detection signal at the timing when the clock signal is input from the clock generation unit 105, and outputs the obtained sample value to the OOK demodulation unit 106. The sampling unit is composed of an A / D converter, for example.

  The OOK demodulator 106 demodulates the received signal by comparing the sample value from the sampling unit 104 with a predetermined threshold value. Here, since the signal subjected to OOK modulation, which is binary ASK modulation, is demodulated, the OOK demodulator 106 compares the sample value with a predetermined threshold value Th1. 1 is output to the OFDM signal detection unit 107 as demodulated data when the sample value <Th1.

  The OFDM signal detection unit 107 detects the presence / absence of an OFDM signal based on the correlation result between the demodulated data and the “reference signal”. The OFDM signal detection unit 107 includes a reference signal generation unit 108, a multiplication unit 109, an integration unit 110, and a threshold determination unit 111.

  The reference signal generator 108 generates a “reference signal” that is a known signal sequence (known signal pattern) used for detection of the OFDM modulation signal, and outputs it to the multiplier 109. Here, the “reference signal” is a signal obtained when the OOK demodulation unit 106 demodulates the preamble section 301 that is a known signal sequence included in the OFDM modulation signal shown in FIG.

  The multiplier 109 multiplies the demodulated data and the “reference signal”, and outputs the obtained multiplication value to the integrator 110. Specifically, the multiplier 109 performs an XOR operation between the demodulated data and the “reference signal”. The XOR operation here is performed according to the following rules. That is, 1XOR1 = 1, 1XOR0 = 0, 0XOR1 = 0, and 0XOR0 = 1.

  The integration unit 110 integrates n multiplication values from the multiplication unit 109 (n is a positive number of “reference signal” samples), and outputs the obtained integration result to the threshold determination unit 111 as a correlation value. To do. That is, the multiplication unit 109 and the integration unit 110 function as a correlation acquisition unit.

  The threshold value determination unit 111 compares the correlation value from the integration unit 110 with a predetermined threshold value (Th2). If the correlation value ≧ Th2, the threshold value determination unit 111 sets “1”, and if the correlation value <Th2, the threshold value determination unit 111 sets “0”. It outputs to the communication control part 112 as a detection signal.

  The OFDM signal detection unit 107 shifts the timing of the “reference signal” by one sample at a time until the operation from the multiplication unit 109 to the threshold determination unit 111 satisfies correlation value ≧ Th2 or m times (m> n). m is a positive number and is the number of samples when one frame of the OFDM modulated signal is sampled by the sampling unit 104).

  Here, an OFDM signal detection method in the OFDM signal detection unit 107 will be described. FIG. 6 is a diagram illustrating an example of demodulated data obtained when the preamble section 301 and the payload section 303 are demodulated by the OOK demodulation section 106.

  As described above, the preamble part 301 is a signal defined on the time axis and includes a signal having a repetitive pattern of “1” and “0”. Therefore, when observed on the time axis, It looks as if it is an amplitude-modulated signal (see FIG. 6A).

  On the other hand, since random data modulated on the frequency axis is included in the payload section 303, when the payload section 303 is observed on the time axis, it looks like noise (see FIG. 6B).

  That is, when the OFDM signal is envelope-detected and further demodulated data is obtained by performing OOK demodulation (threshold determination), the preamble section 301 regularly alternates between the sections where “1” continues and “0” continues. (See FIG. 6A). On the other hand, in the payload section 303, a section in which “1” continues and a section in which “0” continues are randomly obtained (see FIG. 6B).

  In addition, since a known signal sequence is included in the preamble section 301, the result of threshold determination of the preamble section 301 by the OOK demodulation section 106 is also known.

  Therefore, the reference signal generating unit 108 generates demodulated data obtained when the preamble unit 301 is demodulated by the OOK demodulating unit 106 as a “reference signal” and correlates the demodulated data with the “reference signal”. The payload portion 303 can be detected from the correlation result, and as a result, the presence or absence of the OFDM signal can be detected.

  Thus, the OFDM signal detection unit 107 can output an OFDM detection signal indicating the presence or absence of the OFDM signal to the communication control unit 112.

  The communication control unit 112 controls communication of the OOK wireless device 100 according to the OFDM detection signal. Specifically, if no OFDM modulation signal is detected, the communication control unit 112 starts communication using OOK. If an OFDM modulation signal is detected, the communication control unit 112 suspends communication using OOK and waits for a predetermined period. Thereafter, the ASK modulation transmission of the OOK wireless apparatus 100 is controlled so as to start communication with OOK.

  An operation in which the OOK wireless apparatus 100 having the above configuration detects an OFDM modulated signal will be described. FIG. 7 is a flowchart showing a procedure in which the OOK wireless apparatus 100 detects an OFDM modulated signal.

  First, in step 1001, before starting communication, the OOK wireless device 100 receives radio waves in order to confirm the existence of the OFDM wireless device 200 that communicates using OFDM around the device.

  In step 1002, after the OOK radio apparatus 100 adjusts the amplitude level of the received signal by the gain control unit 102, the detection unit 103 performs envelope detection on the received signal.

  In step 1003, the OOK wireless device 100 samples the detection signal by the sampling unit 104.

  In step 1004, the OOK radio apparatus 100 determines the threshold value of the sampling value by the OOK demodulator 106 and demodulates it.

  In step 1005, OOK radio apparatus 100 calculates a correlation value between the demodulated data and the reference signal by multiplication section 109 and integration section 110.

  In step 1006, the OOK wireless apparatus 100 compares the correlation value with a predetermined threshold (Th2) in the threshold determination unit 111.

  When the correlation value ≧ Th2 (step 1006: YES), the threshold determination unit 111 outputs “1” as an OFDM detection signal to the communication control unit 112, and the communication control unit 112 that has received it outputs the OOK radio apparatus 100. Control is performed so as to wait for a predetermined time without starting communication with OOK (step 1007). That is, the communication control unit 112 performs control to stop transmission of the OOK modulation signal during a period in which it is determined that there is an OFDM signal in the received signal.

  On the other hand, if correlation value <Th2 (step 1006: NO), threshold determination section 111 outputs “0” as an OFDM detection signal to communication control section 112, and communication control section 112 that has received it outputs OFDM modulation. It is determined that no signal has been detected, and control is performed so that the OOK wireless device 100 starts communication with OOK (step 1008).

  In this way, the OOK radio apparatus 100 detects the presence / absence of the OFDM modulation signal, and when the OFDM detection / modulation signal is detected, the OOK radio apparatus 100 can avoid interference with the OFDM radio apparatus 200 by waiting for a predetermined period without communication. it can.

  As described above, according to the present embodiment, the OOK radio apparatus 100 generates the OOK demodulator 106 that performs OOK demodulation of the received signal, and the reference signal in which the known signal pattern included in the OFDM signal preamble is OOK demodulated. A reference signal generation unit 108 as a reference signal generation unit, a correlation acquisition unit (multiplication unit 109, integration unit 110) for acquiring a correlation result between the demodulated signal demodulated by the OOK demodulation unit 106 and the reference signal; Based on the correlation result, a determination unit (threshold determination unit 111) that determines the presence or absence of the OFDM signal in the received signal, and a communication control unit that controls transmission of an OOK modulation signal based on the determination result ( Communication control unit 112).

  By doing so, it is determined whether the OFDM signal is received without mounting the OFDM demodulation means in the OOK radio apparatus 100, that is, while avoiding an increase in circuit scale and power consumption of the OOK modulation radio apparatus 100. When it is determined that the OFDM signal is received, it is possible to control the transmission of the OOK modulation signal, so that it is possible to reduce interference with the OFDM radio apparatus during communication. Note that the concept of the present embodiment is not limited to binary OOK demodulation, but can also be applied to ASK demodulation.

  The communication control unit (communication control unit 112) transmits an ASK modulation signal (here, an OOK modulation signal) during a period in which the determination unit (threshold determination unit 111) determines that there is an OFDM signal in the received signal. Stop.

  By doing so, when it is determined that at least the OFDM signal is received, it is possible to control the transmission of the OOK modulation signal, so that it is possible to reduce interference with the OFDM radio apparatus during communication.

  Further, the OFDM radio apparatus 200 has a frame generation means (frame generation unit 202) that generates a transmission frame including a known signal pattern in a preamble, and an OFDM signal that forms an OFDM signal by performing inverse Fourier transform on the transmission frame. Forming means (inverse Fourier transform unit 204). The amplitude of the known signal pattern is periodically changed in the time direction.

  By doing so, it becomes easy to distinguish from the data portion such as the payload portion, so that the processing in the receiving-side OOK wireless apparatus 100 can be simplified.

(Embodiment 2)
In Embodiment 2, the frame generation unit of the OFDM radio apparatus switches the known signal sequence (known signal pattern) included in the preamble unit according to the frame control signal. Specifically, a signal sequence that is easy to demodulate for the receiving-side OOK wireless device (that is, a signal sequence that has a large amplitude variation) and a signal sequence that does not consider whether or not the OOK wireless device is easy to demodulate (that is, amplitude variation is Small signal train). In addition, the receiving-side OOK radio apparatus sets a predetermined threshold (Th1) so that the presence or absence of the OFDM signal can be detected even if the signal sequence with small amplitude fluctuation is an OFDM signal included in the preamble part. It can be adjusted appropriately. Furthermore, the “reference signal” is also switched to a signal that matches a signal sequence with small amplitude fluctuations. This will be specifically described below. The main configuration of the OFDM radio apparatus is the same as that of OFDM radio apparatus 200 of Embodiment 1, and will be described with reference to FIG.

  Frame control section 203 of OFDM radio apparatus 200 outputs a frame control signal to frame generation section 202, and controls switching of a known signal sequence included in preamble section 301.

As a known signal switching control method, the following control method can be considered.
(1) Regardless of the presence of the OOK wireless device, the OFDM wireless device 200 always uses a signal sequence having a large amplitude variation.
(2) Regardless of the presence of the OOK wireless device, the OFDM wireless device 200 always uses a signal sequence with small amplitude fluctuations.
(3) The OFDM radio apparatus 200 performs carrier sense for all channels (all of f1, f2, f3, and f4 in FIG. 2). If all the channels are in use as a result of the carrier sense, it is assumed that the OOK wireless device is communicating, and a signal sequence having a large amplitude variation is used.
(4) The OFDM radio apparatus uses a signal sequence having a large amplitude variation for the first X times after the start of communication, and uses a signal sequence having a small amplitude variation thereafter.

  FIG. 8 is a block diagram showing a configuration of OOK wireless apparatus 500 according to the second embodiment. As described above, when the signal sequence stored in the preamble section 301 is a signal sequence with a small amplitude fluctuation level as a result of the known signal switching control in the OFDM radio apparatus 200, the threshold value is set as shown in FIG. Since (Th1) is too small, the threshold determination in the OOK demodulating unit 106 is not properly performed. Therefore, it is necessary to adjust the threshold value (Th1) to an appropriate value. Further, since the reference signal generation unit 108 does not know in advance which signal sequence of a signal sequence having a large amplitude variation and a signal sequence having a small amplitude variation is stored in the payload unit 301, which signal sequence is You must determine if it is stored.

  Therefore, as shown in FIG. 8, the OOK radio apparatus 500 includes an amplitude fluctuation level detection unit 502, a threshold control unit 504, an OOK demodulation unit 506, and an OFDM signal detection unit 507. The OFDM signal detection unit 507 includes a reference signal generation unit 508.

  The amplitude fluctuation level detection unit 502 detects a section (a section considered to be the preamble section 301) in which the amplitude periodically varies from the sample values output from the sampling section 104. The amplitude variation level detection unit 502 detects the maximum value and the minimum value in the sample values of the detected section, and outputs the average value of each of the maximum value and the minimum value to the threshold value control unit 504.

  The threshold control unit 504 determines the magnitude of the amplitude variation of the signal sequence used in the preamble unit 301 based on the average value of the maximum value and the minimum value from the amplitude variation level detection unit 502.

  Specifically, the threshold value control unit 504 determines that the signal sequence has a large amplitude variation when the average value of the local minimum values is smaller than the threshold value Th1. On the other hand, when the average value of the local minimum values is larger than the threshold value Th1, the threshold value control unit 504 determines that the signal sequence has a small amplitude variation. Then, the threshold control unit 504 outputs the determination result to the reference signal generation unit 508 of the OFDM signal detection unit 507 as amplitude variation level information.

  When the threshold control unit 504 determines that the signal sequence has a small amplitude variation, the threshold Th1 set in the OOK demodulation unit 506 is set to an intermediate value between the average value of the maximum value and the average value of the minimum value. Control to adjust. In this way, demodulated data can be obtained even when the amplitude variation of the known signal sequence of the preamble section 301 is small.

  The reference signal generation unit 508 of the OFDM signal detection unit 507 switches the reference signal between when the amplitude variation is large and when the amplitude variation is small according to the amplitude variation level signal from the threshold control unit 504.

  As described above, according to the present embodiment, OOK radio apparatus 500 generates an OOK demodulator 506 that performs OOK demodulation of a received signal, and a reference signal in which a known signal pattern included in the preamble of the OFDM signal is OOK demodulated. A reference signal generation unit 508 as a reference signal generation unit, a correlation acquisition unit (multiplication unit 109, integration unit 110) for acquiring a correlation result between the demodulated signal demodulated by the OOK demodulation unit 506 and the reference signal; Based on the correlation result, a determination unit (threshold determination unit 111) that determines the presence or absence of the OFDM signal in the received signal, and a communication control unit that controls transmission of an OOK modulation signal based on the determination result ( Communication control unit 112) and amplitude fluctuation level detecting means (amplitude fluctuation level) for detecting the amplitude fluctuation level of the received signal. The OOK demodulator 506 adjusts a threshold value used for demodulation based on the detection result of the amplitude fluctuation level, and the reference signal generator 508 serving as the reference signal generator A plurality of reference signals corresponding to known signal patterns having different amplitude fluctuation levels are generated, and the generated reference signals are switched based on the detection result of the amplitude fluctuation levels.

  In this way, the amplitude fluctuation level of the received signal can be detected, and the threshold used for OOK demodulation can be appropriately adjusted according to the detection result. Therefore, even when the OOK radio apparatus 500 receives an OFDM signal transmitted with the amplitude fluctuation level lowered by the OFDM radio apparatus, a demodulated signal that appropriately reflects the known signal pattern can be obtained. In addition, since the reference signal to be generated can be switched according to the detection result of the amplitude fluctuation level of the received signal, the correlation value of the reference signal suitable for the amplitude fluctuation level of the known signal pattern included in the received signal is acquired. It becomes possible to do. That is, the reliability of the correlation result between the demodulated signal appropriately reflecting the known signal pattern and the reference signal suitable for the amplitude fluctuation level of the known signal pattern included in the received signal is also increased. Since communication control can be performed based on this highly reliable correlation result, the certainty of avoiding interference can be improved.

  Specifically, the amplitude fluctuation level detecting means (amplitude fluctuation level detecting section 502) detects the average value of the local maximum value and the local minimum value in the waveform in the time direction related to the received signal, and serves as a reference signal generating means. The signal generation unit 508 switches the generated reference signal according to the magnitude of the average value of the minimum values and the threshold value used in the OOK demodulation unit 506.

  By doing so, it is considered that the amplitude fluctuation level of the received signal is small when the average value of the minimum value is larger than the threshold value. Therefore, when the average value of the minimum value is larger than the threshold value, the known signal pattern having a small amplitude fluctuation level. By switching to the reference signal corresponding to, a highly reliable correlation result can be acquired.

  The OOK demodulator 506 adjusts the threshold value to a median value between the average value of the maximum values and the average value of the minimum values when the average value of the minimum values is larger than the threshold value.

  By doing this, it is possible to always set a threshold value between the average value of the local minimum value and the average value of the local maximum value, so that the power fluctuation level of the known signal pattern included in the OFDM signal in the received signal is small or large. Regardless of this, a demodulated signal appropriately reflecting a known signal pattern can be obtained.

  Further, the OFDM radio apparatus 200 has a frame generation means (frame generation unit 202) that generates a transmission frame including a known signal pattern in a preamble, and an OFDM signal that forms an OFDM signal by performing inverse Fourier transform on the transmission frame. Forming means (inverse Fourier transform unit 204) and amplitude fluctuation level control means (frame control unit 203) for switching the amplitude fluctuation level of the known signal pattern are provided.

  In this way, for example, when it is desired that the receiving-side OOK radio apparatus recognize the presence of its own apparatus, it is possible to control to increase the power of the transmission OFDM signal by increasing the amplitude fluctuation level. .

  Also, the amplitude fluctuation level control means (frame control unit 203) performs control to increase the amplitude fluctuation level when the carrier sense result indicates that another communication apparatus is communicating in the use frequency band of the own apparatus. May be.

  Further, the amplitude fluctuation level control means (frame control unit 203) may perform control to increase the amplitude fluctuation level in a predetermined number of transmission frames from the start of communication and lower the amplitude fluctuation level in subsequent transmission frames.

(Embodiment 3)
In the third embodiment, as shown in FIG. 10, there is an OOK / OFDM radio apparatus 600 that can support both the OFDM modulation scheme and the OOK modulation scheme, and the OOK radio apparatus 700 and the OFDM radio apparatus 800 are OOK / OFDM. Consider a case of communicating with wireless device 600. In this case, since the OOK / OFDM radio apparatus 600 supports both OOK and OFDM modulation schemes, the OOK communication and the OFDM communication can be synchronized. For this reason, the OOK wireless apparatus 700 knows the timing at which the preamble portion 301 of the OFDM modulation signal is transmitted, and therefore, as in the first embodiment, the sliding correlation is set to m (maximum m) for one frame of the OFDM modulation signal. It is not necessary to repeat the number of samples at the time of sampling in (5), and it is only necessary to perform n (the number of samples of the reference signal) at most, so that power consumption can be reduced.

  However, as illustrated in FIG. 11, the OOK wireless apparatus 700 includes a confirmation signal generation unit 720, an OOK modulation unit 722 as an ASK modulation unit, and a transmission / reception duplexer 724, and when an OFDM modulated signal is detected, A “confirmation signal” indicating that an OFDM modulated signal has been detected is transmitted to the OFDM radio apparatus 800.

  Confirmation signal generation section 720 generates a “confirmation signal” for notifying OFDM radio apparatus 800 that the OFDM modulation signal has been detected, in response to the OFDM detection signal from OFDM signal detection section 107, and provides it to OOK modulation section 722. Output. The “confirmation signal” may have any content as long as it is not a signal of “0”. This is because the OOK wireless device 700 transmits only an OOK modulated signal, and therefore, even if the OFDM wireless device 800 receives and demodulates the “confirmation signal”, the random data becomes meaningless. In the case of all “0”, it cannot be used because it is the same as no signal.

  The OOK modulation unit 722 performs OOK modulation on the “confirmation signal”. The OOK-modulated “confirmation signal” is transmitted from the antenna 101 to the OFDM radio apparatus 800 via the duplexer 724.

  As shown in FIG. 12, OFDM radio apparatus 800 includes transmission / reception duplexer 810, OFDM demodulator 812, confirmation signal detector 814, and frame controller 816.

  The OFDM demodulator 812 performs OFDM demodulation on the received signal input from the antenna 206 via the duplexer 810 and outputs the obtained demodulated data to the confirmation signal detector 814.

  The confirmation signal detection unit 814 searches for (detects) the “confirmation signal” transmitted from the OOK wireless apparatus 700 from the demodulated data.

  As described above, since the “confirmation signal” is an OOK-modulated signal, the contents of the data cannot be understood even by OFDM demodulation. Therefore, the confirmation signal detection unit 814 transmits the random data from the OOK wireless device 700 when random demodulated data is obtained within a predetermined time after the OFDM wireless device 700 transmits the preamble unit 301. Judge as “confirmation signal”. The frame control unit 816 of the OFDM radio apparatus 800 performs control to start communication (frame transmission) when the confirmation signal detection unit 814 determines that the “confirmation signal” is detected. Note that after repeating this operation one or more times, the frame control unit 816 of the OFDM radio apparatus 800 may start communication (frame transmission).

  As a result, the OFDM radio apparatus 800 can be seen that the OOK radio apparatus 700 exists around the own apparatus and that the OOK radio apparatus 700 has confirmed the existence of the own apparatus (OFDM radio apparatus 800). Therefore, it is possible to more reliably avoid interference with the OOK wireless apparatus 700.

  When the “confirmation signal” is not obtained within a predetermined time, it is determined that there is no OOK wireless device 700 in the vicinity, and the frame control unit 816 of the OFDM wireless device 800 performs control to start communication. On the contrary, when the “confirmation signal” is not obtained within a predetermined time, it is determined that the OOK wireless apparatus 700 may want to communicate, and the frame control unit 816 of the OFDM wireless apparatus 800 performs communication ( Control may be made so that the transmission (frame transmission) is suspended and communication (frame transmission) is waited for a predetermined period.

  Thus, according to the present embodiment, when it is determined that OOK wireless apparatus 700 has an OFDM signal in the received signal, notification information for notifying the transmission source of the OFDM signal of the determination result is provided. Notification information generation means (confirmation signal generation unit 720) for generation is provided.

  In this way, by receiving the notification signal, the transmission source of the OFDM signal can recognize that there is an OOK wireless device that has not started transmission of the OOK modulation signal, and can also transmit its own device (OFDM signal transmission). It is also possible to confirm that the OOK wireless device recognizes the presence of the original), so if transmission of transmission data is started using the payload portion in the OFDM signal after this confirmation, the OFDM wireless device will be able to confirm the OOK wireless device. Interference with can also be avoided.

  Further, the OFDM radio apparatus 800 is provided with notification information detection means (confirmation signal detection unit 814) that detects the notification information by acquiring random demodulated data within a predetermined period after the transmission of the OFDM signal.

  In this way, when receiving OOK-modulated notification information in the OOK wireless device, the demodulated data of the notification information does not make sense for the OFDM wireless device. By assuming that the notification information is detected by acquiring random demodulated data within the period, it is possible to detect communication information from an OOK wireless device with a different modulation scheme.

  Further, the frame generation means (frame generation unit 202) of the OFDM radio apparatus 800 generates a transmission frame including transmission data in the payload after the notification information is detected.

  By so doing, it is possible to reduce the probability of interference with the OOK wireless device.

  The frame generation unit (frame generation unit 202) may be configured to be able to switch the amplitude fluctuation level of the known signal pattern, and may increase the amplitude fluctuation level when the notification information is detected.

  The frame generation means (frame generation unit 202) may stop the generation of the frame for a predetermined period when the notification information is detected.

(Other embodiments)
In the first to third embodiments, the OOK radio apparatus 100 (500, 700) includes the gain control unit 102 so that the input signal level to the detection unit 103 is constant. This is for the purpose of appropriately performing threshold determination in the OOK demodulator 106 (506), but gain control is not necessarily required in detecting an OFDM modulated signal.

  In the OOK radio apparatus 100 (500) configured without providing the gain control unit 102, the detection signal level is not constant, and therefore, unless the reception level of the OFDM modulation signal accidentally becomes a desired signal level, the OOK demodulation unit The threshold determination at 106 (506) is not performed appropriately.

  For example, when the reception level of the OFDM modulated signal is always smaller than the threshold value Th1, the demodulated data is all “0”. In such a case, there is no need to calculate the correlation value with the reference signal by the OFDM signal detection unit 107 (507). That is, when “0” continuously appears in the demodulated data for a predetermined number or more, it is considered that the OFDM modulation signal has not been detected, and communication using OOK may be started. This is because a low received signal level means that even if an OFDM modulated signal exists, it can be regarded as communicating remotely, and the OOK modulated signal interferes with the OFDM modulated signal. Because there is no.

  Therefore, in such a case, the communication control unit 112 of the OOK wireless device 100 (500, 700) may perform control to start communication using OOK. Conversely, when the reception level of the OFDM modulated signal is always higher than Th1, all the demodulated data is “1”. In this case, since it can be considered that OFDM communication is being performed in the vicinity of the OOK wireless device 100 (500, 700), the communication control unit 112 controls to wait for a while.

  By doing so, there is no need to provide an OFDM signal detector in the OOK wireless device.

  The wireless communication system, the OFDM communication apparatus, and the ASK communication apparatus according to the present invention can prevent interference between both apparatuses without providing a new modulation / demodulation means in common to both apparatuses while the OFDM communication apparatus and the ASK communication apparatus are mixed. This is useful as a wireless communication system that can be reduced, and an OFDM communication apparatus and an ASK communication apparatus constituting the wireless communication system.

The figure which shows an example of the usage environment of the millimeter wave UWB in Embodiment 1 of this invention The figure which shows an example of the frequency spectrum of the OOK modulation signal which an OOK radio | wireless apparatus transmits, and the OFDM modulation signal which an OFDM radio | wireless apparatus transmits FIG. 2 is a block diagram showing a configuration of an OFDM radio apparatus according to the first embodiment. The figure which shows the basic frame structure of MB-OFDM (MultiBand-OFDM) FIG. 2 is a block diagram illustrating a configuration of the OOK wireless device according to the first embodiment. The figure which showed an example of the demodulation data obtained when a preamble part and a payload part are demodulated with an OOK demodulation part Flow chart showing a procedure for detecting an OFDM modulated signal by the OOK wireless device FIG. 3 is a block diagram illustrating a configuration of an OOK wireless device according to a second embodiment. The figure for demonstrating the relationship between the received signal with a small amplitude fluctuation level, and the threshold value used in an OOK demodulation part. The figure which shows the structure of the radio | wireless communications system of Embodiment 3. Block diagram showing a configuration of an OOK wireless apparatus according to the third embodiment FIG. 3 is a block diagram showing a configuration of an OFDM radio apparatus according to a third embodiment.

Explanation of symbols

100, 500, 700 OOK wireless device 101, 206 Antenna 102 Gain control unit 103 Detection unit 104 Sampling unit 105 Clock generation unit 106, 506 OOK demodulation unit 107, 507 OFDM signal detection unit 108, 508 Reference signal generation unit 109 Multiplication unit 110 Integration unit 111 Threshold determination unit 112 Communication control unit 200,800 OFDM radio apparatus 201 Subcarrier modulation unit 202 Frame generation unit 203,816 Frame control unit 204 Inverse Fourier transform unit 205 Power amplifier 502 Amplitude fluctuation level detection unit 504 Threshold control unit 720 Confirmation signal generation unit 722 OOK modulation unit 724,810 Transmission / reception duplexer 812 OFDM demodulation unit 814 Confirmation signal detection unit

Claims (16)

ASK demodulating means for ASK demodulating the received signal;
A reference signal generating means for generating a reference signal in a state where the known signal pattern included in the preamble of the OFDM signal is ASK demodulated;
Correlation obtaining means for obtaining a correlation result between the demodulated signal demodulated by the ASK demodulating means and the reference signal;
Determining means for determining the presence or absence of the OFDM signal in the received signal based on the correlation result;
Communication control means for controlling transmission of the ASK modulated signal based on the result of the determination;
An ASK communication apparatus comprising:   2. The ASK communication apparatus according to claim 1, wherein the communication control unit stops transmission of the ASK modulation signal during a period in which the determination unit determines that there is an OFDM signal in the received signal. Further comprising amplitude fluctuation level detecting means for detecting the amplitude fluctuation level of the received signal;
The ASK demodulating means adjusts a threshold value used for demodulation based on the detection result of the amplitude fluctuation level,
The reference signal generation means is configured to be able to generate a plurality of reference signals corresponding to known signal patterns having different amplitude fluctuation levels, and switches the reference signal to be generated based on the detection result of the amplitude fluctuation levels. ASK communication apparatus of description. The amplitude fluctuation level detecting means detects an average value of a local maximum value and a local minimum value in a waveform in a time direction related to the received signal,
4. The ASK communication apparatus according to claim 3, wherein the reference signal generating means switches a reference signal to be generated in accordance with a magnitude of an average value of the minimum values and the threshold value used in the ASK modulation means. The amplitude fluctuation level detecting means detects an average value of a local maximum value and a local minimum value in a waveform in a time direction related to the received signal,
4. The ASK communication according to claim 3, wherein the ASK demodulation means adjusts the threshold value to a median value between the average value of the maximum values and the average value of the minimum values when the average value of the minimum values is larger than the threshold value. apparatus.   2. The ASK according to claim 1, further comprising notification information generation means for generating notification information for notifying a transmission result of the OFDM signal when the determination means determines that the OFDM signal is present. Communication device. An OFDM communication apparatus comprising: frame generating means for generating a transmission frame including a known signal pattern in a preamble; and OFDM signal forming means for forming an OFDM signal by performing inverse Fourier transform on the transmission frame;
ASK demodulating means for ASK demodulating the received signal, reference signal generating means for generating a reference signal in a state where the known signal pattern included in the preamble of the OFDM signal is ASK demodulated, and the demodulated signal demodulated by the ASK demodulating means, Correlation acquisition means for acquiring a correlation result with the reference signal; determination means for determining presence / absence of the OFDM signal in the received signal based on the correlation result; and ASK modulation based on the determination result An ASK communication device comprising: a communication control means for controlling transmission of a signal;
A wireless communication system comprising:   The wireless communication system according to claim 7, wherein the known signal pattern periodically varies in amplitude in a time direction. The ASK communication apparatus, when it is determined by the determination means that the OFDM signal is present, notification information generation means for generating notification information for notifying the determination result to the transmission source of the OFDM signal, ASK transmission means for transmitting an ASK modulated signal of communication information, and
8. The wireless communication system according to claim 7, wherein the OFDM communication apparatus further comprises notification information detection means for detecting the notification information.   The wireless communication system according to claim 9, wherein the notification information detection means detects the notification information by acquiring random demodulated data within a predetermined period after the transmission of the OFDM signal.   The wireless communication system according to claim 9, wherein the frame generation unit generates a transmission frame including transmission data in a payload after detecting the notification information.   10. The wireless communication system according to claim 9, wherein the frame generation unit is configured to be able to switch an amplitude fluctuation level of the known signal pattern, and increases the amplitude fluctuation level when the notification information is detected.   The wireless communication system according to claim 9, wherein the frame generation unit stops generation of the frame for a predetermined period when the notification information is detected. Frame generating means for generating a transmission frame including a known signal pattern in a preamble;
OFDM signal forming means for forming an OFDM signal by performing an inverse Fourier transform on the transmission frame;
Amplitude fluctuation level control means for switching the amplitude fluctuation level of the known signal pattern;
An OFDM communication apparatus comprising:   The OFDM communication apparatus according to claim 14, wherein the amplitude fluctuation level control means increases the amplitude fluctuation level when a carrier sense result indicates that another communication apparatus is communicating in the use frequency band of the own apparatus. The OFDM communication apparatus according to claim 14, wherein the amplitude fluctuation level control means increases the amplitude fluctuation level in a predetermined number of transmission frames from the start of communication, and decreases the amplitude fluctuation level in subsequent transmission frames.

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