JP2007166068A - Wireless communication apparatus and wireless communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication apparatus and a wireless communication method capable of detecting a jamming wave with smaller power consumption and avoiding interference in consideration of a frequency use efficiency in the UWB communication adopting the OFDM modulation system. <P>SOLUTION: The wireless communication apparatus detects a signal level to determine DAA before applying digital conversion processing to a received analog signal. When detecting a jamming wave from another communication system, the wireless communication apparatus drives a digital circuit with a frequency selection action, applies DAA determination to a narrow band signal being the jamming wave in the unit of a subcarrier, and a transmission system provides a notch only to a frequency band including the jamming wave to establish the UWB communication. On the other hand, when the jamming wave is not detected in an analog signal, a data transmission is started depending on a result of the DAA determination. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an OFDM modulation type radio communication apparatus and radio communication method for converting and transmitting a signal arranged on a time axis while maintaining orthogonality of a plurality of subcarriers, and in particular, spreads a transmission signal over a wide band. The present invention relates to a wireless communication apparatus and a wireless communication method that employ an OFDM modulation method in UWB communication.

  More particularly, the present invention relates to a wireless communication apparatus and a wireless communication method for performing UWB communication while avoiding interference with a conventional communication system using a narrowband signal. The present invention relates to a wireless communication apparatus and a wireless communication method that perform UWB communication while avoiding interference with narrowband signals of a system.

  In recent years, a wireless communication system using an extremely wide frequency band called “ultra wide band (UWB) communication” has attracted attention. UWB is a technology that enables high-speed transmission of 100 Mbps or more. In the United States, a spectrum mask for UWB is defined by the FCC (Federal Communications Commission), and 3.1 GHz to 10.3 in an indoor environment. UWB transmission can be performed in a 6 GHz band. UWB communication is a short-range wireless communication system because of transmission power, but high-speed wireless transmission is possible, so a PAN with a communication distance of about 10 m is assumed, and wireless that realizes short-range ultrahigh-speed transmission. The practical use is expected as a communication system.

  Further, an OFDM (Orthogonal Frequency Division Multiplexing) transmission system is expected as a technique for realizing high speed and high quality wireless transmission while avoiding deterioration of transmission quality due to fading of wireless signals. For example, in IEEE802.11a / g, an OFDM modulation scheme is adopted as a standard for a wireless LAN. Also in the standardization meeting in IEEE802.15.3a, as a UWB transmission method, a DSSS (Direct Sequence Spread Spectrum) -UWB method in which a spreading speed of a DS (Direct Spread) information signal is increased to the limit, and an OFDM (Orthogonal Frequent Frequency). Two types of OFDM_UWB systems that employ a Multiplexing (Orthogonal Frequency Division Multiplexing) modulation system are defined, and trial production is performed for each system.

  In the OFDM transmission system, a plurality of data output by serial / parallel conversion of a transmission sequence for each symbol period slower than an information transmission rate is assigned to each subcarrier, and, for example, inverse FFT is performed on the plurality of subcarriers. Are converted into signals arranged on the time axis and transmitted while maintaining the orthogonality of the subcarriers arranged in the same manner. That subcarriers are orthogonal to each other means that the peak point of the spectrum of an arbitrary subcarrier always coincides with the zero point of the spectrum of another subcarrier.

  According to the OFDM modulation scheme, transmission data is distributed and transmitted to a plurality of carriers having different frequencies, so that the bandwidth of each carrier is narrow, the frequency utilization efficiency is very high, and it is resistant to frequency selective fading interference.

  In offices and the like, a communication environment in which a plurality of wireless networks are constructed in a narrow space is assumed, and there is a problem of coexistence of networks. Therefore, a frequency hopping (FH) method for flexibly changing the frequency band to be used is adopted. According to this communication method, packets are sent and received while changing the frequency randomly each time, and communication may not be possible due to the influence of other systems, but communication may be interrupted by constantly changing the frequency. rare. That is, it can coexist with other systems, has excellent fading resistance, and is easy to scale.

  For example, in the above-described standardization conference in IEEE802.15.3, in both the DSSS-UWB system and the OFDM_UWB system, a band from 3.1 GHz to 10.6 GHz defined by the FCC is a plurality of sub-bands each having a width of 528 MHz. A multi-band scheme in which the frequency band hopping (FH) is performed between the sub-bands by dividing into bands is under study.

  FIG. 5 shows an example of frequency allocation defined in an OFDM_UWB communication system (hereinafter also referred to as “multiband OFDM”) employing multiband (see, for example, Non-Patent Document 1). In the illustrated example, the 5 GHz band used by the wireless LAN is a null band, and the other bands are divided into 13 subbands. Each subband is divided into four groups A to D, and the frequency is managed and communication is performed in units of groups.

  FIG. 6 shows a state in which data transmission is performed while performing frequency hopping on a time-axis OFDM symbol in the multiband OFDM scheme. In the illustrated example, group A consisting of bands # 1 to # 3 is used, and frequency hopping is performed while changing the center frequency for each OFDM symbol, and OFDM modulation using IFFT / FFT consisting of 128 points is performed.

  By the way, in a recent wireless communication environment such as an office, it is assumed that a plurality of communication systems coexist, and there is concern that mutual transmission signals become interference waves of other systems. For this reason, it is necessary to mitigate the level of interference with other systems caused by UWB transmission waves, and detect and avoid (hereinafter also referred to as “DAA”), that is, transmission signals of other systems within the UWB transmission band. It is indispensable to check whether it exists, and to output a UWB transmission wave below a certain level (weak level) if it exists.

  The basic method of DAA is to avoid collision by starting each terminal's own information transmission after confirming that each terminal has no other information transmission. Here, the signal of the other system, which is a problem in DAA, is usually a narrowband signal, whereas the transmission signal is spread over a wide band according to the UWB communication system, so the influence of the UWB communication system on the other system. Is only part of the bandwidth used. For this reason, avoiding collisions over all bands (1 OFDM symbol) by detecting transmission signals from other systems is not efficient in frequency utilization.

  Therefore, rather than lowering the UWB output level spread over a wide band uniformly below a specified level over all bands (one OFDM symbol), only for the frequency band (ie, the corresponding subcarrier) in which the signal is detected, It is preferable that the UWB output level is selectively lowered below a specified level from the viewpoint of frequency utilization efficiency, and as a high-speed communication method.

  For example, when a narrow-band carrier in the UWB band is detected, by performing spectrum shaping on the transmission signal, only the subcarrier in the frequency band in which the transmission signal of the other system is detected is cut out (see FIG. 7). It is possible to perform UWB communication using other frequency bands while avoiding interference with other systems (see, for example, Non-Patent Document 2).

  The terminal can perform DAA determination by A / D converting the received signal in the receiving system and then calculating the signal level in the digital circuit. In addition, since FFT has a frequency detection function, in the case of OFDM modulation, the received signal is A / D converted and further subjected to FFT to inspect the frequency band with the interference wave in subcarrier units. (For example, see Patent Document 1). That is, DAA can be determined on a subcarrier basis based on the result of OFDM demodulation (see FIG. 8).

  However, signal level detection by a digital circuit generally requires a large amount of arithmetic processing such as many multipliers, resulting in an increase in device cost. Further, in the case of a system using a wide band such as a multiband OFDM communication system, power consumption increases when the FFT is fully operated, and the burden is excessive as preprocessing for data transmission. An attempt to detect the received signal level by a digital circuit may require power ranging from several millimeters to several tens of milliwatts. In view of the fact that there is often no interference wave consisting of a narrowband signal, the operation of this type of digital circuit for the purpose of mere signal detection rather than data transmission is not worth the cost.

JP 2004-188035 A, paragraph numbers 0018 to 0019. “MBOFDM PHY Specification Final Release 1.0,” Wimedia alliance, April 27, 2005. http://wimedia.org/en/index.asp

  An object of the present invention is to provide an excellent radio communication apparatus and radio capable of suitably performing a communication operation while avoiding interference with a conventional communication system using a narrowband signal in UWB communication adopting an OFDM modulation scheme. It is to provide a communication method.

  A further object of the present invention is an excellent wireless communication capable of suitably performing communication while avoiding interference with narrowband signals of other systems in consideration of frequency utilization efficiency in UWB communication employing an OFDM modulation scheme. A communication device and a wireless communication method are provided.

  A further object of the present invention is to provide an excellent radio communication apparatus and radio capable of detecting interference waves with less power consumption and avoiding interference in consideration of frequency utilization efficiency in UWB communication employing an OFDM modulation scheme. It is to provide a communication method.

The present invention has been made in consideration of the above problems, and is a wireless communication apparatus that transmits and receives a multicarrier signal composed of a plurality of subcarriers arranged on the frequency axis,
A reception analog circuit unit for analog processing of the received signal;
An analog / digital converter that converts the received signal after analog processing into a digital signal;
An analog level detector for detecting the level of the received analog signal before converting it to a digital signal by the analog / digital converter;
A demodulation processing unit that demodulates the received signal after digital conversion into the original subcarriers;
A data reproduction unit that reproduces received data from the demodulated multicarrier signal;
A transmission data generation unit for generating transmission data;
A modulation processing unit that modulates transmission data into a multicarrier transmission signal composed of a plurality of subcarriers;
A digital / analog converter that converts the modulated transmission signal into an analog signal;
A transmission analog circuit unit for analog processing of the transmission signal after analog conversion;
A communication operation control unit that controls transmission and reception operations is provided.
The communication operation control unit checks the presence or absence of a transmission signal from another communication system based on the detection result in the analog level detection unit before starting the data transmission operation.
This is a wireless communication device.

  In recent years, UWB communication using a very wide frequency band is expected as a wireless communication system realizing near-field ultra-high-speed transmission, and standardization work has been carried out for a multiband OFDM communication system that employs an OFDM modulation method and performs frequency hopping It is.

  On the other hand, in order to mitigate the interference level to other systems caused by the UWB transmission wave, it is checked whether there is a transmission signal of another system in the UWB transmission band, and if it exists, the UWB transmission wave is below a certain level (weak) Detect and Avoid (DAA) mechanism is essential for output at a certain level.

  Usually, the signal of another system that is a problem in DAA is a narrowband signal, and the influence of the UWB communication system on the other system is only a part of the use band. Accordingly, it is preferable to selectively lower the UWB output level below a specified level only for the frequency band in which a signal is detected from the viewpoint of frequency utilization efficiency, and as a high-speed communication method. For example, the communication terminal can perform DAA determination by A / D converting the received signal in the receiving system and then calculating the signal level with a digital circuit. If frequency detection means such as FFT or wavelet transformer in a digital circuit is used, a narrowband signal is detected in units of subcarriers, and in the transmission system, a cutout is made only in the frequency band in which the transmission signal of another system is detected. Thus, UWB communication that avoids interference with other systems can be performed.

  However, signal level detection by a digital circuit has a problem that a large amount of arithmetic processing such as many multipliers is required. In the case of a system using a wide band such as UWB communication, if the FFT or wavelet converter is fully operated over the entire band, the power consumption increases, and the burden is excessive as preprocessing for data transmission. In a wide-band system such as UWB, when a received signal level is detected by a digital circuit, electric power ranging from several millimeters to several tens of milliwatts may be required.

  On the other hand, in the wireless communication device according to the present invention, the analog level detector detects the level of the received analog signal before digitally converting the received analog signal, so that the transmission signal from another communication system is detected. The presence is checked. Such an analog level detector can be arranged on the same silicon chip as the receiving circuit at low cost, and can be configured with power consumption of about several tens of microwatts. Therefore, since the operation of the digital circuit is not performed when performing DAA determination, it is possible to suppress the consumption of extra power during signal detection.

  Further, when an interference wave (that is, interference) from another communication system is detected by the analog level detection unit, a digital circuit having a frequency selection function such as FFT or wavelet transform is further driven and based on the result of OFDM demodulation. The DAA is determined. As a result, the presence of a narrowband signal that becomes an interference wave can be detected in units of subcarriers. In the transmission system, instead of lowering the transmission output for one OFDM symbol as a whole, notching is performed only in the frequency band in which the transmission signal of the other system is detected, and UWB communication is performed, thereby avoiding interference with good frequency utilization efficiency. Can be realized. For example, it is possible to cut out a specific subcarrier in the multicarrier signal by means such as spectrum shaping.

  On the other hand, when an interference wave from another communication system is not detected by the analog level detection unit, a data transmission operation is started according to the DAA determination result. That is, it is not necessary to drive a digital circuit having a frequency selection function such as FFT or wavelet transform to detect an interference wave, and it is possible to suppress the consumption of extra power during signal detection.

  Here, the analog level detection unit includes a detector that rectifies an arbitrary signal within a frequency band used for transmission and reception, a low-frequency pass filter that converts the output of the detector into a DC signal, and a DC signal that is a predetermined signal. The comparator can be configured to compare with the reference level, and the level of the received analog signal can be detected based on the comparison result. Further, a reference level to be given to the comparator is set according to any of gain, thermal noise change, or frequency characteristic of the propagation path that the reception analog circuit section has when detecting a transmission signal from another communication system. It may be.

  Advantageous Effects of Invention According to the present invention, in UWB communication employing an OFDM modulation scheme, excellent wireless communication that can suitably perform communication while avoiding interference with narrowband signals of other systems in consideration of frequency utilization efficiency. An apparatus and a wireless communication method can be provided.

  Further, according to the present invention, in UWB communication adopting the OFDM modulation scheme, an excellent radio communication apparatus and radio that can detect an interference wave with less power consumption and perform interference avoidance considering frequency utilization efficiency A communication method can be provided.

  According to the wireless communication apparatus of the present invention, since the operation of the digital circuit is not performed when performing DAA determination, it is possible to suppress the consumption of extra power during signal detection. On the other hand, once a jamming wave is detected, a digital circuit having a frequency selection function such as FFT or wavelet transform is driven, and DAA is determined in units of subcarriers based on the result of OFDM demodulation. High interference avoidance operation can be performed.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The present invention relates to a wireless communication apparatus that performs UWB communication adopting an OFDM modulation scheme, and specifically, a plurality of bands each having a bandwidth of 3.1 GHz to 10.6 GHz defined by the FCC and each having a width of 528 MHz. It is possible to perform multiband OFDM communication by dividing the subbands and performing frequency hopping (FH) between the subbands.

  The wireless communication apparatus according to the present invention introduces a DAA mechanism in order to mitigate the interference level to other systems caused by UWB transmission waves, and checks whether transmission signals of other systems exist within the UWB transmission band. Data transmission is started after inspection.

  FIG. 1 shows a configuration of a wireless communication apparatus according to an embodiment of the present invention. In the illustrated wireless communication apparatus 1, a transmission / reception shared antenna 2 is shared by a reception system and a transmission system via an antenna switch 3, and a transmission / reception operation is controlled by a communication operation control unit 31.

  The reception system includes a reception analog circuit unit that performs analog processing on the reception signal, an analog / digital converter 15 that converts the reception signal after the analog processing into a digital signal, and an analog level that detects the level of the reception analog signal. It comprises a detection circuit 20 and a reception digital circuit section that processes a digitally converted reception signal.

  The reception analog circuit unit includes a low noise amplifier (LNA) 11, a frequency converter 12, a frequency selection unit 13, and a gain adjustment unit 14. The received signal from the antenna 2 is amplified by the low noise amplifier 11, then down-converted by the frequency conversion unit 12 by multiplying by the local frequency, the signal outside the UWB band is removed by the frequency selection unit 13, and the gain adjustment unit 14. Is adjusted to an appropriate signal level.

  The reception digital circuit unit includes an FFT 16, performs fast Fourier transform on the reception signal digitally converted by the analog / digital converter 15, converts a time-axis signal into a frequency-axis signal, and modulates each subcarrier. Demodulation corresponding to the system is performed, and parallel / serial conversion is performed to reproduce the information sent as the original serial signal. A wavelet transformer may be provided instead of the FFT.

  The analog level detection circuit 20 detects the level of the received analog signal immediately before being input to the analog / digital converter 15. In this embodiment, the analog level detection circuit 20 includes a detector 21, a low-frequency pass filter 22, and a comparator 23, and rectifies an arbitrary signal within a frequency band used for transmission / reception by the detector 21. The output is converted into a DC signal by the low-pass filter 22, and the comparator 23 compares the DC signal with a predetermined reference level, whereby the level of the received analog signal can be detected. At this time, the reference level setting unit 24 compares the comparator 23 according to any one of the gain of the reception analog circuit unit, the change of thermal noise, or the frequency characteristic of the propagation path when detecting a transmission signal from another communication system. The reference level to be given to is set.

  The analog level detection circuit 20 can be arranged at low cost on the same silicon chip as the reception circuit, and can be configured with power consumption of about several tens of microwatts. On the other hand, in a wide-band system such as UWB, when a received signal level is detected by a digital circuit, it may require power ranging from several millimeters to several tens of milliwatts, and a narrow band that rarely exists. It is a heavy burden to detect a signal.

  The transmission system includes a transmission digital circuit unit that digitally processes transmission data, a digital / analog converter 45, and a transmission analog circuit unit that performs analog processing of transmission signals.

  The transmission digital circuit unit assigns the transmission data signal generated by the transmission data generation unit 47 to a plurality of subcarriers, modulates the amplitude and phase for each subcarrier, and performs inverse fast Fourier transform on the plurality of subcarriers by the IFFT 46. The signal is converted into a time axis signal while maintaining the orthogonality of each subcarrier.

  The digital / analog converter 45 converts the transmission data signal after the modulation processing into an analog signal.

  The transmission analog circuit unit includes a frequency selection unit 44, a gain adjustment unit 43, a frequency converter 42, and a high output amplifier (PA) 41. The transmission signal converted into the analog signal is removed from the signal component other than the desired band by the frequency selection unit 44, adjusted to an appropriate signal level by the gain adjustment unit 43, up-converted by the frequency converter 42, and a high output amplifier The transmission power is amplified by 41 and output from the antenna 2 via the antenna switch 3.

  In this embodiment, a DAA mechanism is introduced to mitigate the level of interference with other systems caused by UWB transmission waves. For this reason, the communication operation control unit 31 starts the data transmission operation after checking whether or not there is a transmission signal of another system in the UWB transmission band at the time of data transmission.

  By performing frequency inspection based on the output of the FFT 16 or wavelet transformer, it is possible to detect a narrowband signal from another system in units of subcarriers. However, in a wide-band system such as UWB, when a received signal level is detected by a digital circuit, electric power in the range of several millimeters to several tens of milliwatts may be required. In view of the fact that there is often no interference wave consisting of narrowband signals, the operation of this type of digital circuit for the purpose of mere signal detection rather than data transmission is not cost-effective.

  On the other hand, in the present embodiment, the analog level detection circuit 20 detects the level of a received analog signal immediately before being input to the analog / digital converter 15 to check whether there is a transmission signal from another communication system. Like to do. The analog level detection circuit 20 can be arranged at low cost on the same silicon chip as the receiving circuit, and can be configured with power consumption of about several tens of microwatts (described above). Therefore, the communication operation control unit 31 can suppress the consumption of excess power during signal detection by performing the DAA determination without operating the digital circuit.

  When the analog level detection circuit 20 detects an interference wave (that is, interference) from another communication system, the communication operation control unit 31 drives the reception digital circuit unit for signal detection, and performs an FFT 16 By performing fast Fourier transform (or wavelet transform), DAA determination operation utilizing frequency selection is performed. That is, based on the result of OFDM demodulation, the presence of a narrowband signal that becomes an interference wave is detected in units of subcarriers.

  Then, the communication operation control unit 31 performs UWB communication with the transmission system by notching only the frequency band in which the transmission signal of the other system is detected, instead of lowering the transmission output level over the entire OFDM symbol. By doing so, interference avoidance with high frequency utilization efficiency is realized. For example, it is possible to cut out a specific subcarrier in the multicarrier signal by means such as spectrum shaping. Alternatively, by subtracting the delayed signal generated by delaying the signal by 1 / f second from the signal made up of the impulse signal sequence and generating the subtraction signal, and transmitting this subtraction signal, the frequency at which the narrowband signal exists The interference in the band f can be reduced (for example, refer to Japanese Patent Laid-Open No. 2002-335188).

  On the other hand, when no interference wave from another communication system is detected by the analog level detection circuit 20, the communication operation control unit 31 immediately starts the data transmission operation according to the DAA determination result.

  Therefore, since a digital circuit having a frequency selection function such as FFT or wavelet transform is not driven to detect an interference wave, it is possible to suppress the consumption of extra power during signal detection. Signal detection by the analog level detection circuit 20 requires power consumption of about several tens of microwatts. On the other hand, in a wideband system such as UWB, when a received signal level is detected by a digital circuit, power ranging from several millimeters to several tens of milliwatts is required (described above).

  As described above, the reference level setting unit 24 sets the reference level to be supplied to the comparator 23 in the analog level detection circuit 20. In general, there is no problem if the reference level is set to a certain gain determined in advance by the gain adjusting unit 14 and fixed to a certain appropriate level corresponding to the gain value. However, when the analog part is saturated due to the extremely high level of the narrowband signal in question, it is assumed that it is necessary to change the gain setting as a receiver to avoid malfunction of the analog circuit. The In this case, the reference level needs to be changed to an appropriate value based on the gain setting of the gain adjusting unit 14. It is desirable that the reference level setting unit 24 is automatically set to an optimum level based on the gain set by the reception gain adjusting unit 14. FIG. 2 schematically shows a circuit configuration for generating a reference level from gain setting information using a digital / analog converter.

  FIG. 3 shows an operation procedure for the wireless communication apparatus 1 according to the present embodiment to start a data transmission operation based on the DAA determination result in the form of a flowchart.

  When a data transmission request is generated from the upper layer of the communication protocol in the wireless communication device 1, first, the analog level detection circuit 20 is activated (step S1), and the reception analog immediately before being input to the analog / digital converter 15 is processed. The signal level is checked (step S2).

  Here, when the interference level from another communication system is not detected by the analog level detection circuit 20 (No in step S2), the communication operation control unit 31 immediately starts the data transmission operation according to the DAA determination result. (Step S6).

  On the other hand, when an interference wave from another communication system is detected by the analog level detection circuit 20 (Yes in step S2), the reception digital circuit unit is subsequently driven for signal detection, and fast Fourier transform is performed by the FFT 16. By performing transformation (or wavelet transformation), DAA determination operation using frequency selection is performed (step S3).

  As a result of the DAA determination by the frequency selection action of the digital circuit, the presence of a narrowband signal that becomes an interference wave is detected in subcarrier units (step S5). Then, the communication operation control unit 31 causes the transmission system to perform UWB communication by notching the frequency band in which the transmission signal of the other system is detected (step S6).

  FIG. 4 shows a timing chart in which the wireless communication apparatus 1 according to this embodiment performs a data transmission operation based on the DAA determination result.

  FIG. 4A shows a timing chart when the analog level detection circuit 20 does not detect an interference wave from another communication system and starts the data transmission operation immediately according to the DAA determination result. In this case, normal OFDM transmission using the entire band (Full Band) is started without starting the FFT operation. In most cases, it is assumed that the data transmission operation is started immediately according to the DAA determination result.

  FIG. 4B shows a timing chart when an interference wave from another communication system is detected by the analog level detection circuit 20. In this case, the reception digital circuit unit is further driven for signal detection, and the data transmission operation is performed after performing the DAA determination operation using the frequency selection effect by performing the FFT. Then, UWB communication is performed by notching the frequency band in which the transmission signal of the other system is detected, not the entire band (Full Band) of one OFDM symbol.

  Comparing FIG. 4 with the conventional example shown in FIG. 8, when a narrow-band signal is present, the detection is delayed by the analog detection time by the amount that the analog circuit level detection is preceded (see FIG. 4B). ) The time required for the analog detection is mainly determined by the time constant of the low-pass filter in the analog level detector 20, but in order to filter the signal over 500 MHz (for one symbol) as in this embodiment. Therefore, it is considered that desired characteristics can be obtained if it takes several microseconds at most. Further, in many cases, it is considered that there is no narrowband signal in the UWB band, so that there is a great merit that the level detection procedure by the digital circuit can be omitted as shown in FIG. 4A.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  In this specification, the embodiment applied to the OFDM_UWB communication adopting the multiband method has been mainly described, but the gist of the present invention is not limited to this. The present invention can be similarly applied to a wireless communication apparatus adopting an OFDM modulation scheme other than UWB communication, or a wireless communication apparatus employing a multicarrier transmission scheme other than OFDM.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram illustrating a configuration of a wireless communication apparatus according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing a circuit configuration for generating a reference level from gain setting information using a digital / analog converter. FIG. 3 is a flowchart showing an operation procedure for starting a data transmission operation based on the DAA determination result. FIG. 4A is a diagram illustrating a timing chart of a transmission operation in a case where an interference wave from another communication system is not detected and a data transmission operation is immediately started (Dominant case). FIG. 4B is a diagram illustrating a timing chart of a transmission operation when an interference wave from another communication system is detected (non-dominant case). FIG. 5 is a diagram showing an example of frequency allocation defined in the OFDM_UWB communication system employing multiband. FIG. 6 is a diagram illustrating a state in which data transmission is performed while performing frequency hopping on an OFDM symbol in the time axis in the multiband OFDM scheme. FIG. 7 shows a state in which UWB communication is performed using other frequency bands while notching only the frequency band in which the transmission signal of the other system is detected to avoid interference with the other system. FIG. FIG. 8 is a timing chart for performing DAA determination in units of subcarriers based on the result of OFDM demodulation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wireless communication apparatus 2 ... Antenna 3 ... Antenna switch 11 ... Low noise amplifier 12 ... Frequency converter 13 ... Frequency selection part 14 ... Gain adjustment part 15 ... Analog / digital converter 16 ... FFT
DESCRIPTION OF SYMBOLS 17 ... Data reproduction part 20 ... Analog level detection circuit 21 ... Detector 22 ... Low-pass filter 23 ... Comparator 24 ... Reference level setting device 31 ... Communication operation control part 41 ... High output amplifier 42 ... Frequency converter 43 ... Gain adjusting unit 44 ... frequency selecting unit 45 ... digital / analog converter 46 ... IFFT
47 ... Transmission data generation unit

Claims (10)

A wireless communication device for transmitting and receiving a multicarrier signal composed of a plurality of subcarriers arranged on a frequency axis,
A reception analog circuit unit for analog processing of the received signal;
An analog / digital converter that converts the received signal after analog processing into a digital signal;
An analog level detector for detecting the level of the received analog signal before converting it to a digital signal by the analog / digital converter;
A demodulation processing unit that demodulates the received signal after digital conversion into the original subcarriers;
A data reproduction unit that reproduces received data from the demodulated multicarrier signal;
A transmission data generation unit for generating transmission data;
A modulation processing unit that modulates transmission data into a multicarrier transmission signal composed of a plurality of subcarriers;
A digital / analog converter that converts the modulated transmission signal into an analog signal;
A transmission analog circuit unit for analog processing of the transmission signal after analog conversion;
A communication operation control unit that controls transmission and reception operations is provided.
The communication operation control unit checks the presence or absence of a transmission signal from another communication system based on the detection result in the analog level detection unit before starting the data transmission operation.
A wireless communication apparatus. When the analog level detection unit detects a transmission signal from another communication system, the communication operation control unit further converts the received analog signal into a digital signal by the analog / digital conversion unit and demodulates by the demodulation processing unit. Process to identify the frequency band in which the transmitted signal exists,
The wireless communication apparatus according to claim 1. The communication operation control unit causes the modulation processing unit to perform transmission data modulation processing except for subcarriers in a frequency band in which a transmission signal from another communication system is detected;
The wireless communication apparatus according to claim 2. The analog level detector is
A detector for rectifying an arbitrary signal in a frequency band used for transmission and reception;
A low-frequency pass filter that converts the output of the detector into a DC signal;
A comparator for comparing the DC signal with a predetermined reference level;
Based on the comparison result, the level of the received analog signal is detected.
The wireless communication apparatus according to claim 1. A reference level for setting a reference level to be given to the comparator according to any of gain, thermal noise change, or propagation path frequency characteristics of the reception analog circuit unit when detecting a transmission signal from another communication system Further comprising setting means,
The wireless communication apparatus according to claim 1. A wireless communication method for transmitting and receiving a multicarrier signal composed of a plurality of subcarriers arranged on a frequency axis, before starting a data transmission operation,
A reception analog processing step for analog processing of the received signal;
An analog level detection step for detecting the level of the received analog signal;
Based on the detection result in the analog level detection step, an interference wave determination step for determining the presence or absence of a transmission signal from another communication system,
In response to determining that there is a transmission signal from another communication system, an analog / digital conversion step of converting the received signal after analog processing into a digital signal;
A demodulation processing step for demodulating the received signal after digital conversion into the original subcarriers;
A frequency inspection step for identifying a frequency band in which an interfering wave exists from the demodulated signal;
The wireless communication method characterized by performing. A data transmission step of performing data transmission processing by performing modulation processing of transmission data except for subcarriers in a frequency band in which a transmission signal from another communication system is detected in the frequency inspection step;
The wireless communication method according to claim 6. In response to determining that there is no transmission signal from another communication system in the interference wave determination step, the method further includes a data transmission step of performing data transmission.
The wireless communication method according to claim 6. In the analog level detection step,
After rectifying an arbitrary signal in the frequency band used for transmission / reception, it passes only in the low frequency band and converts it to a DC signal, and the level of the received analog signal is detected by comparing the DC signal with a predetermined reference level. ,
The wireless communication method according to claim 6. The reference level is set according to any of the gain in the reception analog processing step when detecting a transmission signal from another communication system, a change in thermal noise, or a frequency characteristic of the propagation path.
The wireless communication method according to claim 9.

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