JP2010041446A - Radio device and method of modulating signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio device resistant to interference from another system having an adjacent operating frequency band. <P>SOLUTION: The radio device applies a first modulation system (for example, 16QAM) to subcarriers other than a predetermined number of subcarriers at both ends of a channel band, and transmits and/or receives a signal modulated in an OFDM modulation system applying a second modulation system (for example, QPSK) having noise resistance higher than that of the first modulation system to the predetermined number of subcarriers at both ends of the channel band. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio apparatus that transmits and / or receives a signal modulated by a multicarrier modulation method and a signal modulation method that modulates a signal by a multicarrier modulation method.

  ITS (Intelligent Transport Systems) inter-vehicle communication system, scheduled to start in 2012, is one of its applications, such as intersections with poor outlooks by notifying other vehicles of out-of-sight locations. Encounter vehicle collision accident prevention is considered, and the 720 MHz band will be used. As shown in FIG. 1, the use frequency band of the digital terrestrial television broadcasting system is adjacent to the end of the use frequency band low frequency side of the ITS inter-vehicle communication system with the guard band of 5 MHz interposed therebetween. A frequency band used for electrical communication is adjacent to the end of the system on the high frequency side with a guard band of 5 MHz.

JP 2002-247004 A JP 2006-186630 A

  As described above, since the frequency bands of other systems are adjacent to both ends of the frequency band of the ITS inter-vehicle communication system, interference (giving interference) from the ITS inter-vehicle communication system side to the adjacent other system is reduced. In addition, it is an important issue in the ITS inter-vehicle communication system to be strong against interference (interfered) from the other adjacent systems to the ITS inter-vehicle communication system.

  Here, in Patent Document 1, in order to reduce adjacent interference (giving interference), there is a digital transmission device of a multicarrier modulation system in which a small level subcarrier exists at at least one end of a transmission channel band. Proposed.

  However, the multicarrier modulation type digital transmission apparatus proposed in Patent Document 1 can reduce adjacent interference (interference), but it is caused by a decrease in the subcarrier level at at least one end of the transmission channel band. The communication performance of the local system will deteriorate.

  Further, in Patent Document 2, in order to optimize both transmission throughput and transmission power, based on the propagation path estimation result, a combination of subcarriers and modulation schemes or coding rates is used per unit bit. A subcarrier adaptive control method has been proposed in which transmission power is allocated efficiently while maximizing the total number of transmittable bits by selecting in order from the combination with the smallest required transmission power.

  However, the subcarrier adaptive control method proposed in Patent Document 2 can improve the transmission throughput of the entire system and reduce interference with other cells in a wireless service composed of a plurality of cells using the same frequency, for example. However, when considering on the frequency axis, it is a method of reducing power and reducing interference over the entire frequency being used, so the interference power to other systems adjacent to the frequency band used can be efficiently reduced. It cannot be reduced.

  In addition, although the problem in the ITS inter-vehicle communication system has been described above, a wireless system other than the ITS inter-vehicle communication system in which the use frequency band of another system is adjacent to both ends of the use frequency band or one end of the use frequency band. Even in a wireless system in which the frequency band of another system is adjacent to each other, as in the case of the ITS inter-vehicle communication system, interference (giving interference) from the wireless system side to another system in which the frequency band is adjacent is caused. It is an important issue in the radio system to reduce the frequency band and to make it strong against interference (interference) from the adjacent system to the radio system side.

  In view of the above situation, it is a first object of the present invention to provide a radio apparatus and a signal modulation method that are resistant to interference (interfered) from other systems with adjacent frequency bands.

  Furthermore, in view of the above situation, the present invention provides a radio apparatus and a signal modulation method capable of reducing interference (additional interference) with other systems with adjacent frequency bands while ensuring communication quality of the own system. This is the second purpose.

  In order to achieve the above object, a radio apparatus according to the present invention employs a first modulation scheme for subcarriers other than a predetermined number of subcarriers at one or both ends of a channel band, and at one or both ends of the channel band. A signal modulated by a multi-carrier modulation scheme that employs a second modulation scheme that is stronger in noise resistance than the first modulation scheme for a predetermined number of subcarriers is transmitted and / or received. . When the second modulation method is adopted for a predetermined number of subcarriers at both ends of the channel band, the predetermined number of the low band side end of the channel band and the high band side end of the channel band The predetermined number may be the same number or a different number.

  According to such a configuration, a modulation scheme having high noise resistance is adopted at one or both ends of the channel band where the influence of interference is large, so that the use frequency band is strong against interference (interference) from other systems adjacent to each other. .

  Furthermore, in the multicarrier modulation scheme, the level of a predetermined number of subcarriers at one or both ends of the channel band is set lower than the level of a subcarrier other than the predetermined number of subcarriers at one or both ends of the channel band. Is desirable.

  According to such a configuration, the subcarrier level is reduced at one or both ends of the channel band, which is a major factor of the interference, and therefore, the interference to other systems adjacent to the used frequency band (giving interference) can be reduced. In addition, since a modulation scheme having high noise resistance is used for subcarrier modulation whose level is reduced, the communication quality of the own system can be ensured. That is, it is possible to reduce interference (additional interference) with other systems with adjacent frequency bands while ensuring the communication quality of the own system.

  Further, the second modulation scheme relates to information on a degree of reduction in the level of a predetermined number of subcarriers at one or both ends of the channel band relative to a level of subcarriers other than a predetermined number of subcarriers at one or both ends of the channel band. At least one of the information and the information on the predetermined number may be added to the signal modulated by the multicarrier modulation scheme and transmitted and / or received.

  According to such a configuration, the degree of reduction in the level of the predetermined number of subcarriers at one or both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at one or both ends of the channel band, the second At least one of the modulation method and the predetermined number can be made variable, and adaptive response can be made according to the situation. Further, at least one piece of information related to the first modulation scheme and information related to the number of subcarriers modulated by the first modulation scheme may be added to a signal modulated by the multicarrier modulation scheme. Good. The information about the degree of reduction in the level of the predetermined number of subcarriers at one end or both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at one end or both ends of the channel band includes the one end of the channel band. Alternatively, information on the level of subcarriers other than the predetermined number of subcarriers at both ends and information on the level of a predetermined number of subcarriers at one or both ends of the channel band are included.

  Further, the second modulation scheme relates to information on a degree of reduction in the level of a predetermined number of subcarriers at one or both ends of the channel band relative to a level of subcarriers other than a predetermined number of subcarriers at one or both ends of the channel band. A plurality of combination patterns of information and information related to the predetermined number may be set in advance, and the combination pattern information may be added to a signal modulated by the multi-carrier modulation scheme and transmitted and / or received. .

  According to such a configuration, the information on the degree of reduction of the level of the predetermined number of subcarriers at one or both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at one or both ends of the channel band, Since a plurality of combination patterns of information on the modulation method 2 and information on the predetermined number are set in advance, one pattern can be selected from the plurality of combination patterns, and an adaptive response according to the situation Is possible. Further, the combination pattern may include at least one piece of information among information on the first modulation scheme and information on the number of subcarriers modulated by the first modulation scheme. The information about the degree of reduction in the level of the predetermined number of subcarriers at one end or both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at one end or both ends of the channel band includes the one end of the channel band. Alternatively, information on the level of subcarriers other than the predetermined number of subcarriers at both ends and information on the level of a predetermined number of subcarriers at one or both ends of the channel band are included.

  In order to achieve the above object, a signal modulation method according to the present invention employs a first modulation scheme for subcarriers other than a predetermined number of subcarriers at one or both ends of a channel band, and A signal is modulated by a multi-carrier modulation method that employs a second modulation method having a higher noise resistance than the first modulation method for a predetermined number of subcarriers at both ends.

  According to such a signal modulation method, in a wireless communication system using the signal modulation method, a modulation scheme having high noise resistance is adopted at one or both ends of a channel band that is greatly affected by interference, so that the frequency band to be used is It becomes strong against interference (interfered) from other adjacent systems.

  Furthermore, in the multicarrier modulation scheme, the level of a predetermined number of subcarriers at one or both ends of the channel band is set lower than the level of a subcarrier other than the predetermined number of subcarriers at one or both ends of the channel band. Is desirable.

  According to such a signal modulation method, in the radio communication system using the signal modulation method, the subcarrier level is reduced at one or both ends of the channel band which is a main factor of the interference, so that the used frequency band is adjacent. Interference with other systems (interference) can be reduced, and a highly noise-resistant modulation scheme is adopted for subcarrier modulation whose level is reduced, so that the communication quality of the own system can be ensured. it can. That is, in a wireless communication system using the signal modulation method, it is possible to reduce interference (interference) with other systems adjacent to the used frequency band while ensuring the communication quality of the own system.

  According to the present invention, the first modulation scheme is adopted for subcarriers other than the predetermined number of subcarriers at one or both ends of the channel band, and the predetermined number of subcarriers at one or both ends of the channel band is Since the signal is modulated by the multi-carrier modulation method that employs the second modulation method having higher noise resistance than the first modulation method, the frequency band used for the radio communication system using the modulation signal is adjacent to the frequency band used. It is strong against interference (interference) from the system. Furthermore, in the multicarrier modulation scheme, the level of a predetermined number of subcarriers at one or both ends of the channel band is set lower than the level of a subcarrier other than the predetermined number of subcarriers at one or both ends of the channel band. Thus, while ensuring the communication quality of the radio system using the modulated signal, the use frequency band of the radio communication system using the modulated signal and the interference (interference) with other systems adjacent to the use frequency band can be reduced. it can.

  Embodiments of the present invention will be described below with reference to the drawings. Here, as an example of the wireless device according to the present invention, an in-vehicle wireless communication device used in an ITS inter-vehicle communication system will be described.

  By the way, in the United States, the standard of IEEE802.11p is examined as a standard of inter-vehicle communication. In Japan, although the frequency used in the United States is different (in Japan, 720 MHz band, 5.9 GHz band in the United States), there is a high possibility that a vehicle-to-vehicle communication standard based on the IEEE 802.11p standard will be adopted. Therefore, in describing an in-vehicle wireless communication device used in an ITS inter-vehicle communication system, first, a packet configuration conforming to IEEE 802.11p will be described.

  As shown in FIG. 2, the IEEE802.11p-compliant packet structure viewed from the physical layer is after the physical header consisting of the short training field STF, the long training field LTF, and the signal field SIG. , Followed by physical data DATA. The short training field STF is a field in which information for performing AGC (Automatic Gain Control) control, packet detection, symbol synchronization, and frequency coarse adjustment is described. The long training field LTF is a field in which information for performing fine frequency adjustment and channel estimation is described. The signal field SIG is a field in which information about the transmission rate (modulation method) and packet length of the physical data DATA is BPSK (Binary Phase Shift Keying) modulated. In IEEE802.11p, an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, which is multicarrier modulation, is employed as a modulation method for physical data DATA.

  Next, an in-vehicle wireless communication device that performs ITS inter-vehicle communication will be described. The in-vehicle wireless communication device 100 that performs ITS inter-vehicle communication is installed in the vehicle 200 as shown in FIG.

  As shown in FIG. 4, the in-vehicle wireless communication apparatus 100 includes a serial / parallel converter (S / P converter) 1, a modulator 2, an IFFT (Inverse Fast Fourier Transform) unit 3, a guard interval adding unit 4, and additional processing. A transmission unit including a unit 5, a digital / analog converter (D / A converter) 6, a power amplifier 7, and a physical header processing unit 8.

  Further, as shown in FIG. 4, the in-vehicle wireless communication device 100 includes a switch 9 for switching between transmission and reception, and a transmission / reception antenna 10.

  As shown in FIG. 4, the in-vehicle wireless communication device 100 includes a variable gain amplifier 11, an analog / digital converter (A / D converter) 12, a separation processing unit 13, a guard interval removal unit 14, an FFT (Fast Fourier). Transform) section 15, demodulator 16, parallel / serial converter (P / S converter) 17, and reception section including physical header processing section 18.

  The in-vehicle wireless communication device 100 performs the following operation during transmission. The S / P converter 1 parallelizes transmission data (serial data) and outputs the parallel data to the same number of modulators 2 as the number of subcarriers. The modulator 2 for each subcarrier performs primary modulation and level adjustment for each subcarrier of the output data (parallel data) of the S / P converter 1. The data output from the modulator 2 is secondarily modulated by inverse fast Fourier transform processing by the IFFT unit 3, and then a guard interval is added by the guard interval adding unit 4, and the addition processing unit 5 outputs the data from the physical header processing unit 8. The output physical header is added, converted to an analog signal by the D / A converter 6, power amplified by the power amplifier 7, and transmitted from the transmission / reception antenna 10 via the switch 9.

  The in-vehicle wireless communication device 100 performs the following operation at the time of reception. Received data received by the transmission / reception antenna 10 is level-adjusted by the variable gain amplifier 11 via the switch 9, converted into a digital signal by the A / D conversion unit 12, and physical data and physical header by the separation processing unit 13. The physical data is output to the guard interval removing unit 14, and the physical header is output to the physical header processing unit 18. The physical data output from the separation processing unit 13 is subjected to primary demodulation by fast Fourier transform processing by an FFT (Fast Fourier Transform) unit 15 after the guard interval is removed by the guard interval removal unit 14, and the same number as the number of subcarriers. Secondary demodulated by the demodulator 16. The data secondarily demodulated for each subcarrier by the demodulator 16 for each subcarrier is converted into received data (serial data) by the P / S converter 17.

  Then, the multicarrier modulation method implemented in the vehicle-mounted radio | wireless communication apparatus 100 is demonstrated.

  When taking measures against interference, the in-vehicle wireless communication device 100 implements a multicarrier modulation method as shown in FIG. 5B, for example. In the multicarrier modulation shown in FIG. 5B, primary modulation is performed by 16QAM (Quadrature Amplitude Modulation) on subcarriers other than a predetermined number of subcarriers at both ends of a channel band (band where subcarriers are arranged). This is OFDM modulation in which primary modulation is performed by QPSK (Quadrature Phase Shift Keying), which is stronger in noise resistance than 16QAM, for a predetermined number of subcarriers at both ends of the channel band.

  In this case, among the same number of modulators 2 as the number of subcarriers, those corresponding to subcarriers other than the predetermined number of subcarriers at both ends of the channel band are modulators that perform 16QAM modulation, and predetermined modulators at both ends of the channel band are used. The one corresponding to the number of subcarriers is a modulator that performs QPSK modulation. Correspondingly, among the same number of demodulators 16 as the number of subcarriers, those corresponding to subcarriers other than the predetermined number of subcarriers at both ends of the channel band are demodulators that perform 16QAM demodulation, and the channel The one corresponding to a predetermined number of subcarriers at both ends of the band is a demodulator that performs QPSK demodulation.

  The multi-carrier modulation method as shown in FIG. 5B employs a modulation scheme (QPSK in this case) having high noise resistance at both ends of the channel band where the influence of interference is large. Compared with such a conventional multicarrier modulation method, the used frequency band is more resistant to interference (interfered) from other adjacent systems.

  When taking measures against interference, the in-vehicle wireless communication device 100 implements a multicarrier modulation method as shown in FIG. 6C, for example. The multicarrier modulation shown in FIG. 6 (c) performs primary modulation with 16QAM on subcarriers other than a predetermined number of subcarriers at both ends of a channel band (band in which subcarriers are arranged), and Primary modulation is performed on a predetermined number of subcarriers at both ends by QPSK, which is stronger in noise resistance than 16QAM, and the level of the predetermined number of subcarriers at both ends of the channel band is set to a predetermined number of subcarriers at both ends of the channel band. The OFDM modulation is set to ½ of the level of other subcarriers.

  In this case, among the same number of modulators 2 as the number of subcarriers, those corresponding to subcarriers other than the predetermined number of subcarriers at both ends of the channel band are modulators that perform 16QAM modulation, and predetermined modulators at both ends of the channel band are used. The one corresponding to the number of subcarriers is a modulator that performs QPSK modulation, and the level adjustment for each subcarrier by the modulator 2 for each subcarrier causes the level of a predetermined number of subcarriers at both ends of the channel band to be The level is set to ½ of the level of subcarriers other than the predetermined number of subcarriers at both ends of the channel band. Correspondingly, among the same number of demodulators 16 as the number of subcarriers, those corresponding to subcarriers other than the predetermined number of subcarriers at both ends of the channel band are demodulators that perform 16QAM demodulation, and the channel The one corresponding to a predetermined number of subcarriers at both ends of the band is a demodulator that performs QPSK demodulation.

  In the multicarrier modulation method as shown in FIG. 6C, the subcarrier level is reduced at both ends of the channel band, which is a major factor of the interference, so that the conventional multicarrier as shown in FIG. Compared to the modulation method, it is possible to reduce interference (addition interference) to other systems adjacent to the frequency band used, and a modulation scheme (here, QPSK) that is strong in noise resistance to subcarrier modulation whose level is reduced. Since it is adopted, the communication quality can be improved as compared with the conventional multicarrier modulation method (method proposed in Patent Document 1) as shown in FIG.

  In the multicarrier modulation shown in FIG. 5 (b) and the multicarrier modulation shown in FIG. 6 (c), the number of subcarriers at both ends of the channel band (band in which the subcarriers are arranged) is the lower end. However, it may be a different number (including the case where one is zero). For example, when taking countermeasures against interference, multi-carrier modulation as shown in FIGS. 7A and 7B may be used, and when taking countermeasures against interference as shown in FIGS. 8A and 8B. Multi-carrier modulation may be used.

  5 to 8 described above are diagrams showing the spectrum of the portion of the physical data DATA (see FIG. 2) when the packet is basically observed from the time axis.

  In the multicarrier modulation method shown in FIG. 6 (c) and FIGS. 8 (a) and 8 (b), which are implemented when countermeasures against interference are performed, subcarriers at the end of the channel band are compared with the physical data DATA portion. It is indispensable to reduce the level of noise and adopt a modulation scheme that is resistant to noise. Further, as an extended version of multicarrier modulation performed when countermeasures against interference are taken, the subcarrier level reduction at the end of the channel band is performed not only in the physical data DATA part but also in the signal field SIG (see FIG. 2). Various methods such as a method of extending to a long training field LTF (see FIG. 2) or a method of extending to a short training field STF (see FIG. 2) are conceivable.

  On the other hand, in the multicarrier modulation method shown in FIG. 5B and FIG. 7A and FIG. 7B implemented when countermeasures against interference are performed, the end of the channel band is only applied to the physical data DATA portion. Adopt a modulation method that is resistant to noise. There is no way to extend to the physical header (signal field SIG, long training field LTF, short training field STF) as in the case of taking countermeasures against interference.

  By the way, in the conventional signal field SIG (see FIG. 2), as described above, information on the transmission rate (modulation method) of physical data DATA and packet length is described. However, when the multicarrier modulation method shown in FIG. 6 (c) and FIGS. 8 (a) and (b) and the multicarrier modulation method shown in FIGS. 5 (b), 7 (a) and (b) are implemented. Information on the degree of reduction of the level of the predetermined number of subcarriers at both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at both ends of the channel band, modulation of the predetermined number of subcarriers at both ends of the channel band The channel with respect to the level of subcarriers other than the predetermined number of subcarriers at both ends of the channel band, wherein at least one information among the information regarding the second modulation scheme used for the information and the information regarding the predetermined number is described in a physical header Degree of reduction of the level of a predetermined number of subcarriers at both ends of the band, the second modulation scheme, and the predetermined number To enable changing at least one needs to be described separately in a region different from the conventional signal field SIG. This is because in the conventional signal field SIG compliant with IEEE 802.11p, there is only one reserved bit. Note that information on the degree of reduction of the level of the predetermined number of subcarriers at both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at both ends of the channel band, information regarding the second modulation scheme, and the predetermined In addition to at least one piece of information on the number of channels, the information is modulated by information on the first modulation scheme used for modulation of subcarriers other than a predetermined number of subcarriers at both ends of the channel band and the first modulation scheme. At least one piece of information related to the number of subcarriers may be separately described in a region different from the conventional signal field SIG.

  As specific examples described separately in the above-described region different from the conventional signal field SIG, there are three examples shown in FIGS. 9A to 9C.

  FIG. 9A is a diagram showing a packet configuration when an extended signal field SIG ′ including a conventional signal field SIG compliant with IEEE802.11p is set. This extended signal field SIG ′ includes not only the conventional transmission rate and packet length, but also a predetermined number of subcarriers at both ends of the channel band with respect to subcarrier levels other than the predetermined number of subcarriers at both ends of the channel band. At least one of information on the degree of level reduction, information on a second modulation scheme used for modulation of a predetermined number of subcarriers at both ends of the channel band, and information on the predetermined number.

  FIG. 9B shows a packet configuration when the reserved bit of the conventional signal field SIG compliant with IEEE802.11p is used, and when the reserved bit is set, the information of the second signal field SIG2 is read. FIG. In this case, the conventional signal field SIG conforming to IEEE802.11p is not changed at all, but the second signal field SIG2 includes the channel band corresponding to the subcarrier level other than the predetermined number of subcarriers at both ends of the channel band. At least one of information on the degree of reduction of the level of the predetermined number of subcarriers at both ends of the channel, information on the second modulation scheme used for modulation of the predetermined number of subcarriers at both ends of the channel band, and information on the predetermined number of subcarriers Information is described.

  FIG. 9C shows the same configuration as a conventional packet compliant with IEEE802.11p, but information on the transmission rate (modulation method) of physical data DATA described in the signal field SIG (hereinafter, rate information). )). The rate information described in the conventional signal field SIG has 4 bits and can express 16 types. However, since there are actually 8 types of allocation as shown in FIG. As shown in FIG. 10B, the degree of reduction of the level of the predetermined number of subcarriers at one or both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at one or both ends of the channel band. The information is assigned to a combination pattern of information, information on a second modulation scheme used for modulation of a predetermined number of subcarriers at both ends of the channel band, and information on the predetermined number. Eight combinations that are considered to be effective are set in advance. An example of the setting is shown in FIGS. 11A and 11B. In the setting examples of FIGS. 11A and 11B, the combination pattern includes information on a first modulation scheme used for modulation of subcarriers other than a predetermined number of subcarriers at both ends of the channel band, and the first modulation scheme. Information about the number of subcarriers to be modulated is also included. Each of the combination patterns can be said to indicate a transmission rate in a certain sense.

  For example, when the combination pattern setting shown in FIGS. 11A and 11B is adopted, the in-vehicle wireless communication device 100 is configured as shown in FIG. 12, and 10 modulators out of the same number of modulators 2 as the number of subcarriers are QPSK modulated. The other modulators may perform 16QAM modulation, and among the same number of demodulators 16 as the number of subcarriers, 10 demodulators may perform QPSK demodulation and the other demodulators may perform 16QAM modulation. In FIG. 12, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The configuration shown in FIG. 12 is a configuration in which a combination pattern selection unit 19 and a combination pattern determination unit 20 are added to the configuration shown in FIG.

  The combination pattern selection unit 19 selects one of the eight combination patterns shown in FIG. 11A and FIG. 11B, controls the modulator 2 according to the selection result, determines the level for each subcarrier, and It is determined which modulator is assigned to the subcarrier, and the modulation scheme for each subcarrier is also determined. The combination pattern selection unit 19 also outputs the selection result to the physical header processing unit 8. Based on the output of the combination pattern selection unit 19, the physical header processing unit 8 describes information on the selected combination pattern in the signal field SIG.

  Based on the output of the physical header processing unit 18, the combination pattern determination unit 20 determines a combination pattern used for transmission of received data, and controls the demodulator 16 according to the determination result to determine which subcarrier. Which demodulator is assigned to each subcarrier is determined to determine a demodulation method for each subcarrier.

  Further, the degree of reduction of the level of the predetermined number of subcarriers at both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at both ends of the channel band, and modulation of the predetermined number of subcarriers at both ends of the channel band. Various parameters of the signal modulation method according to the present invention, such as the second modulation method used and the predetermined number, may be adaptively changed according to the situation. For example, in the in-vehicle wireless communication device 100 having the configuration shown in FIG. 12, communication with other systems (terrestrial digital television broadcasting system and telecommunication system) at the current position of the host vehicle 200 (see FIG. 3) by road-to-vehicle communication or the like. The combination pattern selection unit 19 receives the interference state from the interference state grasping unit that grasps the interference state (interference state and interference state), and the combination pattern selection unit 19 selects the combination pattern according to the interference state. It may be.

  In the above-described embodiment, the in-vehicle wireless communication device used in the ITS inter-vehicle communication system has been described as an example. However, the ITS in which the use frequency band of another system is adjacent to both ends of the use frequency band. The present invention can also be applied to a radio apparatus used in a radio system other than the inter-vehicle communication system or a radio system in which the use frequency band of another system is adjacent to only one end of the use frequency band.

  The present invention can be applied not only to a wireless device (transmission / reception device) that performs transmission and reception, but also to a wireless device (transmission device) that performs only transmission and a wireless device (reception device) that performs only reception. Further, the present invention can be applied not only to OFDM modulation but also to other multicarrier modulation.

These are figures which show the frequency allocation around 720 MHz in Japan. These are the figures which show the packet structure (simplified version) based on IEEE802.11p seen from the physical layer. These are figures which show the state by which the vehicle-mounted radio | wireless communication apparatus which performs ITS inter-vehicle communication was mounted in the vehicle. These are figures which show schematic structure of the vehicle-mounted radio | wireless communication apparatus which performs ITS vehicle-to-vehicle communication. These are the figures which show the outline | summary of the modulation method based on this invention which is an example of the conventional modulation method and an interference countermeasure. These are the figures which show the outline | summary of the modulation method based on this invention which is an example of the conventional modulation method and an interference countermeasure. These are the figures which show the outline | summary of the modulation method which concerns on this invention which is another example of a countermeasure against interference. These are figures which show the outline | summary of the modulation method which concerns on this invention which is another example of an interference countermeasure. These are figures which show the example of the packet structure (simplified version) seen from the physical layer. FIG. 5 is a diagram illustrating an example of data assignment in a signal field. These are figures which show the example of a combination pattern in the modulation system of this invention. These are figures which show the example of a combination pattern in the modulation system of this invention. These are figures which show the other schematic structure of the vehicle-mounted radio | wireless communication apparatus which performs ITS vehicle-to-vehicle communication.

Explanation of symbols

1 Serial / parallel converter (S / P converter)
2 Modulator 3 IFFT unit 4 Guard interval addition unit 5 Additional processing unit 6 Digital / analog converter (D / A converter)
7 Power Amplifier 8 Physical Header Processing Unit 9 Switch 10 Transmit / Receive Antenna 11 Variable Gain Amplifier 12 Analog / Digital Converter (A / D Converter)
13 Separation Processing Unit 14 Guard Interval Removal Unit 15 FFT Unit 16 Demodulator 17 Parallel / Serial Converter (P / S Converter)
DESCRIPTION OF SYMBOLS 18 Physical header process part 19 Combination pattern selection part 20 Combination pattern determination part 100 Vehicle-mounted radio | wireless communication apparatus which performs ITS inter-vehicle communication 200 Vehicle

Claims (6)

  A first modulation scheme is adopted for subcarriers other than a predetermined number of subcarriers at one or both ends of a channel band, and the first modulation scheme is applied to a predetermined number of subcarriers at one or both ends of the channel band. A radio apparatus that transmits and / or receives a signal modulated by a multi-carrier modulation scheme that employs a second modulation scheme that has higher noise tolerance. In the multicarrier modulation scheme,
The level of a predetermined number of subcarriers at one or both ends of the channel band,
The radio apparatus according to claim 1, wherein the level is lower than a level of a subcarrier other than a predetermined number of subcarriers at one or both ends of the channel band.   Information on the degree of reduction of the level of a predetermined number of subcarriers at one or both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at one or both ends of the channel band, information regarding the second modulation scheme, The radio apparatus according to claim 1, wherein at least one piece of information relating to the predetermined number is transmitted and / or received by being added to a signal modulated by the multicarrier modulation scheme.   Information on the degree of reduction of the level of a predetermined number of subcarriers at one or both ends of the channel band relative to the level of subcarriers other than the predetermined number of subcarriers at one or both ends of the channel band, information regarding the second modulation scheme, And a plurality of combination patterns of information relating to the predetermined number are set in advance, and the information on the combination patterns is added to the signal modulated by the multicarrier modulation scheme and transmitted and / or received. 2. The wireless device according to 2.   A first modulation scheme is adopted for subcarriers other than a predetermined number of subcarriers at one or both ends of a channel band, and the first modulation scheme is applied to a predetermined number of subcarriers at one or both ends of the channel band. A signal modulation method characterized by modulating a signal by a multicarrier modulation method adopting a second modulation method having higher noise resistance. In the multicarrier modulation scheme,
The level of a predetermined number of subcarriers at one or both ends of the channel band,
The signal modulation method according to claim 5, wherein the signal modulation method is lower than a level of a subcarrier other than a predetermined number of subcarriers at one or both ends of the channel band.

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