WO2010067727A1

WO2010067727A1 - Radio apparatus

Info

Publication number: WO2010067727A1
Application number: PCT/JP2009/070142
Authority: WO
Inventors: 敦史須山; 利哉岩▲崎▼
Original assignee: 三洋電機株式会社
Priority date: 2008-12-08
Filing date: 2009-12-01
Publication date: 2010-06-17

Abstract

A radio apparatus (100), which is adapted to transmit or transmit/receive signals multicarrier-modulated by use of a first frequency band, comprises: a level determining means (43-45) that extracts signal components belonging to a second frequency band adjacent to the first frequency band and determines the levels of the extracted signal components; and a modulating unit (38) that, based on a result of the determination by the level determining means, sets the transmission power of all of the subcarriers included in the first frequency band to a default value when the signal levels of the signal components belonging to the second frequency band are higher than a predetermined value, while setting, to a value smaller than the default value, the transmission power of subcarriers that are included in the first frequency band but closer to the second frequency band when the above-mentioned signal levels are lower than the predetermined value.

Description

Wireless device

The present invention relates to a wireless device that transmits or transmits / receives a signal modulated by a multicarrier modulation method.

The ITS [Intelligent Transport Systems] inter-vehicle communication system, scheduled to start in 2012, exchanges various information between the host vehicle and other vehicles for the purpose of danger avoidance and driving support. . For example, by using an ITS inter-vehicle communication system to exchange position information between vehicles and alerting the driver of each vehicle to other vehicles, vehicles that meet at intersections with poor visibility It can contribute to the prevention of collision accidents.

In the ITS inter-vehicle communication system, the 720 MHz band is scheduled to be used as a wireless communication band between vehicles. As shown in FIG. 1, the use frequency band of the terrestrial digital television broadcasting system is adjacent to the low frequency side end of the use frequency band of the ITS inter-vehicle communication system with the guard band of 5 MHz interposed therebetween. The use frequency band of the telecommunication system is adjacent to the high frequency side end of the use frequency of the inter-vehicle communication system with the guard band of 5 MHz interposed therebetween.

Note that Patent Documents 1 to 3 can be cited as examples of the related art related to the above.

JP 2002-247004 A JP 2006-186630 A International Publication WO2006 / 070551 Pamphlet

Thus, the frequency bands of other systems are adjacent to both ends of the frequency band of the ITS inter-vehicle communication system. Under such a frequency arrangement, for example, when a vehicle equipped with an ITS inter-vehicle communication system is present in a hard-to-view area of a terrestrial digital television broadcasting system (distant from the transmission radio tower, mountainous area, etc.), Interference (interference) from the inter-vehicle communication system to the terrestrial digital television broadcasting system may become a problem. Further, for example, when a vehicle equipped with an ITS inter-vehicle communication system is present in the vicinity of a transmission tower of the terrestrial digital television broadcasting system, interference (covered) from the terrestrial digital television broadcasting system to the ITS inter-vehicle communication system is possible. Interference) may be a problem. Therefore, in the ITS inter-vehicle communication system, it is possible to reduce interference (interference) from the ITS inter-vehicle communication system to other systems adjacent to the use frequency band, and from the other systems adjacent to the use frequency band to the ITS inter-vehicle communication. Increasing resistance to interference (interference) with a communication system is an important issue.

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 level of the subcarrier at at least one end of the transmission channel band. There was a problem that the communication performance of the own system deteriorated.

In Patent Document 1, no particular mention was made as to when adjacent interference countermeasures are required. For example, even in a situation where interference from the own system to other systems with adjacent frequency bands (interference) does not become a problem, the level of the subcarrier at at least one end of the transmission channel band is uniform. As a result, the total throughput in the own system is unnecessarily reduced.

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.

Further, in Patent Document 3, the interference power is measured within the transmission channel band of the own system, and the modulation scheme and the like are set so that the required SNR [Signal Noise ratio] for each subcarrier is optimized according to the measurement result. There has been proposed a wireless communication system that adjusts transmission power to reduce interference as a whole system.

However, in the prior art of Patent Document 3, since the interference power is measured within the transmission channel band of the own system, whether the measurement result reflects interference due to leakage components from the adjacent band, There is a problem in that it is not always possible to distinguish whether or not it reflects interference caused by communication congestion.

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 the use frequency band Even in a wireless system in which the use frequency band of another system is adjacent to only one end, as in the case of the ITS inter-vehicle communication system, interference (giving interference) from the wireless system to another system in which the use frequency band is adjacent. It is an important issue in the radio system to reduce the noise and to improve the resistance against interference (interference) from the other system with the adjacent frequency band to the radio system.

In view of the above situation, the present invention takes appropriate interference countermeasures according to the situation, and effectively prevents interference (additional interference) to other systems with adjacent frequency bands while ensuring the communication quality of the own system. An object of the present invention is to provide a wireless device that can be reduced.

In order to achieve the above object, a radio apparatus according to the present invention is a radio apparatus that transmits or transmits / receives a signal subjected to multicarrier modulation using a first frequency band, and is a second frequency adjacent to the first frequency band. Level determination means for extracting a signal component belonging to a band and performing level determination thereof; based on a determination result of the level determination means, when the signal level of the signal component belonging to the second frequency band is greater than a predetermined value, the first When the transmission power of all subcarriers included in the frequency band is set to a default value and the signal level is lower than the predetermined value, the subcarrier included in the first frequency band is closer to the second frequency band. And a modulation unit that sets the transmission power of the subcarrier to a value smaller than the default value (first configuration).

In the wireless device having the first configuration, the modulation unit is configured to variably control the number of subcarriers whose transmission power is reduced according to the magnitude of the signal level (second configuration). Good.

More specifically, in the radio apparatus having the second configuration, the modulation unit increases the number of subcarriers whose transmission power is reduced as the signal level is smaller (third configuration). ).

Further, in the radio apparatus having any one of the first to third configurations, the modulation unit may have a configuration (fourth configuration) in which transmission power is reduced for subcarriers closer to the second frequency band.

Also, in the radio apparatus having any one of the first to fourth configurations, the modulation unit applies a second modulation scheme that is more resistant to noise than the default first modulation scheme for subcarriers whose transmission power is reduced. A configuration to be applied (fifth configuration) may be used.

In the radio apparatus having the fifth configuration, the modulation unit selects a modulation scheme having a smaller number of multi-values as a second modulation scheme applied to a subcarrier closer to the second frequency band. A configuration (sixth configuration) is preferable.

In the wireless device having any one of the first to sixth configurations, the second frequency band is sandwiched between the first frequency band used by the own system and the third frequency band used by the other system. A configuration (seventh configuration) that is part or all of the guard band may be employed.

In the wireless device having the seventh configuration, the guard band includes a low-frequency guard band adjacent to the low frequency side of the first frequency band and a high frequency frequency adjacent to the high frequency side of the first frequency band. A configuration (eighth configuration) that is at least one of the side guard bands may be used.

According to the present invention, since it is possible to implement an optimal interference countermeasure according to the situation, it is possible to reduce the interference with other systems adjacent to the used frequency band without unnecessarily reducing the total throughput in the own system. It can be effectively reduced.

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. 1 is a block diagram showing a first embodiment of an in-vehicle wireless communication device 100. FIG. 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 block diagrams which show 2nd Embodiment of the vehicle-mounted radio | wireless communication apparatus 100. FIG. These are block diagrams which show 3rd Embodiment of the vehicle-mounted radio | wireless communication apparatus 100. FIG. These are figures which show an example of the pass band of the low-pass filter 43. These are the figures which show the outline | summary of the modulation method which concerns on this invention which is an example of a countermeasure against interference. These are figures which show an example of the table referred at the time of countermeasures against interference. These are the figures which show the outline | summary of the modulation method which concerns on this invention which is an example of an interference countermeasure. These are figures which show an example of the table referred at the time of countermeasures against interference. These are block diagrams which show 4th Embodiment of the vehicle-mounted radio | wireless communication apparatus 100. FIG.

Embodiments of the present invention will be described in detail 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 as an example.

By the way, in the United States, the IEEE 802.11p standard is being studied as a standard for 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 seen from the physical layer is after the physical header composed 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 coarse frequency 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 on the transmission rate (modulation method) and packet length of physical data DATA is BPSK [Binary Phase Shift Keying] modulated. In IEEE802.11p, an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of multicarrier modulation schemes, is employed as a modulation scheme 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.

FIG. 4 is a block diagram showing the first embodiment of the in-vehicle wireless communication device 100. As shown in FIG.

As shown in FIG. 4, the in-vehicle wireless communication device 100 of this embodiment includes a serial / parallel converter 1 (hereinafter referred to as an S / P [Serial / Parallel] converter 1), a modulator 2, and an IFFT. [Inverse Fast Fourier Transform] section 3, guard interval addition section 4, addition processing section 5, digital / analog converter 6 (hereinafter referred to as D / A [Digital / Analog] converter 6), power A transmission unit including an amplifier 7 and a physical header processing unit 8 is provided.

Further, the in-vehicle wireless communication device 100 of the present embodiment includes a switch 9 for switching between transmission and reception, and a transmission / reception antenna 10.

The in-vehicle wireless communication device 100 according to the present embodiment includes a variable gain amplifier 11, an analog / digital converter 12 (hereinafter referred to as an A / D [Analog / Digital] converter 12), a separation processing unit 13, Guard interval removing unit 14, FFT unit [Fast Fourier Transform] unit 15, demodulator 16, parallel / serial converter 17 (hereinafter referred to as P / S [Parallel / Serial] converter 17), physical header And a processing unit 18.

The in-vehicle wireless communication device 100 performs the following operation during transmission. The S / P converter 1 parallelizes input transmission data (serial data) and outputs it 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 on the transmission data (parallel data) output from 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.

In addition, the in-vehicle wireless communication device 100 performs the following operation upon 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 first demodulated by fast Fourier transform processing by the FFT unit 15 after the guard interval is removed by the guard interval removing unit 14, and is demodulated by the demodulator 16 having the same number of subcarriers. Next demodulated. 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.

Subsequently, a multicarrier modulation method performed in the in-vehicle wireless communication device 100 will be described.

When taking measures against interference, the in-vehicle wireless communication device 100 performs, for example, the multicarrier modulation method shown in FIG. In the multicarrier modulation shown in FIG. 5B, primary modulation is performed with 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 the conventional multi-carrier modulation method as shown, 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 performs, for example, the multicarrier modulation method illustrated in FIG. 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. 6 (c), the level of subcarriers is reduced at both ends of the channel band, which is a major factor of interference, so that the conventional method as shown in FIG. 6 (a). Compared with the multi-carrier modulation method, it is possible to reduce interference with other systems that are adjacent to each other in the frequency band used (in addition to interference), and to provide a noise-resistant modulation scheme (in this case) that is more resistant to sub-carrier modulation where the level is reduced. Since QPSK) is employed, 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 above-described multicarrier modulation shown in FIG. 5B and multicarrier modulation shown in FIG. 6C, the number of subcarriers at both ends of the channel band (band in which the subcarriers are arranged) is low. Although the number is the same at the end and the high-frequency side end, 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 FIG. 7A or FIG. 7B may be used, and when taking countermeasures against interference, FIG. 8A or FIG. It is good also as multicarrier modulation like b).

FIG. 5 to FIG. 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 In the physical header, at least one piece of information on the second modulation scheme used in the above and information on the predetermined number is described in the physical header, and the level of subcarriers other than the predetermined number of subcarriers at both ends of the channel band Degree of reduction of the level of a predetermined number of subcarriers at both ends of the channel band, the second modulation scheme, and the To enable changing at least one of the constant number, it is necessary to describe 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 the information about the degree of reduction of the level of the predetermined number of subcarriers at both ends of the channel band with respect to the level of subcarriers other than the predetermined number of subcarriers at both ends of the channel band, the information about the second modulation scheme, and In addition to at least one piece of information on the predetermined number, information on a first modulation scheme used for modulation of subcarriers other than the predetermined number of subcarriers at both ends of the channel band, and the first modulation Of the information on the number of subcarriers modulated by the method, at least one piece of information may be separately described in a region different from the conventional signal field SIG.

Specific examples described separately in a region different from the conventional signal field SIG described above include the three examples shown in FIGS. 9 (a) to 9 (c).

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. The 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 a 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 is described. .

FIG. 9B shows a packet configuration when the reserve bit of the conventional signal field SIG compliant with IEEE802.11p is used, and when the reserve 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 among the information about the degree of reduction of the level of the predetermined number of subcarriers at both ends of the channel, the information about the second modulation scheme used for the modulation of the predetermined number of subcarriers at both ends of the channel band, and the information about the predetermined number One piece of information is described.

FIG. 9C shows the same configuration as a conventional packet (see FIG. 2) compliant with IEEE802.11p, but relates to the transmission rate (modulation method) of physical data DATA described in the signal field SIG. Ingenuity is added to how to handle information (hereinafter referred to as 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 in 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, 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 of information are assigned to combination patterns A to H. As the combination patterns, eight patterns 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 patterns A to H include 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 Information on the number of subcarriers modulated by one modulation scheme is also included. It can be said that each of the combination patterns A to H indicates 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 in the second embodiment shown in FIG. 12, and 10 of the number of modulators 2 are the same as the number of subcarriers. The modulator performs QPSK modulation, the other modulators perform 16QAM modulation, and among the same number of demodulators 16 as the number of subcarriers, 10 demodulators perform QPSK demodulation and the other demodulator perform 16QAM modulation. You should do it. 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 of the second embodiment 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 of the first embodiment shown in FIG.

The combination pattern selection unit 19 selects one of the eight combination patterns A to H shown in FIGS. 11A and 11B, and controls the modulator 2 according to the selection result to determine the level for each subcarrier. In addition, it is determined which modulator is assigned to which 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 of the second embodiment shown in FIG. 12, 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 selecting 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 selecting unit 19 selects the combination pattern according to the interference state. You may make it select.

In addition, as a technique for adaptively changing various parameters of the signal modulation method according to the present invention according to the situation, the signal strength (reception power) of other systems adjacent to the used frequency band is sequentially detected and detected. A configuration in which variable control of the various parameters is performed based on the result is conceivable. Hereinafter, the above configuration will be described in detail as a third embodiment according to the present invention.

FIG. 13 is a block diagram showing a third embodiment of the in-vehicle wireless communication device 100. As shown in FIG.

As shown in FIG. 13, the in-vehicle wireless communication device 100 of this embodiment includes a transmission / reception antenna 31, a switch 32, a low noise amplifier 33 (hereinafter referred to as LNA [Low Noise Amplifier] 33), and a desired wave pass filter 34. An analog / digital converter 35 (hereinafter referred to as an A / D converter 35), a synchronization processing unit 36, a demodulation unit 37, a modulation unit 38, a transmission processing unit 39, and a digital / analog converter 40. (Hereinafter referred to as a D / A converter 40), a desired wave pass filter 41, and a high-power amplifier 42, and further, as a component specific to the present embodiment, a low-pass filter 43, , An analog / digital converter 44 (hereinafter referred to as an A / D converter 44) and a determination unit 45.

Among the components listed above, the transmission / reception antenna 31 in FIG. 13 corresponds to the transmission / reception antenna 10 in FIG. 4 or FIG. 12, and the switch 32 in FIG. 13 corresponds to the switch 9 in FIG. 13 corresponds to the variable gain amplifier 11 of FIG. 4 or FIG. 12, and the A / D converter 35 of FIG. 13 corresponds to the A / D converter 12 of FIG. Further, the D / A converter 40 in FIG. 13 corresponds to the D / A converter 6 in FIG. 4 or FIG. 12, and the high-power amplifier 42 in FIG. 13 corresponds to the power amplifier 7 in FIG. .

The synchronization processing unit 36 and the demodulation unit 37 in FIG. 13 do not depict components directly associated with FIG. 4 or FIG. 12, but the separation processing unit 13 and the guard interval removal unit in FIG. 4 or FIG. 14, the FFT unit 15, the demodulator 16, the P / S converter 17, the physical header processing unit 18, and the combination pattern determination unit 20 are understood to correspond to this. Also, the modulation unit 38 and the transmission processing unit 39 in FIG. 13 do not depict components directly associated with FIG. 4 or FIG. 12, but the S / P converter 1 and the modulator in FIG. 2, IFFT unit 3, guard interval addition unit 4, addition processing unit 5, physical header processing unit 8, and combination pattern selection unit 19 are understood to correspond to this.

During the reception operation of the in-vehicle wireless communication device 100, the switch 32 conducts between the transmission / reception antenna 31 and the LNA 33. The LNA 33 amplifies the power of a reception signal input from the transmission / reception antenna 31 via the switch 32 with a predetermined gain. For example, in the frequency arrangement shown in FIG. 1, the desired wave pass filter 34 converts a signal input from the LNA 33 to receive a desired signal (a signal exchanged in the ITS inter-vehicle communication system in the example of FIG. 1). Filtering processing is performed to pass only frequency components belonging to a desired channel band (715 MHz to 725 MHz in the example of FIG. 1). The A / D converter 35 converts the analog signal input from the desired wave pass filter 34 into a digital signal. The synchronization processing unit 36 performs synchronization processing of the signal input from the A / D converter 35. The demodulation unit 37 demodulates desired received data by performing FFT processing and demapping processing on the signal input from the synchronization processing unit 36.

On the other hand, during the transmission operation of the in-vehicle wireless communication device 100, the switch 32 conducts between the transmission / reception antenna 31 and the high-power amplifier 42. Based on an instruction from the determination unit 45, the modulation unit 38 performs an appropriate modulation process on the transmission data according to the situation. The transmission processing unit 39 performs an IFFT process on the digital signal input from the modulation unit 38 to generate an OFDM signal. The D / A converter 40 converts the digital signal (OFDM signal) input from the transmission processing unit 39 into an analog signal. For example, in the frequency arrangement shown in FIG. 1, the desired wave pass filter 41 sends a desired signal (a signal exchanged in the ITS inter-vehicle communication system in the example of FIG. 1) from the D / A converter 40. The input signal is subjected to filtering processing to pass only frequency components belonging to a desired channel band (715 MHz to 725 MHz in the example of FIG. 1). The high-power amplifier 42 amplifies the signal input from the desired wave pass filter 41 with a predetermined gain. The transmission signal amplified by the high-power amplifier 42 is transmitted to the transmission / reception antenna 31 via the switch 32 and transmitted from the transmission / reception antenna 31 to the outside of the in-vehicle wireless communication device 100.

Next, a detailed description will be given of a method for controlling the necessity or degree (intensity) of measures against adjacent interference during the transmission operation of the in-vehicle wireless communication device 100.

As shown in FIG. 14, the low-pass filter 43 is a means for performing a filtering process on the signal input from the LNA 33, and is a first frequency band used by the ITS inter-vehicle communication system (in the example of FIG. 14, A second frequency band (in the example of FIG. 14, including a 5 MHz wide guard band) on the lower side of the frequency band (715 MHz to 725 MHz) having a total frequency of 10 MHz with a center frequency of 720 MHz, Only signal components belonging to a frequency band (705 MHz to 715 MHz) having a total width of 10 MHz are selectively passed.

In FIG. 14, the pass band of the low-pass filter 43 is set so as to include a guard band adjacent to the low-frequency side of the ITS inter-vehicle communication system and a part of the use frequency band of the digital television broadcasting system. Although the configuration of the present invention is illustrated, the configuration of the present invention is not limited to this, and the pass band of the low-pass filter 43 is set so as to include all the frequency bands used in the digital television broadcasting system. Also good. In addition, only the guard band may be set as the pass band of the low-pass filter 43, or a part or all of the frequency band used in the digital television broadcasting system except for the guard band may be set in the low-pass filter 43. A pass band may be set. What is important is that the channel band of the ITS inter-vehicle communication system is not included in the pass band of the low pass filter 43 (that is, the pass band of the desired wave pass filter 3 and the pass band of the low pass filter 34). And are set exclusively).

The A / D converter 44 converts the analog signal input from the low-pass filter 43 into a digital signal.

The determination unit 45 performs level determination (received power measurement) of the digital signal input from the A / D converter 44 and notifies the modulation unit 38 of the determination result. As the determination unit 45, an RSSI [Received Signal Strength Indicator] circuit or the like generally used as a received signal strength measurement unit can be suitably applied. The RSSI circuit may be incorporated in the determination unit 45 or may be inserted between the low-pass filter 43 and the A / D converter 44.

The modulation unit 38 appropriately sets various parameters of the signal modulation method based on the notification from the determination unit 45.

For example, when the interference from the digital television broadcasting system to the ITS inter-vehicle communication system becomes a problem, the modulation unit 38, if the signal level (reception power P) input to the determination unit 45 is larger than a predetermined value, It is determined that countermeasures against interference are necessary, and among the subcarriers included in the channel band of the ITS inter-vehicle communication system, the modulation scheme for the N subcarriers from the low frequency side is set to the default first modulation scheme ( For example, it may be configured to switch from 16 QAM) to the second modulation method (for example, QPSK) having a lower multi-value number and stronger noise resistance (see FIG. 15A).

The modulation unit 38 variably controls the number N of low-frequency subcarriers to which the second modulation scheme (QPSK) is applied according to the signal level (received power P) input to the determination unit 45. do it. More specifically, the modulation unit 38 increases the second modulation scheme (intensity) as the signal level (reception power P) input to the determination unit 45 increases as the level of interference countermeasures (intensity) increases. The number N of low frequency side subcarriers to which QPSK is applied may be increased.

At this time, the modulation unit 38 may determine the number N of low-frequency subcarriers to which the second modulation scheme (QPSK) is applied based on the table illustrated in FIG. The operation of determining the number N by the modulation unit 38 will be specifically described with reference to the example of FIG.

When the modulation unit 38 receives a notification from the determination unit 45 that P ≧ −30 dBm (high level), the second modulation method (QPSK) is set so that the degree (strength) of countermeasures against interference is a strong level. The number N of low frequency side subcarriers to be applied is set to “10”. As a result, among the subcarriers included in the channel band, 10 subcarriers from the low frequency side are modulated by the second modulation scheme (QPSK), and the remaining subcarriers are modulated by the first modulation scheme (16QAM). Is done.

Further, when receiving a notification from the determination unit 45 that −70 dBm <P <−30 dBm (medium level), the modulation unit 38 sets the second countermeasure level (strength) to the middle level. The number N of low-frequency subcarriers to which the modulation scheme (QPSK) is applied is set to “5”. As a result, among the subcarriers included in the channel band, five subcarriers from the low frequency side are modulated by the second modulation scheme (QPSK), and the remaining subcarriers are modulated by the first modulation scheme (16QAM). Is done.

Further, when the modulation unit 38 receives a notification that P ≦ −70 dBm (low level) from the determination unit 45, the modulation unit 38 sets the second level of interference countermeasures (strength) to a weak level (off). The number N of low-frequency subcarriers to which the modulation scheme (QPSK) is applied is set to “0”. As a result, all subcarriers included in the channel band are modulated by the first modulation scheme (16QAM) (similar to the conventional example of FIG. 5A or FIG. 6A).

In this way, the signal strength (reception power) of the digital television broadcasting system in which the used frequency band is adjacent is sequentially detected, and based on the detection result, various parameters of the signal modulation method (in the above, the second modulation method ( If the configuration is such that the number N) of low-frequency subcarriers to which QPSK) is applied can be variably controlled, optimum countermeasures against interference can be implemented according to the situation, thus eliminating the need for total throughput in the own system. Without lowering, it is possible to effectively prevent performance degradation due to interference from the digital television broadcasting system.

Further, in the wireless communication device 100 of the present embodiment, the interference power from the digital television broadcasting system is higher than the conventional configuration (see Patent Document 3) that measures the interference power within the channel band of the ITS inter-vehicle communication system. Therefore, the necessity or degree (intensity) of countermeasures against interference can be appropriately controlled according to the situation.

In FIG. 15A, in order to take measures against interference from the digital television broadcasting system adjacent to the low frequency side of the ITS inter-vehicle communication system, the low frequency side subcarriers (N) of the ITS inter-vehicle communication system. However, the configuration of the present invention is not limited to this, and the configuration adjacent to the high frequency side of the ITS inter-vehicle communication system is described. When taking measures against interference from a communication system (for example, a mobile phone communication service), as shown in FIG. 15B, the second modulation method is applied to the high frequency side subcarriers (M) of the ITS inter-vehicle communication system. A configuration in which (QPSK) is applied may be employed.

At this time, as a component of the wireless communication device 100, it is necessary to replace the low-pass filter 43 with a high-pass filter (not shown). The high-pass filter is a means for performing a filtering process on the signal input from the LNA 33, and is adjacent to the first frequency band used by the ITS inter-vehicle communication system, for example, on the high-frequency side. It is only necessary to selectively pass only signal components belonging to the second frequency band having a total width of 10 MHz in a form including a guard band having a width of 5 MHz. In addition, it is necessary to replace the low-frequency subcarrier (N) variable control table illustrated in FIG. 16A with the high-frequency subcarrier (M) variable control table. In this regard, it is sufficient to replace “the number N of carriers modulated by QPSK” with “the number M of carriers modulated by QPSK” in the content illustrated in FIG.

Further, when both countermeasures against interference from the digital television broadcasting system adjacent to the low frequency side of the ITS inter-vehicle communication system and interference countermeasures from the telecommunication system adjacent to the high frequency side are performed, FIG. As shown in c), the second modulation scheme (QPSK) may be applied to both the low frequency side subcarriers (N) and the high frequency side subcarriers (M) of the ITS inter-vehicle communication system. .

At this time, as a component of the wireless communication device 100, it is necessary to provide a high-pass filter (not shown) in parallel with the low-pass filter 43. In addition to the variable control table for the low frequency side subcarriers (N) illustrated in FIG. 16A, it is also necessary to prepare a variable control table for the high frequency side subcarriers (M). .

Further, in FIG. 15A, in order to take measures against interference from the digital television broadcasting system adjacent to the low frequency side of the ITS inter-vehicle communication system, the low frequency side subcarriers (N) of the ITS inter-vehicle communication system. However, the configuration of the present invention is not limited to this. For example, as shown in FIG. 15 (d), ITS inter-vehicle communication is performed. Of the low-frequency side subcarriers ((K + L)) of the system, QPSK is applied to the higher L-side subcarriers, while the lower number K of the lower-frequency side subcarriers has more multivalued numbers than QPSK. There may be a configuration in which a modulation method with little noise resistance (for example, BPSK [Binary Phase Shift Keying]) is applied. In this way, by selecting a modulation scheme having a smaller multi-value number as a second modulation scheme applied to a subcarrier closer to the use frequency band of the adjacent digital television broadcasting system, FIG. ), It is possible to further increase the tolerance against interference.

At this time, the contents of the table referred to by the modulation unit 38 are, for example, as shown in FIG. Note that the object to which the modulation method shown in FIG. 15 (d) is applied is not limited to only the low frequency side subcarriers, and only the high frequency side subcarriers may be applied. Both the subcarrier and the high frequency side subcarrier may be applied.

On the other hand, when the interference from the ITS inter-vehicle communication system to the digital television broadcasting system becomes a problem, the modulation unit 38, if the signal level (reception power P) input to the determination unit 45 is smaller than a predetermined value, A configuration that determines that countermeasures against interference are necessary and reduces the signal level (transmission power) of N subcarriers from the low frequency side among the subcarriers included in the channel band of the ITS inter-vehicle communication system; (See FIG. 17 (a)).

Further, the modulation unit 38 may be configured to variably control the number N of low-frequency subcarriers whose signal level is reduced according to the signal level (reception power P) input to the determination unit 45. More specifically, the modulation unit 38 reduces the signal level so that the degree (intensity) of countermeasures against interference increases as the signal level (reception power P) input to the determination unit 45 decreases. It is sufficient to increase the number N of low frequency side subcarriers.

In addition, as a countermeasure against interference, for the low-frequency side subcarrier with a reduced signal level, the modulation scheme is changed from the default first modulation scheme (for example, 16QAM) to the second modulation having a lower multi-level number and stronger noise resistance. The system may be switched to a system (for example, QPSK) (see FIG. 17B). By adopting such a configuration, it is possible to maintain better communication quality as compared with the conventional multicarrier modulation method (method proposed in Patent Document 1) as shown in FIG.

At this time, the modulation unit 38 sets the signal level (transmission power) to ½ of the default value based on the table illustrated in FIG. 18A, and the second modulation method (QPSK) is set. The number N of low frequency side subcarriers to be applied may be determined. The operation of determining the number N by the modulation unit 38 will be specifically described with reference to the example of FIG.

When receiving a notification that P ≧ −30 dBm (high level) from the determination unit 45, the modulation unit 38 sets the signal level (transmission) in order to set the degree (strength) of interference countermeasures to a weak level (off). Power) is set to ½ of the default value, and the number N of low-frequency subcarriers to which the second modulation scheme (QPSK) is applied is set to “0”. As a result, all the subcarriers included in the channel band have the signal level (transmission power) set to the default value and are modulated by the first modulation scheme (16QAM) (FIG. 5A or FIG. The same as the conventional example of a)).

Further, when the modulation unit 38 receives notification from the determination unit 45 that −70 dBm <P <−30 dBm (medium level), the signal level (intensity) is set to the signal level (intensity). Transmission power) is set to ½ of the default value, and the number N of low-frequency subcarriers to which the second modulation scheme (QPSK) is applied is set to “5”. As a result, among the subcarriers included in the channel band, the signal level (transmission power) of subcarriers for five from the low frequency side is set to 1/2 of the default value, and the second modulation scheme (QPSK) ) And the remaining subcarriers are modulated with the first modulation scheme (16QAM) with the signal level (transmission power) set to a default value.

Further, when the modulation unit 38 receives a notification that P ≦ −70 dBm (low level) from the determination unit 45, the modulation unit 38 sets the signal level (transmission power) so that the degree of interference countermeasure (strength) is set to a high level. ) Is set to ½ of the default value, and the number N of low-frequency subcarriers to which the second modulation scheme (QPSK) is applied is set to “10”. As a result, among the subcarriers included in the channel band, the signal level (transmission power) of 10 subcarriers from the low frequency side is set to 1/2 of the default value, and the second modulation scheme (QPSK) ), And the remaining subcarriers are modulated with the first modulation scheme (16QAM) with the signal level (transmission power) set to a default value.

In this way, the signal strength (reception power) of the digital television broadcasting system in which the used frequency band is adjacent is sequentially detected, and based on the detection result, various parameters of the signal modulation method (in the above, the signal level (transmission level) Power) is set to ½ of the default value, and the number of low-frequency subcarriers N) to which the second modulation scheme (QPSK) is applied is variably controlled. Since measures can be taken, it is possible to effectively prevent interference with the digital television broadcasting system without unnecessarily reducing the total throughput in the own system.

In FIGS. 17A and 17B, the low frequency side subcarrier of the ITS inter-vehicle communication system is used to take measures against interference with the digital television broadcasting system adjacent to the low frequency side of the ITS inter-vehicle communication system. (N) has been described by exemplifying a configuration for reducing the signal level (transmission power) and applying the second modulation scheme (QPSK), but the configuration of the present invention is not limited to this. However, when taking measures against interference with an telecommunications system (for example, a mobile phone communication service) adjacent to the high frequency side of the ITS inter-vehicle communication system, as shown in FIG. The high frequency side subcarriers (M) may be configured to reduce the signal level (transmission power) and apply the second modulation scheme (QPSK).

At this time, as a component of the wireless communication device 100, it is necessary to replace the low-pass filter 43 with a high-pass filter (not shown). The high-pass filter is a means for performing a filtering process on the signal input from the LNA 33, and is adjacent to the first frequency band used by the ITS inter-vehicle communication system, for example, on the high-frequency side. It is only necessary to selectively pass only signal components belonging to the second frequency band having a total width of 10 MHz in a form including a guard band having a width of 5 MHz. In addition, it is necessary to replace the low frequency side subcarrier (N) variable control table illustrated in FIG. 18A with the high frequency side subcarrier (M) variable control table. In this regard, in the content illustrated in FIG. 18A, the place “the number of carriers N to reduce transmission power to ½ and QPSK modulation” is changed to “transmission power to ½ and QPSK. It is sufficient to read as “the number of carriers M to be modulated by”.

In the case where both countermeasures for interference with the digital television broadcasting system adjacent to the low frequency side of the ITS inter-vehicle communication system and countermeasures for interference with the telecommunication system adjacent to the high frequency side are performed, FIG. As shown in d), the signal level (transmission power) is reduced and the second modulation scheme (N) for both the low frequency side subcarriers (N) and the high frequency side subcarriers (M) of the ITS inter-vehicle communication system. A configuration in which QPSK) is applied may be employed.

At this time, as a component of the wireless communication device 100, it is necessary to provide a high-pass filter (not shown) in parallel with the low-pass filter 43. In addition to the variable control table for the low frequency side subcarriers (N) illustrated in FIG. 18A, it is also necessary to prepare a variable control table for the high frequency side subcarriers (M). .

17 (a) and 17 (b), the low frequency side subcarrier of the ITS inter-vehicle communication system is designed to take measures against interference with the digital television broadcasting system adjacent to the low frequency side of the ITS inter-vehicle communication system. (N) has been described by exemplifying a configuration that uniformly reduces the signal level (transmission power), but the configuration of the present invention is not limited to this, and for example, FIG. As shown, among the low frequency side subcarriers ((K + L)) of the ITS inter-vehicle communication system, the signal level (transmission power) is reduced to ½ of the default value for L of the higher frequency side subcarriers. For the lower K, the signal level (transmission power) may be reduced to 1/4 of the default value in order to further reduce the signal level (transmission power). At this time, the contents of the table referred to by the modulation unit 38 are, for example, as shown in FIG. In this way, by reducing the signal level (transmission power) for subcarriers closer to the frequency band used in the adjacent digital television broadcasting system, the interference is further increased compared to the configurations of FIGS. 17 (a) and 17 (b). Can be reduced.

In FIG. 17E, subcarriers (K lines) whose signal level is reduced to ¼ of the default value and subcarriers (L lines) whose signal level is reduced to ½ of the default value. In any case, the configuration in which the second modulation scheme (QPSK) is applied has been described as an example. However, the configuration of the present invention is not limited to this, and for example, as illustrated in FIG. Of the low frequency side subcarriers ((K + L)) of the ITS inter-vehicle communication system, QPSK is applied to L of the higher frequency side, while K of the lower frequency side is more than QPSK. Furthermore, a configuration in which a modulation scheme (eg, BPSK) having a small number of multi-values and strong noise resistance may be applied. At this time, the work of partially changing the contents of the table illustrated in FIG. 18B is necessary. This is because, among the contents illustrated in FIG. The number “carrier number K that is reduced to 4 and modulated by QPSK” may be read as “number of carriers K that is modulated by BPSK by reducing transmission power to ¼” (see FIG. 18C). As described above, by applying a modulation scheme (BPSK) having a higher noise resistance to subcarriers whose signal level (transmission power) is reduced to ¼ of the default value, good communication quality is maintained. Can do.

Note that the object to which the modulation method shown in FIG. 17 (e) or FIG. 17 (f) is applied is not limited to only the low frequency side subcarriers, and only the high frequency side subcarriers may be applied. Alternatively, both the low frequency side subcarrier and the high frequency side subcarrier may be applied.

Further, as already described, it is possible to set only the guard band as the pass band of the low-pass filter 43 used in the in-vehicle wireless communication device 100 of the third embodiment. Needless to say, even when the filter 43 is replaced with a high-pass filter (not shown), only the guard band can be set as the pass band.

Therefore, in order to clarify that the above-described modification is possible, the fourth embodiment will be described in detail as an example. FIG. 19 is a block diagram illustrating a fourth embodiment of the in-vehicle wireless communication device 100.

As shown in FIG. 19, the in-vehicle wireless communication device 100 of the fourth embodiment has substantially the same configuration as that of the third embodiment described above, and instead of the low-pass filter 43, the guard band pass filter 46 is used. It has the feature in having. Therefore, the same components as those of the third embodiment are denoted by the same reference numerals as those in FIG. 13, and redundant description is omitted. Hereinafter, the guard band pass filter 46 which is a characteristic part of the fourth embodiment will be emphasized. Give an explanation.

The guard band pass filter 46 is provided on the low frequency side of the first frequency band used by the ITS inter-vehicle communication system (in FIG. 1 to FIG. 14, the frequency band (715 MHz to 725 MHz) having a total frequency of 10 MHz with 720 MHz as the central frequency). At least one of the adjacent low band guard band (710 MHz to 715 MHz in FIGS. 1 to 14) and the high band guard band (725 MHz to 730 MHz in FIG. 1) adjacent to the high band side of the ITS inter-vehicle communication system. A part or all of each frequency band (5 MHz width) is used as a pass band, and only signal components belonging to the pass band are selectively passed.

In this way, for at least one of the high band side guard band and the low band side guard band, the intensity (reception power) of signal components belonging to part or all of each frequency band is sequentially detected, and based on the detection result Various parameters of the signal modulation method (for example, if countermeasures against interference are to be taken, for example, the number of low frequency side subcarriers to which the second modulation scheme (QPSK) is applied and if countermeasures against interference are to be taken. For example, if the configuration is such that the signal level (transmission power) is variably controlled (the number of low-frequency subcarriers set to ½ of the default value), as in the third embodiment, depending on the situation Since it is possible to implement optimal interference countermeasures or interference countermeasures, it is possible to prevent interference or other interference from other systems without unnecessarily reducing the total throughput in the local system. It becomes possible to prevent the interference with the stem effectively.

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

In the first and second embodiments of the present invention, not only a wireless device (transmission / reception device) that performs transmission and reception, but also a wireless device (transmission device) that performs transmission only, and a wireless device (reception device) that performs reception only. It can also be applied to. The third and fourth embodiments of 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 transmission only. The first to fourth embodiments of the present invention can be applied not only to OFDM modulation but also to other multicarrier modulation.

For example, by providing each vehicle with the wireless device according to the present invention, it is possible to suppress mutual interference between the digital television broadcasting system and the ITS inter-vehicle communication system, and effectively prevent communication performance deterioration of both systems. Therefore, the digital television broadcasting system and the ITS inter-vehicle communication system can coexist.

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)
18 Physical Header Processing Unit 19 Combination Pattern Selection Unit 20 Combination Pattern Determination Unit 31 Transmit / Receive Antenna 32 Switch 33 Low Noise Amplifier (LNA)
34 Desired wave pass filter 35 Analog / digital converter (A / D converter)
36 synchronization processing unit 37 demodulation unit 38 modulation unit 39 transmission processing unit 40 digital / analog converter (D / A converter)
41 Desired wave pass filter 42 High-power amplifier 43 Low-pass filter 44 Analog / digital converter (A / D converter)
45 Judgment Unit 46 Guard Band Pass Filter 100 In-vehicle Wireless Communication Device that Performs ITS Vehicle-to-Vehicle Communication 200 Vehicle

Claims

A wireless device that transmits or transmits / receives a multi-carrier modulated signal using a first frequency band,
Level determination means for extracting a signal component belonging to a second frequency band adjacent to the first frequency band and performing level determination thereof;
Based on the determination result of the level determination means, when the signal level of the signal component belonging to the second frequency band is greater than a predetermined value, the transmission power of all subcarriers included in the first frequency band is set to a default value, When the signal level is smaller than the predetermined value, a modulation unit that sets transmission power of a subcarrier closer to the second frequency band among subcarriers included in the first frequency band to a value smaller than the default value When;
A wireless device comprising:
The radio apparatus according to claim 1, wherein the modulation unit variably controls the number of subcarriers whose transmission power is reduced according to the magnitude of the signal level.
The radio apparatus according to claim 2, wherein the modulation unit increases the number of subcarriers in which transmission power is reduced as the signal level decreases.
The radio apparatus according to any one of claims 1 to 3, wherein the modulation unit reduces transmission power of a subcarrier closer to the second frequency band.
5. The modulation unit according to claim 1, wherein the second modulation scheme having higher noise resistance than the default first modulation scheme is applied to subcarriers whose transmission power is reduced. The wireless device described.
The radio apparatus according to claim 5, wherein the modulation unit selects a modulation scheme having a smaller multi-level number as a second modulation scheme applied to a subcarrier closer to the second frequency band. .
The second frequency band is a part or all of a guard band sandwiched between a first frequency band used by the own system and a third frequency band used by another system. The wireless device according to claim 6.
The guard band is at least one of a low band guard band adjacent to the low frequency side of the first frequency band and a high band guard band adjacent to the high frequency side of the first frequency band. The wireless device according to claim 7.