JP2011015078A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for recognizing the influence of interference regardless of whether timing synchronization is established or not.SOLUTION: A radio section 22 inputs the signal of a time domain. An FFT section 42 converts the input signal of the time domain to the signal of a frequency domain. A detection section 48 detects whether reception power of the signal of the frequency domain has an upward tendency from one frequency side of the signal of the frequency domain to the other frequency side. An estimation section 50 estimates presence of interference power in the other frequency side when detecting the upward tendency.

Description

  The present invention relates to communication technology, and more particularly to a receiving apparatus that receives a desired signal in the presence of an interference signal.

  An ITS (Intelligent Transport Systems) inter-vehicle communication system notifies other vehicles of the position, speed information, etc. of the vehicle that is out of sight as one of applications. By this notification, it is expected to prevent an encounter vehicle collision accident at an intersection with poor visibility. The ITS inter-vehicle communication system is scheduled to use the 720 MHz band. The use frequency band of the terrestrial digital television broadcasting system is adjacent to the lower end of the use frequency band of the ITS inter-vehicle communication system with the guard band of 5 MHz interposed therebetween.

  In addition, a frequency band used for telecommunications is adjacent to a high frequency side end portion of a use frequency of the ITS inter-vehicle communication system across a guard band of 5 MHz. As described above, the frequency bands of other systems are adjacent to each other with the guard band between both ends of the frequency band of the ITS vehicle-to-vehicle communication system. There is a possibility of receiving. Under the influence of interference, the reception performance of the ITS inter-vehicle communication system is likely to deteriorate (for example, see Patent Document 1).

JP 2002-271240 A

  In order to reduce the influence of interference in the ITS inter-vehicle communication system, it is effective to use an adaptive array antenna. Adaptive array antenna technology controls beam directivity by controlling the weight for each of a plurality of antennas. As a result, the interference signal is effectively suppressed. When the ITS inter-vehicle communication system supports the OFDM modulation system, generally, an adaptive array antenna technology is applied to a signal converted into a frequency domain by FFT (Fast Fourier Transform). At that time, the FFT window should be set to suit the received signal. If the FFT window is not suitable for the received signal, the weight error becomes large and the beam directivity becomes inaccurate. There is also a radio wave environment in which an FFT window is difficult to set. In this case, if waiting until the FFT window is appropriately set, the period until the weight is derived becomes longer. On the other hand, even if the FFT window is not set appropriately, it is required to grasp the influence of interference. When the influence of interference is grasped, it is possible to take some measures against the interference.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for grasping the influence of interference regardless of whether timing synchronization is established.

  In order to solve the above problems, a receiving apparatus according to an aspect of the present invention includes an input unit that inputs a time domain signal, a conversion unit that converts the time domain signal input in the input unit into a frequency domain signal, A detection unit that detects whether the reception power of the frequency domain signal converted by the conversion unit has an upward trend from one frequency side of the frequency domain signal to the other frequency side, and the detection unit has an upward trend And an estimation unit that estimates the presence of interference power on the other frequency side when detected.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, the influence of interference can be grasped regardless of whether timing synchronization is established.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. It is a figure which shows the channel arrangement | positioning of the communication system of FIG. It is a figure which shows the structure of the terminal device mounted in the vehicle of FIG. 4A to 4D are diagrams illustrating an outline of processing of the detection unit in FIG. It is a flowchart which shows the procedure of the reception process by the terminal device of FIG. It is a flowchart which shows the procedure of the detection process by the terminal device of FIG. It is a flowchart which shows the procedure of the detection process by the terminal device which concerns on the modification of this invention.

  Before describing the present invention in detail, an outline will be described. An embodiment of the present invention relates to a communication system that performs data communication between terminal devices mounted on a vehicle. The terminal device transmits a packet signal storing information such as the speed and position of the vehicle (hereinafter referred to as “data”) (hereinafter, the packet signal storing the data may be referred to as “data”). On the other hand, the terminal device receives a packet signal transmitted from another terminal device and recognizes the approach of another vehicle on which the other terminal device is mounted based on the data. Here, it is assumed that broadcast transmission is performed as transmission in order to efficiently receive data to a plurality of terminal devices. Further, a band for a terrestrial digital television broadcasting system is arranged adjacent to a low frequency side of a band for a communication system, and a band for a mobile phone system is arranged on a high frequency side of the band for a communication system. Bands are arranged adjacent to each other.

  Communication quality of a communication system is affected by interference waves from a terrestrial digital television broadcasting system and a mobile phone system. Therefore, it is effective for the driver to grasp the influence of interference in advance. For example, when the influence of the interference by the mobile phone system is large, the driver can perform a treatment such that the mobile phone device in the vehicle is separated from the terminal device. It is preferable that the period required for grasping the influence of such interference is shorter. On the other hand, when the communication system supports the OFDM modulation scheme, demodulation is started after the FFT window is appropriately set. As described above, depending on the radio wave environment, it may be difficult to set the FFT window appropriately. Even in such a case, the processing for grasping the influence of interference is required to be executed. In order to cope with this, the communication system according to the present embodiment executes the following processing.

  The terminal device according to the embodiment generates a frequency domain signal by performing FFT even before the FFT window is appropriately set. Further, the terminal device derives a power distribution in the frequency domain by measuring the reception power of each subcarrier signal included in the frequency domain signal. Further, the terminal device derives the slope of the received power in the frequency direction from the power distribution. If the absolute value of the slope is larger than the threshold value, the terminal apparatus estimates that an interference wave exists on the frequency side with the larger received power. Further, the terminal device executes the same processing even after the FFT window is appropriately set. That is, the terminal device can estimate the presence of an interference wave regardless of whether or not the FFT window is appropriately set.

  FIG. 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. This corresponds to a case where one intersection is viewed from above. The communication system 100 includes a first vehicle 12a, a second vehicle 12b, a third vehicle 12c, a fourth vehicle 12d, a fifth vehicle 12e, a sixth vehicle 12f, a seventh vehicle 12g, and an eighth vehicle 12h, which are collectively referred to as a vehicle 12. including. Each vehicle 12 is equipped with a terminal device (not shown).

  As shown in the drawing, the road that goes in the horizontal direction of the drawing, that is, the left and right direction, intersects the vertical direction of the drawing, that is, the road that goes in the up and down direction, at the central portion. Here, the upper side of the drawing corresponds to the direction “north”, the left side corresponds to the direction “west”, the lower side corresponds to the direction “south”, and the right side corresponds to the direction “east”. The intersection of the two roads is an “intersection”. The first vehicle 12a and the second vehicle 12b are traveling from left to right, and the third vehicle 12c and the fourth vehicle 12d are traveling from right to left. Further, the fifth vehicle 12e and the sixth vehicle 12f are traveling from the top to the bottom, and the seventh vehicle 12g and the eighth vehicle 12h are traveling from the bottom to the top.

  The terminal device mounted on each vehicle 12 acquires data and broadcasts a packet signal in which the data is stored. Here, each terminal device corresponds to CSMA / CA (Carrier Sense Multiple Access Collision Aviation) as in a known wireless LAN (Local Area Network), and is determined to be capable of performing carrier sense and transmitting. If this happens, broadcast data. As described above, the band used by the terrestrial digital television broadcasting system (not shown) and the band used by the mobile phone system are arranged around the band used by the communication system 100. Since the influence of interference from other systems affects the communication quality, each terminal apparatus estimates the influence of interference from other systems. The estimation of the influence of interference will be described later.

  FIG. 2 shows a channel arrangement of the communication system 100. The horizontal axis represents frequency and the vertical axis represents power. As illustrated, the communication system 100 is disposed in a communication system band 114. Further, the first guard band 112 is arranged adjacent to the low frequency side of the communication system band 114, and the terrestrial digital broadcast band 110 is arranged adjacent to the low frequency side of the first guard band 112. . The terrestrial digital broadcast band 110 is used by the terrestrial digital broadcast 102. A part of the spectrum of the terrestrial digital broadcast 102 extends to the communication system band 114 as shown in the figure. Usually, this part of power is set so as not to affect the communication system 100, but depending on the radio wave environment of the communication system 100 and the terrestrial digital broadcast 102, part of the power of the terrestrial digital broadcast 102 is used. May affect the communication system 100.

  Further, the second guard band 116 is disposed adjacent to the high frequency side of the communication system band 114, and the mobile phone system band 118 is disposed adjacent to the high frequency side of the second guard band 116. The cellular phone system band 118 is used by the cellular phone system 104. A part of the spectrum of the mobile phone system 104 covers the communication system band 114 as shown in the figure. The influence of part of the power of the mobile phone system 104 on the communication system 100 is the same as in the case of the terrestrial digital broadcast 102.

  FIG. 3 shows a configuration of the terminal device 14 mounted on the vehicle 12. The terminal device 14 includes an antenna 20, a radio unit 22, a transmission unit 24, a reception unit 26, and a control unit 28. The transmission unit 24 includes an acquisition unit 30, a generation unit 32, a modulation unit 34, and an IFFT unit 36. The receiving unit 26 includes a synchronization unit 38, a setting unit 40, an FFT unit 42, a demodulation unit 44, a notification unit 46, a detection unit 48, and an estimation unit 50. Further, the detection unit 48 includes a measurement unit 52, a moving average unit 54, a derivation unit 56, and a comparison unit 58.

  The acquisition unit 30 includes a GPS receiver, a gyroscope, a vehicle speed sensor, and the like, and acquires the location of the vehicle 12 on which the terminal device 14 is mounted, the traveling direction of the vehicle, the moving speed, and the like. The existence position is indicated by latitude and longitude. Since a well-known technique should just be used for acquisition of an existing position etc. by the acquisition part 30, description is abbreviate | omitted here. The acquisition unit 30 outputs information related to the location of the vehicle 12, that is, the above-described data to the generation unit 32.

  The generation unit 32 acquires data from the acquisition unit 30. The generation unit 32 generates a packet signal so as to store data. The packet signal also includes information for identifying the terminal device 14. The generation unit 32 outputs the generated packet signal to the modulation unit 34. The modulation unit 34 modulates the packet signal from the generation unit 32. As a modulation method, BPSK, QPSK, 16QAM, 64QAM and the like are defined. Also, the modulation unit 34 outputs the modulated result to the IFFT unit 36 as a baseband packet signal. Note that the baseband packet signal corresponds to an OFDM signal in the frequency domain. In general, baseband packet signals are formed by in-phase and quadrature components, so two signal lines should be shown, but here only one signal line is shown for clarity. Shall be shown.

  The IFFT unit 36 receives a baseband packet signal from the modulation unit 34. The IFFT unit 36 performs an IFFT (Inverse Fast Fourier Transform) to convert an OFDM signal in the frequency domain into an OFDM signal in the time domain. A time-domain OFDM signal is also referred to as a baseband packet signal. As a transmission process, the radio unit 22 performs frequency conversion on the baseband packet signal input from the IFFT unit 36 to generate a radio frequency packet signal. Further, the radio unit 22 broadcasts a radio frequency packet signal from the antenna 20. The wireless unit 22 includes a PA (Power Amplifier), a mixer, and a D / A conversion unit. As described above, the packet signal is transmitted in accordance with an access control function called CSMA / CA, similarly to a wireless LAN compliant with a standard such as IEEE 802.11.

  As a reception process, the radio unit 22 receives a packet signal notified from another terminal device 14 (not shown) by the antenna 20. The radio unit 22 performs frequency conversion on a radio frequency packet signal received via the antenna 20 to generate a baseband packet signal. Here, the baseband packet signal is an OFDM signal in the time domain. Further, the radio unit 22 outputs a baseband packet signal to the receiving unit 26. The wireless unit 22 also includes an LNA (Low Noise Amplifier), a mixer, an AGC, and an A / D conversion unit.

  The synchronization unit 38 inputs the time-domain OFDM signal received by the radio unit 22. The synchronization unit 38 detects a synchronization timing when the FFT unit 42 described later converts the time domain OFDM signal into the frequency domain OFDM signal based on the time domain OFDM signal. Here, the synchronization timing corresponds to a window timing for executing FFT. For detecting the synchronization timing, a known technique may be used. For example, autocorrelation processing or cross-correlation processing is performed. The synchronization unit 38 detects the peak of the correlation value as the synchronization timing. When executing the cross-correlation process, the synchronization unit 38 stores a known signal pattern in advance. The synchronization unit 38 notifies the setting unit 40 of the synchronization timing. The synchronization timing is detected for each packet signal.

  The setting unit 40 receives the synchronization timing from the synchronization unit 38 when the synchronization unit 38 detects the synchronization timing. The setting unit 40 sets the synchronization timing in the FFT unit 42. The FFT unit 42 inputs the time-domain OFDM signal input by the receiving unit 26. When the setting unit 40 sets the synchronization timing, the FFT unit 42 performs FFT at the window timing corresponding to the synchronization timing. As a result, the FFT unit 42 converts the time domain OFDM signal into a frequency domain OFDM signal. The frequency domain OFDM signal is formed by a plurality of subcarrier signals. The FFT unit 42 performs FFT based on an arbitrary timing when the synchronization timing is not set by the setting unit 40. Regardless of when the synchronization timing is set or when the synchronization timing is not set, the FFT unit 42 outputs the frequency domain OFDM signal to the detection unit 48. When the synchronization timing is set, the FFT unit 42 outputs the frequency domain OFDM signal to the demodulation unit 44.

  The demodulator 44 receives the frequency domain OFDM signal from the FFT unit 42 when the setting unit 40 sets the synchronization timing in the FFT unit 42. The demodulator 44 demodulates the frequency domain OFDM signal. As described above, since the OFDM signal in the frequency domain is formed by a plurality of subcarrier signals, the demodulation unit 44 performs a demodulation process on each of the plurality of subcarrier signals. The demodulation unit 44 outputs the demodulated result to the notification unit 46.

  The notification unit 46 receives the demodulation result from the demodulation unit 44. The notification unit 46 processes the demodulation result to obtain information on the location of other vehicles included in the packet signal. The notification unit 46 detects the approach of the other vehicle based on the information related to the location of the other vehicle. At that time, the notification unit 46 may receive information on the location of the host vehicle from the acquisition unit 30. Further, the notification unit 46 notifies the driver of an approach or the like via a monitor or a speaker (not shown). A collision accident is prevented when the driver recognizes the approach of another vehicle. When notifying the approach of another vehicle on the monitor, the notification unit 46 may synthesize an image of the other vehicle on the map image displayed by the car navigation device.

  The measurement unit 52 receives the OFDM signal in the frequency domain converted by the FFT unit 42 regardless of whether the synchronization timing is set by the setting unit 40. Measurement unit 52 measures received power for each of a plurality of subcarrier signals forming an OFDM signal in the frequency domain. Measurement unit 52 may average received power for each of the plurality of subcarrier signals over a predetermined period. Measurement unit 52 outputs received power for each of the plurality of subcarrier signals to moving average unit 54.

  The moving average unit 54 receives the received power for each of the plurality of subcarrier signals from the measurement unit 52. The moving average unit 54 derives a moving average value in the frequency domain for the received power of the plurality of subcarrier signals. More specifically, the moving average unit 54 sets windows corresponding to ten consecutive subcarrier signals, and averages received power included in the windows. The moving average unit 54 derives an average value corresponding to each subcarrier signal by moving the window from the low frequency side to the high frequency side of the communication system band 114 of FIG. Each of these average values corresponds to a moving average value. The moving average unit 54 outputs each moving average value to the derivation unit 56.

  The deriving unit 56 receives a plurality of moving average values from the moving average unit 54. Each of the plurality of moving average values is associated with a frequency in the communication system band 114. The deriving unit 56 derives the slope of the received power from the low frequency side to the high frequency side of the OFDM signal in the frequency domain based on the moving average value. Specifically, the deriving unit 56 extracts a moving average value corresponding to a point on the low frequency side of the communication system band 114 (hereinafter referred to as “low frequency side moving average value”). The deriving unit 56 also extracts a moving average value corresponding to one point on the high frequency side (hereinafter referred to as “high frequency side moving average value”). Furthermore, the deriving unit 56 derives a slope from the low frequency side moving average value to the high frequency side moving average value. That is, the deriving unit 56 derives the slope based on a predetermined number of subcarrier signals among a plurality of subcarrier signals forming the frequency domain OFDM signal. Note that the slope may be derived by processing other than this, for example, by using the least square method. The derivation unit 56 outputs the inclination to the comparison unit 58.

  The comparison unit 58 receives the inclination from the derivation unit 56. In addition, the comparison unit 58 stores a threshold value for the inclination. The comparison unit 58 derives the absolute value of the slope, and when the absolute value of the slope is greater than the threshold value, the received power of the frequency domain OFDM signal is reduced from one frequency side of the frequency domain OFDM signal to the other. It is detected that there is an upward trend toward the frequency side. The comparison unit 58 accepts both the low frequency side moving average value and the high frequency side moving average value from the derivation unit 56, and when the high frequency side moving average value is larger than the low frequency side moving average value, One frequency side described above corresponds to the low frequency side, and the other frequency side corresponds to the high frequency side. Further, when the moving average value on the low frequency side is larger than the moving average value on the high frequency side, the one frequency side described above corresponds to the high frequency side, and the other frequency side corresponds to the low frequency side. On the other hand, when the absolute value of the slope is not larger than the threshold value, the comparison unit 58 detects that the OFDM signal in the frequency domain does not have an upward tendency. When the comparison unit 58 has an upward tendency, the comparison unit 58 outputs the fact and information on the frequency having the larger moving average value to the estimation unit 50.

  4A to 4D show an outline of processing of the detection unit 48. FIG. 4A to 4D, the horizontal axis indicates the frequency, and the vertical axis indicates the power. FIG. 4A shows received power for each of a plurality of subcarrier signals measured by the measurement unit 52. FIG. 4B shows the moving average value derived by the moving average unit 54. Here, the above-mentioned “one point on the low frequency side” is indicated as “f1”, and “one point on the high frequency side” is indicated as “f2”. Further, the above-mentioned “low frequency side moving average value” is indicated as “P1”, and “high frequency side moving average value” is indicated as “P2”. FIG. 4C shows the moving average value as in FIG. 4B, but corresponds to the case where the absolute value of the slope is large. Here, the case where the high frequency side moving average value is larger than the low frequency side moving average value is shown. FIG. 4D shows the moving average value when the absolute value of the slope is large, as in FIG. FIG. 4D shows a case where the low frequency side moving average value is larger than the high frequency side moving average value, unlike FIG. 4C. Returning to FIG.

  When the detecting unit 48 detects an upward tendency, the estimating unit 50 receives that fact and information on the frequency having the larger moving average value. Upon receiving these, the estimation unit 50 estimates the presence of interference power on the frequency side with the larger moving average value. For example, the presence of interference power on the low frequency side is estimated if the moving average value on the low frequency side is larger, and the presence of interference power on the high frequency side is estimated if the moving average value on the high frequency side is larger. . According to FIG. 2, the interference power on the low frequency side corresponds to the interference power due to the terrestrial digital broadcast 102, and the interference power on the high frequency side corresponds to the interference power due to the mobile phone system 104. The estimation unit 50 outputs the estimation result to the notification unit 46.

  When the presence of interference power on the low frequency side is estimated, the notification unit 46 notifies the driver that there is interference from the terrestrial digital broadcast 102. On the other hand, the notification unit 46 notifies the driver that there is interference by the mobile phone system 104 when the presence of interference power on the high frequency side is estimated. At that time, the driver can reduce interference with the communication system 100 by turning off the power of the mobile phone. Note that the detection unit 48 and the estimation unit 50 execute the processing regardless of whether the synchronization timing is set by the setting unit 40. The control unit 28 controls the timing of the entire terminal device 14.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it can be realized by a program loaded in the memory, but here it is realized by their cooperation. Draw functional blocks. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The operation of the terminal device 14 configured as above will be described. FIG. 5 is a flowchart illustrating a procedure of reception processing by the terminal device 14. When the timing synchronization is not established in the synchronization unit 38 (N in S10), the FFT unit 42 executes FFT at an arbitrary window timing (S12). The detection unit 48 performs detection processing based on the OFDM signal subjected to the FFT (S14). On the other hand, when the timing synchronization is established in the synchronization unit 38 (Y in S10), the FFT unit 42 executes the FFT at the synchronized window timing (S16). The demodulator 44 performs demodulation processing on the FFTed OFDM signal (S18). The detection unit 48 performs detection processing based on the OFDM signal subjected to the FFT (S20).

  FIG. 6 is a flowchart illustrating the procedure of the detection process performed by the terminal device 14. The measuring unit 52 measures received power (S40). The moving average unit 54 calculates a moving average with respect to the received power (S42). When P1 is larger than P2 (Y in S44), if the absolute value of the slope is larger than the threshold value (Y in S46), the estimation unit 50 estimates that interference from the terrestrial digital broadcast 102 has occurred. (S48). If the absolute value of the slope is not greater than the threshold value (N in S46), the process is terminated. When P1 is not larger than P2 (N in S44), if the absolute value of the slope is larger than the threshold value (Y in S50), the estimation unit 50 estimates that interference by the mobile phone system 104 has occurred. (S52). If the absolute value of the slope is not greater than the threshold value (N in S50), the process is terminated.

  Next, a modified example of the present invention will be described. The modification of this invention is related with the communication system which performs data communication between the terminal devices mounted in the vehicle similarly to the Example. In addition, the terminal device according to the modified example estimates the presence of interference power based on the slope of the received power, as in the embodiment. In the embodiment, after the received power for each of the plurality of subcarrier signals is measured, the slope is derived based on some of the values. That is, in the embodiment, selection is made following the measurement. On the other hand, in the modification, a subcarrier signal to be used for measurement is selected in advance from among a plurality of subcarrier signals, and the received power is measured for the selected subcarrier signal. Thereafter, the slope is derived. That is, in the modification, measurement is performed following selection. The communication system 100 and the terminal device 14 according to the modification are of the same type as those shown in FIGS. Therefore, here, the difference will be mainly described.

  The measurement unit 52 selects a low-frequency side subcarrier signal and a high-frequency side subcarrier signal from among the plurality of subcarrier signals forming the frequency domain OFDM signal converted by the FFT unit 42. . The selected subcarrier signal may be determined in advance. Measurement unit 52 measures the received power for the selected subcarrier signal. The measurement unit 52 may average the received power for the subcarrier signal over a predetermined period. The measuring unit 52 outputs received power to the deriving unit 56. The deriving unit 56 regards the received power for the low-frequency side subcarrier signal as the low-frequency side moving average value, regards the received power for the high-frequency side subcarrier signal as the high-frequency side moving average value, and executes the above-described processing. To do. In that case, the moving average part 54 becomes unnecessary.

  On the other hand, the measurement unit 52 may select two or more subcarrier signals as low frequency side subcarrier signals, and may select two or more subcarrier signals as high frequency side subcarrier signals. At that time, the measurement unit 52 measures received power for all the selected subcarrier signals. The moving average unit 54 averages received power for two or more subcarrier signals selected as low frequency side subcarrier signals. The averaged result is called the low frequency side average value. The moving average unit 54 also averages received power for two or more subcarrier signals selected as high frequency side subcarrier signals. The averaged result is called the high frequency side average value. The moving average unit 54 outputs the low frequency side average value and the high frequency side average value to the derivation unit 56. The deriving unit 56 regards the low frequency side average value as the low frequency side moving average value, regards the high frequency side average value as the high frequency side moving average value, and executes the above-described processing.

  FIG. 7 is a flowchart showing a procedure of detection processing by the terminal device 14 according to the modification of the present invention. The measuring unit 52 selects two points (S70) and measures received power (S72). When P1 is larger than P2 (Y in S74), if the absolute value of the slope is larger than the threshold value (Y in S76), the estimation unit 50 estimates that interference from the terrestrial digital broadcast 102 has occurred. (S78). If the absolute value of the slope is not greater than the threshold value (N in S76), the process is terminated. When P1 is not larger than P2 (N in S74), if the absolute value of the slope is larger than the threshold value (Y in S80), the estimation unit 50 estimates that interference by the mobile phone system 104 has occurred. (S82). If the absolute value of the slope is not greater than the threshold value (N in S80), the process is terminated.

  According to the embodiment of the present invention, in the frequency domain OFDM signal, the presence of interference power is detected by detecting whether or not the received power tends to increase from one frequency side to the other frequency side. Since the estimation is performed, the detection process can be executed regardless of whether timing synchronization is established. Further, since the detection process is executed regardless of whether timing synchronization is established, the influence of interference can be grasped. Even if timing synchronization is not established, the presence of interference can be grasped, so that early grasping can be realized. Moreover, since an early grasp is implement | achieved, the deterioration of quality can be suppressed. In addition, the detection process is the same regardless of whether timing synchronization is established, so that the switching process can be eliminated. In addition, since the switching process is unnecessary, the process can be simplified.

  Further, since the rising tendency is detected by comparing the received power with the threshold value, the processing can be simplified. Further, when the synchronization timing is detected, demodulation processing is executed, so that desired data can be acquired. In addition, since the detection process is performed while performing the demodulation process, the influence of the latest interference can be grasped. Further, since the detection process is executed for a predetermined number of subcarrier signals among the plurality of subcarrier signals, the processing amount can be reduced. Since the moving average is performed on the received power, the influence of noise can be reduced. In addition, since the influence of noise is reduced, the processing accuracy can be improved. Further, since the received power is measured only for the selected subcarrier signal, the processing amount can be reduced.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  12 vehicle, 14 terminal device, 20 antenna, 22 radio unit, 24 transmission unit, 26 reception unit, 28 control unit, 30 acquisition unit, 32 generation unit, 34 modulation unit, 36 IFFT unit, 38 synchronization unit, 40 setting unit, 42 FFT unit, 44 demodulation unit, 46 notification unit, 48 detection unit, 50 estimation unit, 52 measurement unit, 54 moving average unit, 56 derivation unit, 58 comparison unit, 100 communication system.

Claims (5)

An input for inputting time domain signals;
A conversion unit for converting a time domain signal input in the input unit into a frequency domain signal;
A detection unit that detects whether the reception power of the frequency domain signal converted by the conversion unit has a rising tendency from one frequency side of the frequency domain signal to the other frequency side;
An estimation unit that estimates the presence of interference power on the other frequency side when the detection unit detects an upward tendency;
A receiving apparatus comprising: Based on the time domain signal input in the input unit, the conversion unit detects a synchronization timing when converting the time domain signal to the frequency domain signal, and
A setting unit that sets the synchronization timing in the conversion unit when the synchronization unit detects the synchronization timing;
When the synchronization timing is set by the setting unit, the conversion unit performs conversion based on the synchronization timing, and when the synchronization timing is not set by the setting unit, based on an arbitrary timing. Perform the conversion,
The receiving device according to claim 1, wherein the detection unit and the estimation unit execute processing regardless of whether or not synchronization timing is set by the setting unit. When the synchronization timing is set by the setting unit, the demodulating unit further demodulates the frequency domain signal converted by the conversion unit,
The time domain signal input at the input unit is a time domain multi-carrier signal,
The conversion unit converts a multi-carrier signal in a time domain into a multi-carrier signal in a frequency domain by performing a Fourier transform,
The synchronization unit detects a window timing for executing Fourier transform as the synchronization timing,
The detection unit performs a detection process on a predetermined number of subcarrier signals among a plurality of subcarrier signals forming a frequency domain multicarrier signal,
The receiving apparatus according to claim 2, wherein the demodulating section performs demodulation processing on each of a plurality of subcarrier signals forming a multi-carrier signal in a frequency domain. The detector is
A measuring unit for measuring received power for each of a plurality of subcarrier signals forming a multi-carrier signal in the frequency domain converted by the converting unit;
4. An execution unit for deriving a moving average value in a frequency domain with respect to received power of a plurality of subcarrier signals measured by the measuring unit and executing detection processing on the moving average value. The receiving device described in 1. The detector is
A selection unit that selects one frequency-side subcarrier signal and the other frequency-side subcarrier signal among the plurality of subcarrier signals forming the frequency domain multicarrier signal converted by the conversion unit; ,
A measurement unit that measures received power for the subcarrier signal selected by the selection unit;
The receiving device according to claim 3, further comprising: an executing unit that executes a detection process on the received power measured by the measuring unit.

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