JP2009267945A - Short-range communication receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless receiving apparatus capable of reducing a burden of processing due to software in communication processing. <P>SOLUTION: An ASK demodulation section 4 demodulates a received signal in accordance with an ASK modulation system. A π/4 shift QPSK demodulation section 5 demodulates the received signal in accordance with a π/4 shift QPSK modulation system. A frame message analysis section 7 analyzes the signal demodulated by the ASK demodulation section 4 and the signal demodulated by the π/4 shift QPSK demodulation section 5 in a simultaneous parallel manner. A modulation system determination section 8 determines a modulation system of the received signal on the basis of an analysis result of the frame message analysis section 7, controls a switching section 10 to selectively output a signal from the ASK demodulation section 4 or from the π/4 shift QPSK demodulation section 5. The modulation system determination section 8 determines the modulation system and a communication velocity from a signal transmission rate identifier DRI contained in a CI signal of FCMC. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a narrow area communication receiver.

  In an expressway traffic system (ITS), communication is performed between a roadside device installed on the roadside and an onboard device installed on the vehicle side by narrow-range communication (DSRC).

In an ITS on-board device that supports ETC (Electronic Toll Collection) and next-generation ITS, ASK (Amplitude Shift Keying) and π / 4 shift QPSK (Quadrature)
It supports both modulation methods (Phase Shift Keying). That is, each roadside device uses any one of these modulation methods, and transmission / reception data using the ASK modulation method for one communication and transmission / reception data using the π / 4 shift QPSK modulation method are mixed. In some cases, the ITS vehicle-mounted device is compatible with such roadside devices. Therefore, in the ITS in-vehicle device, it is necessary to determine whether the downlink and uplink signals are of the ASK modulation method or the π / 4 shift QPSK modulation method.

With respect to this point, in the technique disclosed in Patent Document 1, it is determined whether the received signal uses the ASK modulation method or the π / 4 shift QPSK modulation method based on the unique word (UW) included in the received signal. Yes.
Japanese Patent Laid-Open No. 2005-5935

  However, in each slot included in one frame in the narrow area communication, a unique word is included in the downlink slot, but the uplink slot is transmitted from the ITS in-vehicle device side to the roadside device. Therefore, in order to determine the modulation method, it is necessary to analyze the FCMC (Frame Control Message Channel) located at the head of one frame.

  In addition, the signal speed of each slot included in one frame in narrowband communication may vary from slot to slot, and the communication speed of each slot cannot be determined by a unique word. To analyze FCMC.

  For these reasons, with the technology disclosed in Patent Document 1, the processing load by software in the communication processing becomes heavy, and in particular, the burden on the uplink increases.

  An object of the present invention is to provide a wireless reception device that can reduce the processing load by software in communication processing.

  The present invention comprises: a receiving means for receiving a signal for narrow-area communication; a first demodulating means for demodulating the signal received by the receiving means with a first demodulation method for demodulating the first modulation method; In parallel with the demodulation by the first demodulating means, the second demodulating means for demodulating the signal received by the receiving means by the second demodulating method for demodulating the second modulation method, and the first demodulating means Analyzing means for analyzing the first received signal later and the second received signal demodulated by the second demodulating means in parallel, and the signal received by the receiving means from the result of analysis by the analyzing means; Modulation method determining means for determining whether the modulation method is modulated by the first modulation method or the second modulation method, and has been modulated by the modulation method determined by the modulation method determining means The first reception signal or the second reception Selection output means for selectively outputting a signal, and processing means for performing predetermined processing based on the first reception signal or the second reception signal selectively output by the selection output means The modulation method determination means is a narrow-area communication receiver that indicates communication speed information and performs the determination based on a signal transmission speed identifier included in the first reception signal or the second reception signal. is there.

  According to the present invention, by analyzing the signal transmission rate identifier, it is easily determined whether the data to be uplinked should be based on the first modulation scheme or the second modulation scheme as well as the downlink data. can do. Further, information on the communication speed can be obtained simultaneously by analyzing the signal transmission speed identifier. Therefore, the signal transmission rate identifier can be analyzed by hardware, and the processing load by software can be reduced as compared to performing the processing based on software.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a functional block diagram of a narrow area communication receiver used in an ITS on-vehicle device. This narrow area communication receiving apparatus 1 is a receiving apparatus of an ITS vehicle-mounted device. A roadside device (not shown) installed on the roadside transmits a radio signal by DSRC (Dedicated Short Range Communication). The radio signal is transmitted to the ASK receiver 2 and the π / 4 shift QPSK receiver. 3 and simultaneously receive in parallel. The ASK receiving unit 2 receives a signal modulated by an ASK (Amplitude Shift Keying) modulation method, and the π / 4 shift QPSK receiving unit 3 is modulated by a π / 4 shift QPSK (Quadrature Phase Shift Keying) modulation method. Receive a signal.

  Then, the signal received by the ASK receiver 2 is demodulated by the ASK demodulator 4 by a demodulation method corresponding to the ASK modulation method. Further, the signal received by the π / 4 shift QPSK receiver 3 is demodulated by the π / 4 shift QPSK demodulator 5 by a demodulation method corresponding to the π / 4 shift QPSK modulation method. Demodulation in the ASK demodulator 4 and demodulation in the π / 4 shift QPSK demodulator 5 are performed in parallel.

  UW detector 6 detects a unique word (UW) from the signal demodulated by ASK demodulator 4 and the signal demodulated by π / 4 shift QPSK demodulator 5. The unique word UW is data for synchronizing each channel.

  The frame message analyzing unit 7 analyzes the frame message for each of the signal demodulated by the ASK demodulating unit 4 and the signal demodulated by the π / 4 shift QPSK demodulating unit 5.

  Based on the analysis result of the frame message analysis unit 7, the modulation method determination unit 8 determines whether the modulation method of the signal received by the narrowband communication receiver 1 is an ASK modulation method or a π / 4 shift QPSK modulation method.

  Based on the determination result of the modulation scheme determination unit 8, the timing control unit 9 is configured to receive an ASK reception unit 2, a π / 4 shift QPSK reception unit 3, an ASK demodulation unit 4, and a π / 4 shift. It controls the timing of operations of the QPSK demodulator 5 and the modulator and transmitter (not shown) related to signal transmission to the roadside device.

  The switching unit 10 switches to the signal after ASK demodulation output from the ASK demodulation unit 4 when the signal from the roadside unit is ASK modulated according to the determination result of the modulation scheme determination unit 8, and is subjected to π / 4 shift QPSK modulation. Is switched to the signal after the π / 4 shift QPSK demodulation output from the π / 4 shift QPSK demodulator 5. As described above, the switching unit 10 selectively outputs the signal after ASK demodulation or the signal after π / 4 shift QPSK demodulation to the processing unit 11 according to the determination result of the modulation method of the received signal.

  The processing unit 11 performs predetermined processing based on the signal output from the switching unit 10, displays necessary information on the display 12, or outputs a voice message from the speaker 13. Although not shown, the LED may blink or a buzzer may be sounded.

  Next, processing executed by the frame message analysis unit 7 will be described in detail. The communication between the roadside device and the ITS in-vehicle device described here is based on the “ARIB STD-T75” standard in the narrow area communication (DSRC) system. This is based on the slotted Aloha communication method, and the roadside machine performs communication at the initiative of the roadside machine side while dividing the slot.

  FIG. 2 is an explanatory diagram illustrating an example of a data configuration of one frame of a radio signal that is downlinked from the roadside unit to the ITS onboard unit and uplinked from the ITS onboard unit to the roadside unit. An FCMC (Frame Control Message Channel) 21 is provided at the beginning of one frame of data, and reference numeral 22 indicates each slot. In this example, communication between the ITS in-vehicle device and the roadside device is performed in a full-duplex method, and in one frame, the downlink (D / L) is equivalent to 4 slots (upper stage in FIG. 2), the uplink (U / L) is included for four slots (the lower part of FIG. 2). That is, the downlink slot 22 and the uplink slot 22 exist in the same time zone. The FCMC 21 designates which slot 22 is a downlink for an ITS in-vehicle device of a certain car, and designates in which slot 22 an uplink can be performed for an ITS on-vehicle device of a certain car. The FCMC 21 is included only in downlink data. Although not shown in FIG. 2, a preamble signal (PR) and a unique word signal (UW) are provided at the head portion of each downlink slot 22.

  FIG. 3 is an explanatory diagram for explaining the FCMS (frame control message slot) format of the FCMC 21. (A) shows the FCMS format in the case of the ASK modulation method, and (b) shows the FCMS format in the case of the π / 4 shift QPSK modulation method.

  The FCMC 21 includes information on what ITS on-board unit responds to what number slot 22. In addition, information (ASK modulation method or π / 4 shift QPSK modulation method) that specifies the modulation method used in the response is also included. The ITS on-board device analyzes the information and uplinks data in the designated slot 22 at a timing corresponding to the information.

  The FCMC 21 includes a 2 octet (for ASK modulation system) or 16 octet (for π / 4 shift QPSK modulation system) preamble signal (PR), a 4-octet unique word signal (UW1), and a 2-octet error. A check signal (CRC) is added, and guard times t0 and t2 are set before and after the check signal (CRC). In the case of the π / 4 shift QPSK modulation method, a 1-octet length (4 symbols) ramp bit (R) is added before the preamble signal PR.

  In addition, SCI signals from SCI (1) to SCI (8) are included, and each SCI signal includes CI signals (from CI (1) to CI (8)) and LID signals (from LID (1) to LID (8)). ).

  FIG. 4 is an explanatory diagram for explaining the format of the CI signal. The CI signal is composed of 8-bit data, and bit numbers 1 and 2 are slot identifiers (SI). The slot identifier SI is data indicating the attribute of the slot 22. The slot identifier SI indicates whether the slot 22 is allocated as MDS, ACTS, or WCNS.

  Bit numbers 5 to 7 can store a signal type identifier (ST) which is data indicating the contents of the MDC.

  Bit numbers 3 and 4 store a signal transmission rate identifier (DRI) for identifying the data transmission rate of MDC and WCNC.

  FIG. 5 is an explanatory diagram for explaining the contents of the signal transmission rate identifier DRI. Bit numbers 3 and 4 (b3 and b4) are “00” when the signal transmission rate is 1024 kbps in the ASK modulation method and “11” when the signal transmission rate is 4096 kbps in the π / 4 shift QPSK modulation method. In the case of “others”, the reservation is for system expansion.

  Therefore, by determining the value of the signal transmission rate identifier DRI, it is possible to determine whether each slot 22 is an ASK modulation system or a π / 4 shift QPSK modulation system. The communication speed can also be determined.

  The frame message analysis unit 7 described above analyzes the signal transmission rate identifier DRI included in the CI signal of the FCMC 21 to determine whether each slot 22 is an ASK modulation method or a π / 4 shift QPSK modulation method. In addition, the communication speed of each slot 22 can also be determined.

  FIG. 6 is a block diagram of an electrical description of a narrowband communication receiving apparatus 101 as a comparative example with respect to the narrowband communication receiving apparatus 1 described with reference to FIG. 6, components having the same reference numerals as those in FIG. 1 are the same as those in the narrow area communication receiver 1 described above with reference to FIG.

  The narrow-area communication receiver 101 is different from the narrow-area communication receiver 1 in that the ASK demodulator 4 and the π / 4 shift QPSK demodulator 5 are alternately switched by the switching unit 10 and the ASK demodulator 4 is switched. And the signal from the π / 4 shift QPSK demodulating unit 5 are alternately input to the modulation scheme determining unit 8. Thereby, the modulation scheme determination unit 8 determines, for example, the signal from the ASK demodulation unit 4 out of the signal from the ASK demodulation unit 4 and the signal from the π / 4 shift QPSK demodulation unit 5, and the signal is ASK modulated. If it is not ASK modulation, the signal from the π / 4 shift QPSK demodulator 5 is determined to determine whether the signal is π / 4 shift QPSK modulation. When the modulation method is known in this way, the switching unit 10 demodulates the signal from the modulation method (the signal from the ASK demodulation unit 4 if ASK modulation, the signal from the π / 4 shift QPSK demodulation unit 5 if π / 4 shift QPSK modulation). ) To output the signal to the processing unit 11.

  In this narrow area communication receiver 101, unlike the narrow area communication receiver 1, the modulation scheme of the signal from the ASK demodulator 4 and the signal from the π / 4 shift QPSK demodulator 5 is not specified simultaneously. Instead, the switching unit 10 switches between the signal from the ASK demodulator 4 and the signal from the π / 4 shift QPSK demodulator 5, and the signal from the ASK demodulator 4 and the signal from the π / 4 shift QPSK demodulator 5 Are alternately determined to specify the modulation method.

  Therefore, it takes a lot of time to specify the modulation method. And since the narrow area communication of this system is performed between the moving car and the roadside machine, it takes a long time to specify the modulation method, and the communication area is apparently narrowed. There is a bug.

  On the other hand, the narrow area communication receiver 1 specifies the modulation scheme by simultaneously determining the signal from the ASK demodulator 4 and the signal from the π / 4 shift QPSK demodulator 5, so that the modulation scheme Since it takes only a short time to specify the communication area, the communication area can be apparently enlarged.

  As described above, a unique word (UW) is provided at the beginning of each downlink slot 22. FIG. 7 is an explanatory diagram for explaining the unique word UW in each of the ASK modulation method and the π / 4 shift QPSK modulation method. The unique word UW2 is used in the downlink slot 22 in the case of the ASK modulation scheme, and the unique words UW2A and UW2B are used in the downlink slot 22 in the case of the π / 4 shift QPSK modulation scheme. Then, by analyzing the unique word UW of each downlink slot 22, it is possible to determine whether the modulation scheme used in the downlink is the ASK modulation scheme or the π / 4 shift QPSK modulation scheme.

  However, in the case of the uplink, it is necessary to analyze the FCMC 21 and determine what data is to be uplinked in the slot 22.

  For these reasons, if the detection of the unique word UW and the analysis of the FCMC 21 are performed by processing based on software to determine the modulation method, the burden of processing by software in the communication processing becomes heavy.

  On the other hand, the narrow area communication receiver 1 can determine the modulation scheme at high speed by hardware in all the uplink and downlink slots 22 by analyzing the signal transmission rate identifier DRI included in the FCMC 21. In addition, since the communication speed of each slot 22 can be determined, the processing load based on software in the communication process can be reduced.

It is a functional block diagram of the narrow region communication receiver used for the ITS onboard equipment which is one embodiment of this invention. It is explanatory drawing which shows the data structure of 1 frame of the radio signal downlinked to the ITS onboard equipment from the roadside machine, and uplinked from the ITS onboard equipment to the roadside machine. It is explanatory drawing explaining the FCMS format of FCMC. It is explanatory drawing explaining the format of CI signal. It is explanatory drawing explaining the content of a signal transmission speed identifier. It is a block diagram of the electrical description of the narrow region communication receiver used as a comparative example. It is explanatory drawing explaining the unique word in each case of an ASK modulation system and a (pi) / 4 shift QPSK modulation system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Narrow-area communication receiver 2 ASK receiver 3 π / 4 shift QPSK receiver 4 ASK demodulator 5 π / 4 shift QPSK demodulator 6 UW detector 7 Frame message analyzer 8 Modulation method determiner 9 Timing controller 10 Switch Part 11 Processing part 12 Display 13 Speaker 21 FCMC
22 slots

Claims (1)

Receiving means for receiving a signal of narrow-area communication;
First demodulation means for demodulating a signal received by the reception means with a first demodulation method for demodulating a first modulation method;
A second demodulating means for demodulating the signal received by the receiving means in parallel with the demodulation by the first demodulating means by a second demodulation method for demodulating the second modulation method;
Analyzing means for analyzing in parallel each of the first received signal demodulated by the first demodulating means and the second received signal demodulated by the second demodulating means;
A modulation scheme determination unit that determines whether the modulation scheme of the signal received by the reception unit is modulated by the first modulation scheme or the second modulation scheme from the result of analysis by the analysis unit;
Selective output means for selectively outputting the first received signal or the second received signal that has been modulated by the modulation method determined by the modulation method determining means;
Processing means for performing predetermined processing based on the first reception signal or the second reception signal selectively output by the selection output means;
With
The modulation method determination means indicates the communication speed information and performs the determination based on a signal transmission rate identifier included in the first reception signal or the second reception signal.
Narrow area communication receiver.

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