JP2008306274A - Word detecting device, method and program, and reception device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a word detecting device, a word detecting method, a word detecting program and a reception device, which can set the threshold of a reception electric power level in order to allow or disallow unique word detecting operation into the optimum level. <P>SOLUTION: This word detecting device detects a predetermined word included in one or a plurality of reception signals respectively, and is equipped with a reception power level detecting means of detecting a reception power level of each reception signal, a word detecting means of collating respective reception signals to words and detecting the words included in the respective reception signals based upon correlation results, and a word detecting operation control means of controlling word detecting operation by the word detecting means according to the reception power levels of the respective reception signal detected by the reception power level detecting means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a word detecting device, method and program, and a receiving device, for example, a word detecting device and method for detecting a unique word on the receiving vehicle side in a vehicle-to-vehicle communication system for exchanging information between vehicles by wireless communication. And a program and a receiving apparatus.

  For example, in one application application of the inter-vehicle communication system, multiple vehicles exchange vehicle control information such as their vehicle position and speed with each other at a predetermined update period, preventing encounter accidents, right-straight accidents and rear-end collisions. There is a safety support system application.

  In order to realize such a safety support system application, high communication quality is required in the inter-vehicle communication system. For this reason, for example, the receiving apparatus needs to have an error correction function as described in Patent Document 1 and Non-Patent Document 1.

  As a result, even in an environment where radio wave propagation characteristics are severe under a multipath environment such as an inter-vehicle communication system, it is possible to realize a low BER communication quality at a low CNR by using an error correction code having a high correction capability. .

Japanese National Patent Publication No. 11-511607 Wireless Data Communication Study Group, “Introduction to Wireless Data Communication 1994”, Soft Research Center, p. 125-p.127

  However, the receiving apparatus applied to the conventional inter-vehicle communication system has the following problems.

  As described above, in the existing vehicle-to-vehicle communication system, correction coding processing with high correction capability is used. Therefore, the CNR (Carrier vs Noise Ratio), that is, the received power allowed by this correction processing is used. The lower limit of the level is lowered.

  In order to successfully receive a packet, not only the communication quality of a portion to which an error correction code such as a data portion is applied, but also the performance of unique word detection must be improved.

  In order to improve the unique word non-detection rate characteristic and to accurately detect the unique word that should be detected, it is necessary to lower the threshold of the reception power level that determines whether or not the unique word detection operation is possible.

  However, if the threshold of the received power level is lowered too much, the unique word detection operation is excessively allowed, and there is a possibility that the false detection rate of a unique word that detects a portion that is not an original unique word as a unique word increases.

  Therefore, there is a need for a word detection device, a method and a program, and a reception device that can set the threshold of the reception power level to an optimum value for whether or not the unique word detection operation is possible.

  In order to solve such a problem, a word detection device according to a first aspect of the present invention is a word detection device that detects a predetermined word that can be included in each of one or a plurality of reception signals. (1) Reception of each reception signal Received power level detecting means for detecting a power level; (2) word detecting means for taking a correlation between each received signal and a word and detecting a word included in each received signal based on the correlation result; and (3) And a word detection operation control means for controlling the word detection operation by the word detection means in accordance with the reception power level of each received signal detected by the reception power level detection means.

  A word detection method according to a second aspect of the present invention is a word detection method for detecting a predetermined word that can be included in each of one or a plurality of received signals. (1) The received power level detecting means receives the received power of each received signal. A reception power level detection step for detecting a level; and (2) a word detection step in which the word detection means correlates each reception signal with a word and detects a word included in each reception signal based on the correlation result; (3) The word detection operation control means includes a word detection operation control step for controlling the word detection operation by the word detection means in accordance with the reception power level of each received signal detected by the reception power level detection means. It is characterized by.

  A word detection program according to a third aspect of the present invention is a word detection program for detecting a predetermined word that can be included in each of one or a plurality of received signals, and (1) detects a received power level of each received signal. Received power level detection means, (2) Word detection means for taking a correlation between each received signal and a word, and detecting a word contained in each received signal based on the correlation result, (3) Detected by received power level detection means It functions as a word detection operation control means for controlling the word detection operation by the word detection means in accordance with the received power level of each received signal.

  According to a fourth aspect of the present invention, there is provided a receiving apparatus including the word detecting apparatus according to the first aspect of the present invention.

  According to the present invention, the threshold of the received power level can be set to an optimum value for whether or not the unique word detection operation is possible.

(A) First Embodiment A word detection device, method and program, and a first embodiment of a reception device according to the present invention will be described below with reference to the drawings.

  In the first embodiment, in a vehicle-to-vehicle communication system that exchanges various types of information with a communication device provided in one or more other vehicles existing in the vicinity, vehicle control information such as position information and speed information of the own vehicle is obtained. A case where the present invention is applied to a communication apparatus that applies a safety support system application that exchanges each other at predetermined intervals and realizes various traffic safety support will be described as an example.

(A-1) Configuration of First Embodiment FIG. 1 is a functional block diagram illustrating an internal configuration of a receiving device according to the first embodiment. FIG. 2 is a functional block diagram illustrating an internal configuration of the transmission apparatus according to the first embodiment. Each vehicle is equipped with the transmission device of FIG. 2 and the reception device of FIG.

  2, the transmission device 100 according to the first embodiment includes at least a transmission data generation unit 101, a transmission packet generation unit 102, a vehicle ID generation unit 103, a packet transmission unit 104, and a transmission antenna 105. .

  The transmission data generation unit 101 generates transmission data 1 to be transmitted to another vehicle and gives the transmission data 1 to the transmission packet generation unit 102. As the transmission data 1, for example, vehicle information such as position information and speed information of the host vehicle is applicable.

  The vehicle ID generation unit 103 provides the transmission packet generation unit 102 with identification information (for example, vehicle ID 2 in the first embodiment) set in advance when transmitting transmission data.

  The transmission packet generation unit 102 adds a predetermined packet header, a unique word, etc. to the transmission data 1 from the transmission data generation unit 101 and the vehicle ID 2 from the vehicle ID generation unit 103, or performs error correction coding or the like. Thus, the transmission packet 3 is generated. The transmission packet generation unit 102 gives the generated transmission packet 3 to the packet transmission unit 104. Here, as an error correction encoding process applied to the inter-vehicle communication system, an existing error correction encoding process with high error correction capability can be widely applied (see Non-Patent Document 1).

  The packet transmission unit 104 receives the transmission packet 3 from the transmission packet generation unit 102, and transmits the transmission packet 4 via the transmission antenna 105 according to a predetermined communication method. Here, for example, a CSMA (Carrier Sense Multiple Access) method is applied as a predetermined communication method in the packet transmission unit 104, but the present invention is not limited to this, and can be widely applied.

  In FIG. 1, a receiving apparatus 200 according to the first embodiment includes a packet receiving unit 201, a receiving antenna 202, a unique word detecting unit 203, a received power level detecting unit 204, a received packet decomposing unit 205, a received data storage unit 206, a communication. It includes at least a vehicle number estimation unit 207, a packet reception end time detection unit 208, a reception power level threshold determination unit 209, a control parameter storage unit 210, and a unique word detection operation availability determination unit 211.

  The receiving antenna 202 captures an incoming radio wave and provides the radio wave signal to the packet receiving unit 201.

  The packet reception unit 201 receives a communication channel signal of a predetermined communication channel via the reception antenna 202, and performs a predetermined demodulation process to generate a reception signal 6. Further, the packet reception unit 201 gives the generated reception signal 6 to the unique word detection unit 203 and the reception power level detection unit 204.

  The unique word detection unit 203 detects a unique word from the reception signal 6 from the packet reception unit 201 in accordance with the control from the unique word detection operation availability determination unit 211.

  That is, when the unique word detection unit 203 receives the unique word detection operation control signal 16 indicating “ON” from the unique word detection operation availability determination unit 211, the unique word detection unit 203 performs the unique word detection operation and detects the unique word indicating “OFF”. When the operation control signal 16 is received, the unique word detection operation is not performed.

  As a unique word detection method by the unique word detection unit 203, existing unique word detection methods can be widely applied. For example, the correlation value between the received signal 6 and the unique word is acquired, and when the correlation value exceeds the threshold value and reaches the maximum value, the presence of the unique word is detected, and the timing is set to the synchronization timing. It is possible to apply a method such as

  The unique word detection unit 203 gives the received packet 7 to the received packet decomposing unit 205. In addition, when the unique word detection unit 203 detects a unique word, the unique word detection unit 203 notifies the timing at which the magnitude of the correlation value becomes the maximum value as the synchronization timing.

  The reception power level detection unit 204 detects the reception power level of the reception signal 6 received by the packet reception unit 201, and the detected reception power level 3 of the reception signal 6 is determined as a unique word detection operation availability determination unit. 211.

  The received packet decomposing unit 205 extracts the other vehicle ID 9 and the received data 8 by performing an error correction decoding process on the received packet 7 from the unique word detecting unit 203. The received packet decomposition unit 205 gives the other vehicle ID 9 and the received data 8 to the received data storage unit 206 and also gives the other vehicle ID 9 to the communication vehicle number estimating unit 207.

  When the reception packet decomposition unit 205 ends the reception of the reception packet 7 which is the basis of the reception data 8 and the other vehicle ID 9, the packet reception end signal 12 indicating the reception end timing of the reception packet 7 is sent to the packet reception end time. This is given to the detection unit 208.

  The reception data storage unit 206 stores the reception data 8 and the other vehicle ID 9 received from the reception packet decomposition unit 205 and gives them to a higher-level application or the like as necessary.

  The communication vehicle number estimating unit 207 receives the other vehicle ID 9 extracted by the received packet decomposing unit 205 and counts the number of different other vehicle IDs received within a predetermined period set in advance. Thereby, the number of vehicles with which the own vehicle is currently communicating can be estimated. In addition, the communication vehicle number estimation unit 207 gives the communication vehicle number estimation value 11 within a predetermined period to the received power level threshold value determination unit 209.

  When the packet reception end time detection unit 208 receives the packet reception end signal 13 from the reception packet decomposition unit 205, the packet reception end time detection unit 208 detects the reception end time of the packet, and determines the detected packet reception end time 14 as a reception power level threshold value. This is given to the unit 209.

  The control parameter storage unit 210 stores a transmission frequency table 210a indicating the transmission frequency of packets transmitted per predetermined period for each number of communication vehicles. That is, the transmission frequency table 210a is a table in which the probability that a unique word to be detected is transmitted per predetermined time is obtained for each number of vehicles.

  For example, in a vehicle-to-vehicle communication system to which a safety assistance system application is applied, each vehicle transmits a packet at a constant period. The packet length transmitted by each vehicle is regulated to some extent by the application type. Therefore, if the number of vehicles existing around the host vehicle is known, it is possible to estimate the transmission frequency of the unique word of the packet transmitted per predetermined time.

  For example, FIG. 3 is an example showing the configuration of the transmission frequency table 210a. As shown in FIG. 3, the transmission frequency table 210a is configured by associating the number of vehicles existing in the vicinity with the transmission frequency of packets (unique words) per predetermined time.

  As this transmission frequency table 210a, for example, a simulation is performed according to the specification of the assumed application type and / or the access control method type, and a preset table based on the result can be applied.

  Accordingly, the transmission frequency table 210a may be created for each application type, for example, for each access control method, and for each application type and access control method. It may be created.

  Although not shown in FIG. 1, the received packet decomposing unit 205 may be provided with an application type identifying function for extracting application identifying information from the header portion of the received packet as necessary. In general, since the unique word varies depending on the transmission method, the unique word detection unit 203 may have a unique word identification function. Thereby, the transmission frequency table 210a to be used can be specified for each application type and / or for each access control method.

  The reception power level threshold value determination unit 209 includes the communication vehicle number estimation value 11 from the communication vehicle number estimation unit 207, the control parameter 12 from the control parameter storage unit 210, and the packet reception end time from the packet reception end time detection unit 208. 14 and a reception power level threshold 14 for determining whether or not the unique word detection operation can be performed (ON or OFF) corresponding to the number of communication vehicles and the elapsed time from the end of packet reception based on the current time. is there.

  Also, the received power level threshold value determination unit 209 gives the determined received power level threshold value 15 to the unique word detection operation availability determination unit 211.

  When receiving the received power level threshold 15 from the received power level threshold determining unit 209, the unique word detection operation availability determination unit 211 calculates the received power level 3 and the received power level threshold 15 of the packet from the received power level detector 204. The comparison is performed, and whether or not the unique word detection operation is possible is determined according to the comparison result.

  Specifically, when the received power level 3 is equal to or higher than the received power level threshold 15, the unique word detection operation determining unit 211 operates the unique word detection process (ON) and is smaller than the received power level threshold 15. The unique word detection process is not operated (OFF).

  The unique word detection operation availability determination unit 211 gives the unique word detection unit 203 a unique word detection operation control signal 16 indicating whether or not the determined unique word detection operation is possible.

(A-2) Operation of the First Embodiment Next, the operation of the unique word detection control process of the first embodiment will be described with reference to the drawings.

  FIG. 4 is an operation flowchart illustrating transmission processing by the transmission device 100 of each vehicle according to the first embodiment.

  First, in order to exchange vehicle information between vehicles, when each vehicle discloses its transmission process (step S101), the transmission data generation unit 101 creates transmission data 1 (step S102). ). At this time, the vehicle ID generation unit 103 generates the host vehicle ID 2 of the vehicle (step S102).

  When the transmission data 1 generated by the transmission data generation unit 101 and the own vehicle ID 2 generated by the vehicle ID generation unit 103 are given to the transmission packet generation unit 102, the transmission data generation unit 102 transmits the transmission data 1 and the own vehicle ID 2. Then, error correction coding processing and the like are performed to generate a transmission packet 3 (step S103).

  When the transmission packet 3 generated by the transmission packet generation unit 102 is given to the packet transmission unit 104, the packet transmission unit 104 performs access control using, for example, the CSMA method, and the transmission packet 4 is transmitted via the transmission antenna 105. (Step S104).

  At this time, if there is another transmission packet, the process returns to step S102, and the process is repeated. When the packet transmission is completed, the process ends (step S105).

  Next, reception processing of each vehicle according to the first embodiment will be described with reference to the drawings. 5 and 6 are operation flowcharts illustrating the reception processing by the reception device 200 of each vehicle according to the first embodiment.

  In each vehicle, the reception antenna 202 captures the incoming radio wave, and the communication channel signal 5 is received by the packet reception unit 201, subjected to predetermined demodulation processing, and the reception signal 6 is generated (steps S201 to S203). ).

  When the reception signal 6 is generated by the packet reception unit 201, the reception power level detection unit 204 detects the reception power level 3 of the reception signal 6 (step S204).

  Then, the received power level 3 is compared with the received power level threshold 15 by the unique word detection operation enable / disable determining unit 211 (step S205). If the received power level 3 is equal to or higher than the received power level threshold 15, the unique word detecting unit A unique word detection operation control signal (= ON) 16 for giving a unique word detection operation to 203 is given (step S206), and when the received power level is smaller than the received power level threshold value 15, unique word detector 203 is unique. A unique word detection operation control signal (= OFF) 16 that does not allow the word detection operation is given (step S207).

  The unique word detection operation availability determination unit 211 has an initial value of the reception power level threshold 15 in advance, and the initial value of the reception power level threshold 15 is used in the initial process of packet reception. May be.

  Thus, when the unique word detection operation control signal (= OFF) 16 is given to the unique word detection unit 203, the unique word detection operation is not performed (steps S208 and S209).

  On the other hand, when the unique word detection operation control signal (= ON) 16 is given in the unique word detection unit 203 (step S208), the unique word detection operation is performed (step S210), and the unique word included in the reception signal 6 is detected. A word is detected (step S211).

  At this time, when the unique word is not detected from the received signal 6, the process returns to step S208 and is repeated.

  Further, when the unique word included in the received signal 6 is detected by the unique word detection unit 203, the received packet decomposition unit 205 uses the detection timing of the maximum value of the correlation value related to the unique word detection process as a synchronization timing. The received data 8 and the other vehicle ID 9 are extracted from the received packet 7 (step S212).

  When the reception data decomposition unit 205 extracts the reception data 8 and the other vehicle ID 9, the other vehicle ID 9 is given to the communication vehicle number estimation unit 207, and the communication vehicle number estimation unit 207 counts different other vehicle IDs 9, respectively. The number of vehicles within a predetermined period of communication is estimated (step S213). Then, the estimated number of communication vehicles 11 is given to the received power level threshold value determination unit 209.

  The received data 8 and the other vehicle ID 9 extracted by the received packet decomposing unit 205 are given to the received data storage unit 206 and stored for the upper application (step S214).

  If the packet reception process has not been completed (step S215), the process returns to step S202 to repeat the process.

  On the other hand, when the reception processing of the packet is completed (step S215), the packet reception end signal 13 is given from the reception packet decomposition unit 205 to the packet reception end time detection unit 208 (step S216), and the packet reception end time 13 is generated. (Step S217), the packet reception end time 13 is given to the reception power level threshold value determination unit 209.

  Based on the packet reception end time 14 from the packet reception end time detection unit 208 and the current time, the reception power level threshold value determination unit 209 obtains an elapsed time from the packet reception end time to the current time.

  Further, the reception power level threshold value determination unit 209 refers to the transmission frequency table 210a of the control parameter storage unit 210, and obtains the transmission frequency per predetermined time corresponding to the current communication vehicle number estimated value 11.

  Based on the elapsed time from the reception end time of the packet to the current time and the transmission frequency per predetermined time with respect to the estimated number of communication vehicles 11, the received power level threshold determination unit 209 determines the current power level from the packet reception end time to the current time. A transmission frequency corresponding to the elapsed time up to the time is obtained, and a reception power level threshold corresponding to the transmission frequency corresponding to the elapsed time is determined (step S218).

  As a method for determining the received power level threshold, for example, a method for determining the received power level threshold using a predetermined arithmetic expression can be applied. For example, an arithmetic expression may be applied such that the reception power level threshold 15 is lowered when the transmission frequency of the unique word is high, and the reception power level threshold 15 is increased when the transmission frequency of the unique word is low.

  As another method, for example, a reception power level threshold determination table for setting the reception power level threshold 15 to be determined according to the transmission frequency is set in advance, and this reception power level threshold determination table is used to It is possible to apply a method for determining a received power level threshold according to the transmission frequency of communication.

  When the reception power level threshold value determination unit 209 determines the reception power level threshold value 15 in this way, the reception power level threshold value 15 is given to the unique word detection operation availability determination unit 211, and the reception power level threshold value 15 is updated. Using the received power level threshold value 15, it is determined whether or not the unique word detection operation according to the received power level 3 is possible.

(A-3) Effect of First Embodiment As described above, according to the first embodiment, the unique time according to the elapsed time from the packet reception end time to the current time and the number of vehicles performing communication. It is possible to set an optimum reception power level threshold value for whether or not the word detection operation is possible, and both the unique word non-detection rate and the false detection rate can be reduced.

(B) Other Embodiments (B-1) In the first embodiment, a case where the present invention is applied to a receiving device of an inter-vehicle communication system mounted on each vehicle has been described. The present invention can also be applied to a receiving device of a communication system.

  In this case, instead of the communication vehicle number estimation unit 207 that estimates the number of currently communicating communication vehicles, it can be realized by including a function unit that estimates the number of other communication terminals located in the vicinity of the own device. .

(B-2) The functions of the transmission device 100 and the reception device 200 described in the first embodiment can be realized by software processing. That is, various functions of the transmission apparatus 100 and the reception apparatus 200 described above can be realized by a CPU or DSP executing a predetermined processing program. Of course, if possible, it may be realized by hardware processing.

  In the first embodiment, the case where a unique word is detected has been described. However, the present invention is not limited to a unique word and can be widely applied to word detection.

It is a functional block diagram which shows the internal structure of the receiver of 1st Embodiment. It is a functional block diagram which shows the internal structure of the transmitter of 1st Embodiment. It is explanatory drawing explaining the structural example of the transmission frequency table of 1st Embodiment. It is an operation | movement flowchart which shows the transmission process of 1st Embodiment. It is an operation | movement flowchart which shows the reception process of 1st Embodiment (the 1). It is an operation | movement flowchart which shows the reception process of 1st Embodiment (the 2).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 200 ... Receiver, 201 ... Packet receiving part, 202 ... Reception antenna, 203 ... Unique word detection part, 204 ... Reception power level detection part, 205 ... Reception packet analysis part, 206 ... Reception data storage part, 207 ... Number of communication vehicles Estimating unit, 208... Packet reception end time detecting unit, 209... Reception power level threshold determining unit, 210... Control parameter storage unit, 211.

Claims (6)

In a word detection device for detecting a predetermined word that can be included in each of one or a plurality of received signals,
Received power level detecting means for detecting the received power level of each received signal;
A word detecting means for taking a correlation between each received signal and the word and detecting the word included in each received signal based on the correlation result;
A word detection device comprising: word detection operation control means for controlling a word detection operation by the word detection means in accordance with the reception power level of each received signal detected by the reception power level detection means. The word detection operation control means is
A reception power level threshold determination unit that estimates the frequency of detection of the word based on the number of communication destinations currently communicating, and determines a reception power level threshold according to the frequency of detection of the word;
The received power level threshold value determined by the received power level threshold value determining unit is compared with the received power level of each received signal, and the received power level of each received signal is equal to or higher than the received power level threshold value. A word detection operation enable / disable instruction unit configured to execute a word detection operation and prevent the word detection operation from being executed when a reception power level of each received signal is smaller than the reception power level threshold value. Item 2. The word detection device according to Item 1. The word detection operation control means is
Establishing synchronization based on the word detection result by the word detection means, and a received signal analyzer for analyzing the received signal;
Based on the communication destination identification information of the received signal analyzed by the received signal analysis unit, a communication destination number estimation unit for obtaining an estimated value of the communication destination number currently communicating within a predetermined period;
Based on the analysis result of the reception signal analysis means, a reception end time acquisition unit that acquires the reception end time of the reception signal;
A transmission frequency storage unit that stores the transmission frequency of the word that can be transmitted per predetermined time in advance for each number of communication destinations;
The received power level threshold value determining unit refers to the transmission frequency of the word per predetermined time and receives the received signal based on the elapsed time from the reception end time of the received signal to the current time and the estimated number of communication destinations. The word detection device according to claim 2, wherein a power level threshold is determined. In a word detection method for detecting a predetermined word that can be included in each of one or a plurality of received signals,
A reception power level detection step, wherein the reception power level detection means detects the reception power level of each reception signal;
A word detection step in which word detection means correlates each received signal and the word, and detects the word included in each received signal based on the correlation result;
A word detection operation control means for controlling the word detection operation by the word detection means in accordance with the reception power level of each received signal detected by the reception power level detection means. Characteristic word detection method. In a word detection program for detecting a predetermined word that can be included in each of one or a plurality of received signals,
On the computer,
Received power level detecting means for detecting the received power level of each received signal;
A word detecting means for taking a correlation between each received signal and the word and detecting the word included in each received signal based on the correlation result;
A word detection program which functions as a word detection operation control means for controlling a word detection operation by the word detection means in accordance with the reception power level of each received signal detected by the reception power level detection means.   A receiving device comprising the word detection device according to claim 1.

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