JP2008098827A - Device and method for detecting unique word - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for detecting a unique word from a packet transmitted and received in a radio communication such as a communication between vehicles. <P>SOLUTION: The device 10 for detecting the unique word uses a pattern containing an original unique word as a first unique word in a receiving packet, and uses the pattern composed of a part of the first unique word as a second unique word. The device 10 detects the first and second unique words respectively on the basis of the receiving packet in first and second unique-word detecting sections 12 and 14. The device 10 can improve throughput characteristics and unique-word detecting characteristics in the radio communication by determining the detection of the original unique word by a unique-word detection determination section 16 when both the first and second unique words are detected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus and method for detecting a unique word from a packet transmitted and received in wireless communication such as inter-vehicle communication.

  Conventionally, a unique word detection device is mounted on a communication terminal such as a vehicle-mounted device or a roadside device that transmits and receives a packet in wireless communication such as inter-vehicle communication, and detects a unique word inserted in a received packet. The position of the control field or data field (payload) of the packet can be detected.

  A unique word consists of a known pattern in all terminals, and the unique word detection device detects a unique word if it detects data with the same pattern as the unique word from the demodulated signal of the received packet. Can be determined.

  With respect to a packet used in wireless communication, the positional relationship between a unique word and a control field and data field is determined in advance, so that the control field and data field can be detected by detecting the unique word.

  In wireless communication, the communication quality deteriorates due to the influence of the propagation environment and the bit error rate deteriorates, so it is difficult for the communication terminal to always receive all bit data corresponding to the unique word without error. .

  Therefore, in order to improve the detection characteristics of the unique word detecting device, a bit error at the time of detecting the unique word may be allowed. Here, the bit error is bit data that does not match the unique word among the data corresponding to the unique word in the received packet, and the number thereof is referred to as the bit error number. If the number of bit errors is equal to or less than a predetermined number, this detection apparatus allows a unique word detection, and this predetermined number is referred to as an allowable number of bit errors.

  However, when the number of allowable bit errors is increased, the number of cases where the unique word detection device erroneously determines that the received packet is detected as a unique word other than the original position of the unique word increases. Therefore, in the wireless communication system, it is desirable to determine the unique word size and the allowable number of bit errors so that the non-detection rate and the false detection rate of the unique word are lowered in consideration of propagation characteristics, that is, communication quality.

For example, in the receiver described in Patent Document 1, an information data decoder obtains a correlation value between a received signal sequence and a unique word by a correlator, and when this correlation value is higher than a predetermined threshold, header information error detection The decoder performs error detection decoding on the header information following the unique word.
International Publication No.99 / 07100

  However, in the conventional unique word detection device, in order to improve the unique word detection characteristic, it is necessary for the communication terminal to transmit and receive a packet having a large unique word size. However, if the unique word size is increased, the packet size is increased, so that the throughput characteristic in wireless communication is degraded. Therefore, in wireless communication, it is necessary to reduce the size of the unique word and improve the throughput characteristics.

  An object of the present invention is to provide a unique word detection apparatus and method for solving such drawbacks of the prior art, improving throughput characteristics in wireless communication, and improving unique word detection characteristics.

  In order to solve the above-described problems, the present invention provides a unique word detection device mounted on a communication terminal such as an on-vehicle device or a roadside device that transmits and receives packets in a wireless communication system such as inter-vehicle communication. The first unique word is used as the first unique word, the pattern including a part of the first unique word is used as the second unique word, and the first unique word is detected based on the received packet. 1 original detection means, a second detection means for detecting a second unique word based on the received packet, and whether or not the original unique word could be detected according to the detection results of the first and second detection means And unique word detection determination means for determining whether or not.

  In addition, a unique word detection device mounted on a communication terminal such as a vehicle-mounted device or a roadside device that transmits and receives a packet in a wireless communication system such as inter-vehicle communication uses the original unique word and a part of the preamble of the packet. This pattern is used as the third unique word, and when the third unique word is detected based on the received packet, it is determined that the original unique word has been detected.

  Furthermore, in a wireless communication system such as inter-vehicle communication, a unique word detection method for detecting a unique word from a packet transmitted / received by a communication terminal such as an on-vehicle device or a roadside device has a pattern including the original unique word in the packet. A first detection step for detecting a first unique word based on a received packet, using the first unique word, a pattern comprising a part of the first unique word as a second unique word, and reception A second detection step for detecting a second unique word based on the received packet, and a unique word detection for determining whether or not the original unique word has been detected according to the detection results of the first and second detection steps And a determination step.

  A unique word detection method for detecting a unique word from a packet transmitted and received by a communication terminal such as an on-vehicle device or a roadside device in a wireless communication system such as inter-vehicle communication is one of the original unique word and preamble. A pattern consisting of a part is used as a third unique word, and when the third unique word is detected based on the received packet, it is determined that the original unique word has been detected.

  According to the unique word detection device of the present invention, the pattern including the original unique word is used as the first unique word, and the pattern including a part of the first unique word is used as the second unique word. The unique word detection characteristic can be improved by performing the original unique word detection determination based on the detection of the second unique word.

  Here, the number of allowable bit errors at the time of detecting the first unique word is increased to reduce the unique word non-detection rate, while the number of allowable bit errors at the time of detecting the second unique word is decreased to reduce the unique word error. The detection rate can be suppressed.

  The unique word detection device of the present invention detects the size of the original unique word by detecting, based on the received packet, another unique word including a part of the preamble and the original unique word in the received packet. Even if it is reduced, the throughput characteristic in wireless communication is improved.

  Embodiments of a unique word detecting device according to the present invention will now be described in detail with reference to the accompanying drawings. For example, as shown in FIG. 1, the unique word detection device 10 includes a first unique word detection unit 12 that detects a predetermined first unique word from a received packet, and a part of the first unique word. And a second unique word detection unit 14 for detecting a second unique word, and the unique word detection determination unit 16 determines whether the unique word has been detected from the received packet according to the detection results. It is. Note that portions not directly related to understanding the present invention are not shown and redundant description is avoided.

  The device 10 is mounted on a communication terminal such as an in-vehicle device or a roadside device that transmits and receives packets in a system that performs wireless communication, particularly inter-vehicle communication. Such a communication terminal establishes synchronization in packet communication by detecting a unique word in the received packet using the apparatus 10.

  The packet 112 used in this wireless communication system has various fields such as a control field and a data field (payload). In particular, as shown in FIG. Next, an area for writing the unique word 116 is provided. Note that the patterns of the preamble 114 and the unique word 116 may be known by all communication terminals.

  In the present embodiment, a pattern including not only the unique word 116 but also a part of the preamble 114 in the packet 112 is defined as a first unique word 118, and a pattern including a part of the first unique word 118 is defined as a second pattern. Use as unique word 120.

  In this embodiment, the packet 112 is a series of a plurality of bit data, and the sizes of the first and second unique words 118 and 120 are a and b bits, respectively, and a and b are integers of 1 or more. , A is larger than b.

  The apparatus 10 receives a packet 112 received by a communication device, and detects first and second unique words using the bit data of a and b bits of the received packet 112 as received information 102 and 104. Input to parts 12 and 14, respectively. That is, the first bits of the reception information 102 and 104 are shifted by a−b bits. For example, when the x-th bit data of the reception packet 112 is d (x), the bit data of the reception information 102 is Are arranged in the order of d (1), d (2),..., D (a-1), d (a), the bit data of the reception information 104 is d ( a-b + 1), d (a-b + 2),..., d (a-1), d (a).

  The apparatus 10 of the present embodiment may, for example, sequentially obtain each bit data from the received packet 112 for each bit, and generate the reception information 102 and 104 for a and b bits by the FIFO method. The first and second unique word detectors 12 and 14 may sequentially input the bit data of the received packet 112 and the bit data for a and b bits may be used as the received information 102 and 104, respectively.

  In addition, the apparatus 10 may demodulate the reception packet 112 input from the communication device, or input the reception packet 112 that has already been demodulated from the communication device, and generate reception information 102 and 104 based on the demodulated signal. .

  The first unique word detecting unit 12 compares and determines the a-bit received information 102 based on the received packet 112 with the first unique word 118, and sends the comparison information 106 based on the result to the unique word detecting and determining unit 16. To supply.

  The detection unit 12 of this embodiment holds the pattern of the first unique word 118 in advance, compares this pattern with the pattern of the reception information 102, and determines whether or not they match for each bit. Get the number of bits that do not match. Further, the detection unit 12 holds the allowable bit error number Na in advance, compares the number of mismatched bits of the determination result with the allowable bit error number Na, and indicates the first unique word non-detection when larger than Na, When Na or less, comparison information 106 indicating the first unique word detection is generated.

  Similarly to the detection unit 12, the second unique word detection unit 14 compares and determines the b-bit reception information 104 based on the reception packet 112 with the second unique word 120, and compares the comparison information 108 based on the result. Is supplied to the unique word detection determination unit 16.

  The detection unit 14 of this embodiment compares the pattern of the second unique word 120 held in advance with the pattern of the received information 104, determines whether or not they match for each bit, and determines the number of bits that do not match. obtain. Further, the detection unit 14 compares the number of mismatched bits of the determination result with the number Nb of allowable bit errors stored in advance, and indicates a second unique word non-detection when it is larger than Nb, and when it is equal to or smaller than Nb. Comparison information 108 indicating the detection of two unique words is generated.

  The unique word detection determination unit 16 determines whether a unique word has been detected from the received packet 112 according to the comparison information 106 and 108 by the detection units 12 and 14, and outputs the detection detection information 110 as a result It is.

  The detection determination unit 16 of the present embodiment generates detection determination information 110 indicating unique word detection only when the comparison information 106 indicates first unique word detection and the comparison information 108 indicates second unique word detection. If the combination of the comparison information 106 and 108 is other than this, the detection determination information 110 indicating the unique word non-detection is generated.

  Next, an example of the reception operation of the unique word detection device 10 in the present embodiment will be described with reference to the flowcharts of FIGS.

  In this embodiment, first, when a packet 112 is received by a communication terminal to which the present apparatus 10 is applied, a unique word detection operation by the present apparatus 10 is started (S202).

  In this apparatus 10, data is obtained for each bit from the head of the demodulated signal of this packet 112 based on the received packet 112, and bit data for a and b bits is obtained as received information 102 and 104 by the FIFO method. It is done.

  In this embodiment, the reception information 102 and 104 is data based on the k-th bit of the demodulated signal of the reception packet 112. For example, when the xth bit data of the demodulated signal is d (x), the reception information 102 is the bit data d (k), d (k + 1), d (k + 2) starting with the kth bit. ),..., D (k + a-1), and the received information 104 is bit data d (k + ab), d (k + a-b + 1) starting from the k + a−b-th bit. , D (k + a−b + 2),..., D (k + a−1).

  When the unique word detection operation starts in step S202, 1 is set as the initial value of the number k (S204).

  Next, in the present apparatus 10, the first and second unique word detection processing (SUB1, SUB2) in each of the detection units 12 and 14 is performed.

  In the subroutine SUB1, the detection unit 12 operates as shown in the flowchart of FIG. 4 to perform the first unique word detection process.

  First, the detection unit 12 obtains a-bit reception information 102 starting from the k-th bit of the demodulated signal of the received packet 112 (S222). Here, since k is 1, the first bit is first. Received information 102 comprising the bit data d (1), d (2), d (3),..., D (a) is obtained.

  Next, the detection unit 12 compares the reception information 102 starting with the first bit with the first unique word 118 (S224), and compares the data of each bit in order from the first bit of both, and matches. It is determined whether or not.

  As a result of the determination by the detection unit 12, the number of mismatch bits is obtained and compared with the allowable number of bit errors Na (S226).

  For example, the reception information 102 starting with the first bit corresponds to the first unique word 118 only when the first unique word starts from the beginning of the preamble 114. At this time, the number of mismatch bits obtained in step S224 is usually small, but the number of mismatch bits may be large if the communication environment at the time of packet reception is bad. If the received information 102 does not correspond to the first unique word 118, the number of mismatch bits will naturally be large.

  In step S226, if the number of mismatch bits is Na or less, the process proceeds to step S228, and if it is greater than Na, the process proceeds to step S230.

  In step S228, comparison information 106 indicating first unique word detection is generated, and in step S230, comparison information 106 indicating first unique word non-detection is generated.

  In this way, the detection unit 12 obtains detection or non-detection of the first unique word, and the first unique word detection process (SUB1) is completed.

  Similarly, in the subroutine SUB2, the detection unit 14 operates as shown in the flowchart of FIG. 5 to perform the second unique word detection process.

  First, the detection unit 14 obtains b-bit reception information 104 starting from the k + a−b-th bit of the demodulated signal of the reception packet 112 (S242). Here, since k is 1, 1 + a−b bits Reception information 104 including bit data d (1 + ab), d (2 + ab), d (3 + ab),..., D (a) starting from the eye is obtained.

  Next, the detection unit 14 compares the received information 104 with the 1 + a−b bit at the head as compared with the second unique word 120 (S244), and sequentially compares the data of each bit from the head bit of both, It is determined whether or not they match.

  As a result of the determination by the detection unit 14, the number of mismatch bits is obtained and compared with the allowable number of bit errors Nb (S246).

  For example, the reception information 104 starting from the 1 + a−b bit corresponds to the second unique word 120 only when the first unique word starts from the beginning of the preamble 114. At this time, the number of mismatch bits obtained in step S244 is usually small, but the number of mismatch bits may be large if the communication environment during packet reception is bad. If the received information 104 does not correspond to the second unique word 120, the number of mismatch bits will naturally be large.

  In step S246, if the number of mismatch bits is equal to or less than Nb, the process proceeds to step S248, and if greater than Nb, the process proceeds to step S250.

  In step S248, comparison information 108 indicating second unique word detection is generated, and in step S250, comparison information 108 indicating second unique word non-detection is generated.

  In this way, the detection unit 14 obtains the detection or non-detection of the second unique word, and the second unique word detection process (SUB2) ends.

  When the detection processing of SUB1 and SUB2 is completed, the apparatus 10 of the present embodiment proceeds to step S206 as shown in FIG. 3 and compares according to the detection result by SUB1 and SUB2, that is, the comparison obtained from the detection units 12 and 14. Whether or not a unique word has been detected from the received packet 112 is determined according to the information 106 and 108.

  In step S206, when the unique word detection determination unit 16 determines the comparison information 106 and 108, the comparison information 106 indicates the first unique word detection, and the comparison information 108 indicates the second unique word detection. Proceed to step S208, otherwise proceed to step S210.

  In step S208, the detection determination unit 16 generates and outputs detection determination information 110 indicating unique word detection, and the unique word detection operation ends (S212).

  In step S210, the detection determination unit 16 generates and outputs detection determination information 110 indicating that the unique word is not detected, and the process proceeds to step S214.

  In step S214, the received information 102 and 104 are shifted by 1 bit, and the first and second unique word detection processing (SUB1, SUB2) proceeds. Here, 1 is added to the number k, and the subroutines SUB1 and SUB2 are added. move on.

  As described above, in the case where the unique word is not detected, the first and second unique word detection processing (SUB1, SUB2) is performed on the reception information 102 and 104 starting with the next bit, and the unique word is detected. The detection process is repeated until.

  Although not shown here, when the unique word detection process is interrupted, for example, when packet reception is interrupted, it is preferable to exit from the repetition of this detection process.

  Further, the unique word detection device 10 of the present invention may be configured not only to improve both the unique word detection characteristic and the throughput characteristic, but also to improve only the unique word detection characteristic or only the throughput characteristic.

  When the unique word detection device 10 improves only the unique word detection characteristic, for example, a pattern including only the original unique word 116 is defined as a first unique word 118, and a pattern including a part of the first unique word 118 is used. Is used as the second unique word 120.

  Further, when the unique word detecting device 10 improves only the throughput characteristic, for example, the first unique word 118 is defined as a pattern including the original unique word 116 and a part of the preamble 114 as the first unique word 118. Can be realized without detecting the second unique word 120.

  Furthermore, the unique word detection device 10 uses a pattern composed of the original unique word 116 and a part of the preamble 114 as the first unique word 118, and the second composed of a part of the first unique word 118. As the unique word 120, a pattern including not only the original unique word 116 but also a part of the preamble 114 can be used as the second unique word 120.

It is a block diagram which shows one Example of the unique word detection apparatus based on this invention. It is a figure which shows roughly the packet and unique word which the unique word detection apparatus of the Example shown in FIG. 1 uses. It is a flowchart explaining the operation | movement procedure in the unique word detection apparatus of the Example shown in FIG. FIG. 4 is a flowchart illustrating a first unique word detection process in a subroutine SUB1 in the operation procedure of FIG. 3. FIG. 4 is a flowchart illustrating a second unique word detection process in subroutine SUB2 in the operation procedure of FIG.

Explanation of symbols

10 Unique word detector
12 First unique word detector
14 Second unique word detector
16 Unique word detection judgment part

Claims (10)

In a unique word detection device mounted on a communication terminal such as an on-vehicle device or a roadside device that transmits and receives packets in a wireless communication system such as inter-vehicle communication, the device includes:
Among the packets, a pattern including an original unique word is used as a first unique word, and a pattern including a part of the first unique word is used as a second unique word.
First detecting means for detecting a first unique word based on the received packet;
Second detection means for detecting a second unique word based on the received packet;
A unique word detection device comprising: unique word detection determination means for determining whether or not an original unique word has been detected according to detection results by the first and second detection means.   2. The unique word detection device according to claim 1, wherein the unique word detection determination means detects a first unique word by a first detection means and detects a second unique word by a second detection means. A unique word detection device that determines that an original unique word has been detected only when   2. The unique word detecting device according to claim 1, wherein the device uses a pattern including an original unique word and a part of a preamble as the first unique word in the packet. Detection device.   2. The unique word detection device according to claim 1, wherein the device is a pattern composed of a part of a first unique word in the packet, and a pattern composed of an original unique word and a part of a preamble. A unique word detecting device used as a second unique word. In a unique word detection device mounted on a communication terminal such as an on-vehicle device or a roadside device that transmits and receives packets in a wireless communication system such as inter-vehicle communication, the device includes:
Of the packet, a pattern consisting of an original unique word and a part of a preamble is used as a third unique word,
An apparatus for detecting a unique word, characterized in that an original unique word can be detected when a third unique word is detected based on a received packet. In a unique word detection method for detecting a unique word from a packet transmitted and received by a communication terminal such as a vehicle-mounted device or a roadside device in a wireless communication system such as inter-vehicle communication, the method includes:
Among the packets, a pattern including an original unique word is used as a first unique word, and a pattern including a part of the first unique word is used as a second unique word.
A first detection step of detecting a first unique word based on the received packet;
A second detection step of detecting a second unique word based on the received packet;
A unique word detection method comprising: a unique word detection determination step of determining whether or not an original unique word has been detected according to detection results of the first and second detection steps.   7. The unique word detection method according to claim 6, wherein in the unique word detection determination step, a first unique word is detected in the first detection step, and a second unique word is detected in the second detection step. A unique word detection method, wherein it is determined that an original unique word has been detected only when   7. The unique word detection method according to claim 6, wherein the method uses a pattern composed of an original unique word and a part of a preamble as the first unique word in the packet. Detection method.   The unique word detection method according to claim 6, wherein the method is a pattern composed of a part of a first unique word in the packet, and a pattern composed of an original unique word and a part of a preamble. A unique word detection method, wherein the unique word detection method is used as a second unique word. In a unique word detection method for detecting a unique word from a packet transmitted and received by a communication terminal such as a vehicle-mounted device or a roadside device in a wireless communication system such as inter-vehicle communication, the method includes:
Of the packet, a pattern consisting of an original unique word and a part of a preamble is used as a third unique word,
A unique word detection method, comprising: determining that an original unique word has been detected when a third unique word is detected based on a received packet.

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