GB2527654A - Spot transmission communication device and time correction method thereof - Google Patents
Spot transmission communication device and time correction method thereof Download PDFInfo
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- GB2527654A GB2527654A GB1507327.3A GB201507327A GB2527654A GB 2527654 A GB2527654 A GB 2527654A GB 201507327 A GB201507327 A GB 201507327A GB 2527654 A GB2527654 A GB 2527654A
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- mobile body
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- 238000004891 communication Methods 0.000 title claims abstract description 198
- 230000005540 biological transmission Effects 0.000 title claims description 27
- 238000000034 method Methods 0.000 title claims description 13
- 238000012937 correction Methods 0.000 title abstract description 14
- 238000001514 detection method Methods 0.000 claims abstract description 42
- 230000005856 abnormality Effects 0.000 claims description 8
- 238000012545 processing Methods 0.000 claims description 4
- 230000001360 synchronised effect Effects 0.000 description 9
- 235000014676 Phragmites communis Nutrition 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1803—Stop-and-wait protocols
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B61—RAILWAYS
- B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
- B61L3/00—Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal
- B61L3/02—Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control simultaneous mechanical and electrical control
- B61L3/08—Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control simultaneous mechanical and electrical control controlling electrically
- B61L3/12—Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control simultaneous mechanical and electrical control controlling electrically using magnetic or electrostatic induction; using radio waves
- B61L3/125—Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control simultaneous mechanical and electrical control controlling electrically using magnetic or electrostatic induction; using radio waves using short-range radio transmission
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/0008—Synchronisation information channels, e.g. clock distribution lines
- H04L7/0012—Synchronisation information channels, e.g. clock distribution lines by comparing receiver clock with transmitter clock
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/0016—Arrangements for synchronising receiver with transmitter correction of synchronization errors
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mechanical Engineering (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
- Mobile Radio Communication Systems (AREA)
- Electric Clocks (AREA)
Abstract
A communication device 1-7 on a mobile body (vehicle) determines a detection time of a trackside communication device 1-16 on the basis of system time information included in messages received from a mobile body control portion 1-2. However, if the control portion has to perform message retransmission due to a communication error, divergence occurs between the time included in the retransmitted message and the actual time, leading to an error in timing (see figure 5). To detect divergence caused by retransmission, the communication device calculates the difference in system times received in current and previous messages, and compares this with the difference in local timer values recorded when the messages were received. If the result exceeds a threshold then it is determined that an out-of-synchronisation situation has occurred due to retransmission, and a correction is performed. Consequently detection time of the trackside communication device is calculated with high accuracy.
Description
SPOT TRANSMISSION COMMUNICATION DEVICE AND TIME CORRECTION
METHOD THEREOF
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a spot transmission communication device and a time correction method thereof.
Description of the Related Art
As background art in this technical field, Japanese Patent Laid-Open Publication No. 2011-29756 (Patent Document 1) can be cited.
This Publication describes that, with respect to current time information transmitted regularly at a predetermined interval which is to be a basis, a receiving terminal side makes correction for hardware interruption in accordance with progress of time of the current time information and thus, time progress can be made close to equal to progress of time indicated by the current time information transmitted regularly at the predetermined interval.
A mobile body communication device calculates detection time of a trackside communication device on the basis of time information obtained from a mobile body control portion which is its superior device. In order to calculate the detection time of the trackside communication device with high accuracy, it is important that time of the mobile body communication device and time of the mobile body control portion are synchronized with each other.
In prior-art time synchronization between each apparatus, clock correction or the like is performed on the basis of a signal from a synchronization source apparatus as the technology described in Patent Document 1, and the time information of the signal of the synchronization source is trusted and considered to be without an error. However, re-transmission of a message signal or the like occurs when a communication failure or the like occurs, and in such a case, an error can occur in the time information of the synchronization signal.
Thus, the present invention provides a spot transmission communication device which corrects an error which is likely to be included in the time information of the synchronization signal.
SUMMARY OF THE INVENTION
In order to solve the above-described problem, the present invention has, in the mobile body communication device: a current time storage portion for storing both system time added to a latest message received from the mobile body control portion which is a superior device and a self timer value when the message is received; a past time storage portion for storing, when a message has been received prior to the latest message, both the system time of the previous message and the self timer value when the previous message was received; and a time synchronization portion which detects occurrence of a communication failure from the two types of time information, that is, the system time and the self timer value, and corrects an error of a synchronization signal.
According to the present invention, when a communication failure or the like occurs between the mobile body control portion and the mobile body communication device, such failure is detected, and the synchronization time can be corrected and kept accurate.
Problems, configurations and advantageous effects other than the above will be made apparent from description of the following embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an entire configuration diagram of an embodiment of the present invention; FIG. 2 is an explanatory view when the present invention is applied to speed control of a mobile body; FIG. 3 is a flowchart of timer value setting for synchronization; FIG. 4 is an explanatory view of accuracy in synchronization between a mobile body control portion and a mobile body communication device (no re-transmission); FIG. 5 is an explanatory view of accuracy in synchronization between the mobile body control portion and the mobile body communication device (re-transmission other than initial communication); FIG. 6 is an explanatory view of accuracy in synchronization between the mobile body control portion and the mobile body communication device (re-transmission in initial communication); FIG. 7 is a flowchart of the timer value setting for synchronization with error detection applied; and FIG. 8 is an explanatory view of trackside communication device detection.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(Embodiment 1) First, an entire configuration of an embodiment will be described below by using FIG. 1.
FIG. 1 illustrates entire configurations of a spot transmission communication device installed on a mobile body and a trackside communication device.
In a communication device transmitting/receiving control information used for control of a mobile body (1-1) between a trackside and the mobile body, a trackside communication device (1-16) installed on the ground performs wireless power feed by an electric power wave from a mobile body communication device (1-7) installed on the mobile body and conducts information transmission from the trackside communication device to the mobile body communication device by using this power through electromagnetic coupling using a frequency different from the electric power wave.
Specifically, in order to transmit road surface information such as inclination gradient or the like to the mobile device, the road surface information is set in the trackside communication device (1-16).
The mobile body communication device (1-7) uses signal intensity received from the trackside communication device in order to determine entry and advance into a communication range of the trackside communication device (1-16) (hereinafter referred to as trackside communication device detection). That is, when a mobile antenna (1-13) passes the trackside communication device (1-16), the trackside communication device (1-16) transmits a message of the information by the electromagnetic coupling to the mobile body communication device (1-7).
At this time, the signal intensity received by the mobile body communication device is maximized when electric center positions of the mobile body communication device and the trackside communication device match each other and decreases when they go apart from each other.
Thus, by setting an appropriate detection threshold value of 1 value or more, it can be determined that the trackside communication device has been detected when the received signal intensity exceeds the detection threshold value (see FIG. 8).
On the other hand, a spot transmission communication device installed on the mobile body is constituted by the mobile body communication device (1-7) and a mobile body control portion (1-2) which is its superior device. The mobile body communication device calculates detection time of the trackside communication device which made detection on the basis of mobile body speed information and time information from the mobile body control portion and reports it with the message received from the trackside communication device to the mobile body control portion.
Subsequently, an outline of the problem to be solved by the present invention will be described.
The mobile body communication device (1-7) has a self timer (1-1 0) in its inside but basically calculates the detection time of the trackside communication device on the basis of the time information also from the mobile body control portion (1-2) which is a superior device. Thus, in order to calculate the time of the trackside communication device with high accuracy, it is important that time of the mobile body communication device (1-7) and time of the mobile body control portion (1-2) are synchronized with each other.
In spot transmission whose communication cover area is local, the mobile body communication device needs to calculate time within an error of a position of the trackside communication device at approximately 1 [m], in general. Since, during high-speed movement, time required for advance of 1 [ml at 500 [km/h], for example, is only 7.2 [ms], a difference in time recognized by the mobile body control portion and by the mobile body communication device, respectively, needs to be the above-described value or less.
As described above, prior-art time synchronization between apparatuses is made on the basis of a signal from a synchronization source apparatus, and though clock correction or the like is made, occurrence of an error in the synchronization signal itself is not considered.
However, whether it is wired or wireless, a communication error can occur in communication due to an external or internal factor, and it is impossible to completely suppress the communication error. For example, a communication error can occur due to occurrence of a communication failure or the like in a communication path (1- 6) between the mobile body control portion and the mobile body communication device.
With regard to such phenomena, communication redundancy, that is, detection or correction of an error can be made by correcting an error by a reed solomon code in a communication message or by detecting an error of a message by error detecting means such as a CRC code and then, by re-transmitting the message by using re-transmission control or the like.
However, if an error correction code is used, a large quantity of calculation time is required for encoding/decoding, and if communication redundancy is ensured by the error correction by the reed solomon code or the error detecting means such as the CRC code, an error occurs between the mobile body control portion and the mobile body communication device and as a result, there is a concern that accuracy of the detection time of the trackside communication device is deteriorated to the contrary. That is, these methods cannot handle processing requiring real time properties such as spot transmission in many cases.
Moreover, if the re-transmission control is executed, the time information in the re-transmitted message is still what it was and there is a problem that the time in the message is delayed from actual time by time required for re-transmission.
The present invention was made in view of the above-described points and includes a system time management portion (1-5), a communication portion (1-3) with the mobile body communication device, and a re-transmission control portion (1- 4) of the communication in the mobile body control portion (1-2), and in the mobile body communication device, includes a trackside communication device detection portion (1-12) for determining detection of the trackside communication device by measuring signal intensity received from the trackside communication device, a communication portion (1-B) which receives system time when management is performed in the mobile body control portion and transmits reception information of the trackside communication device, a re-transmission control portion (1-9) in which, when a failure occurs in communication with the mobile body control portion, it is reported to the mobile body control portion and re-transmission is prompted, and a self timer (1-10) for counting time in the mobile body communication device.
Then, from the two kinds of time information, that is, the self timer value and the system time received from the mobile body control portion, a timer value for synchronization to be a basis of the trackside communication device detection time is calculated, and on the basis of the three kinds of time information, that is, the self timer value, the system time, and the timer value for synchronization, communication redundancy with the mobile body communication portion is ensured and the detection time of the trackside communication device is calculated with high accuracy by performing the following operations (a), (b), and (c): (a) The mobile body communication device stores the system time received from the mobile body control portion, the self timer value at communication reception, and the timer value for synchronization each time communication is conducted and manages them.
(b) An increase of the system time included in communication messages at previous communication and current communication (when the latest message is received) and an increase of the self timer value at the previous communication and the current communication (when the latest message is received) are compared, and the timer value for synchronization is set as follows: If no error occurs in the increases of the both, it is determined that a communication failure such as re-transmission or the like has not occurred in communication, and the self timer value at message reception is set to a timer value for synchronization.
If an error occurs in the increase of the both, it is determined that a communication failure such as re-transmission or the like has occurred in communication, and the self timer value at message reception is not employed as the timer value for synchronization, and a value obtained by adding the increase in the system time included in the communication message from the mobile body control portion to the timer value for the previous synchronization is set to the timer value for synchronization.
(c) If the mobile body communication device detects the trackside communication device, it measures elapsed time to detection from the timer value for synchronization set in the above-described (a) and (b) by the self timer. Then, this elapsed time measured by the self timer is added to the system time stored at the same time as the timer for synchronization used as a reference and set to the trackside communication device detection time.
The above-described points will be described by referring to FIG. 1 for each of the operations.
When the mobile body communication device (1-7) conducts communication with the trackside communication device (1-16), it transmits the received time of the message to the mobile body control portion (1-2) with the message.
Subsequently, the mobile body control portion (1-2) uses the communication portion (1-3) and transmits the system time to the mobile body communication device (1-7) through a transmission path (1-6). Moreover, the communication is subjected to re-transmission control by the re-transmission control portions (1-4) and (1-9) in order to ensure redundancy.
The re-transmission control uses a Stop-and-wait ARQ method or the like, for example. In the Stop-and-wait ARO method, means capable of examining errors such as a CRC is incorporated in a message, and when the message is received on a receiving side, if the message does not have an error, positive acknowledgement (ACK) is replied, while if it has an error, negative acknowledgement (NACK) is replied.
A transmitting side considers the communication to be successful if it receives the positive acknowledgement (ACK) after transmission of the message and if it receives the negative acknowledgement (NACK), it considers the communication to be failed and transmits the message again (re-transmission).
Moreover, the transmitting side counts time from the transmission and if it cannot receive either of the positive acknowledgement (ACK) and the negative acknowledgement (NACK) by certain time, it considers the message transmission to be failed and re-transmits the message. An upper limit in the number of re-transmission times to one message is determined in view of an environment of a communication path so that, if a transmission apparatus or a receiving apparatus fails, re-transmission is not to be conducted permanently.
In a case of wired communication as in this embodiment, the upper limit of the number of re-transmission times is once in general, and if the transmitting side receives a second timeout or NACK, it determines to be a failure and stops the system.
Moreover, the communication portion (1-3) of the mobile body control portion (1-2) also performs a reception work of a message from the mobile body communication device (1-7), and the re-transmission control similar to the above is executed also for this communication by the re-transmission control portions (1-4) and (1-9).
Subsequently, the mobile body communication device (1-7) will be described.
In Fig. 1, the mobile body communication device (1-7) includes the trackside communication device detection portion (1-12), the communication portion (1-8) with the mobile body control portion, the re-transmission control portion (1-9), a time synchronization portion (1-15), and the self timer (1-10) for counting time on the basis also of a hardware clock.
When the mobile body communication device (1-7) detects the trackside communication device (1-16) by the trackside communication device detection portion (1-12), it calculates the detection time and transmits it to the mobile body control portion (1-2) through the communication path (1-6) by using the communication portion (1-8) together with the message from the trackside communication device (1-16). A method of the trackside communication device detection is to measure reception intensity from the trackside communication device and to make determination on the basis of the intensity.
At this time, since the detection time of the trackside communication device is used for control in the mobile body control portion (1-2), it needs to be synchronized with the system time of the mobile body control portion (1-2). Thus, the mobile body communication device (1-7) needs to cause the system time received from the mobile body control portion (1-2)to correspond to the self timer (1-10) in the time synchronization portion (1-11) at reception of the system time from the mobile body control portion (1-2).
Regarding this, a determination method of the timer value for synchronization will be described by a flowchart using FIG. 3.
First, in FIG. 3, at Step (3-1), the mobile body communication device (1-7) receives a message including the system time (Tc. N) from the mobile body control portion (1-2).
A first suffix C in Tc. N represents the system time, while a second suffix N represents the N-th system time reception from the mobile body control portion (1-2), and transmission timing of the message from the mobile body control portion (1-2) may be or may not be a regular constant interval.
If the mobile body communication device (1-7) receives the system time from the mobile body control portion, the received system time Tc, N and the self timer value (TR. N) at the message reception are stored in a set in a current time storage portion (1-14).
A first suffix R in TR, N represents the self timer value managed by the mobile body communication device (1-7), while a second suffix N represents the N-th system time reception.
If the mobile body communication device has received the system time prior to that, the information received previously and stored in the current time storage portion (1-14) is moved to a past time recording portion (1-15).
At Step (3-2), whether or not it is a first system time reception from the mobile body control portion (1-2) is determined, and if it is the first reception (that is, in a case of Tc, o reception), the received Tc, N is set to the timer value for synchronization (TG. N) (that is, To, o = TR, o) at Step (3-3) and recorded in the current time storage portion (1-14) in a set with the system time and the self timer value.
The timer value for synchronization is an expected self timer value when the received system time (Tc. N) is created, and a first suffix G in To. N represents the timer value for synchronization managed by the mobile body communication device (1-7), while a second suffix N represents the N-th system time reception.
In a case other than the first reception at Step (3-2), a difference (ATc, N) between the system time (Tc. N) received this time and the system time (Tc. N-i) received previous time stored in the current time storage portion (1-14) and the past time storage portion (1-15) is calculated at Step (3-4).
At Step (3-5), a difference (AIR, N) between the self timer value (IR, N) received this time and the self timer value (TR, N-i) received previous time stored in the current time storage portion (1-14) and the past time storage portion (1-15) is calculated.
At Step (3-6), a difference value between ATc. N calculated at Step (3-4) and AIR, N calculated at Step (3-5) is compared with a specified value 1 as a threshold value and determined whether or not out-of-synchronization has been caused by re-transmission.
Specifically, the timer value for synchronization (TG. N) is determined as follows and recorded in the current time storage portion (1-14) in a set with the system time and the self timer value.
In a case of ATc. N -ATR, N < specified value 1, it is considered that no delay has been caused by re-transmission and it is set to Ta N = IR. N and stored at Step (3-7).
In a case of ATc. N -ATR, N »= specified value 1, it is considered that a re-transmitted message has been received and it is set to IG. N = Ta N-i + ATc. N and stored at Step (3-8).
At this time, a method of determining the specified value 1 depends on calculated position accuracy of the trackside communication device. Assuming that a position allowable error is L [ml and a use maximum speed is V [mis], it is approximately the specified value I as a threshold value LIV [s].
If a difference between Tc. N and IR, N is compared with a difference between Tc, Ni and IR, Ni instead of comparison of the differences ATc. N and ATR. N, it is: AIc, N -ATR. N = (Ic, N -Ic, N-i) -[FR, N -IR, N-i) = (Tc. N -TR. N) -(Tc, N-i -TR, N-i) and thus, it is mathematically equivalent, and equivalent calculation can be made.
Subsequently, by using time charts in FIGs. 4 to 6, how the mobile body control portion is synchronized with the mobile body communication device by presence of re-transmission when the present invention is applied will be described in terms of a relation among Tc. N, Ts. N, and IG. N. FIG. 4 is a time chart when re-transmission has not occurred, and in the determination at Step (3-6) in FIG. 3, all the communication branches to Step (3-7) side, the system time is synchronized with the internal timer, and the trackside communication device detection time can be calculated without problem.
In FIG. 5, re-transmission occurred in the second communication in which Tc, i was transmitted. In this case, in the second communication, the difference AIR, N of the internal timer becomes larger than the difference ATc, N of the system time only by re-transmission delay Ta Thus, in the determination at Step (3-6) in Fig. 3, it branches to the Step (3-8) side and is subjected to correction.
Moreover, in the third communication, on the contrary, the difference AIR, N of the internal timer becomes smaller than the difference ATc, N of the system time only by re-transmission delay To, in the determination at Step 3-6 in FIG. 3, it branches to the Step (3-8) side similarly to the previous time and is subjected to correction, and the system time is synchronized with the internal timer substantially accurately.
In the fourth communication and after, correction is not made, and the system time is accurately synchronized with the internal timer.
In FIG. 6, re-transmission occurs in the initial communication in which Tc, o is transmitted. In this case, since there is no comparison target in the first reception, an error occurs and the error continues to the second reception but synchronization can be realized at the third reception. Such an event occurs only in the first communication and thus, the risk can be avoided in the first communication by transmitting the system time from the mobile body control portion in a span shorter than usual and the like.
By executing such processing, even if re-transmission occurs due to occurrence of a communication failure or the like, the system time can be synchronized with the internal timer with high accuracy, and the detection time of the trackside communication device can be calculated.
In order to perform the trackside communication device detection more accurately, a transmission loss of the communication may be pulled in from IR, N when TG. N = TR. N is set at Steps (3-3), (3-7), and (3-8).
The information relating to the trackside communication device received from the mobile body communication device is used for executing speed control or the like by adding a speed control portion (2-17) to the mobile body control portion (2-2) as illustrated in FIG. 2 and by combining it with speed information obtained from a car speed detection portion (2-20) such as a speed generator and a GPS in the speed control portion (2-17) so as to control a driving device (2-18) and a brake device (2-19).
FIG. 8 illustrates a relational view between reception intensity received by the mobile body communication device and passage time in passage of the trackside communication device. A method in which a point where the reception intensity from the trackside communication device (1-16) exceeds a detection threshold value (8-1) is set to an entry point (8-2), a point where it falls below the detection threshold value (8-1) to an entry point (8-3), and an intermediate point between the both to a detection point (8-4), or a method in which a maximum point of the reception intensity expected to be immediately above the center of the trackside communication device is set to a detection point (8-5) is considered.
If TG. N set as above is used, by measuring time from this TG. N to detection of the trackside communication device (1-1 6) at all times based on an arbitrary TG,N by the self timer and by adding the elapsed time by the self timer which has been measured to Ic which is the system time stored at the same time as To. N set to the basis at the detection, even if re-transmission occurs, the trackside communication -10-detection time synchronized with the mobile body control portion can be calculated with high accuracy.
According to the present invention, while redundancy by the re-transmission control is ensured for the communication between the mobile body control portion and the mobile body communication device, even if re-transmission occurs in the communication, an error in time recognized by each of the mobile body control portion and the mobile body communication device can be suppressed, and the mobile body communication device capable of calculating the detection time of the trackside communication device can be realized with high accuracy.
(Embodiment 2) In this embodiment, a variation of the embodiment 1 illustrated in FIG. 3 will be described.
Specifically, in case of occurrence of abnormality in the system time itself caused by clock abnormality in the mobile body control portion (1-2) in FIG. 1, a new step is provided after Step (3-4) in FIG. 3.
Specifically, as illustrated at Step 7-9 in FIG. 7, ATc, N is compared with a specified value 2 as a new threshold value so as to conduct an inspection of the clock abnormality.
Here, regarding how to determine the specified value 2, since there is a concern that Aic, N might be delayed from a forecast value depending on a load state of the mobile body control portion (1-2), it can be set to the specified value 2 = forecast value ± d assuming that fluctuation time of processing time by a maximum/minimum load state is d.
At this time, d needs to be set smaller than the fluctuation time by an assumed failure mode. For example, when time is calculated on the basis of a clock generated by a crystal oscillator, if the failure mode of the crystal oscillator forecasts that a frequency of the clock is reduced to a half or less, the forecast value d may be set to approximately a twice or less of a communication time interval.
When ATc: N is to be compared with the specified value 2, since it is necessary to know a transmission interval of the system time to some degree, the transmission timing of the system time is preferably a regular constant interval.
Moreover, in order to conduct an inspection so as to check abnormality in the self timer such as clock abnormality of the mobile body communication device (1-7), monitoring may be conducted such that a new branch may be further added to the branch in Step (3-6) in FIG. 3 so that increases in the respective system time and the respective self timer values at message reception are compared between the latest message and the previous message, and if the compared value is larger than the maximum delay time by re-transmission, it is determined that abnormality occurs in the self timer (Step 7-6 in FIG. 7).
The present invention is not limited to the above-described embodiments but includes various variations. Moreover, it is possible to replace a part of the -11 -configuration of one embodiment with the configuration of another embodiment.
Furthermore, the above-described embodiments are described in order to explain the present invention to be easily understood, and the present invention is not necessarily limited to those provided with all the described configurations.
For example, the method and allowable margin of setting the specified value can be appropriately changed in accordance with the use environment of the communication device, the characteristics of the mobile body and the like, and it is natural that the configurations of the mobile body communication device and the trackside communication device can include various variations according to the type, size and the like of the mobile body.
Moreover, the present invention has been described on the premise of a communication failure by re-transmission but it is needless to say that an apparent delay occurrence phenomenon other than re-transmission of a message can be also handled.
Furthermore, the present invention can be applied not only to the communication device for mobile body control but widely to communication devices and systems that cannot employ error correction codes and the like regardless of necessity of time synchronization between apparatuses. -12-
Claims (7)
- What is claimed is: 1. A spot transmission communication device for conducting spot transmission communication between a trackside communication device installed on the ground and a mobile body communication device installed on a mobile body through an on-board antenna installed on the mobile body and detecting the trackside communication device by measuring intensity of a signal received from the trackside communication device, wherein a mobile body control portion connected to the mobile body communication device through a transmission path is provided on the mobile body; the mobile body control portion has a communication portion for transmitting a message to the mobile body communication device and a system time management portion for creating system time to be added to the message; the mobile body communication device has: a self timer for creating a self timer value; a current time storage portion for storing both the system time added to a latest message received from the mobile body control portion and the self timer value when the message is received; a past time storage portion for storing, when a message has been received prior to the latest message, both the system time of the previous message and the self timer value when the previous message was received; and a time synchronization portion for creating a timer value for synchronization which is time for position calculation of the trackside communication device; in the time synchronization portion, occurrence of a communication failure between the mobile body communication device and the mobile body control portion is detected from the respective system time added to the latest message and the previous message from the mobile body control portion and the self timer values when the respective messages were received, and the synchronization timer is corrected in accordance with presence of occurrence of a failure; and detection time of the trackside communication device is estimated by using the corrected synchronization timer.
- 2. The spot transmission communication device according to claim 1, wherein detection of occurrence of a communication failure between the mobile body communication device and the mobile body control portion is made by comparing increases of the respective system time in the latest message and the previous message and the time of self timer values when the respective messages were received and if a comparison value is not less than a specified value 1, it is detected that the communication failure has occurred; the specified value 1 is assumed to be a value larger than a value obtained by dividing a position allowable error of the mobile body by a maximum speed of the mobile body; and -13-the synchronization timer is to correct a value obtained by adding an increase of the system time to the timer value for synchronization of the previous message as a timer value for synchronization.
- 3. The spot transmission communication device according to claim 1 or 2, wherein detection of occurrence of a communication failure between the mobile body communication device and the mobile body control portion is made by comparing increases of the respective system time in the latest message and the previous message and the time of self timer values and if a comparison value is less than the specified value 1, it is detected that the communication failure has not occurred; and as the timer value for synchronization, the self timer value when the latest message was received is employed.
- 4. The spot transmission communication device according to any one of claims 1 to 3, wherein time obtained by adding a difference between the self timer value at detection of the trackside communication device and the timer value for synchronization to the system time stored in the current time storage means is calculated as detection time of the trackside communication device.
- 5. The spot transmission communication device according to any one of claims 1 to 4, wherein if the message is sent from the mobile body control portion at a regular constant interval, a value twice a processing time difference generated between a case in which a load of the mobile body control portion is maximum and a case in which the load is minimum is set to a specified value 2, and if an increase of the system time added to the received message is not less than the specified value 2, it is determined that abnormality has occurred.
- 6. The spot transmission communication device according to any one of claims 1 to 5, wherein increases of the respective system time in the latest message and the previous message and the self timer values when the respective messages were received are compared, and if the comparison value is larger than a maximum delay time by re-transmission, it is determined that abnormality has occurred in the self timer.
- 7. A time correcting method of a spot transmission communication device comprising: a first step in which a mobile body communication device receives a message including system time (Ic, N) from a mobile body control portion and stores the -14-received system time (Tc, N) and a self timer value [FR. N) when the message was received in a set in a current time storage portion; a second step in which whether or not a reception is a first system time reception from the mobile body control portion is determined, and in a case of first reception, the received system time (Tc, N) is set to a timer value for synchronization (TG, N), and the system time and the self timer value are recorded in a set in the current time storage portion, while if the reception is not the first reception, a difference (ATc, N) between the system time (Tc, N) received this time and the system time (Tc, N-i) received the previous time stored in the current time storage portion and a past time storage portion is calculated; a third step of calculating a difference (ATR, N) between the self timer value (TR, N) received this time and the self timer value (TR. N-i)received the previous time stored in the current time storage portion and the past time storage portion; a fourth step of comparing a difference value between the (ATc. N) and the (ATR.N) calculated at the second step and the third step with a specified value 1 as a threshold value and determining whether or not out-of-synchronization has been caused by re-transmission; and a fifth step in which, in case of ATc. N -ATR. N < the specified value 1, the timer value for synchronization is set and stored as TG, N = ft N, while in a case of ATc, N -AIR, N »= the specified value 1, the timer value for synchronization is set and stored as To, N = To. N-i + ATc. N.
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| JP2014120979A JP6199242B2 (en) | 2014-06-11 | 2014-06-11 | Spot transmission communication device |
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| GB2527654A true GB2527654A (en) | 2015-12-30 |
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| CN112887939B (en) * | 2019-11-29 | 2023-02-28 | 阿波罗智能技术(北京)有限公司 | Vehicle information determination method and device, electronic equipment and storage medium |
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| US6975652B1 (en) * | 2000-10-18 | 2005-12-13 | 3Com Corporation | Clock synchronization of HFC telephone equipment |
| US20100268980A1 (en) * | 2009-04-17 | 2010-10-21 | Denso Corporation | Node apparatus mounted in vehicle and in-vehicle network system |
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| DE102015210261B4 (en) | 2019-11-14 |
| JP6199242B2 (en) | 2017-09-20 |
| GB2527654B (en) | 2016-09-14 |
| JP2016001808A (en) | 2016-01-07 |
| DE102015210261A1 (en) | 2015-12-17 |
| GB201507327D0 (en) | 2015-06-10 |
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