TW201338581A - Communication method and communication system - Google Patents

Abstract

A communication system includes a step of utilizing time data stored in an on-vehicle equipment in the case in which the level of GPS reception is lower than a predetermined level or the on-vehicle equipment is in a low-accuracy location which is recorded in a database of places where GPS accuracy is low.

Description

Communication method and communication system

The present invention relates to a communication method and communication system for transmitting data from a base station to a plurality of mobile stations and transmitting data from the mobile station to the base station.

The present application claims priority based on Japanese Patent Application No. 2012-025002, filed on Jan.

Patent Document 1 describes an example of a communication system. The communication system of Patent Document 1 includes a wireless base station having a plurality of wireless communication units that perform wireless communication by mutually different communication channels, and a wireless communication unit that can change the communication channel. Further, the communication system of Patent Document 1 includes a wireless terminal that receives a service provided via a wireless base station by wirelessly communicating with a wireless base station by the wireless communication unit.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open Publication No. 2010-226271

In the field of ITS (Intelligent Transport System), WAVE (Wireless Access in Vehicular Environments) communication standard is used in various traffic-related services that are intended to be used in common for road toll collection. The vehicle-mounted device has a communication system for performing road-vehicle-to-vehicle-vehicle-vehicle communication.

As shown in FIG. 6, the communication system 100 performs road toll collection by receiving the information transmitted from the vehicle 102 traveling on the road 101 by the toll collector 103 installed on the road 101.

As shown in FIG. 7, as an application example of the vehicle-to-vehicle communication, the communication system 100 issues a notification "there is an emergency vehicle approaching from the rear" to the vehicle 102 traveling on the road 101 when the emergency vehicle approaches. Or, when the emergency vehicle approaches, issue a notice 105 of "Attention to the Vehicle in Front".

As shown in FIG. 8, such a communication system 100 realizes different types of services according to purposes, and divides the used communication band into a plurality of communication channels 110 by time division. The communication channel 110 is divided into a control channel CC and a service channel SC, which are common to all communication terminals 1, 2, 3, wherein the next service channel SC is indicated and communication is established. On the other hand, in the service channel SC, information is transmitted and received, and the control channel CC and the service channel SC are alternately repeated, thereby realizing different information services by using time division and parallel.

Here, the communication channel 110 must synchronize the timing, the interval, and the start timing on the transmitting side and the receiving side. As a method of synchronizing the communication channel 110, any of the following methods is usually adopted. One of the synchronization methods uses an UTC (Universal Time, Coordinated) absolute time included in a signal of a GPS (Global Positioning System). The second method of synchronization is that the start timing of the communication message from the base station is positive and consistent with it.

However, as shown in FIG. 9, the communication system 100 is in a place where it is not possible to stably receive GPS radio waves between buildings or tunnels, and if this state is continued for a long period of time, an interval for correct time correction by GPS is vacated. Thereby, the time is maintained by the built-in clock during this period, and thus the error is accumulated. Therefore, in the communication between the vehicles 120, 130, and 140, it is necessary to make the start timings coincide with each other. Therefore, if the accumulated error exceeds the guard interval, the communication conflicts and fails.

On the other hand, in Patent Document 1, even if the data of each of the plurality of services is received in parallel, the respective service materials can be completely received, and the data can be flexibly received in parallel according to the user's request. However, in the communication system in which it is necessary to synchronize the timing of the communication time slot, the patent document 1 performs time synchronization in accordance with the absolute time included in the GPS signal or the communication message from the base station. Therefore, Patent Document 1 requires a GPS function or a base station, and when an interval of correct time correction by GPS is vacated, the error is accumulated by the built-in clock holding time during this period, and the accumulated error exceeds the guard interval. The situation. Therefore, Patent Document 1 has a case where a collision or failure of communication occurs.

The present invention has been made to solve the above problems, and an object of the invention is to provide a communication method and a communication system capable of maintaining an accurate timing of communication when a GPS cannot be stably received for a long period of time.

In order to solve the above problem, a first aspect of the present invention provides a communication method for transmitting data from a base station to a plurality of mobile stations via a downlink channel, and transmitting one of the plurality of mobile stations from the plurality of mobile stations to the base station via the uplink channel. The data source includes: a step of receiving a GPS wave by the mobile station; a step of determining the quality of the received GPS wave; and a step of setting the time obtained from the GPS wave to the mobile station when the quality of the GPS wave is more than a specific condition According to the position of the mobile station, and referring to the GPS time accuracy reduction site database to determine whether it is located in the accuracy reduction position; and the accuracy of the GPS radio wave is specified below, or the mobile station is located in the GPS time accuracy reduction database The step of applying the mobile station at the time of lowering the location.

The communication method may be applied to a time when a wireless LAN (Local Area Network) is applied when the quality of the GPS wave is equal to or less than a specific time and the time quality of the mobile station is equal to or lower than a specific one.

A second aspect of the present invention is a communication system including: a WAVE communication function unit that communicates with a roadside device or another vehicle by WAVE communication; The GPS time output function unit generates an absolute time based on the GPS radio wave received from the GPS, and outputs the absolute time as a GPS time for the reference signal for the WAVE communication synchronization signal, and outputs the GPS radio wave reception quality; The telephone time output function unit generates an absolute time based on the radio wave received from the mobile phone base station, and outputs the absolute time as a mobile phone time for the reference for the synchronization signal for WAVE communication, and outputs the mobile phone radio wave Receive quality; position estimation function unit obtains position information from GPS, and infers its position according to the road map data corrected to the position on the road, outputs the self position as its own position information, and can display the position information and the indication result To what extent, reliable reliability is output together; the synchronization signal output function unit corrects the built-in clock by using the mobile phone time, the GPS time, the position information, and the reliability, and outputs the WAVE communication based on the time of the built-in clock. Synchronization signal; road map database with location inference function Use of the road information; and reduce the accuracy of GPS time places database, which is measured in advance prior precision, will likely lead to a higher likelihood of reduced time accuracy of GPS database of places.

The communication system may further include: a wireless LAN time output function unit that creates an absolute time based on the radio wave received from the wireless LAN access point, outputs the absolute time as a synchronization signal for WAVE communication, and outputs the wireless LAN The reception quality of the access point radio wave; and the synchronization signal output function unit that switches any of the mobile phone time output, the GPS time output, the wireless LAN time output, and the built-in clock, and outputs a synchronization signal required for WAVE communication.

According to the communication system of the present invention, it is possible to maintain the accuracy of the communication timing when the GPS radio wave cannot be stably received for a long period of time.

10, 30‧‧‧Communication system

11, 31‧‧‧ Vehicles

12, 32‧‧‧WAVE Communication Function Department

13, 33‧‧‧ GPS time output function

14, 34‧‧‧Mobile Phone Time Output Function

15, 35‧‧‧Location Inference Function Department

16, 36‧‧‧ Synchronous signal output function

17, 37‧‧‧Road Map Database

18, 38‧‧‧ GPS Time Accuracy Reduction Site Database

19‧‧‧ Roadside equipment, other vehicles

20‧‧‧GPS waves

22‧‧‧Mobile Phone Base Station

39‧‧‧Wireless LAN time output function

40‧‧‧Wireless LAN access point

100‧‧‧Communication system

101‧‧‧ Road

102‧‧‧ Vehicles

103‧‧‧charger

104‧‧‧With vehicles approaching from behind

105‧‧‧Attention to the vehicle ahead

110‧‧‧Communication channel

120, 130, 140‧‧‧ vehicles

CC‧‧‧Control channel

SC‧‧‧ service channel

Fig. 1 is a functional block diagram of a communication system according to a first embodiment of the present invention.

Fig. 2 is a flow chart showing the control operation of the communication system according to the first embodiment of the present invention; Figure.

Fig. 3 is a functional block diagram of a communication system according to a second embodiment of the present invention.

Fig. 4 is a view showing an area of a communication system according to a second embodiment of the present invention.

Fig. 5 is a flow chart for explaining the control operation of the communication system according to the second embodiment of the present invention.

Figure 6 is a schematic diagram of an associated communication system.

Fig. 7 is a schematic diagram showing an application example of vehicle-to-vehicle communication of the associated communication system.

Figure 8 is a schematic diagram of the time channel of the associated communication system.

Figure 9 is an explanatory diagram of the error of the associated communication system.

Hereinafter, a communication system according to a plurality of embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the communication system 10 according to the first embodiment of the present invention is mounted on the vehicle-mounted device 11, and includes a WAVE communication function unit 12, a GPS time output function unit 13, a mobile phone time output function unit 14, and Position estimation function unit 15. Further, the communication system 10 includes a synchronization signal output function unit 16, a road map database 17, and a GPS time accuracy reduction location database 18.

The WAVE communication function unit 12 communicates with the roadside device (or other vehicle) 19 by WAVE communication. The GPS time output function unit 13 generates an absolute time based on the GPS radio wave 20 received from the GPS, and outputs the absolute time as a GPS time for the reference signal for the WAVE communication synchronization signal, and outputs the GPS radio wave reception quality. The mobile phone time output function unit 14 creates an absolute time based on the radio wave received from the mobile phone base station 22, and outputs the absolute time as a mobile phone time for the reference signal for the WAVE communication synchronization signal, and outputs the action. Telephone wave reception quality.

The position estimation function unit 15 obtains position information from the GPS wave 20, and estimates the position of the road based on the road map data, and uses the position as the self. The position information is outputted, and the position information is output together with the reliability indicating how reliable the inference result can be. The synchronization signal output function unit 16 corrects the built-in clock by using the mobile phone time, the GPS time, the position information, and the reliability, and outputs a synchronization signal required for WAVE communication based on the built-in clock time. The road map database 17 stores the road information used by the position estimation function unit 15. The GPS time accuracy reduction location database 18 is pre-measurement accuracy, and the location of the place where the possibility of GPS time accuracy is likely to be reduced is stored and stored.

Next, the control operation of the communication system 10 will be described. Here, the synchronization signal output function unit 16 is configured to correct the processing of the built-in clock using the mobile phone time, the GPS time, the position information, and the reliability. As shown in FIG. 2, when the control is started, the GPS time-of-day output function unit 13 receives the latest information of the GPS radio wave reception quality and the GPS time (S101). Thereafter, the position estimation function unit 15 receives the latest information on the position information and the reliability (S102).

Then, when it is determined that the received GPS radio wave reception quality is equal to or greater than a predetermined threshold value, the current position is referred to the GPS time accuracy reduction location database 18 (S103→S104). Then, when the positional information and the reliability of the position estimation function unit 15 are used to determine that the reliability is more than or equal to the position in the GPS time accuracy reduction location database 18, it is determined that the reliability is not available. The GPS time is entered into the correction determination using the mobile phone time (S105→S106).

At this time, when it is determined that the reliability is not fixed or is not present in the position in the GPS time accuracy reduction location database 18, the built-in clock is corrected at the GPS time (S105→S107). Thereafter, the synchronization signal is output to the WAVE communication function unit 12 based on the built-in clock timing (S110). At this time, when it is determined that the GPS radio wave 20 cannot be stably received from the GPS radio wave reception quality, the mobile phone time output function unit 14 receives the latest information of the mobile phone radio wave reception quality and the mobile phone time (S106).

Thereafter, it is determined that the reception quality of the mobile phone radio wave is a predetermined threshold value. In the case of the above, the built-in clock is corrected at the time of the mobile phone (S108 → S109). In this case, when the reception quality of the mobile phone radio wave is not equal to or greater than the predetermined threshold value, the built-in clock is not corrected at the mobile phone time, and the WAVE communication is performed by the built-in clock output synchronization signal (S108→S110). Thereafter, the synchronization signal is output to the WAVE communication function unit 12 based on the built-in clock timing (S110).

As described above, in the communication system 10 according to the first embodiment of the present invention, when the GPS radio wave 20 cannot be stably received for a long period of time, the timing of the communication can be maintained at the time of the mobile phone.

Further, according to the communication system 10, in the case where the GPS radio wave 20 can be stably received but in a situation where the accuracy is lowered in advance, the reference switching of the GPS time and the mobile phone time can be avoided by applying the mobile phone time. Causes unstable movements.

Next, a communication system according to a second embodiment of the present invention will be described. In the second embodiment, the components that are the same as those in the above-described first embodiment are denoted by the same reference numerals or the same reference numerals, and the description thereof will be simplified or omitted.

As shown in FIG. 3, the communication system 30 according to the second embodiment of the present invention is mounted on the vehicle-mounted device 31, and includes a WAVE communication function unit 32, a GPS time output function unit 33, a mobile phone time output function unit 34, and Position estimation function unit 35. Further, the communication system 30 includes a synchronization signal output function unit 36, a road map database 37, a GPS time accuracy reduction location database 38, and a wireless LAN time output function unit 39.

The WAVE communication function unit 32 communicates with the roadside device (or other vehicle) 19 by WAVE communication. The GPS time output function unit 33 generates an absolute time based on the GPS wave 20 received from the GPS, and outputs the absolute time as a GPS time for the reference for the synchronization signal for WAVE communication, and outputs the GPS radio wave reception quality. The mobile phone time output function unit 34 creates an absolute time based on the radio wave received from the mobile phone base station 22, and uses the absolute time as a synchronization signal for WAVE communication. The mobile phone of the standard is output at the moment, and the radio wave reception quality of the mobile phone is output.

The position estimation function unit 35 obtains position information from the GPS wave 20, and estimates the position of the road map data based on the road map data, and outputs the position as its own position information, and can display the position information and the indication result. To what extent, reliable reliability is output together. The synchronization signal output function unit 36 switches any of the mobile phone time output, the GPS time output, the wireless LAN time output, and the built-in clock, and outputs a synchronization signal required for WAVE communication. The road map database 37 stores the road information used by the position estimation function unit 35. The GPS time accuracy reduction location database 38 is based on pre-measurement accuracy, and is stored in a place where the possibility of a decrease in GPS time accuracy is high. Thereafter, the wireless LAN time output function unit 39 creates an absolute time based on the radio wave received from the wireless LAN access point, and outputs the absolute time as a synchronization signal for WAVE communication. Further, the reception quality of the wireless LAN access point radio wave is output.

As shown in FIG. 4, the communication system 30 periodically transmits a plurality of wireless LAN access points 40 in advance using a wireless LAN in a place where the GPS and the mobile phone base station 22 cannot be used. Built-in clock correction with beacon signals.

Next, the control operation of the communication system 30 will be described. As shown in FIG. 5, when the control is started, the GPS time output function unit 33 receives the latest information of the GPS radio wave reception quality and the GPS time (S201). Thereafter, the position estimation function unit 35 receives the latest information of the position information and the reliability (S202).

Then, when it is determined that the received GPS radio wave reception quality is equal to or greater than a predetermined threshold value, the current position is referred to the GPS time accuracy reduction location database 38 (S203→S204). Then, when the positional information and the reliability of the position estimation function unit 35 are used to determine that the reliability is more than or equal to the position of the GPS time accuracy reduction location database 38, it is determined that the GPS time cannot be used. Then, the determination is made by using the mobile phone time (S205 → S206).

At this time, when it is determined that the reliability is not fixed or is not present in the position in the GPS time accuracy reduction location database 38, the built-in clock is corrected at the GPS time (S205→S207). When it is determined that the GPS radio wave cannot be stably received from the GPS radio wave reception quality, the mobile phone time output function unit 34 receives the latest information of the mobile phone radio wave reception quality and the mobile phone time (S206).

Then, when it is determined that the reception quality of the mobile phone radio wave is not equal to or greater than the predetermined threshold value, the wireless LAN time output function unit 39 receives the wireless LAN access point radio wave reception quality and the wireless LAN time (S208→S209). ). At this time, when it is determined that the reception quality of the mobile phone radio wave is equal to or greater than a predetermined threshold value, the built-in clock is corrected at the mobile phone time (S208→S210).

When it is determined that the received radio wave access point radio wave reception quality and the radio LAN access point radio wave reception quality at the wireless LAN time are equal to or greater than a predetermined threshold value, the built-in clock time is corrected at the wireless LAN access point time ( S211→S212). When it is determined that the received radio wave access point radio wave reception quality and the wireless LAN access point radio wave reception quality at the wireless LAN time are not equal to or greater than a predetermined threshold value, the WAVE communication function is based on the built-in clock time. The portion 32 outputs a synchronization signal (S213).

According to the communication system 30 of the second embodiment, when the GPS radio wave 20 cannot be stably received for a long period of time and the radiotelephone radio wave reception quality cannot be stably received, the timing of the communication can be surely obtained by the wireless LAN time information.

Further, according to the communication system 30, the location of any of the GPS and the mobile phone base station 22 can be used, and the built-in clock can be corrected by using the beacon signal periodically transmitted by the wireless LAN of the plurality of wireless LAN access points 40. .

Furthermore, the communication system of the present invention is not limited to the above-described embodiments, and can be appropriately modified or improved.

As described above, according to the communication system of the present invention, the timing of the accurate communication can be maintained when the GPS radio wave 20 cannot be stably received for a long time. As a result of the above, The product can be stabilized and the quality can be improved, and the industrial availability of the present invention can be said to be large.

[Industrial availability]

According to the state of the present invention, it is possible to provide a communication system capable of maintaining an accurate timing of communication when a GPS wave cannot be stably received for a long period of time.

10‧‧‧Communication system

11‧‧‧Vehicle

12‧‧‧WAVE Communication Function Department

13‧‧‧GPS time output function

14‧‧‧Mobile Phone Time Output Function

15‧‧‧Location Inference Function Department

16‧‧‧Synchronous signal output function

17‧‧‧Road Map Database

18‧‧‧GPS Time Accuracy Reduction Site Database

19‧‧‧ Roadside equipment, other vehicles

20‧‧‧GPS waves

22‧‧‧Mobile Phone Base Station

Claims (4)

A communication method is that a base station transmits data to a plurality of mobile stations via a downlink channel, and selects one of the plurality of mobile stations to transmit data to the base station via the uplink channel; and includes: the mobile station receives the GPS a step of determining a quality of the received GPS radio wave; and a step of setting a time obtained from the GPS radio wave to the mobile station when the quality of the GPS radio wave is more than a specific condition; and according to the mobile station a position, and a step of determining whether the position is located at the accuracy reduction position with reference to the GPS time accuracy reduction site database; and the accuracy reduction position of the GPS radio wave having a quality below or below, or the mobile station being present in the GPS time accuracy reduction location database In the case of the case, the step of applying the above-mentioned mobile station. The communication method of claim 1, further comprising the step of applying a wireless LAN when the quality of the GPS radio wave is equal to or less than a specific time and the time quality of the mobile station is equal to or less than a specific time. A communication system including: a WAVE communication function unit that communicates with a roadside device or another vehicle by WAVE communication; and a GPS time output function unit that makes an absolute time based on GPS waves received from the GPS, and The absolute time is output as a GPS time for a reference for a synchronization signal for WAVE communication, and outputs GPS radio wave reception quality; and a mobile phone time output function unit that creates an absolute time based on radio waves received from the mobile phone base station, And outputting the absolute time as a mobile phone time for the reference of the synchronization signal for WAVE communication, and outputting the line The mobile phone radio wave receiving quality; the position inference function unit obtains the position information from the GPS, and corrects the position according to the road map data corrected to the position on the road, outputs the self position as its own position information, and sets the position information and The synchronization signal output function unit corrects the built-in clock by using the mobile phone time, the GPS time, the position information, and the reliability, and the built-in clock is based on the above-mentioned mobile phone time, the GPS time, the position information, and the reliability described above. The synchronization signal required for the WAVE communication is outputted at the time of the clock; the road map database has the road information used by the position estimation function; and the GPS time precision reduction location database, the pre-measurement accuracy of the time may cause The location of the above-mentioned GPS where the accuracy of the accuracy is lowered is high. The communication system of claim 3, further comprising: a wireless LAN time output function unit that creates an absolute time based on the radio wave received from the wireless LAN access point, and uses the absolute time as a synchronization signal for the WAVE communication Outputting and outputting the reception quality of the wireless LAN access point radio wave; and a synchronization signal output function unit that switches between the mobile phone time output, the GPS time output, the wireless LAN time output, and the built-in clock, And the synchronization signal required for the above WAVE communication is output.