JP2004304250A - Automobile information system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automobile information system for performing smooth data communication even when radio wave environment conditions are deteriorated. <P>SOLUTION: An in-vehicle information terminal 2 performs a request of reducing a data capacity per one packet to an information center when the present position of an automobile is within an area where a radio wave environment is deteriorated, when the electric field intensity of a radio wave from an information center base station 3 becomes lower than a predetermined threshold, or when the BER of the result of communication with the information center 1 exceeds a predetermined threshold. Upon receiving the data capacity reduction request from the terminal 2, the information center 1 reduces the data capacity per one packet, and distributes various kinds of information to the in-vehicle information terminal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automobile information system that exchanges various information between an automobile and an information center.
[0002]
[Prior art]
A navigation system that selects the route with the best communication environment with the information center from among multiple routes to the destination, and enables good data communication between the onboard information terminal and the information center while traveling Is known (for example, see Patent Document 1).
[0003]
Prior art documents related to the invention of this application include the following.
[Patent Document 1]
JP-A-2000-131083
[Problems to be solved by the invention]
However, if the communication environment cannot select the optimal route, data retransmission frequently occurs due to the deterioration of the radio wave environment in urban or suburban areas where high-rise buildings are dense, and it takes time to download data. There is.
[0005]
The present invention provides an automobile information system that performs smooth data communication even under a poor radio wave environment.
[0006]
[Means for Solving the Problems]
The present invention, in the on-board information terminal, when the current location of the vehicle enters the radio wave environment degradation area, or when the electric field strength of the radio wave from the information center base station is lower than a predetermined threshold, or When the BER of the communication result with the information center exceeds a predetermined threshold value, the information center issues a data capacity reduction request per packet to the information center, and the information center receives the data capacity reduction request from the in-vehicle information terminal. Sometimes, the data capacity per packet is reduced, and various types of information are distributed to the in-vehicle information terminal.
[0007]
【The invention's effect】
Advantageous Effects of Invention According to the present invention, smooth data communication can be performed even in a situation where the radio wave environment is poor.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a configuration of an embodiment. The vehicle information system according to one embodiment includes an information center 1 and an in-vehicle information terminal 2 mounted on a plurality of vehicles. The information center 1 distributes various types of information from a plurality of base stations 3 to the in-vehicle information terminals 2 by wireless communication.
[0009]
The in-vehicle information terminal 2 includes a mobile phone 4, a GPS receiver 5, a radio wave environment deterioration database 6, a controller 7, a display 8, a speaker 9, an input device 10, and the like. Although a mobile phone or an in-vehicle phone is used as the mobile phone 4, a general wireless communication device can also be used. The GPS receiver 5 receives a signal wave from a GPS satellite and detects the current position of the vehicle by satellite navigation. The travel distance may be calculated by detecting the moving distance and traveling direction of the vehicle, and the current position may be detected by autonomous navigation by performing map matching with a road map.
[0010]
The radio wave environment degradation database 6 previously measures the reception level of radio waves emitted from the base station 3 while actually traveling on a road, and stores an area having a low reception level of radio waves as a radio environment degradation area in a storage device. is there.
[0011]
The controller 7 includes a CPU 7a, a ROM 7b, a RAM 7c, etc., communicates with the information center 1 via the mobile telephone 4, downloads various information from the information center 1, and notifies the occupant through the display 8 and the speaker 9. The occupant can use the input device 9 to request download of desired information.
[0012]
Here, data communication by a PDC (Personal Digital Cellular System) mobile phone will be described with reference to FIG. In the data communication by the PDC type mobile phone, as shown in (a), one frequency is shared by six mobile phones, and data communication is performed in a time-division manner into packets 1 to 6 every 6.5 mS. .
[0013]
One packet is divided into three blocks of a protocol header 21, a data body 22, and an error detection code 23 as shown in FIG. The protocol header 21 records a destination address, a source address, a flag indicating data content, and the like. The error detection code 23 is a code for confirming whether data of one packet has been correctly transmitted.
[0014]
Each time the in-vehicle information terminal 2 receives one packet data from the information center 1, it checks with the error detection code 23 whether the received one packet data is correct. When one packet data is correctly received, a notification of reception is made to the information center 1, and when an error is detected in the received data, an error notification is made to the information center 1. The information center 1 having received the error notification retransmits one packet data having a transmission error.
[0015]
The data communication speed of a PDC mobile phone is 9600 bps, which is lower than the data communication speed of a fixed telephone. On the other hand, in an urban area or a suburb where high-rise buildings are densely located, there are areas where the radio wave environment from the information center base station 3 is deteriorated. In such places, transmission errors are likely to occur, and data retransmission frequently occurs. become. Therefore, the occupants are uncomfortable with the long data download.
[0016]
Therefore, in this embodiment, the capacity of the data body 22 in one packet is reduced according to the deterioration of the radio wave environment. FIG. 3 shows a packet structure in the case where the data capacity in one packet is reduced to half of the normal capacity. In this case, half of the data body 22 is defined as valid data 22a, and the other half is defined as meaningless invalid data 22b. The detection of the data transmission error described above is performed only for the valid data 22a in the data body 22.
[0017]
The larger the data capacity in one packet is, the longer the data transmission time is. Therefore, the data transmission time is easily affected and the data transmission error is likely to occur. As shown in FIG. 3, if the capacity of the transmission data in one packet is reduced to half, the transmission time of the data itself is reduced to half that of the normal case. Is approximately １ ／.
[0018]
In this case, if the data capacity in one packet is halved, data of the same capacity is divided into two packets, and the communication time becomes longer. However, in an environment where the radio wave environment is poor, data retransmission is usually performed many times in many packets, so that the communication time is longer than the communication time that increases due to the reduction in the data capacity per packet.
[0019]
In other words, by reducing the data capacity per packet and performing data transmission by dividing the data into a plurality of packets, occurrence of data transmission errors can be suppressed, and smooth data communication can be performed even in a poor radio wave environment. it can. Therefore, the data download time can be reduced.
[0020]
In this embodiment, the radio wave environment degradation database 6 stores information about an area where the reception level of radio waves from the base station 3 is low. Make a reduction request. The information center 1 that has received the data capacity reduction request performs data transmission while reducing the data capacity per packet.
[0021]
On the other hand, the mobile phone always detects the electric field strength of the received radio wave and the BER (Bit Error Rate) of the communication result. The mobile phone receives a radio wave from the base station 3 even in the standby state, and constantly detects the electric field strength and displays the electric field strength in a bar graph. On the other hand, the mobile phone detects the BER of the communication result when the communication is actually performed. The lower the electric field strength of the received radio wave and the higher the BER of the communication result, the more the radio wave environment is degraded.
[0022]
The in-vehicle information terminal 2 sets threshold values for the electric field strength of the received radio wave and the BER of the communication result, and constantly monitors the electric field strength and the BER of the received radio wave of the mobile telephone 4. Then, when the electric field strength of the received radio wave falls below the threshold value or when the BER of the communication result exceeds the threshold value, the information center 1 is requested to reduce the data capacity per packet.
[0023]
FIG. 4 is a flowchart showing a data capacity reduction request process executed by the controller 7 of the onboard information terminal 2. The operation of the embodiment will be described with reference to this flowchart.
[0024]
When an occupant requests acquisition of traffic information, weather information, news, a sightseeing guide, a town guide, etc. from the input device 10, the controller 7 calls the information center 1 from the mobile telephone 4 and connects the telephone line. In step 1, when a line to the information center 1 is connected, a data capacity reduction process is started.
[0025]
In step 2, the current position of the vehicle is detected by the GPS receiver 5. In step 3, it is checked whether the current position of the vehicle has entered the radio wave environment degradation area stored in the radio wave environment degradation database 6. If the current position of the vehicle is in the radio wave environment degraded area, the process proceeds to step 6 and requests the information center 1 to reduce the data capacity.
[0026]
The information center 1 that has received the data capacity reduction request performs data transmission in the subsequent data transmission by reducing the data capacity per packet to a predetermined amount. In step 7, it is confirmed whether or not the telephone line has been disconnected from the information center 1. If the line has been disconnected, the process is terminated. If the line has not been disconnected, the process returns to step 2 to repeat the above process.
[0027]
On the other hand, if it is determined in step 3 that the current position of the vehicle is not in the radio wave environment degraded area, the process proceeds to step 4. In step 4, it is confirmed whether or not the electric field strength of the radio wave of the information center 1 detected by the mobile telephone 4 is lower than a predetermined threshold. If the electric field strength of the received radio wave is lower than the threshold value, the process proceeds to step 6 and requests the information center 1 to reduce the data capacity.
[0028]
The information center 1 that has received the data capacity reduction request performs data transmission in the subsequent data transmission by reducing the data capacity per packet to a predetermined amount. In step 7, it is confirmed whether or not the telephone line has been disconnected from the information center 1. If the line has been disconnected, the process is terminated. If the line has not been disconnected, the process returns to step 2 to repeat the above process.
[0029]
If it is determined in step 4 that the electric field strength of the received radio wave is equal to or higher than the threshold, the process proceeds to step 5 to determine whether the BER of the communication result with the information center 1 is higher than a predetermined threshold. Check whether or not. If the BER of the communication result is higher than the threshold, the process proceeds to step 6 and requests the information center 1 to reduce the data capacity.
[0030]
The information center 1 that has received the data capacity reduction request performs data transmission in the subsequent data transmission by reducing the data capacity per packet to a predetermined amount. In step 7, it is confirmed whether or not the telephone line has been disconnected from the information center 1. If the line has been disconnected, the process is terminated. If the line has not been disconnected, the process returns to step 2 to repeat the above process.
[0031]
If all of steps 3 to 5 are denied, that is, if the current position is not in the radio wave environment degraded area, the electric field strength of the received radio wave is equal to or higher than the threshold, and the BER of the communication result is equal to or lower than the threshold, Proceed to step 8. In step 8, it is confirmed whether or not the data capacity is currently being reduced. If the data capacity is being reduced, the process proceeds to step 9, where a request to cancel the data capacity reduction is made to the information center 1. On the other hand, if the data capacity is not currently being reduced, the process returns to step 2 and the above-described processing is repeated.
[0032]
The information center 1 that has received the data capacity reduction release request returns the data capacity per packet to the normal capacity and performs data transmission in the subsequent data transmission.
[0033]
As described above, according to the embodiment, when the current location of the vehicle enters the deteriorating area of the radio wave environment or the electric field intensity of the radio wave from the information center base station 3 is determined in advance in the on-board information terminal 2. When the value becomes lower than the threshold value or when the BER of the communication result with the information center 1 exceeds a predetermined threshold value, the data center 1 is requested to reduce the data capacity per packet. Reduces the data capacity per packet when a data capacity reduction request is received from the in-vehicle information terminal 2, so that the occurrence of data retransmission can be reduced even in a poor radio wave environment, Data communication can be performed.
[0034]
In the above-described embodiment, an example has been described in which, when there is a data capacity reduction request from the on-board information terminal 2, the data capacity reduction amount per packet is set to a predetermined fixed amount. The reduction amount of the data capacity may be continuously variable according to the electric field strength and the BER of the communication result. That is, the lower the electric field strength of the received radio wave and the higher the BER of the communication result, the greater the amount of reduction in data capacity. When the amount of reduction in data capacity is set in accordance with the electric field strength and the BER, when it is determined in the in-vehicle information terminal 2 that the request for reduction in data capacity is to be made as described above, when the request for reducing data capacity is made, The electric field strength and the BER detection value of the communication result are sent to the information center 1. The information center 1 determines a reduction amount of the data capacity according to the electric field strength and the BER transmitted from the onboard information terminal 2. By determining the amount of reduction in data capacity according to the electric field strength of the received radio wave and the BER of the communication result, it is possible to reduce the occurrence of data retransmission even in an environment with a poor radio wave environment and download data while performing smooth data communication. Time can be reduced.
[0035]
Also, in the above-described embodiment, an example is shown in which the dedicated GPS receiver 5 is provided in the in-vehicle information terminal 2. However, in a vehicle equipped with a navigation device, the GPS receiver of the navigation device is used or shared. It may be.
[0036]
Further, in the above-described embodiment, an example is described in which the in-vehicle information terminal 2 determines whether to reduce the data capacity. However, the information center 1 may make the determination. In this case, the radio wave environment deterioration database 6 is installed in the information center 1, and the current position of the vehicle, the electric field strength of the received radio wave, and the BER of the communication result are transmitted from the in-vehicle information terminal 2 to the information center 1. The information center 1 determines whether the current position of the vehicle is in the radio wave environment degraded area, whether the electric field strength of the received radio wave is lower than the threshold, and whether the BER of the communication result is higher than the threshold. It is sufficient to make a determination and determine whether to reduce the data capacity.
[0037]
The correspondence between the components of the claims and the components of the embodiment is as follows. That is, the GPS receiver 5 is a current position detecting means, the radio wave environment deterioration database 6 is a radio wave environment storage means, the controller 7 is a communication control means, the information center 1 is a data capacity control means, and the mobile telephone 4 is a field strength detecting means. And BER detection means. Note that each component is not limited to the above configuration as long as the characteristic functions of the present invention are not impaired.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment.
FIG. 2 is a diagram for explaining a data communication system by a PDC mobile phone.
FIG. 3 is a diagram illustrating a packet structure according to an embodiment;
FIG. 4 is a flowchart illustrating a data capacity reduction process according to an embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Information center 2 In-vehicle information terminal 3 Base station 4 Mobile telephone 5 GPS receiver 6 Radio wave environment degradation database 7 Controller 7a CPU
7b ROM
7c RAM
8 display 9 speaker 10 input device 21 protocol header 22 data body 22a valid data 22b invalid data 23 error detection code

Claims (7)

In an automobile information system that performs data communication in packet units via a mobile phone or an in-vehicle phone and distributes various information from an information center to an in-vehicle information terminal,
In the in-vehicle information terminal, a current position detecting means for detecting the current position of the vehicle,
Radio wave environment storage means for storing the radio wave environment degraded area of the information center base station;
Communication control means for constantly monitoring whether or not the current position of the vehicle has entered the radio wave environment degraded area, and when entering the radio wave environment degraded area, requests the information center to reduce the data capacity per packet; With
A vehicle information system, wherein the information center includes a data capacity control unit that reduces a data capacity per packet when a data capacity reduction request is received from the in-vehicle information terminal. The vehicle information system according to claim 1,
The in-vehicle information terminal includes an electric field intensity detecting unit that detects an electric field intensity of a radio wave from the information center base station,
The communication control means constantly monitors the electric field intensity of the radio wave from the information center base station, and when the electric field intensity becomes lower than a predetermined threshold, requests the information center to reduce the data capacity per packet. Car information system characterized by performing. The vehicle information system according to claim 1 or 2,
The in-vehicle information terminal includes a BER detection unit that detects a BER (Bit Error Rate) of a communication result with the information center,
The communication control means constantly monitors a BER of a communication result with the information center, and when the BER of the communication result exceeds a predetermined threshold value, issues a data capacity reduction request per packet to the information center. An automobile information system characterized by the above-mentioned. In an in-vehicle information terminal that receives various information in packet units from an information center via a mobile phone or an in-vehicle phone,
Current position detecting means for detecting the current position of the vehicle;
Radio wave environment storage means for storing the radio wave environment degraded area of the information center base station;
Communication control means for constantly monitoring whether or not the current position of the vehicle has entered the radio wave environment degraded area, and when entering the radio wave environment degraded area, requests the information center to reduce the data capacity per packet; An in-vehicle information terminal comprising: The in-vehicle information terminal according to claim 4,
An electric field intensity detecting unit for detecting electric field intensity of a radio wave from the information center base station,
The communication control means constantly monitors the electric field intensity of the radio wave from the information center base station, and when the electric field intensity becomes lower than a predetermined threshold, requests the information center to reduce the data capacity per packet. In-vehicle information terminal characterized by performing. The in-vehicle information terminal according to claim 4 or 5,
BER detection means for detecting a BER (Bit Error Rate) of a communication result with the information center,
The communication control means constantly monitors a BER of a communication result with the information center, and when the BER of the communication result exceeds a predetermined threshold value, issues a data capacity reduction request per packet to the information center. An in-vehicle information terminal, characterized in that: In an automobile information system that performs data communication in packet units via a mobile phone or an in-vehicle phone and distributes various information from an information center to an in-vehicle information terminal,
In the in-vehicle information terminal, a current position detecting means for detecting the current position of the vehicle,
Radio wave environment storage means for storing the radio wave environment degraded area of the information center base station;
Electric field intensity detecting means for detecting the electric field intensity of the radio wave from the information center base station,
BER detection means for detecting a BER (Bit Error Rate) of a communication result with the information center;
When the current location of the vehicle enters the radio wave environment degraded area, or when the electric field intensity of the radio wave from the information center base station becomes lower than a predetermined threshold value, or a communication result with the information center When the BER exceeds a predetermined threshold, a request for reducing the data capacity per packet is made to the information center, and the electric field intensity of the radio wave from the information center base station and the information center are transmitted to the information center. Communication control means for sending the BER of the communication result with
When the information center receives a data capacity reduction request from the in-vehicle information terminal, the data per packet is determined according to the electric field strength of the radio wave from the information center base station and the BER of the communication result with the information center. An automobile information system comprising data capacity control means for reducing capacity.

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