JP2004080588A - Mobile communication system and communication method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication system for communicating with an on-vehicle station in which communication with a traveling vehicle is not affected by the surrounding land and traffic conditions and to lower costs. <P>SOLUTION: In the mobile communication system, a signal processing part 2 connected to a plurality of radio blocks 3 for which one antenna 5 and one radio equipment part 4 are paired in one set is housed in a base station 1 for radio-communicating with the on-vehicle station 8, a reception performance is improved by receiving radio waves from the on-vehicle station 8 in the plurality of radio blocks 3, interference is prevented by selecting only one radio block 3 for transmission to the on-vehicle station 8, and stable communication is provided. Also, by making the plurality of radio block parts 3 share the signal processing part 2, the costs are reduced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mobile communication system and a communication method of a mobile communication system for performing radio communication such as microwave or millimeter wave with an in-vehicle station mounted on a vehicle running on a road.
[0002]
[Prior art]
FIG. 5 is a block diagram showing an example of a configuration of a conventional mobile communication system that performs wireless communication with a vehicle-mounted station by radio. Hereinafter, the configuration and operation of a conventional mobile communication system that communicates with a vehicle-mounted station will be described with reference to FIG.
[0003]
A mobile communication system that performs wireless communication between a vehicle running on a road and a base station installed on the ground has a plurality of base stations 101 (#a to #n) installed on the road side and runs on the road. Various types of information communication are performed with the vehicle-mounted station 8 mounted on the vehicle. The base station 101 is connected to the control base station 103 via the network 6.
[0004]
Thus, transmission / reception of traffic information, transmission / reception of various service information, and the like are performed between the vehicle-mounted station 8 and the host computer on the ground.
[0005]
Each of the base stations 101 (#a to #n) processes data and signals transmitted and received in mobile communication, and a signal processing unit 201 that controls the operation of the base station 101, and data between the signal processing unit 201 And an antenna 205 for transmitting and receiving the radio wave modulated and demodulated by the radio communication unit 204.
[0006]
The radio unit 204 sends to the signal processing unit 201 a signal obtained by converting a radio wave from the vehicle-mounted station 8 received by the antenna 205 to a predetermined frequency and a monitor signal such as a reception intensity of the radio wave.
[0007]
The signal processing unit 201 demodulates the signal, generates data configured in a predetermined format, and transmits the data to the control base station 103 via the network 6 together with a monitor signal such as the reception intensity of a radio wave. Further, the control base station 103 is connected to an upper host computer or the like directly or via a network or the like.
[0008]
At the same time, the signal processing unit 201 receives a data signal transmitted from the control base station 103 to the base station 101 via the network 6, a control signal for controlling the base station 101, and the like, and transmits the data signal to the vehicle-mounted station 8. The signal is extracted and a predetermined modulation is performed.
[0009]
The radio unit 204 converts the frequency of the transmission data signal modulated by the signal processing unit 201 and transmits a radio wave from the antenna 205 to the vehicle-mounted station 8.
[0010]
Each of these base stations 101 (#a to #n) has a coverage area of a communicable area (cell), and is provided on a road so as to enable continuous communication with an on-vehicle station 8 mounted on a vehicle. It is installed on the roadside.
[0011]
These base stations 101 (#a to #n) are connected to the control base station 103 via the network 6, and correspond to the vehicle-mounted station 8 ( For example, the dominating base station 103 performs handover control on the base stations 101 (#a to #n) so that one station of the base station 101 serving as the communication partner of #a) is sequentially switched.
[0012]
This handover control operates so that communication can be continued while the vehicle-mounted station 8 sequentially moves between the coverage areas of the base stations 101 (#a to #n).
[0013]
That is, the control base station 103 monitors the signal quality of the radio wave received from the vehicle-mounted station by the base station 101 (#a to #n) at a predetermined time interval at which the vehicle can be tracked and captured, for example, the reception intensity. One of the base stations 101 (#a to #n) suitable for communication is selected by comparing the obtained data, and a control signal instructing communication is transmitted to the base station 101 (for example, #a).
[0014]
Although the details are omitted, the handover process is greatly affected by the radio wave propagation state between the vehicle-mounted station 8 and the base station 101.
[0015]
FIG. 6 is a conceptual diagram illustrating a situation in which communication quality is affected by shadowing in a conventional mobile communication system communicating with a vehicle-mounted station, using a handover process as an example. Here, a state is shown in which the base station 101 (#a, #b) is installed on the roadside, and the base station 101 (#a) is communicating with the vehicle-mounted station 8.
[0016]
Normally, a handover is performed (taken over like handing over) from the base station 101 (#a) communicating with the vehicle-mounted station 8 to (#b) in accordance with the traveling of the vehicle-mounted station 8.
[0017]
However, for example, a large vehicle 9 may enter between the base station 101 (#a) and the communicating on-vehicle station 8 and cut off the communication between the on-vehicle station 8 and the base station 101 (#a). When traveling, not only communication is interrupted, but also the in-vehicle station 8 and the base station 101 (#a) are connected again, and then a handover process is performed, or the in-vehicle station 8 is connected to the handover destination base station 101 (#a). For example, it is an irregular handover in which a wireless connection is made immediately with #b).
[0018]
In such a case, if the wireless connection between the vehicle-mounted station 8 and the base station is interrupted, there is a problem that the handover process cannot be performed correctly. Further, there is a problem that if the cutoff time becomes long, the connection is forcibly disconnected and the connection must be re-established. Further, even in a normal handover process, it must be performed frequently every time the coverage area of the antenna changes, and communication and handover with the on-vehicle station 8 during traveling are performed on the terrain and surrounding vehicles. There is a problem that it is necessary to improve that it is greatly affected by radio wave propagation caused by radio waves.
[0019]
In addition to the above, when the vehicle-mounted station 8 turns right or left at an intersection or the like, the vehicle-mounted station 8 performs handover to the base station 101 (for example, #N) to which the vehicle turns right or left. (#N) means that the wireless connection (handover) is suddenly performed, and the processing up to the connection is complicated, and there is a problem that the communication quality is deteriorated.
[0020]
[Problems to be solved by the invention]
In conventional mobile communication systems that communicate with on-board stations, communication quality is likely to deteriorate due to shadowing or turning left or right at intersections. There is a problem that is greatly affected by radio wave propagation by the vehicle and surrounding vehicles.
[0021]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and can secure stable communication without being affected by the terrain and traffic conditions around a traveling vehicle, thereby achieving a low cost mobile communication system. And a communication method for a mobile communication system.
[0022]
[Means for Solving the Problems]
In order to achieve the above object, a mobile communication system of the present invention is a mobile communication system that performs wireless communication between a plurality of base stations and an in-vehicle station mounted on a vehicle running on a road, wherein the base station and A control base station connected via a network, a plurality of radio block units provided in the base station, each of which is a set of an antenna and a radio, installed at a different position across the on-vehicle station; A signal processing unit connected to a block unit, the plurality of wireless block units simultaneously receive radio waves from the vehicle-mounted station, the signal processing unit, the signal received by the plurality of wireless block unit Processing and transmitting the signal to the control base station, and selecting one of the plurality of radio block units to transmit a signal from the control base station to the on-vehicle station.
[0023]
Also, the communication method of the mobile communication system of the present invention is a combination of an in-vehicle station mounted on a vehicle running on a road, an antenna installed on the roadside and installed at a different position across the in-vehicle station, and a radio. A communication method of a mobile communication system for performing wireless communication with a plurality of base stations having a plurality of wireless block units and a signal processing unit connected to the plurality of wireless blocks, wherein a radio wave from the vehicle-mounted station is provided. Are simultaneously received by the plurality of radio blocks of the base station, and the signals received by the plurality of radio blocks are processed by the signal processing unit of the base station and transmitted to the general base station connected via a network. Then, a signal from the control base station is transmitted to the on-vehicle station using one wireless block unit selected by the signal processing unit of the base station.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0025]
FIG. 1 is a block diagram showing a configuration of an embodiment according to the mobile communication system of the present invention.
[0026]
The mobile communication system of the present invention assumes a mobile communication system that communicates with an on-vehicle station, and includes a plurality of base stations 1 (#A to #N) having a plurality of wireless block units 3, a network 6, and a control base. Station 7 and on-vehicle station 8. Hereinafter, the configuration and functions of the mobile communication system will be described with reference to FIG.
[0027]
A mobile communication system that performs wireless communication between an on-vehicle station 8 mounted on a vehicle traveling on a road and a ground facility includes a plurality of base stations 1 (#A to #N) on both sides of the on-vehicle station. Or on the roadside and the median strip with the in-vehicle station in between, and connected to the controlling base station 7 via the network 6. Then, the control base station 7 transmits and receives data to and from the plurality of base stations 1 (#A to #N) and performs a plurality of handover controls.
[0028]
Each of the base stations 1 (#A to #N) processes data and signals transmitted and received in communication with the vehicle-mounted station 8 and controls the operation of the base station 1; It is composed of a plurality of wireless block units 3 (# 1 to #m) each having a set of antennas 5.
[0029]
That is, the base station 1 of the present invention has a configuration in which a plurality of wireless block units 3 (# 1 to #m) are connected to one signal processing unit 2, and each of the wireless block units 3 The installation locations and the coverage areas of the (i.e., the respective antennas 5) are provided, for example, on the right road side and the left road side, and are configured so that wireless communication can be performed with all vehicles traveling on the lane.
[0030]
Each of the wireless block units 3 (# 1 to #m) is connected to one signal processing unit 2 by a communication cable or an optical fiber cable, and the base station 1 (#A to #N) is connected to the network 6 Is connected to the control base station 7 via the.
[0031]
In the following description, an operation in the case where the base station 1 (for example, #A) includes two wireless block units 3 (# 1, # 2) will be described. However, the number of the wireless block units 3 is further increased. The operation of the base station 1 is the same.
[0032]
Each of the radio block units 3 (# 1 and # 2) of the base station 1 (#A) receives the radio wave from the on-vehicle station 8 by the antenna 5, and the radio unit 4 converts the signal to perform signal processing. Transmit to section 2. At the same time, the reception intensity data of the radio wave from the vehicle-mounted station 8 is transmitted to the signal processing unit 2.
[0033]
The signal processing unit 2 demodulates the signal from the radio unit 4 into a predetermined data format, and further integrates the data signal and the reception intensity data from the radio block units 3 (# 1 and # 2) via the network 6. Transmit to base station 7.
[0034]
Further, the signal processing unit 2 modulates data transmitted from the control base station 7 to the in-vehicle station 8 transferred to the base station 1 (#A), and transmits the modulated data to the radio block unit 3 (# 1 or # 2). Output.
[0035]
The radio block units 3 (# 1 and # 2) perform frequency conversion of the signals, transmit radio waves from the antenna 5 and communicate with the vehicle-mounted station 8, and at this time, the radio block units 3 (# 1 and # 2) Mutual interference occurs when radio waves are transmitted at the same time, and it is necessary to take measures against this mutual interference. Therefore, for example, transmission is performed only from one of the antennas 5 of the wireless block unit 3 (# 1 or # 2).
[0036]
That is, the signal processing unit 2 compares the reception intensity data from the radio block units 3 (# 1 and # 2) and demodulates the signal from the radio block unit 3 (here, for example, # 1) with the higher reception intensity. The transmitted data is transmitted to the control base station 7 via the network.
[0037]
Then, the signal processing unit 2 selects the radio block unit 3 (# 1) having the stronger reception strength for radio wave transmission, and transmits the data to be transmitted to the on-vehicle station 8 transmitted from the control base station 7 to the base station 1. Is modulated and output to the radio block unit 3 (# 1).
[0038]
The wireless block unit 3 (# 1) converts the signal into a predetermined frequency, transmits radio waves from the antenna 5, and communicates with the vehicle-mounted station 8.
[0039]
In this way, even if a plurality of radio block units 3 (# 1 and # 2) are present in one base station 1, the radio block unit 3 (# 1 or # 2) that transmits the radio block unit 3 (# 1 or # 2) may be one according to the reception strength. Since one is selected, radio interference can be prevented.
[0040]
In addition, the signal processing unit 2 may perform processing for improving the signal quality of the received signal by performing the diversity processing while comparing the reception intensity data from the wireless block units 3 (# 1 and # 2). For example, the reception intensities of the reception signals of both the radio blocks 3 (# 1 and # 2) are averaged and demodulated to a baseband signal to reduce the fluctuation difference in the reception intensity.
[0041]
Then, the signal processing unit 2 transmits the data transmitted from the control base station 7 to the on-vehicle station 8 transferred to the base station 1 (#A) to the wireless block (# 1 in the above example) having the higher reception strength. I do.
[0042]
In the above example, the selection method of transmitting the wireless block unit 3 (# 1 in the above example) having a high reception strength by comparing the evaluation parameters of the signal quality using the reception strength is shown. The radio block 3 (for example, # 1) used for transmission is evaluated based on the result (for example, having the lowest error rate) of the parameter evaluated by means for comparing parameters (for example, signal error rate) appropriate for system operation. You may choose.
[0043]
When a means for comparing error rates is used to select a radio block unit, the signal processing unit 2 monitors and compares signals from the radio blocks 3 (# 1 and # 2) at a fixed timing. Then, the signal processing unit 2 extracts a baseband signal from the wireless block 3 having a small error rate (for example, # 1 when there is one, and # 2 at the next timing), and converts the stable data with the smallest error rate fluctuation into a network. 6 may be performed to output the information to the controlling base station 7.
[0044]
As described above, in the base station 1 accommodating the plurality of radio block units 3, the signal processing unit 1 compares the reception intensities of the radio block units 3 (# 1 to #m), and among them, The radio block unit 3 (# 1 in the above example) having a strong error rate is selected, or the error rate is compared and transmitted using the radio block unit 3 (# 1) with the lowest error rate. Stable communication is enabled even with the fluctuation of the generated radio wave propagation.
[0045]
On the other hand, as a method of selecting one of the wireless block units 3, the transmission timing of the plurality of wireless block units 3 (# 1 and # 2) is set so that interference due to simultaneous transmission by a plurality of transmitters does not occur. There is a method of switching and transmitting the block units 3 (# 1 and # 2) according to their transmission timing.
[0046]
In the on-vehicle station 8, even if the line-of-sight communication with one wireless block unit 3 (# 1) is blocked by another vehicle, the other wireless block unit 3 (# 2) is installed so that the vehicle is not blocked. Communication with the wireless block unit 3 (# 2). Therefore, communication with the base station 1 can always be continued.
[0047]
According to this method, the communication control is easier because the base station 1 does not need to compare the quality of the signal received from the vehicle-mounted station 8 as compared with the method using the reception intensity.
[0048]
In the mobile communication system according to the present invention, as described above, a plurality of radio block units 3 (# 1 to #m) accommodated in one base station 1 determine optimum communication conditions (determined as best). A method of selecting the wireless block unit 3 (for example, # 1) that can obtain the signal quality) by its own judgment, or switching the wireless block units 3 (# 1 to #m) periodically with a timing to establish communication with the vehicle-mounted station 8 The communication method avoids the influence of radio wave propagation such as vehicle congestion and terrain around the vehicle-mounted station 8.
[0049]
Accordingly, the communication range (that is, the coverage area) covered by one base station 1 is wider and continuous than that of a conventional mobile communication system that communicates with a vehicle-mounted station.
[0050]
Further, since the configuration is such that a plurality of wireless block units 3 (# 1 to #m) are shared by one signal processing unit 2, the apparatus cost is reduced.
[0051]
FIG. 2 shows the mobile communication system according to the present invention, in which the radio block units 3 (# 1 and # 2) are installed on the roadside and the median strip of the road. Will be described.
[0052]
In FIG. 2, the base station 1 (#A) includes two radio block units 3 (# 1, # 2), the radio block unit 3 (# 1) is on the sidewalk side, and (# 2) is on the center divider side. Here, it is assumed that the wireless block unit 3 (# 1) is communicating with the vehicle-mounted station 8.
[0053]
At this time, if the communication between the in-vehicle station 8 and the antenna 5 of the wireless block unit 3 (# 1) is blocked by the intrusion of the large vehicle 9 traveling on the same road, the in-vehicle station 8 cannot communicate.
[0054]
Therefore, in the present invention, since the wireless block units 3 (# 2) installed on the side of the central divider that can secure communication with the vehicle-mounted station 8 are alternately switched and transmitted, the wireless block units 3 (# 2) Communication can be continued.
[0055]
FIG. 3 shows a configuration in the case where the present invention is applied to a base station installed at an intersection, and a handover process in FIG. 3 will be described.
[0056]
In FIG. 3, it is assumed that the vehicle-mounted station 8 is traveling upward in the figure. The base station 1 (#B) has a signal processing unit 2, a radio block unit 3 (# 4) in the straight traveling direction of the vehicle-mounted station 8, a radio block unit 3 (# 5) at the left turn, and a radio block unit at the right turn. 3 (# 6) and three wireless block units 3.
[0057]
The area covered by the antenna of each wireless block unit 3 (# 4 to # 6) is the range indicated by C4, C5, and C6.
[0058]
According to the present invention, even when the vehicle-mounted station 8 turns right or left, each wireless block unit 3 (# 4 to # 6) of the base station 1 (#B) takes a timing and periodically switches to transmit. There is an advantage that the communication with the base station 1 (#B) is continued immediately after the right or left turn, and the handover is smoothly performed to the base station 1 (#N) immediately after the right or left turn.
[0059]
In FIG. 3, the radio block units 3 (# 4, # 5, # 6) are configured to be included in the base station 1 (#B). The configuration of the station 1 may be shared.
[0060]
In FIG. 4, the radio block units 3 (# 4, # 5, # 6) are in the base station 1 (#B), and the radio block units 3 (# 5, # 6, # 7) are in the base station 1 (#C). ), And the wireless block unit 3 (# 5 and # 6) is shared by the two base stations 1 (#B and #C). In this case, the handover process of the control base station 7 is performed. Becomes easier.
[0061]
【The invention's effect】
According to the mobile communication system of the present invention, as described above, the base station has a plurality of radio block sections, and the plurality of radio block sections are sequentially switched for transmission or reception by the plurality of radio block sections. The effect of shadowing is reduced, continuous communication is enabled, and stable wireless communication with the in-vehicle station can be secured.
[0062]
In addition, since one signal processing unit is shared by a plurality of wireless block units, control of a mobile communication system that communicates with a vehicle-mounted station can be facilitated and cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of a configuration of an embodiment according to a mobile communication system of the present invention.
FIG. 2 is a diagram illustrating an example of an operation in which a base station is installed along a road in the mobile communication system of the present invention.
FIG. 3 is a diagram illustrating an example of an operation of installing a base station at an intersection in the mobile communication system of the present invention.
FIG. 4 is a block diagram showing an example in which a mobile communication system according to the present invention in which a radio block unit is shared by a plurality of base stations is installed at an intersection.
FIG. 5 is a block diagram showing an example of a configuration of a conventional mobile communication system.
FIG. 6 is a view for explaining an example of the influence of shadowing on communication quality in a conventional mobile communication system.
[Explanation of symbols]
Reference Signs List 1 base station 2 signal processing unit 3 radio block unit 4 radio unit 5 antenna 6 network 7 supervising base station 8 on-board station 9 large vehicle

Claims (9)

In a mobile communication system that performs wireless communication between a base station and an in-vehicle station mounted on a vehicle traveling on a road,
A controlling base station connected to the base station via a network,
The base station includes a plurality of radio block units, each of which is a set of an antenna and a radio, installed at a different position across the on-vehicle station, and a signal processing unit connected to the plurality of radio block units. And
The plurality of radio block units simultaneously receive radio waves from the vehicle-mounted station,
The signal processing unit processes a signal received by the plurality of radio block units and transmits the signal to the control base station, and selects one of the plurality of radio block units to output a signal from the control base station. A mobile communication system for transmitting to an in-vehicle station. The signal processing unit compares the signal quality of radio waves received from the vehicle-mounted station in the plurality of wireless block units,
2. The wireless communication device according to claim 1, wherein one of the plurality of wireless block units, which is determined to be the best among the signal qualities of the received radio waves, is selected and used for transmission to the vehicle-mounted station. A mobile communication system according to claim 1. The signal processing unit compares the reception intensity of radio waves from the vehicle-mounted station in the plurality of wireless block units,
The mobile communication system according to claim 2, wherein a radio block unit having the highest reception strength is selected from the plurality of radio block units. The signal processing unit compares the error rate of the radio wave signal from the vehicle-mounted station in each of the plurality of wireless block units,
The mobile communication system according to claim 2, wherein a radio block unit having the lowest error rate is selected from the plurality of radio block units. 2. The mobile communication system according to claim 1, wherein the plurality of wireless block units sequentially transmit data from the signal processing unit to the on-vehicle station in accordance with respective set time timings. 3. 2. The mobile station according to claim 1, wherein the plurality of wireless block units sequentially transmit data from the signal processing unit to the on-vehicle station according to transmission timings having a predetermined period set respectively. Communications system. The mobile communication system according to claim 1, wherein the base station communicating with the on-vehicle station performs diversity processing on signals received from the on-vehicle station in the plurality of radio block units. The mobile station according to claim 1, wherein at least one of the plurality of radio block units accommodated in the first base station constitutes a second radio block unit of the base station. Communications system. An in-vehicle station mounted on a vehicle traveling on a road, a plurality of radio block units each including a pair of antennas and radios installed at different positions across the in-vehicle station, and signals connected to the plurality of radio blocks A communication method of a mobile communication system for performing wireless communication with a plurality of base stations having a processing unit, wherein the radio waves from the in-vehicle station are simultaneously received by a plurality of wireless blocks of the base station,
The signals received by the plurality of radio blocks are processed by the signal processing unit of the base station, and transmitted to the general base station connected via a network,
A communication method for a mobile communication system, comprising: transmitting a signal from the control base station to the on-vehicle station by using one radio block unit selected by the signal processing unit of the base station.

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