JP3584291B2

JP3584291B2 - Road-to-vehicle communication system

Info

Publication number: JP3584291B2
Application number: JP2002092110A
Authority: JP
Inventors: 雅人前田
Original assignee: National Institute for Land and Infrastructure Management
Current assignee: National Institute for Land and Infrastructure Management
Priority date: 2002-03-28
Filing date: 2002-03-28
Publication date: 2004-11-04
Anticipated expiration: 2022-03-28
Also published as: JP2003289582A

Description

【０００１】
【発明の属する技術分野】
この発明は、移動体通信方式としての路車間通信方式に関し、特に、道路に沿って設置された狭域無線通信方式（ＤＳＲＣ，ＤｅｄｉｃａｔｅｄＳｈｏｒｔＲａｎｇｅＣｏｍｍｕｎｉｃａｔｉｏｎｓ）による基地局と道路上を高速移動する移動局との間の路車間通信方式（以下、ＤＳＲＣ路車間通信方式と称する）に関するものである。
【０００２】
【従来の技術】
従来の狭域無線通信方式の通信機器は性能の向上を重視するために無線規格（ＡＲＩＢＳＴＤ−Ｔ５５）に規定された受信感度規定等の性能条件の上限を実現する傾向にあり、その結果、通信すべきでない場所への電波の飛びすぎがみられる。また、携帯電話の例では移動端末の送信出力を制御することで通信の信頼性を向上させている。
【０００３】
しかしながら、上述した従来のシステムで採用している通信制御方式では、ＤＳＲＣ路車間通信方式によって情報通信領域を道路に沿って小領域が並ぶ形態もしくは帯状に連なる形態に設定し、それぞれの情報通信領域毎に異なった地域性の高い情報を提供する高速移動体通信システムに適用する場合、次のような問題がある。
【０００４】
第１の問題点は、図５に示すように、基地局１０は道路８上を走行する移動局１００と通信領域Ａ１の中で確実に通信を行うように設定されている場合に、その外側にも、例えば通信領域Ｎ３の範囲で電波は弱くなるが漏れ出ており、隣接道路８１を移動中の移動局１０１は通信すべきでないにもかかわらず移動局１０１の通信機の性能によっては基地局１０の電波を受信して通信が成立してしまうことである。誤った通信を防ぐために基地局１０の送信電波を弱くすると通信領域Ａ１で移動局１００の受信レベルが下がり移動局１００の通信品質が確保できなくなるという問題が生じる。
【０００５】
第２の問題点は、ＤＳＲＣ路車間通信方式の特徴を活かして、無線通信によって移動局の位置を特定する場合に、図６に示すように、移動局の通信機の性能の違いによって誤差が生じることである。基地局１０から送出した電波は道路８上を伝搬するときの電界強度は一般的に図６の３００のようになっている。移動局１００の通信機の性能が図６の３２０のレベルより高いレベルで通信可能の場合は、移動局１００が図６の３２１の地点から３２２の地点の間にあるときに通信が可能であり、移動局は最初に通信が可能になった３２１の地点を位置情報として取得する。
【０００６】
一方、移動局１００の通信機の性能が図６の３１０のレベルより高いレベルで通信可能の場合は、移動局１００が図６の３１１の地点から３１２の地点の間にあるとき、および３１３の地点から３１４の地点の間にあるときに通信が可能であり、移動局は最初に通信が可能になった３１１の地点を位置情報として取得する。このように移動局の通信機の性能によって取得した位置情報と通信地点の間に誤差が出ることである。
【０００７】
【発明が解決しようとする課題】
そこでこの発明は、前記のような従来の問題点を解決し、高品質の路車間通信を確保することができ、電波の飛びすぎによって生じる、望まない路車間通信を防止することができ、ＤＳＲＣ路車間通信方式によって移動局の位置を特定する際に移動局の通信機の性能の違いによって生じる誤差を減少させることができる路車間通信方式を提供することを目的とする。
【０００８】
前記目的を達成するため、請求項１に記載の発明は、狭域無線通信方式を用いて基地局と移動局間の通信が双方向通信及び基地局から移動局への単方向通信で行われる路車間通信方式において、基地局と移動局間の通信が双方向通信で行われる場合においては、基地局は移動局が送信した電波の受信強度を監視し、該電波の受信強度が予め設定した判定基準値以上の場合に、基地局が移動局との双方向通信を成立させるとともに、基地局と移動局間の通信が双方向通信と基地局から移動局への単方向通信とで行われる場合においては、移動局は、前記双方向通信が成立したときの受信レベルを記憶し、基地局からの単方向通信の受信レベルが前記記憶された受信レベル以上である場合に、前記基地局からの単方向通信の受信を有効とすることを特徴とする。
【０００９】
【発明の実施の形態】
次に、本発明の実施の形態について図面を参照して詳細に説明する。
図１および図２は、実施の形態として通信領域を基地局の受信レベルの設定で可変にできる高信頼ＤＳＲＣ路車間通信方式を示した図である。
【００１０】
図１および図２において、道路８上に走行する移動局１００は進行方向９へ進むものとする。路側に設置された基地局１０は空中線１１と基地局空中線の送受信の切り替え機能または多重分離機能１２と双方向通信機能２１と受信レベル監視機能３１と受信レベル判定機能３２から構成され、移動局１００は移動局空中線１１１と移動局空中線の送受信の切り替え機能または多重分離機能１１２と双方向通信機能１２１と受信判定機能（１）１３１−１から構成される。基地局１０が空中線１１を介して放射する電波は道路８上に向けられており、移動局１００との間で通信を行うが、通信が可能になる領域を通信領域として、通信領域Ａ、通信領域Ｂ、・・・通信領域Ｎとする。
【００１１】
通信領域を変化させる手段として基地局の受信レベル監視機能３１と受信レベル判定機能３２によって移動局１００が空中線１１１を介して送信した電波を基地局１０が空中線１１を介して受信し、基地局１０は受信レベル監視機能３１においてその受信レベルを監視し、受信レベル判定機能３２において基準値以上の受信レベルであると判定した場合に基地局１０が移動局１００に対し応答することによって移動局１００が通信可能になる通信領域が設定されるようにする。本発明は受信レベル判定機能３２における基準値を変化させることによって移動局１００との通信領域の大きさを変化させることを可能にする。
【００１２】
図３は、図２の基地局１０および移動局１００の構成を基本として基地局１０から移動局１００への単方向通信機能を加えた場合の構成を示した図である。基地局１０においては単方向送信機能２２を加え、移動局１００においては単方向受信機能１２２と受信レベル監視記憶機能１３２を加え、受信判定機能（１）を受信判定機能（２）１３１−２に換えた構成である。単方向通信において移動局の受信情報を有効とする条件として双方向通信の成立を適用する。移動局において単方向通信の受信を有効とする判定条件として双方向通信が成立したときの受信レベルを受信レベル監視記憶機能１３２に記憶し、単方向通信の受信レベルが記憶した受信レベル以上であることを受信判定機能（２）１３１−２において判定し単方向通信の受信が有効であることを判定することで単方向通信の通信品質を確保することを特長としている。
【００１３】
次に、高信頼ＤＳＲＣ路車間通信方式の実施の形態の動作を説明する。基地局の受信レベルを調整することで移動局の受信レベルを基地局側が期待するレベルに調整することができる理由は、基地局の送信機の出力レベルをＰｂとし、基地局の受信機の入力レベルをＲｂ（基地局の受信機の受信感度より高いレベルであること）とし、移動局の送信機の出力レベルをＰｍとし、移動局の受信機の入力レベルをＲｍ（移動局の受信機の受信感度より高いレベルであること）とした場合、Ｐｂ＋Ｒｂ＝Ｐｍ＋Ｒｍの関係が成立し、Ｐｂがある一定値をとり、Ｐｍが移動局ごとに差異があるもののある範囲の一定値をとるとした場合に、Ｒｂの値を調整すればＲｍの値はＲｂに応じて一定の範囲の値に調整されるということに基づいている。
【００１４】
先ず、基地局と移動局間の双方向通信の高信頼性ＤＳＲＣ路車間通信方式の実施の形態について動作を説明する。
【００１５】
図１および図２において、移動局１００が道路８を進行方向９の方向に進むものとする。道路８の路側に基地局１０が設置され移動局１００との通信のために道路８に向けて電波を発射しているものとする。移動局１００は道路８を進行中に基地局１０の電波を受信する。この時の移動局１００が受信可能になる位置は基地局１０が発射する電波の強度と移動局１００の受信機の受信性能に依存し、移動局の製造業者や機種によって異なったものとなる。例えば、移動局１００が通信領域Ｎ３に入ったときに移動局１００の受信機が受信できたとする。移動局１００は基地局１０と双方向通信を開始するために基地局１０に向けて電波を放射する。基地局１０は移動局１０が放射した電波を受信し、受信レベル監視機能３１により移動局が放射した電波の強度を測定する。
【００１６】
基地局１０の受信レベル判定機能３２は通信領域Ａ１、通信領域Ｂ２、・・・通信領域Ｎ３に対応する値が予め設定されるものとする。例えば、通信領域Ａ１に対応する値が設定されているとすると、この位置にある移動局１００からの受信電力は値を満たさないため、基地局１０の受信レベル判定機能３２は双方向通信機能２１を介して移動局１００の通信開始要求に対して否定的な回答を行う。または、無視し回答を返さない。移動局１００は基地局１０に対して繰り返し通信開始の要求を行い、移動局１００が道路を進んで通信領域Ａ１の中に入った場合には基地局１０の受信レベル監視機能３１の出力は通信領域Ａ１に対応する値になり、受信レベル判定機能３２は通信の開始を許諾する。移動局は受信判定機能（１）１３１−１は基地局１０からの許諾を受信して双方向通信の成立を判断する。
【００１７】
次に、基地局から移動局への単方向通信の高信頼性ＤＳＲＣ路車間通信方式の実施の形態について動作を説明する。
【００１８】
図３は、基地局１０においては、前記図２の構成の中に単方向送信機能２２が加わる構成となる。移動局１００においては、前記図２の移動局の構成の中に単方向受信機能１２２が加わり、移動局の受信判定が受信判定機能（２）１３１−２に換わる。
受信判定機能（２）１３１−２は、基地局１０と移動局１００の間の通信が双方向通信と基地局から移動局への単方向通信とで行われる場合において、移動局１００は単方向通信の有効性を判定する機能を有する。移動局１００は前記図２の成立条件が維持されていることを確認する目的として移動局１００で双方向通信が成立したときの受信レベルを受信レベル監視記憶機能１３２において記憶し、受信判定機能（２）１３１−２は単方向通信の受信レベルが受信レベル監視記憶機能１３２で記憶した受信レベル以上であることを判定して有効とする。
【００１９】
単方向通信において移動局の受信情報を有効とする条件として双方向通信の成立を適用する発明の他の実施の形態として、双方向通信機能を介して基地局と移動局間で周期的に通信要求応答を繰り返す例を示す。図４を参照すると、基地局１０においては、前記図３の構成の中に周期的通信要求応答機能３３が加わる構成となる。移動局１００においては、前記図３の移動局の構成の受信レベル監視記憶機能が不要であり、受信判定機能（２）１３１−２が受信判定機能（３）１３１−３に換わる。図４は周期的通信要求応答機能３３を基地局１０の中に設けた一例を示している。周期的通信要求応答機能３３は、基地局になく移動局の中に設けても良く、基地局および移動局の双方に設けても良い。
【００２０】
移動局の受信判定機能（３）１３１−３は、基地局と移動局間の通信が双方向通信と基地局から移動局への単方向通信とで行われる場合において、移動局１００は単方向通信の有効性を判定する機能を有する。基地局１０の周期的通信要求応答機能３３が双方向通信機能２１を介して移動局１００の双方向通信機能１２１と通信を行う。この通信が基地局１０の受信レベル監視機能３１と受信レベル判定機能３２で条件に合致している間は双方向通信が繰り返されることになる。移動局１００ではこの双方向通信が続いている間の単方向通信の受信を有効とするように受信判定機能（３）１３１−３が働く。これにより図３の移動局１００の受信レベル監視記憶機能１３２が不要になる。
【００２１】
【発明の効果】
以上説明したように、請求項１に記載の発明によれば、基地局側で移動局の通信領域の調整が可能になることにより、移動局の通信機の性能の違いによる通信領域の大きさの違いを抑えることができるため、通信領域を所定の電波強度以上に保つことによって通信品質の維持が可能になり、電波の飛びすぎによって隣接地の受信すべきでない場所で通信が成立してしまう問題を解決することができる。また、基地局と移動局間の通信品質が良好に維持できる。また、電波の飛びすぎを基地局の送信レベルを下げることによる電波伝搬距離の調整を行う場合と比べ、基地局の送信レベルの変化がないため、移動局の受信レベルは変わらず通信品質の劣化がない。また、基地局側で細かな通信領域の調整が可能になることにより、移動局の受信機の感度に依存することないため、基地局側で細かな通信領域の調整が可能になることにより、狭域無線通信によって移動局の位置を特定する際に移動局の通信機の性能の違いによって生じる誤差を減少させることができる。
【００２３】
以上の効果により、電波の飛びすぎによって隣接地の受信すべきでない場所で通信が成立してしまう問題を解決することができる。また、基地局と移動局間の通信品質が良好に維持できる。ＤＳＲＣ路車間通信方式を利用した移動局の位置の特定において誤差を減すことができる。
【図面の簡単な説明】
【図１】この発明の一実施の形態における高信頼ＤＳＲＣ路車間通信方式を道路上で適用した例で示す概略図である。
【図２】高信頼性ＤＳＲＣ路車間通信方式を双方向通信機能を有する基地局および移動局に適用した場合の構成例を示す概略図である。
【図３】高信頼性ＤＳＲＣ路車間通信方式を双方向通信機能および基地局から移動局への単方向通信機能を有する基地局および移動局に適用した場合として受信レベル記憶機能を含む構成例を示す概略図である。
【図４】高信頼性ＤＳＲＣ路車間通信方式を双方向通信機能および基地局から移動局への単方向通信機能を有する基地局および移動局に適用した場合として周期的通信要求応答機能を含む構成例を示す概略図である。
【図５】電波の飛びすぎによって通信すべきでない道路上を走行する移動局と誤って通信が発生する場合の例を示す概略図である。
【図６】移動局の性能の違いによる通信開始位置の違いを説明する概略図である。
【符号の説明】
１通信領域Ａ
２通信領域Ｂ
３通信領域Ｎ
８道路
９移動局の進行方向
１０基地局
１１基地局空中線
８１道路８の隣接道路
１００移動局
１０１通信すべきでない道路上を走行する移動局
１１１移動局空中線[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a road-to-vehicle communication system as a mobile communication system, and more particularly, to a base station and a mobile station that moves at high speed on a road by a short-range wireless communication system (DSRC, Dedicated Short Range Communications) installed along a road. (Hereinafter, referred to as DSRC road-vehicle communication system).
[0002]
[Prior art]
Conventional narrow-area wireless communication system communication devices tend to realize the upper limit of performance conditions such as the reception sensitivity specification defined in the wireless standard (ARIB STD-T55) in order to emphasize performance improvement. Radio waves jump too far to places that should not communicate. Further, in the example of a mobile phone, the reliability of communication is improved by controlling the transmission output of the mobile terminal.
[0003]
However, according to the communication control method adopted in the above-described conventional system, the information communication area is set to a form in which small areas are arranged along a road or a form in which the information communication area is continuous in a belt shape by the DSRC road-to-vehicle communication method. When the present invention is applied to a high-speed mobile communication system that provides information having high regional characteristics, the following problems arise.
[0004]
The first problem is that, as shown in FIG. 5, when the base station 10 is set to reliably communicate with the mobile station 100 traveling on the road 8 within the communication area A1, the base station 10 Also, for example, the radio wave is weakened but leaks in the range of the communication area N3, and depending on the performance of the communication device of the mobile station 101, the mobile station 101 moving on the adjacent road 81 should not communicate. The communication is established by receiving the radio wave of the station 10. If the transmission radio wave of the base station 10 is weakened to prevent erroneous communication, the reception level of the mobile station 100 decreases in the communication area A1, and the communication quality of the mobile station 100 cannot be ensured.
[0005]
The second problem is that when the position of the mobile station is specified by wireless communication by utilizing the features of the DSRC road-vehicle communication system, an error occurs due to the difference in the performance of the communication device of the mobile station as shown in FIG. Is to happen. The electric field intensity when the radio wave transmitted from the base station 10 propagates on the road 8 is generally as shown by 300 in FIG. When the performance of the communication device of the mobile station 100 is communicable at a level higher than the level of 320 in FIG. 6, communication is possible when the mobile station 100 is between the points 321 and 322 in FIG. , The mobile station first obtains, as position information, the point 321 at which communication became possible.
[0006]
On the other hand, when the performance of the communication device of the mobile station 100 is communicable at a level higher than the level of 310 in FIG. 6, when the mobile station 100 is between the point 311 and the point 312 in FIG. Communication is possible when the point is between the point 314 and the point, and the mobile station obtains, as position information, the point 311 at which the communication is possible first. As described above, an error occurs between the acquired location information and the communication point due to the performance of the communication device of the mobile station.
[0007]
[Problems to be solved by the invention]
Therefore, the present invention solves the conventional problems as described above, can ensure high-quality road-vehicle communication, and can prevent unwanted road-vehicle communication caused by excessive radio wave jump. It is an object of the present invention to provide a road-vehicle communication system capable of reducing an error caused by a difference in performance of a communication device of a mobile station when a position of a mobile station is specified by the road-vehicle communication system.
[0008]
In order to achieve the above object, according to the present invention, communication between a base station and a mobile station is performed by two-way communication and one- way communication from the base station to the mobile station using a short-range wireless communication system. Te road-vehicle communication system odor, when the communication between the base station and the mobile station is performed in two-way communication, the base station monitors the reception intensity of the radio wave that the mobile station has transmitted, sets the reception intensity of the radio wave in advance If the above determination reference value, together with the base station to establish a two-way communication with a mobile station, the line between the one-way communication to a mobile station communication between base station and mobile station from two-way communication with the base station In this case, the mobile station stores the reception level when the bidirectional communication is established, and when the reception level of the one-way communication from the base station is equal to or higher than the stored reception level, the base station to validate the reception of one-way communication from And it features.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 and FIG. 2 are diagrams showing a highly reliable DSRC road-vehicle communication system in which a communication area can be changed by setting a reception level of a base station as an embodiment.
[0010]
1 and 2, it is assumed that a mobile station 100 traveling on a road 8 travels in a traveling direction 9. The base station 10 installed on the road side is composed of an antenna 11 and a function of switching between transmission and reception of the base station antenna or a demultiplexing function 12, a two-way communication function 21, a reception level monitoring function 31, and a reception level determination function 32. Is composed of a function for switching transmission / reception between the mobile station antenna 111 and the mobile station antenna or a demultiplexing function 112, a two-way communication function 121, and a reception determination function (1) 131-1. Radio waves emitted by the base station 10 via the antenna 11 are directed on the road 8 and communicate with the mobile station 100. The communication area A is defined as an area where communication is possible. Area B,... Communication area N.
[0011]
As means for changing the communication area, the base station 10 receives the radio wave transmitted by the mobile station 100 via the antenna 111 by the reception level monitoring function 31 and the reception level determination function 32 of the base station, and the base station 10 The base station 10 responds to the mobile station 100 when the reception level monitoring function 31 monitors the reception level and the reception level determination function 32 determines that the reception level is equal to or higher than the reference value. A communication area that enables communication is set. The present invention makes it possible to change the size of the communication area with the mobile station 100 by changing the reference value in the reception level determination function 32.
[0012]
FIG. 3 is a diagram illustrating a configuration in which a one-way communication function from the base station 10 to the mobile station 100 is added based on the configurations of the base station 10 and the mobile station 100 in FIG. In the base station 10, a one-way transmission function 22 is added, and in the mobile station 100, a one-way reception function 122 and a reception level monitoring storage function 132 are added, and the reception determination function (1) is changed to the reception determination function (2) 131-2. This is a changed configuration. The establishment of two-way communication is applied as a condition for making the received information of the mobile station valid in one-way communication. The reception level when the bidirectional communication is established is stored in the reception level monitoring storage function 132 as a determination condition for enabling the reception of the one-way communication in the mobile station, and the reception level of the one-way communication is equal to or higher than the stored reception level. That is, the reception determination function (2) 131-2 determines that the reception of the one-way communication is valid, thereby ensuring the communication quality of the one-way communication.
[0013]
Next, the operation of the embodiment of the highly reliable DSRC road-vehicle communication system will be described. The reason that the reception level of the mobile station can be adjusted to the level expected by the base station by adjusting the reception level of the base station is that the output level of the transmitter of the base station is Pb and the input level of the receiver of the base station is Pb. The level is Rb (which is higher than the receiving sensitivity of the base station receiver), the output level of the transmitter of the mobile station is Pm, and the input level of the receiver of the mobile station is Rm (of the receiver of the mobile station). If the level is higher than the receiving sensitivity), the relationship of Pb + Rb = Pm + Rm is established, and Pb takes a certain value, and Pm takes a certain value in a certain range although there is a difference for each mobile station. In addition, it is based on the fact that if the value of Rb is adjusted, the value of Rm is adjusted to a value within a certain range according to Rb.
[0014]
First, the operation of the embodiment of the highly reliable DSRC road-vehicle communication system for bidirectional communication between the base station and the mobile station will be described.
[0015]
1 and 2, it is assumed that the mobile station 100 travels on the road 8 in the traveling direction 9. It is assumed that the base station 10 is installed on the road side of the road 8 and emits radio waves toward the road 8 for communication with the mobile station 100. The mobile station 100 receives radio waves from the base station 10 while traveling on the road 8. The position at which the mobile station 100 can receive data at this time depends on the intensity of radio waves emitted from the base station 10 and the reception performance of the receiver of the mobile station 100, and differs depending on the manufacturer and model of the mobile station. For example, suppose that the receiver of the mobile station 100 was able to receive when the mobile station 100 entered the communication area N3. The mobile station 100 emits radio waves toward the base station 10 to start bidirectional communication with the base station 10. The base station 10 receives the radio wave radiated by the mobile station 10 and measures the intensity of the radio wave radiated by the mobile station by the reception level monitoring function 31.
[0016]
In the reception level determination function 32 of the base station 10, values corresponding to the communication area A1, the communication area B2,..., The communication area N3 are set in advance. For example, if a value corresponding to the communication area A1 is set, the received power from the mobile station 100 at this position does not satisfy the value, so the reception level determination function 32 of the base station 10 A negative response is made to the communication start request of the mobile station 100 via the. Or, ignore it and return no answer. The mobile station 100 repeatedly requests the base station 10 to start communication. When the mobile station 100 travels on the road and enters the communication area A1, the output of the reception level monitoring function 31 of the base station 10 indicates the communication. The value becomes the value corresponding to the area A1, and the reception level determination function 32 permits the start of communication. In the mobile station, the reception determination function (1) 131-1 receives a license from the base station 10 and determines establishment of two-way communication.
[0017]
Next, the operation of the embodiment of the highly reliable DSRC road-to-vehicle communication system for one-way communication from the base station to the mobile station will be described.
[0018]
FIG. 3 shows a configuration in which a one-way transmission function 22 is added to the configuration of FIG. 2 in the base station 10. In the mobile station 100, a one-way reception function 122 is added to the configuration of the mobile station in FIG. 2, and the reception determination of the mobile station is replaced with the reception determination function (2) 131-2.
When the communication between the base station 10 and the mobile station 100 is performed by two-way communication and one-way communication from the base station to the mobile station, the reception determination function (2) 131-2 performs the unidirectional communication. It has a function to determine the validity of communication. The mobile station 100 stores a reception level when bidirectional communication is established in the mobile station 100 in a reception level monitoring storage function 132 for the purpose of confirming that the establishment condition of FIG. 2 is maintained, and a reception determination function ( 2) 131-2 determines that the reception level of the one-way communication is equal to or higher than the reception level stored by the reception level monitoring and storage function 132, and makes it valid.
[0019]
In another embodiment of the invention in which the establishment of bidirectional communication is applied as a condition for validating received information of a mobile station in one-way communication, periodic communication between a base station and a mobile station via a bidirectional communication function is performed. An example of repeating a request response is shown. Referring to FIG. 4, the base station 10 has a configuration in which a periodic communication request response function 33 is added to the configuration of FIG. In the mobile station 100, the reception level monitoring and storage function of the configuration of the mobile station in FIG. 3 is unnecessary, and the reception determination function (2) 131-2 is replaced by the reception determination function (3) 131-3. FIG. 4 shows an example in which the periodic communication request response function 33 is provided in the base station 10. The periodic communication request response function 33 may be provided in the mobile station, not in the base station, or may be provided in both the base station and the mobile station.
[0020]
The reception determination function (3) 131-3 of the mobile station indicates that when the communication between the base station and the mobile station is performed by two-way communication and one-way communication from the base station to the mobile station, the mobile station 100 performs the unidirectional communication. It has a function to determine the validity of communication. The periodic communication request response function 33 of the base station 10 communicates with the bidirectional communication function 121 of the mobile station 100 via the bidirectional communication function 21. While this communication meets the conditions by the reception level monitoring function 31 and the reception level determination function 32 of the base station 10, the two-way communication is repeated. In the mobile station 100, the reception determination function (3) 131-3 operates so as to validate the reception of the one-way communication while the two-way communication is continued. This eliminates the need for the reception level monitoring and storage function 132 of the mobile station 100 in FIG.
[0021]
【The invention's effect】
As described above, according to the first aspect of the present invention, since the communication area of the mobile station can be adjusted on the base station side, the size of the communication area due to the difference in the performance of the communication device of the mobile station can be improved. The communication quality can be maintained by maintaining the communication area at a predetermined radio wave intensity or higher, and communication is established in an adjacent place where reception should not be performed due to excessive radio waves. Can solve the problem. Also, good communication quality between the base station and the mobile station can be maintained. Also, compared to the case where the radio wave propagation distance is adjusted by lowering the transmission level of the base station for excessive radio wave skipping, the transmission level of the base station does not change, so that the reception level of the mobile station does not change and the communication quality deteriorates. There is no. Also, by enabling fine adjustment of the communication area on the base station side, because it does not depend on the sensitivity of the receiver of the mobile station, by enabling fine adjustment of the communication area on the base station side, When the position of the mobile station is specified by the short-range wireless communication, an error caused by a difference in the performance of the communication device of the mobile station can be reduced.
[0023]
With the above effects, it is possible to solve the problem that communication is established in a place where reception should not be performed in an adjacent place due to excessive jumping of radio waves. Also, good communication quality between the base station and the mobile station can be maintained. An error can be reduced in specifying the position of the mobile station using the DSRC road-vehicle communication method.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example in which a highly reliable DSRC road-to-vehicle communication system according to an embodiment of the present invention is applied on a road.
FIG. 2 is a schematic diagram showing a configuration example when a highly reliable DSRC road-vehicle communication system is applied to a base station and a mobile station having a two-way communication function.
FIG. 3 shows a configuration example including a reception level storage function as a case where the highly reliable DSRC road-vehicle communication system is applied to a base station and a mobile station having a two-way communication function and a one-way communication function from the base station to the mobile station. FIG.
FIG. 4 shows a configuration including a periodic communication request response function when the highly reliable DSRC road-vehicle communication method is applied to a base station and a mobile station having a bidirectional communication function and a one-way communication function from a base station to a mobile station. It is a schematic diagram showing an example.
FIG. 5 is a schematic diagram showing an example of a case where communication is erroneously made with a mobile station traveling on a road to which communication should not be performed due to excessive jumping of radio waves.
FIG. 6 is a schematic diagram illustrating a difference in a communication start position due to a difference in performance of a mobile station.
[Explanation of symbols]
1 Communication area A
2 Communication area B
3 Communication area N
8 Road 9 Traveling direction of mobile station 10 Base station 11 Base station antenna 81 81 Road 100 adjacent to road 8 Mobile station 101 Mobile station 111 running on a road that should not be communicated Mobile station antenna

Claims

Communication between the base station and the mobile station using a short range wireless communication scheme Te road-vehicle communication system odor performed by unidirectional communication to the mobile station from the two-way communication and a base station, communication between the mobile station and the base station when performed in two-way communication, the base station monitors the reception intensity of the radio wave that the mobile station transmits, if the reception intensity of the radio wave is equal to or greater than the determination reference value set in advance, the base station and mobile station Along with establishing bidirectional communication , when the communication between the base station and the mobile station is performed by bidirectional communication and one-way communication from the base station to the mobile station, the mobile station establishes the bidirectional communication. The reception level at the time is stored, and when the reception level of the one-way communication from the base station is equal to or higher than the stored reception level, the reception of the one-way communication from the base station is enabled. Road-to-vehicle communication method.