JP4396928B2 - Communications system - Google Patents

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JP4396928B2
JP4396928B2 JP2004052803A JP2004052803A JP4396928B2 JP 4396928 B2 JP4396928 B2 JP 4396928B2 JP 2004052803 A JP2004052803 A JP 2004052803A JP 2004052803 A JP2004052803 A JP 2004052803A JP 4396928 B2 JP4396928 B2 JP 4396928B2
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弘幸 芥川
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Hitachi Kokusai Electric Inc
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Description

本発明は、伝搬路状況などを判断して適応変調を可能にする通信システムに関するものである。 The present invention relates to a communication system that enables adaptive modulation by determining propagation path conditions and the like.

固定無線機（以下基地局という）と移動体無線機（以下移動局という）の間の無線通信では、移動局の移動速度や周辺の環境によってマルチパスフェージングなどを受ける伝搬環境が随時変動する。
図６はそのような環境状況を示すための通信エリアの一例を示す図である。今、基地局１とエリアＡ，Ｂ，Ｃ内を移動する移動局２が無線で通信を行う際、移動局２がエリアＡ又はＢの範囲を移動中であれば、建物など周辺環境から伝搬状態が比較的良く高品質の通信が可能である。これに対して、移動局２がエリアＣの範囲にある間は、建物など周辺環境から伝搬状態が悪くなる可能性が大きく、受信信号のＳＮが劣化し誤り率が増加する。 In wireless communication between a fixed wireless device (hereinafter referred to as a base station) and a mobile wireless device (hereinafter referred to as a mobile station), the propagation environment that receives multipath fading and the like varies depending on the moving speed of the mobile station and the surrounding environment.
FIG. 6 is a diagram showing an example of a communication area for indicating such an environmental situation. Now, when the mobile station 2 moving in the areas A, B, and C communicates with the base station 1 wirelessly, if the mobile station 2 is moving in the area A or B, it propagates from the surrounding environment such as a building. The condition is relatively good and high quality communication is possible. On the other hand, while the mobile station 2 is in the area C, the propagation state is likely to deteriorate from the surrounding environment such as a building, and the SN of the received signal deteriorates and the error rate increases.

従来、伝搬状態が悪くても誤りのない通信を実現するために、伝搬状態が悪いときは伝送速度を下げて誤り率を低減する適応変調などの技術が知られるが、伝搬路状況の判断に確立された方法はなく様々な検討が進められている。   Conventionally, techniques such as adaptive modulation that reduce the error rate by lowering the transmission rate when the propagation condition is bad are known in order to realize error-free communication even if the propagation condition is bad. There is no established method and various studies are underway.

また、別の手段としてデータ通信の場合は送信側は高い伝送速度で送信し、受信側では誤り率が高ければ自動再送要求（Automatic Repeat reQuest：以下ＡＲＱという）信号により送信側に再送要求を出し、送信側はＡＲＱを受け取ると伝送速度を下げて再送する方法も知られている。   As another means, in the case of data communication, the transmission side transmits at a high transmission rate, and the reception side issues a retransmission request to the transmission side by an automatic repeat request (ARQ) signal if the error rate is high. Also, a method is known in which when the transmission side receives ARQ, it retransmits at a reduced transmission rate.

なお、上記従来例に関連する技術として、下記特許文献が知られている（例えば、特許文献１、２参照。）。
特開平１０−５６４２０号公報 特開２００２−２９０２４６号公報 In addition, the following patent document is known as a technique relevant to the said prior art example (for example, refer patent document 1, 2).
Japanese Patent Laid-Open No. 10-56420 JP 2002-290246 A

しかし、ＡＲＱを用いた技術では、ＡＲＱによる再送という処理が複雑になり、また変調方式等が同じであれば誤り率の向上は認められないという問題があった。   However, the technique using ARQ has a problem that the process of retransmission by ARQ is complicated, and if the modulation method is the same, the error rate cannot be improved.

本発明は上述した事情に鑑みて成されたものであり、例えば基地局−移動局間に適用され、通信を行わない時間帯に、無線伝搬試験を自動で行うことで無線伝搬状態をリアルタイムで随時調査して、伝搬状況が悪いときには、データ伝送速度（変調方式）を下げて誤りのない通信を実現し、また伝搬状況が良いときにはデータ伝送速度を上げて、高品質で効力のある通信を可能にすることができる通信システムを提供することを目的としている。 The present invention has been made in view of the above-described circumstances. For example, the present invention is applied between a base station and a mobile station, and in a time zone in which communication is not performed, a wireless propagation test is automatically performed, so that a wireless propagation state is real-time. We investigate from time to time, and when the propagation situation is poor, lower the data transmission rate (modulation method) to achieve error-free communication, and when the propagation situation is good, increase the data transmission rate to achieve high quality and effective communication. An object is to provide a communication system that can be enabled.

上述した課題を解決するため、本発明に係る通信システムは、基地局と移動局との間の伝搬路状況を判定して変調方式を切替える通信システムにおいて、前記基地局は、自局のＰＴＴ（Press To Talk）のオフ時間とスケルチの閉時間を監視することによって前記移動局と通信を行っているか否か判断し、通信が行われていないと判断したとき、前記移動局との間で伝搬路状況判定用のデータの送受信を行って伝搬路状況についての判定を行うと共に、該判定結果に基づいて該通信区間における通信の変調方式を切替えることを特徴とする。
ここで、前記基地局は、所定時間にわたって通信が行われていないと判断したとき、前記移動局との間で伝搬路状況判定用のデータの送受信を行って伝搬路状況についての判定を行うことを特徴とする。 In order to solve the above-described problems, a communication system according to the present invention is a communication system that determines a propagation path condition between a base station and a mobile station and switches a modulation scheme. (Press To Talk) off time and squelch close time are monitored to determine whether or not communication with the mobile station is performed, and when it is determined that communication is not being performed, propagation to and from the mobile station The present invention is characterized in that determination of a propagation path condition is performed by transmitting / receiving data for determining a road condition, and switching a modulation method of communication in the communication section based on the determination result.
Here, when the base station determines that communication has not been performed for a predetermined time, the base station performs transmission / reception of propagation path status data to / from the mobile station to determine the propagation path status It is characterized by.

実施の形態において、上記伝搬路状況の判定は、無線機（例えば基地局）からＰＮ符号のようなランダムデータを送信相手（例えば移動局）に送信し、送信相手は受信データを復調後、該復調データを変調データとして無線機に返送する。無線機側では、受信データを復調して元のランダムデータと比較して、その誤り率により当該無線機と送信相手の間の無線伝搬状況を判断する。   In the embodiment, the propagation path condition is determined by transmitting random data such as a PN code from a wireless device (for example, a base station) to a transmission partner (for example, a mobile station). The demodulated data is returned to the radio as modulated data. On the wireless device side, the received data is demodulated and compared with the original random data, and the state of wireless propagation between the wireless device and the transmission partner is determined based on the error rate.

また、実施の形態において、通信相手との間で通信を行っていない時間帯の判断は、該無線機が基地局の場合は基地局側のＰＴＴ（Press To Talk）のオフ時間を監視し、移動局の場合は基地局側のアナログ復調部のスケルチの閉時間を監視し、所定の時間にわたり、基地局からも移動局からも送信行為が行われなかったことを条件に判断する。   Further, in the embodiment, the determination of the time zone during which communication with the communication partner is not performed is performed by monitoring the off time of PTT (Press To Talk) on the base station side when the wireless device is a base station, In the case of a mobile station, the closing time of the squelch of the analog demodulation unit on the base station side is monitored, and it is determined on the condition that no transmission act has been performed from the base station or the mobile station for a predetermined time.

実施の形態における基地局と移動局の通信システムは、基地局において非通信時間帯を判断し、該時間帯が判断されると所定の試験信号を変調して移動局に送信すると共に、移動局より該試験信号の受信、復調、再変調後に返送される該試験信号を復調して送信前の試験信号を比較し、該比較結果に基づいて移動局との間における通信の変調方式を切替選択する。   The communication system between the base station and the mobile station in the embodiment determines a non-communication time zone in the base station, modulates a predetermined test signal when the time zone is determined, and transmits the modulated test signal to the mobile station. The test signal returned after receiving, demodulating and remodulating the test signal is demodulated, the test signal before transmission is compared, and the modulation method for communication with the mobile station is selected based on the comparison result To do.

以上に詳述したように本発明によれば、伝搬路状況が考慮された変調方式を用いることにより、伝搬路状況によらず、常に良好な通信を行うことができる通信システムを提供することができる。 As described above in detail, according to the present invention, it is possible to provide a communication system that can always perform good communication regardless of the propagation path condition by using the modulation method in which the propagation path condition is considered. it can.

以下、本発明の実施の形態について図面を参照しつつ説明する。   Embodiments of the present invention will be described below with reference to the drawings.

図１は本実施の形態の全体構成を示す図である。図において、１は基地局、２は基地局１と通信が可能な移動局、１ａ，２ａはそれぞれ基地局１と移動局２に設けられ基地局１と移動局２の間で無線通信を行うための無線通信用アンテナである。また、４は伝搬状況試験時（折り返し試験時）のデータの流れを示している。   FIG. 1 is a diagram showing an overall configuration of the present embodiment. In the figure, 1 is a base station, 2 is a mobile station capable of communicating with the base station 1, and 1a and 2a are provided in the base station 1 and the mobile station 2, respectively, and perform wireless communication between the base station 1 and the mobile station 2 This is an antenna for wireless communication. Reference numeral 4 denotes a data flow at the time of the propagation state test (at the time of the loopback test).

基地局１と移動局２はアンテナ１ａ，２ａを経由して無線通信を行う。基地局１と移動局２の間の無線伝搬状況は周囲環境により随時変動する。基地局１と移動局２の間で伝搬状況試験を随時行い、伝播状況に最適な伝送速度で無線通信を行う。   The base station 1 and the mobile station 2 perform wireless communication via the antennas 1a and 2a. The state of radio propagation between the base station 1 and the mobile station 2 varies from time to time depending on the surrounding environment. A propagation state test is performed between the base station 1 and the mobile station 2 as needed, and wireless communication is performed at a transmission rate optimum for the propagation state.

４で示す伝搬状況試験時のデータの流れによれば、伝搬試験時、基地局１からは例えばＰＮ符号のようなランダムデータを変調して、アンテナ１ａから移動局２に対して送信する。移動局２はアンテナ２ａを介して受信したデータを復調後、該復調データを元のランダム伝送データと比較し、その誤り率により、基地局１−移動局２間の無線伝搬状況を判断する。伝搬状況が悪いときにはデータ伝送速度を下げて誤りのない通信を実現し、また伝搬状況が良いときにはデータ伝送速度を上げて効力のある通信を可能にする。   According to the data flow at the time of the propagation state test indicated by 4, at the time of the propagation test, random data such as a PN code is modulated from the base station 1 and transmitted from the antenna 1 a to the mobile station 2. The mobile station 2 demodulates the data received via the antenna 2a, compares the demodulated data with the original random transmission data, and determines the radio propagation status between the base station 1 and the mobile station 2 based on the error rate. When the propagation situation is bad, the data transmission rate is lowered to realize error-free communication, and when the propagation situation is good, the data transmission rate is raised to enable effective communication.

図２は、本発明の実施の形態における基地局１のブロック図である。図２において、１０１は通常無線運用時(伝搬状況試験時以外)の送信データ入力部である。１２１は擬似データ(ランダムデータ)入力部であり、伝搬状況試験時にランダムデータを生成する。１２２は通信系切替制御部であり、通常通信／伝搬試験を制御する。ＳＷ１は通信系切替制御部の制御により入力データ、出力データを切り替えるスイッチであり、ａ１，ｂ１のいずれかが選択される。１０３は入力部１０１もしくは擬似データ入力部１２１からの入力データと、通信系切替制御部１２２からの通信系情報、方式切替制御部の変調方式情報や他の制御データより１ブロック分の送信データを生成するチャネルコーディング部である。ＳＷ２は１２３で示す方式切替制御部の制御により、変調方式や復調方式を切替えるスイッチであり、ａ２，ｂ２，ｃ２のいずれかが選択される。   FIG. 2 is a block diagram of the base station 1 in the embodiment of the present invention. In FIG. 2, reference numeral 101 denotes a transmission data input unit during normal wireless operation (except during a propagation state test). A pseudo data (random data) input unit 121 generates random data during a propagation state test. A communication system switching control unit 122 controls the normal communication / propagation test. SW1 is a switch for switching input data and output data under the control of the communication system switching control unit, and either a1 or b1 is selected. 103 indicates transmission data for one block from input data from the input unit 101 or the pseudo data input unit 121, communication system information from the communication system switching control unit 122, modulation system information of the system switching control unit and other control data. This is a channel coding unit to be generated. SW2 is a switch for switching the modulation method and the demodulation method under the control of the method switching control unit indicated by 123, and any one of a2, b2, and c2 is selected.

１０５はチャネルコーディング部１０３からの送信データに対しベースバンド帯の１６ＱＡＭ変調を行う１６ＱＡＭ変調部である。１０６はチャネルコーディング部１０３からの送信データに対しベースバンド帯のＱＰＳＫ変調を行うＱＰＳＫ変調部である。１０７はチャネルコーディング部１０３からの送信データに対しベースバンド帯のＢＰＳＫ変調を行うＢＰＳＫ変調部である。１０８はベースバンド変調波に対してＡＭなどの変調処理を施すアナログ変調部であり、アナログ変調波を出力する。１０９は該アナログ変調波（中間周波数帯）を無線周波数帯に変換する送信部である。１１０は無線周波数帯の信号を無線出力レベルまで増幅させる電力増幅部であり、電力増幅後に送信用アンテナ１ａ−１より移動局に対して送信する。   Reference numeral 105 denotes a 16QAM modulation unit that performs baseband 16QAM modulation on transmission data from the channel coding unit 103. Reference numeral 106 denotes a QPSK modulation unit that performs baseband QPSK modulation on transmission data from the channel coding unit 103. Reference numeral 107 denotes a BPSK modulation unit that performs baseband BPSK modulation on transmission data from the channel coding unit 103. An analog modulation unit 108 performs modulation processing such as AM on the baseband modulated wave, and outputs an analog modulated wave. Reference numeral 109 denotes a transmitter that converts the analog modulated wave (intermediate frequency band) into a radio frequency band. Reference numeral 110 denotes a power amplifying unit that amplifies a radio frequency band signal to a radio output level, which is transmitted from the transmitting antenna 1a-1 to the mobile station after power amplification.

１ａ−２は受信用のアンテナであり、１１３は移動局２から受信用アンテナ１ａ−２を介して受信された受信信号（無線周波数帯）を中間周波数に変換する受信部である。１１４は、中間周波数に対してアナログ復調を行うスケルチ機能を有するアナログ復調部である。１１５はベースバンド帯の１６ＱＡＭ復調を行う１６ＱＡＭ復調部である。１１６はベースバンド帯のＱＰＳＫ復調を行うＱＰＳＫ復調部である。１１７はベースバンド帯のＢＰＳＫ復調を行うＢＰＳＫ復調部である。   Reference numeral 1a-2 denotes a reception antenna, and reference numeral 113 denotes a reception unit that converts a reception signal (radio frequency band) received from the mobile station 2 via the reception antenna 1a-2 into an intermediate frequency. Reference numeral 114 denotes an analog demodulation unit having a squelch function for performing analog demodulation on the intermediate frequency. Reference numeral 115 denotes a 16QAM demodulator that performs 16QAM demodulation in the baseband. Reference numeral 116 denotes a QPSK demodulator that performs QPSK demodulation in the baseband. Reference numeral 117 denotes a BPSK demodulator that performs baseband BPSK demodulation.

１１８は１６ＱＡＭもしくはＱＰＳＫもしくはＢＰＳＫ復調データよりデータと通信系情報、方式情報などのデータを分離するチャネルデコーディング部である。１１９はチャネルデコーディング部の通常無線運用時（伝搬状況試験時以外）の受信データ出力部である。１２０は伝搬状況試験時の擬似データ判定部であり、擬似データ入力部１２１とのデータを比較して、その誤り率より次ブロック送信時の変調方式を決定する。   Reference numeral 118 denotes a channel decoding unit that separates data such as communication system information and system information from 16QAM, QPSK, or BPSK demodulated data. Reference numeral 119 denotes a reception data output unit when the channel decoding unit is in normal radio operation (except during the propagation state test). A pseudo data determination unit 120 at the time of the propagation state test compares data with the pseudo data input unit 121, and determines a modulation method at the next block transmission from the error rate.

以下、基地局の動作として、伝搬状況試験時の動作を説明する。伝搬状況試験は基地局と移動局間で無線通信の行われていない時間を監視して行う。例えば、基地局からの送信は基地局側のＰＴＴ(Press To Talk)のＯＦＦ時間を監視、移動局からの送信は基地局側のアナログ復調部１１４のスケルチの閉時間を監視することで行う。   Hereinafter, as the operation of the base station, the operation during the propagation state test will be described. The propagation state test is performed by monitoring the time when wireless communication is not performed between the base station and the mobile station. For example, transmission from the base station is performed by monitoring the PTT (Press To Talk) OFF time on the base station side, and transmission from the mobile station is performed by monitoring the squelch closing time of the analog demodulation unit 114 on the base station side.

その結果、固定時間（例えば１５分間）基地局からも移動局からの送信が行われなかった際に伝搬状況試験を行う。伝搬状況試験は、通信系切替制御部１２２によりＳＷ１をｂ１側に切替えて行う。このとき、擬似データ入力部１２１からＰＮなどのランダムデータを生成して送信データとする。チャネルコーディング部１０３では、擬似データ入力部１２１からのデータと通信系情報、変調方式情報や他の制御パラメータを付加した送信データを作成する。チャネルコーディング部で作成される送信データフォーマットの一例を実施例を図３に示す。   As a result, a propagation state test is performed when transmission from the mobile station is not performed from the base station for a fixed time (for example, 15 minutes). The propagation state test is performed by switching SW1 to the b1 side by the communication system switching control unit 122. At this time, random data such as PN is generated from the pseudo data input unit 121 and used as transmission data. The channel coding unit 103 creates transmission data to which data from the pseudo data input unit 121 and communication system information, modulation scheme information, and other control parameters are added. An example of a transmission data format created by the channel coding unit is shown in FIG.

この送信フォーマットでは、送信１ブロックデータに対して方式切替制御部１２３の制御により高速伝送の１６QAM変調ベースバンド帯の変調処理を行い、アナログ変調部１０８によりＡM変調等のアナログ変調が施され、送信部１０９で無線周波数帯に変換後、電力増幅部１１０で電力増幅されアンテナ１ａ１より移動局２へ送信する。   In this transmission format, modulation of the 16QAM modulation baseband for high-speed transmission is performed on the transmission 1 block data under the control of the system switching control unit 123, and analog modulation such as AM modulation is performed by the analog modulation unit 108. After being converted to a radio frequency band by unit 109, the power is amplified by power amplifying unit 110 and transmitted from antenna 1 a 1 to mobile station 2.

また、受信側では移動局２より返送されたデータをアンテナ１ａ−２で受信すると、受信部１１３で周波数変換した信号をアナログ復調部１１４でベースバンド変調波に復調し、その後、１６ＱＡＭ復調部１１５による復調を施し、チャネルデコーディング部１１８へ出力する。チャネルデコーディング部１１８では、データと通信系情報と方式情報とその他の制御パラメータに分割する。伝搬状況試験中はチャネルデコーディング部１１８で分割されたデータは、擬似データ判定部１２０に出力され、擬似データ入力部１２１で生成送信したデータと比較する。１０の９乗ｂｉｔ程度の擬似データを生成するまで上記動作を繰り返してその誤り率で伝搬状況を判断する。   On the receiving side, when the data returned from the mobile station 2 is received by the antenna 1a-2, the frequency-converted signal by the receiving unit 113 is demodulated into a baseband modulated wave by the analog demodulating unit 114, and then the 16QAM demodulating unit 115 is obtained. Is output to the channel decoding unit 118. The channel decoding unit 118 divides data, communication system information, system information, and other control parameters. During the propagation state test, the data divided by the channel decoding unit 118 is output to the pseudo data determination unit 120 and compared with the data generated and transmitted by the pseudo data input unit 121. The above operation is repeated until pseudo data of about 10 9 bits is generated, and the propagation status is determined based on the error rate.

誤りがあれば、ＳＷ２をｂ２に切替えてＱＰＳＫ変調ベースバンド変調で上記を繰り返す。図４に試験結果と伝搬状況の関係を示している。以上の伝搬状況試験により、通常運用時の伝送速度（ベースバンド変調方式）を決定する。   If there is an error, SW2 is switched to b2 and the above is repeated with QPSK modulation baseband modulation. FIG. 4 shows the relationship between test results and propagation conditions. The transmission rate (baseband modulation system) during normal operation is determined by the above propagation condition test.

図５は実施の形態における移動局のブロック図を示す。
図５において、各符号の下二桁が図３と同じ物は図３に示したものに想到している。即ち、移動局の基本的構成は、図３において説明した基地局の構成とほぼ同じであるため異なる部分のみを説明する。移動局側には基地局１が有する擬似データ入力部１２１、擬似データ判定部１２０がなく、別に通信系判定部２２０´が設けられている。通信系判定部２２０´はチャネルデコーディング部２１８より通信系情報を入手し、ＳＷ１を切替える通信系判定部である。 FIG. 5 shows a block diagram of the mobile station in the embodiment.
In FIG. 5, the last two digits of each symbol are the same as those in FIG. That is, the basic configuration of the mobile station is almost the same as the configuration of the base station described with reference to FIG. On the mobile station side, the pseudo data input unit 121 and the pseudo data determination unit 120 included in the base station 1 are not provided, and a communication system determination unit 220 ′ is provided separately. The communication system determination unit 220 ′ is a communication system determination unit that obtains communication system information from the channel decoding unit 218 and switches SW1.

以下、移動局の伝搬状況試験時の動作を説明する。
基本的に図３の基地局と同じであるため異なる部分のみを説明する。
移動局のチャネルデコーディング部２１８では、ベースバンド復調後の復調データをデータ、変調方式情報、通信系情報、その他の制御パラメータに分割する。通信系情報により伝搬状況試験中であると判断すると、ＳＷ１をｂ１側に切替えて、復調データを送信側の入力データとして、基地局への返送データとする（このときのデータは擬似データ入力部１２１で生成したランダムデータである）。これにより、基地局１から移動局２、移動局２から基地局１というデータフローで無線折り返し試験（伝搬状況）の試験系を構築する。 The operation during the propagation status test of the mobile station will be described below.
Since it is basically the same as the base station of FIG. 3, only the different parts will be described.
The channel decoding unit 218 of the mobile station divides demodulated data after baseband demodulation into data, modulation scheme information, communication system information, and other control parameters. If it is determined from the communication system information that the propagation status test is being performed, SW1 is switched to the b1 side, and the demodulated data is used as input data on the transmission side to be returned to the base station (the data at this time is a pseudo data input unit) Random data generated at 121). Thus, a test system for a radio loopback test (propagation state) is constructed with a data flow from the base station 1 to the mobile station 2 and from the mobile station 2 to the base station 1.

本発明の実施の形態の系統図である。It is a systematic diagram of an embodiment of the invention. 実施の形態における基地局のブロック図である。It is a block diagram of a base station in an embodiment. 実施の形態における送信１ブロックのフォーマットを示す図である。It is a figure which shows the format of 1 transmission block in embodiment. 伝搬状況試験結果と伝送速度の関係を示す図である。It is a figure which shows the relationship between a propagation condition test result, and a transmission rate. 実施の形態における移動局のブロック図である。It is a block diagram of the mobile station in embodiment. 通信エリアの一例を示す図である。It is a figure which shows an example of a communication area.

符号の説明Explanation of symbols

１ 基地局、２ 移動局、１０１，２０１ 入力部、１０３，２０３ チャネルコーディング部、１０５，２０５ １６ＱＡＭ変調部、１０６，２０６ ＱＰＳＫ変調部、１０７，２０７ ＢＰＳＫ変調部、１１５，２１５ １６ＱＡＭ復調部、１１６，２１６ ＱＰＳＫ復調部、１１７，２１７ ＢＰＳＫ復調部、１１８，２１８ チャネルデコーディング部、１１９，２１９ 出力部、１２０ 擬似データ判定部、１２１ 擬似データ入力部、１２２ 通信系切替制御部、１２３，２２３ 方式切替制御部、２２０´ 通信系判定部。     1 base station, 2 mobile station, 101, 201 input unit, 103, 203 channel coding unit, 105, 205 16QAM modulation unit, 106, 206 QPSK modulation unit, 107, 207 BPSK modulation unit, 115, 215 16QAM demodulation unit, 116 , 216 QPSK demodulation unit, 117, 217 BPSK demodulation unit, 118, 218 channel decoding unit, 119, 219 output unit, 120 pseudo data determination unit, 121 pseudo data input unit, 122 communication system switching control unit, 123, 223 Switching control unit, 220 ′ communication system determination unit.

Claims (2)

基地局と移動局との間の伝搬路状況を判定して変調方式を切替える通信システムにおいて、In a communication system that determines a propagation path condition between a base station and a mobile station and switches a modulation method,
前記基地局は、自局のＰＴＴ（Press To Talk）のオフ時間とスケルチの閉時間を監視することによって前記移動局と通信を行っているか否か判断し、通信が行われていないと判断したとき、前記移動局との間で伝搬路状況判定用のデータの送受信を行って伝搬路状況についての判定を行うと共に、該判定結果に基づいて該通信区間における通信の変調方式を切替えることを特徴とする通信システム。  The base station determines whether it is communicating with the mobile station by monitoring its own PTT (Press To Talk) off time and squelch closing time, and determines that communication is not being performed. When performing transmission / reception data transmission / reception data transmission / reception with the mobile station to determine the propagation path condition, the communication modulation method in the communication section is switched based on the determination result. A communication system. 前記基地局は、所定時間にわたって通信が行われていないと判断したとき、前記移動局との間で伝搬路状況判定用のデータの送受信を行って伝搬路状況についての判定を行うことを特徴とする請求項１に記載の通信システム。When the base station determines that communication has not been performed for a predetermined time, the base station performs transmission / reception data transmission / reception data transmission / reception with the mobile station to determine the propagation path condition. The communication system according to claim 1.
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