JPH08205120A

JPH08205120A - Two-way transmission system of catv

Info

Publication number: JPH08205120A
Application number: JP7011754A
Authority: JP
Inventors: Hiromi Tanaka; 大幹田中; Hiroyuki Mizukami; 博之水上
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1995-01-27
Filing date: 1995-01-27
Publication date: 1996-08-09
Anticipated expiration: 2018-06-09
Also published as: JP3415311B2

Abstract

PURPOSE: To make an efficient two-way communication request of CATV by performing retransmission on a subscriber side in random timing if plural requests conflict with each other at a repeating device, and reducing the probability of a reconflict. CONSTITUTION: The repeating device 2 once accepting an access request signal from a subscriber HT3 sends a signal being a transmission permission for the accepted subscriber HT and being a busy signal for other subscribers HT. Further, sent data are transferred to a center 1 by polling. Then when a process end signal is sent from the center 1 to the repeating device 2, the repeating device 2 sends an idle signal to the respective subscribers HT. Each subscriber when receiving the idle signal outputs an access request in random timing to make a two-way communication of CATV. Consequently, the repeating device 2 can quickly respond to the request from the subscriber HT3.

Description

Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、センタと複数の加入者
の間に中継器を持ち双方向通信の可能なＣＡＴＶに関
し、特に複数の加入者からセンタに対する多くのアクセ
ス要求の発生に対処する伝送システムに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV having a repeater between a center and a plurality of subscribers and capable of two-way communication, and particularly dealing with generation of many access requests from a plurality of subscribers to the center. Transmission system.

【０００２】[0002]

【従来の技術】センタと複数の加入者の間に中継器を持
ち双方向通信の可能なＣＡＴＶにおける従来のポーリン
グ方式では、ヘッドエンドから周波数多重された再送信
サービス信号や自主放送サービス信号などのテレビジョ
ン信号を中継装置を介して加入者端末（ＨＴ：ホームタ
ーミナル）に送信し、双方向制御信号をこれに多重して
双方向通信を行なっている。2. Description of the Related Art In the conventional polling system in CATV, which has a repeater between a center and a plurality of subscribers and is capable of two-way communication, in a conventional polling system such as a frequency-multiplexed retransmission service signal or an independent broadcasting service signal, A television signal is transmitted to a subscriber terminal (HT: home terminal) via a relay device, and a bidirectional control signal is multiplexed on the television signal for bidirectional communication.

【０００３】図４は、従来のポーリング方式による信号
の流れを動作シーケンスで示した図であり、センタは、
双方向サービス処理部から複数の中継装置に向けて順に
ポーリングを行なう。中継装置は、このポーリングに対
し記憶手段に記録していた加入者からの要求を出力す
る。FIG. 4 is a diagram showing a signal flow according to a conventional polling method in an operation sequence.
The bidirectional service processing unit sequentially polls a plurality of relay devices. In response to this polling, the relay device outputs the request from the subscriber recorded in the storage means.

【０００４】また、中継装置は、複数の加入者端末に向
けて順にポーリングを行なう、この中継装置からのポー
リングに対し各加入者端末（ＨＴ）は、加入者からの要
求が無い場合は自分の加入者端末のアドレスおよび“要
求無し”を意味する情報を含むデータを中継装置の双方
向サービス処理部に対し送り返す。中継装置の双方向処
理部は、この情報データを解析する手段を有し、加入者
からの要求がある場合にはその要求データをデータ記憶
手段に記録するかもしくは中継装置に選局などの処理能
力がある場合に限り要求に応じた処理を行ない、要求が
無い場合には次の加入者端末をポーリングする。このよ
うにしてシステムが動作している限りはポーリングを続
けることになる。Further, the relay device sequentially polls a plurality of subscriber terminals, and each subscriber terminal (HT) responds to the polling from this relay device by its own unless there is a request from the subscriber. Data including the address of the subscriber terminal and information indicating "no request" is sent back to the interactive service processing unit of the relay device. The bidirectional processing unit of the relay device has a means for analyzing this information data, and when the subscriber requests, record the requested data in the data storage means or perform processing such as channel selection in the relay device. Only when there is capability, the processing according to the request is performed, and when there is no request, the next subscriber terminal is polled. In this way polling will continue as long as the system is operating.

【０００５】[0005]

【発明が解決しようとする課題】上述した従来の中継装
置を有するＣＡＴＶでは、加入者端末が、中継装置に対
しアクセスする場合には、中継装置からのポーリングに
対して応答する形でのみアクセスが可能であった。つま
り、中継装置が割り当てられた全ての加入者に対しポー
リングを行なっていたわけであるが、この方式では加入
者数が増えるにつれて１件の加入者に対するポーリング
の間隔が長くなり、迅速なアクセスが出来にくくなると
共に中継装置の負荷が増加するという問題が生じる。In the CATV having the above-mentioned conventional relay device, when the subscriber terminal accesses the relay device, the access can be made only by responding to the polling from the relay device. It was possible. In other words, all the subscribers to which the relay device was assigned polled, but with this method, the polling interval for one subscriber becomes longer as the number of subscribers increases, and quick access is possible. There is a problem that it becomes difficult and the load of the relay device increases.

【０００６】また、この方式では、一方で信号の伝送帯
域幅が固定であるので、これに再送信番組や自主放送番
組にチャネルを割り当てるとデマンドサービスに使用可
能なチャネル数は自ずと決定されることになる。このよ
うな方式では、多数の加入者の要求を満たす程にはチャ
ネル数が確保出来ないという問題があった。In this system, on the other hand, since the signal transmission bandwidth is fixed, if channels are allocated to retransmitted programs and independent broadcast programs, the number of channels that can be used for the demand service is naturally determined. become. In such a system, there is a problem that the number of channels cannot be secured so as to satisfy the demands of many subscribers.

【０００７】このように、従来の方式では、回線の不足
によってサービスが受けられない確率が高くなってしま
うとともに、高速アクセスを実現する障害となり、ＶＯ
Ｄなどのデマンドサービスにおける問題があった。As described above, in the conventional method, the probability that the service cannot be received becomes high due to the shortage of the line, and it becomes an obstacle for realizing the high speed access.
There was a problem with demand services such as D.

【０００８】本発明は、双方向通信方式およびＶＯＤな
どのデマンドアクセスサービスを行なう上で必ず問題と
なるチャネル回線数の不足を解決するために、多数の加
入者からの要求に対し、どのようなタイミングでアクセ
スしても迅速に対応でき、中継装置の負荷を軽減すると
ともに処理効率を向上したシステムを提供することを目
的とする。In order to solve the shortage of the number of channel lines, which is always a problem in performing a demand access service such as a bidirectional communication system and VOD, the present invention can be applied to any request from a large number of subscribers. An object of the present invention is to provide a system capable of responding promptly even when accessed at a timing, reducing the load on the relay device and improving the processing efficiency.

【０００９】[0009]

【課題を解決するための手段】本発明は、センタと中継
装置の間では、センタからのポーリングによる双方向通
信を行ない、中継装置と複数の加入者の間ではサービス
を要求する加入者のみが中継装置と交信を行なうランダ
ムアクセス方式を用いることによって、ポーリングによ
るアクセス方式で必ず生じる全ての加入者に対する往復
のデータ伝送に要するムダな時間を減少させ、中継装置
の負荷の軽減および迅速なアクセスを実現する。一方、
上述したチャネル回線数の不足に対しては中継装置内に
周波数多重回路を置くことで各中継装置に新たな伝送帯
域が与えられることになりデマンドサービスに使用可能
な回線も中継装置と共に一定数増加させることができ
る。According to the present invention, two-way communication by polling from the center is performed between the center and the relay device, and only the subscriber who requests the service between the relay device and the plurality of subscribers. By using the random access method that communicates with the relay device, it is possible to reduce the wasteful time required for round-trip data transmission to all subscribers, which always occurs in the access method by polling, to reduce the load on the relay device and to make quick access. To be realized. on the other hand,
For the above-mentioned shortage of the number of channel lines, by placing a frequency multiplexing circuit in the repeater, a new transmission band is given to each repeater, and the number of lines that can be used for demand service increases with the repeater. Can be made.

【００１０】センタは、ヘッドエンドにおいて通常のテ
レビジョン信号を周波数多重すること無く中継装置に対
し提供し、センタ内の第１の通信処理部においてポーリ
ング信号および下り要求信号を伝送する。The center provides an ordinary television signal to the relay device without frequency-multiplexing it at the head end, and transmits a polling signal and a downlink request signal in the first communication processing section in the center.

【００１１】中継装置においては、上記テレビジョン信
号などの各種信号が個々の中継装置毎に周波数多重され
各中継装置においてデマンドサービスに使用可能な回線
が同じ数だけ確保される。つまり中継装置の数に応じて
使用可能な回線数は増加することになる。加入者端末か
ら送信されるアクセス要求信号は、衝突または通信障害
の有無を確認された後、信号が正常であった場合は直ち
に受け付けられ記憶手段に記憶される。この時中継装置
の状態情報として、該当する加入者端末への要求データ
送信許可およびその他の加入者端末に対するビジー状態
信号が送信される。上記記憶されたデータはその内容が
デマンドサービスの要求またはセンタからの要求に対す
る上りデータに限りセンタからのポーリングに対応して
送信される。信号に異常のあった場合には、受信された
信号は無効となり、中継装置からアイドル状態信号が送
信される。これらの状態信号を加入者端末において受信
および解析することによって、各加入者端末は、アクセ
ス要求信号の送信のタイミングを得ることができる。In the repeater, various signals such as the above television signals are frequency-multiplexed for each repeater so that the same number of lines available for demand service are secured in each repeater. That is, the number of usable lines increases according to the number of relay devices. The access request signal transmitted from the subscriber terminal is immediately accepted and stored in the storage means when the signal is normal after the presence or absence of collision or communication failure is confirmed. At this time, the request data transmission permission to the corresponding subscriber terminal and the busy status signal to the other subscriber terminals are transmitted as the status information of the relay device. The stored data is transmitted in response to polling from the center only in the case of upstream data in response to a demand service request or a request from the center. If the signal is abnormal, the received signal becomes invalid and the relay device transmits an idle state signal. By receiving and analyzing these status signals at the subscriber terminals, each subscriber terminal can obtain the timing of transmission of the access request signal.

【００１２】別の方法として、中継装置から状態信号の
送信がない構成では各加入者端末がアクセス要求信号を
出力した後、一定時間を計測しこの間に要求データ許可
信号が得られなかった場合再送信を行なう方法もある
（図５参照）。個々の加入者端末はアクセス要求信号の
出力タイミングをその都度ランダムに変化させて、信号
の衝突する確立を低下させている。これによりアクセス
の高速化に対し効果が得られる。As another method, in a configuration in which no status signal is transmitted from the relay device, after each subscriber terminal outputs an access request signal, a certain period of time is measured and if no request data permission signal is obtained during this time There is also a method of transmitting (see FIG. 5). Each subscriber terminal randomly changes the output timing of the access request signal to reduce the probability of signal collision. This has the effect of speeding up access.

【００１３】加入者端末は、何ら要求の無い場合には、
中継装置に対しアクセス要求信号を送信することは無
く、ただ中継装置から送信されて来る状態信号を解析し
ているだけである。このことによって、中継装置は処理
を必要とする加入者端末のみを正常なデータが受け付け
られた順に対象とすれば良く、ポーリング方式に比べ中
継装置の負荷は軽減される。また、加入者端末からのア
クセス要求がある一定のレベルを越えた場合に生じると
考えられる、長時間にわたるアクセス不可状態には、一
旦ポーリングによるアクセス方式を実行することによっ
てアクセスの信頼性が補償される。The subscriber terminal, if there is no request,
No access request signal is transmitted to the relay device, but only the status signal transmitted from the relay device is analyzed. This allows the relay device to target only the subscriber terminals that require processing in the order in which normal data is received, and the load on the relay device is reduced compared to the polling method. In addition, in the inaccessible state for a long time, which is considered to occur when the access request from the subscriber terminal exceeds a certain level, the access reliability is compensated by once executing the access method by polling. It

【００１４】[0014]

【実施例】次に、本発明の実施例について図を用いて説
明する。図１は、本発明に係るＣＡＴＶシステムの基本
構成を示すシステム概念図である。図２は、従来の代表
的な双方向ＣＡＴＶシステムの構成を示すシステム概念
図である。図３は、本発明によるＣＡＴＶシステムにお
ける双方向通信部の構成を示しており具体的な双方向通
信の流れを説明するブロック図である。図４は、従来の
ポーリング方式によるアクセス動作シーケンス図であ
る。図５は、本発明のアクセス方式の一実施例を示すア
クセス動作シーケンス図である。図２は、従来の代表的
な双方向ＣＡＴＶシステムの構成図であるが、この構成
においても請求項１〜請求項８のアクセス方式を実現す
ることができる。Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system conceptual diagram showing the basic configuration of a CATV system according to the present invention. FIG. 2 is a system conceptual diagram showing a configuration of a conventional typical bidirectional CATV system. FIG. 3 is a block diagram showing the configuration of the bidirectional communication unit in the CATV system according to the present invention and explaining the specific flow of the bidirectional communication. FIG. 4 is a sequence diagram of an access operation by the conventional polling method. FIG. 5 is an access operation sequence diagram showing an embodiment of the access method of the present invention. FIG. 2 is a block diagram of a conventional typical bidirectional CATV system, but the access methods of claims 1 to 8 can be realized also in this structure.

【００１５】以下、図２のシステム構成において、本発
明のアクセス方式を実現する実施例について説明する。
双方向ＣＡＴＶシステムは、センタ１と中継装置２と、
加入者宅３とから構成されており、センタ１と中継装置
２の間は光ファイバケーブル４で接続され、中継装置２
と各加入者宅３との間は同軸ケーブル５で接続されてい
る。センタ１は、ヘッドエンド１０１と、第１の双方向
通信部１０２と、システム制御部１０３と、システム管
理部１０４とから構成される。ヘッドエンド１０１は、
受信したＴＶ放送信号やＡＴＭスイッチを介したビデオ
サーバからの信号や受信したＴＶ放送信号などが入力さ
れこれらを多重化する周波数多重回路１１０と、光送受
信器１１１とから構成される。An embodiment for realizing the access method of the present invention in the system configuration of FIG. 2 will be described below.
The bidirectional CATV system includes a center 1, a relay device 2,
It is composed of a subscriber's house 3, and the center 1 and the relay device 2 are connected by an optical fiber cable 4.
And each subscriber's house 3 are connected by a coaxial cable 5. The center 1 includes a head end 101, a first bidirectional communication unit 102, a system control unit 103, and a system management unit 104. The headend 101 is
It is composed of a frequency multiplexing circuit 110 for receiving a received TV broadcast signal, a signal from a video server via an ATM switch, a received TV broadcast signal, etc. and multiplexing them, and an optical transceiver 111.

【００１６】中継装置２は、複数の加入者制御部２００
−１〜２００−ｎ＋１と、合分配器２０４と、光送受信
器２０５とから構成され、それぞれの加入者制御部２０
０はチャネル選択器２０１と、第２の双方向通信部２０
２と、送受信器２０３とから構成される。The relay device 2 includes a plurality of subscriber control units 200.
-1 to 200-n + 1, a multiplexer / distributor 204, and an optical transmitter / receiver 205, and each subscriber control unit 20.
0 is the channel selector 201 and the second bidirectional communication unit 20.
2 and a transceiver 203.

【００１７】加入者宅３には、複数のホームターミナル
（ＨＴ）３００−１〜３００−３と、モニタ３０１と、
送受信器３０５とが備えられ、ホームターミナル３００
は、チューナ部と、第３の双方向通信部３０２と、リモ
コン受信部と３０３、合分波器３０４とから構成されて
いる。At the subscriber's home 3, a plurality of home terminals (HT) 300-1 to 300-3, a monitor 301,
The home terminal 300 is provided with a transceiver 305.
Is composed of a tuner section, a third bidirectional communication section 302, a remote control reception section 303, and a multiplexer / demultiplexer 304.

【００１８】加入者からの要求信号は、リモコン受信部
３０３から第３の双方向通信部３０２を通り同軸ケーブ
ル５を介して中継装置２へ向けて出力される。この信号
は、加入者宅３の第３の送受信器３０５で合波され、中
継装置２の送受信器２０３で分波され中継装置内にある
第２の双方向通信部２０２に送られる。The request signal from the subscriber is output from the remote control receiver 303 to the relay device 2 through the third bidirectional communication unit 302 and the coaxial cable 5. This signal is multiplexed by the third transmitter / receiver 305 of the subscriber's house 3, demultiplexed by the transmitter / receiver 203 of the relay device 2, and sent to the second two-way communication unit 202 in the relay device.

【００１９】第２の双方向通信部２０２では加入者から
の要求に従って加入者の好みのサービスを提供するデマ
ンドサービス以外の処理を行なうことが出来る。例えば
通常放送などのチャネル選択などの制御を行なう。もし
加入者からの要求がデマンドサービスの要求であった場
合、その信号は、一旦第２の双方向通信部２０２に記憶
され、センタ１からポーリング信号が送信された場合
に、要求信号として第２の双方向通信部２０２から光フ
ァイバケーブル４を介してセンタ１に向けて送信され
る。センタ１に向けて送信された信号は中継装置２内の
合分配器２０４及び光送受信器２０５を通り光ファイバ
ケーブル４に出力される。この上り信号はセンタ１内の
ヘッドエンドに含まれる光送受信器１１１で受信及び光
／電気変換された後第１の双方向通信部１０２に伝達さ
れる。The second two-way communication unit 202 can perform processing other than the demand service for providing the service desired by the subscriber in accordance with the request from the subscriber. For example, control such as channel selection for normal broadcasting is performed. If the request from the subscriber is a demand service request, the signal is temporarily stored in the second two-way communication unit 202, and when the polling signal is transmitted from the center 1, the second signal is sent as the request signal. Is transmitted from the bidirectional communication unit 202 to the center 1 via the optical fiber cable 4. The signal transmitted to the center 1 is output to the optical fiber cable 4 through the combiner / distributor 204 and the optical transmitter / receiver 205 in the repeater 2. This upstream signal is received and optically / electrically converted by the optical transmitter / receiver 111 included in the head end in the center 1, and then transmitted to the first bidirectional communication unit 102.

【００２０】第１の双方向通信部１０２では、この信号
から要求内容を解析し、その内容に応じた処理装置に命
令を伝達し制御する。この要求が仮りにビデオ・オン・
デマンド（ＶＯＤ）であったなら、双方向通信部１０２
は、加入者の希望の番組をビデオサーバから交換器であ
るＡＴＭスイッチに信号出力させる。ＡＴＭスイッチ
は、双方向通信部１０２に指定された空き回線に信号を
転送する。このように要求された処理が終了すると直ち
に第１の双方向通信部１０２から中継装置２の第２の双
方向通信部２０２に向けて処理終了を意味する信号を送
信する。The first two-way communication unit 102 analyzes the request content from this signal and transmits a command to the processing device according to the content to control it. This request is supposed to be video on
If it is a demand (VOD), the bidirectional communication unit 102
Causes the video program of the subscriber to be output from the video server to the ATM switch, which is an exchange. The ATM switch transfers a signal to an empty line designated by the bidirectional communication unit 102. Immediately after the requested processing is completed, the first bidirectional communication unit 102 transmits a signal indicating the end of processing to the second bidirectional communication unit 202 of the relay device 2.

【００２１】中継装置２の第２の双方向通信部２０２
は、センタからの処理終了を意味する信号を受信する
と、加入者からのアクセス要求を受け付けないビジー状
態からアイドル状態へ移行し、加入者端末（ＨＴ）に向
けてアイドル信号を一斉送信する。これを受けてホーム
ターミナル（ＨＴ）３００は、アクセス要求が生じる毎
に要求信号を出力する。The second bidirectional communication section 202 of the relay device 2
When receiving a signal indicating the end of processing from the center, shifts from a busy state in which an access request from a subscriber is not accepted to an idle state, and simultaneously transmits an idle signal to a subscriber terminal (HT). In response to this, the home terminal (HT) 300 outputs a request signal each time an access request occurs.

【００２２】以上、簡単にシステム上の双方向通信の流
れを説明したが、参考として本発明の制御信号の基本的
な流れを示すシーケンスを図５を用いて説明する。セン
タからは順次ポーリングが行なわれ、中継装置は、ＨＴ
からの要求を記憶しておき、ポーリングがあったときに
記憶した要求内容をセンタに送信する。中継装置は、Ｈ
Ｔからアクセス要求がないときには、アイドル信号を各
ＨＴに送信する。ＨＴは、アイドル信号があったときに
中継装置に対してアクセス要求を送出し、中継装置はこ
のアクセス要求を受けると送信許可信号をＨＴへ送信す
るとともに、他のＨＴに対してビジー信号を送信して他
のＨＴからのアクセス要求を拒絶する。送信許可信号を
受信したＨＴは、アクセス要求データを送信する。中継
装置は、このデータを記憶しておき次回のポーリングが
あるとこの要求内容をセンタに送信する。センタは、Ｈ
Ｔからの要求を受けてＨＴへ向けて要求内容に対応した
情報を転送するための処理を行なう。この処理が終了す
ると、処理終了が中継装置に伝えられると共に、センタ
からＨＴへ向けて所定の情報の転送が開始される。処理
終了を受けた中継装置は、アイドル信号を発し他のＨＴ
からのアクセス要求に備える。Although the flow of bidirectional communication on the system has been briefly described above, a sequence showing the basic flow of the control signal of the present invention will be described with reference to FIG. 5 for reference. Polling is performed sequentially from the center, and the relay device
Request is stored, and the stored request content is transmitted to the center when polling is performed. The relay device is H
When there is no access request from T, an idle signal is transmitted to each HT. The HT sends an access request to the relay device when an idle signal is received, and when the relay device receives this access request, the HT sends a transmission permission signal to the HT and also sends a busy signal to another HT. Then, the access request from another HT is rejected. Upon receiving the transmission permission signal, the HT transmits access request data. The relay device stores this data and transmits this request content to the center when the next polling is performed. Center is H
Upon receiving the request from T, processing for transferring information corresponding to the requested content to HT is performed. When this process ends, the end of the process is notified to the relay device and transfer of predetermined information from the center to the HT is started. Upon receipt of the processing end, the relay device emits an idle signal and outputs another HT.
Prepare for access request from.

【００２３】また、本発明は、通信方式に関するもので
あって、センタおよび中継装置ならびに加入者端末の双
方向通信部１０２，２０２，３０２に関する説明によっ
て理解されるべきである。従って本発明に関する説明で
は、同軸ケーブル５、光送受信器１１１，２０５、送受
信器２０３，３０５、モニタ３０１などの本発明におい
て特に注意を払われてはいない装置は簡単のため省略し
て説明を行なう。特に幹線に挿入されるべき増幅器等の
公知の装置については説明の簡便性を優先するため記述
を省略したことを明記しておく。また、伝送ケーブルに
おいては光又は同軸ケーブルのどちらを用いたとしても
本システムは構成可能であることは言うまでもない。Further, the present invention relates to a communication system and should be understood by the description of the center and the relay device and the bidirectional communication units 102, 202 and 302 of the subscriber terminals. Therefore, in the description of the present invention, the devices such as the coaxial cable 5, the optical transmitters / receivers 111 and 205, the transmitters / receivers 203 and 305, and the monitor 301 which are not particularly noted in the present invention are omitted for simplicity. . In particular, it should be noted that the description of known devices such as amplifiers to be inserted in the main line is omitted because priority is given to simplicity of description. Further, it goes without saying that the present system can be configured regardless of whether an optical or coaxial cable is used as the transmission cable.

【００２４】図３は、本発明によるアクセス方式を詳し
く説明するために、センタおよび中継装置ならびにＨＴ
の各双方向通信部の機能を示した機能ブロック図であ
る。センタ１の第１の双方向通信部１０２は、第１のデ
ータ確認手段１２１と、第１の上り信号受信手段１２２
と第１の下り信号出力手段１２３と、第１のデータ記憶
手段１２４とから構成され、中継装置２の第２の双方通
信部２０２は、第２のデータ確認手段２２１と、第２の
上り信号受信手段２２２と、第２の下り信号出力手段２
２３と、第２のデータ記憶手段２２４と、第２の上り信
号出力手段２２５と、第１の下り信号受信手段２２６と
から構成される。さらに、ＨＴ３の第３の双方向通信手
段３０２は、受信信号解析手段３２１と、第３のデータ
記憶手段３２４と、第１の上り信号出力手段３２５と、
第２の下り信号受信手段３２６と、上り出力制御手段３
２７と、受付確認手段３２８とから構成される。FIG. 3 illustrates a center and a relay device and an HT in order to explain the access method according to the present invention in detail.
3 is a functional block diagram showing the function of each bidirectional communication unit of FIG. The first bidirectional communication unit 102 of the center 1 includes a first data confirmation unit 121 and a first upstream signal reception unit 122.
And the first downlink signal output means 123 and the first data storage means 124. The second both-side communication unit 202 of the relay device 2 includes the second data confirmation means 221 and the second upstream signal. Reception means 222 and second downlink signal output means 2
23, second data storage means 224, second upstream signal output means 225, and first downstream signal reception means 226. Further, the third two-way communication means 302 of the HT3 includes a received signal analysis means 321, a third data storage means 324, a first upstream signal output means 325,
Second downlink signal receiving means 326 and uplink output control means 3
27 and reception confirmation means 328.

【００２５】加入者端末３０２は、同軸ケーブル５から
送られて来るフレームを第２の下り信号受信手段３２６
によって受信する。受信したデータは、受信信号解析手
段３２１に送られる。このとき情報／要求エリアに含ま
れるデータは、受付加入者端末アドレスが自分のアドレ
スか他人のアドレスかで違う意味を持つように設定され
ている。例えば、受付加入者端末アドレスが自分のアド
レスの場合、情報／要求エリアに含まれるデータはアク
セス要求送信許可の意味を持つデータであり、受付加入
者端末アドレスが他人のアドレスの場合、情報／要求エ
リアに含まれるデータはビジー状態を表すデータである
と受信信号解析手段３２１によって認識される。受信信
号解析手段３２１は、アクセス要求送信許可を認識した
場合、中継装置から加入者までの最大の伝送遅延時間か
ら自局加入者端末の伝送遅延時間を引いた残りの時間だ
け経過した後、加入者からの要求内容を表すデータを第
３のデータ記憶手段３２４から読み出し、第１の上り信
号出力手段３２５に出力する。The subscriber terminal 302 receives the frame sent from the coaxial cable 5 from the second downlink signal receiving means 326.
To receive by. The received data is sent to the received signal analysis means 321. At this time, the data contained in the information / request area is set so that the accepting subscriber terminal address has a different meaning depending on whether it is the own address or the address of another person. For example, if the receiving subscriber terminal address is his / her own address, the data contained in the information / request area is data having the meaning of permission of access request transmission, and if the receiving subscriber terminal address is another person's address, the information / request The reception signal analysis unit 321 recognizes that the data included in the area is data indicating a busy state. When recognizing the access request transmission permission, the reception signal analysis means 321 joins after the remaining time after subtracting the transmission delay time of the own station subscriber terminal from the maximum transmission delay time from the relay device to the subscriber, The data representing the request content from the person is read from the third data storage means 324 and output to the first upstream signal output means 325.

【００２６】上りデータのフレームフォーマットを図６
（Ａ）に、下りデータのフレームフォーマットを図６
（Ｂ）に示す。フレームは、全てフレームスタート記号
で始まり、フレーム終了記号で終了することとし、フレ
ームチェックシーケンスを調査することによって、デー
タ誤りや信号の衝突を検出できる構成となっている。The frame format of upstream data is shown in FIG.
FIG. 6A shows a frame format of downlink data.
It shows in (B). All frames start with a frame start symbol and end with a frame end symbol, and by examining the frame check sequence, data errors and signal collisions can be detected.

【００２７】第１の上り信号出力手段３２５は、受信信
号解析手段３２１から受け取ったデータで、図６（Ａ）
に示すフレームを作成し、上り出力制御手段３２７を通
してセンタへ要求データを出力する。上り信号出力手段
３２５がセンタへ要求データを出力した後、第２の下り
信号受信手段３２６が受信した信号に基づいて受信信号
解析手段３２１によって認識されたデータが要求データ
送信許可信号でなかった場合、自局加入者端末の発した
要求は受け付けられなかったことになり、再送信を行な
わなければならない。再送信要求は、受信信号解析手段
３２１が認識する情報／要求データがビジー信号からア
イドル信号に変化した時点で、受信信号解析手段３２１
から受付確認手段３２８に対し送信される。The first upstream signal output means 325 is the data received from the received signal analysis means 321 and is shown in FIG.
The frame shown in (1) is created, and the request data is output to the center through the upstream output control means 327. When the data recognized by the reception signal analysis means 321 based on the signal received by the second downlink signal receiving means 326 is not the request data transmission permission signal after the up signal output means 325 outputs the request data to the center. , The request issued by the local station subscriber terminal has not been accepted and must be retransmitted. The retransmission request is received signal analysis means 321 when the information / request data recognized by reception signal analysis means 321 changes from a busy signal to an idle signal.
From the reception confirmation means 328.

【００２８】受付確認手段３２８は、再送信要求を受信
すると、乱数を発生させて、その結果得られる数字に応
じたタイミングで上り信号出力手段３２５に対し、再送
信のタイミングを送信する。第１の上り信号出力手段３
２５は再送信タイミング信号を得た時点で、先に送信し
たフレームを自己のメモリから取り出し再び送信する。
但し、新たに加入者からの要求があった場合はこの限り
ではない。Upon receipt of the retransmission request, the acceptance confirmation means 328 generates a random number and transmits the retransmission timing to the upstream signal output means 325 at a timing corresponding to the number obtained as a result. First upstream signal output means 3
When 25 receives the retransmission timing signal, it retrieves the previously transmitted frame from its own memory and retransmits it.
However, this does not apply if there is a new request from the subscriber.

【００２９】ここでランダムなタイミングの発生につい
て請求項５を例にとって具体的な説明を加える。図７
（Ｂ）に示すように１フレームを５つのスロットに分
け、このスロットに１から５までの番号を付ける。番号
３のスロットを基準として±２スロットの範囲で乱数を
作成すれば１フレームの内に５つのポイントでのランダ
ムアクセスタイミングが得られる。このスロット内に納
まるように加入者端末からの上り信号出力タイミングを
制御するのも受付確認手段３２８である（図７（Ｂ）参
照、請求項６は図７（Ｃ）参照）。Here, a concrete description will be given of the occurrence of the random timing, taking claim 5 as an example. Figure 7
As shown in (B), one frame is divided into five slots, and the slots are numbered from 1 to 5. If random numbers are generated within the range of ± 2 slots with reference to the slot of number 3, random access timing at 5 points can be obtained in one frame. The reception confirmation means 328 also controls the output timing of the upstream signal from the subscriber terminal so that the reception signal is stored in this slot (see FIG. 7B, claim 6 refers to FIG. 7C).

【００３０】上り出力制御手段３２７は、受信信号解析
手段３２１がビジーまたはアイドル或いは要求許可信号
を認識した場合に出力する制御信号に応じて、上り出力
制御手段３２７の出力と上り信号用同軸ケーブルとの切
離し或いは接続を行なうスイッチである。ビジーの場合
は切離し、アイドルまたは要求許可信号の場合は接続で
ある。The upstream output control means 327 selects the output of the upstream output control means 327 and the upstream signal coaxial cable according to the control signal output when the reception signal analysis means 321 recognizes the busy or idle or request permission signal. It is a switch for disconnecting or connecting. Disconnected if busy, connected if idle or request grant signal.

【００３１】ＨＴ３０２から同軸ケーブル５を通して送
信された上り信号は、受信停止手段２２７を通過して第
２の上り信号受信手段２２２によって受信される。上り
信号がアクセス要求信号であった場合、発信元加入者端
末アドレスを２Ｂｙｔｅとし、要求内容の１Ｂｙｔｅお
よび付随するデータとして次回送信するフレームの長さ
を表す情報の１Ｂｙｔｅを足して合計４Ｂｙｔｅが実質
のデータとなる。このデータは一旦無条件に第２のデー
タ記憶手段２２４の所定のアドレスに記憶される。この
ときの記憶には上り信号受信手段２２２から直接データ
記憶手段２２４に記憶するＤＭＡ（Direct Memory Acce
ss）を使用することも可能である。上り信号受信手段２
２２は、フレームチェックシーケンスを受信した後、直
ちにデータ誤りを調査する。データ誤りを検出した時点
で第２の上り信号受信手段２２２は、第２のデータ確認
手段２２１に対し異常データ受信の合図を送信する。異
常データ受信の合図があった場合は受信したデータは廃
棄される。第２のデータ確認手段２２１は、いわゆるＣ
ＰＵであり、種々のデータの解析ならびに周辺の諸機能
に対し命令を送信し制御する。The upstream signal transmitted from the HT 302 through the coaxial cable 5 passes through the reception stopping means 227 and is received by the second upstream signal receiving means 222. If the upstream signal is an access request signal, the source subscriber terminal address is set to 2 Bytes, and 1 Byte of the request content and 1 Byte of information indicating the length of the frame to be transmitted next as additional data are added to give a total of 4 Bytes. It becomes data. This data is temporarily stored unconditionally at a predetermined address of the second data storage means 224. At this time, the upstream signal receiving means 222 directly stores the data in the data storage means 224 (DMA (Direct Memory Acce)).
ss) can also be used. Upstream signal receiving means 2
22 checks for data errors immediately after receiving the frame check sequence. At the time when the data error is detected, the second upstream signal receiving means 222 transmits a signal of abnormal data reception to the second data confirmation means 221. If there is a signal to receive abnormal data, the received data is discarded. The second data confirmation means 221 is a so-called C
It is a PU that analyzes and analyzes various data and sends commands to various peripheral functions to control them.

【００３２】上記異常データ受信の合図を受信しなかっ
た第２のデータ確認手段２２１は、第２の上り信号受信
手段２２２からのフレーム受信終了の合図と共に第２の
データ記憶手段２２４から要求内容を読み出し、そのデ
ータの表す内容の判定を行なう。ここで要求内容はアク
セス要求であると判断されるので、第２のデータ記憶手
段から要求内容に付随するデータを読み込んだ場合、そ
のデータは次に送られて来るフレーム長の情報データで
あることがわかるためこの情報を解析して、ビジーフレ
ームの長さを決定する（図７参照）。The second data confirmation means 221 which has not received the above-mentioned abnormal data reception signal sends a request content from the second data storage means 224 together with a signal of the end of frame reception from the second upstream signal reception means 222. The data is read and the content represented by the data is determined. Here, since the request content is determined to be an access request, when the data accompanying the request content is read from the second data storage means, the data is the information data of the frame length to be sent next. Therefore, the length of the busy frame is determined by analyzing this information (see FIG. 7).

【００３３】ここで、第２のデータ確認手段２２１は、
図６（Ｂ）で表す下り信号に、読み出した発信元加入者
端末アドレスを使い、情報／要求エリアに発信元加入者
端末にとってはアクセス要求許可の意味を持つデータで
あり他の加入者端末にとってはビジー状態を表すデータ
を挿入して下り信号フレームを作成し、これを第２の９
下り信号出力手段２２３に送信する。この時第２のデー
タ確認手段２２１は受信停止手段２２７に対し受信停止
命令を送信する。受信停止手段２２７は、スイッチであ
り受信停止命令を受けると、同軸ケーブル５と上り信号
受信手段２２２を結ぶ回線を切離し、遅延によってビジ
ー状態の時に送られて来る上り信号をカットする。Here, the second data confirmation means 221 is
For the downlink signal shown in FIG. 6B, the read source subscriber terminal address is used, and in the information / request area, it is data having the meaning of access request permission for the source subscriber terminal and for the other subscriber terminals. Inserts the data indicating the busy state to create a downlink signal frame, which is
It transmits to the downlink signal output means 223. At this time, the second data confirmation means 221 sends a reception stop command to the reception stop means 227. The reception stopping means 227 is a switch and, when receiving the reception stop command, disconnects the line connecting the coaxial cable 5 and the upstream signal receiving means 222, and cuts the upstream signal sent in the busy state due to the delay.

【００３４】第２の下り信号出力手段２２３は、１Ｂｙ
ｔｅづつパラレルデータを上記第２のデータ確認手段２
２１から受け取ると、このデータをシリアルデータに変
換し、下り信号伝送用の同軸ケーブル５へ出力する。当
然のことながら、出力データにはフレームスタート記号
とフレーム終了記号、フレームチェックシーケンスは付
加された形態で出力される（図６（Ｂ）参照）。The second downlink signal output means 223 has 1By
The second parallel data confirmation means 2 for each parallel data
When it is received from 21, it converts this data into serial data and outputs it to the coaxial cable 5 for downlink signal transmission. As a matter of course, the output data is output in a form in which the frame start symbol, the frame end symbol, and the frame check sequence are added (see FIG. 6B).

【００３５】この送信許可信号を受けたＨＴの双方向通
信部３０２は、次に加入者の要求の種類を表すデータを
アクセス要求と同様にして中継装置の双方向通信部２０
２へ送信する。第２のデータ確認手段２２１は、このデ
ータ内容の解析を行ない、チャネル選択等の処理を行な
う。このとき要求内容がデマンドサービスであった場合
は、センタに対して要求を伝達しなければならない。Upon receiving the transmission permission signal, the HT bidirectional communication unit 302 next processes the data indicating the type of the subscriber's request in the same manner as the access request, and the bidirectional communication unit 20 of the relay device.
Send to 2. The second data confirmation means 221 analyzes this data content and performs processing such as channel selection. At this time, if the request content is a demand service, the request must be transmitted to the center.

【００３６】センタの双方向通信部１０２は、大きく
は、複数の中継装置とデータの送受信を行なうと共に、
データの収集、保管、計算などのＣＡＴＶシステムの運
営、機器管理に関する全てのデータ処理を行なうが、本
実施例では双方向通信についてのみ説明をするものであ
る。センタのデータ確認手段１２１は、中継装置の双方
向通信部２０２に保持された加入者からのデマンドサー
ビス要求を第１の下り信号出力手段１２３を使ったポー
リングによって検出する。第１の下り信号出力手段１２
３からのポーリング信号は、中継装置の双方向通信部２
０２内の第１の下り信号受信手段２２６で受信され、第
２のデータ確認手段２２１で判別される。ポーリング信
号を認識した第２のデータ確認手段２２１は、加入者か
らのデマンドサービス要求がある場合には、その要求内
容を、無い場合には要求なしを意味するデータをセンタ
の双方向通信部１０２に対し送信する。The two-way communication unit 102 of the center generally sends and receives data to and from a plurality of relay devices, and
Although all data processing relating to CATV system operation and device management such as data collection, storage, and calculation is performed, only bidirectional communication will be described in the present embodiment. The data confirmation means 121 of the center detects the demand service request from the subscriber held in the two-way communication section 202 of the relay device by polling using the first downlink signal output means 123. First downlink signal output means 12
The polling signal from the relay device 3 is sent to the bidirectional communication unit 2 of the relay device.
The signal is received by the first downlink signal receiving means 226 in 02 and is discriminated by the second data confirming means 221. The second data confirmation unit 221 that recognizes the polling signal, when there is a demand service request from the subscriber, transmits the request content, and when there is no demand service, the data that means no request is transmitted to the two-way communication unit 102 of the center. Send to.

【００３７】センタの第１の上り信号受信手段１２２
は、中継装置からの上り信号を受信し第１のデータ確認
手段１２１に出力する。このときデータはパラレルデー
タに変換される。第１のデータ確認手段１２１では上り
信号の内容を解析し、要求のある場合には対応した処理
回路に内容に応じた命令を出力する。各処理回路は、処
理終了と共に第１のデータ確認手段１２１に対し処理の
終了を伝達する。第１のデータ確認手段１２１は、この
信号を受け取ると第１の下り信号出力手段１２３に対し
処理終了を意味するデータを送信する。第１の下り信号
出力手段１２３は、この信号をシリアルデータ変換し中
継装置に伝送する。The first upstream signal receiving means 122 of the center
Receives the upstream signal from the relay device and outputs it to the first data confirmation means 121. At this time, the data is converted into parallel data. The first data confirmation means 121 analyzes the content of the upstream signal, and outputs a command according to the content to the corresponding processing circuit when there is a request. Each processing circuit notifies the first data confirmation means 121 of the end of the processing when the processing is completed. Upon receiving this signal, the first data confirmation means 121 transmits data indicating the end of processing to the first downlink signal output means 123. The first downlink signal output means 123 converts this signal into serial data and transmits it to the relay device.

【００３８】中継装置の第２のデータ確認手段２２１
は、処理終了信号を認識すると、第２の下り信号出力手
段２２３に対しアイドル状態を意味するデータを出力す
る。第２の下り信号出力手段２２３は、アイドル状態を
意味するデータを全てのＨＴに対し一斉送信する。各Ｈ
Ｔではアイドル信号を受信すると再びアクセス要求を出
力することになる。Second data confirmation means 221 of the relay device
When recognizing the processing end signal, outputs the data indicating the idle state to the second downlink signal output means 223. The second downlink signal output means 223 broadcasts data indicating an idle state to all HTs. Each H
At T, when the idle signal is received, the access request is output again.

【００３９】次にシステム構成は従来と同じであるが、
アクセス方式の途中切り替えを行なった場合の実施例に
ついて説明する。中継装置の双方向通信部２０２におけ
る第２のデータ確認手段２２１は、第２の上り信号受信
手段２２２から異常データ受信の合図を３度続けて受信
した場合、複数の加入者がランダムにアクセス要求を出
す上記説明のランダムコール方式より、センタが全ての
加入者端末を１台づつポーリングするポーリング方式に
アクセス方式の切り替えを行なう。これは第２のデータ
確認手段２２１が自らのアクセス方式のプログラム読み
出し位置の変更を行なうことによって実現される。第２
のデータ確認手段２２１の内部でポーリング方式にアク
セス方式が切り替わると、第２のデータ確認手段２２１
は、下り信号のフレーム中にある情報／要求データの内
容をポーリングを表すデータに切り替える。これによっ
てセンタ側のアクセス方式の変換が完了する（図６
（Ｃ）参照）。Next, the system configuration is the same as the conventional one,
An example in which the access method is switched midway will be described. When the second data confirmation means 221 in the two-way communication unit 202 of the relay device receives the abnormal data reception signal from the second upstream signal reception means 222 three times in a row, a plurality of subscribers randomly make access requests. The access method is switched to the polling method in which the center polls all subscriber terminals one by one from the random call method described above. This is realized by the second data confirmation means 221 changing the program read position of its own access method. Second
When the access method is switched to the polling method inside the data confirming means 221 of the above, the second data confirming means 221
Switches the content of the information / request data in the frame of the downlink signal to data representing polling. This completes the conversion of the access method on the center side (Fig. 6).
(See (C)).

【００４０】ＨＴ側では、受信信号解析手段３２１が、
中継装置からのフレームがポーリングであることを解析
すると、第１の上り信号出力手段３２５に対しポーリン
グに対する回答フレームを図６（Ａ）に従って出力する
ようにデータを送信する。この場合加入者からの要求が
無いときでも要求内容として要求無しを表すデータを送
信する。On the HT side, the received signal analysis means 321
When it is analyzed that the frame from the relay device is polling, data is transmitted to the first upstream signal output means 325 so as to output a reply frame to the polling according to FIG. 6 (A). In this case, even if there is no request from the subscriber, data indicating no request is transmitted as the request content.

【００４１】次に本発明係る他の実施例による上記ラン
ダムコール方式を用いたシステムであり、とくにＶＯＤ
などのデマンドサービスに優れたシステムについて説明
する。図１に示すシステムは、従来のシステム構成に比
べより多数の加入者に対する迅速なサービスが可能であ
るという点において優れたシステム概念図を示してい
る。このシステムのシステム上の最大の違いは、センタ
から複数の中継装置に対して送信される信号に変調や合
成が一切なされないことである。Next, a system using the above random call method according to another embodiment of the present invention will be described.
Describes a system that excels in demand services such as. The system shown in FIG. 1 shows an excellent system conceptual diagram in that it can provide quick service to a larger number of subscribers than the conventional system configuration. The biggest systematic difference of this system is that the signal transmitted from the center to the plurality of relay devices is not modulated or combined at all.

【００４２】すなわち、このシステムは、センタ１と、
複数の中継装置２〜２ｎと、複数の加入者宅３〜３ｎか
ら構成され、中継装置２と加入者宅とは加入者終端装置
３１０〜３１０−ｎによって接続されている。センタ１
は、第１の双方向通信部１０２と、システム監視部１０
３と、システム管理部１０４、ならびに、ＢＳやＣＳ及
び地上放送ならびに一般放送等の再送信サービス手段
と、所望のビデオ情報をＡＴＭスイッチを介して送り出
すビデオサーバとから構成される。各々の中継装置２
は、それぞれ、周波数多重回路１１０と、第２の双方向
通信部２０２と、送受信機２０３とから構成される。各
加入者宅３は、複数のホームターミナル（ＨＴ）３００
〜３００−２と、モニタ３０１とから構成され、各ＨＴ
３００は、それぞれ第３の双方向通信部３０２と、リモ
コン受信部３０３と、合分波器３０４と、チューナ部か
ら構成される。That is, this system includes a center 1,
It is composed of a plurality of relay devices 2 to 2n and a plurality of subscriber homes 3 to 3n, and the relay device 2 and the subscriber homes are connected by subscriber terminating devices 310 to 310-n. Center 1
Is the first bidirectional communication unit 102 and the system monitoring unit 10.
3, a system management unit 104, a retransmission service means for BS, CS, terrestrial broadcasting, general broadcasting, etc., and a video server for sending desired video information through an ATM switch. Each relay device 2
Are each composed of a frequency multiplexing circuit 110, a second bidirectional communication unit 202, and a transceiver 203. Each subscriber home 3 has a plurality of home terminals (HT) 300.
~ 300-2 and monitor 301, each HT
Each 300 includes a third bidirectional communication unit 302, a remote control receiving unit 303, a multiplexer / demultiplexer 304, and a tuner unit.

【００４３】再送信サービスの映像であるＢＳやＣＳ及
び地上放送ならびに一般放送などは、分配増幅器７を通
して各中継装置に送られる。デマンドサービスにおいて
は、各中継装置に許容される回線の数だけセンタの交換
器と接続された専用回線が割り当てられる。専用回線
は、交換器の能力に応じて設けることが可能であり、こ
の数に到るまで中継装置を設けることはデマンドサービ
スを行う上で非常に意義が有る。BS, CS, terrestrial broadcasting, general broadcasting and the like of the video of the retransmission service are sent to each relay device through the distribution amplifier 7. In the demand service, dedicated lines connected to the exchanges in the center are allocated by the number of lines permitted for each relay device. The dedicated line can be provided according to the capacity of the exchange, and it is very significant to provide the demand device up to this number in order to perform the demand service.

【００４４】中継装置内の周波数多重回路２１０で変調
及び合成された信号は、送受信器２０３を通り加入者終
端装置３１０に送られる。加入者終端装置３１０は、送
受信器３０５で受信した信号を、合分配器３０６を経由
して複数の加入者に対し分配送信する。ＨＴの中にチュ
ーナ部を持つことによって、再送信サービスなどの要求
は、中継装置やセンタに対してのアクセスを必要とせず
待ち時間のない迅速な対応が行なわれる。また中継装置
２に上る信号は上記説明を施したランダムコール方式を
用いて行なわれるので、センタからのデータ要求に対し
て送信されるデータ（視聴率調査や利用状況を表すデー
タなど）以外は、加入者からの要求であるデマンドサー
ビスに関する要求となり、上り信号が大幅に減少し、中
継装置内の双方向通信部にかかる負荷は、軽減される。The signal modulated and combined by the frequency multiplexing circuit 210 in the repeater is sent to the subscriber terminating device 310 through the transmitter / receiver 203. The subscriber terminal device 310 distributes and transmits the signal received by the transmitter / receiver 305 to a plurality of subscribers via the combiner / distributor 306. By having a tuner unit in the HT, a request for a retransmission service or the like can be promptly handled without requiring access to the relay device or the center and without waiting time. Further, since the signal sent to the relay device 2 is performed by using the random call method described above, except for the data transmitted in response to the data request from the center (data indicating the audience rating, the usage status, etc.), The demand for the demand service is a request from the subscriber, the upstream signal is significantly reduced, and the load on the two-way communication unit in the relay device is reduced.

【００４５】加入者がＶＯＤサービスを希望した場合に
ついて考えると、加入者からの要求は、ＨＴにおいてリ
モコン受信部３０３を通り双方向通信部３０２において
その内容が解析される。このときＨＴ内で処理が可能な
要求の場合は、第３の双方向通信部３０２からＨＴ内の
関連する処理装置に対し処理要求信号が出力されるが、
ＶＯＤの場合は、センタの処理を必要とするデマンドサ
ービスであるので、加入者の要求内容は、双方向通信用
のフレームフォーマットに成形される。この信号は、そ
の後加入者要求信号として出力される。Considering a case where the subscriber desires the VOD service, the content of the request from the subscriber passes through the remote control receiving unit 303 in the HT and is analyzed in the bidirectional communication unit 302. At this time, if the request can be processed in the HT, a processing request signal is output from the third two-way communication unit 302 to the related processing device in the HT.
In the case of VOD, which is a demand service that requires processing by the center, the content requested by the subscriber is formed into a frame format for two-way communication. This signal is then output as the subscriber request signal.

【００４６】中継装置内の第２の双方向通信部２０２
は、この信号を受信し、正常であることを確認すると他
の加入者からの受信を停止し、要求された処理に移る。
このとき従来のシステム構成では、中継装置に対する要
求は、再送信チャネルの選局などの要求も含まれるの
で、全体の要求数が多くなって信号が重なってしまい、
一旦キャンセルされる確率が高いが、この実施例による
システムでは、再送信チャネルの選択などの要求などは
含まれないので、キャンセル確率は非常に低くなり、要
求に対する迅速な処理が可能となる。Second bidirectional communication section 202 in the relay device
When it receives this signal and confirms that it is normal, it stops receiving from other subscribers and moves to the requested processing.
At this time, in the conventional system configuration, the request to the relay device also includes a request for selecting a retransmission channel, so that the total number of requests increases and signals overlap,
Although the probability of being canceled once is high, the system according to this embodiment does not include a request such as selection of a retransmission channel, so the cancellation probability is very low, and a prompt process for the request is possible.

【００４７】中継装置内の第２の双方向通信部２０２で
は、デマンドサービス用の空き回線の管理も行なってお
り、要求のあった時点で空き回線が存在した場合には要
求したＨＴにＶＯＤ受信許可としてその回線番号をキー
として送信することによってその空き回線を割当てる一
方で、センタのＡＴＭ交換器に対してもビデオサーバか
らの映像出力先として回線番号を指定する。上記回線番
号やビデオサーバに指定する番組コードなどのデータ
は、加入者から中継装置に送信された処理要求データの
中に含まれており、中継装置内の第２の双方向通信部２
０２で一旦保存しセンタからのポーリングに対する信号
に含めてセンタ内の第１の双方向通信部１０２に送信す
る（図５参照）。The second two-way communication section 202 in the relay device also manages an empty line for the demand service, and if there is an empty line at the time of the request, it receives VOD at the requesting HT. As a permission, the free line is allocated by transmitting the line number as a key, while the line number is designated as the image output destination from the video server to the ATM switch of the center. The data such as the line number and the program code specified for the video server are included in the processing request data transmitted from the subscriber to the relay device, and the second bidirectional communication unit 2 in the relay device is included.
In 02, it is temporarily stored and included in a signal for polling from the center and transmitted to the first two-way communication unit 102 in the center (see FIG. 5).

【００４８】センタの双方向通信部１０２では、ポーリ
ングに対応して送信された信号を解析し、番組コードと
空き回線番号を認識するとビデオサーバ及びＡＴＭスイ
ッチに対し処理命令を出力する。この結果センタから
は、変調されない映像信号データが中継装置に対して送
信される。ここでセンタにとっては映像データを空き回
線に出力するだけの行為であるので、理論的には回線が
存在すればＡＴＭスイッチの能力の分だけ映像データを
出力することが可能である。変調及び合成を行なう周波
数多重回路では、伝送帯域上の問題から回線数をある一
定以上増やすことは不可能であるが、中継装置と共に周
波数多重回路を増やすことによって新たな伝送帯域を作
ることができ、結果として回線数を増やすことができ
る。The bidirectional communication section 102 of the center analyzes the signal transmitted in response to the polling, and when it recognizes the program code and the vacant line number, outputs a processing command to the video server and the ATM switch. As a result, the video signal data that is not modulated is transmitted from the center to the relay device. Here, since the center only outputs the video data to the idle line, theoretically, if the line exists, the video data can be output by the capacity of the ATM switch. With a frequency multiplexing circuit that performs modulation and synthesis, it is not possible to increase the number of lines above a certain level due to problems with the transmission band, but a new transmission band can be created by increasing the number of frequency multiplexing circuits together with the repeater. As a result, the number of lines can be increased.

【００４９】以上のように、上記本発明によるシステム
は、ランダムコール方式による高速アクセス及び中継装
置内で周波数多重を施すことによるサービス用チャネル
回線数の増加によって、多数の加入者を対象とするデマ
ンドサービスに最適な環境を提供することができる。本
発明のアクセス方式の内、センタと中継装置の間の通信
方式が上記説明したランダムコール方式とした場合にお
いては、センタと中継装置の関係は中継装置とＨＴの関
係に等しく動作はそれに準ずる。図８は実際にシステム
を作成する場合に考えられるＨＴの双方向通信部の具体
的な構成例である。第３図における受信信号解析手段３
２１および受付確認手段３２８は、マイクロコンピュー
タ４０にプログラムメモリ４２、アドレスデコーダ４１
を組み合わせた構成で代用される。第１の上り信号出力
手段３２５と第２の下り信号受信手段３２６は既存の非
同期シリアル通信回路４４またはＩＣで代用可能であ
り、上り出力制御手段は、公知のスイッチ回路４５であ
る。中継装置２及びセンタ１における双方向通信部２０
２、１０２においてもデータ確認手段２２１、１２１を
マイクロコンピュータ、受信停止手段２２７をスイッチ
回路とすれば何ら変わらぬ構成で作成できる。As described above, in the system according to the present invention, the high-speed access by the random call system and the increase in the number of service channel lines by performing the frequency multiplexing in the repeater increase the demand for many subscribers. An optimal environment for services can be provided. In the access system of the present invention, when the communication system between the center and the relay device is the random call system described above, the relationship between the center and the relay device is equal to the relationship between the relay device and the HT, and the operation is in accordance with that. FIG. 8 is a specific configuration example of the bidirectional communication unit of the HT that can be considered when actually creating a system. Received signal analysis means 3 in FIG.
21 and the acceptance confirmation means 328, the microcomputer 40, the program memory 42, the address decoder 41
It is substituted by the composition which combined. The first upstream signal output means 325 and the second downstream signal reception means 326 can be replaced by the existing asynchronous serial communication circuit 44 or IC, and the upstream output control means is a known switch circuit 45. Bidirectional communication unit 20 in relay device 2 and center 1
In the case of 2 and 102 as well, if the data confirming means 221 and 121 are microcomputers and the reception stopping means 227 is a switch circuit, they can be created with no change.

【００５０】以上のように、上記本発明によるシステム
は、ランダムコール方式による高速アクセス及び中継装
置内で周波数多重を施すことによるサービス用チャネル
回線数の増加によって、多数の加入者を対象とするデマ
ンドサービスに最適な環境を提供することができる。As described above, the system according to the present invention demands a large number of subscribers due to high-speed access by the random call method and an increase in the number of service channel lines by performing frequency multiplexing in the repeater. An optimal environment for services can be provided.

【００５１】本発明のアクセス方式の内、センタと中継
装置の間の通信方式が上記説明したランダムコール方式
とした場合においては、センタと中継装置の関係は中継
装置とＨＴの関係に等しく動作はそれに準ずる。In the access system of the present invention, when the communication system between the center and the relay device is the random call system described above, the relationship between the center and the relay device is the same as the relationship between the relay device and the HT. According to that.

【００５２】図８は、実際にシステムを作成する場合に
考えられるＨＴの双方向通信部の具体的な構成例を示
す。図３における受信信号解析手段３２１および受付確
認手段３２８は、マイクロコンピュータ４０にプログラ
ムメモリ４２、アドレスデコーダ４１を組み合わせた構
成で代用される。第１の上り信号出力手段３２５と第２
の下り信号受信手段３２６は既存の非同期シリアル通信
回路４４またはＩＣで代用可能であり、上り出力制御手
段は、公知のスイッチ回路４５である。中継装置２及び
センタ１における双方向通信部２０２、１０２において
もデータ確認手段２２１、１２１をマイクロコンピュー
タ、受信停止手段２２７をスイッチ回路とすれば何ら変
わらぬ構成で作成出来る。FIG. 8 shows a concrete configuration example of the bidirectional communication unit of the HT that can be considered when actually creating a system. The received signal analysis means 321 and the acceptance confirmation means 328 in FIG. 3 are substituted by a configuration in which the microcomputer 40 is combined with a program memory 42 and an address decoder 41. The first upstream signal output means 325 and the second
The existing asynchronous serial communication circuit 44 or IC can be substituted for the downstream signal receiving means 326 of FIG. 1, and the upstream output control means is a known switch circuit 45. Even in the two-way communication units 202 and 102 in the relay device 2 and the center 1, if the data confirmation means 221 and 121 are microcomputers and the reception stopping means 227 is a switch circuit, they can be created with no change.

【００５３】[0053]

【発明の効果】以上説明したように本発明によれば、中
継装置が対応するのは何らかの要求を持った加入者端末
のみであり、要求に対し素早い対応をすることが可能で
あり、複数の要求が衝突した場合においても加入者端末
自信がランダムなタイミングで再送信を行なうので、再
衝突の確立を軽減することとなり効率のよい要求処理が
できる。また、上記手法による高速処理と中継装置内に
おいて信号の変調及び合成を行なうことによって、高速
なアクセスとデマンドサービス専用回線を増やすことが
可能でありデマンドサービスに最適な環境を提供するこ
とができる。As described above, according to the present invention, the relay device supports only the subscriber terminal having any request, and can quickly respond to the request. Even if requests collide, the subscriber terminal retransmits at random timing, which reduces the possibility of re-collision and enables efficient request processing. Further, by performing high-speed processing by the above method and modulating and synthesizing signals in the relay device, it is possible to increase high-speed access and dedicated lines for demand service, and it is possible to provide an optimal environment for demand service.

[Brief description of drawings]

【図１】本発明によるＣＡＴＶシステムの基本構成図。FIG. 1 is a basic configuration diagram of a CATV system according to the present invention.

【図２】従来の代表的な双方向ＣＡＴＶシステムの基本
構成図。FIG. 2 is a basic configuration diagram of a conventional representative bidirectional CATV system.

【図３】本発明によるＣＡＴＶシステムにおける双方向
通信部の機能概念図。FIG. 3 is a functional conceptual diagram of a bidirectional communication unit in the CATV system according to the present invention.

【図４】従来のポーリング方式によるアクセス動作シー
ケンス。FIG. 4 is an access operation sequence according to a conventional polling method.

【図５】本発明におけるアクセス方式の基本動作シーケ
ンス。FIG. 5 is a basic operation sequence of an access method according to the present invention.

【図６】本発明による通信データのフレームフォーマッ
ト。FIG. 6 is a frame format of communication data according to the present invention.

【図７】本発明のアクセスタイミングを示した図。FIG. 7 is a diagram showing access timing of the present invention.

【図８】本発明における加入者端末双方向通信部の具体
的構成を示すブロック図。FIG. 8 is a block diagram showing a specific configuration of a subscriber terminal two-way communication unit in the present invention.

[Explanation of symbols]

１センタ２中継装置３加入者端末（通信部）４光ファイバケーブル５同軸ケーブル７分配増幅器４０マイクロコンピュータ４１アドレスデコーダ４２プログラム格納メモリ４３データ記憶メモリ４４非同期シリアル通信回路４５スイッチ回路１０１ヘッドエンド１０２第１の双方向通信部１１０周波数多重回路１１１送受信器１２１第１のデータ確認手段１２２第１の上り信号受信手段１２３第１の下り信号出力手段１２４第１のデータ記憶手段２００加入者制御部２０２第２の双方向通信部２０４合分配器２０５送受信器２２１第２のデータ確認手段２２３第２の下り信号出力手段２２４第２のデータ記憶手段２２５第２の上り信号受信手段２２６第１の下り信号受信手段２２７受信停止手段３０１モニタ３０２第３の双方向通信部３０３リモコン受信部３０６合分配器３１０加入者終端装置３２１受信信号解析手段３２４第３のデータ記憶手段３２５第１の上り信号出力手段３２６第２の下り信号受信手段３２７上り出力制御手段３２８受付確認手段 1 Center 2 Relay Device 3 Subscriber Terminal (Communication Unit) 4 Optical Fiber Cable 5 Coaxial Cable 7 Distribution Amplifier 40 Microcomputer 41 Address Decoder 42 Program Storage Memory 43 Data Storage Memory 44 Asynchronous Serial Communication Circuit 45 Switch Circuit 101 Headend 102 No. 1 bidirectional communication unit 110 frequency multiplexing circuit 111 transmitter / receiver 121 first data confirmation means 122 first upstream signal receiving means 123 first downstream signal output means 124 first data storage means 200 subscriber control section 202 second Two-way communication unit 204 Combiner / distributor 205 Transmitter / receiver 221 Second data confirmation means 223 Second downlink signal output means 224 Second data storage means 225 Second upstream signal receiving means 226 First downstream signal reception Means 227 Reception stopping means 3 1 Monitor 302 Third Bidirectional Communication Unit 303 Remote Control Receiver 306 Combiner / Distributor 310 Subscriber Termination Device 321 Received Signal Analysis Means 324 Third Data Storage Means 325 First Upstream Signal Output Means 326 Second Downstream Signal Reception Means 327 Upstream output control means 328 Reception confirmation means

Claims

[Claims]

1. A two-way CATV two-way transmission network that includes a relay device between a center and a plurality of subscriber terminals, and transmits and receives signals to and from each other via the relay device. Between the relay device and the subscriber terminal, the relay device distributes and transmits a downlink signal indicating an idle state to all the subscriber terminals. , Receiving an access request signal transmitted at random timing from the subscriber terminal, and the received signal from the subscriber terminal collides with a signal transmitted from another subscriber terminal, causing communication failure. In this case, all the received signals from the subscriber terminal are invalidated, and if the access request signal from the subscriber terminal is normal, the requesting subscriber end A request data transmission permission signal is given to the end, the data transmitted from the subscriber terminal corresponding to this is temporarily stored in the data storage means, and the data is transmitted in response to polling from the center, Also, in response to a request from the center, the corresponding processing including the transmission to the subscriber terminal is performed, and on the other hand, when the subscriber terminal recognizes that the relay device is in the idle state, it performs random timing. The access request signal is repeatedly retransmitted until an access request is accepted and a request data transmission permission signal is received from the relay device, whereby only the subscriber terminal given the request data transmission permission signal is transmitted to the relay device. CAT characterized by performing bidirectional communication using a random call method
V access method in a two-way communication system.

2. A bidirectional CATV including a relay device between a center and a plurality of subscriber terminals, and transmitting and receiving signals to and from each other through the relay device using the same frequency band or the same time slot. In the two-way transmission network, the two-way communication is performed between the center and the relay device by using polling, and the relay device means an idle state between the relay device and the plurality of subscriber terminals. The downlink signal to be distributed is transmitted to all the subscriber terminals, and an access request signal transmitted at random timing from the subscriber terminal is received, and the signal from the received subscriber terminal is received from another subscriber terminal. If there is a communication failure due to collision with the transmitted signal, all the received signals from the above-mentioned subscriber terminal are invalidated and access from the subscriber terminal is required. If the request signal is normal, the request data transmission permission signal is given to the requesting subscriber terminal, and a signal notifying that the subscriber terminal is busy is transmitted to the other subscriber terminals. When the relay device recognizes that the relay device is in the idle state, the access request signal is accepted at the random timing within the period until the next idle signal is transmitted, and the request data transmission permission signal is transmitted from the relay device. Repeatedly retransmitting until receiving, while the other subscriber terminals that did not obtain the request permission signal, upon recognizing the signal indicating the busy state, invalidate the access request signal to be transmitted to the relay device, thereby Only the subscriber terminal to which the request data transmission permission signal is given in the two-way communication with the same frequency and the same time slot relays the above. Access method for two-way communication system CATV, characterized in that to perform bidirectional communication using a random-call for transmission to the location.

3. In a two-way communication between the relay device and the plurality of subscriber terminals, the relay device accepts an access request signal from the subscriber terminal, and at the same time, a busy signal transmitted from the relay device is transmitted. The C according to claim 1 or claim 2, characterized in that reception of all uplink inputs is suspended until the time reaches all the subscriber terminals.
An access method in an ATV two-way communication system.

4. In bidirectional communication between the relay device and the plurality of subscriber terminals, the downlink signal from the relay device includes the busy signal and the idle signal and is transmitted at fixed time intervals (frames). When the access request signal from the subscriber terminal is not accepted by the relay device during the next frame after transmitting the busy signal or the idle signal, the idle signal is transmitted again, while one of the subscriber terminals transmits the idle request signal. The access method in the CATV two-way communication system according to claim 2 or 3, wherein the busy signal is transmitted when the access request signal of (1) is accepted by the relay device.

5. The frame interval is divided into n (n-slots) into a time length (subslot) in which an upstream signal from the subscriber terminal is accommodated.
Is an integer), and the uplink signal from the subscriber terminal is transmitted in synchronization with any sub-slot, and the access request signal from the subscriber terminal generated in the same frame is a signal collision. 5. The access method in the CATV two-way communication system according to claim 2, wherein the access is canceled and retransmitted from the subscriber terminal.

6. The frame interval is divided into n (n) (n) time periods (subslots) in which an upstream signal from the subscriber terminal is accommodated.
Is a whole number), and the signal delay time proportional to the distance from the center of the subscriber terminal is used to assign specific sub-slots as transmission timings of the subscriber terminal groups divided into n groups having substantially the same delay time. The subscriber terminal group in the delay time period transmits an access request signal in a specific subslot of an arbitrary frame, and the access request signal from the subscriber terminal generated in the same frame is canceled as a signal collision and 5. The re-transmission from the subscriber terminal, wherein the re-transmission is performed from the subscriber terminal.
An access method in a CATV two-way communication system according to any one of 1.

7. In bidirectional communication between the relay device and the plurality of subscriber terminals, length information of signal data to be transmitted next in an access request signal which is an upstream signal from the subscriber terminal. Alternatively, processing time information is included, the relay device reads the information, and the length of the busy frame is changed so as to correspond to the length of the processing time calculated from the signal data. An access method in a CATV two-way communication system according to any one of claims 2 to 6.

8. The relay device receives an access request signal transmitted from the subscriber terminal, and determines whether the relay device collides with a signal transmitted from another subscriber terminal or is a normal signal. If there is a collision or communication failure, all the received access request signals are invalidated, and if the access request signals are invalidated at a certain rate or more, the relay device uses the access method. To the polling method, and transmits a signal indicating that all subscribers have been converted to the polling control method. The subscriber terminal receives / analyzes the control method conversion information included in the downlink signal, and transmits the uplink signal. To respond to polling from the relay device, and the relay device polls all subscriber terminals once. When the processing for the request from the subscriber terminal is completed, a signal for switching to an access method for accepting an access request signal from a random subscriber terminal is transmitted again, and the subscriber terminal receives / analyzes this control method conversion information. 8. The access method in the CATV two-way communication system according to claim 1, wherein the method is switched to a method of randomly transmitting an access request signal in response to a request from a subscriber. .

9. In a bidirectional CATV bidirectional transmission network that includes a relay device between a center and a plurality of subscriber terminals, and transmits and receives signals to and from each other via the relay device, the center and the relay device. In the meantime, the center distributes and transmits a downlink signal meaning an idle state to all the relay devices, and receives an access request signal transmitted at random timing from the relay device having a processing request from a subscriber, When the received signal from the relay device collides with a signal transmitted from another relay device and causes a communication failure, all the received signals from the relay device are invalidated, and If the access request signal is normal, a request data transmission permission signal is given to the requesting relay device, and the device waits for request data from the relay device. On the other hand, when the relay device recognizes that the center is in the idle state, the relay device repeatedly retransmits the access request signal at random timing until the access request is accepted and the request data transmission permission signal is received from the center. By the random call method in which only the relay device given the request data transmission permission signal by the above performs data transmission to the center, two-way communication is performed, while the relay device also operates between the relay device and the subscriber terminal. , While distributing and transmitting a downlink signal meaning an idle state to all the subscriber terminals, receiving an access request signal transmitted at random timing from the subscriber terminal, the received signal from the subscriber terminal is If there is a communication failure due to collision with a signal transmitted from another subscriber terminal, it will be received. When all the signals from the subscriber terminal are invalidated and the access request signal from the subscriber terminal is normal, a request data transmission permission signal is given to the requesting subscriber terminal, at which time the subscriber terminal is sent. The data transmitted from the terminal is temporarily stored in the data storage means, and in response to this, the data is transmitted to the center by the random call method as described above, and also to the subscriber terminal in response to the request from the center. When the subscriber terminal recognizes that the relay device is in an idle state, the subscriber terminal performs the corresponding processing at random timing within a period until the next idle signal is transmitted. The access request signal is repeatedly retransmitted until the access request is accepted and the request data transmission permission signal is received from the relay device. Access method for two-way communication system CATV, characterized in that to perform bidirectional communication using random call scheme only subscriber terminal that received data transmission permission signal to transmit to the relay device.

10. A C including a head end and a bidirectional communication section.
An ATV center, a plurality of subscriber terminals, and the relay device between the center and the plurality of subscriber terminals,
A downlink control data signal is transmitted from the center to the relay device, an uplink control data signal is transmitted from the relay device to the center, and the relay device is transmitted to the plurality of subscriber terminals. In a bidirectional CATV communication system including a bidirectional transmission network for transmitting a downlink control data signal and transmitting an uplink control data signal from the plurality of subscriber terminals to a relay device, the center includes: Generally speaking, bidirectional communication by polling is performed between the headend, which includes re-transmission equipment for retransmitting normal television broadcasting and self-broadcasting equipment for broadcasting self-produced programs, etc., and network monitoring equipment and relay equipment. A first downlink signal output that has a communication unit, and the bidirectional communication unit transmits polling signals and data request signals to a plurality of relay devices. Stage, a first upstream signal receiving means for receiving upstream data sent from the relay device, a first data confirmation means for analyzing the content of the received data and instructing relevant parts to perform the processing, and a subscriber. A video server that outputs a service signal to an idle line only after receiving a request from
The relay device has a demand service device such as an ATM switch, and the communication between the frequency multiplexing device for modulating and synthesizing various signals transmitted from the headend and the communication with the center is performed by polling from the center. And a second bidirectional communication unit, characterized in that communication with a plurality of subscribers is performed by the random call method according to any one of claims 1 to 9, and the second bidirectional communication unit is the above-mentioned It has a second upstream signal receiving means for receiving upstream control data signals transmitted from a plurality of subscriber terminals, and a second data storage means for storing the received signal in a predetermined data storage location, Detected a collision between multiple signals, generated the idle signal as a collision signal is invalid, and if the received signal is normal, the corresponding subscriber Second data confirmation means for generating a final request data transmission permission signal and a busy state signal, and information indicating whether the center obtained from the second data confirmation means is in a busy state or an idle state, and Second downlink signal output means for transmitting the request data transmission permission signal to the plurality of subscriber terminals by including it in a downlink signal, each of the plurality of subscriber terminals being roughly a monitor section and a channel. It has a tuning unit for selecting a channel, a remote control receiving unit, and a third bidirectional communication unit for bidirectional communication with the relay device, and the third bidirectional communication unit receives a downlink signal from the center. Second downlink signal receiving means,
It has a third data storage means for storing the data received by the second downlink signal receiving means and a request command from the subscriber, and analyzes the content of the signal received by the downlink signal receiving means to obtain the downlink signal. A reception signal analysis means for generating information indicating the content of the received signal based on the status information of the relay device and the request data transmission permission signal included in the access request signal according to the information from the reception signal analysis means. Upstream output control means for moving up to or cutting off midway and first upstream signal output means for actually transmitting an access request signal or request data are provided.
After transmitting the access request signal, the presence / absence of permission to transmit the request signal from the relay device is detected within a certain period of time. A bidirectional CAT, characterized in that it has an acceptance confirmation means for sending a retransmission request signal to the first upstream signal output means and for retransmitting the access request signal to the first upstream signal output means at random timing.
V communication system.

11. The communication between a frequency multiplexer that modulates and synthesizes various signals transmitted from the headend and the center side is performed by a polling method from the center, and communication with a plurality of subscribers is performed by the above method. 1 to 9 has a two-way communication unit that performs a random call method and a transceiver that transmits a signal to a center or a plurality of subscribers,
The two-way communication unit has an upstream signal receiving means for receiving upstream control data signals transmitted from the plurality of subscriber terminals, and a data storage means for storing the received signal in a predetermined data storage location, Detects a collision between the received signals, generates an idle signal as the signal with the collision is invalid, and transmits the requested data of the corresponding subscriber terminal when the received signal is normal. Data confirmation means for generating a permission signal and a busy state signal, information on whether the relay device obtained by the data confirmation means is in a busy state or an idle state, and a request data transmission permission signal are added to the plurality of subscriptions. And a downlink signal output means for transmitting the downlink signal to the user terminal.

12. The communication between a frequency multiplexer that modulates and synthesizes various signals transmitted from the headend, the center side, and the communication with a plurality of subscribers are described above.
It has a bidirectional communication section for performing a random call method as described and a transmitter / receiver for transmitting signals to a center or a plurality of subscribers, and the bidirectional communication section has uplink control data transmitted from the plurality of subscriber terminals. It has an upstream signal receiving means for receiving a signal and a data storage means for storing the received signal in a predetermined data storage location, detects a collision between the plurality of received signals, and invalidates the signal having the collision. As an example, when the received signal is normal, a data confirmation means for generating a request data transmission permission signal of the corresponding subscriber terminal and a busy state signal when the received signal is normal, and the above data confirmation. Information about whether the relay device is in a busy state or an idle state obtained by the means and a request data transmission permission signal are transmitted to the plurality of subscriber terminals as downlink signals. Relay apparatus characterized by comprising a downlink signal output means for Umate transmission.

13. A monitor unit, a channel selection unit for performing channel selection, a remote control reception unit, and a bidirectional communication unit for performing bidirectional communication with the relay device, wherein the bidirectional communication unit is a downlink from the relay device. Downlink signal receiving means for receiving a signal, and data storage means for storing the data received by the downlink signal receiving means and a request command from the subscriber are provided, and the content of the signal received by the downlink signal receiving means is analyzed. The received signal analyzing means for generating information indicating the content of the received signal based on the center status information and the request data transmission permission signal included in the downlink signal, and making an access request in accordance with the information from the received signal analyzing means. Upstream output control means for sending a signal to the center or cutting it in the middle, and an upstream signal output means for actually transmitting an access request signal or request data. After the access request signal is transmitted, the presence / absence of request signal transmission permission from the relay device is detected within a certain period of time after transmitting the access request signal. A subscriber comprising reception confirmation means for sending a retransmission request signal to the first upstream signal output means at random timing and for causing the upstream signal output means to retransmit the access request signal at random timing. Terminal.