AU773721B2 - Multidirectional multiplex communication system and ISDN point-to-multipoint communication method - Google Patents

Description

S&F Ref: 499764

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: NEC Corporation 7-1, Shiba Minato-ku Tokyo 108-01 Japan Koichi Nagashima Spruson Ferguson St Martins Tower 31 Market Street Sydney NSW 2000 Invention Title: Multidirectional Multiplex Communication System and ISDN Point-to-multipoint Communication Method The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845c 1 MULTIDIRECTIONAL MULTIPLEX COMMUNICATION SYSTEM AND ISDN POINT-TO-MULTIPOINT COMMUNICATION METHOD BACKGROUND OF THE INVENTION FIELD OF THE INVENTION: The present invention relates to ISDN services in a multidirectional multiplex communication system and, more particularly, to point-to-multipoint communication.

DESCRIPTION OF THE PRIOR ART: 10 A conventional ISDN point-to-multipoint communication method in a multidirectional multiplex communication system of this type is disclosed as "ISDN Service Method in Multidirectional Multiplex Communication System" in Japanese Unexamined Patent Publication No. 10-322758.

15 According to the above reference, as shown in Fig. 17, in this ISDN service method, termination is performed up to layer 2 between an ISDN network 3 and a base station 4 and between a subsidiary ISDN terminal 80 and a subsidiary station 5, and a conventional protocol is used between the base station 4 and the subsidiary station 5, thereby performing frame relay of an ISDN layer 3 message.

The subsidiary station 5 monitors layer 3 messages from the base station 4 and subsidiary ISDN terminal 80 to detect origination of an ISDN call and on-hook operation.

With this operation, the subsidiary station 5 assigns B channel time slots and generates a release request to the base station 4. By performing such demand-assignment line control, the line utilization efficiency is improved, and the number of subscribers accommodated is increased.

According to the above conventional technique, communication line assignment/release between a base station and subsidiary stations is performed in accordance with call origination/on-hook operation by point-to-multipoint communication based on the demand-assignment scheme. However, since 1:1 communication is performed between a master ISDN terminal (not shown) connected to an ISDN network and a subsidiary ISDN terminal connected to a subsidiary station, multi-address calling 0o cannot be performed. For this reason, in order to send the same message from the master ISDN terminal to all subsidiary ISDN terminals, frame relay of a layer 3 message must be repeated by the number of times equal to the number of subsidiary ISDN terminals.

A need thus exists to provide a multidirectional multiplex communication system and ISDN point-to-multipoint communication method which realize 1:N broadcast mode transmission between an ISDN terminal connected to an ISDN network and a plurality of ISDN terminals connected to a plurality of subsidiary stations.

**99 o9 9 9* [R:\LIBCC]26786.doc:wxb -3- Another need exists to provide a multidirectional multiplex communication system and ISDN point-to-multipoint communication method which realize a 1:N broadcast mode transmission between an ISDN terminal connected to an ISDN network and a plurality of ISDN terminals connected to the same subsidiary station.

Still another need exists to provide a multidirectional multiplex communication system and ISDN point-to-multipoint communication method which realize the above 1:N broadcast mode transmission and 1:1 bidirectional communication.

SUMMARY

According to a first aspect of the present invention, there is provided a multidirectional multiplex communication system for performing point-to-multipoint communication between a master ISDN terminal connected to an ISDN network and a plurality of subsidiary ISDN terminals accommodated in a plurality of subsidiary stations under the control of a base station, comprising common time slots assigned to a layer 3 message of a D channel and a B channel of a basic ISDN interface to establish a communication line between the base station and all the subsidiary stations, wherein simultaneous communication can be performed from the master ISDN terminal to all the subsidiary ISDN terminals.

a a 0 S a

S

S

[R:\LIBCC]26786.doc:wxb -4- According to a second aspect of the present invention, there is provided a multidirectional multiplex communication system for performing point-to-multipoint communication between a master ISDN terminal connected to an ISDN network and a plurality of subsidiary ISDN terminals accommodated in a plurality of subsidiary stations under the control of a base station, comprising a base station which terminates the ISDN network up to layer 2, monitors a layer 3 message from the ISDN network and a layer 3 message from the subsidiary station, and assigns a D channel message time slot and B channel time slot and notifies all the subsidiary stations of the time slots through a control channel common to the subsidiary stations when a call setting request message originated by the master ISDN terminal is transmitted through the ISDN network, in order to perform call setting processing in cooperation with the master ISDN terminal, and a plurality of subsidiary stations, each of which terminates a corresponding ISDN terminal up to layer 2, performs call setting processing in cooperation with the corresponding subsidiary ISDN terminal upon receiving a communication line setting message from the base station, establishes a communication line with the base station through a D channel i message time slot and a B channel time slot, performs call setting processing in cooperation with the corresponding subsidiary ISDN terminal if the corresponding ISDN terminal originates a call to communicate with the master ISDN terminal after the communication line establishment, and establishes a communication line by inquiring the base station about a D channel message time slot, B channel time slot, and call number.

S.

[R:\LIBCC]26786.doc:wxb According to a third aspect of the present invention, there is provided a multidirectional multiplex communication system for performing point-to-multipoint communication between a master ISDN terminal connected to an ISDN network and a plurality of subsidiary ISDN terminals accommodated in a plurality of subsidiary stations under the control of a base station, comprising: a base station which includes a layer 1 terminating circuit for terminating layer 1, a layer 2 terminating circuit for terminating layer 2, a logic terminal number management table storing a logic terminal number of each of the plurality of subsidiary ISDN terminals, and a time slot management table, the base station being adapted to perform, with the ISDN network, terminal end point identifier assignment processing for the subsidiary ISDN terminal, call setting processing, assignment processing of a D channel message time and B channel time slot by looking up the time slot management :e o *e* eeo* [R:\LIBCC]26786.doc:wxb 6 table upon origination of a call, management of the terminal end point identifier, management of the logic terminal number, and management of a call number: a plurality of subsidiary stations, each of which includes a layer 1 terminating circuit for terminating layer 1, and a layer 2 terminating circuit for terminating layer 2, the subsidiary stations being adapted to perform the terminal end point identifier assignment processing and call setting processing in cooperation with the corresponding subsidiary ISDN terminal, and to acquire the terminal end point identifier and call number by receiving notification from the base station or making an inquiry thereto through a control channel common to all the subsidiary stations; and a terminal which is connected to the base station so as to register the logic terminal number in the logic terminal number management table.

According to still another preferable aspect of the multidirectional multiplex communication system of the present invention, bidirectional communication between the master ISDN terminal and each subsidiary ISDN terminal can be performed when the master ISDN terminal sends a designated ISDN terminal communication request message to all the subsidiary stations through the base station, and the request is accepted by the designated subsidiary ISDN terminal, or when a communication request is accepted by the master ISDN terminal after the base station which has received a communication request message sent from the subsidiary ISDN terminal confirms contention of communication requests from subsidiary stations.

According to a fourth aspect of the present invention, there is provided a multidirectional multiplex communication method of performing point-to-multipoint communication between a master ISDN terminal connected to an ISDN network and a plurality of subsidiary ISDN terminals accommodated in a plurality of subsidiary stations under the control of a base station, comprising, in the base station, the step of terminating the ISDN network up to layer 2, the step of monitoring layer 3 messages from the ISDN 1o network and the subsidiary station, and the step of assigning a D channel message time slot and B channel time slot upon reception of a call setting request message originated from the master ISDN terminal through the ISDN network, and notifying all the subsidiary stations of the time slots through a control channel common to the subsidiary stations, thereby performing call setting processing in cooperation with the master ISDN 15 terminal, and, in each of the plurality of subsidiary stations, the step of terminating a corresponding one of the subsidiary ISDN terminals up to layer 2, the step of performing call 2 °oo •*go ooo•* •o IR:\LIBCC]26786.docwxb -8setting processing in cooperation with the corresponding subsidiary ISDN terminal upon reception of a communication line setting message from the base station, thereby establishing a communication line with the base station through a D channel message time slot and B channel time slot, and the step of performing call setting processing in cooperation with the corresponding subsidiary ISDN terminal if the corresponding subsidiary ISDN terminal originates a call to communicate with the master ISDN terminal after the communication line establishment, and establishing a communication line by inquiring the base station about a D channel message time slot, B channel time slot, and call number.

As is obvious from the above aspects, the present invention may have the following effects.

The first effect is that 1 :N broadcast mode communication can be performed between a master ISDN terminal and a plurality of subsidiary ISDN terminals. This is because a common B channel is used for transmission from the master ISDN terminal to :o 15 the plurality of subsidiary ISDN terminals.

i: The second effect is that bidirectional communication can be performed between a master ISDN terminal and each of a plurality of subsidiary ISDN terminals. This is because a B channel bus can be connected only between the ooo oooo.

[R:\LIBCC]26786.doc:wxb -9master ISDN terminal and each of the plurality of subsidiary ISDN terminals.

The above and many other features and advantages of embodiments of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which preferred embodiments incorporating the principle of the present invention are shown by way of illustrative examples.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing a technical concept relating to the present invention; Fig. 2 is a block diagram showing the arrangement of the first embodiment of the present invention; Fig. 3 is a sequence chart showing terminal end point identifier assignment operation for subsidiary ISDN terminals in the first embodiment; 15 Fig. 4 is a sequence chart showing call origination from a master ISDN terminal i: to subsidiary ISDN terminals in the first embodiment; Fig. 5 is a view showing the concept of communication between the master ISDN terminal and the subsidiary ISDN terminals in the first embodiment; Fig. 6 is a sequence chart showing call origination from a subsidiary ISDN terminal to the master ISDN

C

[R:\LIBCC]26786.doc:wxb 10 terminal in the first embodiment; Fig. 7 is a sequence chart showing communication from the master ISDN terminal to each subsidiary ISDN terminal in the first embodiment; Fig. 8 is a sequence chart showing communication from a subsidiary ISDN terminal to the master ISDN terminal in the first embodiment; Fig. 9 is a sequence chart showing on-hook operation from a subsidiary ISDN terminal in the first embodiment; 10 Fig. 10 is a sequence chart showing on-hook operation oo :from the master ISDN terminal; Fig. 11 is a block diagram showing the arrangement of the second embodiment of the present invention; Fig. 12 is a sequence chart showing call origination 15 from the master ISDN terminal to subsidiary ISDN terminals in the second embodiment; Fig. 13 is a view showing the concept of communication between the master ISDN terminal and the subsidiary ISDN terminals in the second embodiment; Fig. 14 is a sequence chart showing call origination from a subsidiary ISDN terminal to the master ISDN terminal in the second embodiment; Fig. 15 is a sequence chart showing communication from the master ISDN terminal to each subsidiary ISDN terminal in the second embodiment; 11 Fig. 16 is a sequence chart showing on-hook operation from the master ISDN terminal in the second embodiment; and Fig. 17 is a block diagram showing the arrangement of a conventional system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A few preferable embodiments of the present invention will be described below with reference to the accompanying drawings.

1 0 A multidirectional multiplex communication system of a point-to-multipoint communication scheme according to the first embodiment of the present invention will be described first with reference to Fig. 1.

Referring to Fig. 1, a master ISDN terminal 1 is 15 connected to an ISDN network 3 through a. network terminating apparatus (to be referred to as an "NT" hereinafter) 2. A base station 4 is also connected to the ISDN network 3. A subsidiary ISDN terminal 80 is connected to a subsidiary station 5 through an NT 70. A subsidiary ISDN terminal 81 is connected to a subsidiary station 6 through an NT 71.

The base station 4 provides the ISDN network 3 with a U point of a basic ISDN interface. The subsidiary stations 5 and 6 respectively provide the subsidiary ISDN terminals 80 and 81 with U points of basic ISDN interfaces.

12 The base station 4 and subsidiary stations 5 and 6 perform time-division multiplex communication. An O&M terminal in which the logic terminal numbers of the subsidiary ISDN terminals 80 and 81 are registered is connected to the base station 4.

The base station 4 and subsidiary stations 5 and 6 respectively terminate the ISDN network 3 and subsidiary ISDN terminals 80 and 81 up to layer 2.

The subsidiary ISDN terminals 80 and 81 have the same 10 TEI (Terminal Endpoint Identifier) value. These TEIs are assigned to the subsidiary ISDN terminals 80 and 81 from the ISDN network 3 in response to a request from the base station 4. The base station 4 notifies the subsidiary stations 5 and 6 of the TEIs when the base station 4 is 15 started up and the subsidiary stations 5 and 6 are started up. The base station 4 monitors Dch messages converted from layer 3 messages from the ISDN network 3 and subsidiary stations 5 and 6. When a call setting request message originated from the master ISDN terminal 1 is transmitted from the ISDN network 3 to the base station 4, the base station 4 assigns Dch message TSs (Time Slots)' and Bch TSs, and notifies the subsidiary stations 5 and 6 of the TSs.

Cch 100 is a control channel common to the subsidiary stations and used to transmit/receive control messages 13 between the base station 4 and the subsidiary stations and 6. The base station 4 performs call setting processing with the master ISDN terminal i. The O&M terminal 10 registers the logic terminal numbers of the subsidiary ISDN terminals 80 and 81.

Upon receiving communication line setting messages from the base station 4, the subsidiary stations 5 and 6 respectively perform call setting processing with the •ego subsidiary ISDN terminals 80 and 81. As a consequence, 10 1 2 communication lines are established between the base station 4 and the subsidiary stations 5 and 6 through Dch message TSs and Bch TSs.

If the subsidiary ISDN terminal 81 originates a call for communication with the master ISDN terminal 1 after the establishment of the communication lines with the base stations 4 and 5, the subsidiary station 6 inquires the base station 4 about a Dch message TS, Bch TS, and call number, thereby establishing a communication line. This call setting processing is also performed between the subsidiary station 6 and the subsidiary ISDN terminal 81.

In general, communication lines are set in a broadcast mode of capable of transmitting data or speech information from the master ISDN terminal 1 to all the subsidiary ISDN terminals 80 and 81. Therefore, 1 1 communication between the master ISDN terminal 1 and the 14 subsidiary ISDN terminal 80 or 81 can be performed after the master ISDN terminal 1 transmits a designated ISDN terminal communication request message to all the subsidiary stations 5 and 6 through the base station 4, and the request is accepted by the designated subsidiary ISDN terminal 80 or 81.

In addition, the subsidiary ISDN terminal 80 or 81 can generate a request to the master ISDN terminal 1 to perform 1 1 communication between the master ISDN 10 terminal 1 and the subsidiary ISDN terminal 80 or 81. In this case, communication can be performed after the base station 4 that has received the communication message sent Sfrom the subsidiary ISDN terminal 80 or 81 sends the communication request message to the master ISDN terminal 15 1 upon confirming communication request contention from subsidiary stations, and the request is accepted by the master ISDN terminal 1.

Fig. 2 shows the first embodiment of the present invention. Referring to Fig. 2, a basic ISDN interface line 91 from the ISDN network 3 is connected to the base station 4 to allow the master ISDN terminal 1 to communicate with the subsidiary ISDN terminals 80 and 81.

Basic ISDN interface lines 92 and 93 are respectively connected to the subsidiary stations 5 and 6 to allow the subsidiary ISDN terminals 80 and 81 to communicate with 15 the master ISDN terminal 1.

The base station 4 and subsidiary stations 5 and 6 respectively include layer 1 terminating circuits 41, 51, and 61 for terminating layer 1 and layer 2 terminating circuits 42, 52, and 62 for terminating layer 2. With this arrangement, layer 1 synchronization and layer 2 links are respectively established between the base station 4 and the ISDN network 3, the subsidiary station O O0 0000 and the subsidiary ISDN terminal 80, and subsidiary 1' 0 station 6 and the subsidiary ISDN terminal 81. As a layer "0 1 terminating circuit and layer 2 terminating circuit, known circuits based on the ISDN communication scheme using LSIs complying with the ITU-T standards are used.

The base station 4 performs TEI assignment processing 15 and call setting processing with the ISDN network 3, assigns Dch message TSs and Bch TSs by looking up a TS management table 44 at the time of generation of a call, and manages TEIs and call numbers. The O&M terminal connected to the base station 4 stores logic terminal numbers in a logic terminal number management table 43.

The subsidiary stations 5 and 6 perform TEI assignment processing and call setting processing with the subsidiary ISDN terminals 80 and 81, respectively. The subsidiary stations 5 and 6 acquire the TEIs and call numbers of the subsidiary ISDN terminals 80 and 81 through 16 Cch by notification from the base station 4 or inquires to the base station 4. In general, communication from the master ISDN terminal 1 to the subsidiary ISDN terminals and 81 is performed in the broadcast mode. If, therefore, communication is to be made with a specific subsidiary ISDN terminal, the master ISDN terminal 1 transmits a communication request message containing the logic terminal number of the designated subsidiary ISDN terminal to all the subsidiary stations. This communication can be 10 performed after the master ISDN terminal 1 receives a response message from the subsidiary ISDN terminal having this logic terminal number.

When each of the subsidiary ISDN terminals 80 and 81 is to individually communicate with the master ISDN terminal 1, each subsidiary ISDN terminal transmits a communication request message to the base station 4. This communication can be performed after the subsidiary ISDN terminal receives a response message from the master ISDN terminal 1 that has received a communication request acceptance message and communication request message from the base station 4.

The operation the first embodiment will be described next.

TEI Assignment of Subsidiary ISDN Terminal: TEI assignment performed by the subsidiary ISDN 17 terminals 80 and 81 will be described with reference to the sequence chart of Fig. 3. TEIs are assigned to the subsidiary ISDN terminals 80 and 81 when the base station 4 notifies the subsidiary stations 5 and 6 of the TEIs acquired by sending TEI assignment requests to the ISDN network 3, and the subsidiary ISDN terminals 80 and 81 send TEI assignment requests to the subsidiary stations and 6.

Call Origination from Master ISDN Terminal to Subsidiary ISDN Terminal: Call origination from the master ISDN terminal 1 to subsidiary ISDN terminals 80 and 81 will be described with reference to the sequence chart of Fig. 4. When the master ISDN terminal 1 originates a call, a SETUP message is sent to the base station 4 through ISDN network 3.

Upon reception of the SETUP message, the base station 4 hO transmits a communication line setting message to all the subsidiary stations 5 and 6 through Cch. This communication line setting message contains Dch message TSs and Bch TSs between the base station 4 and the subsidiary stations 5 and 6 and call numbers.

Upon receiving the communication line setting message, the subsidiary stations 5 and 6 perform call setting processing by known procedures between the subsidiary stations 5 and 6 and the subsidiary ISDN terminals 80 and 18- 81, and assign TSs designated by the communication line setting message as a Dch message. The subsidiary stations and 6 connect Bch TSs designed by the communication line setting message and downstream Bch to the subsidiary ISDN terminals 80 and 81 by time-division switches. The base station 4 performs call setting with the master ISDN terminal 1 according to a known procedure independently of the operation each subsidiary station.

Upon completion of call setting processing, the 10 subsidiary ISDN terminals 80 and 81 send communication line setting completion messages to the subsidiary stations 5 and 6 by using layer 3 messages. The subsidiary stations 5 and 6 add logic terminal numbers to the received communication line setting completion messages and send the resultant messages to the base station 4 through the Dch message TSs notified over the 4 communication line setting messages. The message form used in this case is a Dch message format that is unique to the system and used between each subsidiary station and the base station, and is converted into a layer 3 message by the base station 4.

The communication line setting completion messages received by the base station 4 are sent to the master ISDN terminal 1 through the ISDN network 3. Thus, the master ISDN terminal 1 can recognize the subsidiary stations 19 under communication. With the above operation, the master ISDN terminal 1 can perform 1 2 communication with the subsidiary ISDN terminals 80 and 81 by using Bch.

Fig. 5 shows the concept of communication between the master ISDN terminal 1 and the subsidiary ISDN terminals and 81.

Call Origination from Subsidiary Station to Master ISDN Terminal: Call origination to allow the subsidiary ISDN 10 terminal 81 to communicate with the master ISDN terminal 1 while the master ISDN terminal 1 is communicating with the subsidiary ISDN terminal 80 will be described with reference to the sequence chart of Fig. 6.

When the subsidiary ISDN terminal 81 originates a call, a SETUP message is sent to the subsidiary station 6.

Upon receiving the SETUP message from the subsidiary ISDN terminal 81, the subsidiary station 6 sends a communication line setting request message to the base station 4 through Cch in order to acquire a Dch message TS, Bch TS, and call number. Upon receiving the communication line setting request message, the base station 4 returns a communication line setting response message containing the Dch message TS, Bch TS, and call number to the subsidiary station 6.

Upon receiving the communication line setting 20 response message, the subsidiary station 6 performs call setting processing with the subsidiary ISDN terminal 81, assigns the Dch message TS, and connects the Bch TS to downstream Bch on the subsidiary ISDN terminal 81 side by a time-division switch. Upon completion of call setting processing, the subsidiary ISDN terminal 81 sends a communication line setting completion message to the master ISDN terminal 1 through the base station 4 and ISDN network 3. With the above operation, the subsidiary ISDN terminal 81 can communicate with the master ISDN terminal *1.

Communication from Master ISDN Terminal to Each Subsidiary ISDN Terminal: Communication from the master ISDN terminal 1 to the o* subsidiary ISDN terminal 80 will be described with reference to the sequence chart of Fig. 7.

During communication between the master ISDN terminal 1 and the subsidiary ISDN terminals 80 and 81, control messages are transmitted/received over layer 3 messages between the master ISDN terminal 1 and the base station 4 and between the subsidiary stations 5 and 6 and the subsidiary ISDN terminals 80 and 81, and over Dch messages unique to the system between the base station 4 and the subsidiary stations 5 and 6. The layer 3 messages and Dch messages are converted in the base station 4 and 21 subsidiary stations 5 and 6, respectively.

When the master ISDN terminal 1 generates a request to communicate with the subsidiary ISDN terminal 80, a communication request message is sent from themaster ISDN terminal 1 to all the subsidiary stations 5 and 6 through the ISDN network 3 and base station 4. Upon receiving the communication request message, the subsidiary station accommodating the subsidiary ISDN terminal 80 sends the communication request message to the subsidiary ISDN 10 terminal 80. The subsidiary station 6, which is not accommodating the subsidiary ISDN terminal 80, performs no operation upon receiving the communication request message.

Upon receiving the communication request message, the subsidiary ISDN terminal 80 sends a communication request response message to the master ISDN terminal 1 through the subsidiary station 5, base station 4, and ISDN network 3.

Upon receiving the communication request response message, the master ISDN terminal 1 returns a communication request response acknowledgement message to the subsidiary stations 5 and 6 through the ISDN network 3 and base station 4. Upon receiving the communication request response acknowledgement message, the subsidiary station connects an upstream Bch bus from the subsidiary ISDN terminal 80. The subsidiary station 6 disconnects a downstream Bch bus. This operation makes it possible to 22 perform 1 1 bidirectional communication between the master ISDN terminal 1 and the subsidiary ISDN terminal Upon completion of communication, the master ISDN terminal 1 sends a communication completion message indicating the completion of communication with the subsidiary ISDN terminal 80 to the subsidiary stations and 6 through the ISDN network 3 and base station 4. The communication completion message is transmitted from only the subsidiary station 5 accommodating the subsidiary ISDN 10 terminal 80 to the subsidiary ISDN terminal 80. Upon receiving the communication completion message, the subsidiary ISDN terminal 80 transmits a communication completion response message to the master ISDN terminal 1 through the subsidiary station 5, base station 4, and ISDN network 3.

Upon receiving the communication completion response message, the master ISDN terminal 1 transmits a communication completion response acknowledgement message to the subsidiary stations 5 and 6 through the ISDN network 3 and base station 4. Upon receiving the communication completion response acknowledgement message, the subsidiary station 5 transmits the communication completion response acknowledgement message to the subsidiary ISDN terminal 80, and also releases the upstream Bch bus from the subsidiary ISDN terminal 23 The subsidiary station 6 connects the downstream Bch bus to the subsidiary ISDN terminal 81. With this operation, the communication mode returns to 1 2 communication from the master ISDN terminal 1 to the subsidiary ISDN terminals 80 and 81.

Communication from Subsidiary ISDN Terminal to Master ISDN Terminal: Communication operation to allow the subsidiary ISDN terminal 80 to individually communicate with the master 10 ISDN terminal 1 will be described with reference to the *g sequence chart of Fig. 8.

When the subsidiary ISDN terminal 80 generates a o" communication request, a communication request message is transmitted to the base station 4 through the subsidiary 15 station 5. Upon receiving the communication request message, the base station 4 checks whether a communication request is received from the other subsidiary ISDN terminal 81. Only when no communication request is received from the other terminal, the base station 4 transmits the received communication request message to the master ISDN terminal 1 through the ISDN network 3, and also sends a communication request acceptance message with respect to the subsidiary ISDN terminal 80 to the subsidiary stations 5 and 6.

Upon receiving the communication request message, the 24 master ISDN terminal 1 sends a communication request response message for the subsidiary ISDN terminal 80 to the base station 4. The base station 4 transmits the received the communication request response message for the subsidiary ISDN terminal 80 to the subsidiary stations and 6. Upon receiving the communication request response message for the subsidiary ISDN terminal 80 from the base station 4, each of the subsidiary stations 5 and 6 checks whether the message is a communication request 10 response message for the subsidiary ISDN terminal which S" the corresponding subsidiary station is accommodating.

*The subsidiary station 5, which is accommodating the subsidiary ISDN terminal 80, transmits the received communication request response message to the subsidiary 15 ISDN terminal 80, and connects the upstream Bch bus from the subsidiary ISDN terminal 80 by the time-division switch. The subsidiary station 6, which is not accommodating the subsidiary ISDN terminal 80, disconnects the downstream Bch bus from the subsidiary ISDN terminal 81. This operation makes it possible to perform 1 1 bidirectional communication between the subsidiary ISDN terminal 80 and the master ISDN terminal 1.

When the communication is over, a communication completion message is sent from the subsidiary ISDN terminal 80 to the master ISDN terminal 1 through the 25 subsidiary station 5, base station 4, and ISDN network 3.

Upon receiving the communication completion message, the master ISDN terminal 1 transmits a communication completion response message to the subsidiary stations and 6 through the ISDN network 3 and base station 4. Upon receiving the communication completion response message, the subsidiary station 5 transmits the communication completion response message to the subsidiary ISDN terminal 80, and also disconnects the upstream Bch bus 10 from the subsidiary ISDN terminal 80. The subsidiary

S.

station 6 connects the downstream Bch bus to the subsidiary ISDN terminal 80. With this operation, the communication mode returns to 1 2 communication from the master ISDN terminal 1 to the subsidiary ISDN terminals 15 and 81.

sr On-hook Operation from Subsidiary ISDN Terminal: On-hook operation from the subsidiary ISDN terminal will be described with reference to the sequence chart of Fig. 9.

When the subsidiary ISDN terminal 80 performs on-hook operation, a DISC message is sent from the subsidiary ISDN terminal 80 to the subsidiary station 5. Upon receiving the DISC message, the subsidiary station 5 transmits a terminal 80 communication line release message through Cch and releases the Dch message TS and the Bch bus from the 26 subsidiary ISDN terminal 80. On-hook operation is performed between the subsidiary ISDN terminal 80 and the subsidiary station 5 by a known procedure.

On-hook Operation from Master ISDN Terminal: On-hook operation from the master ISDN terminal 1 will be described with reference to the sequence chart of Fig. When the master ISDN terminal 1 performs on-hook operation, a DISC message is sent from the master ISDN 10 terminal 1 through the ISDN network 3. Upon receiving the DISC message, the base station 4 transmits a communication line release message to the subsidiary stations 5 and 6 through Cch, and releases the Dch message TS, Bch TS, and Bch bus. On-hook operation on the master ISDN terminal 1 is performed between the master ISDN terminal 1 and base Sstation 4 by a known procedure.

Upon receiving the communication line release messages, the subsidiary stations 5 and 6 release the Dch message TSs and Bch TSs and perform on-hook processing with the subsidiary ISDN terminals 80 and 81, respectively, by known procedures.

The second embodiment of the present invention will be described next with reference to the accompanying drawings.

Fig. 11 shows the arrangement of the second 27 embodiment. According to the system configuration of the first embodiment, each subsidiary station accommodates one subsidiary ISDN terminal. In the second embodiment, each subsidiary station accommodates a plurality of subsidiary ISDN terminals. In addition, a logic terminal number management table 53 is provided for the subsidiary stations to allow each subsidiary station to control a plurality of subsidiary ISDN terminals.

TEI Assignment of Subsidiary ISDN Terminal: 10 As in the first embodiment, TEIs are assigned to subsidiary ISDN terminals 80 and 81 when the TEIs are notified from a base station 4, and the subsidiary ISDN terminals 80 and 81 send TEI assignment requests to a subsidiary station Call Origination from Master ISDN Terminal to Subsidiary ISDN Terminals: 28 Fig. 12 shows a sequence for call origination from a master ISDN terminal 1 to subsidiary ISDN terminals 80 and 81. This sequence differs from that in the first embodiment in that the subsidiary station 5 which has received a communication line setting message from the base station 4 performs call setting processing with a plurality of subsidiary ISDN terminals 80 and 81 and control operation to connect a Bch TS and downstream Bch S:"by a time-division switch.

S" 0 Logic terminal numbers corresponding to the subsidiary ISDN terminals 80 and 81 and selected from the logic terminal number management table 53 by the subsidiary station 5 are added to a communication line setting completion message sent from the subsidiary 15 station 5 to the base station 4. Logic terminal numbers Sare registered in the logic terminal number management table 53 of the subsidiary station 5, through Cch 100, from an O&M terminal 10 connected to the base station 4.

Fig. 13 shows a concept of communication between the master ISDN terminal 1 and the subsidiary ISDN terminals and 81.

Call Origination From Subsidiary ISDN Terminal to Master ISDN Terminal: Fig. 14 shows a call origination sequence of allowing the subsidiary ISDN terminal 81 to communicate with the 29 master ISDN terminal 1 during communication between the master ISDN terminal 1 and the subsidiary ISDN terminal This sequence differs from that in the first embodiment in that the subsidiary station 5 performs call generation processing only within the subsidiary station without sending any communication line setting request message to the base station 4 because the subsidiary station has already possessed a Bch TS and call number.

Communication from Master ISDN Terminal to Each 10 Subsidiary ISDN Terminal: Fig. 15 shows a sequence for communication from the master ISDN terminal 1 to the subsidiary ISDN terminal This sequence differs from that in the first embodiment in that the subsidiary station 5 controls the downstream Bch bus to the subsidiary ISDN terminal 81 other than the one designated by the master ISDN terminal because the subsidiary station 5 is accommodating a plurality of subsidiary ISDN terminals.

Communication from Subsidiary ISDN Terminal to Master ISDN Terminal: This operation differs from that in the first embodiment in that a subsidiary station checks whether a communication request is received from any subsidiary ISDN terminal other than the one that has generated a communication request, and sends a communication request 30 message to the master ISDN terminal only when no communication request is received.

On-hook Operation from Subsidiary ISDN Terminal: This operation differs from that in the. first embodiment in that a subsidiary station does not release a Dch message TS if a subsidiary ISDN terminal other than the one that has sent a DISC message is under "communication, and releases the Dch message TS when all S• the subsidiary ISDN terminals accommodated in the 10 subsidiary station are set in the on-hook state.

On-hook Operation from Master ISDN Terminal: ~Fig. 16 shows a sequence for on-hook operation from the master ISDN terminal 1. This operation differs from that in the first embodiment in that the subsidiary station 5 performs on-hook processing for a plurality of subsidiary ISDN terminals 80 and 81 accommodated in the subsidiary station 5 upon receiving a communication line release message from the base station 4.

As has been described above, according to the second embodiment of the present invention, 1 N broadcast mode communication can be performed between a master ISDN terminal and a plurality of subsidiary ISDN terminals accommodated in a subsidiary station.

Claims (3)

1. A multidirectional multiplex communication system for performing point-to-multipoint communication between a master ISDN terminal connected to an ISDN network and a plurality of subsidiary ISDN terminals accommodated in a plurality of subsidiary stations under the control of a base station, comprising common time slots assigned to a layer 3 message of a D channel and a B channel of a basic ISDN interface to establish a communication line between said base station and all said subsidiary stations, wherein simultaneous communication can be performed from said master ISDN terminal to all said subsidiary ISDN terminals.

2. A multidirectional multiplex communication system for forming point-to-multipoint communication between a master ISDN terminal connected to an ISDN network and a plurality of subsidiary ISDN terminals accommodated in a plurality of subsidiary stations under the control of a base station, comprising: a base station which terminates said ISDN network up to layer 2, monitors a layer 3 message from said ISDN network and a layer 3 message from said subsidiary station, and assigns a D channel message time slot and B channel time slot and notifies all said subsidiary stations of the time slots through a control channel common to said

32- subsidiary stations when a call setting request message originated by said master ISDN terminal is transmitted through said ISDN network, in order to perform call setting processing in cooperation with said master ISDN terminal, and a plurality of subsidiary stations, each of which terminates a corresponding ISDN terminal up to layer 2, e performs call setting processing in cooperation with said S" corresponding subsidiary ISDN terminal upon receiving a 10 communication line setting message from said base station, establishes a communication line with said base station •o through a D channel message time slot and a B channel time 00 slot, performs call setting processing in cooperation with said corresponding subsidiary ISDN terminal if said corresponding ISDN terminal originates a call to communicate with said master ISDN terminal after the communication line establishment, and establishes a communication line by inquiring said base station about a D channel message time slot, B channel time slot, and call number. 3. A multidirectional multiplex communication system for performing point-to-multipoint communication between a master ISDN terminal connected to an ISDN network and a plurality of subsidiary ISDN terminals accommodated in a plurality of subsidiary stations under the control of a 1, 33 base station, comprising: a base station which includes a layer 1 terminating circuit for terminating layer i, a layer 2 terminating circuit for terminating layer 2, a logic terminal number management table storing a logic terminal number of each of said plurality of subsidiary ISDN terminals, and eS.. a time slot management table, said base station being adapted to perform, with the 10 ISDN network, terminal end point identifier assignment processing for said subsidiary ISDN terminal, call setting oooo oo processing, assignment processing of a D channel message time and B channel time slot by looking up said time slot management table upon origination of a call, management of the terminal end point identifier, management of the logic terminal number, and management of a call number; :i a plurality of subsidiary stations, each of which includes a layer 1 terminating circuit for terminating layer 1, and a layer 2 terminating circuit for terminating layer 2, said subsidiary stations being adapted to perform the terminal end point identifier assignment processing and call setting processing in cooperation with said corresponding subsidiary ISDN terminal, and to acquire the ,m 1 n r, 34 terminal end point identifier and call number by receiving notification from said base station or making an inquiry thereto through a control channel common to all said subsidiary stations; and a terminal is connected to said base station so as to register the logic terminal number in said logic terminal number management table. oo*. 4. A system according to claim 3, wherein each of said plurality of subsidiary stations accommodates a 10 plurality of subsidiary ISDN terminals, and each of said subsidiary stations includes a logic terminal number management table for controlling said subsidiary ISDN o o terminals. 5. A system according to claim i, wherein terminal oooo end point identifiers of all said subsidiary ISDN terminals are equal in value, and the terminal end point S•identifiers are assigned from the ISDN network in response to a request from said base station and notified from said base station to all said subsidiary stations when said base station is started up and said subsidiary stations are started up. 6. A system according to claim 2, wherein terminal end point identifiers of all said subsidiary ISDN terminals are equal in value, and the terminal end point identifiers are assigned from the ISDN network in response I I IJ 35 to a request from said base station and notified from said base station to all said subsidiary stations when said base station is started up and said subsidiary stations are started up. 7. A system according to claim 3, wherein terminal end point identifiers of all said subsidiary ISDN terminals are equal in value, and the terminal end point identifiers are assigned from the ISDN network in response to a request from said base station and notified from said 10 base station to all said subsidiary stations when said 5. base station is started up and said subsidiary stations are started up. 8. A system according to claim 4, wherein terminal end point identifiers of all said subsidiary ISDN terminals are equal in value, and the terminal end point Sidentifiers are assigned from the ISDN network in response to a request from said base station and notified from said base station to all said subsidiary stations when said base station is started up and said subsidiary stations are started up. 9. A multidirectional multiplex communication method of performing point-to-multipoint communication between a master ISDN terminal connected to an ISDN network and a plurality of subsidiary ISDN terminals accommodated in a plurality of subsidiary stations under the control of a 36 base station, comprising: in said base station, the step of terminating the ISDN network up to layer 2; the step of monitoring layer 3 messages from the ISDN network and said subsidiary station; and the step of assigning a D channel message time slot and B channel time slot upon reception of a call setting S. request message originated from said master ISDN terminal 10 through the ISDN network, and notifying all said subsidiary stations of the time slots through a control channel common to said subsidiary stations, thereby performing call setting processing in cooperation with St t* said master ISDN terminal, and in each of said plurality of subsidiary stations, the step of terminating a corresponding one of said subsidiary ISDNterminals up to layer 2; the step of performing call setting processing in cooperation with said corresponding subsidiary ISDN terminal upon reception of a communication line setting message from said base station, thereby establishing a communication line with said base station through a D channel message time slot and B channel time slot; and the step of performing call setting processing in cooperation with said corresponding subsidiary ISDN -37- terminal if said corresponding subsidiary ISDN terminal originates a call to communicate with said master ISDN terminal after the communication line establishment, and establishing a communication line by inquiring said base station about a D channel message time slot, B channel time slot, and call number. A multidirectional multiplex communication system substantially as herein described with reference to Figs. 1-10 or Figs. 1, 11-16 of the accompanying drawings. 10o 11. A multidirectional multiplex communication method, said method substantially as herein described with reference to Figs. 1-10 or Figs. 1, 11-16 of the accompanying drawings. S. DATED this Thirteenth Day of March, 2000 NEC Corporation Patent Attorneys for the Applicant SPRUSON FERGUSON [R:\LIBQ]00190.doc:bfd