JPH0817426B2 - Communications system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a bus type communication system.

(Prior Art) In recent years, the development of communication networks including new media has been remarkable, and in order to realize higher and higher speed communication services, the communication system is shifting from analog communication to digital communication.

ISDN (Integrated Service Digital Network), which is currently being standardized internationally by CCITT (International Telegraph and Telephone Advisory Committee)
Is a typical one, and is expected to spread as a communication network in each country.

In this ISDN, various services are realized by integrating a communication network that has been independent in the past, such as a telephone network, a data network, and a facsimile network, into one.

For example, in the basic interface specified by CCITT I series recommendation, by multiplexing and transmitting two information channels (for terminal-terminal information transmission) and signal channels (for terminal-switch control information transmission),
A maximum of eight communication terminals of various types are connected to the same transmission line by a bus so that a plurality of terminals can communicate at the same time.

Further, in the basic interface in this ISDN, as shown in FIG. 3, a plurality of users A, B, ... Can each connect various communication terminals to a bus to a network such as PBX1.

By the way, in the case of the system as shown in FIG. 3, since a terminal having different attributes such as a telephone 2 and a FAX3 data terminal 4 may be connected like the user B shown in the same figure, a call may be made prior to communication. It is necessary to check the consistency between the terminal and the receiving terminal. For this reason, CCITT Recommendation I.451 (Layer 3) defines the procedure for checking consistency.

FIG. 4 is an operation sequence for making and receiving a call based on the procedure specified by CCITT recommendation for confirming the consistency. In this example, when the user A shown in FIG. Is assumed.

That is, as shown in FIG. 4, when the user A makes a telephone call, a "call setup" message for this call request is sent to the PBX 1 using the signaling channel. At this time, various call control messages are transmitted in the information (I) frame in the data link control procedure defined by CCITT Recommendation I.441 (Layer 2). That is, in this data link control procedure, user A first sends SABME (extended asynchronous balanced mode command) to PBX1, and user A
The layer 2 is initialized by receiving a UA (unnumbered confirmation response) from the PBX1, and a "call setup" message is transmitted from the user A to the PBX1 by an I frame. The "call setting" message contains the other party's number and its own terminal attribute (telephone in this case). Further, the layer 2 has a peculiar address (W in this case) shown by () in the figure, and is used for frame transmission / reception of the layer 2.

When PBX1 receives this "call setup" message, it refers to the other party's number included in this "call setup" message and designates the designated party (in this case, user B).
To the terminal, a "call setting" message for notifying the incoming call is sent. Here, in ISDN, in order to ensure the portability of the user's terminal, the PBX 1 side does not manage the presence or absence of connection of the user terminal, attributes, etc. Therefore, the originating terminal (user A) and the receiving terminal (user B) It is necessary to confirm the consistency with Therefore, all terminals in user B,
In this case, the telephone 2, FAX 3 and data terminal 4 need to receive the "call setup" message normally sent from the PBX 1 to the user B.

Here, since each terminal has a unique address (X), (Y), and (Z), the PBX 1 sends a "call setup" message in the broadcast UI frame to the user B. All terminals of user B are notified of the incoming call.

Then, each terminal of this user B receives this "call setup" message at the same time, refers to the terminal attributes included in this message, and executes comparison and matching with the attributes of its own terminal. As a result, the terminal with the matching attribute sends a "call setup" message to the PBX1 and the terminal with the mismatching attribute sends a "release completion" message including the reason for the attribute mismatch to the PBX1. The procedure for this is to send SABME including the unique addresses (X), (Y) and (Z) to each PBX1 in advance from each terminal of the user B, similarly to the above-mentioned transmission from the user A to the PBX1. Then, the data link setting procedure of receiving the UA from the PBX1 is executed.

On the other hand, the PBX 1 waits for a response from the receiving side terminal for a predetermined time, for example, 1 second, after notifying the receiving side of the incoming call, that is, after transmitting the "call setting" message to the user B. Then, in this case, "release completion" including attribute mismatch from the data terminal (X) and FAX (Y) within this time
A message, a "call" message for accepting an incoming call from the telephone (Z) is returned. Then, the former takes a disconnection procedure, and the latter performs the connection processing of the calling terminal, so that the call is realized using the B channel.

It should be noted that, as shown in FIG. 5, the procedures for making and receiving calls as described above are performed by layer 1 (electrical physical layer), layer 2 (data link) and layer 3 (network) of the PBX1 and the terminal.
It is realized by three layers consisting of

Here, in the example shown in FIG. 5, three types of terminals, that is, a data terminal, a FAX, and a telephone are connected on the signal channel from the PBX1, but layer 1 and layer 3 are all terminals on the PBX1 side. , While Layer 2 provides unique data link parameters for each terminal, such as transmit state variable N (S), receive state variable N (R),
Since it has other timers etc., the address (X) of each terminal,
Has independent layer 2 for (Y) and (Z),
Each layer 2 needs to be multiplexed on the layer 1 signaling channel. In the series of processes, the software of the same microprocessor sequentially processes the data links of (X), (Y), and (Z) of layer 2 by time division processing.

By the way, in the example shown in FIG. 4, the terminal that cannot accept the incoming call is "opening complete" as described above.
Responding with a message is necessary to distinguish from no response when no terminal is connected to the called side, but the signaling channel shown in FIG. 5 is common to all terminals. Therefore, each terminal needs to monitor the availability of the signal channel and send the response information to the signal channel. However, the order of sending this response varies depending on the processing speed of the microprocessor inside each terminal, so a negative response "release complete" message is sent first, and an affirmative response "call" message is sent later. In some cases, the PBX1 cannot proceed with the connection process until an affirmative response is received, and there is a problem that the connection is delayed.

On the other hand, in ISDN, the user can freely connect various terminals to the transmission line at any time, and the number of terminals is not specified. However, on the network side such as PBX1, Layer 2
In order to execute (data link) or layer 3 (call origination / termination control) and realize downsizing and cost reduction, it is considered that the number of connected user terminals is defined.
In this case, the network side determines the number of connected user terminals to be n.
In this case, n layers 2 and n layers 3 capable of controlling n terminals should be realized.

By the way, even though the number of layers 2 that can be simultaneously processed on the PBX1 side is set to n in this way, when n or more terminals are connected on the transmission line, there is a terminal that can respond positively to an incoming call. However, if the terminal that responds with a negative response sends n responses first, the terminal that responds with a positive response cannot set the layer 2 data link.
For SABME to X1, this terminal cannot receive the UA from PBX1, so there is a problem that the incoming call cannot be established.

(Problems to be Solved by the Invention) As described above, in the communication system in which the terminals connected to the bus on the same transmission line are notified from the network side of the incoming call all at once in a broadcast format like the basic interface in ISDN described above, In order to distinguish between the case where the terminal is not connected to the called side and the case where the attributes of the terminal do not match when receiving a call, it is necessary for the called side to make a negative response to the incoming call to the network side for the mismatch of the attributes. It

Therefore, for example, due to the processing speed of the microprocessor inside each terminal, a negative response may be sent before the positive response. In this case, the network side performs the connection process until the positive response is returned. However, there is a problem that the connection is delayed.

Also, if more than the number of terminals that can be processed simultaneously on the network side are connected on the transmission path, and if more than this number of terminals send a negative response in advance, the terminal that can respond with an affirmative response to the incoming call Even if there is, there is a problem that the incoming call cannot be established.

The present invention has been made based on such circumstances,
It is an object of the present invention to provide a communication system that can not only realize a quick connection process but also can reliably make an incoming call when a terminal capable of receiving an incoming call exists.

[Structure of the Invention] (Means for Solving the Problem) The present invention is configured such that a plurality of terminals are connected in a bus-like manner on a transmission path connected to a predetermined network. In a communication system in which notifications are sent all at once in a broadcast format and a line connection is made to terminals that have transmitted an affirmative response to the effect that an incoming call is to be received, it is determined whether or not each terminal receives an incoming call notified from the network. Incoming call determining means and, when it is determined that the incoming call is accepted, sends an affirmative response to the network side, and when it is determined that the incoming call is not accepted, a negative response is given after a predetermined period without answering the incoming call. And means for controlling the transmission so that the data is transmitted to the network side.

(Operation) In the present invention, since each terminal controls the transmission of the response to this incoming call based on the determination result of whether or not to accept the incoming call that is broadcasted simultaneously from the network,
Not only can a quick connection process be realized, but when there is a terminal capable of receiving an incoming call, the incoming call can be surely made.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

In a communication system according to an embodiment of the present invention, as shown in FIG. 3 of a conventional example, a plurality of users A, B ... The communication terminals are bus-connected, and in particular, the user A has only the telephone 5 as a terminal, and the user B has the telephone 2, the fax 3 and the data terminal 4 as terminals.

Here, FIG. 1 shows a call originating / receiving operation sequence when the present invention is applied to the communication system having the configuration shown in FIG. 3, and the present embodiment will be described below based on this figure. Note that the example of this figure assumes that user A makes a call to user B by telephone 5.

First, when the user A makes a call to the user B, the user A sends SABME to the PBX1, and the user A receives the UA from the PBX1 to initialize the layer 2. After this, user A sends a "call setup" message to PBX1.

This causes the PBX 1 to send a "call setting" message to the user B in a broadcast UI frame.

Here, FIG. 2 is a flowchart showing the operation of each terminal of the user B having received the "call setting" message from the PBX 1.

That is, when the power is turned on, the terminal enters an idle state and waits until communication starts (step 201).

Then, as described above, when the "call setting" message for notifying the incoming call is received from the PBX 1 (step 202),
The terminal attribute included in this message is compared with the own terminal attribute (step 203) to determine whether communication is possible (step 204).

If the attributes match and communication is possible, the data link setting procedure by layer 2 is immediately executed. In this case, the terminal of the user B having the same attribute is the telephone 2
Is.

That is, User B's telephone 2 immediately sends PBX1 to SA.
BME is sent (step 205), and user B responds to this.
Phone 2 receives the UA from PBX 1 (step 20
6) The layer 2 is initialized, and thereafter, the telephone 2 of the user B sends a "call" message to the PBX 1 (step 207) and the telephone 2 rings a ring tone. Then, PBX1 calls "Call" to user A.
The message is sent.

After that, when the handset of the telephone 2 of the user B goes off-hook, the telephone 2 sends a “response” message to the PBX 1, and the PBX 1 also sends a “response” message to the user A. A call between A's telephone 5 and user B's telephone 2 is made by the B channel (step 208).

On the other hand, if the attributes do not match and communication is not possible, a delay of, for example, 250 to 500 msec is applied (step 209),
After that, the data link setting procedure by layer 2 is executed. In this case, the terminals of the user B whose attributes do not match are the data terminal and FAX3.

That is, after the "call" message is sent from the telephone 2 of the user B to the telephone 5 of the user A via the PBX 1, that is, after the positive response is made by the user B, the data terminal 4 and the FAX 3 of the user B are transmitted. From
SABME is sent to PBX1 (step 210), and in response, user B's data terminal 4 and FAX3 receive UA from PBX1 (step 211), layer 2 initialization is performed, and then user B is sent. Data terminal 4 and FAX3 to PB
A "release complete" message is sent to X1 (step 212).

User B's data terminal and FAX3 will be
The transmission of the DISC for X1 (step 213) and the reception of the UA for this (step 214) release the setting of the data link and return to idle.

As described above, in the communication system according to the present exemplary embodiment, when the terminal on the receiving side does not receive the call because the attributes do not match, the data link setting procedure is executed after delaying for a predetermined time. The matching terminal can preferentially notify the PBX1 of the response. Therefore, the PBX 1 can promptly know the incoming call reception from the terminal after the incoming call notification, and can promptly proceed with the connection processing.

Even if more terminals than can be processed simultaneously on the PBX1 side are connected on the transmission line, the terminals with the same attributes preferentially notify the PBX1 of the response. Can proceed with the connection processing with a terminal that can communicate with reliability, and communication failure due to the connection processing will not occur.

In addition, in the above-described embodiment, the terminal that performs communication is telephone communication, but it is needless to say that this may be the FAX 3, the data terminal 4, or the like. In the case of a terminal that automatically receives such an incoming call, it is possible to immediately send out a "response" message and start communication without sending out a "call" message.

Further, in the above-described embodiment, the case has been described in which the terminal attributes are compared and collated at the time of an incoming call and a positive response and a negative response are responded. However, the present invention is not limited to this, and even if the attributes match, they are temporarily If you can't accept the incoming call,
For example, even when the incoming call is rejected or the terminal is locally busy, the same operation can be performed.

In the above-described embodiment, the case where the operations by the layers 2 and 3 on the terminal side are both delayed at the time of the negative response is described, but the present invention is not limited to this. For example, on the network side (PBX), when the CPU is hierarchically designed so that the processing of layer 2 and layer 3 is performed by separate modules, all n terminals connected to the transmission line are simultaneously connected in layer 2 in layer 2. It becomes possible to process, and it is possible to simultaneously process a number of terminals less than n in layer 3.

In this case, even if the data link operation by the layer 2 is carried out in advance, only the message transmission by the layer 3 is delayed, and finally the transmission control to the network side is performed by the processing of the layer 3. Good.

By the way, since the portability of terminals is claimed in ISDN, there may be a case where there is no response to an incoming call notification due to the reason that the terminals are not connected on the transmission path. For this reason, CCITT recommendations say, for example, 4
If there is no response within a fixed time of about a second, it is stipulated that the incoming notification should be retransmitted for confirmation.

The second embodiment shown below is one in which the present invention is applied by paying attention to this point.

Here, the second embodiment is similar to the above-mentioned embodiments in CCITT Recommendations I.441 (layer 2) and I.451 (layer 3).
Frames, messages and procedures according to It should be noted that the layer 3 message includes a call number for identifying a plurality of calls. In the second embodiment, the fact that there is an incoming call is stored by storing this call number, and the call is retransmitted. Used to distinguish a waiting call from another call.

The communication system according to the second embodiment is also a system to which a basic interface in ISDN is applied, that is, PBX1 as shown in FIG. 3 in the conventional example.
, A plurality of users A, B ... Are connected to various communication terminals by a bus.
Has only a telephone 5 as a terminal, and the user B has a telephone 2, a fax 3 and a data terminal 4 as terminals. The call setup retransmission timer value when there is no response after the call setup transmission is set to 4 seconds.

FIG. 6 is a flow chart showing the operation of each terminal upon receipt of an incoming call in the second embodiment.

When the power is turned on, the terminal enters an idle state and waits until communication starts (step 601).

Then, as described above, when the "call setting" message for notifying the incoming call is received from the PBX 1 (step 602),
The terminal attribute included in this message is compared with the own terminal attribute (step 603), and it is determined whether communication is possible (step 604).

If the attributes match and communication is possible, the layer 2 data link setting procedure is immediately executed (steps 605 to 608).

On the other hand, if the attributes do not match and communication is not possible, such a data link setting procedure is not executed and the call number included in the "call setting" message is stored (step 60).
9) and start the 4-second timer (step 6)
Ten).

Then, when the "call setup" message is received again within 4 seconds (step 602), the call number included in the "call setup" message is compared and collated with the already stored call number (step 611). Here, if these call numbers match, that is, if the "call setup" message is retransmitted, the timer is stopped (step 612) and the data link setup procedure by layer 2 is executed (step 612).
613-617) and clear the stored call number (step 618).

If the call number included in the "call setup" message received within 4 seconds does not match the stored call number (step 611), this "call setup" message is not retransmitted. Since it is an initial one, it is treated as an initial “call setup” message.

If the "call setup" message is not received within 4 seconds (step 619), it is considered that the other terminal initially responded to the "call setup" message, and the stored call number is cleared (step 618). ), And becomes idle (step 601).

Here, FIG. 7 and FIG. 8 show an outgoing / incoming operation sequence when the terminal of the second embodiment is applied to the communication system having the configuration shown in FIG. In addition,
The examples in these figures assume that user A makes a call to user B by telephone 5.

First, when the user A makes a call to the user B, the user A sends SABME to the PBX1, and the user A receives the UA from the PBX1 to initialize the layer 2. After this, user A sends a "call setup" message to PBX1.

This causes the PBX 1 to send a "call setting" message to the user B in a broadcast UI frame.

Then, as shown in FIG. 7, when there is a terminal that has the same attribute and is communicable, the terminal immediately executes the data link setting procedure by layer 2. In this case, the terminal of the user B having the matching attribute is the telephone 2.

That is, User B's telephone 2 immediately sends PBX1 to SA.
BME is sent out, and user B's telephone 2 receives PBX1
By receiving the UA from the layer 2, the layer 2 is initialized, after which the telephone 2 of the user B sends a "call" message to the PBX 1 and the telephone 2 rings a ringing tone. Then, PBX1 calls "Call" to user A.
The message is sent.

After that, when the handset of the telephone 2 of the user B goes off-hook, the telephone 2 sends a “response” message to the PBX 1, and the PBX 1 also sends a “response” message to the user A. A call between A's telephone 5 and user B's telephone 2 is made by the B channel.

On the other hand, the data terminal 4 and the FAX 3 terminal whose attributes do not match do not execute such a data link setting procedure,
Start a 4-second timer and set up call until timeout
Wait for the message to be retransmitted. In this case, since the telephone 2 has already responded to the initial "call setup" message due to attribute matching, the "call setup" message is not retransmitted, so the release completion procedure is not executed, and the state remains as is. Become idle.

Further, as shown in FIG. 8, for example, when the telephone 2 is busy and there is no terminal having the same attribute, each terminal does not respond to the initial “call setup” message, and therefore the “call setup” message is retransmitted. Will be done.

Then, each terminal receives this retransmission “call setup” message within the set time of its own timer,
Perform the release completion procedure for the first time.

That is, SABME is sent from each terminal of user B to PBX1, while each terminal of user B is sent from PBX1 to UA.
In response to this, the layer 2 is initialized, and then each terminal of user B sends a "release complete" message to PBX1. Then, the PBX 1 notifies the telephone 5 of the user A as the reason of the disconnection message according to the priority order defined in CCITT Recommendation I.441, and the reason of the received “release completion” message is Disconnection recovery and link release.

Thus, in the communication system of the present embodiment, when there is a terminal with the same attribute, other terminals do not make a negative response,
Since the negative response is made only when there is no terminal having the same attribute, the PBX 1 can promptly know the reception of the incoming call from the terminal after the notification of the incoming call, and can promptly proceed with the connection process.

Even if more than the number of terminals that can be processed simultaneously on the PBX1 side are connected on the transmission line, only the terminals with the same attributes will notify the PBX1 of the response, so the PBX1 will be reliable. The connection processing can be performed with a terminal that can communicate with each other, and communication failure due to the connection processing does not occur.

In addition, in the above-described embodiment, the terminal for communication is telephone communication, but it may be FAX 3, data terminal 4 or the like. Then, in the case of such a terminal that automatically receives an incoming call, it is possible to immediately send a "response" message and start communication without sending a "call" message.

Further, in the above-described embodiment, the call number is used to identify whether or not the call is retransmitted, but this may be the calling number or the like.

Furthermore, 4 seconds was set as the timer value for waiting for retransmission, but considering the retransmission timer on the PBX side, it is the lowest probability that the retransmission timer value on this PBX side is exceeded and the same calling number is used. It may be equal to or less than the interval.

Further, in the present embodiment, the consistency comparison is not performed when the call setting is retransmitted, but the consistency comparison may be performed also when the call is retransmitted.

Further, in the present embodiment, the case where the release completion is transmitted only based on the result of the comparison of the consistency has been described, but the same can be performed when the release completion is transmitted when the terminal is busy such as local busy or communicating.

Even when the present invention is applied to the ISDN basic interface, the present invention can be realized within the range of the procedure defined by CCITT recommendation, and therefore the standard procedure is not spoiled.

[Effect of the Invention] As described above, in the communication system of the present invention, the terminal controls the transmission of the response to the incoming call based on the determination result of whether to accept the incoming call notified from the network. Not only can a quick connection process be realized, but when there is a terminal capable of receiving an incoming call, the incoming call can be surely made.

[Brief description of drawings]

FIG. 1 is a sequence of call originating / receiving operations of a system according to an embodiment of the present invention, FIG. 2 is a flow chart showing an operation of a terminal according to FIG. 1, and FIG. FIG. 4 shows a call originating / receiving operation sequence of a conventional bus communication system, FIG. 5 shows a channel connection between a PBX and a terminal, and FIG. 6 shows an operation of a terminal according to a second embodiment of the present invention. A flow chart, FIG. 7 and FIG. 8 are an outgoing / incoming operation sequence of the system according to the second embodiment of the present invention. 1 ... PBX, 2,5 ... phone, 3 ... FAX, 4 ... data terminal.

Claims (1)

[Claims] 1. A plurality of terminals are connected in a bus-like manner on a transmission line connected to a predetermined network, and the network simultaneously notifies each of the terminals of an incoming call in a broadcast format and accepts the incoming call. In a communication system in which a line connection is made to a terminal that has transmitted an affirmative response of the above, when each terminal determines whether to accept an incoming call notified from the network, and when it is determined to accept an incoming call A means for controlling transmission so that an affirmative response is sent to the network side, and when it is determined that the incoming call is not accepted, a negative response is sent to the network side after a predetermined period without responding to the incoming call. A communication system comprising: