JPH06101733B2 - ISDN subscriber line multiplex transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to bidirectional time division multiplexing for connecting a switching device and a plurality of network terminators connected at a reference point S to a terminal compliant with CCITT's I series recommendation. The present invention relates to an ISDN subscriber line multiplex transmission method capable of efficiently using a subscriber transmission line by a demand assign method.

“Conventional Technology” Multiplexing of transmission lines is a technique that has been conventionally used as a means of making the transmission lines economical. Further, in order to improve the channel use efficiency of the multiplexed transmission path, a so-called channel demand assign method, in which a channel is allocated every time there is a communication request and the channel is released after the communication is finished, is a technique that has been often used conventionally.

According to the I-series recommendations before the 1986 edition, the basic access interface using the metallic line between the network terminating equipment and the exchange does not have a function of multiplexing the transmission line between the plurality of network terminating equipments and the exchange. . In addition, although the primary group interface is defined as a multiplexed transmission line between the central office switch and mainly the private exchange, in order to connect multiple network terminators directly to the multiplexed transmission line, the transmission line access The above-mentioned contention elimination is required, and the primary group interface, which is premised on point-to-point communication, does not have that function. On the other hand, a demand for time slots using a layer-1 activation / shutdown procedure for each call to reduce station power supply to terminals conforming to the I series recommendation by using a time division wireless transmission line between a plurality of network terminating equipments and exchanges. Although the assignment has been proposed, since the Layer 1 start / stop procedure is not originally set for demand assignment, use of the shared control channel when multiple network terminators access the exchange through the multiplexed transmission line. However, if the problem of elimination of contention, which is indispensable for practical use, has not been solved and there is no time slot for the D channel on the transmission path, there is no means to notify the terminal of the congestion factor by the layer 1 start / stop procedure alone. However, there is a problem that the subscriber cannot distinguish from the transmission path failure. In addition, if a control channel dedicated to an individual network terminating device, rather than a shared channel, is always kept on the transmission line, no conflict will occur.
This is an impractical solution because the effective use of the transmission line is not achieved and the number of network terminators connected to the transmission line is restricted.It is a practically essential condition to provide a shared control channel and eliminate contention. Is.

[Problems to be Solved by the Invention] As described above, in a system that realizes a subscriber line multiplex transmission line by the demand assign method in ISDN, multiplexing by a plurality of network termination devices unique to the multiplex transmission line is performed. There are practical problems such as how to eliminate access conflict and how to send congestion information to a terminal according to the usage status of a time slot.

The present invention is premised on the use of terminals conforming to the I-series recommendations, and practically indispensable conflict elimination in order to realize demand assignment of time slots on multiplexed transmission lines by a layer 1 start / stop procedure for each call. A subscriber line multiplex transmission method for terminating a procedure for securing a time slot for transmitting congestion information between a switch and a network terminating device.

"Means for Solving the Problem" The present invention relates to information transmission / reception between a plurality of network terminating devices and exchanges, and relates to allocation and release of time slots for each call on a time division multiplex transmission line by releasing D channel allocation release in I series. Follow the recommendation-compliant layer 1 start / stop procedure, and
The exchange is instructed to each network terminating device by receiving layer 3 information at the exchange, and slotted ALOHA is provided for eliminating contention from a request from the network terminating device.
Applying the method, the network terminator activates the time limit timer at the time of sending a signal to the exchange, and if no confirmation is received from the exchange within a certain time, it is determined that contention has occurred due to timeout and the information is retransmitted to the exchange, In addition, when the number of D channels used on the transmission path exceeds a certain number, a time slot for the remaining D channels is secured and used for layer 3 congestion information transfer to a terminal newly requesting the D channel. And

[Operation] According to this invention, CCITT Recommendation I.4 is provided between the terminal and the network terminating device.
By applying the call start / stop procedure for each call according to the S point specification of 30, the elimination of contention between multiple network terminators, the release of time slot allocation, and the securing of time slots during congestion are between the exchange and the network terminator. By doing so, there is an effect that a terminal conforming to the I series recommendation can be connected to the multiplexed transmission line shared between the network terminating devices without affecting the S point specifications.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

Among the terms used in this explanation, INFOO, INFO1, IN
FO2, INFO3, INFO4 are those specified in CCITT Recommendation I.430,
Layer 1, Layer 2, Layer 3, Layer 1 start and stop status,
D channel, B channel, layer 3 release and release complete message, layer 1 MPH-stop-request primitive,
S point, basic access interface, channel identifier,
The reason indication uses the translation in the TTC standard corresponding to the I series recommendation.

FIG. 1 is a schematic configuration diagram of an apparatus to which an ISDN subscriber line multiplex transmission system according to an embodiment is applied. The exchange 4 is connected to a plurality of network terminators 2a and 2n by a multiplexing transmission line 3, and time limit timers 6a and 6n are added to each of the network terminators.
Terminals 1a, 1b, 1n and 1m are connected to 2n via S points 5a and 5n of the basic access interface, respectively.

FIG. 2 shows the time division frame on the multiplexed transmission line 3,
The format examples of the upstream (transmission from the network terminating device to the exchange) frame and the downstream (transmission from the exchange to the network terminating device) frame are respectively assigned to the transmission bands in one direction. For example, on a CATV coaxial cable, two 6 MHz TV transmission bands are assigned to the upstream and the downstream, respectively. Here, the control channels 11a and 11b are used for information transfer between the exchange 4 and the network terminating devices 2a and 2n, and are shared by all the network terminating devices, and each time slot 12a, 12n, 13a and 13n is an exchange. It is used for information transfer as D and B channels between a terminal and a terminal. The network terminator performs drop (extraction) / insertion (insertion) for the time-division frame of the allocated time slot, and the information in the time slot is transferred to the terminal. It is used for communication between exchanges, and a pair of time slots of upstream and downstream frames are used for bidirectional information transmission and reception between exchanges and terminals. When each time slot is assigned, it is exclusively used by the network terminating device, and is not used simultaneously by different network terminating devices, so that there is no conflict regarding the use of the time slot.

D channel allocation procedure at the time of calling the terminal If the layer 1 of the S point 5a at the time of calling the terminal 1a is in the stopped state,
An INFO1 signal is sent from the terminal 1a to the network terminating device 2a, and the network terminating device 2a receives it and sends the signal to the exchange 4 to the uplink control channel 11a.
To request a D channel time slot. Switch 4
Responds to the time slot request to notify the network terminating device 2a of the D channel time slot using the downlink control channel 11b. The network terminating device 2a starts access to the allocated time slot, sends INFO4 to the terminal 1a, completes the activation of the layer 1, and the layer 2 communication becomes possible.

When a new call is made from the terminal 1b, since the terminal 1b is in the layer 1 activated state, the layer 2 communication is immediately started without issuing INFO1. In this case, the information of layer 2 and above is transferred through the D channel allocated earlier, but there is no problem because the D channel competition between the terminals 1a and 1b is arbitrated at the S point 5a by the I series recommendation.

Procedure for eliminating contention between network terminators The contention between network terminators 2a and 2n occurs by sending D channel request information to the exchange using the same upstream control channel 11a. For example, this occurs when the layer 1 at the S points 5a and 5n in the network terminating devices 2a and 2n is in a stopped state and the terminals 1a and 1n simultaneously call. Uplink control channel 11a when D channel is requested
The request source network termination device identifier is set in the
When a conflict occurs, a plurality of network terminating equipment identifiers are overlapped on the uplink control channel 11a. Therefore, the network terminating equipment cannot make a request for retransmission because the network terminating equipment cannot be deciphered and cannot be discriminated from which network terminating equipment. Therefore, it is judged that contention has occurred in each of the network terminators 2a and 2n. The slotted ALOHA method is applied to eliminate this competition.

That is, when the D channel is requested, the time limit timers 6a and 6n are activated in the network terminators 2a and 2b, respectively, and the acceptance confirmation information from the exchange is received in each network terminator via the control channel 11b on the downlink frame within a certain time. If it does not exist, it is judged as a contention due to a timeout, and the uplink control channel 11
Use a to request allocation of D channel time slots. It should be noted that the number of control channels may be plural, and in this case, a procedure for randomly selecting control channels at the time of contention is added.
Further, when it is desired to use an arbitrary time slot as a control channel, a method of broadcasting an empty time slot number on the downlink control channel can be considered.

D-channel time slot allocation procedure when receiving a call to the terminal The network terminating equipment identifier and the time slot number are transmitted from the exchange to the downlink control channel 11b, and the network terminating equipment designated by the identifier transmits the time slot designated by the time slot number. Access to S and S
INFO2 that should activate the layer 1 of the point is transmitted to the call-in terminal, waits for INFO3 from the call-in terminal, sends out INFO4, and then starts communication of the layer 2. If the time slot for D channel is already allocated to the network terminating device, the exchange directly starts layer 2 communication using the allocated D channel without newly securing the D channel.

B channel time slot allocation procedure Regarding the allocation of time slots for B channel, the exchange receives the channel request by the layer 3 communication from the terminal regardless of whether the call originates from the terminal or the call is received from the terminal. Is sent to the network terminating device via the downlink control channel 11b as an assigned time slot by assigning the corresponding B channel time slot number, and the network terminating device starts access to the B channel time slot and performs layer 3 communication between the exchange and the terminal. Is started.

B channel time slot release procedure To release the B channel time slot, the layer 3 disconnection message is sent and received between the switch and the terminal, and then the switch sends the B channel time slot number to the network terminating device.
Send via 11b to stop access to the timeslot.

Procedure for releasing D channel time slot Release of D channel time slot is recommended in I series I.43.
Due to the MPH-Stop-Request Primitive regarding Layer 1 stop described in 0, the exchange instructs the designated network terminating device to stop the access of the D channel via the control channel 11b, and in response, the network terminating device receives the D The access to the channel is stopped and INFO0 is sent to the terminal to stop the layer 1.

FIG. 3 shows the terminal 21, the network terminating device 23, and the exchange 25 when the terminal is called.
The following is an example of the exchange of information between the terminals. The process of the network terminating device 23 will be described as an example.
(26) After receiving, the timer is activated (27), the D channel time slot request (28) is made to the exchange using the control channel, and the timeout occurs before (31) receiving the allocation instruction from the exchange on the control channel ( 29) Therefore, after requesting the D channel after a random time (30), receiving the allocation instruction (31) from the exchange, sending INFO2 (32) to the terminal 21, INFO3 (33) from the terminal, INFO4 (when receiving) 34) to enable layer 2 communication using D channel between exchange terminals (3
5)

Processing when D channel time slots are congested When a D channel request is made, at least one or more idle D channel time slots are secured in the exchange as a countermeasure against the inability to allocate because all D channel time slots are in use. For the D channel request at the time of congestion, the reserved time slot is allocated as the D channel, and a layer 3 release message is sent through this to request disconnection of the D channel request terminal. Based on this, disconnect Layer 2 and Layer 1 in that order.
Stop.

FIG. 4 shows a part of the processing when there is a terminal call when the D channel is congested. The example shown in FIG. 3 corresponds from the call to the layer 2 communication state. When layer 3 communication using the channel is started (46), the exchange displays the reason for the D channel congestion and sends the layer 3 release message and the terminal release completion message (47). 2 After sending and receiving the disconnection message (48), the exchange sends a D channel release request to the network terminating device via the control channel (49).
The network terminator IN indicates to the terminal that Layer 1 has been disconnected from the exchange.
Layer 1 is stopped by sending FOO (51) and the terminal sending INFOO (52). Further, the network terminating device stops (50) D channel access due to disconnection of layer 1.

FIG. 5 shows a configuration example of the network terminating device 61. The S interface control circuit 63 is connected to a terminal conforming to the I series recommendation via the S / T interface 62, and the output D channel 64, B1 channel 65, B2 channel 66 of the S interface control circuit is connected by the time slot multiplex insertion circuit 70. The transmission timing control circuit 72 multiplexes the data and sends it out through the modulation transmission circuit 74 in synchronization with the upstream communication timing of the transmission line 77. The received frame is taken from the transmission line to the network terminating device via the reception demodulation circuit 75. After adjusting the timing by the reception timing control circuit 73, the time slot extraction / separation circuit 71 extracts the time slot to be taken into the terminal device, and divides into the D channel 67, B1 channel 68, B2 channel 69, and the S interface control circuit. Is input and sent to the S / T interface. Each circuit is signal line 1 (78), 2 (79), 3
(80), 4 (81) is connected to the common control device 76.

The information of the control channel according to the present invention is converted into a layer 1 signal on the S interface by the S interface control circuit via the signal line 1, and the layer 1 signal on the S interface is signal line 1 by the S interface control circuit. After being converted into the above signal and edited into control channel information by the common control device, it is sent to the time slot multiplex insertion circuit via the signal line 2 and inserted into the frame. If the time limit timer shown in FIG. 1 is also incorporated in the common control device, the control device can perform contention processing regarding the control channel. The device configuration on the exchange side is configured so as to be able to face a plurality of this device. The processing at the time of D channel congestion can be realized as a function of the exchange side.

[Advantages of the Invention] As described above, according to the present invention, since it is possible to connect to a demand-assignment-type multiplexed transmission line without changing the S point specification of a terminal conforming to the I series recommendation, It is a very useful method in practice because it can use terminals conforming to the I series recommendation while making the economy economical. As a specific example, it can be considered as an effective method for a system in which a plurality of subscriber premises equipments are accommodated on a broadband transmission line such as a CATV network.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an ISDN subscriber line multiplex transmission system device, FIG. 2 is a diagram showing an example of a time division frame format, FIG. 3 is a diagram showing a signal sequence when a terminal is called, and FIG. FIG. 5 is a diagram showing a signal sequence for a terminal call when D channel congestion occurs, and FIG. 5 is a block diagram showing a configuration example of a network terminating device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04Q 5/00 8627-5K

Claims (2)

[Claims] 1. A TEI compliant with CCITT's I-series recommendation or
A transmission method in a bidirectional time division multiplex transmission line connecting a plurality of network terminating devices connected to an ISDN terminal equivalent to a TA at a reference point S and a switch, wherein the network terminating device and the switch are: It has a function of dropping / inserting information into a control channel and a time slot on the transmission line of the time division multiplexing system, and if the layer 1 at the point S is in a stopped state when the terminal makes a call, an activation signal from the terminal. Upon receiving the request, the network terminating device requests the exchange for a D channel time slot using the uplink control channel, and when the exchange receives the request, the exchange notifies the network terminating device of the D channel time slot through the downlink control channel, and the network is terminated. The terminating device receives the above-notified D
Initiate access to channel timeslot, INFO4
To the calling terminal to complete the start-up of layer 1, the communication of layer 2 is started, the network terminating device has a timed timer, and the timer is started when the D channel time slot is requested, If the acceptance confirmation information of the request is not received by the time-out of the above timer, the request time slot is transmitted again on the uplink control channel after the lapse of random time, and the D channel time slot allocation when the terminal receives the call is performed from the exchange to the downlink control channel. The network terminating equipment identifier and the time slot number are transmitted to the network terminating equipment, and the network terminating equipment designated by the identifier starts access to the time slot designated by the time slot number, and the called terminal receives the layer 1 at the S point. After sending INFO2 to activate, wait for INFO3 from the called terminal and send INFO4, then layer 2
The communication is started, and the assignment of B channel time slot is received by the exchange in response to the request from the terminal by layer 3 communication in both the case of the call originating from the terminal and the call receiving of the terminal, and the exchange selects the idle B channel. Then, the B channel time slot number is assigned as a time slot and sent to the network terminating device on the downlink control channel. The network terminating device starts access to the B channel time slot and the layer 3 is exchanged between the exchange and the terminal.
Communication is started and the B channel time slot is released by sending and receiving a layer 3 disconnection message between the exchange and the terminal, and then releasing the B channel release information from the exchange to the network terminating device connecting the terminal to the downlink control channel. , The network terminator stops access to the B channel time slot, and the release of the D channel time slot is caused by the MPH-halt-request primitive regarding the layer 1 halt, from the switch to the designated network terminator. ISDN subscriber line multiplex characterized by instructing to stop access to D channel in response to the request, and in response to this, the network terminating device stops access to the D channel, sends INFO0 to the terminal, and stops layer 1 Transmission method. 2. On the transmission path, at the time of requesting a D channel, the exchange reserves at least one free D channel time slot, and reserves it for a D channel request at the time of congestion. The time slot is allocated as a D channel, and a layer 3 release message is sent through the time slot to request the disconnection of the D channel requesting terminal.
2. The ISDN subscriber line multiplex transmission method according to claim 1, wherein layer 2 and layer 1 are disconnected and stopped in this order based on the series recommendation.