JPH02183644A - Isdn subscriber line multiplex transmission system - Google Patents

Abstract

PURPOSE:To connect a terminal equipment in compliance with the I series recommendations to a multiplex transmission line shared among network terminators independently of the specifications at a point S by applying exclusion of contention between plural network terminators, assignment release of a time slot and acquisition of the time slot at congestion between an exchange and the network terminator. CONSTITUTION:An exchange 4 is connected to plural network terminators 2a and 2n, times 6a and 6n are added to each network terminator and terminal equipments 1a, 1b, 1n, 1m are connected to the network terminators 2a and 2n via points S 5a, 5n of the basic access interface. Then the terminal equipments are connected to a multiplex transmission line 3 of the demand assign system without revising the specifications of the terminal equipment at the point S in compliance with the I series recommendations. Thus, the system is advantageous practically while the transmission line 3 is economized at the point that terminal equipment in compliance with the I series recommendations is used.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention applies to CCITT's l series recommendation 1! ! An ISDN subscriber who can efficiently use a bidirectional time-division multiplex subscriber transmission line that connects a terminal at a base, a plurality of network termination devices connected at a reference point S, and an exchange by a demand assignment method. Related to line multiplex transmission system.

"Prior Art" Multiplexing of transmission lines is a technique that has been used in the past as a means of making transmission lines more economical. Furthermore, in order to improve the channel usage efficiency of multiplexed transmission paths, a so-called channel demand assignment method has been often used in the past, in which a channel is assigned every time there is a communication request, and the channel is released after the communication is completed.

According to the summer series recommendations prior to the 1986 edition, basic access interfaces that use metallic wires between network termination equipment and exchanges do not have the ability to multiplex transmission paths between multiple network termination equipment and exchanges. . In addition, primary group interfaces are specified as multiplexed transmission lines between horse exchanges and mainly private exchanges, but in order to directly connect multiple network termination devices to multiplexed transmission lines, transmission line access The above contention elimination is necessary, and the primary group interface, which assumes point-to-point communication, does not have this function. On the other hand, time-shared wireless transmission channels are used between multiple network termination devices and exchanges, and a time-sharing method using a Layer 1 startup/stop procedure for each call is used to reduce the power supplied to stations to m terminals. Demand assignment has been proposed, but since the Layer I start/stop procedure is not originally a procedure set for demand assignment, it is necessary to use a shared control channel when multiple network terminal equipment accesses an exchange through a multiplexed transmission path. If the problem of contention elimination, which is essential in practice regarding the use of Since there is no means of notification, there are problems such as the subscriber being unable to distinguish it from a transmission line failure. Note that if a control channel dedicated to each network termination device is always provided on the transmission path instead of a shared channel, contention will not occur, but the effective use of the transmission path will not be achieved and the number of network termination devices connected to the transmission path will be limited. Therefore, it is an impractical solution, and providing a shared control channel and eliminating contention are practically essential conditions.

``Problems to be Solved by the Invention'' As stated above, in a system that implements subscriber line multiplexed transmission lines using the demand assignment method in ISDN, multiple network There are practical problems such as how to eliminate contention in access and how to send congestion information to terminals depending on the usage status of time slots.

This invention assumes the use of a terminal that complies with the Series Recommendation, and is designed to eliminate competition, which is practically essential in realizing time-scott demand assignment on multiplexed transmission paths using a layer l activation/stop procedure for each call. The present invention provides a subscriber line multiplex transmission system in which the procedure for securing time slots for transmitting congestion information is terminated between an exchange and a network termination device.

[Means for Solving the Problems] This invention relates to the transmission and reception of information between a plurality of network termination devices and exchanges, and the allocation and release of time slots for each call on a time division multiplex transmission path. B
Channel (i1 talk channel) assignment is performed by instructing each network termination device to release by receiving layer 3 information at the exchange, and applying the slotted ALOHA method to eliminate competition for requests from the network termination device. Activates a timer when sending a signal to the exchange, and
If reception confirmation is not received from Ai within a certain period of time, it is determined that a conflict has occurred due to a timeout, and the information is retransmitted to the exchange, and if the number of D channels used on the transmission path exceeds a certain number, the remaining D channels are used. It is characterized in that it is used to transfer layer 3 congestion information to a terminal newly requesting a D channel by securing a time spot.

"Operation" According to the present invention, between a terminal and a network termination device, a layer l start/stop procedure is applied for each call in accordance with the three-point specifications of CGITT Recommendation 1.430, eliminating conflicts between multiple network termination devices, By opening the time slot allocation and securing the time slot during congestion between the switch and the network termination equipment, ■ Terminals that comply with the series recommendations can be placed at three points on the multiplexed transmission line shared between the network termination equipment. This has the effect of allowing connections without affecting specifications.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Of the terms used in this explanation, INFOOIN
FOL, INFO2, INFO3, INFO4 are CC
As specified in ITY Recommendation 1.430, Layer 1. Layer 2. Layer 3. Layer l start and stop states, D channel, B channel, layer 3 release and release completion messages, layer 1 MP) l-stop-request primitive,
3 points, basic access interface, channel identifier,
The reason expression uses translated words in the TTC standard that correspond to the I-series recommendations.

FIG. 1 is a schematic diagram of a device 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 termination devices 2゜2n by a multiplex transmission line 3,
Each network termination device has a timer 6, . 6. is added, and the network termination device 2. ．． 2. Terminal 1. , lb, 1a+ 1
．． 8 points of basic access interface 5. ．．
Connected via 5fi.

Figure 2 shows the time-division frames on the multiplexed transmission line 3.
Examples of formats for upstream (transmitted from the network termination equipment to the exchange) and downlink (transmitted from the exchange to the network termination equipment) frames assigned to one-way transmission bands are shown.For example, 6M1 on a CATV coaxial cable. (T of z
Two V transmission bands are allocated one for uplink and one for downlink.

Here, control channel 11. , llb is the switch 4 and the cable termination M2. .

It is used for information transfer between time slots 12. ．． 12. .

13,,13. is used as a B channel to transfer information between the exchange and the terminal, and the network terminal equipment performs dropping (extraction) and insertion (insertion) into the time-division frame of the allocated time slot, and the information in the time slot is transferred to the terminal. The time slots of the up and down frames are used in pairs for two-way information transmission and reception between the switch and the terminal. Once allocated, each time slot is used exclusively by a network terminating device, and different network terminating devices are never used at the same time, so there is no conflict regarding the use of the time slot.

■Procedure for D channel allocation when terminal calls are made If layer 1 of point S 51 is in a stopped state when terminal 1s makes a call, terminal 1. An INFOL signal is sent from the network terminal device 2° to the network terminal device 2. is then exchanged [upstream control channel 1 to 4]
1. to request a D channel time slot. Switch 4 transmits downlink control channel 1 according to the time slot request.
1. The network terminal device 21 is notified of the D channel time slot using the D channel time slot. The network terminal device 21 starts accessing the allocated time slot, sends INFO4 to the terminal 11, completes the activation of the layer, and layer 2 communication becomes possible.

Now, create a new terminal 1. When a call is made from terminal 1, since terminal 1 is in the layer 1 activated state, it immediately starts layer 2 communication without issuing an INFOL. In this case, information on layers 2 and higher is transferred through the previously allocated D channel, but the D channel contention between terminals 1 and lb is
8 points and 5 points based on series recommendation. There is no problem as it will be arbitrated.

■ Procedure for eliminating contention between network termination devices Network termination device 2. ．． 2. The contention between the same uplink control channel 11. This occurs by sending D-channel request information using the . For example, network termination device 2. ．． 2. 8 points in l5. ．． 5. Layer 1 of terminal 1 is in a stopped state, and terminal 1. ．．
1. Occurs when there are simultaneous calls. When a D channel is requested, the request source network terminal equipment identifier is set in the control channel 11□, but when a conflict occurs, the exchange 4
, because the multiple network terminal device identifiers overlap, they cannot be decoded and it is not possible to determine which network terminal device the information is from, and it is not possible to request retransmission to the network terminal device. Therefore, each network terminal device 2. ,2
．． It will be determined that a conflict has occurred. A slotted ALOHA method is applied to this contention elimination.

That is, when a D channel is requested, the time-limited timers 6, . 6. is activated, and within a certain period of time, each network terminal equipment receives confirmation information from the switch and transmits the control channel 11. on the downlink frame. If no reception is received via the uplink control channel 11., it is determined that there is a conflict due to a timeout, and the uplink control channel 11. The allocation of D channel time slots is requested using . Note that the number of control channels may be plural, and in this case, a procedure for randomly selecting a control channel at the time of contention is added. Furthermore, if it is desired to use an arbitrary time slot as a control channel, a method of broadcasting an empty time slot number on a downlink control channel may also be considered.

■ D channel time slot allocation when a call arrives at a terminal is downlink '41 ■ Channel 11 in the case of an incoming call from a procedural switch.
, the network terminal device identifier and time slot number are set in the specified network P, and the end device starts accessing the specified time slot and sends INFO2 to the terminal to activate the eight layer 1 points. , INFO from the terminal
3, sends INFO 4, and then starts layer 2 communication. If a time slot for the D channel of the network P end-packing device has already been allocated, the exchange directly starts layer 2 communication using the already allocated D channel without securing a new D channel.

■ B channel time slot allocation procedure Regarding time slot allocation for B channel, in both cases of terminal call origination and terminal call arrival, the exchange receives a channel request from the terminal through layer 3 communication, and assigns an empty B channel time slot. This can be achieved by selecting the B channel time slot number, sending the corresponding B channel time slot number to the network terminal equipment via the control channel llb, and, after the allocation is completed, notifying the channel identifier information from the exchange to the terminal using layer 3 information.

■ B channel time slot release procedure To release the B channel time slot, after sending and receiving a layer 3 disconnection message between the exchange and the terminal, the exchange transmits the B channel time slot number to the network terminal device in control channel 11. to stop access to Time Thronet.

■ D channel time slot release procedure D channel time slot release is based on the important stop-request primitive regarding layer 1 stop described in I-series recommendation r, 430, and the control channel is sent from the AC IA device to the designated network terminal equipment. 11° to stop access to the D channel, and in response to this, the network terminal equipment stops access, sends INFOO to the terminal, and stops layer 1.

FIG. 3 shows an example of the exchange of information performed between the terminal 21, the network P: the termination device 3, and the exchange 25 when a terminal call is made.
After receiving INFOL (26) from , start the timer (2
7) L uses the control channel to request the D channel time slot (28) from the exchange, and the allocation from the exchange times out (29) before the instruction is received on the control channel (31), so the D channel is allocated after a random time. As requested again (30), the allocation from the exchange was instructed (31),
Send INFO2 (32) to the terminal 21 and input from the terminal
FO3 (33), upon reception, transmits INFO4 (34) to enable layer 2 communication using the D channel between the tAi terminals (35).

■ Processing when D channel time slot congestion occurs When a D channel is requested, all D channel time slots are in use and cannot be allocated. After securing a slot and allocating the reserved time slot in response to a D channel request during congestion, a release message with an indication of the reason for no available line is sent as layer 3 information. Request the terminal to be disconnected, and then disconnect/stop layer 2 and layer 1 in that order based on the ■ series recommendations.

Figure 4 shows part of the processing when a terminal call is made during D channel width comparison. When layer 3 communication using the D channel starts (46), the exchange sends a layer 3 release message with a reason indication of D channel congestion, the terminal sends a release completion message (47), and then the D channel After the layer 2 disconnection message is sent and received via the exchange (48), the
A channel release request is sent to the M4 terminating device on the control channel (49), and the network terminating device sends INFOO (51) indicating layer 1 disconnection from the exchange to the terminal, and the terminal sends INFOO.
By sending (52), layer 1 is stopped. Further, the network terminal equipment stops D channel access (50) due to the layer 1 disconnection.

FIG. 5 shows an example of the configuration of the network termination device 61. The S interface control circuit 63 connects terminals and S/
The output D channel 64 . of the S interface control circuit is connected via the T interface 62 . B1 channel 65
．． B2 channel 66 is a time slot multiple insertion circuit 70
The received frame is multiplexed by the transmission timing control circuit 72 and sent out through the modulation transmission circuit 74 in accordance with the uplink communication timing of the transmission path 77, and the received frame is taken from the transmission path to the network termination device via the reception demodulation circuit 75. After the timing is adjusted by the reception timing control circuit 73, the time slot extraction and separation circuit 71 extracts the time slot to be taken into the terminal device, and outputs the D channel 67, Bl channel 68 . It is divided into the B2 channel 69 and becomes the power of the S interface control circuit and is sent to the S/T interface. Each circuit is signal cotton 1 (78), 2 (7
9), 3(80).

4 (81) to the common control device 76.

Information on the control channel according to the present invention is converted into a layer 1 signal on the S/T interface by the S interface control circuit via the signal line l, and the layer 1 signal on the S/T interface is sent to the S interface control circuit. is converted into a signal on signal line 1, and converted into control channel information by the common control device)! After being collected, the signals are sent to the time slot multiple insertion circuit via the signal line 2 and inserted into the frame.

If the time limit timer shown in FIG. 1 is also built into the common control device, the control device can perform contention processing regarding control channels. The equipment configuration on the exchange side will be configured as one facing a plurality of the devices. Note that the processing at the time of D channel congestion can be realized as a function on the exchange side.

r Effects of the Invention J As explained above, according to the present invention, it is possible to connect to a demand-assign multiplexed transmission line without making any changes to the 8-point specifications of a terminal that complies with the Series Recommendations; This method is extremely useful in practice because it allows the use of terminals that comply with the ■ series recommendations while also making it more economical.

As a specific example, it can be considered as an effective method for a system such as CATVM4 in which a plurality of subscriber premises equipment is accommodated on a broadband transmission path.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the equipment configuration of ISDN subscriber line multiplexing transmission system, Fig. 2 is a diagram showing an example of the format of a time division frame, and Fig. 3 is a diagram showing a signal sequence when a terminal calls.
FIG. 4 is a diagram showing a signal sequence for terminal call origination during D channel congestion, and FIG. 5 is a block diagram showing an example of the configuration of a network termination device. O 1 Figure O 2 Figure

Claims (2)

[Claims] (1) In a bidirectional time-division multiplex transmission line that connects an ISDN terminal equivalent to TE1 or TA that complies with CCITT's I series recommendations, multiple network termination devices connected at a reference point S/T, and an exchange. , regarding time slot allocation and release for each call on the transmission path, that is, time slot demand assignment processing, the D channel allocation on the ISDN basic interface is released in accordance with the Layer 1 activation/stop procedure in accordance with the I-series recommendations; The exchange instructs each network termination device to release allocation of the B channel by interpreting layer 3 information, and performs slotted AL to eliminate contention for simultaneous requests from multiple network termination devices.
An ISD that applies the OHA method and, if reception confirmation is not received from the exchange within a certain period of time after sending it to the exchange, it is determined that a conflict has occurred and the requested information is retransmitted to the exchange.
N subscriber line multiplex transmission system. (2) D as a process when D channel congestion occurs on the transmission path.
2. The ISDN subscriber line multiplex transmission system according to claim 1, wherein a certain number of channel time slots are reserved and allocated to a terminal newly requesting a D channel and used for transferring congestion information.