JPH0638617B2 - Digital exchange that accommodates high-speed circuit switching terminals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a 64 Kbps which accommodates a subscriber line of an ISDN primary rate access interface and is communicated via a B channel of the ISDN primary rate access interface. A general circuit-switched call that uses the following bandwidth and a high-speed circuit-switched call that uses a bandwidth exceeding 64 Kbps are separated, the general circuit-switched call is exchanged, and the high-speed circuit-switched call is multiplexed to be exchanged by the upper-tier switching center. The present invention relates to a digital exchange that accommodates a high-speed circuit switching terminal that converts and transmits.

[Conventional technology]

In CCITT, I. Define the user network interface for ISDN. With the standardization of the series recommendations, the introduction of ISDN is being accelerated in each country. In addition to conventional telephones, ISDN also provides packet terminals or high-speed circuit switching services with wider bandwidth.

However, ISDN cannot be realized immediately after its use is decided, and various problems need to be solved in order to construct ISDN. As one of the problems, there is a method of configuring a subscriber exchange described below.

In ISDN, various services can be provided by the same subscriber interface. To do so, firstly it is necessary for the switch to be able to accommodate the user network interfaces in the above CCITT recommendations, and secondly for calls of various nature to and from these ISDN subscribers, eg circuit switched. , It is necessary to be able to accommodate a call having both attributes of high-speed circuit switching as a switch.

[Problems to be solved by the invention]

However, most of the existing exchanges are for telephones, and even if they are digital exchanges, it is necessary to add an ISDN subscriber interface to the subscriber side to accommodate ISDN subscribers. Furthermore, even if ISDN subscribers are accommodated, it is not possible to easily support both circuit switching and high-speed circuit switching with existing exchanges.
In other words, existing telephone exchanges are capable of circuit switching, but high-speed circuit switching uses different bandwidths, so there are various problems to be solved in using this to perform high-speed circuit switching. . For example, in the case of high-speed circuit switching, a time slot sequence, which is not a problem in a call using a normal B channel whose baseband is 64 Kbps.
The need to preserve integrity (TSI) arises. This has a problem in that the order of time slots is not always guaranteed when a high-speed circuit switched call is connected using a plurality of B channels.

This problem can be dealt with to some extent by the existing circuit switch, but for that purpose, the burden of software, the increase of the call loss rate, etc. have been unavoidable.

Therefore, in order to provide a high-speed circuit switching service to ISDN subscribers, the subscriber switching system is replaced with a dedicated one for ISDN subscribers capable of supporting both circuit switching and high-speed circuit switching, or a switching system dedicated for high-speed circuit switching separately. (There are two possible methods: placing this high-speed circuit switch on the subscriber level or placing it on the transit level), but the circuit-switched call is to this circuit-switch, and the high-speed circuit-switched call is to the high-speed circuit. It is necessary to perform either control so as to connect to the exchange according to the attribute of the call.

This method is simple as a network configuration method, and is the most preferable method from the viewpoint of ISDN subscribers in terms of service. Therefore, it will be common when ISDN becomes popular in the future. However,
In this way, all existing exchanges cannot be used for ISDN subscribers. So applying this method right now is not always economical.

On the other hand, if the method is adopted, the switch portion of the existing telephone digital exchange can be used as the circuit exchange switch. In this sense, from the standpoint of promoting the introduction of ISDN, the method can be said to be more realistic, especially in the early stages of ISDN introduction.

Even if the above method is adopted, there is a further problem as to where in the network the exchange dedicated for high-speed circuit switching is placed, as mentioned above. Depending on the traffic ratio between high-speed circuit-switched calls and circuit-switched calls, it is desirable to place them on the subscriber level if the ratio of high-speed circuit-switched calls is high, or on the relay level if the ratio of circuit-switched calls is high. Generally, at the early stage of ISDN implementation, it is estimated that the traffic of high-speed circuit calls is considerably smaller than that of circuit-switched calls, and the high-speed circuit switch is placed on the transit ladder so that subscribers can access it as needed. Are considered to be economical.

In this case, the trunk line (that is, Toll in ATT terminology)
In order to operate the Connecting Trunk economically, the trunk line can be commonly used for the circuit switched call and the high speed circuit switched call, and the channel used by the high speed circuit switched call and the circuit switched call on the multiplexed trunk line. It is desirable to be able to change the ratio of the numbers depending on the line status. Further, the above change of the ratio is effective even if it is semi-fixed, but it is more preferable if it can be changed dynamically. However, it is difficult for existing systems to meet such demands.

Against the background of the above circumstances, the present invention is an economical IS system with minimal changes to existing networks.
It is an object of the present invention to provide a switching system capable of accommodating DN subscribers, especially subscribers requiring high-speed circuit switching, in a network.

[Means for solving problems]

A digital switch accommodating a high-speed circuit switching terminal of the present invention includes a time-division switching switch for general circuit switching calls for exchanging a general circuit switching call using a band of 64 Kbps or less, and a high speed circuit switching for using a band of more than 64 Kbps. A multiplexer for concentrating and multiplexing calls and a subscriber line of the ISDN primary rate access interface are terminated, the B channel and the D channel constituting the primary rate access interface are separated, and the separated D channel line A process for controlling a call is performed based on signal data, and a general circuit-switched call and a high-speed circuit-switched call communicated via a B channel are separated, and the general circuit-switched call is a time division for the general circuit-switched call. Means for connecting to the switching switch, and high-speed circuit-switched calls to the multiplexer, respectively. A time slot that accommodates a digital trunk line connected to an upper-tier switching center and is connected to a plurality of time-division switching switches for general circuit switching and the multiplexer, and configures the same physical line in the digital trunk line is predetermined. It is characterized by comprising means for inserting or separating a general circuit-switched call and a high-speed circuit-switched call corresponding to the time-slot position for the general circuit-switched time and the time slot position for a high-speed circuit-switched call and digitally transmitting them. .

〔Example〕

Referring to FIG. 1, the digital switching network to which the present invention is applied includes subscriber exchanges (LS) 10 and 30, and a transit exchange (TS) 20. In the following description, the subscriber terminals accommodated in the LS 10, TS 20 and LS 10 will be described as an example. In the digital subscriber terminal, the data terminal (DT) 51 and the telephone terminal (TT) 52 are accommodated in the network terminal (NT) 41, and the video terminal (VT) 53 and TT 54 are accommodated in the NT 42. The combination of the terminals is an example,
It is not limited to this combination. NT41 and 42 control the terminal accommodation form in the home, and LS1
NT41 and NT42 which perform layer 1 (physical layer) processing such as synchronization with 0 are digital subscriber lines (D
A) It is accommodated in the subscriber interface module (LM) 11 of the LS 10 via 71 and 72. LM1
Reference numeral 1 is connected to a general circuit switching time division switch (TDSW) 12 and a system multiplexer (SPMX) 13, respectively.

DT51, TT52 and 54, and VT53 to N
The call generated via T41 and T42 is separated into a high-speed circuit-switched call communicated via a plurality of B-channels in the LM 11 as well as a general circuit-switched call via the B-channel. Then, the general circuit switched call is connected to the TDSW 12, and the high speed circuit switched call is connected to the SPMX13.

A high-speed circuit-switched call is a call that is mainly connected by a high-speed terminal using a band of 64 Kbps or higher and is used for teleconference, image transmission, and the like. Digital relay line TCT
61 and 62 are general digital lines, for example 2.048M
bps (primary group), 8.448Mbps (secondary group), etc. (1.54 in North America)
It has a bit rate of 4 Mbps (primary group), 6.312 Mbps (secondary group), etc. The TCT61 uses the digital cross connect modules DXM14 and 21 to connect the LS10 and the T
It is housed in both exchanges of S20.

The DXMs 14, 21 and 24 are the line interface devices of the respective exchanges, and in the LS10 the TD
It is connected to SW12 and SPMX13 respectively, and S
It has a function of inserting and separating the high-speed circuit-switched call concentrated and multiplexed in the PMX 13 into the pre-designated channel of the TCT 61 together with the general circuit-switched call communicated through the TDSW 12. The above channel designation can designate any channel on the digital line. However, once designated, the designated channel is semi-fixedly used until changed.

The ratio of the channels used for the general circuit-switched call and the high-speed circuit-switched call is L depending on the respective traffic at that time.
It is changed by the negotiation between S10 and TS20.

In the upper station, that is, TS20, the general circuit-switched call and the high-speed circuit-switched call are separated by the DXMs 21 and 24 according to the designated channel of the digital circuit, and the general circuit-switched call is a time-division switch (TDSW) for general circuit switching.
At 22, the high-speed circuit-switched call is exchanged at the high-speed circuit-switched time division switch (HTDSW) 23.

Referring now to FIG. 2, the subscriber exchange (LS) 10 shown in FIG. 1 according to one embodiment of the present invention comprises a plurality of subscriber interface modules (LM) 110-11n. Each LM has a digital subscriber circuit (DLC) 211 and 212.

DLCs 211 and 212 accommodate subscriber lines 71 and 72, respectively, in the ISDN subscriber interface, the interface referred to as the U interface.
The DLCs 211 and 212 have a terminating function for layer 1 (physical layer) and layer 2 (data link layer). That is, the DLCs 211 and 212 perform electrical termination of the U interface, termination of layer 1 such as synchronization, and termination of layer 2 of LAP-D.

Referring to FIG. 3, the DLCs 211 and 212 include a line terminator (LT) 311 that terminates the layer 1 of the U interface, a D channel handler (DCH) 312 and 23 that terminates the layer 2 of the LAP-D.
A function to separate and insert a B channel communication path and a D channel from the format of the ISDN primary rate access interface of B + D, and to the concentrator switch (DLSW) 213 when the B channel is a general circuit switched call,
When the B channel is a high-speed circuit switching call, it comprises a dropper inserter (DI) 313 having a function of branching to a multiplexer (LMPMX) 215.

Next, description will be given with reference to FIG. 2 and FIG. Depending on the control of the DI 313, that is, whether the B channel is used for a general circuit switched call or a high speed circuit switched call, the B channel is set to the DLSW 213 respectively.
Is controlled by the module control circuit (LMC) 214. Specifically, the subscriber terminal transmits a calling signal via the D channel to the DLC 211 or 212 in which the subscriber terminal is accommodated. Based on this information, the LMC 214 controls the switching of whether the B channel is connected to the DLSW 213 or the LMPMX 215, respectively.

Of the outputs of the DLCs 211 and 212, the B channel of the general circuit switched call is connected to the DLSW 213.

The DLSW 213 concentrates and multiplexes the B channels from the DLCs 211 and 212 and connects them to the TDSW 12.

The TDSW 12 further multiplexes general circuit-switched calls concentrated by a plurality of LMs 110 to 11n to the multiplicity of the main highway, and connects the communication path to an appropriate destination subscriber interface module or trunk module by a switch network as necessary. .

The DCHs of the DLCs 211 and 212 perform layer 2 termination such as flag synchronization with the connected subscriber terminals, removal of consecutive 0's of a preset number or more, error control by retransmission, and the like. LMC2
Hand over to 14.

The LMC 214 uses the D channel data from the DLCs 211 and 212 to identify a service access point for identifying a layer 3 and layer 2 service access point.
Looking at I, the line signal data of SAPI = 0 is processed, and necessary call processing is performed. Accordingly, DLSW2
Necessary control is performed inside the system, such as communication of control information 217 between the control information 216 of 13 and the switch control unit (CTL) 250 that is the control unit of the TDSW 12. Conversely, the high speed line call received from the SMPX 13 is distributed to the corresponding LM.

The LMPMX 215 in the LM multiplexes the high-speed circuit switched call in the module and sends it to the SMPX 13.

The SPMX13 is installed in units of a plurality of subscriber interface modules (LM) 110 to 11n. On the uplink side (hereinafter, the direction from LS to TS is the uplink, and vice versa is the downlink) each subscriber interface module. The high-speed circuit switching call received from the LM is further multiplexed and sent to the digital cross connect module (DXM) 14. Also, on the downlink side, speech path data is sent to the subscriber interface module LM connected corresponding to the time slot. The DXM 14 is a general circuit-switched call that is installed corresponding to the circuit to multiplex the general circuit-switched call from the TDSW 12 to the general circuit-switched call channel and the high-speed circuit-switched call from the SMPX 13 to the high-speed circuit-switched call channel. High-speed circuit-switched call multiplexers (CPMX) 221 and 231, digital transmission interfaces (DTI) 222 and 231 that are line interfaces, and a digital cross-connect control circuit (DXCC) that controls a combination of a plurality of CPMXs 221 and 231 and DTIs 222 and 232. 240 and.

Further, the details of the DXM will be described with reference to FIG.
The CPMX 221 includes a selector circuit (SEL) 411 that can select a signal path from the TDSW 12 and a signal path from the SPMX 13 on a per uplink side in time slot units, and a demultibrex circuit (DEC) 41 on the downlink side.
Equipped with 3. In the DEC 413, the general circuit-switched call separates a predetermined time slot, inserts an idle channel pattern in the remaining time slot, and sends it to the TDSW 12. The high-speed circuit-switched call is sent to the SPMX 13 (see FIG. 2) except for the general circuit-switched call.

The CPMX 221 is a variable multiplexer, which is controlled by the insertion / separation time slot control memory IDCM 412 corresponding to the time slot. DX to IDCM412
DXCC240 which is the control circuit which controls the whole M14
The memory data is written to and read from.
The contents of the IDCM 412 are the maintenance control device (M
The bandwidth used by the general circuit switching call and the high speed circuit switching call can be changed by being rewritten via the DXCC 240 under the control of the NC) 260.

Also, a digital transmission interface (DTI) 222
Has an interface function with TCT which is a digital transmission path, that is, a bit synchronization, a frame synchronization, a frame aligner function, and various functions of fault monitoring on the digital transmission path. Transmission control circuit (SND) 431 shown in the figure
Has a function of inserting a frame pattern, suppressing 0 series, and sending an alarm signal to the game. It also converts to a unipolar / bipolar signal.

On the downlink side, in the digital transmission line from the relay stage, the bipolar signal on the digital transmission line is converted in the bipolar / unipolar conversion circuit (BU) 433 into the unipolar signal in the exchange and sent to the reception control circuit (RCV) 434. The RCV 434 performs bit synchronization, frame synchronization, and frame alignment processing for aligning the frame phase of the digital transmission line with the phase of the exchange. Also R
CV434 has a fault monitoring function on the digital transmission line, and when a fault is found on the digital transmission line, DXCC24
Report to 0. The DXCC 240 receives the above report and notifies the MNC 260.

The MNC 260 is a device that performs monitoring for failure of each device in the exchange and control for maintenance. The MNC 260 transmits / receives data necessary for operating the system to / from the LMCs 214, 250 and the like in order to achieve the above purpose.

〔The invention's effect〕

As described above, the digital exchange accommodating the high-speed circuit switching terminal of the present invention commonly receives the services of circuit switching and high-speed circuit switching on the same subscriber line while minimizing the influence on the subscriber switching device. It is possible to minimize the impact on the network at the initial stage of ISDN introduction, and to economically introduce ISDN.

Further, the trunk line (Toll Connecting Trunk: TCT) connecting the subscriber exchange and the relay exchange can be shared by the circuit switched call and the high speed circuit switched call, whereby the efficient use of the trunk line can be realized.

There is an effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an ISDN network to which the present invention is applied, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 shows details of the digital line circuit shown in FIG. FIG. 4 is a block diagram and FIG. 4 is a block diagram showing details of the digital cross-connect module shown in FIG. 10 ... Subscriber switch (LS), 11 ... Subscriber interface module (LM), 12, 22 ... General line exchange time division switch (TDSW), 13 ... System multiplexer (SPMX), 14, 21, 24: Digital cross connect module, 23: High-speed line switching time division switch (HTDSW).

Claims (1)

[Claims] 1. A time-division switch for a general circuit-switched call for exchanging a general circuit-switched call using a band of 64 Kbps or less in a digital subscriber exchange; a high-speed circuit-switched call using a band of more than 64 Kbps is concentrated. Multiplexer for multiplexing; B channel and D terminating the subscriber line of the ISDN primary rate access interface and configuring the primary rate access interface
Channels are separated, processing for call control is performed based on the separated D-channel line signal data, and general circuit-switched calls and high-speed circuit-switched calls communicated via the B-channel are separated, A means for connecting the circuit switched call to the time division switching switch for the general circuit switched call and a high speed circuit switched call to the multiplexer respectively; a plurality of the general circuits accommodating a digital trunk circuit connected to the upper ladder switching center; It is connected to a time division exchange switch for exchange and the multiplexer, and corresponds to a time slot position for general circuit exchange and a time slot position for high-speed circuit exchange call which are predetermined in time slots constituting the same physical line in the digital trunk line. Means for inserting or separating a general circuit switched call and a high speed circuit switched call for digital transmission; Digital switching equipment to accommodate the high-speed circuit-switched terminal, wherein.