KR950000678B1 - Distributed packet switching arrangement - Google Patents

Abstract

No content.

Description

Integrated line / packet switching system

1 through 3 are block diagrams of exemplary embodiments of an integrated packet switching and circuit switching system comprising a distributed packet switching arrangement illustrating the principles of the invention when arranged in accordance with FIG.

4 is a more detailed diagram of the digital line units included in the system of FIGS.

5 to 11 are more detailed diagrams of the packet switching unit and processor interface included in the system of FIGS. 1 to 3 when arranged in accordance with FIG.

FIG. 14 is a time sequence diagram illustrating the flow of control messages between the user terminal and switching system of FIGS. 1 through 3 to form and subsequently disconnect circuit switched calls. FIG.

15 and 16 are functional diagrams for the communication sequence employed in the setup and removal of intra-module packet switched calls in the systems of FIGS.

FIG. 17 illustrates entries in the routing table of two protocol coordinators involved in an example of packet switched switching in a module.

Figure 18 illustrates entries in the routing table of the four protocol coordinators involved in the intermodule packet switched call example.

FIG. 19 is a diagram illustrating a directly coupled mesh topology used to interconnect four switching modules of the systems of FIGS. 1-3 for inter-module packet traffic. FIG.

FIG. 20 is a diagram illustrating the shaping phase used to interconnect four switching modules for intermodule packet traffic in a first alternative embodiment of the invention.

FIG. 21 is a diagram showing additions and modifications to the system of FIGS.

FIG. 22 is a block diagram of a time division line switching system before four additional switching modules are incorporated as shown in FIGS. 1-3 to provide packet switching capability.

FIG. 23 is a more detailed diagram of the time slot exchange unit and associated control unit used in the system of FIG. 22. FIG.

24 is a diagram of an interface unit included in each time slot exchange unit used for communication with a time multiplexed switch of the system of FIG.

25 is a diagram of an interface unit of a time multiplexed switch used for communication with a time slot exchange unit of the system of FIG.

FIG. 26 is a diagram for the data word format used in the FIG. 22 system.

27 is a functional diagram for the communication sequence required for call setup in the FIG. 22 system.

28 is a diagram of an E-bit control sequence of the system of FIG. 22. FIG.

FIG. 29 is a diagram for an E-bit check circuit used in the system of FIG. 22. FIG.

* Explanation of symbols for main parts of the drawings

10: time multiplex switch

11,12,1011,4011: Time slot exchange unit

17,18,1017,4017: Control unit 19,20,21,22: Line unit

29: control memory 30: central controller

31: control distribution unit 69: interface unit

78,79: link interface 190: outgoing uniform

191: incoming unit

501,527,1000,2000,3000,4000: switching module

1101,1102,4101,4102: Digital Line Unit

1300: Processor Interface

1400,4400: Packet Switching Unit

1500: Control Fanout Unit

1600-0 to 1600-5: Data Fanout Unit

1700-0 to 1700-95,1701-0 to 1701-95,4700-0 to 4700-95

1800,4800: Packet Interconnector

1900-0 to 1900-5: Packet fanout unit.

[Technical Field]

The present invention relates to a switching system comprising a plurality of switching modules each associated with a plurality of user terminals, wherein the switching module is connected to the plurality of related via a access line to provide a circuit switched communication channel between the user terminals. A time slot switching unit capable of connecting a user terminal, and a time multiplex switch for interconnecting the time slot switching unit of the switching module for circuit switched communication between modules.

[Background of invention]

The widespread use of personal computers and other data processing devices in homes and offices requires the widespread use of voice and data transmission and switching capabilities. This has led to the development of an ISDN, a switched communication network that provides end-to-end digital connectivity between network users, where voice and data services are provided via the same transmission and switching facility. In other words, due to the different nature of the communication between voice and data, voice is typically continuous in one direction for a relatively long time and is immune to noise, but sensitive to delay changes so that the data is sensitive to errors, Because of their immunity, two fundamentally different switching techniques have traditionally been applied. Circuit switching, where switch connections between users are made during a call duration, is the basis of today's switched voice communications circuitry. On the other hand, packet switching, in which data packets from many calls share a single high speed line and is switched based on the number of logical channels contained in that packet, has been realized in various public data circuits.

Currently the most commonly used method of serving customers who need both voice data is to use separate circuits and separate access lines for both types of traffic. Since both voice and data access lines are typically only used for a fraction of the time, the duplication of equipment involved in this method is wasteful and expensive compared to devices that can be shared by a facility. Some currently available equipment multiplexes voice and data over the same access line. However, even when access lines are shared, voice and data typically transmitted in very different formats must each be switched to their appropriate destination. One way to provide such switching is to use a completely separate packet switch and circuit switch. However, this method is redundantly unnecessary. From the line circuit internally, two types of information are serviced by separate equipment. The main reason for using this approach is the technical difficulty in coordinating these two fundamentally different forms (and formats) in an efficient and comprehensive form.

Another solution to the problem is to include a centralized packet switching entity in the switching system and route all packet traffic from the system user to the centralized entity. In other cases, however, if line switching material available for voice calling is used to convey such packet call volume, the voice call capacity of the switching system is reduced by an amount depending on the level of the packet call amount. Furthermore, the initial cost and complexity of integrating such concentrated packet switching entities into the construction of circuit switching systems is significant given the gradual increase in the number of system users requiring packet switching services.

Problems recognized in the art include difficulties in providing packet switching services to users of ISDN switching systems, unnecessary duplication of equipment, undesirable effects of packet call volume on circuit switched call capacity of the system, and the number of users. This is an increasing effect on the packet switching capacity of the system with an increase in.

Overview of the Invention

In the switching system for solving this problem according to the invention each switching module is adapted to provide said packet multiplexed communication channels between said associated user terminals and between said associated user terminal and time multiplexed switching. And further comprising a packet switching unit capable of connecting to the located position, wherein the time multiplexed switch interconnects the packet switching units for intra-module packet switched communication.

The switching system according to the invention comprises a plurality of switch modules, each associated with a corresponding group of user terminals. The switching module is interconnected to an intermodule connection unit, a time multiplex switch. Each switching module comprises a circuit switching unit, for example a time slot exchange unit and a packet switching unit. The circuit switching unit provides a similar channel to the circuit switched communication channel for the amount of call in the module and the intermodule connection unit for the circuit switched call amount between the modules. Similarly, the packet switching unit provides a packet switched communication channel for the packet switched call volume in the module, and provides a similar channel to the intermodule connection unit for the packet switched call volume between the modules.

In accordance with an exemplary embodiment, each switching module further comprises a bidirectional data bus coupling the packet switching unit to a time slot exchange unit. The time slot exchange unit provides a scheduled communication channel between a bidirectional data bus and a time multiplexed switch for use in carrying packet traffic between modules.

In an exemplary embodiment, each packet switching unit includes a plurality of packet switching node protocol coordinators that accumulate received data bits into the packet and subsequently transmit the packet to the destination. One of the nodes may be connected to a time multiplexed interface switch, and some of the nodes may be connected to a user terminal of the switching module. The packet switching unit further comprises a packet interconnector interconnecting the nodes to provide a packet switched communication channel between the user terminal of the switching module and between the user terminal of the switching module and the intended node. The time multiplexed interface switch interconnects predetermined nodes of the switching module to provide a packet switched communication channel between user terminals of different switching modules.

In an exemplary embodiment, the packet switching node sends a request signal to the packet interconnector. These packet interconnects each generate a selection signal defining one of the nodes and respond to a request signal from a given node and a generated selection signal defining the given node by transmitting a clear signal to the given node. A given node responds to a clear signal from a packet interconnect by sending a packet. The ordering arrangement allows each node to send information to the packet interconnector in order.

According to an exemplary embodiment, the predetermined node of each switching module is connected to each predetermined node of the other switching module in a directly connected mesh topology. In a first alternative embodiment, the predetermined node of only one of the switching modules is connected to the predetermined node of the other switching module in the shaping phase.

Packet switching network is included in a second alternative embodiment of the present invention. Each packet switching node that may connect to a user terminal may connect to a packet switching network. Furthermore, the packet switching node is connected to the control unit used to control the operation of the time slot exchange unit. The packet interconnector provides signals and channels between each user terminal and the control unit of the switching module. A node capable of connecting to the user terminal transmits a signaling packet received from the user terminal to the control unit of the switching module and transmits a data packet received from the user terminal to the packet switching network.

Good Example

1 through 3 show block diagrams of exemplary time division switching systems illustrating the principles of the invention when arranged in accordance with FIG. A time multiplexed interface switch 10 that provides a circuit switched communication channel between the 27 switching modules 501-527 of the system and a plurality of conventional subscriber sets 23-26. Each switching module includes a control unit that controls the switching module operation including the formation of a circuit switched channel by the time slot switching unit. For example, the switching module 501 includes a control unit 17 for controlling the operation of the time slot exchange unit 11, and the switching module 527 controls the operation of the time slot exchange unit 12. 18). The switching module control unit 17 (18) and the central controller 30 controlling the operation of the time multiplexed switch 10 are controlled by the time multiplexed switch 10 and control distribution in the manner described in detail herein. They communicate with each other via an interprocessor communication mechanism using a predetermined control channel of the unit 31. For example, the control unit 17 first detects the off-hook state of the subscriber set 23 and then one of the other subscriber sets served by the switching module 501, for example the subscriber set 24. The control unit 17 and the central controller 30 exchange control messages when detecting a series of digits that define the number of digits that define the number of digits, and then the control unit 17 between the subscriber set 23 and the subscriber set 24. The time slot exchange unit 11 forms a bidirectional circuit switched communication channel between the subscriber set 23 and the subscriber set 24 for the duration of the voice call.

In addition, when the subscriber set 23 calls the subscriber set, eg, set 26, served by the switching module 527, the control units 17, 18 and the central controller 30 exchange control messages. To form a call. The central controller 30 writes commands via the track 49 to the central memory 29 which defines the channels of time multiplexed interface switches 10 available between the time slot exchange units 11 and 12. do. Through the control unit 17, the time slot exchange unit 11 forms a circuit switched communication channel between the subscriber set 23 and the available time multiplexed switch 10 channel. Likewise, through the control unit 18, the time slot exchange unit 12 forms a circuit switched communication channel between the subscriber set 26 and the available time multiplexed switch 10 channel. The switching system comprises a time slot exchange unit 11 indicating a first time step, a time multiplexed switch 10 indicating a space end and a second for a call from subscriber set 23 to subscriber set 26. It is composed of a time-space-time type with a time slot exchange unit 12 indicating a time stage.

In accordance with an exemplary embodiment of the present invention, the four switching modules 1000, 2000, 3000, and 4000 are for example customer terminal, vendor datebases, telephone operator location terminals, or packet access. Included in the system is to provide line switching and packet switching services to a number of user terminals 1001, 1002, 4001 and 4002 that indicate ports. 2 and 3 only the switching modules 1000 and 4000 are shown in detail. Each user terminal 1001 transmits information to and receives information from, for example, the associated switching module 1000 in a 64 Kbps channel called a B channel and a 16 Kbps channel called a D channel. In this embodiment, one B-channel is used to carry 8-bit samples at a digital rate of 8000 samples per second, and the other B-channel is used to carry data at the same rate of 64 kilobits per second (but Each B channel can be used for the traffic of either voice or data. Each B channel is separately switched by the above system to, for example, another user terminal 1002, 4001, 4002, or, for example, to subscriber sets 23 to 26. The D channel is used to carry signals and packets for message communication between the user terminal and the system, and to carry data packets between the user terminals. The D channel is packet switched to another user terminal by the system, or packet switched to the control unit 1017 which controls both the formation of the circuit switched call and the formation of the packet switched call in the switching module 1000. Message communication between the user terminal and the control unit 1017 may be configured in a functional or stimulating format. Functional signaling involves some intelligent processing in its generation or analysis, while stimulus signaling occurs as a result of a single time at a user terminal, such as a key press, or Contains basic commands from the switching system to be performed by the user terminal.

In this exemplary embodiment, information is conveyed, for example, between the user terminal 1001 and the switching module 1000 via a four-wire user access line 1003 using a pair of conductors for each transmission direction. . User line 1003 includes 144 Kbps for the two 64 Kbps B channels and one 16 Kbps D channel, and also uses 48 Kbps used for multiple functions including frame formation, DC balancing, control and maintenance. It transmits a signal bit flow at a speed of 192 Kbps. User line 1003 is referred to as the T interface by the International Telegraph and Telephone Advisory Committee (CCITT). Using the T interface in this system is merely exemplary. The present invention is equally applicable to systems using other access methods.

In the switching module 1000, for example, user lines 1003 and 1004 are terminated by two digital line units 1101 and 1102. Information is carried between the respective digital line units 1101 and 1102 and the time slot exchange unit 1011 via a number of 32 channel bidirectional time multiplexed data buses 1201. Information is also carried between the respective digital line units 1101 and 1102 and the packet switching unit 1400 via a number of 32 channel bidirectional time multiplexed data buses 1202. The data bus 1201 is primarily used to convey the B-channel information circuit-switched by the time slot exchange unit 1011 to a user terminal served by the switching module 1000 or the time multiplex switch 10. do. However, the data bus 1201 also carries D channel information carried to the packet switching unit 1400 via any of the time slot exchange unit 1011 channels and the 32 channel bidirectional data bus 1205 predetermined at system initialization. Is used. Each channel or time slot on data bus 1201 may include eight B-channel bits from one user terminal or two D-channel bits from each of four different user terminals. The data bus 1202 is used to carry only D channel information. Each channel or time slot on data buses 1202 and 1205 includes two D-channel bits from each of four different user terminals.

In this exemplary embodiment, the packet switching unit 1400 includes 96 protocol coordinators 1700-0 through 1700-95, protocol coordinators 1700-0 through 1700-95, and a processor interface 1300. And a packet interconnector 1800 for interconnecting them. Each user terminal, e.g., 1001, is associated with one of the protocol coordinators 1700-0 to 1700-95, and in particular 32 high level data link control (HDLC) circuits included in the relevant protocol coordinator. One, for example 1406-0 (FIG. 8). In this embodiment, a communication link is formed between the HDLC circuit of the protocol coordinator and the corresponding HDLC circuit (not shown) at the user terminal at system initialization. This link is used to carry packets in HDLC frames according to known HDLC protocols. The connection between a given protocol coordinator and its associated D channel on data buses 1202, 1205 is completed by one of six data fan out units, for example 1600-0 (FIG. 7).

Packets carried on the D-channel communication link between the user terminal and the associated protocol coordinator are of variable length. Each user terminal, for example 1001, transmits and receives packets on one or more logical communication channels. In this embodiment, logical channel LCN1 is used to carry signaling packets to set up both circuit switched and packet switched calls to and from user terminal 1001 and logical channel LCN2 is used. It is used to carry data packets during packet switched calls to and from user terminal 1001. The logical channel number of each packet is defined by the header portion of that packet. Each packet received by the protocol coordinator (user packet switching node) from the user terminal is stored in a random access memory (RAM), for example RAM 1470 (FIG. 8), at its protocol coordinator. If the received packet is a signaling packet, that is, it is received on logical channel LCN1, this packet is transmitted to processor interface 1300 via packet interconnect 1800. If the received packet is a data packet, that is, it was received on logical channel LCN2, and a packet switched call was previously formed, then the received packet was sent via packet interconnect 1800 for subsequent transmission to the destination user terminal. Destination is sent to the protocol coordinator associated with the user terminal. In other words, if a packet switched call is made between two user terminals associated with the same protocol coordinator, the data packet need not be transmitted via the packet interconnector 1800. Instead, the protocol coordinator only sends data pickets on the appropriate channel to the destination user terminal.

When a given protocol coordinator, e.g., 1700-0, has received a complete packet from a user terminal and has determined the destination of that packet, i.e., one of the other protocol coordinators or processor interface 1300, this coordinator Sends a Logical 0 Transmit Request (RTS) signal on one of the six conductor buses 1701-0, referred to as a request signal, to the packet interconnector 1800. Similarly, when the processor interface 1300 has a packet ready to transmit to one of the protocol coordinators, the processor interface transmits a logical 0 RTS signal on one of the six conductor buses 1301. The packet interconnector 1800 allows each protocol coordinator and processor interface 1300 to transmit in a predetermined order. Since processor interface 1300 transmits signals and packets to all user terminals served by switching module 1000, processor interface 1300 for each enabling of individual protocol coordinators in the order by packet interconnector 1800. Enable 16 times. When the packet interconnector 1800 order reaches the protocol coordinator 1700-0, the packet interconnector 1800 clears the logical 0 transmission on the second conductor of the bus 1701-0, referred to herein as a clear signal. ) Responds to the RTS signal on bus 1701-0 by sending a signal to protocol coordinator 1702-0. The protocol coordinator 1700-0 responds to the CTS signal at high speed, for example, at 10 Mbps by sending the stored packet to its destination via the packet interconnector 1800. All protocol coordinators and processor interface 1300 can receive packets, but only one receiver, as defined by the packet coordinator in this embodiment, actually stores the packet by subsequent transmission. Only after the complete packet has been sent by the protocol coordinator 1702-0 the packet interconnector 1800 sequence begins again. Packet reception by the destination protocol coordinator or by the processor interface 1300 is confirmed by sending an acknowledgment packet back to the protocol coordinator 1700-0.

The other three switching modules installed for packet switching are almost identical to the switching module 1000. In the switching module 4000, the elements are numbered exactly 3000 larger than the corresponding elements in the switching module 1000. The protocol coordinators 1700-0 through 1700-95 and the processor interface 1300 in the switching module 1000 and their corresponding elements in the switching module 4000 accumulate the received data bits into packets. The packets are referred to herein as packet switching because they are sent to their destination. In this embodiment, the protocol coordinators 1700-0 and 1700-2 through 1700-95 are connected to the D channel from the user terminal, and are referred to as user packet switching nodes. Since processor interface 1300 is coupled to carry control information to and from control unit 1017, processor interface 1300 is referred to as a control packet switching node. In the switching module 1000, one protocol coordinator in each switching module, for example, the protocol coordinator 1700-1 and the protocol coordinator 4700-1 in the switching module 4000, is used for packet call data between modules. It is used to switch packets and is called intermediate packet switching node.

In this embodiment, the four channels on the data bus 1205 are four channels of the input / output port pair P55 of the time multiplex switch 10 by the time slot exchange unit 1011 at system initialization, for example. Are connected to channels 109 through 112. Similarly, four channels (FIG. 3) on the data bus 4205 are connected to the channels 109 to 112 of the input / output port pair P61 by the time slot exchange unit 4011. The control memory 29 defines to form a bidirectional communication line between the input / output port pairs P55 and P61 during the channel 109 to 112 cycles of each time multiplexed switch 10. By using these predefined connections, the protocol coordinators 1700-1 and 4700-1 can transmit up to four packets at a time at 256Kbps or 64Kbps at once using all four channels. The transmission can be made using one of four channels or the association of several different channels. Connections must be made through time slot exchange units 1011, 4011 to be received by protocol coordinator 4700-1 in the same order in which packets are transmitted at a rate of n × 64 Kbps. Assume that user terminal 1001 is associated with protocol coordinator 1700-0 and user terminal 4001 is associated with protocol coordinator 4700-1. Once a packet switched call has been established between user terminal 1001 and 4001, the data packet is transmitted and stored at 16 Kbps from user terminal 1001 to protocol coordinator 17000-0.

When enabled by the packet interconnector 1800, the protocol coordinator 1700-0 transmits a data packet to the protocol coordinator 1700-1 at a rate of 10 Mbps. The protocol coordinator 1702-0 may be configured via a predetermined channel of the bus 1205, a time slot exchange unit 1011, a time multiplex switch 10, a time slot exchange unit 4011, and the bus 4205. At 4700-1, for example, a data packet is transmitted at a rate of 256 Kbps. When enabled by the packet interconnector 4800, the protocol coordinator 4700-1 transmits the data packet to the protocol coordinator 4700-0 at a rate of 10 Mbps.

Finally, protocol coordinator 4700-0 sends data packets to user terminal 4001 at a rate of 16 Kbps. Of course, appropriate registration must be made in the routing tables in each of the protocol coordinators 1700-0, 1700-1, 4700-1, and 4700-0 as part of the processor that forms these packet switched calls. . Processors requiring exchange of control communications between control units 1017, 4017 and central controller 30 are described in detail herein.

[details]

22 is a block diagram of a time division line switching system. The exemplary integrated packet switching and line switching system of FIGS. 1 through 3 includes the system of FIG. 22 to which four additional switching modules 1000, 2000, 3000, and 4000 are added. The description below is arranged in two parts. First, the system of FIG. 22 is described. Based on the description, an exemplary embodiment of the invention shown in FIGS. 1 to 3 is shown.

[Figure 22 System]

The time division switching system of FIG. 22 is used to interconnect subscriber sets, such as subscriber sets 23 to 26, and employs a time-shared space division switch with 64 input ports and 64 output ports. Including time multiplexed switching 10. Also included are a 27 hour slot exchange unit, in which representative time slot exchange units 11, 12 are shown in particular. Each time slot exchange unit 11, 12 includes a bidirectional time slot exchanger and is further connected to two input ports and two output ports of the time multiplexed switch 10. In the system of FIG. 22, the time slot exchange unit 11 is connected to the two hour multiplexed switch input port via the time multiplexed lines 13, 14, and the time multiplexed line 15, It is connected to the 2 output ports via (16).

In the following description, the input / output ports of the time multiplexed switch 10 are referred to as input / output port pairs. This term is used because the source for a data word destined for an input port on a given input / output port is also the destination for data words from that pair of output ports. As shown in FIG. 22, the input / output port pair P1 is associated with the time multiplexed lines 13 and 15. Each time multiplexed line 13-16 carries digital information in 125 ms frames that each include a 256 hour split channel. Thus, each time slot exchange unit receives up to 512 channels of digital information for each 125 ms frame.

Each time slot exchange unit is uniquely associated with each control unit, that is, the control unit 17 is associated with the time slot exchange unit 11 and the control unit 18 is associated with the time slot exchange unit 12. In addition, each time slot exchange unit is connected with a plurality of line units, and line units 19 to 22 are shown in FIG. 22 via separate time multiplexed lines. The line units 19 and 20 are connected to the time slot exchange unit 11, and the line units 21 and 22 are connected to the time slot exchange unit 12. Each line unit is connected to a plurality of subscriber sets, in which subscriber sets 23 to 26 are shown. The exact number of line units associated with each time slot exchange unit and the exact number of subscriber sets associated with each line unit are determined by the number of subscribers to be served and the calling speed of those subscribers. Each line unit is terminated by a known analog loop from a plurality of subscriber sets, for example (23) to (26), converts the call information including the analog voice signal into a digital data word, and converts this digital data. The word is sent to the associated time slot exchange unit. In addition, each line unit detects a service request from a set of subscribers and generates some signals and information for that set of subscribers. The particular set of subscribers for which voice samples are taken and encoded, and the particular time multiplexed channel used to transmit the resulting code between the line unit and its associated time slot exchange unit, are controlled by the control unit of the associated time slot exchange unit. Is determined.

The relationship between the subscriber set, the line unit and the time slot exchange unit is actually the same for each of these groups of interconnected nits. Thus, while the following description relates directly to subscriber set 23, line unit 19 and exchange unit 11, this description shows the relationship to all of these other groups of units. The line unit 19 scans the lines connected to each set of subscribers to detect service requests. When such a request is detected, the line unit 19 sends a message to the control unit 17 indicating the request and the identity of the requesting subscriber set. This message is transmitted to the control unit 17 via the communication line 27. The control unit 17 performs the necessary translations on the basis of the required service, the identity of the requesting subscriber set and the available equipment, and the multiple time separation channels between the line unit 19 and the time slot exchange unit 11. A message is sent to the line unit 19 via the communication line 27 which defines which of the subscriber sets 23 will be used to transmit information from the subscriber set 23 to the time slot exchange unit 11. Based on this message, the line unit 19 encodes the analog information from the subscriber set 23 into a digital data word and transmits the resulting data word to the assigned channel. The line unit 19 transmits an indication of the DC state of the subscriber loop associated with the subscriber set 23, i. E. Open circuit, short circuit, to the assigned channel.

After the time separation channel between the line unit 19 and the time slot exchange unit 11 is assigned to a given subscriber set, the control unit 17 samples the signaling information from the subscriber set by sampling the information transmitted on the assigned channel. This sampling operation is performed via the communication line 28. The control unit 17 controls the time slot exchange function of the time slot exchange unit 11 so that signals and information from the subscriber's channel and other control units, for example (18) and from the central control unit (30), are controlled. Respond to the control message. As already described, each multiplex line between the time slot switching unit and the time multiplexed switching 10 has 256 channels in each 125 ms frame. These channels are assigned to 1 to 256 destinations in the order in which they occurred. The order of these channels is cycled so that a given channel is available every 125 ms. The time slot exchange function accepts data words received from the line unit, and under the control of the control units 17, 18, the channels on the time multiplexed line between the time slot exchange unit and the time multiplexed switch 10 Posted in

The time multiplexed switch 10 operates in a circular frame of time slots where each 125 ms frame includes 256 time slots. During each time slot, the time multiplexed switch 10 can connect a data word received at any of the 64 input ports to any of the 64 output ports in accordance with the time slot control information stored in the control memory 29. have. The configuration pattern of the connection via the time multiplex switch 10 repeats itself every 256 time slots, with each time slot being assigned to the destination in the order of 1 to 256. Thus, the information in channel 1 on the time multiplexed line 13 during the first time slot TS1 is switched to the output port P64 by the time multiplexed switch 10, while during the next time slot TS2. The next channel 2 on the time multiplexed line 13 will be switched to output port P55. The time slot control information is recorded in the control memory 29 by the central controller 30 which generates this control information from control messages obtained from various control units, for example 17 and 18.

The central controller 30 and the control units 17, 18 control the time multiplexed line between the time slot exchange unit and the time multiplexed switch 10, for example the control channels of (13) to (16). It exchanges control messages using a selected channel called. Each control message includes a number of control words, and each control channel can transmit one control word / frame for 256 time separation channels. The same channel of two time multiplexed lines associated with a given input / output port pair is predefined as a control channel. Also, a given channel is used as a control channel only for a pair of time multiplexed lines. For example, if channel 1 is used as a control channel on time multiplexed line 13 and associated time multiplexed line 15, then another time multiplexed line does not use channel 1 as control channel. During each time slot having a destination of the same number as the control channel, the time multiplexed switch 10 connects the data word occupying that control channel to the output port P64 and connects the input port P64 to the control. Connect to the output port associated with the channel.

Next, when channel 1 is the control channel for time multiplexed lines 13 and 15, and channel 2 is the control channel for time multiplexed lines 14 and 16, One embodiment of the operation of the system of FIG. During time slot TS1, information from memory 29 is connected, among other connections, a control word in channel 1 of time multiplexed line 13 to an output port P64, and at input port P64 a channel. It defines that the control word in (1) is connected to the time multiplexed line 15. Similarly, during time slot TS2, the information from control memory 29 is such that the control word in channel 2 of time multiplexed line 14 is connected to output port P64, and at input port P64 the channel ( It defines that the control word in 2) is connected to the time multiplexed line 16. When operating in this manner the output port P64 receives all control words in the channel from the time multiplexed switch 10 with the same number of destinations that all control words were sent to the time multiplexed switch. Furthermore, each control channel is connected to receive a control word from input port P64 during a time slot having a destination of the same number as their associated control channel. The control words switched to the output port P64 are transmitted to the control distribution unit 31 which temporarily stores them in positions associated with the control words. The stored information source is identified by the association between the storage position in the control distribution unit 31 and the control channel.

Each control message from the time slot exchange unit includes a start character, a destination part, a signaling information part and an end character. The destination portion uniquely defines the expected destination of the control message. The control distribution unit 31 interprets the destination portion of each control message to determine an appropriate destination for the control message, and time-multiplexes the message in a channel having a destination with the same number as the control channel associated with the destination unit. It retransmits to the input port P64 of the formula switching 10.

When operating as described above, the time slot exchange unit 11 transmits a control message to the time slot exchange unit 12 by transmitting a control word during its cyclic control channel, thereby identifying the destination for the time slot exchange unit 12. Form a control message having a portion. The control distribution unit 31 accumulates the control word, interprets the destination portion, and sends a message to the input port P64 during the channel having a destination with the same number as the control channel associated with the time slot exchange unit 12. Resend. The control message may be sent to the central controller 30 by defining the central controller 30 at the destination portion of the control message. When this operation occurs, the control distribution unit 31 transmits the message to the central controller 30 via the communication link 32 without circulating the time multiplexed switch 10. Similarly, the message may be sent from the central controller 30 to one of the time slot switching units by sending a control message having a destination portion defining a particular time slot switching unit to the control distribution unit 31. Such transmission may also be performed using communication link 32.

Each control unit, e. 57 (FIG. 23). The memory 57 stores information such as service classification, subscriber limits for gain or attenuation, telephone screening information, and information about changes in normal call processing procedures such as end of common hold. Most of the contents of a given memory 57 are not stored in memory locations associated with other control units or central controllers. However, it may be stored in bulk memory (not shown) for maintenance. For example, some information in memory 57, such as common hold end information, is primarily associated with a function performed by another control unit. This information is stored in association with the subscriber associated with that information to avoid the inefficiency of the centralized storage of this information and to avoid data duplication. The above configuration using the control channel received through the control distribution unit 31 is used to transmit this call related information to the other control unit and the central controller 30.

As already described, the control unit 17 controls many of the operations performed by each line unit. The main processing entity of the control unit 17 is the processor 66 (Fig. 23) which operates in response to the instructions stored in the memory 57. The control unit 17 receives a command from the processor 66 via the bus 59, and in response, communicates with the line unit, eg 19 and 20, via the communication line 27. Control interface circuitry 56; The control unit 17 also includes a signal processor 65 and a digital service unit 67. The signal processor 65 reduces the real-time load request of the processor 66 by receiving and analyzing the signaling portion (bits A through G in FIG. 26) of each data word received by the time slot exchange unit 11. The digital service unit 67 receives the data portion (Fig. 26) of each data word received by the time slot exchange unit 11 to detect the tone signal from the subscriber converted to the PCM signal. The digital service unit 67 is also used to transmit tones and signals in PCM format to the subscriber via the gate 51 and to the time multiplexed switch 10 via the gate 52. The operation of the control interface circuit 56, the signal processor 65 and the digital service unit 67 as well as the line unit 19 are known in the art. In the system of FIG. 22, the clock signal used in the line unit is passed through the control interface 56 and the communication line 27 by the clock recovery circuit 84 (FIG. 24) to the interface unit 69 (FIG. 23). Is transmitted in the figure).

Each line unit transmits a cyclic frame each containing 16 digital bits of 16 bits. This information is transmitted to the Miltiplex unit 60 (FIG. 23) in the time slot exchange unit 11. The multiplex unit 60 is reformatted and transmitted on an output time multiplexed line 62 having 512 channels for each 125 ms frame. Similarly, the demultiplex unit 61 receives 512 channels of 16 bits each on a time multiplexed line 63 in which channels are distributed in a predetermined configuration to eight line units such as the line unit 19. Further, the multiplex unit 60 converts the incoming channel of information from serial to parallel form, and the demultiplex unit 61 converts received information from parallel to serial form. Information transmitted on a given channel on time multiplexed line 62 is stored in receive time slot exchange 50 at a memory location uniquely associated with that given channel.

The specific memory location where a given data word is stored is defined by the time slot destination signal generated by time slot counter 54. Time slot counter 54 generates a cyclic series of 512 time slot destinations at a rate of one time slot destination per time slot. The particular time slot destination generated during the time slot period in which a given data word is received defines a memory location within the receive time slot exchange 50 storing that data word. Data words may also be read from receive time slot exchange 50 at a rate of one data word per time slot. The memory address of the data word to be read from the receive time slot exchange 50 for a given time slot is obtained by reading the control RAM 55. The control RAM 55 is read from the time slot counter 54 once per time slot at the address defined by the time slot destination, and the amount so read is the received time slot switch as a read address for that time slot. Is sent to 50. The data words read from the receive time slot exchange 50 are time multiplexed via the time multiplexed line 68, gate 8, time multiplexed line 68 'and interface unit 69. Is sent to (10).

The data words from the time multiplexed switch 10 are received by the time slot exchange unit 11 by the interface unit 69, the time multiplexed line 70 ', the gate 9 and the time multiplex. It is conveyed to the transmission time slot exchange 53 via the formula line 70. In the case of a call between subscribers served by a line unit connected to the time slot exchange unit 11, when the control RAM 55 operates the gates 8 and 9, the reception time slot on the time multiplexed line 68 The data words transmitted by the exchange 50 are carried to the transmission time slot exchange 53 via gates 8 and 9 and the time multiplexed line 70. The transmission time slot exchange 53 stores the incoming data word at the position defined by the address from the control RAM 55. The data word is read from the transmission time slot switch 53 at the address defined by the time slot counter 54.

The data words read in this way are transmitted to the time multiplexed line 63 for transmission to the line unit 19. Note that the control RAM 55 can be realized as a plurality of control memories, each associated with a particular circuit, such as, for example, the transmission time slot exchange 53. The specific structure of the control memory is not important in this description and may vary depending on timing and circuit requirements within the time slot exchange unit 11. The general principles of time slot exchange performed by receive time slot exchange 50, control RAM 55, time slot counter 54, and transmit time slot exchange 53 are known in the art and are further described herein. It is not described in detail.

The primary mode of control information in the system of FIG. 22 passes a time multiplexed switch 10 and a control distribution unit 31 from a source time slot exchange unit and sends a control message back to the destination time slot exchange unit. It includes. Control information for a call, used in a secondary mode of communication and thereby given, is transferred to a destination time slot via a time multiplexed switch 10 using a time slot allocated for that call from a source time slot exchange unit. Sent to the unit. The data word and E bit portions in the call time slot are used for secondary mode communication. However, some or all of the signaling bits serve the dual purpose of this secondary communication line continuity check and signal receipt confirmation. The control RAM 55 (Fig. 23) includes one E bit position in each of the 512 storage positions. During the call process, the processor 66 controls the digit stored in the E bit position of each storage location of the control RAM 55 associated with the call. When control RAM 55 transmits an address defining a data word to be read from receive time slot exchange 50, this control RAM is a time multiplexed line instead of the E bits stored in receive time slot exchange 50. The stored E bit is transmitted on (68). This operation allows the transmission of messages using the Ebit channel between time slot exchange units. The arrangement of FIG. 23 includes an E-bit accumulator 48 that receives an E-bit in each data word received on the time multiplexed line 70. This E bit is sent by the E bit accumulator 48 to the E bit check circuit 192. E-bit check circuit 192 responds to instructions from processor 66 on conductor 195 to send an output signal associated with E-bit of the selected data word to processor 66.

For example, during the communication line formation period, the processor 66 causes the E-bit check circuit 192 to notify the processor 66 if a particular channel examines the E-bit position and if logic 1 is received within a predetermined time period. 28 is a flowchart of the function performed by the E-bit check circuit 192. When the E bit of logic 1 is not found on a particular channel within a predetermined time period, a discontinuity signal indicating this fact is sent to processor 66 via conductor 193. As another example, the continuity signal is transmitted to processor 66 via conductor 194 when this logic 1 is found by E-bit check circuit 192 within the time period. E bit check circuit 192 examines the E bit of each active call. The discontinuity signal is sent to its associated processor 66 when the E bit of the active call goes to logic 1 and lasts for a fixed period of time. Any processor 66 that receives the discontinuity signal sends a control message to the central controller 30 indicating this fact.

FIG. 29 shows a portion of an E-bit check circuit 192 associated with one incoming channel, ie, a communication line. Timer 196 responds to instructions from processor 66 on conductor 195. Since the command is received from the processor 66 when the predetermined time period passes, the timer 196 transmits a logic 1 on the connected conductor 197 as an input to the AND gate 199, and the output of the AND gate 199. Is connected to conductor 193. The continuity signal generator 198 receives the E bit position of the associated channel and generates an output of logic 1 in the conductor 194 in response to the E bit of logic 1. Logic 1 on conductor 194 is applied continuously until the E bit of logic 0 is found by continuity signal generator 198. The output signal from the continuity signal generator 198 may be inverted and applied to the input of the AND gate 199. Thus, if timer 196 generates its logic 1 output, this output is via AND gate 199 when continuity signal generator 198 generates a logic 0 output (indicating that the E bit is not received). Will be applied to the conductor 193 as a discontinuity signal.

As another example, whenever continuity signal generator 198 generates a logic 1 output, the signal on conductor 193 remains logic 0 while the logic 1 continuity signal is transmitted on conductor 194. The function of the E-bit check circuit will be advantageously performed by the processor 66, thus eliminating the need for a separate E-bit check circuit 192. In realizing call completion, the use of the Ebit channel will be discussed in more detail later in this document.

The following is a description of the primary mode of communication between the various control entities of the switching system. The processor 66 performs a translation with respect to the dialed number in response to the fully dialed number, formulating a control message for the central controller 30 (FIG. 22), so that an idle time slot for the call is It can be formed through the time multiplexed switch 10. This control message is stored in the memory 57 by the processor 66. The DMA unit 58, well known in the art, reads the control message at a rate of 1 control word per frame and transmits it to the time multiplexed switch 10 on a time multiplexed line. The control word is sent to my control word source register 80 (FIG. 24). Similarly, control messages are received from other control units and the central controller 30 in the control word destination register 92 (FIG. 24) in the interface unit 69, and those control messages are sent to the processor 66. Is transmitted by the DMA unit 58 to the memory 57 which is read by. The interface unit 69 shown in detail in FIG. 24 includes a multiplex / demultiplex circuit 75 and two link interfaces 78, 79. The multiplex / demultiplex circuit 75 receives a data word from the receive time slot exchange unit 50 via a time multiplexed line 68 'and transmits via a time multiplexed line 70'. A time slot exchange 53 is connected to transmit a data word. It will be recalled that the two time multiplexed lines 68 ', 70' carry data words at a rate of 512 channels per 125 ms frame. The multiplex / demultiplex circuit 75 transmits a data word to each even channel on the time multiplexed line 77 and each transmits an odd channel to the time multiplexed line 76, thereby providing a line 68. The received information on ') is divided into two time multiplexed lines 76 and 77. Thus, each time multiplexed line 76, 77 carries information at a rate of 256 channels per frame.

Additionally, multiplex / demultiplex circuit 75 couples information on two 256-channel time multiplexed lines 85,86 to 512-channel time multiplexed line 70 '. This combination allows the data words from time multiplexed line 85 to be transferred from time multiplexed lines 85 and 86 while the data words from time multiplexed line 86 are transmitted to the even channel. Occurs by alternately transmitting The time multiplexed lines 76, 85 are connected to the link interface 78, and the time multiplexed lines 77, 86 are connected to the link interface 79. The time slot exchange unit 11 operates based on 512 time slots (channels) per frame, while the link interfaces 78, 79 and the time multiplexed switch 10 have 256 time slots (channels) per frame. It should be noted that this works based on.

Furthermore, the channels of data words received from and transmitted to the time slot exchange unit 11 are completely synchronous. That is, each time a channel having a destination of a given number is received by the link interface 78 from the time slot switching unit 11, the two link interfaces 78 and 79 are identical to the time slot switching unit 11. It will receive and transmit the channel with the destination of the number. All odd channels on the time multiplexed line 68 'are delayed by the multiplex / demultiplex circuit 75 to maintain synchronization after splitting so that the odd and next even channels are each time multiplexed. Are transmitted to equation lines 76 and 77 at about the same time. Similarly, each data word from the link interface 79 on the time multiplexed line 86 is a data word received with it almost simultaneously with itself by the multiplex / demultiplex circuit 75. Immediately following this is delayed by the multiplex / demultiplex circuit 75 to be transmitted to the time multiplexed line 70 '. The time slots of a given data word in the description below are referred to as time slots for the link interface 78,79 and the time multiplexed switch 10. For example, the data words from channel 1 and the data words from channel 2 of time multiplexed line 68 'may both be associated with link interface 78, 79 and time multiplexed switch 10. Associated with time slot channel 1. Each link interface unit 78, 79 is uniquely associated with one input / output port pair of the time multiplexed switch 10.

Link interface 78 (FIG. 24) receives data words transmitted serially from time multiplexed switch 10 via time multiplexed line 15 and serializes this information onto conductor 83. And a receiver 82 to retransmit. The clock recovery circuit 84 receives the incoming bit flow by connection with the conductor 83 and recovers the 32.768 MHz clock signal therefrom. This clock signal is used to provide timing for the link interface circuit 78. As described in more detail herein below, the information received on the time multiplexed line 15 is not necessarily in channel synchronization with that transmitted on the time multiplexed line 13. An incoming data word on conductor 83 is buffered in random access memory 87 to achieve channel synchronization between the data words on time multiplexed lines 76 and 85. The data word on the conductor 83 is written in the random access memory 87 at the position defined by the write address generator 88. The write address generator 88 receives the 2.048 MHz clock signal from the clock recovery circuit 84 and generates 256 write addresses in a cyclic sequence in synchronization with the incoming data word on the conductor 83 in response thereto. The data word is read from the random access memory 87 for transmission to the time slot exchange unit 11 at the position defined by the read address generator 89 which generates 256 read addresses of the cyclic sequence. The read address is derived from the information received from the offset circuit 90. The offset circuit 90 receives the write address generated by the write address generator 88, and effectively subtracts a predetermined number there.

The result of such subtraction is then sent to read address generator 89. In this manner, the read address generator 89 generates a series of read addresses that are about 1/4 frame (64 time slots) after the address generated by the write address generator 88.

The link interfaces 78, 79 of the interface unit 69 operate in master / slave mode to maintain channel synchronization. In this embodiment, the link interface 78 is a master and continues to operate in the manner described above. However, the read address generator of the link interface 79 is driven by the read address from the read address generator 89 of the link interface 78. It should be noted that, since the lengths of the time multiplexed lines 15 and 16 can vary, approximately one-quarter information frames can separate the write address and read address used for the link interface 79. . The reason for this is that the data words transmitted on the time multiplexed lines 85 and 86 are in channel synchronization, while this synchronization is necessary for the time multiplexed lines 15 and 16. Because it does not.

The same channel is used for a given link interface to send and receive control messages. The particular channel used by the link interface, eg interface 78, to carry the control message is preset and stored in the control channel register 81. Each read address generated by the read address generator 89 is sent to a comparator 91 which compares this read address with the preset control channel destination stored in the control channel register 81. When the comparator 91 determines that the instantaneous read address is the same as the control channel destination, the comparator generates a gating signal that is sent to the control word source register 80 and the control word destination register 92. The control word destination register 92 stores information on the time multiplexed line 85 in response to a gating signal from the comparator 91. During that particular channel, the information on the time multiplexed line 85 contains the contents of the control channel to be used by the control unit 17. By operation of the DMA unit 85, the contents of the control word register 92 are transmitted to the memory 57 before the next control channel. Similarly, control word source register 80 responds to the gating signal from comparator 91 by gating its content to time multiplexed line 76 and thus transmitting a control word. Control words are transmitted and received by the link interface 79 in a similar manner, but the particular control channel destination associated with the link interface 79 is different from that associated with the link interface 78.

The read address generated by the read address generator 89 may be sent to the frame sequence generator 93. Frame sequence generator 93 responds to the read address by generating a unique sequence of framing bits at a rate of 1 bit per channel. During each channel, the bits generated by the frame sequence generator 93 are transmitted to the frame insertion circuit 94 which positions the framing bits to the G bit positions of the data words from the time slot exchange unit 11. The data word containing these framing bits is connected to a time multiplexed line 13 connected to the only input port of the time multiplexed switch 10 via the parallel-serial register 95 and the drive circuit 96. Is sent. Each data word received by the link interface 78 includes a framing bit that is generated and transmitted by the time multiplexed switching 10. Frame checker 97 reads each framing bit of each data word from time multiplexed switch 10, and the communication between time multiplexed switch 10 and frame checker is still in sync. Determine if there is. If synchronization is not corrected, then synchronization is achieved by communicating with the clock recovery circuit 84 in a manner well known in the art.

The input / output ports of the time multiplex switch 10 may be considered as a pair since both ports are connected to the same link interface. Further, each input / output port pair of the time multiplexed switch 10 is connected to a time multiplexed switch link interface similar in form to the link interfaces 78 and 79. Link interlace 78 receives receiver 101 that receives data words from time multiplexed line 13 and transmits those data words to serial-parallel register 102 via time multiplexed line 103. A time multiplexed switch link interface 100 (FIG. 25). The bit flow from the time multiplexed line 103 may be applied to the clock circuit 104 and the frame check circuit 105, respectively, which derive a clock signal and determine whether frame synchronization is present. The time multiplexed switch link interface 100 also includes a write address generator 106 that generates a series of write addresses in response to signals from the clock recovery circuit 104. Each data word sent to serial-parallel register 102 is written to random access memory 107 at the address generated by write address generator 106.

The time multiplexed switch 10 also includes a time division, space division switch 108 that operates in a frame of 256 time slots of about 488 ns to complete the line between its input and output ports. Control information defining the switching line between the input port and the output port to be connected during each time slot is stored in control memory 29 (FIG. 22) which is read out for each time slot to form such a connection. Note that each time slot has a numbered destination, and that a data word channel having the same number of destinations for a given time slot is switched. Thus, all data words in a channel with a given number of destinations must be transmitted to the time division, space division switch 108 during their associated time slots to avoid incorrect switching. For this purpose, the time multiplexed switch 10 includes a master clock circuit 109 for generating 256 read addresses of a cyclic sequence transmitted almost simultaneously to each random access memory of each time multiplexed switch link interface. do. Thus, the equivalent random access memory included in the random access memory 107 and all other time multiplexed switch link interfaces reads data words associated with the same time slot almost simultaneously. The data words read from the random access memory 107 are sent to the parallel-serial shift register 110, and the data words are sent from the parallel-serial shift register 110 to the time division, space division switch 108.

All data words to be transmitted to the link interface 78 on the time multiplexed line 15 are time-divided, space-divided switches 108 on the conductors 11 in one time slot to transmit to the time-division, space-dividing switch 108. Is received from. The time multiplexed switch link interface 100 includes a frame sequence generator 112 that generates a series of framing bits at a rate of 1 bit per slot per hour. The framing bits are transmitted to the frame insertion circuit 113 where each data word on the conductor 11 places the frame bits at bit position G. Each data word on conductor 111 is transmitted to link interface 78 via drive circuit 114 and via time multiplexed circuit 15.

The following is an example of call setup and removal in the system of FIG. In this embodiment, the subscriber in subscriber set 23 wishes to call subscriber 26. The line unit 19 detects the originating off hook at the subscriber set 23 and transmits a message to the control unit 17 via the communication line 27. In response to this message from the line unit 19, the control unit 17 issues a command specifying which communication channel between the line unit 19 and the time slot exchange unit 11 is to be used for data word communication. Transmit to line unit 19. Furthermore, the control unit 17 starts to transmit a dial tone on the channel associated with the new off hook subscriber between the time slot exchange unit 11 and the line unit 19. The control unit 17 then checks the DC state of the subscriber set 23. The control unit 17 detects dialing of the digits in the subscriber set 23 and finishes the dial tone in response to this first digit. Based on the fully dialed number and the identity of the calling subscriber, the control unit 17 formulates a control message for the central controller 30. This control message includes a central controller 30 that identifies the destination portion and further includes the originating subscriber identity, the called party identity, and some originating subscriber related information, such as the service class.

27 is a functional diagram by communication between processors for call establishment between subscribers. In FIG. 27, the originating unit 190 represents the originating subscriber set 23, the line unit 19, the time slot exchange unit 11, and the control unit 17. In FIG. Similarly, the destination unit 191 represents the destination subscriber set 26, the line unit 22, the time slot exchange unit 12, and the control unit 18. Each communication in the call completion sequence is indicated in FIG. 27 by a line ending with an arrow head indicating its direction and having an associated letter (a) to (g). In the course of the following description, the letters a to g are used to identify the particular communication discussed. The control message a formulated by the control unit 17 of the originating unit 190 is transmitted one control word per frame to the control channel of the time multiplexed line 13 as already described. The time multiplexed line associated with the odd input / output port is the primary time multiplexed line used to carry control messages. Time multiplexed lines associated with even input / output port pairs are used to carry longer messages, such as program and / or data update messages. Thus, the control channel of the time multiplexed line 13 is used to carry control messages in this embodiment. The control word in this control channel is switched to the control distribution unit 31 by the time multiplexed switch 10 during the time slot associated with that control channel. As already explained, the control distribution unit 31 interprets the destination portion of the received message and transmits the message to the central controller 30.

The central controller 30 calculates the identity of the time slot exchange unit associated with the called party identity and allocates an idle time slot for communication between the sender and the called party. In this embodiment, time slot TS16 is assumed to be selected for this communication. The central controller 30 then controls the time slot exchange unit 12 of the destination unit 191 connected to the subscriber set 26 via the control distribution unit 31 and the time multiplexed switch 10. Send a message (b). This control message (b) comprises the identity of the called subscriber, the identity of the time slot exchange unit 11 connected to the originator, and the time slot to be used for communication via the time multiplexed switch 10. At about the same time as the central controller 30 transmits the control message b to the time slot exchange unit 12, the central controller 30 commands the control memory 29 via the communication line 49. c) transmit and the command defines a switching line to be used during time slot TS16 to connect time slot exchange unit 11 and time slot exchange unit 12. The control unit 18 of the terminating unit 191 responds to the control message b from the central controller 30 to transmit the line unit 22 and the time slot exchange unit 12 for communication with the subscriber set 26. Assigns a channel in between, and starts transmitting the E bit d of logic 1 to the time multiplexed switch 10 in the channel associated with the subscriber set 26. Recall that the control unit controls the transmission of the E bits of logic 1 to a given channel by accessing the storage location of RAM 55 associated with the given channel and setting its E bit position to logic 1. Further, the control unit 18 may include an identity of the time slot exchange unit 12 of the destination unit 191, a time slot TS16 to be used for communication, and a set of subscribers necessary for the control unit 17 to complete the call. Formulate a control message that defines all information about (26).

The control message e passes again through the time multiplexed switch 10 in the control channel associated with the time slot exchange unit 11 and via the control channel of the time multiplexed switch 10 and the control distribution unit 31. Is transmitted to the time slot exchange unit 11 of the originating unit 190. In addition, the processor 66 of the control unit 18 instructs the E bit check circuit 192 to examine the state of the E bit in the time slot TS16 for a predetermined time period, for example 128 frames.

In response to the message from the control unit 18, the control unit 17 starts transmitting the E bit f of logic 1 to the time multiplexed switch 10 in the channel associated with the subscriber set 23. Further, the control unit 17 of the originating unit 190 checks the E bit of the channel 16 entering from the time slot exchange unit 12 while logic 1 is present. When this E bit of logic 1 is received, the continuity signal is transmitted from the E bit check circuit 192 to the processor 66 of the control unit 17, which is the time slot exchange unit 111 in the time slot exchange unit 12. Indicates that the communication line up to) is known. When there is continuity of the communication lines from the time slot exchange unit 11 to the time slot exchange unit 12, the E-bit check circuit 192 of the control unit 18 performs logic 1 on the channel 16 for a predetermined time period. Will detect the E bit. The E bit check circuit 192 of the control unit 18 transmits a continuity signal to its associated processor 66 in response to the E bit of logic one. In response to the continuity signal from the E bit check circuit 192 of the control unit 18, the line unit 22 is notified to send the call current to the subscriber set 26, and the audible call tone is time slot TS16. Is returned to the subscriber set 23. When the subscriber set 26 goes off hook, the line unit 22 terminates the transmission of an audible call tone to the subscriber set 23 and terminates the application of the call current to the subscriber set 26. 18). The control unit 18 then sends a control message from the time slot exchange unit 12 to the time slot exchange unit 11 via the control channel, indicating that a response has occurred. This enables communication between subscribers.

The call termination is normally controlled by the control unit associated with the calling subscriber which is the control unit 17 in this embodiment. When subscriber set 23 goes on hook, the E bit in the channel between subscriber set 23 and subscriber set 23 turns to logical zero. The control unit 18 sends a control message to the central controller 30 in response to the E bit of logic 0, which specifies that the portion of the call is to be terminated. Similar messages are also sent from the control unit 17 when an on hook is detected. In response to these two messages, central controller 30 controls control memory 29 to break the line connecting the channel between subscriber set 23 and subscriber set 26. Furthermore, control units 17 and 18 idle the lines from their associated subscriber sets to the time multiplexed switch 10 to be used for other communications. When the subscriber set 26 goes on hook, it sends a control message to the control unit 17 via the control channel indicating that the on hook has occurred to the control unit 17. In response to this message, the control unit 17 waits for a predetermined period of time similar to hit timing and then initiates a call termination procedure as described above.

The called party may have certain characteristics that alter the normal call completion / end routine. By way of example, subscriber 26 (receiving subscriber of the above embodiment) should receive call tracking. In this situation, all calls directed to subscriber 26 preferably remain complete until subscriber 26 is on hook. According to this embodiment, the call is made in the same manner as described in the above embodiment. However, the first control message from the time slot exchange unit 12 to the time slot exchange unit 11 includes a portion indicating that call tracking is working for a call that will soon be completed. The control unit 17 modifies the call termination order in response to this control message so that the completed line is not removed until a message indicating that the subscriber 26 is on hook is received from the control unit 18.

Exemplary Embodiments of the Invention

An exemplary embodiment of the invention shown in FIGS. 1 to 3 arranged in accordance with FIG. 12 is a combination of four additional switching modules 1000, 2000, 3000, and 4000. A 22 degree time division, circuit switching system is included. Additional switching modules are connected using input / output port pairs P55 to P62 of the time multiplexed switch 10. Only switching modules 1000, 4000 are shown in detail in FIGS. 2 and 3. A given switching module, e.g. 1000, may be configured to provide a plurality of user terminals, e. Provide such a channel between < RTI ID = 0.0 > Time multiplexed switching 10 is only used for inter-module calls.

Switching module (1000)

Switching module 1000 (FIG. 2) includes two digital line units 1101 and 1102, time slot exchange unit 1011, control unit 1017, processor interface 1300 and packet switching unit 1400. do. The time slot exchange unit 1011 and the control unit 1017 are almost identical to the time slot exchange unit 11 and the control unit 17 (Fig. 23) already described. In this embodiment, the communication between the user terminal and the control unit 1017 is performed using message signaling via the user D channel, the packet switching unit 1400, and the processor interface 1300, so on hook and off hook. The processor function required in the control unit 17 to detect the status, dialed digits, etc. is not required in the control unit 1017. In the control unit 17, the control interface 55 (FIG. 23) is used to convey control information to the line unit via the line 27. In the control unit 1017, the equivalent of the control interface 56 is used to convey control information to the digital line units 1101, 1102 and the packet switching unit 1400 via the communication line 1027. A bus 1059 equivalent to the bus 59 in the control unit 17 used for communication with the processor 66 is connected to the processor interface 1300 and provides signaling information between the user terminal and the control unit 1017. Means of transport.

Digital Line Unit (1101)

Digital line unit 1101 is shown in more detail in FIG. Each user access line, such as 1003, terminates on a separate one of the plurality of digital line circuits 1105.

Recall that in this embodiment, user access line 1003 is a four-wire T interface that carries a bit flow of 192 Kbps in each direction on separate wire pairs. 144 Kbps is used to carry user information including message signaling, and 144 Kbps includes two 64 Kbps circuit switched B channels and one 16 Kbps packet switched D channel. The user terminal 1001 transmits a 192 Kbps bit flow in a 48 bit line frame at a rate of 4000 line frames / second. Each 48-bit line frame contains a framing bit, various other control bits, a DC balance bit, a super frame bit, and a spare bit, which use bipolar disturbance to mark the beginning of the frame, and 8 bits of each of the two B channels. It includes two generations and two bit generations of a single D channel. Digital line circuitry 1105 receives a 192 Kbps bit flow from the user terminal 1001 via converter coupling to provide DC isolation, common mode signal exclusion, and overvoltage protection. Digital line circuitry 1105 detects the beginning of each lime frame and then stores information from two B channels and a single D channel in a separate register (not shown). The information thus received is transmitted to the second time slot assignment unit 1112 on the 32-way bidirectional bus 1109. Information defining a particular time slot or channel on one of the two buses 1108 or 1109 to which each B and D channel is to be transmitted is a line aggregation controller 1106 that coordinates the operation of the 16 digital line circuits 1105. Is determined based on the information received. A time slot given to one of the buses 1108 includes one 8-bit occurrence of one B channel from one digital line circuit 1105 and two D channels from each of four circuits of the digital line circuit 1105. It is used to transmit one bit generation. The time slot assignment unit 1111 receives information from one group of the sixteen line circuits 1105 via one of the buses 1108.

Similarly, time slot assignment unit 1112 receives information from one group of sixteen line circuits 1105 via one of buses 1109. Buses 1108 and 1109 may be load distributed according to assignment by line aggregation controller 1106 which defines a mapping between user B and D channels and time slots on buses 1108 and 1109. Can be. This line controller 1106 in turn receives their information from the single line unit controller 1107 communicating with the control unit 1107 via the communication line 1027 to initiate this idea. The line unit controller 1107 also controls the operation of the time slot assignment units 1111 and 1112. The function of the time slot assignment unit 1111, 1112 is to transfer the time slot received from the digital line circuit 1105 to the time slot exchange unit 1011 on the specified time slot of the 32-channel bidirectional data bus 1201, Or a packet switching unit 1400 on a specified time slot of a 32 channel bidirectional data bus 1202. Bus 1201 carries primarily B channel information, but some D channel information is carried on that bus and then packet switching unit 1400 via time slot exchange unit 1011 and bus 1205 in a later scheduled channel. Is sent to. The bus 1202 carries only the D channel information directly to the packet switching unit 1400.

The time slot assignment units 111 and 112 receive information from the time slot exchange unit 1011 on the bus 1201 and from the packet switching unit 1400 on the bus 1202 and thus receive in a specific time slot. It also operates to transmit the obtained information to the digital line circuit 1105. Each digital line circuit 1105 receives two B-channels and a single D-channel from the relevant time slots on the buses 1108 and 1109 and formats the received information into 48-bit line frames. This line frame is transmitted at a rate of 192 Kbps via a transformer coupled to the user line, for example 1003.

Packet Switching Unit (1400)

A more detailed diagram of the packet switching unit 1400 and the processor interface 1300 is shown in FIGS. 5-11 arranged in accordance with FIG. 13. The packet switching unit 1400 stores the time slots received on the bus 1202 from the digital line units 1101 and 1102 and on the bus 1205 from the time slot exchange unit 1011. 6 data fanout units 1602-0 through 1600-5 (FIG. 7), which distributes to 0) through 1700-95, and FIG. Only 0), 1700-15, 1700-80, and 1700-95 are shown in detail. Data fanout units 1600-0 through 1600-5 send information received from the control regulator to the digital line units 1101, 1102, and bus 1205 in the assigned time slots on bus 1202. To the time slot exchange unit 1011. Each data fanout unit is associated with 16 protocol coordinators.

For example, data fanout unit 1602-0 is associated with protocol coordinators 1702-1 through 1700-15, and data fanout unit 1600-5 is associated with protocol coordinators 1700-85 with 1700-0. 95). The data fanout units 1600-0 to 1600-5 communicate allocation information, referred to herein as allocation signals, regarding the mapping of time slots between the protocol coordinator and the buses 1202 and 1205 from the control unit 1017. Receive via line 1027, data fanout unit 1500 (FIG. 6), and control bus 1501. Protocol coordinators 1700-1 through 1700-95 receive, process, and store packets (or intermodule packets via bus 1205) from the D channel of the user terminal associated with these coordinators. When enabled by 1800 (FIGS. 10 and 11), the stored packets are transmitted to the destination protocol coordinator or, in the case of signaling packets, to the processor interface 1300 (FIG. 5). The destination protocol coordinator stores the packets received from the packet interconnector 1800 and subsequently transmits such packets to the D channel of the destination user terminal. The processor interface 1300 stores such signaling packets to be subsequently read by the control unit 1017 via the bus 1059 in response to the signaling packets from the protocol coordinator. The processor interface 1300 also receives signaling information recorded via the bus 1059 by the control unit 1017 and stores this information in the signaling packet, and the signal to be enabled by the packet interconnector 1800. Sends a packet to the destination protocol coordinator. At any given time, multiple protocol coordinators are reserved.

These redundant destinations and other configuration and control information are transmitted by the control unit 1017 to the packet interconnector 1800 via the communication line 1027, the control fanout unit 1500 and the control bus 1502. . Packet interconnect 1800 distributes certain control information to a particular protocol coordinator via control buses 1702-0 through 1702-5 (FIG. 9). The packet interconnector 1800 includes six fanout units 1900-0 through 1900-5 (FIG. 11). Each data fanout unit receives packets from the 16 protocol coordinators and sends them to the 16 protocol coordinators. For example, data fanout unit 1900-0 receives packets from protocol coordinators 1700-0 through 1700-15 and transmits packets to these coordinators, and data fanout unit 1900-5 is protocol coordinator. Receive packets from 1700-80 through 1700-95 and send packets to these coordinators.

Data Fanout Unit (1600-0)

The data fanout unit 1600-0 (FIG. 7) is a time slot exchange unit 1011 from the digital line units 1101, 1102 on the 32 channel bus 1202, and on the 32 channel bus 1205. And a multiplexer 1610 that receives the time slots and transmits the received time slots to the receiving time slot exchange 1650 on a single time multiplexed line 1612. Receive time slot exchange 1650 performs a time slot exchange function by transmitting information received from multiplexer 1610 to demultiplexer 1620 at a predetermined time slot on time multiplexed line 1613. The time slot definitions used by the receive time slot exchange 1650 are stored in the control RAM 1655 by the processor 1632 at system initialization or subsequent system reconfiguration. Processor 1632 is a universal asynchronous receiver, transmitter (UART) 1631, control bus 1501 and associated UART 1511-0 from processor 1510 included in control fanout unit 1500 (FIG. 6). Receive these time slot definitions via. The demultiplexer 1620 connects the 16 slots 160-0 to 1700-15 associated with the data fanout unit 1600-0 in a predetermined manner over time slots on the time multiplexed line 1613. It is divided into 32 channel bidirectional data buses (1601-0) to (1601-15).

Similarly, multiplexer 1621 in the reverse direction receives time slots on 32 channel buses 1601-1 through 1601-15 from protocol coordinator 1702-1 through 1700-15, and a single time multiplex. The time slot received on equation line 1614 is transmitted to transmit time slot exchange 1643. In accordance with the time slot definition stored in the control RAM 1655, the transmit time slot exchange 1653 transmits the information received from the multiplexer 1621 to the demultiplexer 1611 on the single time multiplexed line 1615. The demultiplexer 1611 transmits the time slots received on the time multiplexed line 1615 to the bus 1202 and to the time slot exchange unit in a predetermined manner to transmit to the digital line units 1101, 1102. To bus 1205 for transmission to 1011. Note that bus 1205 is connected to only one of the data fanout units, namely unit 1600-1. The data fanout unit 1600-0 receives timing signals from the time slot exchange unit 1011 via the bus 1205 and assigns time slots included in the protocol coordinator to appropriately adjust the operation timing of the various devices. And the timing adaptation unit, for example such a timing signal to each of the data fanout units 1600-1 to 1600-5, as well as to the unit 1405 in the protocol regulator 1700-0 (FIG. 8). To distribute. The distribution of the timing signals is not shown in the figure. Although the operation of the data fanout unit 1600-0 is generally similar to the operation of the time slot exchange unit 11 (FIG. 23) already described, the time slot exchange unit 11 has a line switching function, i.e. While performing the function of slot swapping to provide a communication channel for the call, the data fanout unit 1602-0 is relatively permanently assigning each time slot on the buses 1202, 1205 to the bus 1601-0. Mapping to the designated time slot on 1601-5 only performs the distribution function, not the switching function for the call.

Protocol Regulator 1700-0

The protocol coordinator 1700-0 (FIG. 8) is a time slot connecting the bidirectional data bus 1601-0 from the data fanout unit 1160-0 to 32 HDLC circuits 1406-0 through 1140-31. Allocation and speed adaptation unit 1405. Each HDLC circuit, for example (1406-0), is used to terminate the HDLC link level protocol from the 16 Kbps D channel of one user terminal, also referred to herein as a protocol processor. A given channel, or time slot, on data bus 1601-0 is used for up to four D channels, eight bits of two bits from each D channel. The time slot allocation and speed adaptation unit 1405 includes a 32 incoming shift register (not shown), one incoming shift register and one outgoing shift register for each HDLC circuit. A given incoming shift register receives two bits from a predetermined time slot on data bus 1601-0 during each 125 ms frame. After four such frames, a given incoming shift register has accumulated eight bits, and unit 1405 sends a clock signal to the associated HDLC circuit, for example 1406-0, which accumulated eight bits are HDLC circuits. Is sent to (1406-0). Since a given incoming shift register only receives information from a one time slot / 125 ms frame, this bit may be set by the HDLD circuit 1402 from the incoming shift register at a lower rate than those received from the data bus 1601-0. 0). In the reverse direction, HDLC circuit 1406-0 sends 8 bits to a given fetch shift register, which bits are inserted into a predetermined time slot in data bus 1601-0. Two bits are inserted during the generation of each predetermined time slot over four 125 ms frames. The time slot allocation and rate adaptation unit 1405 reconfigures a given HDLC circuit to terminate the D channel at a higher rate, such as 64 or 256 Kbps, using multiple incoming and outgoing shift registers and multiple time slots. Can be.

The protocol coordinator 1700-0 includes three control entities, a processor 142, a DMA processor 1423, and a communication controller 1443. DMA processor 1423 is a low-level processor that must transfer information via bus 1420 between HDLC circuits 1406-0 through 1140-31 and a buffer in RAM 1470. The communication controller 1443 performs a function similar to transferring information via the bus 1440 between the bus 1701-0 (connected to the packet interconnect 1800) and a buffer in the RAM 1470. Processor 1442 represents the higher intelligence of protocol coordinator 1702-0. The DMA processor 1423 has an associated erasable and programmable read only memory (EPROM) 1421 for storing the program and an associated RAM 1422 for storing the program stack and various local variables. The processor 1422 also includes an associated EPROM 1421 to store the program. The dual port RAM controller 1471, the error detection and correction unit 1472, and the selector 1473 are associated with the RAM 1470. In this embodiment, the RAM 1470 is realized with 22 memories having 256 kilo and 22 bit positions, each having 256 kilo and 1 bit positions. Each position of the RAM 1470 is used to store a 16-bit data word and a 6-bit error check code generated by the error detection and correction unit 1472. The error check code is used by the unit 1472 to correct all single bit errors and to detect all double bit errors in the data words read from the RAM 1470. The dual port RAM controller 1471 transmits a select signal to the selector 1473 which defines which of the two buses 1420,1440, is accessed at a given time. RAM 1470 includes two system control blocks (not shown), one of which is associated with DMA processor 1423 and the other is associated with communication controller 1443. Processor 1442 writes control information via bus 1400 to the appropriate system control block of RAM 1470 and then the control signal via conductor 1431 to DMA processor 1423 or via conductor 1445. By transmitting to the communication controller 1443, the DMA processor 1423 and the communication controller 1443 read their associated system control blocks in the RAM 1470 to determine what action is required by the processor 1442. The RAM 1470 is a plurality of predetermined standards for storing packets received from the HDLC circuits 1406-0 to 1402-31 and packets received from the packet interconnector 1800 via the bus 1701-0. It also contains a buffer of. Each such buffer has an associated buffer control block that defines certain characteristics of the buffer, such as, for example, the buffer specification. A given packet requires several buffers connected in a chain. Each buffer control block defines the position of the next buffer in this chain.

At system initialization, the control unit 1017 passes through the communication line 1027, the control fanout unit 1500 and the control bus 1052, so that the processor 1922 (FIG. 11) is connected to the bus 1702-0. It affects the transmission of the reset signal to the processor 1442 on the conductor. In response, the processor 1442 returns to a known state and then writes a read command via the bus 440 into the system control block of the RAM 1470 for the communication controller 1443. The processor 1442 transmits a control signal to the communication controller 1443 on the conductor 1445, and in response, the communication controller 1443 reads the system control block of the RAM 1470. The system control block also includes information defining a list of available buffers to be used by the communication controller 1443 to store packets. In response to the read command in the system control block, the communication controller 1443 starts listing on the bus 1701-0 for the start of the packet. As part of the initialization, the control unit 1017 sends initialization information to the processor interface 1300. At this time, the processor interface 1300 (already initialized by the control unit 1017 in a manner similar to that described for the protocol coordinator 1700-0) transmits a packet containing initialization information to the packet interconnect 1800 and the bus. Send to protocol coordinator 17000-0 via (1701-0). The communication controller 1443 detects the beginning of the packet and allocates one or more available buffers in the RAM 1470 to be used to store the packet. When the communication controller 1443 detects the end of the packet, this controller reads the initialization packet via the conductor 1444 via an interrupt signal. The initialization packet contains system configuration information. This information may be associated with time slot assignments, such as, for example, time slots on data bus 1601-0, and with specific HDLC circuitry to operate at various defined rates, such as 16, 64, or 256 Kbps. And a definition for the configuration of the speed adaptation unit 1405. The processor 1422 sends this configuration information to the time slot assignment and speed adaptation unit 1405 via the bus 1440.

The processor 1442 then sends an acknowledgment packet to the processor interface 1300 via the communication controller 1443 and the packet interconnect 1800. The acknowledgment packet is read in sequence by the control unit 1017. In response, the control unit 1017 affects sending another initialization packet to the RAM 1470 of the protocol coordinator 1700-0. Processor 1442 reads this packet from RAM 1470. This packet specifies which of the current HDLC circuits is associated with the active user terminal. In response to this packet, the processor 1442 writes an instruction into the RAM 1470 system control block for the DMA processor 1423. Processor 1442 transmits a control signal to DMA processor 1423 via conductor 1431, and in response, DMA processor 1423 reads the command in the system control block via bus 1420. . Based on this instruction, the DMA processor 1423 requires any one of the HDLC circuits 1406-0 through 1140-31 to initialize the HDLC communication link with the equivalent HDLC circuit (not shown) at the associated user terminal. The control information is transmitted via the bus 1420. Link initialization involves the continuous transmission of idle flags by the HDLC circuit at each end of the link. HDLC circuits perform HDLC link level functions such as bit stuffing, error checking, and the like in a manner well known in the art. The DMA processor 1423 repeatedly scans each HDLC circuit 1406-0 through 1140-31 to determine when the start of a packet has been received. If the HDLC circuitry, for example 1406-0, determines that it has received the start of the packet, the processor 1423 selects at least an available RAM 1470 buffer to be used to store at least the initial portion of the packet. Processor 1423 stores the address of the selected buffer in its associated RAM 1422. Each byte received by the HDLC circuit 1406-0 is then delivered via the bus 1420 to the selected RAM 1470 buffer based on the address stored in the RAM 1422.

Alternatively, RAM 1422 can be used to temporarily store alternating bytes such that an entire 16 bit word can be sent to RAM 1470. Of course, if a packet is configured to be long enough to exceed the first allocated buffer, additional buffers are allocated as needed. The entire chain of buffers used to store stable packets is linked together through pointers stored in a buffer control block associated with the buffer. When the HDLC circuit 1406-0 determines that the entire packet has been received, this HDLC circuit stores the bits thus indicated in an internal register (not shown). The circuit also stores a bit indicating whether the HDLC frame containing the packet was received without error. The DMA processor 1423 reads the bit indicating the end of the packet and in response sends an interrupt signal to the processor 1442 via the conductor 1432. In response, processor 1422 reads at least the header of the picket from RAM 1470 via the bus. If the header indicates that the packet is a signaling packet, i.e., if the header specifies logical channel LCN1, then the processor 1442 allows the communication controller 1443 to send the packet in the inner packet frame via the packet interconnect 1800. It affects the transmission to the interface 1300. Part of the inner packet frame defines the physical address of the processor interface 1300 as the destination of the packet. On the other hand, when the processor 1442 determines that the packet is a data packet when the head of the packet is read from the RAM 1470, the processor 1442 refers to a routing table stored in the RAM 1470. Thus, in sending a packet from the correct logical channel to the correct user terminal, both the physical address of the destination protocol coordinator and the internal protocol channel number to be used by the destination protocol coordinator are determined (which forms the actual circuit between the two user terminals). The storage of this routing table at the processor is described later herein).

Processor 1442 affects communication controller 1443 sending data packets in an inner packet frame to destination protocol coordinator via packet interconnect 1800. The inner packet frame includes both the physical address of the destination protocol coordinator and the ILCN. The inner packet frame also includes the physical address of the source protocol coordinator, namely 1700-0, to be used by the destination protocol coordinator in sending the acknowledgment packet back to the source protocol coordinator. Within protocol coordinator 1702-0, processor 1442 is responsible for all network level functions such as signaling and proper routing of data packets, for example. The processor 1442 also performs the mechanics of retransmitting the HDLC frame when it determines via the DMA processor 1423 that the frame is received in error.

The communication controller 1443 transmits packets from the HDLC circuits 1406-0 to 1140-31 to the buffers in the RAM 1470 in a manner similar to that of the DMA processor 1423. An incoming packet received on the bus 1701-0 from the bus 1701 to an available buffer in the RAM 1470. In the case of a data packet, the processor 1442 uses the routing table stored in the RAM 1470 again to send the data packet to the correct HDLC circuit with the correct LCN. The signaling packet received on the bus 1701-0 from the packet interconnector 1800 is processed by the processor 1442 in writing the necessary entries in the routing table of the RAM 1470 in the processor forming the actual circuit. The other signaling packets received on the bus 1701-0 are used by the user terminal via HDLC circuits 1406-0 through 1140-31 based on their ILCN and routing table of the RAM 1470. Is routed to

Although not shown in the figure, the protocol coordinator 1702-0 further includes a replication communication controller connected on the protocol coordinator 1440. The register 1447, which stores the status bits received from the processor 1922 via the bus 1702-0, stores bits that define whether the current communication controller 1443 is operating or the duplicate communication controller.

Processor Interface (1300)

Most of the processor interface 1300 (FIG. 5) is the same as the protocol coordinator 17000-0. In particular, EPROM 1341, bus 1340, processor 1342, conductors 1344, 1345, communication controller 1343, selector 1373, dual port RAM controller 1372, RAM 1370, And the error detection and correction unit 1372 matches exactly the corresponding element of the protocol coordinator 1700-0 numbered exactly 100 larger numbers. However, as with the RAM 1470 in the protocol coordinator 1700-0, instead of receiving information from the 32 HDLC circuits, the RAM 1370 of the processor interface 1300 is transferred from the control unit 1017 to the bus 1059. And the buffer 1352 are received. The address counter 1351 is used as a means for indirectly addressing a position in the RAM 1370 by the control unit 1017. For example, in order to write certain control information in the RAM 1370, the control unit 1017 writes in the address counter 1351 the address of the first RAM 1360 buffer to be used to store this information. When the first RAM 1370 buffer is filled, the address counter 1351 is automatically incremented to define the location of that buffer. The processor 1342 may be reset by the control unit 1017 to reinitialize the system via one conductor of the bus 1059.

Packet Interconnector (1800)

In addition to the processor interface 1300 and the duplicate processor interface (not shown), the protocol coordinators 1700-1 through 1700-95 use six conductor buses (or another example, a bus including six pairs) to process packets. And are connected to interconnectors 1800 (FIGS. 10 and 11), respectively. The replication processor interface is used to connect the packet interconnector 1800 of the replication control unit (not shown) used to control the switching module 1000 in the event of a failure of the control unit 1017. The protocol coordinators 1700-1 through 1170-95 are connected to the packet interconnector 1800 by buses 1701-0 through 1701-95. It is connected to the packet interconnector 1800 by the protocol interface 1300 and the replica processor interface buses 1301 and 1302. Buses 1701-0 through 1701-95, 1301, and 1302 each provide three signals: a transmit request (RTS) signal, a clock transmit (TC) signal, and a data transmit (TD) signal. 1800, and are used to receive three signals, namely a transmit clear signal (CTS), a clock receive (RC) signal, and a data receive (RD) signal from the packet interconnector 1800. For example, protocol coordinator 1700-0 operates as follows to transmit a packet via packet interconnect 1800. When the communication controller 1443 of the protocol coordinator 1702-0 determines that it is ready to send a packet to the packet interconnect 1800, the controller transmits a logical 0 RTS signal to the packet interconnect 1800. . Packet interconnect 1800 then returns a logic 0 CTS signal to protocol coordinator 1700-0. In response, the communication controller 1443 of the protocol coordinator 1702-0 sends the packet to the packet interconnector 1800 as a TS signal as well as the bit rate clock as the TC signal. Operation of the packet interconnector 1800 allows only one protocol coordinator or processor interface to be transmitted at a time.

The TD signals and TC signals transmitted by the protocol coordinator 1700-0 are not only the processor interface 1300 and the duplicate processor interface, but also their RD and RD signals by the protocol coordinator 1700-1 through 1700-95, respectively. Is received as. However, only one destination is typically defined by the physical destination address at the beginning of the packet, and only that destination uses the RC signal to clock the bits of the packet to its communication controller for later storage.

The packet interconnector 1800 realizes two selection levels in allowing transmission to the protocol coordinator and processor interface. At lower levels, six fanout units 1900-0 through 1900-5 (FIG. 11) are used to select among 96 protocol coordinators 1700-0 through 1700-95. For example, the packet fanout unit 1900-0 selects among 16 protocol coordinators 1700-1 through 1700-15, and the packet fanout unit 1900-5 selects 16 protocol coordinators 1700-80. ) To (1700-95). At a higher level, selector unit 1810 (FIG. 10) is used to select between six fanout units 1900-0 through 1900-5, processor interface 1300, and duplicate processor interface. Packet interconnect 1800 executes a fixed selection order. By two levels of selection, each processor interface is enabled 16 times to enable each individual protocol coordinator respectively.

Packet fanout unit 1900-0 (FIG. 11) provides three 16: 1 multiplexers 1931, each receiving RTS, TC and TD signals from protocol coordinators 1700-0 to 1700-15, ( 1932 and (1933). RTS signals from protocol coordinators 1700-1 through 1700-15 are received by sixteen AND gates 1924-0 through 1924-15. The enable latch 1923 specifies whether each of the sixteen protocol coordinators 1700-1 through 1700-15 is currently operating or stores 16 bits that are held as a reserve. The bit is enabled by the processor 1922 receiving this information from the control unit 1017 via the UART 1921, the control bus 1502, the control fanout unit 1500 and the communication line 1027. (1923). For example, enable latch 1923 sends a logic 1 signal to AND gate 1924-0 when protocol coordinator 1700-0 operates. Thus, the RTS signal from protocol coordinator 1700-0 is transmitted to multiplexer 1931 by AND gate 1924-0. By operation of the multiplexers 1931, 1932, and 1933, the RTS, TC, and TD signals transmitted by the one of the selected protocol regulators 1700-0 to 1700-15 are selected by the selection unit 1810. Is sent at a higher selection level. The packet fanout unit 1900-0 includes a 1: 16 demultiplexer 1941, whereby the CTS signal from the selection unit 1810 is selected from among the protocol regulators 1700-0 through 1700-15. May be sent to. Selection by the multiplexers 1931, 1932, 1933 and demultiplexer 1941 is generated by a 7-bit binary counter 1982 (FIG. 10) and via a bus 1898 a packet fanout unit ( 1900-0) through four higher order bits transmitted to (1900-5).

Thus, for a given count of counters 1822, multiplexers 1931, 1932, and 1933 are the RTS, TS, and TD received from one of the given coordinators of protocol coordinators 1700-0 to 1700-15. Demultiplex 1941 transmits the CTS signal to its given protocol coordinator. The packet fanout unit 1900-0 includes two buffers 1942 used to transmit the RC and RD signals received from the selector unit 1810 to the respective protocol coordinators 1700-1 through 1700-15, (1943) further. Recall that RC and RD signals are sent to both the protocol coordinator and the protocol interface, but typically only one receiver actually remembers the transmitted packet for subsequent transmission. -0) to (1701-15) act to electrically insulate the RC and RD conductors, while allowing signals on these conductors to be transmitted to respective protocol regulators 1700-0 to 1700-15.

The selector unit 1810, which represents a higher selection level to choose between the six packet fanout units 1900-0 through 1900-5, the processor interface 1300, and the replica processor interface (not shown), has six packets. Three 8: 1 multiplexers 1831, 1832, and 1833 to receive the RTS, TS, and TD signals from a fanout unit and two processor interfaces. The selector unit 1810 includes a 1: 8 demultiplexer 1841 which transmits the CTS signal to a selected one of the eight possible units, and the TC and TD signals transmitted by the multiplexers 1832 and 1833 to the conductors 1851. And two buffers 1842 and 1843, each receiving via 1852, and transmitting this received signal to the eight units as RC and RD signals. These signals are transmitted between packet fanout units 1900-0 through 1900-5 and selector unit 1810 via bus 1899. 10 and 11, the conductors of the bus 1899 associated with the packet fanout unit 1900-0 are designated RTS0, TC0, TD0, CTS0, RC0, and RD0. Similarly, conductors of bus 1899 associated with packet fanout unit 1990-5 are designated RTS5, TC5, CTS5, RC5, and RD5. The selection by the multiplexers 1831, 1832, 1833 and demultiplexer 1841 is defined by the three lower bits of the counter 1822 received via the bus 1897, by the counter 1822. The seven bits transmitted are designated herein as selection signals. The signal transmitted by the multiplexer 1831 is coupled to the enable input terminal of the demultiplexer 1841 and the counter 1822 via two serially coupled synchronous flip-flops 1823 and 1824. The 16 MHz clock 1821 is used to arrange the counter 1822 and clock the flip-flops 1823, 1824.

Flip-flops 1823 and 1824 are included such that the oscillation that occurs when a signal is received at the enable input terminal at the same time as the transition occurs in the clock signal transmitted by the clock 1821 does not occur in the counter 1822. When the counter 1822 is in the count (0000000), for example, an RTS signal of logic 0 sent by the protocol regulator 1700-0 is multiplexer 1931, conductor RTS0 of the bus 1899, multiplexer 1831. And flip-flops 1823 and 1824 to the counter 1822 and demultiplexer 1841. In response to the RTS signal at logic 0, the counter 1822 stops counting. The demultiplexer 1841 transmits a logic 0 signal as a CTS signal to the protocol coordinator 17000-0 via the conductor CTS0 / of the bus 1899 and the demultiplexer 1941. In response, the protocol store 1702-0 begins transmitting the bits of the stored packet and the bits associated with them as TD and TC signals, respectively. The TD signal is transmitted to buffer 1843 via multiplexer 1933, conductor TD0 of bus 1899, multiplexer 1833, and conductor 1852, from which the signal is a total of 96 protocols as an RD signal. Sent to the regulator and two processor interfaces. The TC signal is transmitted to buffer 1842 via multiplexer 1932, conductor TC0 of bus 1899, multiplexer 1832, and conductor 1801, from which the signal is a RC signal as a total of 96 protocols. Sent to the regulator and two processor interfaces. Conductor 1852 represents a shared communication line of switching module 1000, via which the entire packet to and from user terminals such as 1001 and 1002 served by switch module 1000 and from this user terminal. Is sent. Once protocol coordinator 91700-0 has completed sending the packet, the RTS signal of logic 0 is removed, and in response to this removal, the CTS signal of logic 0 is removed, and counter 1822 is a logic indicating that the packet is ready for transmission. Counting resumes until it reaches another transmitter with an RTS signal of zero.

The selector unit 1810 includes a timeout counter (not shown), whereby the selection order starts again if the value of logic 0 is not removed within the predetermined time. The order executed by the packet interconnector 1800 is as follows. First, one protocol coordinator associated with each of the packet fanout units 1900-0, 1900-1, and 1900-2 is enabled to transmit, and the processor interface 1300 is enabled. One protocol coordinator associated with each of the packet fanout units 1900-3, 1900-4, and 1900-5 can then transmit. The replication processor interface can then transmit. During the next eight counts of the counter 1822, the second protocol coordinator and processor interface 1300 associated with each packet fanout unit 100-0, 1900-1, and 1900-2 in sequential order, respectively, With the second protocol coordinator associated with the packet fanout units 1900-3, 1900-4, and 1900-5, the replica processor interface is finally ready to transmit. The complete sequence includes 128 counters of the counter 1822, during which each protocol coordinator is ready to transmit once and each processor interface is enabled 16 times.

Control Fanout Unit (1500)

The control fanout unit 1500 (FIG. 6) is a control unit via a communication line 1027, ten UARTs 1511-0 to 1511-5, and 1512-0 to 1512-5. A processor 1510 in communication with 1017. Each UART 1511-0 through 1511-5 communicates with an associated UART of one of the data fanout units 1600-0 through 1600-5. For example, the UART 1511-0 communicates with the UART 1631 of the data fanout unit 1602-0 via a portion of the control bus 1051, allowing the processor 1510 to control the processor 1632. do. This control is performed by the bus 1202 from the digital line units 1101 and 1102 and the time slot exchange unit 1011 to the buses 1601-0 through 1601-15 to the protocol coordinators 1702-1 through 1700-15. ) And defining the time slot mapping between the bus 1205. Each UART 1512-0 through 1512-5 communicates with an associated UART in one of the packet fanout units 1900-0 through 1900-5. UART 1512-0 communicates with UART 1921 of packet fanout unit 1900-0 via a portion of control bus 1502 to allow processor 1510 to control processor 1922. This control includes the definition of which of the protocol coordinators 1700-1 through 1700-15 is designated to operate and which of the duplicate communication controllers is designated as active in each protocol coordinator.

Circuit switch

A method for establishing a circuit switched call is that message signaling is used between the user terminal and the switching system, and a given user terminal can simultaneously activate two circuit switched calls to different subscribers using two B channels. It differs from the method already described with respect to FIG. Message signaling is performed in the switching module 1000 by sending signaling packets from the user D terminal to the associated protocol coordinator and switching such packets to the processor interface 1300 via the packet interconnector 1800. The signaling information is read from the processor interface 1300 by the control unit 1017. Control information from the control unit 1017 is sent in the signaling packet by the processor interface 1300 to the given protocol coordinator via the packet interconnector 1800 and to one of its associated user D channels. For example, a call between user terminal 1001 and subscriber set 23 may signal a message in signaling module 1000 between D channel of user terminal 1001 and control unit 1017 at one end of the call. And at the other end of the call involves the usual in-band signaling in the switch module 501 between the subscriber set 23 and the control unit 17.

14 is a time sequence diagram illustrating the flow of messages between user terminals 1001 and 4001 and the switching system to establish a circuit switched call from user terminal 1001 to user terminal 4001. Initially, user terminal 1001 sends a SETUP message to the switching system indicating a request to complete some form of call to user terminal 1401. This SETUP message includes the telephone number of user terminal 4001 and which of the two B channels of user terminal 1001 is to be used. The switching system returns a SETUP ACK message confirming receipt of the SETUP message to the user terminal 1001, and then sends a SETUP message indicating the operation of the incoming call to the user terminal 4001. This SETUP message is sent to the user terminal 4001 after the switching system routes this call. This message includes the format of the call and the B channel of the user terminal 4001 selected by the switching system for this call. User terminal 4001 confirms the arrival of the SETUP message and returns an ALERTING message to the switching system that transmits call progress information equivalent to an audible ring tone. This switching system sends this ALERTING message to the user terminal 1001. When a user answers an incoming call at user terminal 4001, user terminal 4001 responds to a CONNECT message that forms a circuit switched communication channel from user terminal 1001 to the selected B channel of user terminal 4001. Send to the switching system. The switching system notifies the user terminals 1001 and 4001 that the call has been established by sending the CONNECT message to the user terminal 1001 and returning the CONNECT ACK message to the user terminal 4001. Subscribers can now communicate.

User terminal 1001 or user terminal 4001 may initiate disconnection of the call by sending a DISCONNECT message to the switching system. The switching system disconnects the B channel of the call, idles the call-related data, sends a DISCONNECT message to another user terminal, which returns a DISCONNECT ACK message confirming the successful completion of the disconnection procedure. .

In-module packet switch type call

The following is an example illustrating the setup and removal of an intramodule packet switched call between user terminals 1001 and 1002.

The necessary communication is indicated in FIG. 15 by a line terminated by an arrow head indicating its direction by the relevant letters A to M. To initiate the call, user terminal 1001 sends a call request packet A to its associated protocol coordinator 17000-0 on logical channel LCN1. The protocol coordinator 1700-0 processes a call request packet that includes a task of verifying that the logical channel number LCN2 of the user terminal 1001 is currently idle. The protocol coordinator 1700-0 selects an internal logical channel number (ILCN), e.g., ILCN3, associated with the call and used by the destination protocol coordinator in transmitting the packet to the protocol coordinator 1700-0. At this point, the protocol coordinator 1700-0 stores an entry in a routing table that maps ILCN3 of the user terminal 1001 to ILCN2. This entry is the top entry in the protocol coordinator 1700-0 routing table shown in FIG. 17. Underlining ILCN3 in the entry indicates that protocol coordinator 1700-0 selected ILCN3.

The protocol coordinator 1700-0 then sends a packet origination request B to the processor interface 1300 via the packet interconnector 1800. The packet origination request defines the originating user terminal 1001, the called telephone number, and ILCN3 selected by the protocol coordinator 17000-0 for the call. The packet origination request is read from the processor interface 1300 by the control unit 1017 (C). The control unit 1017 inserts information on the packet origination request into the control message D, and inserts the control message into the scheduled control channel 55 of the time slot exchange unit 1011 and the time multiplex switch 10. Via the control distribution unit 31 to the central controller 30. The central controller 30 translates the called telephone number defining the user terminal 1002 in this embodiment. The central controller 30 connects the called user terminal to the control unit 1017 via the control distribution unit 31, the time multiplexed switch 10, the control channel 55 and the time slot exchange unit 1011. A packet termination request (E) specifying 1002) is transmitted. The control unit 1017 maps the called user terminal 1002 to an associated protocol coordinator, e.g., 1700-95, both of which are currently in service. Verify The control unit 1017 sends the packet termination request F to the processor interface 1300. Based on the information defining the destination protocol coordinator 1700-95, the processor interface 1300 sends a packet termination request (G) to the protocol coordinator 1700-95 via the packet interconnector 1800. . In response, protocol coordinator 1700-95 selects an internal logical channel number, for example ILCN8, which is associated with the call. The protocol coordinator 1700-95 stores an entry in a routing table (FIG. 17) that maps ILCN8 of the user terminal to ILCN2.

The protocol coordinator 1700-95 then transmits a packet line setup message H containing information defining both ILCN3 and ILCN8 to the protocol coordinator 1700-0 via the packet interconnector 1800. In response, protocol coordinator 1700-0 stores a second entry in the routing table (FIG. 17) mapping LCN2 of user terminal 1001 to ILCN8 and protocol coordinator 1700-95.

At this time, the protocol coordinator 1700-0 transmits a packet setup completion message I to the protocol coordinator 1700-95 via the packet interconnector 1800. In response, protocol coordinator 1700-95 stores a second entry in a routing table (FIG. 17) that maps to LCN2 and LCN3 and protocol coordinator 17000-0 of user terminal 1002. At this point, the protocol coordinator 170005 transmits the incoming call packet J to the user terminal 1002. User terminal 1002 returns a call allowed packet (K) to protocol coordinator 1700-95, in response to which protocol coordinator sends a packet line connection indication (L) via packet interconnect 1800. Transmit to regulator 1700-0. Finally, the protocol coordinator 1700-0 transmits the call connection packet M to the user terminal 1001, and a packet switched communication channel between the user terminal 1001 and 1002 has been established.

During the call period, routing table entries stored in protocol coordinator 1702-0 and 1700-95 are used to switch data packets between user terminal 1001 and 1002 (FIG. 17). Data packets received from LCN2 of user terminal 1001 by protocol coordinator 1700-0 are transmitted to protocol coordinator 1700-95 via packet interconnector 1800 using ILCN8. Data packets received by the protocol coordinator 1700-95 from the packet interconnector 1800 at ILCN8 are transmitted to the user terminal 1002 at LCN2. In the other direction, the data packet received by the protocol coordinator 1700-95 from LCN2 of the user terminal 1002 is received by the protocol coordinator 1700-0 from the packet interconnector 1800 using ILCN3. Is sent to the user terminal 1001 at LCN2.

The sequence of messages needed to disconnect the call is shown in FIG. The user terminal 1001 sends an erase request packet A to the protocol coordinator 17000-0. In response, protocol coordinator 1700-0 marks LCN2 of user terminal 1001 as idle and sends a clear message B to protocol coordinator 1700-95 via packet interconnector 1800. . The protocol coordinator 1700-0 sends an erase confirmation packet C to the user terminal 1001. In response to the erase message B, the protocol coordinator 1700-95 transmits an erase display packet D to the user terminal 1002. The user terminal 1002 responds by returning the erase confirmation packet E to the protocol coordinator 1700-95. In response, protocol coordinator 1700-95 marks LCN2 and ILCN8 at the user terminal as idle. The protocol coordinator 1700-95 sends an acknowledgment message E to the protocol coordinator 1700-0 via the packet interconnector 1800. In response, protocol coordinator 17000-0 marks ILCN3 as idle, and the disconnection sequence is completed. Note that in setting up and removing the packet switched call, only the central controller 30 and the control unit 1017 are involved in the initial routing of the call.

Example of packet-switched switching between modules

Setting up an intermodule packet switched call from user terminal 1001 to user terminal 4001 includes two protocol coordinators 1700-0, 1700-1 in packet switch unit 1400, and packet switching unit 4400. My two protocol coordinators (4700-0, 4700-1). To initiate the call, user terminal 1001 sends a call request packet on logical channel LCN1 to its associated protocol coordinator 1700-0. The protocol coordinator 1702-0 processes a call request packet that includes a task of verifying that logical channel number LCN2 of user terminal 1001 is currently idle. The protocol coordinator 1700-0 is associated with a call and is used by the inter-module protocol coordinator 1700-1 in sending packets to the protocol coordinator 1700-1, eg, ILCN9. Select. The protocol coordinator 1700-0 stores an entry in a routing table that maps ILCN9 to ILN2 in user terminal 1001 (FIG. 18). The protocol coordinator 1700-0 then sends a packet origination request to the processor interface 1300 via the packet interconnector 1800. The packet origination request defines the ILCN9 selected for calling by the originating user terminal 1001, the called telephone number, and the protocol coordinator 17000-0. The packet origination request is read from the processor interface 1300 by the control unit 1017. The control unit 1017 inserts the packet origination request information into the control message, and transmits the control message via the time slot exchange unit 1011, the predetermined control channel 55 of the time multiplex switch 10, and the control distribution unit. It transmits to the central controller 30 via 31. The central controller 30 translates the called telephone number defining the user terminal 4001 in this embodiment. The central controller 30 controls the packet termination request defining the called user terminal 4001, the control separation unit 31, the control channel 61 of the time multiplexed switch 10, and the time slot exchange unit 4011. It transmits to the control unit 4017 via.

The control unit 4017 associates the called user terminal 4001 with an associated protocol coordinator, for example 4700-0, and verifies that both the protocol coordinator 4700-0 and the user terminal 4001 are currently in service. do. At this time, the control unit 4017 sends a packet termination request to the processor interface 4300. Based on the information defining the destination protocol coordinator 4704-0, the processor interface 4300 sends a packet termination request to the protocol coordinator 4704-0 via the packet interconnector 4800. The protocol coordinator 4700-0 determines, based on the parameters in the packet termination request, that the call is an intermodule call. The protocol coordinator 4700-0 then exchanges control messages with the intermodule protocol coordinator to select a packet switched channel between them. Subsequently, the protocol coordinator 4700-1 exchanges a control message with the intermodule protocol coordinator 1700-1 at the switching module 1000, and forms a channel between the protocol coordinators between the two modules. Communication between protocol coordinator 4700-1 and 1700-1 is time multiplexed by bus 4205 between four scheduled channels, time slot exchange unit 4011, input / output ports P61 and P55. Transmit to protocol coordinator 1700-1 via channels CH109 through CH112 time slot exchange unit 1011 of switch 10 and four predetermined channels of bus 1205. The predetermined channel between protocol coordinator 4700-1 and 1700-1 may be used to transmit packets at 256 Kbps, 64 Kbps, or various other rates. Finally, protocol coordinator 1700-1 exchanges the control message with protocol coordinator 1700-0 to complete the packet switched channel from protocol coordinator 4704-0 to protocol coordinator 1700-0. The additional steps required to make a call are the same as in the in-module call described above.

Exemplary routing table entries in the various protocol coordinators 1700-0, 1700-1, 4700-1, and 470-00-0 for the intermodule calls are shown in FIG. The logical channel number used on the intermodule channel is referred to as the intermodule logical channel number (IMLCN). As in the case of in-module calls, each of the originating protocol coordinator and the terminating protocol coordinator select the ILCN used to determine which of the packets received from the packet interconnector is associated with a particular call. Each intermodule protocol coordinator selects both the ILCN and IMLCN required to associate packets received from the packet interconnector and from the intermodule channel, respectively. In accordance with the embodiment shown in FIG. 18, once a call has been made, data packets received from the LCN2 of the user terminal 1001 by the protocol coordinator 1700-0 are transmitted via the packet interconnector 1800 at ILCN4. Is sent to the protocol coordinator 1700-1. Packets received by the protocol coordinator 1700-1 from the packet interconnector 1800 at ILCN4 are transmitted to the protocol coordinator 4700-1 at IMLCN8 in an intermodule channel. Packets received by the protocol coordinator 4700-1 from the intermodule channel to IMLCN8 are transmitted to the protocol coordinator 4704-0 via the packet interconnector 4800 at ILCN3. Finally, packets received at ILCN3 from packet interconnector 4800 by protocol coordinator 4704-0 are transmitted to user terminal 4001 at LCN2. The data packet received by the protocol coordinator 4704-0 from LCN2 of the user terminal 4001 in the reverse direction is transmitted to the protocol coordinator 4700-1 at ILCN14 via the packet interconnector 4800. Packets received at ILCN144 from packet interconnect 4800 by protocol coordinator 4700-1 are transmitted to protocol coordinator 1700-1 at IMLCN3 on the intermodule channel. Packets received at IMLCN3 by protocol coordinator 1700-1 from an intermodule channel are transmitted to protocol coordinator 1700-0 via packet interconnector 1800 in ILCN9. To complete the connection, the packet received by the protocol coordinator 1700-0 at INCN9 from the packet interconnector 1800 is transmitted to the user terminal 1001 at LCN2.

In this embodiment, the switching modules 1000, 2000, 3000, and 4000 are directly coupled or interconnected for packet traffic in a mesh distribution. Each pair of switching modules utilizes four time multiplexed switch 10 channels for packet communication between the modules. For example, a packet may be connected to the switching module 1000 using the time multiplexed switch 10 channels CH 101 to CH 104 (as indicated in FIG. 19 by numbers on the line between modules 1000 and 2000). Is carried between 2000. Twelve time multiplexed switch 10 channels from each switching module are used for inter-module packet call volume.

Operator service

One or more switching modules of the system, for example module 1000, are moved in connection with the telephone operator location terminal to provide attendant services and guidance services, such as number guidance and telephone charges, to be served by other switching modules of the system. It can be provided by. For example, if the switching module 1000 is used to provide such an operator service and the user terminals connected to the module 1000, such as terminals 1001 and 1002, are operator location terminals, then the digital conference circuitry may be used. It is connected to the time slot switching unit 1011 and relays the available operator location terminal and the subscriber set or user terminal connected directly to another switching module or connected via a digital or analog trunk from another switching system. For example, the originating subscriber or subscriber set 23 is connected to the digital conference circuit via the line unit 19, the time slot exchange unit 11, the time multiplex switch 10 and the time slot exchange unit 1011. . The called subscriber or user terminal 4001 is connected to the digital conference circuit via the digital line unit 4101, the time slot exchange unit 4011, the time multiplex switch 10 and the time slot exchange unit 1011. The operator location terminal, or user terminal 1001, is connected to the digital conference circuit via the digital line unit 1101 and the time slot exchange unit 1011 to relay the caller and the called party and the operator. Messages communicated between the terminal 1001 and the control unit 1017 include a keystroke message sent by the terminal 1001 in response to the pressing of various function keys on the terminal 1001 used in providing the operator service. do.

First Alternative Embodiment

In a first alternative embodiment, the switching modules 1000, 2000, 3000, and 4000 are interconnected for packet traffic in the shaping phase of FIG. 20. Each of the switching modules 1000, 2000, and 3000 performs packet switching within the module, and four time multiplexed switches 10 to switch packets to and from the switching module 4000. ) Channel. The switching module 4000 also performs intra-module packet switching, but uses four time multiplexed switch 10 channels for each of the switching modules 1000, 2000 and 3000 to carry packets. , Packet switching is performed between the modules 1000, 2000, 3000, and 4000 for inter-module packet call. As another example, the switching module 4000 may be used only for packet switching between modules. In some situations, a system that requires many of these modules, the circuit switching data of the time multiplexed switching 10 is used more effectively than the similar realization of the meshed phase of FIG. 19 to realize the shaping phase of FIG. However, using the shaping phase may increase the overall packet transmission delay.

Second Alternative Embodiment

In a second alternative embodiment, a packet switching ring network 5000 is added to the system of FIGS. 1-3 to switch both intermodule packet calls and intramodule packet calls. Such networks are known in the art. FIG. 21 shows only the additional part and changes to the system of FIGS. 1 to 3 for this second alternative embodiment. Packet switching units 1400, 2400, 3400 and 44000 represent packet switching units in the switching modules 1000, 2000, 3000 and 4000 of FIGS. . The central controller 30 has a second communication link 5005 (FIG. 21) used for control of the ring network 5000 in addition to the communication link 32 (FIG. 3). Each packet switching unit is connected to a ring network 5000 by a plurality of digital communication facilities 5002, ie by a 24-channel T1 carrier system. A given communications facility 5002 is connected to a ring network 5000 via a digital facility interface 5003 and to a given packet switching unit via a digital facility interface 5001. Each digital facility interface 5001 is connected to one of the data fanout units included in the packet switching unit via a 32-channel bidirectional data bus 5004. However, only 24 of the 32 bus 5004 channels are used. In the packet switching unit 1400, for example, each protocol coordinator is associated with one channel at one of the facilities 5002. The protocol coordinator responds to the signaling packet from the user terminal by switching such a packet to the control unit 1017 (FIG. 2), as above. However, the protocol coordinator responds to the data packet by sending the data packet to the channel of the associated facility 5002 at a rate of 64 Kbps. The ring network 5000 communicates with the central controller 30 to determine the appropriate channel of the facility 5002 and to transmit this data over the channel so that the data packet is received by the correct destination protocol coordinator to be switched to the destination user terminal. The packet is returned. The actual circuit is formed in the ring circuit 5000 between the inlet channel of the facility 5002 and thus the outlet channel.

It is to be understood that the above embodiments merely illustrate the principles of the invention, and that other embodiments may be modified by those skilled in the art without departing from the scope and spirit of the invention. For example, in the described embodiment, the user terminal accesses the switching system via a 4-wire CCITT, T interface using 2B + D format (two 64 Kbps circuit switched B channels and one 16 Kbps packet switched D channel). However, other user access methods are also expected. For example, a user terminal may achieve access via a two-wire line (CCITT denoted U-interface) using the same 2B + D format. A digital transmission facility, such as a T1 carrier system, may use 23B + D format (23 Digital loop-carrier remote terminal or remote switching entity, with multiple 2B + D formats multiplexed in a T1 carrier system via a digital PBX or 64Kbps circuit switched B-channel and one 64Kbps packet-switched D-channel). In addition, in the above embodiment, the communication link between the user terminal and the protocol coordinator realizes a known HDLC link level protocol, many other link level protocols may be used. Furthermore, other protocols may be used to communicate with other user terminals. It is also understood that null can be used as a packet switched channel rather than a circuit switched channel, etc. If the user B channel is used as a packet switched channel in the system of Figs. 4400 or directly via a line-switched channel of the time slot exchange unit 1011. Further, a system as shown in FIGS. 1 to 3 may only include a line unit. It is also understood that analog or digital trunk units may be included that connect with trunks from other switching systems.

Claims (7)

A time slot exchange, each associated with a plurality of user terminals, capable of connecting the associated plurality of user terminals 1001, 1002 via access lines 1003, 1004 to provide circuit switched communication channels between the user terminals; A plurality of switching modules (1000,4000) comprising a unit (1011) and a time multiplexed switch (10) for interconnecting the time slot exchange units of said switching module for inter-module circuit switched communication. In a switching system, each switching module (1000,4000) is the time multiplier to provide a packet switched communication channel between the associated user terminals and between the associated user terminal and the time multiplexed switch (10). It further comprises a packet switch unit 1400 that can be connected to the flex switch 10, wherein the time multiplex switch 10 The packet switching unit of the switching module is interconnected for inter-module packet switched communication, wherein the packet switching unit 1400 is capable of connecting one predetermined protocol regulator of the protocol regulator to the time multiplexed switch 10; Some protocol coordinator 1700 connects to the associated user terminal and provides a packet switched communication channel between the associated user terminals and between the associated user terminal and a predetermined protocol coordinator of the switching module. Packet interconnect 1800 for interconnecting protocol coordinators, wherein the time multiplexed switch 10 establishes a circuit switched communication channel between user terminals associated with different modules of the switching module 1000. Time slot of each switch module 1000 to provide Interconnect the switch exchange unit 1011, interconnect the predetermined protocol coordinator of the switching module to provide a packet switched communication channel between user terminals associated with different modules of the switching module 1000, and the packet interconnector ( 1800 includes a selector unit (1810) for enabling each said protocol coordinator to transmit information to said packet interconnector in order. 2. The packet switching unit 1400 of claim 1, wherein the packet switching unit 1400 is connected to the time slot exchange unit 1011 via a bus 1205, and the time slot exchange unit 1011 is time multiplied with the bus 1205. Line / packet integrated switching system characterized in that it provides a predetermined channel (P56, P55) between the flex switch (10). 2. The method of claim 1, wherein the time multiplexed switching and the time slot exchange unit connect a predetermined protocol coordinator 1700-1 of each switching module of the switching modules to a predetermined protocol coordinator of each other module of the switching modules. Featuring integrated line / packet switching system. 2. A circuit according to claim 1, wherein the time multiplex switch and the time slot exchange unit connect a predetermined protocol coordinator 4700-1 of a given module of the switching module to a predetermined protocol coordinator of another module of the switching module. / Packet integrated switching system. 2. The circuit / packet integrated switching system of claim 1, wherein said time slot exchange unit (1011) provides a communication channel between a predetermined protocol coordinator of said switching module and said time multiplexed switch (10). 2. The apparatus of claim 1, wherein the switching module further includes a control unit 1017 for controlling the formation of a circuit switched communication channel by the time slot exchange unit 1011, wherein the packet switching unit 1400 is each Connect each of the protocol regulators to a protocol controller connected to the control unit to provide a signaling channel between the associated user terminal and the control unit of which each of the protocol controllers is connected to a signaling received from the associated user terminal. And a communication controller 1443 for transmitting a packet to the control unit 1017 and for transmitting a data packet received from the relevant user terminal to any of the protocol coordinators. . 2. The apparatus of claim 1, wherein each protocol regulator transmits a request signal, and the selector unit 1810 generates a clock 1821 for generating a clock signal and a selection signal defining one of the protocol regulators, respectively. A counter 1822 responsive to a clock signal, and responding to a given signal of a selection signal to send to the counter a request signal received from one of the protocol regulators defined by the given selection signal such that no further selection signal can occur. A multiplexer 1831 and a demultiplexer 1841 in response to the given selection signal and in response to the request signal received from the multiplexer to send a clear signal to one of the protocol regulators defined by the given selection signal. Wherein each said protocol regulator is cloned from said demultiplexer. And a packet to the packet interconnect in response to the rear signal.

Images