KR0166197B1 - A circuit exchange for switching atm cells - Google Patents

Abstract

The present invention relates to a circuit switch having an ATM switching function, comprising: a broadband access matching unit (10) for using STM-1 in a synchronous transmission method; A medium speed access matching unit 20 which multiplexes and demultiplexes the pseudo-synchronous digital transmission data DSIE and DS3 and connects them by ATM; A broadband trunk line matching unit 40 for connecting to another network with STM-1; An ATM interworking unit 50 for interfacing the ATM switch with the line switch; ATM switch 30 for exchanging ATM cells input to the intermediate speed access matching unit 20, the broadband access matching unit 10, the broadband relay line matching unit 40, and the ATM interworking unit 50 to 16 × 16. ); And an ATM access processor 60 that controls ATM switching according to a synchronous clock and a predetermined sequence inputted from the ATM network synchronization unit 70, so that ATM functions can be accommodated in a part of a circuit switcher, thereby attaining a low cost. There is an effect that can provide a service.

Description

Circuit Switch with ATM Switching

1 is a block diagram showing an ATM switching device implemented in a circuit switch in accordance with the present invention.

* Explanation of symbols for main parts of the drawings

10: Broadband Access Matching Unit (BAI)

11, 41: Broadband Subscriber Physical Layer Unit (BSPLU)

12, 42: Broadband subscriber ATM layer unit (BSALU)

13, 43: used parameter control unit (UPCU)

20: Medium Speed Access Matching Unit (MAI)

21: low speed interface unit 22: medium speed interface unit

23: medium speed multiplexing / demultiplexing unit 30: 16 × 16 ATM switch

40: broadband relay line matching unit 50: ATM interworking and data link

51: interworking processor unit 52: ATM cell multiplexing / demultiplexing unit

53 cell disassembly / assembly unit 54 local data link matching unit

55: interworking clock distribution unit 60: ATM access switching processor

61: wideband processor ATM layer unit 62: AAL signal processing unit

63: ATM switching control processor unit 70: ATM network synchronization unit

The present invention relates to an ATM function of a digital electronic switching system, and more particularly, to provide an ATM switching service in a circuit switching switch such as a conventional TDX-10. A circuit switch with a function is provided.

In recent years, with the rapid growth of the multimedia field, a communication network for transmitting a video signal digitally has been required, and a broadband-integrated services digital network (B-ISDN) capable of transmitting broadband has emerged. With the advent of broadband ISDN, it is possible to meet various service needs of users, and in particular, it is possible to transmit moving images, thereby becoming a foundation for realizing the dream of the future information society.

This ATM communication is based on the ATM cell, the user's long message is divided into ATM cells and transmitted, and the received ATM cells are reassembled into a single message and delivered to the upper user.

That is, the ATM cell is divided into a 5-byte header (H: Header) section and a 48-byte user information section, and the 5-byte header includes a header structure and a network node interface (UNI: User Network Interface). It is divided into header structure in NNI: Network Node Interface (NNI), and header structure in user network interface (UNI) is 4-bit generic flow control (GFC) and 4-bit virtual path identification number of 1 byte. (VPI: Virtual Path Identifier), and the second byte consists of a 4-bit Virtual Path Identifier (VPI) and a 4-bit Virtual Channel Identifier (VCI), and the third byte is 8 bits. Fourth byte consists of a 4-bit virtual channel identification number (VCI), a 3-bit payload type (PT) and a 1-bit cell abandonment ranking (CLP: Cell). Loss Priority, and the fifth byte is an 8-bit header error control (HEC). Eojinda.

Here, the last bit of the 3-bit payload type (PL) is a user bit (AUU: ATM-USER to ATM-USER), which is useful in the AAL 5 protocol. When the first bit is 1, the operation management load type (OAM) is used. : Operations, Administration, and Management) and its meaning is as follows.

Also, when looking at the header structure of the network node interface (NNI), except that the general flow control (GFC) in the first byte of the user network interface (UNI) described above is used as the virtual path identification number (VPI). It can be seen that the same as the header structure of the network interface (NNI).

This ATM communication method has a hierarchical structure as shown in Table 2 below and has standardized standards for each layer.

As shown in Table 2, the ATM communication method includes a physical layer, an ATM layer, an ATM adaptation layer (AAL). Like the upper protocol layer, it is divided into vertical structures, and the AAL layer is divided into a segmentation and reassembly sublayer (SAR) and a convergence (CS) sublayer, and the physical layer is a physical medium (PM). ) And sub-layer of transmission convergence (TC).

In addition, according to the service of the user, that is, the characteristics of the source in the ATM communication method can be separated as shown in Table 3.

As shown in Table 3, the types of services in B-ISDN are classified into Classes A to D according to the nature of the source. The Class A services are real-time, identity bit rate, and connectivity services, and the Class B service is real-time, It is a variable bit rate, connectivity service, class C service is a non-real time variable bit rate, a non-connected service, class D service is a non-real time, variable bit rate, a non-connected service. Representative examples of such services include identity rate video signals, variable rate video signals, connectivity data transmission, and connectionless data transmission.

On the other hand, AAL protocols corresponding to the above services are divided into AAL1 to AAL5 as shown in Table 4, but in the past, AAL1 to AAL4 are classified. However, AAL3 and AAL4 have similarities and are combined into AAL3 / 4. AAL5 has been proposed to reduce the overhead.

As shown in Table 4, the AAL layer is divided horizontally as AAL1, AAL2, AAL3 / 4, AAL5 in order to efficiently process the service according to the type of service. It is suitable for high-speed data communication by reducing overhead of AAL3 / 4 layer that transmits data of class and class D service, and transparently delivers service data unit (U-SDU) from service user. The ATM cell is detected and the variable-length data received from the convergence layer layer CS, which performs the function of identifying and buffering the information, is divided and the ATM cell is created and delivered to the ATM layer. The ATM cell is received from the cell and reassembled into subdivided and recombined sublayers (SARs) that recover the converged sublayer protocol data unit (CS-Protocol Data Unit). In addition, the Convergence (CS) sublayer includes a Common Part Convergence Sublayer (CPCS) that performs functions common to the connectivity and connectionless services, and a service specific convergence layer layer (CPCS) for providing a specific AAL user service. SSCS: Service Spectific Convergence Layer.

However, the ATM switch that exchanges ATM cells in order to provide a service according to the ATM method is conventionally divided into a circuit switch that performs circuit switching and thus exists as an independent switch. In order to provide an additional ATM switch, a huge cost has been increased.

In order to solve the above problems, the present invention provides a circuit switch equipped with an ATM switching function, which is capable of simultaneously supporting circuit switching and ATM access by accommodating an ATM switching function in a part of the circuit switch. have.

In order to achieve the above object, the apparatus of the present invention, in the digital electronic switch for receiving a predetermined subscriber and the trunk circuit switching, multiplexing and demultiplexing the digital transmission data DSIE and DS3 of the synchronous synchronization method ATM A medium speed access matching unit for matching in a manner; A broadband access matching unit for accommodating synchronous transmission STM-1; A broadband trunk line matching unit for connecting to another network with STM-1; An ATM interworking unit for interfacing ATM switching with a return switch; ATM switching for exchanging ATM cells input to the intermediate speed access matching unit, the broadband access matching unit, the broadband relay line matching unit, and the ATM interworking unit by 16 × 16; And an ATM access processor for controlling ATM switching according to a synchronous clock and a predetermined sequence input from the ATM network synchronization unit.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

ATM switching implemented in the circuit switch in accordance with the present invention is a broadband access matching unit (BAI: 10), medium speed access matching unit (MAI: 20), ATM switching (ASW: 30), as shown in FIG. Broadband trunk line matching unit (BAI: 40), ATM interworking unit (AIDL: 50), ATM access switching processor (AASP: 60), ATM network synchronization unit (ANES: 70).

The broadband access matching unit BAI: 10 includes a broadband subscriber physical layer unit (BSPLU) 11 which receives an STM-1 signal from a subscriber and transmits a physical layer processing and a preferred maintenance signal to a control system; A broadband access ATM layer unit (BSALU: 12) using a parameter control unit (UPCU: 13), the medium speed access matching unit (MAI: 20) comprising: a low speed interface unit (LRIU: 21) for matching DSIE signals; A medium speed interface unit (MRIU: 22) for matching DS3 signals; It consists of a medium speed multiplexing demultiplexing unit (MMDXU: 23).

Broadband trunk line matching unit (BAI: 40) Broadband subscriber physical layer unit (BSPLU: 41) matching STM-1 class 155.520 Mbps speed; Broadband subscriber ATM layer unit (BSACU: 42); A usage parameter control unit (UPCU) 43, and the ATM interworking unit (AIDL) 50 includes an interworking processor unit (IWPU) 51; An ATM cell multiplexing / demultiplexing unit (AMDU: 52); Cell disassembly / assembly unit (CADU: 53); Local data link matching (LDIU: 54); An interworking clock distribution unit (ICDU) 55, and the ATM access processor unit AASP 60 includes a broadband processor ATM layer unit BPALU 61; AAL signal processing unit (AASHU: 62); It consists of an ATM Switching Control Processor Unit (AACPU: 63).

That is, in order to access broadband subscribers, low-speed interface unit (LRIU: 21) that matches DSIE 2.048Mbps speed, medium-speed interface unit (MRIU: 22) that matches DS3-class 45Mbps speed, and STM-1 class 155.520Mbps are used for subscriber access. There is a Broadband Subscriber Physical Layer Unit (BSPLU: 11) that matches speed, and among them, the Broadband Subscriber Physical Layer Unit (11) is a terminal having a UNI protocol with B-ISDN subscriber matching, and functions of the physical layer and the ATM layer. Do this.

In addition, the broadband relay line matching unit 40 includes a BSPLU 41 that matches the STM-1 class, 155.520 Mbps speed, and performs the functions of the physical layer and the ATM layer as an end device having an NNI protocol for B-ISDN relay line matching. .

As described above, the matching of the ATM switching system is performed by the B-ISDN, and the matching of the UNI protocol and the B-ISDN network to the user side is performed using the NNI protocol.

Data of DSIE and DS3-class subscribers of the broadband subscribers are multiplexed and demultiplexed at the base rate of 155.520 Mbps before the physical layer connection and the ATM layer processing are performed at the LRIU 21 and the MRIU 22, and then exchanged at the ATM switching. . The multiplexed data is broadband to the AASHU 62 of the AASP 60, which is an ATM switching processor that performs the functions of the AAL layer, to support the next wideband signal cell processing and internal message communication through the ATM switching that performs the cell switching function. It passes through the processor ATM layer unit 61. The AASHU 62 transmits and receives ATM cells to perform decomposition and combining functions on signal information and internal messages.

All inter-processor communications (IPUs) and internal messages for maintenance and operation performed during call setup and user information transfer are identified by a separate flag in the cell header, and are routed in advance by the switching network 30. Are interchanged.

Next, the ATM switching operation according to the present invention will be described in terms of a broadband subscriber reception processing procedure, a broadband subscriber transmission processing procedure, and an ATM switched call setup procedure.

[Broadband subscriber reception process]

When the broadband subscriber matching unit 10 receives the ATM cell, the procedure is as follows.

The broadband subscriber matching unit 10 receiving the cell mapped to the STM-1 by converting the received optical signal into an electrical signal performs an error detection while performing a cell synchronization function of determining the start point of the cell in the bit stream using the HEC mechanism. And perform a correction function. The STM-1 disassembler extracts the information data contained in the virtual container (VC) of the STM-1 frame.

At this time, when the starting point of the cell is determined by interpreting the received pointer, a header conversion function is performed by the I / O conversion table stored in the memory to convert the internal cell structure to set up the call. The I / O conversion table contains information such as flags that distinguish between the outer set (user cell) and the inner message cell (IPU cell), a new header for the outgoing cell, routing information (the physical address of the switch), and a cell counter for charging. Have In case of accessing low speed and medium speed subscribers, the medium speed multiplexing and demultiplexing unit performs multiplexing by STM-1 synchronous method.

[Broadband subscriber transmission process]

When the broadband subscriber matching unit 10 transmits an ATM cell, it has the following processing procedure.

Change the inner cell structure to the outer cell structure and update the HEC according to the cell header change. In addition, the STM-1 assembler performs an STM-1 assembling function to fill an ATM cell in the VC-4, and then outputs the converted STM-1 assembler to convert an electrical signal into an optical signal in an unshown optical transceiver.

[Calling Procedure of ATM Switch]

On the other hand, the call setup procedure of ATM switch is as follows.

First, the physical layer connection is performed at the LRIU 21, the MRIU 22, and the BSPLU 11 of the broadband subscriber matching unit (BAI: 10) and the intermediate speed subscriber matching unit (MAI: 20). The subscriber's signaling information is delivered to AASHU 62 via a semi-permanent internal signaling channel (ie, BSALU-MMDXU-ASW-BPALU). At this time, the BAPLU 11 of the calling party allocates the VPI to the user, performs a number translation from the called subscriber number included in the subscriber signal information, and transmits the called subscriber number to the called ATM.

The destination ASM is assigned an output VPI and selects an optimal information transfer path (ie, the physical address of the switch) in consideration of the status of the links accommodated in the destination ASM. The called party sends the switch's physical address to the calling party, and the calling party ASM stores the physical address of the switch from the called party in the input header table, and the called party ASM enters the VPI into the output header translation table. Call setup is made between called subscribers. In the user information cell having the VPI, the physical address and control information of the switch are added to the cell header for self routing by the input header conversion table, and the new information is transmitted to the called subscriber after being changed to the new VPI by the output header conversion table. do.

Here, the broadband subscriber physical layer unit (BSPLU) 11 performs a function of transferring a physical layer processing function and a line maintenance signal between the subscriber and the BSALU 12 to the control system, and the BSALU 12 is connected to the BSPLU 11. After the physical layer is connected, the ATM cell is received and the ATM layer is processed, and then the data is transmitted to the switching processor block 60 through the ATM switching 30. In addition, the BSALU 12 performs a virtual path (VP) operation preservation function.

In the case of the LRIU 21 and the MRIU 22 of the intermediate subscriber matching unit 20, both the physical layer processing and the ATM layer processing are performed, and then the MMDXU 23 performs the multiplexing and demultiplexing functions, and the ATM switching 30 is performed. By transmitting the cell to the BPALU (61) to perform the ATM layer call processing function and operation preservation function.

After performing the ATM call processing function in the BPALU 61, a cell is transmitted to the AASHU 62 to perform AAL layer processing, where the decomposition and combining of the internal messages is performed. The AACPU 63, which is an ATM switching processor unit, performs a control function for all resources of the ATM switching ASS, and performs a matching function with the BPALU 61 to perform IPC through the ATM switching 30.

The AIDL 50 is located between the local circuit switching block (INS) and the ATM switch to perform AAL processing for user information and IAAL (IPC AAL) for IPC messages.

And the matching function with the INS for connection with the PSTN network is data link matching in the LDIU (54), PCM data and control data received via the optical link from the circuit switch is the cell data of STM-1 format in the CADU (53) Perform cell disassembly and assembly function of AAL1 to convert it to AMDU 52. The AMDU 52 multiplexes the received ATM cells and transmits them for cell switching in the ATM switching 20. These CADU (53), AMDU (5

2) is controlled by the IWPU 52, the IWPU 51 provides the IPU function with the AASP 60, and converts the IPC cell received in IAAL processing and ATM switching to IPC format for IPU transmission and reception. It plays a role.

That is, the CADU 53 provides a subhighway interface with SSL (which belongs to the INS block) and performs cell disassembly and cell assembly of AAL1 by PCM data, and the AMDU 52 multiplexes and demultiplexes an ATM cell. Function, matching function of ATM switch and circuit switch. The IWPU 51 controls the CAD 53 and the AMDU 52 and provides an IPC communication function with the AASP 60 through the global interface. In addition, IPC data received from the global bus is converted to IAAL, which is an ATM IPC format, by ATMP (???), and transmitted to the ATM switch 30 via the AMDU 52. On the contrary, the IPC cell received from the ATM exchanger is transmitted to ATMP (???) separated from the end user cell in AMDU (52), and the ASP (via the global bus) (Not shown).

As described above, the circuit switch according to the present invention provides an ATM function, so that various services can be integrated and provided, and in particular, the ATM function can be accommodated in a part of the circuit switch without using a separate ATM switching system. It is effective in providing ATM service at low cost.

Claims (4)

Claims [1] A digital electronic switch system for circuit switching by acquiring predetermined subscribers and trunks, comprising: a broadband access allocator (10) for accommodating synchronous transmission STM-1; A medium speed access matching unit 20 which multiplexes and demultiplexes the pseudo-synchronous digital transmission data DSIE and DS3 and connects them by ATM; A broadband trunk line matching unit 40 for connecting to another network with STM-1; An ATM interworking unit 50 for interfacing ATM switching with a line switch; ATM switching for exchanging ATM cells input to the intermediate speed access matching unit 20, the broadband access matching unit 10, the broadband relay line matching unit 40, and the ATM interworking unit 50 to 16 × 16. 30; And an ATM access processor (60) for controlling ATM switching according to a synchronous clock and a predetermined sequence input from the ATM network synchronization unit (70). 2. The broadband subscriber matching unit (10) according to claim 1, further comprising: a broadband subscriber physical layer unit (11) for performing physical layer processing for ATM mapped to STM-1; A usage parameter control unit 13 for controlling the usage parameter by the information received at the physical layer; A circuit switch having an ATM switching function, comprising: a broadband subscriber ATM layer unit (12) configured to perform ATM layer processing on ATM cells processed in the broadband subscriber physical layer under the control of the usage parameter control unit. . 2. The medium speed access matching unit (20) of claim 1, wherein the medium speed access matching unit (MAI: 20) comprises: a low speed interface unit (LRIU: 21) for matching a DSIE signal; A medium speed interface unit (MRIU: 22) for matching DS3 signals; A medium speed multiplexing / demultiplexing unit (MMDXU) for multiplexing the outputs of the low speed interface unit and the medium speed interface unit and outputting the same to the low speed interface unit and the medium speed interface unit by demultiplexing the data inputted from the ATM switching unit. A circuit switch with an ATM switching function, characterized in that consisting of 23). 2. The ATM system of claim 1, wherein the ATM interworking unit (AIDL) comprises: an interworking processor unit (IWPU) 51 for controlling corresponding boards and processing an IPU communication function to interface circuit switching and ATM switching; An ATM cell multiplexing / demultiplexing unit (AMDU) 52 for transmitting / receiving and multiplexing and demultiplexing ATM cells by ATM switching; A cell disassembly / assembly unit (CADU) 53 for disassembling and assembling the demultiplexed ATM cell; A local data link matching section (LDIU) 54 for matching data assembled with an ATM cell with link data on a circuit-switching side; A circuit switch with an ATM switching function, comprising: an interworking clock distribution unit (ICDU: 55) for providing a clock for interworking.