WO2010115328A1

WO2010115328A1 - Method and system for achieving interworking function service intercommunication between networks

Info

Publication number: WO2010115328A1
Application number: PCT/CN2009/073508
Authority: WO
Inventors: 娄方亮; 范更孟; 程鹏
Original assignee: 中兴通讯股份有限公司
Priority date: 2009-04-07
Filing date: 2009-08-25
Publication date: 2010-10-14
Also published as: CN101534571A; CN101534571B

Abstract

The present invention discloses a method and system for achieving network interworking function (IWF) service intercommunication between networks. The method includes: different network terminals send to each other network IWF service requests, and distribute and transmit network IWF parameters to their own respective wireless side protocol stack processing units and network IWF service protocol processing units via the H.248g signaling processing units on their respective media gateways; the different network terminals respectively establish wireless link layer protocol links and notify their respective network IWF service protocol processing units to establish the interworking links between the networks. The present invention enables interworking links between the IWF service protocol processing units of different network terminals, and achieves the objective of IWF service intercommunication between networks.

Description

TECHNICAL FIELD The present invention relates to the field of communications, and in particular, to a method and system for implementing IWF service interworking between networks in the field of mobile communications. BACKGROUND OF THE INVENTION A mobile communication network implements a conventional circuit type data service similar to a Public Switched Telephone Network (PSTN) through an Interworking Function (IWF) device. The IWF is a device that provides interworking between the mobile communication network and the PSTN network. It uses the mobile station (Mobile Termination, called the MT) and the modem on the IWF (MODEM) to provide the same user with the wired MODEM. Function to implement circuit data services, such as asynchronous data services, wireless fax services. 1 is a schematic diagram of an interconnected service model for performing IWF services by a code division multiple access (CDMA) 2000 terminal and a global system for mobile communication (GSM) terminal, as shown in FIG. As shown in Figure 1, the functional units of the IWF service of CDMA2000 include CDMA2000 terminals, Base Transceiver Station (BTS) / Base Station Controller (BSC), wireless access equipment, mobile Switching Center Emulation (MSE), media gateway. First, the CDMA2000 terminal initiates an IWF service request, and sends a request signaling to the MSCE through the BTS/BSC radio access device. The MSCE is transmitted to the media gateway through the XX39 interface. The media gateway assigns bearer circuits and IWF function resources according to the request instruction. Then, the IWF function unit of the CDMA2000 terminal and the media gateway performs media plane negotiation in the inband, and establishes a 7|c carrier protocol stack to implement the IWF service function. Similarly, the implementation of the IWF service function of GSM is the same as the implementation of the function of the IWF service of CDMA2000. Please refer to Figures 2 and 3, where. 2 is a media plane protocol stack structure defined by an IWF in a CDMA2000 network, and FIG. 3 is a media plane protocol stack structure defined by an IWF in a GSM network. Among them, in the ten discussions of MT and IWF in Figure 2, the uppermost layer is asynchronous data application/PC fax application/ Async Data App/PCFax App/ Analog Fax App. Comparing the structure of the media plane protocol stack shown in Figure 2 and Figure 3, it can be clearly concluded that the format of the media surface of the IWF is inconsistent.

The protocol stack established by the media plane negotiation of the CDMA2000 terminal and the GSM terminal is different, so that the two network type IWF services cannot communicate. SUMMARY OF THE INVENTION To solve the problem that IWF services cannot be interworked between different network types, it is necessary to provide a method for implementing IWF service interworking between networks. In addition, it is also necessary to provide a system for implementing IWF service interworking between networks. The method for implementing IWF service interworking between networks includes the following steps: Initiating network interworking function IWF service requests between different network terminals and allocating and transmitting IWF service parameters to respective H.248g signaling processing units on respective media gateways The wireless side protocol stack processing unit and the IWF service 1⁄4, the negotiation processing unit; the different network terminals respectively establish an RLP link and notify the respective IWF service protocol processing unit to complete the establishment of the interworking link between the networks. In the above method, the request for the network interworking function IWF service between the different network terminals is: the softswitch centers of the different networks establish a connection through the sip protocol; the terminal sends the IWF service through the softswitch center of the network. Requesting to the softswitch center of the different network, and then transmitting to the different network terminals. In the above method, the IWF service protocol processing unit comprises: a standard 3.1k audio modem protocol modulation processing unit, a standard 3. Ik audio modem protocol modulation T.30 fax processing unit, a 64Kbps UDI service processing unit of an ISDN service, and an ISDN service. 56Kbps RDI business processing unit. In the above method, the different network terminals include: a GSM network terminal, and a CDMA2000 network terminal. In the above method, the GSM network terminal establishes a RLP link of the GSM: the GSM network terminal initiates a negotiation of a link layer RLP protocol, and requests the GSM radio side protocol stack processing unit to establish an RLP link; the GSM The wireless side protocol stack processing unit feeds back information about successful RLP link negotiation to the GSM network terminal; the process for the CDMA2000 network terminal to establish an RLP link of the CDMA2000 is: the CDMA2000 wireless side protocol stack processing unit initiates a link layer TCP /IP-PPP/RLP ten tenths of the tenth, requesting the CDMA2000 network terminal to establish a TCP/IP-PPP/RLP link; the CDMA2000 network terminal feeding back to the CDMA2000 wireless side protocol stack processing unit to establish TCP/ IP-PPP/RLP link Ten business success information. In the above method, after the GSM network terminal and the CDMA2000 network terminal respectively establish respective RLP links, the method further includes: the IWF service protocol processing unit of the GSM network sends the GSM RLP chain to the IWF service protocol processing unit of the CDMA2000 network. Establishing success information, and initiating a link negotiation request; the IWF service protocol processing unit of the CDMA2000 network receives the RLP link setup success information of the GSM, and notifies the radio side protocol stack processing unit of the CDMA2000 network; the CDMA2000 The IWF service protocol processing unit of the network answers the link negotiation request, and feeds back the RLP link establishment success information of the CDMA2000; the IWF service protocol processing unit of the GSM network receives the RLP link establishment success information of the CDMA2000, and then notifies The radio side protocol stack processing unit of the GSM network completes establishment of an interworking link between the networks. The present invention also provides a system for implementing IWF service interworking between networks, which includes different network terminals and media gateways of different networks, wherein the media gateways of the different networks respectively include an H.248g signaling processing unit and a wireless side. a protocol stack processing unit, an IWF service protocol processing unit: the media gateways of the different networks, configured to allocate and transmit the IWF service parameters to respective radio side protocol stack processing units and by respective H.248g signaling processing units IWF Business Association After the RLP link is established on the different network terminals, the IWF service protocol processing unit is notified to complete the establishment of the interworking link between the networks. In the above system, the different network terminals include: a GSM network terminal, and a CDMA2000 network terminal. In the above system, the IWF service protocol processing unit of the GSM network is used to

The IWF service ten-processing unit of the CDMA2000 network sends the RLP link setup success information of the GSM and the initiate link negotiation request; and receives the RLP link setup success information of the CDMA2000, and notifies the radio side protocol stack processing of the GSM network. The IWF service protocol processing unit of the CDMA2000 network is configured to receive the RLP link setup success information of the GSM, notify the radio side protocol stack processing unit of the CDMA2000 network, answer the link negotiation request, and feed back The RLP link of CDMA2000 establishes success information. In the above system, the IWF service protocol processing unit comprises: a standard 3. Ik audio modem protocol modulation processing unit, a standard 3. Ik audio modem protocol modulation T.30 fax processing unit, an ISDN service 64 Kbps UDI service processing unit, ISDN 56Kbps RDI business processing unit for business. Compared with the prior art, the present invention establishes an interworking link between IWF service protocol processing units of different network terminals, and realizes the purpose of interworking between IWF services between networks. The features and advantages of the present invention will become more apparent from the detailed description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, In the drawings: FIG. 1 is a schematic diagram of an interconnection service model for a CDMA2000 terminal and a GSM terminal performing an IWF service; FIG. 2 is a media plane protocol stack structure defined by an IWF in a CDMA2000 network; FIG. 3 is a definition of an IWF defined in a GSM network. Media plane protocol stack structure; FIG. 4 is a flow chart of a method for implementing IWF service interworking between networks according to an embodiment of the present invention; FIG. 5 is a schematic diagram of a cooperation process of a GSM terminal requesting a CDMA2000 terminal 3.1k audio asynchronous non-transparent interconnection according to an embodiment of the present invention; FIG. 6 is a schematic diagram of a system module for implementing IWF service interworking between networks according to an embodiment of the present invention; . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides an implementation network in consideration of the problem that the two network type IWF services cannot communicate with each other due to different protocol stacks established by the media plane negotiation of the CDMA2000 terminal and the GSM terminal in the related art. The scheme for interworking between the interworking functions of the IWF service is as follows: the network interworking function IWF service requests are initiated between different network terminals, and the IWF service is allocated and transmitted through the H.248g signaling processing unit on the respective media gateway. The parameters are to the respective wireless side protocol stack processing unit and the IWF service protocol processing unit; the different network terminals respectively establish a wireless link layer protocol RLP link and notify the respective IWF service protocol processing unit to complete the establishment of the interworking link between the networks. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. The invention will be described in detail below with reference to the drawings in conjunction with the embodiments. In the following embodiments, the steps illustrated in the flowchart of the drawings may be performed in a computer system such as a set of computer executable instructions, and although the logical order is illustrated in the flowchart, in some cases The steps shown or described may be performed in an order different from that herein. The method and system for implementing IWF service interworking between networks according to the present invention will be described below with reference to the accompanying drawings, and only in the GSM network and the CDMA2000 network, and other networks: for example, a WCDMA network and a CDMA2000 network. FIG. 4 is a schematic flowchart of a method for implementing IWF service interworking between networks according to an embodiment of the present invention. As shown in FIG. 4, the process includes the following steps: Step S1: Complete negotiation of a control plane between a GSM terminal and a CDMA2000 terminal. That is, the GSM terminal negotiates with the MSCE of the CDMA2000 terminal through the Mobile Switching Center Server (the MSC server) to notify the CDMA2000 terminal. Initiating an IWF service request, the GSM terminal and the CDMA2000 terminal allocate and transmit IWF service parameters to respective IWF radio side protocol stack processing units through respective H.248g signaling processing units, and then allocate and transmit IWF service parameters to respective IWF services. The protocol processing unit; Step S2, establishing an interworking relationship between the GSM terminal and the CDMA2000 terminal. That is, an interworking link is established between the IWF service protocol processing unit of the GSM terminal and the IWF service protocol processing unit of the CDMA2000 terminal. FIG. 5 is a schematic diagram of a cooperation process of a GSM terminal requesting a CDMA2000 terminal 3.1k audio asynchronous opaque interconnection according to an embodiment of the present invention. As shown in FIG. 5, the process includes the following steps: Step S1, completing a GSM terminal and a CDMA2000 terminal Negotiation of the control plane. The step S1 specifically includes: Step S401: The GSM terminal sends the IWF service request to the media gateway of the GSM terminal through the MSC server by using the SetUp message; Step S402, the MSC server of the GSM terminal and the MSCE of the CDMA2000 terminal pass the session initiation protocol (The Session Initiation Protocol, the tube is called SIP) protocol to establish the connection, the MSC server of the GSM terminal sends the IWF service request to the MSCE of the CDMA2000 terminal; Step S403, the MSCE of the CDMA2000 terminal sends the IWF service request to the CDMA2000 terminal and the media gateway of the CDMA2000 terminal. Step S404: The H.248g signaling processing unit of the media gateway of the GSM terminal receives the IWF service request, parses the IWF service parameter, allocates the GSM radio side protocol stack processing unit, and transmits the fc IWF service parameter to the GSM radio side protocol stack. Processing unit; Step S405: The H.248g signaling processing unit of the media gateway of the CDMA2000 terminal receives the IWF service request, parses the IWF service parameter, allocates the CDMA2000 radio side protocol stack processing unit, and transmits the IWF service parameter to the CDMA2000 radio side protocol. a stack processing unit; Step S406, the H.248g signaling processing unit of the media gateway of the GSM terminal, allocates a GSM standard 3.1k audio modem (modem) protocol modulation processing unit, and transmits the IWF service parameter to the GSM standard 3.1k audio Modem modulation processing unit; step S407, H.248g signaling processing unit of the media gateway of the CDMA2000 terminal, allocation The CDMA2000 standard 3.1k audio modem protocol modulates the processing unit, and the IWF service parameters are transmitted to the CDMA2000 standard 3.1k audio modem protocol modulation processing unit. Step S2: Establish an interworking relationship between the GSM terminal and the CDMA2000 terminal. The step S2 includes: Step S410: The GSM terminal initiates a negotiation of a radio link protocol (Radio Link Protocol, RLC), and requests the GSM radio side protocol stack processing unit to establish an RLP link; Step S411, CDMA2000 radio side protocol The stack processing unit initiates the link layer transmission control protocol (Transmission Control Protocol), and the Internet Protocol-Point to Point Protocol (IP-PPP) Negotiation of the RLP protocol, requesting the CDMA2000 terminal to establish a TCP/IP-PPP/RLP link; Step S412, the GSM radio side protocol stack processing unit feeds back information of the RLP link negotiation success to the GSM terminal; Step S413, the CDMA2000 terminal to the CDMA2000 radio side The protocol stack processing unit feeds back information for establishing successful TCP/IP-PPP/RLP link negotiation, and sends an inband AT command AT+CFG="" ATA to the CDMA2000 radio side protocol stack processing unit; Step S414, GSM radio side protocol stack The processing unit notifies the GSM standard 3.1k audio modem protocol modulation processing unit RLP link establishment success; step S415, GSM standard 3.1k audio modem protocol modulation processing unit to CDMA2000 The standard 3.1k audio modem protocol modulation processing unit sends a link success confirmation CONNECT, that is, link establishment success information, and initiates a link negotiation request; step S416, the CDMA2000 radio side protocol stack processing unit sets the AT command of the CDMA2000 terminal AT+CFG= "" ATA performs in-band parsing, and part of the ATA is transmitted to the CDMA2000 standard 3.1k audio modem protocol modulation processing unit; Step S417, CDMA2000 standard 3.1k audio modem protocol modulation processing unit, responding to the GSM standard 3.1k audio modem protocol modulation processing unit The link negotiation request, the sending link succeeds in confirming CONNECT; Step S418, receiving the GSM standard 3.1k audio modem protocol modulation processing unit link successfully confirming CONNECT, CDMA2000 standard 3.1k audio modem protocol modulation processing unit The CDMA2000 wireless side protocol stack processing unit is known; Step S419, the GSM standard 3.1k audio modem protocol modulation processing unit notifies the GSM wireless side protocol stack processing unit after receiving the link success confirmation CONNECT; Step S420, the GSM terminal mobile terminal and the CDMA2000 terminal user After the negotiation is complete, the end-to-end link is established, and the two terminals end-to-end interworking are implemented to implement IWF service interworking between the networks. If the above-mentioned operator process fails in any stage, or the response from the corresponding end is not received within the time limit, the GSM terminal and the CDMA2000 terminal will be hung up through MSCe and MSCserver. FIG. 6 is a schematic diagram of a system module for implementing IWF service interworking between networks according to an embodiment of the present invention. As shown in FIG. 6, the system for implementing IWF service interworking between networks includes a GSM terminal and a media gateway of a GSM terminal. , CDMA2000 terminal and media gateway of CDMA2000 terminal. The media gateway of the GSM terminal includes a H.248g signaling processing unit, a GSM radio side protocol stack processing unit, a GSM standard 3.1k audio modem protocol modulation processing unit, and a GSM standard 3. Ik audio modem protocol modulation T.30 fax processing unit , 64Kbps UDI service processing unit of GSM ISDN service, 56Kbps RDI service processing unit of GSM ISDN service.

The IWF service protocol processing unit includes: GSM standard 3.1k audio modem protocol modulation processing unit, GSM standard 3.1k audio modem protocol modulation T.30 fax processing unit, GSM ISDN service 64Kbps unrestricted digital information (Unrestricted Digital Information, cartridge The UDI) service processing unit, the 56Kbps Restricted Digital Information (RDI) service processing unit of the GSM ISDN service.

The media gateway of the CDMA2000 terminal includes an H.248g signaling processing unit, a CDMA2000 wireless side protocol stack processing unit, a standard 3.1k audio modem protocol modulation processing unit, and a standard 3.1k audio modem protocol modulation T.30 fax processing unit. Expand the IWF service of CDMA2000:

SO=4110 (0x0007): asynchronous data 64Kbps UDI service

SO=4120 (0x0008): asynchronous data 56Kbps RDI service , where asynchronous data identifies asynchronous data. The media gateway of the CDMA2000 terminal further includes a 64 Kbps UDI service processing unit of the CDMA2000 Integrated Services Digital Network (ISDN) service, and a 56 Kbps RDI service processing unit of the ISDN service of the CDMA2000.

The IWF service protocol processing unit includes: standard 3.1k audio modem protocol modulation processing unit, standard 3.1k audio modem protocol modulation T.30 fax processing unit, CDMA2000 ISDN service 64Kbps UDI service processing unit, CDMA2000 ISDN service 56Kbps RDI service Processing unit.

The GSM terminal is used to notify the CDMA2000 terminal to initiate an IWF service request and to send an IWF service request to the media gateway of the GSM terminal. That is, the MSC server of the GSM terminal establishes a connection with the MSCE of the CDMA2000 terminal through the sip protocol; the GSM terminal sends the IWF service request to the MSCE of the CDMA2000 terminal through the MSC server, and then transmits the signal to the CDMA2000 terminal. In addition, the GSM terminal is also used to complete the establishment of the RLP link.

The CDMA2000 terminal is used to receive the notification of the GSM terminal and complete the establishment of the RLP link.

The media gateway of the GSM terminal receives and parses the IWF service request from the GSM terminal, obtains the IWF service parameter, and allocates the GSM radio side protocol stack processing unit through the H.248g signaling processing unit, and transmits the IWF service parameter to the GSM radio side protocol. The stack processing unit redistributes the GSM standard 3.1k audio modem protocol modulation processing unit, and transmits the IWF service parameters to the GSM standard 3.1k audio modem protocol modulation processing unit. Similarly, the CDMA2000 terminal media gateway also completes the IWF service protocol processing unit that allocates and transmits IWF service parameters to the CDMA2000 terminal. After the RLP link of the GSM terminal is successfully established, the IWF service protocol processing unit of the GSM terminal is notified. After the RLP link of the CDMA2000 terminal is successfully established, the IWF service protocol processing unit of the CDMA2000 terminal is notified. The IWF service protocol processing unit of the GSM terminal and the IWF service protocol processing unit of the CDMA2000 terminal exchange link establishment success information, and then respectively notify the respective wireless side protocol stack processing units, so that the GSM terminal and the CDMA2000 terminal user face negotiation completion, the terminal pair The link between the two ends is established, and the end-to-end interworking between the two terminals is completed to achieve the purpose of interworking between IWF services. Compared with the prior art, the method and system for implementing IWF service interworking between networks first notify a CDMA2000 terminal to initiate an IWF service request through a GSM terminal, and then allocate and transmit IWF service parameters by respective H.248g signaling processing units. To their respective IWF wireless side associations The stack processing unit allocates and transmits the IWF service parameters to the operations of the respective IWF service protocol processing units, and then the IWF service protocol processing unit of the GSM terminal exchanges the RLP link establishment success information with the IWF service protocol processing unit of the CDMA2000 terminal, Establish interworking links to achieve interworking between IWF services between networks. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device, or they may be separately fabricated into individual integrated circuit modules, or they may be Multiple modules or steps are made into a single integrated circuit module. Thus, the invention is not limited to any specific combination of hardware and software. The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

A method for implementing interworking between networks, the IWF service interworking, and the method includes the following steps:

The network interworking function between the different network terminals initiates the IWF service request and allocates and transmits the IWF service parameters to the respective wireless side protocol stack processing unit and the IWF service protocol processing unit through the H.248g signaling processing unit on the respective media gateway;

The different network terminals respectively establish a radio link layer protocol RLP link and notify each of the IWF service ten processing units to complete the establishment of the interworking link between the networks.

The method according to claim 1, wherein the network interworking function is initiated between the different network terminals, and the IWF service request is:

The softswitch centers of the different networks establish a connection through a session initiation protocol SIP protocol;

The terminal sends an IWF service request to the softswitch center of the different network through the softswitch center of the network, and then transmits the same to the different network terminal.

3. The method according to claim 1, wherein the IWF service protocol processing unit comprises: a standard 3.1k audio modulation and demodulation modem protocol modulation processing unit, and a standard 3.1k audio modulation and demodulation modem protocol modulation T. .30 fax processing unit, 64Kbps unrestricted digital information UDI service processing unit for ISDN service, 56Kbps limited digital information RDI service processing unit for integrated service digital network ISDN service.

The method according to claim 1, wherein the different network terminals comprise: a global mobile communication GSM network terminal, a code division multiple access CDMA2000 network terminal.

The method according to claim 4, wherein the process of establishing a GSM RLP link by the GSM network terminal is:

The GSM network terminal initiates negotiation of a link layer RLP protocol, and requests the GSM wireless side protocol stack processing unit to establish an RLP link;

The GSM radio side protocol stack processing unit feeds back the RLP link 1 "business success information" to the GSM network terminal;

The process of establishing a CDMA2000 RLP link by the CDMA2000 network terminal For:

The CDMA2000 radio side protocol stack processing unit initiates negotiation of a link layer transmission control protocol TCP/Internet Protocol-Point-to-Point Protocol IP-PPP/RLP protocol, requesting the CDMA2000 network terminal to establish a TCP/IP-PPP/RLP link ;

The CDMA2000 network terminal feeds back to the CDMA2000 radio side protocol stack processing unit to establish information for successful TCP/IP-PPP/RLP link negotiation.

The method according to claim 5, wherein after the GSM network terminal and the CDMA2000 network terminal respectively establish respective RLP links, the method further includes:

The IWF service protocol processing unit of the GSM network sends the RLP link setup success information of the GSM to the IWF service protocol processing unit of the CDMA2000 network, and initiates a link negotiation request;

The IWF service protocol processing unit of the CDMA2000 network receives the RLP link setup success information of the GSM, and notifies the radio side protocol stack processing unit of the CDMA2000 network;

The IWF service protocol processing unit of the CDMA2000 network responds to the link negotiation request, and feeds back RLP link establishment success information of the CDMA2000;

The IWF service protocol processing unit of the GSM network receives the RLP link setup success information of the CDMA2000, and then notifies the radio side protocol stack processing unit of the GSM network to complete the establishment of the interworking link between the networks.

A system for implementing IWF service interworking between networks, comprising different network terminals and media gateways of different networks, wherein media gateways of different networks respectively include H.248g signaling processing unit and wireless side protocol stack processing Unit, IWF service protocol processing unit, characterized by:

The media gateways of the different networks are configured to allocate and transmit the IWF service parameters to respective radio side protocol stack processing units and IWF service protocol processing units through respective H.248g signaling processing units; and in the different After establishing the RLP link, the network terminal notifies the IWF service protocol processing unit to complete the establishment of the interworking link between the networks.

The system according to claim 7, wherein the different network terminals comprise: a GSM network terminal, and a CDMA2000 network terminal.

9. The system of claim 8 wherein: The IWF service protocol processing unit of the GSM network is configured to send GSM RLP link setup success information and initiate link negotiation request to the IWF service protocol processing unit of the CDMA2000 network; and receive the CDMA2000 RLP link setup success information. Notifying the wireless side protocol stack processing unit of the GSM network;

The IWF service protocol processing unit of the CDMA2000 network is configured to receive the RLP link setup success information of the GSM, notify the radio side protocol stack processing unit of the CDMA2000 network, answer the link negotiation request, and feed back the CDMA2000 RLP link establishment success information. The system of claim 7 wherein:

The IWF service protocol processing unit comprises: a standard 3.1k audio modem protocol modulation processing unit, a standard 3.1k audio modem protocol modulation T.30 fax processing unit, a 64Kbps UDI service processing unit for ISDN services, and a 56Kbps RDI service processing unit for ISDN services. .