MXPA01002581A - Signalling in a telecommunications system - Google Patents

Abstract

A method of transmitting signalling information in a Public Land Mobile Network (PLMN) between a pair of peer application parts. An adaptation layer is interposed between the TCAP of an SS7 network and a TCP/IP part to allow signalling data to be transmitted to and from an application part via an IP based network. The Adaptation layer provides for translation between global titles or Destination Point Codes (DPCs), used as the basis for addressing in the SS7 network, and IP addresses/port numbers for use in the IP network. The adaptation layer also provides for formatting of messages suitable for processing by the TCP/IP layers, and also for formatting signalling information flowing in the reverse direction.

Description

"SIGNALING IN A TELECOMMUNICATION SYSTEM" FIELD OF THE INVENTION The present invention relates to signaling in a telecommunications system and in particular, even if not necessarily, with the transmission of signaling data in a Mobile Public Domain Field Network.

BACKGROUND OF THE INVENTION In a telecommunications system, signaling equipment and signaling channels are required for the exchange of information between the elements or nodes of the system. In particular, this internodular signal informs the nodes of what is going to be carried out when a telephone call or data is going to be established or released in the so-called "circuit-switched" connections. The signaling is frequently also used to communicate information about the current state of the system and individual subscribers. Modern telecommunications systems now make great use of Common Channel Signaling (CCS) whereby signaling information is - - transmitted on one or more dedicated signaling channels, other than the channels used to carry the real user's information (e.g., voice or data). An important characteristic of the CCS is the same signaling system that can support services in a variety of existing telecommunications networks, eg, Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), and Mobile Land Networks. Public Domain (PLMN), as well as proposed future protocols such as B-ISDN, greatly improving the interoperability of the networks that support the different protocols. Currently, the predominant CCS is known as Signaling System Number 7 (SS7), defined in ITU-T (International Telecommunications Union - Technical) starting the recommendations with Q.700. SS7 is a packet switched system that occupies a time-by-frame interval of Time Division Multiple Access (TDMA) The transmission format (s) Tl (the other time intervals remaining available for the user's voice or data information) . The individual signaling message packets (referred to as Message Signaling Units or MSUs), are associated with the respective individual telephone calls. Since only a quantity - - relatively small signaling information is associated with a single telephone call, a single channel SS7 is able to handle all the signaling between two network nodes (called "signaling points") for several thousand calls. It will be seen that the route taken by an MSU in the SS7 network may be the same as that through which the associated telephone call is established, or may be different. As already stated, SS7 (together with other CCS systems) is capable of supporting a number of different telecommunication networks (e.g., PSTN, ISDN, PLMN). In terms of signal processing, SS7 comprises a Message Transfer Part (MTP) that deals with the physical transfer of the signaling information through the signaling network (MTP layer 1), message format preparation, detection and error correction, etc. (layer MTP 2), and routing the message (layer MTP 3). The SS7 also comprises user parts and application parts that allow several "users" (ie, ISDN User Part, Telephony User Part, Mobile Application Part, etc.) to send the signals in the same signaling network . Figure 1 illustrates a PLMN (GSM) having a Mobile Pass-Through Switching Center (GMSC) 1 that provides an interface for PLMN to "foreign" networks, such as ISDNs, PSTNs * | and other PLMNs. An exemplary Mobile Station (MS), registered in PLMN, is indicated by the reference number 2. A Rijouero of exemplary nodes within PLMN are also shown including: GMSC 1; a Mobile Switching Center (MSC) 3; a Base Station Controller (BSC) 4; a Base Transceiver Station (BTS) 5; a Smart Network node (IN) 6; a Visitor Location Register (VLR) 7; a Home Location Registry (HLR) 8; an Authentication Center (AUC) 9; and an Equipment Identity Register (EIR) 10. A more complete description of a PLMN, and other aspects of telecommunication networks, is provided in "Understanding Telecommunications", volumes 1 and 2, Studentlitteratur, Lund, Sweden (ISBN 91-44-00214-9). Figure 1 indicates the different signaling interfaces that are used to signal between the network nodes described above. These interfaces include: the ISUP / TUP interfaces between GMSC 1 and foreign networks; the INAP interface used between MSC 3 and Smart Network nodes (IN); the MAP interface used between MSC / GMSC 1, 3 and the specific PLMN nodes (VLR, HLR, AUC, EIR) 6-10; BSSMAP used between MSC 3 and BSC 4; and the Abis interface between BSC 4 and BTS 5. Conventionally, all of these interfaces serve as part of the user and application parts of an SS7 network, being above the MTP layers. The resulting protocol stacks are illustrated in Figure 2. In order to provide INAP and MAP (as well as certain other application parts, eg, OMAP, which also depends on non-connectable communication through the signaling network) with certain functions and protocols as well as a standard and a common interface between the application parts and the network signaling service, a Transaction Capability Application Part (TCAP or TC) is interposed between these application parts and MTP. In addition, a Signaling and Control Connection Part (SCCP) is interposed between TCAP and MTP to control the signaling connection. SCCP is also used by certain other application parts (which are referred to as SCCP users, eg, BSSMAP) that do not use TCAP services and that rely on connection-oriented and / or connection-free communication through the signaling network. SS7 makes use of addresses known as Destination Point Codes (DPCs) to route the signaling data through the "visibility area" of the telecommunications network, typically the visibility area being the network itself along with the interfaces between the network and "foreign" networks under the control of other operators. DPC is placed in the MSU head and examined by the network signaling point (SP) during the receipt of MSU to determine the next hop for MSU that is routed to its destination. The so-called Subsystem Numbers (SSNs) are used by SS7 to direct the data to specific application parts (see below) and are also included in MSUs. With reference to Figure 2, it will be noted that routing between various application parts above the SCCP layer is achieved using so-called "global titles". A global title contains (among other things) a number that has been marked in PLMN or the number of a roaming mobile station (for the specific example shown in Figure 1). SCCP contains all the network and routing information that is required to analyze a global title and moves it to DPC and, optionally, a Subsystem Number (SSN) that identifies the next or final signaling point in the SS7 network. In an SS7 network, any change in the DPC assignment within the visibility area requires the operator to update the DPC database (or routing table) that exists in each SP of the network. This, however, adds significantly to the general maintenance costs of the network. The dedicated nature of SS7 makes it generally costly and maintains (in relation to both hardware and software), a '~ J_JSááj ____ l? *' ** ¿. significant barrier especially for new telecommunication operators in perspective. Furthermore, since an SS7 network occupies a bandwidth in the TDMA frames of the transmission protocols E.l / T.l (one interval per time frame), the available bandwidth for calling data of the real user is restricted. Yet another disadvantage of traditional signaling architectures is that the interworking of SS7 networks is ted due to the dedicated nature of the physical MTP layers.

COMPENDIUM OF THE PRESENT INVENTION An object of the present invention is to overcome or at least mitigate the aforementioned disadvantages of the existing telecommunication signaling systems. In accordance with a first aspect of the present invention, there is provided a method for transmitting signaling information in a telecommunications network between a pair of application parts, the method comprising; generating the signaling information in a first of the application parts including the address information associated with the second of the application parts; passing the reporting information from the application part to the Transaction Capability Application Part (TCAP); passing the signaling information from TCAP to an adaptation layer placed to determine an IP address and the port number associated with the address information; passing the signaling information and the IP address and the port number to a part of the Internet Protocol (IP) and transmitting the signaling information through an IP network to the destination IP address in one or more IP datagrams; decapsulate the signaling information in the destination associated with the IP address and an adaptation layer identified by the port number; and route the signaling information to the second part of the user. The use of the IP-based network to transmit the signaling information reduces the need for a conventional signaling infrastructure (even though it can still be used in the part). IP-based networks offer increased flexibility (e.g., routers in the network have auto-update routing boxes) and reduced operating costs, maintenance and engineering compared to conventional telecommunications signaling networks. It will be appreciated that the Control and Signaling Connection Part (SCCP), which is normally interposed between TCAP and MTP in the SS7 network, is omitted from the present invention since it relates to the transmission of signaling information from TCAP to a part of the invention. IP. Rather, the adaptation layer is interleaved with TCAP towards the IP part. SCCP is designed to segment signaling messages into 272 octet blocks, such as are required by SS7 MTP. In contrast, the individual TCP and UDP datagrams are capable of carrying a much larger number of octets than an MTP message. In this way, by omitting SCCP, the present invention avoids unnecessary segmentation of signaling messages. The method of the present invention is particularly applicable to Mobile Public Domain Field Networks (PLMN), where the application partner pair can, for example, peek at Mobile Application Parts (MAPs) or Application Parties of the Intelligent Network (INAPs) present in the respective signaling nodes of PLMN. In certain embodiments of the invention, the adaptation layer carries out a transfer between a Destination Point Code (DPC) and an associated IP address and number - from Port. In other embodiments, however, the IP address and port number are obtained in the adaptation layer directly from a global title that is provided as part of the address information from the application part. Preferably, the adaptation layer is positioned to provide all the service functionality that TCAP would otherwise receive from SCCP including sequence control, return during an error, and congestion control. Preferably, the adaptation layer is positioned to encapsulate the signaling and address information to an appropriate form for further processing by the IP part. Preferably, the signaling information is passed from the adaptation layer to the IP part via a UDP or TPC encapsulation layer. Preferably, the adaptation layer is positioned to encapsulate the direction and direction information to an appropriate form for further processing by the UDP or TCP layers. In accordance with a second aspect of the present invention there is provided an apparatus for transmitting the signaling information in a telecommunications network between a pair of application parts, the apparatus comprising; a generating means for generating the signaling information in a first of the application parts, including the address information associated with the second of the application parts; a Transaction Capability Application Part (TCAP) to receive the signaling information; an adaptation layer positioned to receive the signaling information from TCAP and to determine an IP address and a port number associated with the address information; a part of the Internet Protocol (IP) placed to receive the signaling information and the IP address and the port number and to transmit the signaling information through an IP network to the destination IP address in one or more IP datagrams; a processing means in the destination associated with the IP address and in an adaptation layer identified by the port number, placed to decapsulate the signaling information; and a routing means placed to route the signaling information to the second part of the user.

In accordance with a third aspect of the present invention, a pitch node is provided for coupling the signaling information from a common channel signaling network for (CCS) of a telecommunications system, to a network based on the Internet Protocol (IP). ), the step node comprising: a Message Transfer Part (MTP) placed to receive the signaling information through the CCS network; a Signal Connection Control Part (SCCP) placed to receive the signaling information from the MTP, while the signaling connection is controlled through the CCS network; an adaptation layer positioned to receive the signaling information from SCCP and to determine an IP address and the port number associated with a global title or Destination Port Code (DPC) included in the signaling information; an IP layer to receive the signaling information and the IP address and the port number from the adaptation layer and to be placed for transmission of the signaling information through the IP-based network in the form of IP datagrams.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention and in order to show the way in which it can be carried out, reference will now be made by way of example to the accompanying drawings, in which: Figure 1 schematically illustrates a GSM network together with the signaling protocols used therein; Figure 2 schematically illustrates the signal processing layers of the SS7 protocol of the network of Figure 1; Figure 3 illustrates schematically the use of a TCP / IP network to transmit the signaling information in a telecommunications network; and Figure 4 illustrates the signaling protocol layers present in the nodes of the telecommunications network of Figure 3.

DETAILED DESCRIPTION OF CERTAIN MODALITIES The general structure in terms of signaling nodes and signaling interfaces of a GSM PLMN has already been described in the foregoing with reference to Figures 1 and 2. Figure 3 shows several nodes in GSM PLMN where it is assumed, for purposes of this discussion, that each of these nodes comprises an application part 25 (eg, MAP, INAP) having a conventional composition of -1 * such that it can be supported by SS7 for the sending of signaling information up to a part of application of a glimpse in a certain nodule. Taking into account in particular MSCs 3a, 3b and GMSC 1, these nodes are connected to a conventional network SS7 in order to communicate the signaling information. Smart grids and specific PLMN nodes, including the nodes IN 6, VLR 7, HLR 8, AUC 9, and EIR 10, each have application parts (and in particular MAP and INAP) constructed in a similar way for communication of peek-a-glimpse through SS7. However, these nodes each comprise an additional interface that allows them to communicate the signaling information through the IP network 12. In order to allow the interworking of the connected SS7 nodes and the nodes connected to the IP network, the two signaling networks 11, 12 are connected by a node of step 13. Figure 4 shows schematically the protocol layers present in a node connected to the IP network 12 (Node 1), in the node of step 13 (Node 2) , and a node connected to the network Number 11 of SS7 (Node 3). Of the layers shown, the INAP / MAP, TCAP, SCCP, TCP / IP, the physical layer, and MTP are essentially conventional in structure and therefore will not be described in detail. Instead, the reader should refer to the literature including "Telecommunications of Understanding", volumes 1 and 2, Studentlitteratur, Lund, Sweden (ISBN 91-44-00214-9), and ITU-T recommendations (Union of International Telecommunications - Technique) that begins with Q.700 that defines the Number of Signaling System 7 (SS7). The present discussion is mainly related to the Adaptation layer that allows the TCP / IP and physical layers to replace MTP (and SCCP), in such a way that TCAP can communicate through the IP network 12. As has been discussed in what precedes already, MSUs are routed in an SS7 network using Point Codes of Destination (DPCs) that are fixed to each of MSUs. Within a signaling point, the messages are directed to a specific application (e.g., HLR, VLR, etc.) based on a Subsystem Number (SSN) also set to MSU. On the other hand, the datagrams in the IP network are routed to a destination machine on the basis of an IP address, and to an application that operates on a specific machine based on the IP body number. A main function of the application layer is therefore to move between global titles and IP addresses and port numbers, which is a process that is achieved using a database that associates global titles and IP addresses / numbers from Port.

In node 1, in order for the signaling data to be transmitted to Nodule 3, the adaptation layer determines an IP address and the port number associated with the global title contained in the "primitive" message received from TCAP. The adaptation layer then encapsulates the primitive messages in a format that is available to the TCP (or UDP) layer before passing the information to the TCP (or UDP) layers. An additional function of the Adaptation layer is to monitor the state of the connection between the two communication peek application parts. For example, if the communication between the application parts disintegrates, and can not be restored, then the Adaptation layer can report this to TCAP. It will be appreciated that the Adaptation layer communicates with TCAP in a manner identical to that of SCCP (which is omitted). The TCP / UDP layers pass the encapsulated signaling information to the IP layer. The messages transmitted through the IP network 12 have the following structure: Header Header Header Header Header Data Physical IP TCP Global TCAP INAP / MAP Addresses / DPC / SSN In the node of step 13 (Node 2 in Figure 4), the Adaptation layer is above the IP network and the SS7 network side layers. The adaptation layer provides means for the decapsulation of the received message and passes it to SCCP on the side of the SS7 network for further processing. The messages received by SCCP from the adaptation layer contain either a global title or a DPC / SSN or both. In the case where the message contains only a global title, then SCCP translates that title to DPC / SSN as already described above. For transmission through the SS7 network 11, SCCP passes the primitives, with the associated DPCs, to the MTP that handles the transmission in a known manner. In a similar manner, the protocol layers in the receptor node (Node 3) correspond to the conventional SS7 structure. It will be appreciated by a skilled person that various modifications may be made to the above-described embodiment without departing from the scope of the present invention. For example, the connectivity of the nodes of the network shown in Figure 3 can be varied in such a way that certain IN nodes connect to the SS7 network, while MSCs and / or GMSC can connect to the IP network. It may also be the case that the nodes connect to both the SS7 network and the IP network, so that one network provides a backup for the other network. It will also be appreciated that in case TCAP provides address information to the adaptation layer that includes a DPC / SSN, rather than just a global title, then the adaptation layer can be moved between DPC and the IP address / number of port.

Claims (9)

CLAIMS:

1. A method for transmitting signaling information in a telecommunications network between a pair of application parts, the method comprises: generating the signaling information in a first of the application parts including the address information associated with the second part of the application; passing the reporting information from the application part to the Transaction Capability Application Part (TCAP); passing the signaling information from TCAP to an adaptation layer placed to determine an IP address and a port number associated with the address information; pass the signaling information and the IP address and the port number to a part of the Internet Protocol (IP) and transmit the signaling information through an IP network to the destination IP address in one or more IP datagrams; decapsulate the signaling information in the destination associated with the IP address and in an adaptation layer identified by the port number; and route the signaling information to the second part of the user.

2. A method according to claim 1, for use in a Mobile Public Domain Field Network (PLMN), wherein the pair of application parties peers Mobile Application Parties (MAPs) or Network Application Parties Intelligent (INAPs) present in the respective PLMN signaling nodes.

3. A method according to claim 1 or 2, and comprising passing the address information from TCAP to the adaptation layer including a global title.

4. A method according to any of the preceding claims and comprising passing the address information from TCAP to the adaptation layer including a Destination Point Code and optionally a Subsystem Number.

5. A method according to any of the preceding claims, wherein the adaptation layer provides all the service functionality that TCAP otherwise receives from SCCP including sequence control, return during error, and congestion control.

6. A method according to any of the preceding claims and comprising passing the signaling information from the application part to the adaptation layer through a Party of Application of Transaction Capabilities.

7. A method according to any of the preceding claims wherein the adaptation layer encapsulates the signaling and direction information to an appropriate form for further processing by a UDP / TCP layer placed between the adaptation layer and the IP part.

8. The apparatus for transmitting the signaling information in a telecommunications network between a pair of application parts, the apparatus comprises; a generating means for generating the signaling information in a first of the application parts, including the address information associated with the second of the application parts; a Capacity Application Part of Transaction (TCAP) to receive the signaling information; an adaptation layer positioned to receive the signaling information from TCAP and to determine an IP address and a port number associated with the address information; an Internet Protocol (IP) part placed to receive the signaling information and the IP address and port number and to transmit the signaling information through the IP network to the destination IP address in one or more of the datograms IP; a processing means in the destination associated with the IP address and in an adaptation layer identified by the port number, placed to decapsulate the signaling information; and a routing means positioned to route the signaling information to the second party of the user.

9. A step node that couples the signaling information from a common channel signaling network (CCS) of a telecommunication system to a network based on Internet Protocol (IP) the node comprises: a Message Transfer Part (MTP) placed to receive the signaling information through the CCS network; a Signal Connection Control Part (SCCP) placed to receive the signaling information from MTP, while controlling the signaling connection through the CCS network; an adaptation layer positioned to receive the signaling information from SCCP and to determine an IP address and a port number associated with a global title or Destination Port Code (DPC) included in the signaling information; an IP layer for receiving the signaling information and the IP address and the port number from the adaptation layer and for placing means for the transmission of the signaling information through the IP-based network in the form of IP datagrams .