FI105745B - Signaling in a telecommunications system - Google Patents

Description

105745

Signaling in a telecommunications system Signallering i et telekommunikationssystem

Field of the Invention 5

The present invention relates to signaling in a telecommunications system and in particular to the transmission of signaling information over a packet switched network.

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Background of the Invention

Conventional telecommunication networks for the transmission of voice and other user information have generally relied on specific telecommunications network infrastructures and transmission protocols. However, the recent explosion of digital communication, mainly driven by the use of Intranet networks and the Internet, has shifted towards the use of general infrastructure and common protocols within the telecommunications community 20. The motive behind this move ... is, above all, the desire for interoperability between telecommunication networks and other information networks and, secondly, the cost and performance advantages offered by general "information systems" compared to traditional telecommunications systems.

International Telecommunication Union

In 1996, the Telecommunications Union (ITU) defined 30 standards for the transmission of multimedia data over local area networks (LANs) as well as "inter-networks" ("internetworks") formed by several shared LANs. This standard is known as H.323, and again the 1998 updated version is known as H.323 version 35 2. A fundamental and essential part of H.323 is the capacity for the transfer of 2 105745 digitized and compressed voice data. However, H.323 also has optional capabilities for transferring video and other data formats.

5 For the purpose of negotiating a call between two H.323 terminals and establishing a channel between them for transmitting user and signaling information, H.323 will definitely make use of ITU standard Q.931. In addition, Q.931 is mandatory for 10 certain call maintenance and termination functions.

Known as the Integrated Services Digital Network (ISDN), the protocol is perhaps the most advanced telecommunications network protocol. In a connection between a subscriber and its 15 local exchanges (subscriber "access point"), ISDN uses a signaling protocol known as DSS1 (Digital Subscriber Signaling System), while another ISUP is used to transmit signaling information within the network, i.e., 20 exchange exchanges. (ISDN User Part) protocol.

• In the current competitive telecommunications market 25, it is vital for telecommunications operators to be able to offer a wide range of value-added services as well as to minimize the cost of services to end-users. As such, existing telecommunication network protocols, and in particular ISDN, have evolved to allow the transmission of a plurality of messages and parameters associated with such services between different nodes (i.e., signaling points) of the networks.

Because the Q.931 signaling protocol is largely based on the DSS1-35 protocol, the overall interoperability between ISDN and H.323 is satisfactory. It is therefore possible to replace 3 105745

Intermediate components of an ISDN network using the H.323 network (or better, the TCP / IP network using the H.323 protocol). For example, a connection between two telephone exchanges can be made through the H.323 network. Similarly, it is possible to achieve interoperability between H.323 and non-ISDN networks, e.g. PSTN

(Public Switched Telephone Network), between.

SUMMARY OF THE INVENTION 10 ZI_____________

The present inventors have found that the Q.931 based H.323 signaling protocol is unable to handle certain signaling messages that may be generated in a telecommunications system, which are defined in existing ISUP standards. It has further been found that this incompatibility constitutes an obstacle to the introduction of H.323 in the telecommunications network.

The object of the present invention is to eliminate or at least alleviate the above disadvantages of the present telecommunication signaling systems. It is a further object of the present invention to provide telecommunications. transmission system using packet-switched 25 networks for transporting user information and signaling information: ......

According to a first aspect of the present invention there is provided a method of transmitting signaling information? · Between 30 pairs of telecommunication networks using ISUP over a packet switched network, the method comprising using the H.3234 protocol for communication over a communication network, wherein the signaling information is transported by a Q.931 based protocol extended to 35 not transmitted by the ISUP messages1. capable of carrying 4 105745

The term "extented" is used herein to define that the Q.931-based protocol has been modified to include new messages and / or message fields. ISUP messages that are not already covered by Q.931 (or DSS1) 5 are not transmitted over the communication network merely by encapsulating them in "carrier" messages.

Preferably, the Q.931-based protocol is extended to provide at least one of the following ISUP messages / parameters / functions: Access delivery information; Automatic congestion level; Backward call indicators; 15 Call diversion information; Call history information;

Calling party number;

Calling party's category;

Closed user group 20 interlock code;

Connection number;

Connection request;

Echo control information;

The nature of the connection (Facility indicator); 25 Forward call indicators; Freephone indicators;

Freephone indicators;

Generic number;

Generic reference; 30 Hop counter;

Information indicators;

Information request indicators;

Location number, -35 5 105745 MCID request indicator, - MCID response indicator; Message Compatibility Information, · MLPP Priority (MLPP Precedence); 5 Nature of connection indicators; Network specific facilities;

Optional backward call indicators; 10 Optional forward call indicators, - _______

Original called number; Originating ISC point code (ISC);

Parameter Compatibility 15 information;

Propagation delay counter;

Redirecting number; Redirection information;

Redirection number restriction; 20 Service activation;

Signaling point code;

Subsequent number;

Suspend / Resume indicators. Preferably, the Q.931-25 protocol used by the present invention is "provided for application in the H.323 protocol stack. More preferably, said connection or part of a connection between subscriber parties is established over a TCP / IP based network. This network may be LAN, inter-network, Internet. or a combination of two or more ·· 30. In these cases, the H. 323 protocol stack is constructed above the TCP / IP protocol stack.

According to another aspect of the present invention, there is provided apparatus for transmitting signaling information between two telecommunication networks using ISUP 35 signaling over a 6 105745 packet switched communication network comprising means for using the H.323 protocol to communicate over a communication network based on a protocol 9. has been extended to provide the transmission of ISUP messages that cannot be carried on DSS1.

According to a third aspect of the present invention, there is provided a method of transmitting signaling information 10 between two telecommunication networks using ISUP signaling protocols over a packet switched communication network, the method comprising utilizing the H. 323 protocol to communicate over a communications network, whereby the signaling information is transmitted. H.323 protocol.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the present invention and to see how it may be practiced, reference will now be made by way of example to the accompanying drawings, in which Figure 1 is a schematic diagram of a telecommunication network;

Detailed Description of Certain Embodiments.

The following description is based on the presentation of ITU standard H.323 ···, where the use of a Q.931-based standard to establish and maintain a call connection between two H.323-capable terminals is made mandatory. In the example shown in Figure 1, two exchanges 1.2 of the telecommunications network communicate with the corresponding H.323 gateway nodes 3,4 using the ISUP-35 interface. The gateway nodes 3,4, in turn, communicate with each other via 7 105745 using the TCP / IP protocol over a packet switched communication network 5. More specifically, the H. 323 protocol layer is located on top of the TCP / IP layers in the protocol stacks of two gateway nodes.

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The exchanges 1,2 provide the respective subscriber terminals with 6,7 ISDN access points to the telecommunications network, where the signaling paths are carried between the subscriber terminals and the exchanges using the DSS1 signaling protocol. In the case of a call between two terminals 6,7, the terminal 6 from which the call is established is referred to as the calling party, while the other terminal 7 is referred to as the answering party. It should be noted that switches 1.2 may be located in a single operator network or may be in networks of different operators. It is also to be noted that terminals 6,7 may be connected to respective access centers 1,2 through intermediate routing nodes. ___________ 20 Gateway nodes use an extended version of the Q.931 protocol, as defined by H.323, for seamless signaling between switches 1.2. Specifically, the Q.931 protocol has been expanded to allow the above listed parameters to be transmitted over 25 TCP / IP networks .______

By way of example, Q.931 can be extended to provide the transmission of so-called "clearback" / "reanswern" messages that may be contained in ISUP. Q.931 defines - ·· 30 currently NOTIFY messages with the following structure, where Reference indicates the corresponding data element in Q.931, Direction indicates which direction (s) the data element is allowed to carry with the NOTIFY message ( n = network, u = H.323-35 user, and Length indicates element length in octets: 8 105745

Data Element Reference Direction Type Length _ (Sub-clause) ___

4.2 Both Ml 5 Separator_____

Call Reference 4.3 Both M 2

Message Type 4.4 Both M 1 10 Service Level 4.5 n -> u O 2-12

Announcement Index 4.5 Both M 3 Castors 15 ---------- Display 4.5 n-> u O> 2 20

One of the six message elements is the Notificaton indicator, for which the existing standard Q.931 defines three meaningful values of 25, i.e. states:

Bits 7 6 5 4 3 2 1 ;;; 30 0 0 0 0 0 0 0 User suspended 0000001 User resumed 0000010 Bearer service change

All other facilities are currently occupied.

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Claims (7)

A method for communicating signal data between a pair of telecommunication networks using a packet switching data network A method according to claim 1, wherein the extended protocol Q.931 has been arranged to be applied within an H.323 protocol stack. 15 The method according to claim 2, wherein said connection or part of the connection between the subscriber parties has been established via a TCP / IP network. The method of claim 3, wherein the H.323 protocol stack has been provided over a TCP / IP protocol stack. 5 Base Reference; Koppiingsstegräknare; Information indicators; Information request indicators; Omrädesnummer; 10 MCID Request Indicator; MCID Response Message Indicator; Message Compatibility information; MLPP precedence; Connecting Character Indicators; Night-specific properties; Optional call indicators behind; Optional call indicators forward; Originally dialed numbers; ISC avsändarpunktkod; Parameter compatibility information; Mediation Delay SmA Counter; Transferring numbers; Transfer information; Transfer dialing; 25 Service activation; signaling point; The following numbers; _______________ Cancel / Continue indicators. The method of claim 1, wherein the Q.931-based protocol has been extended to provide at least one of the following ISUP messages: 25 Access Delivery Information; Automatic logging level; Call indicators in the rear; Call transfer information; Samtaishistorikinformation; 30 Calling party number; Calling party category; Closed user group connection code; Connection Number; Connection request; 35 Echo control information; Facilitetsindikator; i ψ 13 105745 Call indicators presented; Free number indicators; base character; __________________ Base number; ISUP signaling, which method involves using protocol H.323 to communicate over the data network, where signal data is carried by a protocol based on Q.931 that has been expanded to provide transmission of ISUP messages that cannot be carried by DSS1. 10 A device for communicating signal data between a pair of telecommunications networks using ISUP signaling via a packet switching data network, the device comprising means for using the protocol H.323 for the communication over the data network where signal data is transported by a protocol based on Q.931 which has been expanded. to convey the ISUP messages that cannot be transported by DSS1. 14 105745 A method of communicating signal data between a pair of telecommunications networks using ISUP signaling via a packet switching data network, which method comprises using protocol H.323 to communicate over the data network, transmitting signal data by means of a protocol based on Q .763 which replaces Q.93X in protocol H.323.