WO2002023768A1

WO2002023768A1 - Optimised mobile-to-mobile call handling in satellite networks using gprs/umts network architecture

Info

Publication number: WO2002023768A1
Application number: PCT/NO2001/000379
Authority: WO
Inventors: Jarle FJØRTOFT; Tormod Hegdahl; Håvard LØBERG; Tormod Wien
Original assignee: Telefonaktiebolaget L M Ericsson
Priority date: 2000-09-18
Filing date: 2001-09-17
Publication date: 2002-03-21
Also published as: NO20004647L; AU2001290365A1; NO20004647D0; NO312929B1

Abstract

A telecommunication system with GPRS architecture, including at least one transceiver station having a controllable switching means, includes a session manager (SM2) functionality controlling sessions between user terminals communicating with the system by means of the same at least one transceiver station. These sessions are set up as 'direct' terminal-to-terminal sessions, and user packet data exchange between the user terminals is routed from the uplink side to the downlink side of the same at least one transceiver station by means of the switching means without traversing other any SGSN or GGSN node of the system.

Description

Optimised mobile-to-mobile call handling in satellite networks using GPRS/UMTS network architecture

FIELD OF THE INVENTION.

The present invention relates to satellite based mobile telephone systems and methods for mobile-to-mobile call handling in satellite networks using General Packet Radio Service Universal Mobile Telecommunication System (GPRS/UMTS) network architecture. Particularly, the method allows establishment of a short path for _'mobile-to- mobile user data traffic in such systems.

THE PROBLEM AREAS.

In a new development in this area, it has been suggested that the GPRS/UMTS network architecture should form the Ground Segment (GS) part of a broadband satellite communication system.

A broadband system of the type mentioned above could be a spot beam system with several terminal beams. In such a system, the satellite will have an on-board switch providing switching of data units in any uplink beam to any downlink beam based on address information contained in the data units. For this purpose, the suggested data unit format is an ATM cell. The on-board switch will, therefore, act as an ATM switch providing VC and VP switching. Such a prior art system is illustrated in the attached figure 1.

In the system described above, the GPRS SGSN node will:

• Provide user attach/authentication functions,

PDP context handling (user session) functions (Session Management - SM), and

Control the satellite switch.

A major advantage of the broad-band satellite communication system lies in suitability for building corporate networks. Such systems, in conjunctions with terminals for communication at high data rates by means of satellite, allow connection of corporate offices spread out over a large area into one corporate network, wherein services offered will span from voice to high-speed data.

KNOWN SOLUTIONS AND PROBLEMS WITH THESE.

In known GPRS/UMTS networks, mobile users are provided with access to the data networks. Network access may be made from a mobile side or the fixed side of the GPRS UMTS network. In known GPRS UMTS networks, when a mobile user sets up a connection towards another mobile user recognised to be in the same network, user data will be routed along a path comprising all essential elements of the known networks. The situation is shown in the attached figure 2, and illustrates that no means exist in the known GPRS/UMTS network allowing a "direct" mobile-to-mobile connection.

In the following, reference is made to the attached figures 2 and 4. These figures illustrate how two user terminal (or mobile station)s connect in the GPRS network using the mobile and network originated PDP Context Activation Procedure. (The procedures illustrated by figures 2 and 4 are highly simplified as functions not important for demonstrating the working principles such as for instance security functions are left out. A complete description of these procedures are found in document GSM 03.60.)

The procedural steps, illustrated by figures 2 and 4, are as follows:

1. The initiating' UT (A-party) sends an Activate PDP Context Request (NS API, TI, PDP Type, PDP Address, Access Point Name (APN), QoS Requested, PDP

Configuration Options) message to the SGSN.

2. The SGSN validates the Activate PDP Context Request using PDP Type (optional), PDP Address (optional), and Access Point Name (optional) provided by the UT and the PDP context subscription records. If a GGSN address can be derived, the SGSN creates a TID for the requested PDP context by combining the IMSI stored in the MM context with the NSAPI received from the UT.

3. The SGSN sends a Create PDP Context Request (PDP Type, PDP Address, Access Point Name, Qos Negotiated, TID, MSISDN, Selection Mode, PDP

Configuration Options) message to the affected GGSN. The GGSN may use Access Point Name to find an external network. The GGSN creates a new entry in its PDP context table and generates a Charging Id. The new entry allows the GGSN to route PDP PDUs between the SGSN and the external PDP network, and to start charging.

4. The GGSN then returns a Create PDP Context Response (TID, PDP Address,

Reordering Required, PDP Configuration Options, Qos Negotiated, Charging Id, Cause) message to the SGSN.

5. The SGSN inserts the NSAPI along with the GGSN address in its PDP context. The returns an Activate PDP Context Accept (PDP Type, PDP Address, TI, Qos

Negotiated, Radio Priority, PDP Configuration Options) message to the UT (or MS).

6. The SGSN is now able to route PDP PDUs between the GGSN and the UT, and to start charging.

The PDUs are routed from the UT through the SGSN and GGSN and onto the Internet. If the target for these packets is another UT, the Internet routers recognise this, and the packets ^"are routed back to the GGSN as shown in figure 2. The GGSN then proceed as follows:

7. When receiving a PDP PDU the GGSN determines if the Network-Requested PDP Context Activation procedure has to be initiated.

8. The GGSN sends a PDU Notification Request (IMSI, PDP Type, PDP Address) message to the SGSN. The SGSN returns a PDU Notification Response (Cause) message to the GGSN in order to acknowledge that it shall request the UT to activate the PDP context indicated with PDP Address.

9. The SGSN sends a Request PDP Context Activation (TI, PDP Type, PDP Address) message to request the UT to activate the indicated PDP context.

10. For the called UT (B-party), the PDP context is activated with the PDP Context Activation procedure, as described in steps 1-5 above.

The steps of the procedure described above is controlled in the SGSN node by the Session Manager (SM). In figure 3 is illustrated an example of a satellite communication system with a ground segment formed by the GPRS/UMTS network architecture, showing how the : GPRS/UMTS nodes could be utilised to control a network with a satellite in the radio communication path.

With a solution as illustrated in figure 3, the sequence described above for a land mobile network with a GPRS/UMTS architecture is applicable.

One problem encountered when employing the known GPRS solution in a system involving a satellite, is the additional delay ι caused by the satellite hop in the signalling as well as the data transmission path. To send data from one UT (or MS) to the other through the network, two satellite hops will be required. Assuming that the satellites are in geo-synchronous orbits, approximately ^lA of a. second delay is introduced for each hop. This delay should be avoided, and can cause problems with some data communication protocols, such as for instance TCP.

Another problem encountered with a solution as described above and illustrated by the example of figure 3, is that all user data will be routed through the SGSN and GGSN nodes onto the IP-net and back as described earlier. In a system based on a known architecture, the SGSN will handle the signalling and assignment of radio resources on a demand basis. In addition, the SGSN and GGSN must be equipped with large amounts of processing power and buffer capacity to be able to handle data transmissions for large numbers of terminals, possibly in the order 100 000 - 1 000 000, which are estimated for one system.

A third problem encountered with a satellite based communication system with known GPRS/UMTS architecture is the utilisation of radio resources. Radio resources, which are limited, must be assigned for up- and downlink channels for each terminal communicating with a satellite and for communication from the SGSN to the satellite for conveying data PDUs (in addition to signalling).

OBJECTS OF THE INVENTION.

It is an object of the invention to mitigate the satellite hop transmission delay problem encountered when communicating between terminals on ground via satellite. It is a further object of the invention to improve the resource utilisation in a satellite communication system with a GPRS/UMTS architecture.

It is yet another object of the invention to save radio resources in a satellite based communication system with GPRS/UMTS architecture.

BRIEF DESCRIPTION OF THE DRAWINGS.

Figure 1 illustrates schematically the overall architecture of a typical broad-band satellite communication system employing a spot beam system with several terminal beams and an on-board switch which acts as an ATM- switch providing VC and VP switching.

Figure 2 is a schematic drawing illustrating signalling sequence and user data path controlled by the Session Manager (SM) in a known ground based GPRS network for mobile-to-mobile packet domain traffic.

Figure 3 is a schematic drawing illustrating the signalling sequence and user data flow path controlled by the Session Manager (SM) in a known satellite network using the GPRS network solution for mobile-to-mobile packet domain traffic.

Figure 4 is a sequence diagram illustrating the typical GPRS PDP context activation procedures also illustrated by figures 2 and 3.

Figure 5 is a schematic diagram illustrating the signalling sequence and user data path controlled by Session Manager 2 (SM2) according to the invention in a satellite network using the modified GPRS network solution for mobile-to-mobile packet domain traffic.

Figure 6 is a sequence diagram illustrating call set-up controlled by Session

Manager 2 (SM2) according to the invention in a satellite network using the modified GPRS network solution for mobile-to-mobile packet domain traffic.

BRIEF DISCLOSURE OF THE INVENTION. The present invention provides a telecommunication system having GPRS architecture and providing data communication between GPRS adapted user terminals (UT) attached to the system, the system comprising at least one transceiver station including a data switching node and an SGSN having a session manager handling calls between said user terminals, the data switching node having a control input in communication with the session manager and allowing connection of an uplink data path between an attached user terminal and said at least one transceiver station to a downlink data path between another attached user terminal and said at least one transceiver station, the session manager arranged to establishing a first leg of a call set-up for a first user terminal as a response to a PDP_activate call set-up request message from the first user terminal and a second leg of a call set-up for a second user terminal specified in the PDP_activate call set-up request message of the first user terminal, said session manager further arranged to: identifying GPRS adapted user terminals attached to the system through the same at least one transceiver station, and, i if the first and second user terminals are identified as user terminals attached to the system through the same at least one transceiver station: a) intercepting the PDP_activate call set-up request message from the first user terminal and completing at the SGSN by PDP activation a first leg call set-up between the first user terminal and the second user terminal and a second leg call set-up between the first user terminal and the second user terminal, and, b) instructing the data switching node to connect the uplink data path of the first user terminal to the downlink path of the second user terminal.

The present invention further provides a telecommunication system having GPRS architecture and providing data communication between GPRS adapted user terminals (UT) attached to the system, the system comprising at least one transceiver station including a data switching node and an SGSN having a session manager handling calls between said user terminals, the data switching node having a control input in communication with the session manager and allowing connection of an uplink data path between an attached user terminal and said at least one transceiver station to a downlink data path between another attached user terminal and said at least one transceiver station, the session manager arranged to establishing a first leg of a call setup between the SGSN and a first user terminal as a response to a PDP_activate call set- up request message from the first user terminal and a second leg of a call set-up between the SGSN and a second user terminal specified in the PDP_activate call set-up request message of the first user terminal, wherein the session manager further is arranged to: identifying GPRS adapted user terminals attached to the system through the same at least one transceiver station, and, if the first and second user terminals are identified as user terminals attached to the system through the same at least one transceiver station: a) intercepting the PDP_activate call set-up request message from the first user terminal and completing at the SGSN by PDP activation a first leg call set-up between the first user terminal and the second user terminal and a second leg call set-up between the first user terminal and the second user terminal, and, b) instructing the data switching node to connect the uplink data path of the first , user terminal to the downlink path of the second user terminal.

Other advantageous features of a system according to the invention include: that the transceiver station includes a means for adapting and/or converting formats and/or code of user data signals from a transmitting UT to formats and /or code of user data signals receivable at a receiving UT; that the transceiver station is a satellite transceiver station or a ground transceiver station; or that the user terminal is allocated to a satellite network subscriber.

The present invention further provides a method, to be performed in a telecommunication system with GPRS architecture, providing user packet data transfer between GPRS adapted user terminal (UT), for establishing a "direct" UT-to-UT user packet data path between a calling user terminal (A-party UT) and a called user terminal (B-party UT) via only a single transceiver station having a controllable user packet data switching means, comprising the steps of: a) sending from the A-party UT an Activate_PDP_Context Request message to the SGSN, said Activate_PDP_Context Request message including NSAPI, TI, PDP Type, PDP Address, Access Point Name (APN), QoS Requested and PDP Configuration Options data; said method including the further steps of: b) the SGSN validating the Activate_PDP_Context Request message, the APN(R) (or APN (S)) identifying the B-party UT and the SGSN determining that the B-party UT is communicating by means of the same transceiver station as the A-party UT, and the SGSN sending a Request_PDP_Context__Activation message to the called UT (B-party) to activate the indicated B-party PDP context; c) activating the B-party PDP context with the PDP context activation procedure; d) the SGSN sending a configure message to the controllable data switching means to enable routing of Packet Data Units (PDUs) on an uplink beam from the A-party UT to a downlink beam to the B-party UT; and, e) the SGSN completing the PDP context activation procedure by sending the Activate_ PDP_Context_Accept message to the A-party UT and the B-party UT, respectively.

Other advantageous features of a method according to the invention include: that the step of activating the B-party PDP context with the PDP context activation procedure is performed by the B-party UT sending an Activate_PDP_Context_Request, message to the SGSN; that it further comprises the step of adapting and/or converting > formats and/or code of user packet data signals from the A-party UT to formats and /or code of user packet data signals receivable at the B-party UT, or vice versa; that the transceiver station is a satellite transceiver station or a ground transceiver station; or that the user terminals are allocated to satellite network subscribers. >

The invention handles and/or controls terminal-to-terminal communication in satellite telecommunication systems using GPRS/UMTS network solution, as one "context", providing a "direct" communication path via satellite between terminals, as illustrated schematically in figure 5. This solution will:

1) improve the transmission delay problem as only one "hop" is required,

2) eliminate the resource utilisation problem in the SGSN and GGSN nodes as described above, and

3) reduce the radio resource utilisation problem (no radio resources assigned for SGSN to satellite links for data PDUs).

In general, the solution according to the present invention is as described in the following:

1) The new Session Manager functionality (SM2) is added to the SGSN node, handling and/or controlling "direct" terminal-to-terminal sessions for terminals communication by means of the same transceiver station, such as e.g. a satellite.

2) The session set-up will be initiated by an originating terminal as a GPRS standard mobile originated session comprising several of the previously explained prosedural steps (see procedural steps 1-10 above). As will be explained in more detail later, in a system or method implementing the invention, procedural step 1 will be maintained, while procedural step number 2 is changed in that SM2 performs a validation and provides a register for the set-up. Further, the previously explained procedural steps 3, 4, 6, 7 and 8 are no longer applicable, as procedural step number 3 in a solution according to the invention corresponds to the previously explained procedural step number 9. Also, as is explained below, a new procedural step number 4 is added. Furthermore, procedural step 5 of the previously explained procedure is maintained as procedural step number 5 in a solution implementing the invention, with the exception that a GGSN address is not required. Accordingly, in a solution implementing the invention, procedural step number 5 does not require that the GGSN inserts the NSAPI along with the GGSN address in its PDP Context.

3) SM2 will provide a register maintaining an association between the two set-ups, thus identifying them as a terminal-to-terminal session. SM2 logs all attach requests coming to the SGSN and either includes a configured table mapping logical APN names to identifications received ((IMSI/MSISDN) or number group) received in the attach request) in the attach or the attach identifications (MSISDN or group) must be used in the CREATE_PDP Context message. A network convention for the actual transceiver or satellite system is needed, but is beyond the scope of the present invention.

4) The transceiver station, or satellite, is provided with a switch to forward the data messages received on the uplink side to the downlink side. In comparison, a typical satellite system will provide an uplink side which could be from the user terminal to the satellite and the corresponding downlink side for transferring data received on the uplink side towards a ground station on a corresponding downlink side. Provided that a message format is similar or identical for the two cases, that is in a satellite system terminal-to-ground or ground-to-terminal, no further processing of the data being exchanged between the two terminals will be required. Preferably, the switch should be general in such a way that any uplink path can be switched to any downlink path, which may be a typical solution due to other needs such as transceiver reconfiguration for reasons of equipment failure or changes in capacity. Accordingly, instead of commanding the transceiver station switch to forward data between a mobile terminal and an intermediate node, such as e.g. the SGSN, the switch will be commanded to set up the path from one user terminal to another user terminal. In the case where the transceiver station is a satellite, the channels typically will be controlled from a ground station. In accordance with the aforesaid, in a solution according to the invention the SGSN will provide control signalling which will signal, via transceiver control, which transceiver channels shall be used for uplink and downlink in a particular set-up, which in a solution according to the invention will be command establishing a terminal datapath. Accordingly, after the connection between the terminals has been established as explained above, user data transfer between the user terminals of the session set-up appears to be "direct" terminal-to-terminal, although via a common transceiver station, or a common satellite. (Fig. 5)

In the following part, and referring to the diagram shown in figure 6, the invention will be described by way of example. In this e+xample, Mobile Station A wants to communicate with Mobile Station B. The network includes a station with a switching means, and, optionally, a means for converting formats and/or code of user data signals from a transmitting UT to formats and /or code of user data signals receivable at a receiving UT, and the new SM2 of the invention, controlling the set-up procedure as follows:

Initially, before actions are made to establish communication between UT A and UT B, it is assumed that both user terminals (or mobile station, i.e. MS or UT) are in STANDBY mode:

1. The "calling" UT (A-party) sends an Activate PDP Context Request (NSAPI, TI, PDP Type, PDP Address, Access Point Name (APN), QoS Requested, PDP Configuration Options) message to the SGSN. 2. The SGSN validates the Activate PDP Context Request, the APN(R) (or APN (S)) identifies the "called" network and determines that this is within same network domain, and a Request PDP Context Activation message is sent to the "called" UT (B-party) to activate the indicated B-party PDP context.

3. The B-party PDP context is activated with the PDP context activation procedure (e.g. the B-party UT sends an sends an Activate PDP Context Request message to the SGSN).

4. The SGSN sends a configure message to the satellite switch, enabling routing of PDUs on an uplink beam from a UT to a downlink beam to another UT, and, when

, required, enable adapting and/or converting formats and/or code of user data signals from a transmitting UT to formats and /or code of user data signals receivable at a receiving UT.

5. The SGSN completes the PDP context activation procedure by sending the Activate PDP Context Accept message to the A- and B-party User terminal (or mobile station)s (or User Terminals).

ADVANTAGES. 1) The invention allows shortening of delays on transmission paths for mobile - mobile communication.

2) The invention allows simplifying the SGSN for "direct" mobile-to-mobile communication via satellite, as it only will have to be equipped for handling signalling.

BROADENING.

The example used to describe the invention is "direct" mobile-to-mobile communication via one transceiver station being a satellite station for a better illustration of some of the advantages, but the advantages will also become apparent in networks where the satellite is replaced by another node with similar capabilities, such as e.g. a properly equipped base transceiver station on the ground. Accordingly, the invention could be utilised in general to handle mobile-to-mobile calls between user terminals attached' to the GPRS (or UMTS) network through the same properly equipped transceiver station, and the use of UMTS signalling for wideband communication should not be limited to UMTS channels.

Claims

P a t e n t c l a i m s

1.

A telecommunication system having GPRS architecture and providing data communication between GPRS adapted user terminals (UT) attached to the system, the system comprising at least one transceiver station including a data switching node and an SGSN having a session manager handling calls between said user terminals, . the data switching node having a control input in communication with the session manager and allowing connection of an uplink data path between an attached user terminal and said at least one transceiver station to a downlink data path between another attached user terminal and said at least one transceiver station, the session manager arranged to establishing a first leg of a call set-up for a first user terminal as a response to a PDP_activate call set-up request message from the first user terminal and a second leg of a call set-up for a second user terminal specified in the PDP_activate call set-up request message of the first user terminal, c h a r a c t e r i s e d i n that the session manager is further arranged to: identifying GPRS adapted user terminals attached to the system through the same at least one transceiver station, and, if the first and second user terminals are identified as user terminals attached to the system through the same at least one transceiver station: c) intercepting the PDP_activate call set-up request message from the first user terminal and completing at the SGSN by PDP activation a first leg call set-up • between the first user terminal and the second user terminal and a second leg call set-up between the first user terminal and the second user terminal, and, d) instructing the data switching node to connect the uplink data path of the first user terminal to the downlink path of the second user terminal.

2.

A telecommunication system having GPRS architecture and providing data communication between GPRS adapted user terminals (UT) attached to the system, the system comprising at least one transceiver station including a data switching node and an SGSN having a session manager handling calls between said user terminals, the data switching node having a control input in communication with the session manager and allowing connection of an uplink data path between an attached user terminal and said at least one transceiver station to a downlink data path between another attached user terminal and said at least one transceiver station, the session manager arranged to establishing a first leg of a call set-up between the SGSN and a first user terminal as a response to a PDP_activate call set-up request message from the first user terminal and a second leg of a call set-up between the SGSN and a second user terminal specified in the PDP_activate call set-up request message of the first user terminal, characterised in that the session manager further is arranged to: identifying GPRS adapted user terminals attached to the system through the same at least one transceiver station, and, if the first and second user terminals are identified as user terminals attached to the system through the same at least one transceiver station: c) intercepting the PDP_activate call set-up request message from the first user terminal and completing at the SGSN by PDP activation a first leg call set-up between the first user terminal and the second user terminal and a second leg call set-up between the first user terminal and the second user terminal, and, d) instructing the data switching node to connect the uplink data path of the first user terminal to the downlink path of the second user terminal.

3.

A telecommunication system according to claim 1 or 2, characterised in that the transceiver station includes a means for adapting and/or converting formats and/or code of user data signals from a transmitting UT to formats and /or code of user data signals receivable at a receiving UT.

4. The telecommunication network of claim 1, 2 or 3, characterised in that the transceiver station is a satellite transceiver station or a ground transceiver station.

5.

The telecommunication network of claim 1,2, 3 or 4, characterised in that the user terminal is allocated to a satellite network subscriber.

6.

A method, in a telecommunication system with GPRS architecture providing user packet data transfer between GPRS adapted user terminal (UT), for establishing a "direct" UT-to-UT user packet data path between a calling user terminal (A-party UT) and a called user terminal (B-party UT) via only a single transceiver station having a controllable user packet data switching means, comprising the steps of: f) sending from the A-party UT an Activate_PDP_Context Request message to the SGSN, said Activate_PDP_Context Request message including NSAPI, TI, PDP Type, PDP Address, Access Point Name (APN), QoS Requested and PDP Configuration Options data; characterised in the further steps of: g) the SGSN validating the Activate_PDP_Context Request message, the APN(R) (or APN (S)) identifying the B-party UT andthe SGSN determining that the B-party UT is communicating by means of the same transceiver station as the A-party UT, and the SGSN sending a Request_PDP_Context_Activation message to the called UT (B-party) to activate the indicated B-party PDP context; h) activating the B-party PDP context with the PDP context activation procedure; i) the SGSN sending a configure message to the controllable data switching means to enable routing of Packet Data Units (PDUs) on an uplink beam from the A-party UT to a downlink beam to the B-party UT; and, j) the SGSN completing the PDP context activation procedure by sending the

Activate_ PDP_Context_Accept message to the A-party UT and the B-party UT, respectively.

7. The method of claim 6, characterised in that the step of activating the B-party PDP context with the PDP context activation procedure is performed by the B-party UT sending an Activate_PDP_Context_Request message to the SGSN.

8. The method of claim 6 or 7, characterised in that it further comprises the step of adapting and/or converting formats andor code of user packet data signals from the A-party UT to formats and /or code of user packet data signals receivable at the B- party UT, or vice versa.

9.

The method of claim 6, 7, or 8 characterised in that the transceiver station is a satellite transceiver station or a ground transceiver station.

10. The method of claim 6, 7, 8 or 9, c h ar a c t e r i s e d in that the user terminals are allocated to satellite network subscribers. ABBREVIATIONS AND TECHNICAL TERMS

AccessPointName The APN requested by the MS (UT) APN Access Point Name GPRS General Packet Radio Service HLR Home Location Register IMSI International Mobile Subscriber Identity - allocated for each mobile subscriber¹

MS Mobile Station

NCC Network Control Centre

NSAPI Network layer Service Access Point Identifier. The NSAPI identifies the PDP context associated with a PDP address.

PDP Packet Data Protocol

PDPAddress PDP address, e.g. an X.121 or an IP address. An MS subscriber identified by an IMSI shall have one or more network layer addresses associated that conforms to the standard addressing scheme of the respective layer service used, e.g. IP.

PDPType PDP type, e.g. X.25 or IP

QoSNegotiated Quality of Service profile negotiated

QoSRequested Quality of Service profile requested

RAB Radio Access Bearer

RNC Radio Network Controller

RR Radio Resources

Satellite-PL Satellite Payload

SGSN Serving GPRS Support Node

SM Session Manager

TI Transaction Identifier

UMTS Universal Mobile Telecommunication System

UT User Terminal (Mobile Station)

VC Virtual Connection

VPI/VCI Virtual Path/Virtual Connection Identifiers

^l The term "mobile subscriber" in this context may also designate a "Satellite Network subscriber". ² The terms UT and MS name the same entity. APPENDIX

Terminology

ITU-H.323 A family of ASN.l encoded protocols defining message formats, encoding standards and call state sequences of multimedia conferences on an Internet protocol infrastructure.

ITU-H.225.0 A subset of the H.323 standards suite being based on Q.931 and defining call control messages, encoding standards and call-state sequences.

ITU-H.450 A suite of ASN.l standards defining service control protocols to be used for service control in an H.323 network. The H.450 messages are being carried within H.225.0 messages.

ITU-Q.931 Telephony standard for call control that defines call control messages, encoding standards and call-state sequences.

ASN.l Abstract Syntax Notation Number 1

A formal data structure definition language

HTTP A MIME (ASCII) encoded protocol for transport of World- wide-web data. The protocol is open for tunnelling of other protocols.

CGI Common Gateway Interface

A script language used for customisation of web page contents

API Application Programming Interface

DTMF Dual Tone Multiple Frequency

QSIG A service control protocol used by PBX

PBX Private Branch Exchange

GSM Global System for Mobile Communication

A widely employed standard for mobile communication

SMS Short Message Service

Messaging service protocol employed within GSM Secure Socket Layer

Security protocol employed for Transport Layer Security MIME Multipart Information Message Entity Protocol encoding format based on

ASCII characters SIP Session Initiation Protocol

IP Telephony protocol based on HTTP SMTP Simple Mail Transfer Protocol

Protocol for transport/exchange of email messages

NTTP Network News Transfer Protocol

Protocol for transport/exchange of news messages S/MIME Secure MIME

WAP Wireless Access Protocol a web protocol for mobile devices (i.e. "a-kind-of HTTP for mobile handsets)