NO312929B1 - Optimized mobile-to-mobile call handling in satellite networks using GPRS / UMTS network architecture - Google Patents

Description

The present invention relates to satellite-based mobile phone systems and methods for handling mobile-to-mobile calls in satellite networks that use "General Packet Radio Service" / "Universal Mobile Telecommunication System"

(GPRS/UMTS) network architecture. In particular, the method allows the establishment of a short path for mobile-to-mobile user data traffic in such systems.

In a new development in this area, it is proposed that the GPRS/UMTS network architecture should form the ground segment (GS) part of a broadband satellite communication system.

A broadband system of the kind mentioned above can be a point beam system with several terminal beams. In such a system, the satellite will have on board a switch which provides for the 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 proposed data unit format is an ATM cell. The onboard switch will therefore act as an ATM switch providing VC and VP switching. Such a known system is illustrated in the accompanying figure.

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

• Provide user association/authentication functions,

• PDP context management (user session) functions (session management - SM), and

• Control the satellite's switch.

A significant advantage of the broadband satellite communication system lies in its suitability for forming intra-company networks. Such systems, together with terminals for communication at high data rates by means of satellite, enable the interconnection of company offices spread over a large area in an intra-company network, where services offered will range from voice to high-speed data.

In known GPRS/UMTS networks, mobile users are provided with access to the data networks. Network access can be made from the mobile side or the landline side of the GPRS/UMTS network. When a mobile user sets up a connection to another mobile user with the recognition that they are in the same network, in known GPRS/UMTS networks user data will be routed along a path that includes all essential elements in the known networks. The situation is shown in the accompanying figure 2, and illustrates that there is no means in the known GPRS/UMTS network that allows 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 terminals (or mobile stations) are connected to each other in the GPRS network using the mobile-originated and network-originated "PDP Context Activation Procedure". (The procedures illustrated using Figures 2 and 4 are greatly simplified as functions not important to demonstrate the working principles, such as safety functions, are omitted. A full description of these procedures can be found in document GSM 03.60.)

The procedural steps, illustrated by means of Figures 2 and 4, are as follows:

1. The executing 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 using the PDP type (optional), PDP address (optional), and "Access Piont Name (optional) provided using the UT and PDP context subscription entries. If a GGSN address can be derived, the SGSN creates a TID for the PDP context the request applies to by combining the IMSF 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 concerned GGSN. The GGSN can use the "Access Piont Name" to find an external network. The GGSN creates a new entry in its PDP context table and generates a load Id. The new posting enables the GGSN to route PDP PDUs between the SGSN and the external PDP network and to initiate the load. 4. The GGSN then returns a "Create PDP Context Response (TID, PDP Address, Recording Required, PDP Configuration Options, Qos Negotiated, Charging Id, Cause)" message to the SGSN. 5. The SGSN inserts the NSAPF together with the GGSN address into its PDP context. The SGSN 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 waits to route PDPPDUs between the GGSN and the UT, and to start the load.

The PDUs are routed from the UT through the SGSN and the GGSN and out onto the Internet. If the destination of these packets is another UT, the Internet routers recognize this and the packets are routed back to the GGSN as shown in Figure 2. The GGSN then proceeds as follows: 7. When a PDP PDU is received, the GGSN determines whether the PDP the context activation procedure requested by the network must 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 to confirm that it should request the UT to activate the PDP context indicated by 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 - the context activation procedure, as described in steps 1-5 above.

The steps of the procedure described above are controlled in the SGSN node by the session manager

(SM).

Figure 3 illustrates an example of a satellite communication system with a ground segment formed using the GPRS/UMTS network architecture, which shows how GPRS/UMTS nodes can be utilized to control a network with a satellite in the radio communication path.

The known procedure indicated above is mainly defined and standardized in the European standard publication ETSI EN 301 344 V7.3.1 (2000-07) entitled "Digital Cellular Telecommunications System (Phase 2+); General Packet Radio Service ((GPRS); Service Description; Stage 2 (GSM 03.60 version 7.3.1 Release 1998)".

Furthermore, a known wireless telephone system is described in US Patent No. 5594780. The wireless telephone system, which is capable of serving an itinerant user of a wireless telephone, includes a satellite communication system consisting of at least one satellite in orbit; at least one ground-based gateway with access to a database of users, destination codes (telephone numbers), at least one network coordinating gateway in at least one area served by the satellite, a single network control center, and several terrestrial communication links. The system works by effecting communication between an earth-bound wireless user telephone device and an earth-bound communication connection via a single relay connection through a single satellite or a series of individual Telesatellites where the relay station can be in motion in relation to the user's wireless telephone device and the earth-bound communication connection.

With a solution as illustrated in Figure 3, the sequence described above applies to a land mobile network with GPRS/UMTS architecture.

A problem encountered when utilizing the known GPRS solution in a system comprising a satellite is the additional delay caused by the satellite hop in the signaling path 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 the satellites are in geo-synchronous orbits, about 0.25 seconds of delay is introduced for each hop. This delay is avoided and can cause problems with some data communication protocols, such as TCP.

Another problem encountered with a solution as described above and illustrated using the example in Figure 3 is that all user data will be routed through the SGSN and GGSN nodes into the IP network and back as described earlier. In a system based on a known architecture, the SGSN will handle the signaling and allocation of radio resources based on demand. In addition, the SGSN and GGSN must be equipped with large amounts of processing power and buffer capacity to be able to handle data transfers for large terminal numbers, probably in the order of 100,000 - 1,000,000 estimated for a system.

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

It is an object of the invention to relieve

the satellite hop transmission delay problem encountered when communicating between terminals on the ground via satellite.

It is a further purpose of the invention to improve resource utilization in a satellite communication system with a GPRS/UMTS architecture.

Another purpose of the invention is to save radio resources in a satellite-based communication system with GPRS/UMTS architecture.

The present invention provides a telecommunications system with GPRS and/or UMTS architecture and which provides data communication between GPRS- and/or UMTS-adapted user terminals which are connected to the system characterized by the features that appear in the accompanying independent patent claim 1, a telecommunications system with GPRS- and/or UMTS architecture and which provides data communication between GPRS- and/or UMTS-adapted user terminals which are connected to the system characterized by the features that appear in the accompanying independent patent claim 2, and a method in a telecommunications system with GPRS and/or UMTS -architecture to establish a "direct" user terminal-to-user terminal user data packet path between a calling user terminal and a called user terminal via a single transmitter/receiver station characterized by the features that appear in the accompanying independent patent claim 6.

Further advantageous features of the telecommunications system appear from the accompanying non-independent patent claims 3, 4 and 5.

Further advantageous features of the invention's method appear from the accompanying non-independent patent claims 7, 8, 9 and 10.

The invention will then be explained with the help of the accompanying drawings, where:

Figure 1 schematically illustrates the overall architecture of a typical broadband satellite communications system utilizing a multi-terminal beam spot beam system and an on-board switch acting as an ATM switch providing VC and VP switching. Figure 2 is a schematic drawing illustrating the signaling 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 signaling 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 means of Figures 2 and 3. Figure 5 is a schematic diagram illustrating the signaling 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 setup controlled by session manager 2 (SM2) in accordance with the invention in a satellite network using the modified GPRS network solution for mobile-to-mobile packet domain traffic.

The invention handles and/or controls terminal-to-terminal communication in a satellite telecommunications system using GPRS/UMTS network solution, as a "context", which provides a "direct" communication path via satellite between terminals, as illustrated schematically in Figure 5. This the solution will: 1) improve the transmission delay problem as only one "hop" is needed, 2) eliminate resource utilization problem in the SGSN and GGSN nodes as described above, and 3) reduce the radio resource utilization problem (no radio resources are allocated for SGSN for satellite links for data PDU 'is).

In general, the solution is in accordance with the present invention as described in the following: 1) The new session manager functionality (SM2) is added at the SGSN node, which handles and/or controls "direct" terminal-to-terminal sessions for terminals' communication using of the same transceiver station, such as

for example a satellite.

2) The session setup will be a combination of standard (GPRS) mobile-originated/network-originated session setup (see diagram - figure 5), to some extent as described previously (procedural steps 1-10 above), but the session manager (SM2) in accordance with the invention will recognize the setup as

a terminal-to-terminal call and handle it accordingly.

3) SM2 will provide a register that maintains an association between the two setups, thus identifying them as a terminal-to-terminal session. 4) After establishing the connection between the terminals, user data transfer is via satellite and "direct" terminal-to-terminal (Figure 5).

In the following part, and with reference to the diagram shown in figure 6, the invention will be described by means of an example. In this example, mobile station A wishes to communicate with mobile station B. The network includes a station with a switching device, and optionally, a device for converting formats and/or codes of user data signals from a transmitting UT into formats and/or codes of user data signals that can is received at a receiving UT, and the new SM2 of the invention, which controls the setup procedure as follows: Initially, before actions are taken to establish communication between UT A and UT B, it is assumed that both user terminals (or mobile stations, i.e. MS or UT) are in a "standby" mode: 1. The "calling" UT (A participant) 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", APN (R) or APN (S)) identifies the "called" network and determines that this is within the same network domain and a "Request PDP Context Activation" message is sent to it "called" UT (B participant) to activate the specified B participant's PDP context. 3. The B participant's PDP context is activated with the PDP context activation procedure (for example, the B participant's UT sends an "Activate PDP Context Request" message to the SGSN). 4. The SGSN sends a configuration message to the satellite switch, which enables routing of PDUs on an uplink beam from one UT to a downlink beam of another UT, and, when necessary, enables adaptation and/or reshaping of formats and/or code at user data signals from a transmitting UT into formats and/or code of user data signals that can be received at a receiving UT. 5. The SGSN completes the PDP context activation procedure by sending the "Activate PDP Context Access" message to the A participant's and B participant's user terminals (or mobile stations) (or user terminals).

In the following, some advantages of the invention are indicated:

1) The invention enables the reduction of delays on transmission paths for mobile - mobile communication. 2) The invention enables simplification of the SGSN for "direct" mobile-to-mobile communication via satellite, as it only needs to be equipped to handle the signaling.

The example used to describe the invention is "direct" mobile-to-mobile communication via satellite for a better illustration of some of the advantages, but the advantages will also be evident in networks where the satellite is replaced by another node with similar capabilities, such as a suitably equipped base transmitter/receiver station on the ground. Accordingly, the invention can be utilized in general to handle mobile-to-mobile calls in GPRS/UMTS networks, and the application of UMTS signaling for broadband communication should not be limited to UMTS channels.

ABBREVIATIONS AND TECHNICAL TERMS

AccessPointName The APN in the request from the MS (UT)

APN Access Point Name

GPRS General Packet Radio Service

CPR Home Location Register

IMSI International Mobile Subscriber Identity (allocated for each

mobile subscriber<1>)

MS<2> Mobile Station

NCC Network Control Center - network control center

NSAPI Network layer Service Access Point Identifier. NSAPI

identifies the PDP context associated with a PDP

address.

PDP Packet Data Protocol

PDP Address PDP address, for example an X, 121 or an IP address. A MS

subscriber identified by means of an IMSI must have one or more network layer addresses associated with them that conform to the standard addressing scheme of the respective service layer used, such as IP.

PDPType PDP type, for example X.25 or IP.

QoSNegotiated Negotiated quality of service profile

QoSRequested Requested quality of service profile

RAB Radio Access Bearer - radio access bearer

RNC Radio Network Controller - radio network controller

RR Radio Resources - radio resources

Satellite-PL Satellite payload

SGSN Serving GPRS Support Node

SM Session Manager - session manager

TI Transaction Identifier - transaction identifier

UMTS Universal Mobile Telecommunication System

UT User terminal (mobile station)

VC Virtual connection

VPI/VCI Virtual Path/Virtual Connection Identifier

The term "mobile subscriber" in this context indicates a "satellite network subscriber". <2>The expressions UT and MS indicate the same unit.

TERMINOLOGY

ITU-H.323 A family of ASN. 1 -encoded protocols that define message formats, encoding standards, and call state sequences

for multimedia conferencing on an Internet Protocol infrastructure. ITU-H.225.0 A subset of the H.323 standards collection that is based on

Q.931 and defining call control messages,

coding standards and call state sequences.

ITU-H.450 A collection of ASN. 1 standards that define service management protocols to be used for service management in an H.323 network. The H.450 messages are carried within H.225.0

messages.

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

ASN. 1 Abstract Syntac Notation Number 1. ET formally

data structure definition language.

HTTP A MIME (ASCII) encoded protocol for transporting "World-wide-web" data. The protocol is open for tunneling of

other protocols.

CGI Common Gateway Interface. A scripting language used for

customer adaptation of website content.

API Application Programming Interface

DTMF Dual Tone Multiple Frequency

QSIG A service management protocol used by PBX (PBX) PBX Private Branch Exchange - PBX

GSM Global System for Mobile Communication.

A widely used standard for mobile communication

SMS Short Message Service

Messaging service protocol used in GSM "Secure Socket Layer Security" protocol used for

transport layer security (Transport Layer Security).

MIME Multipart Information Message Entity Protocol. An encoding format based on ASCII characters.

SIP Session Initiation Protocol.

An IP telephony protocol based on HTTP.

SMTP Simple Mail Transfer Protocol.

A protocol for the transport/exchange of e-mail messages. NTTP Network News Transfer Protocol.

A protocol for the transport/exchange of news messages.

S/MIME Secure MIME

WAP Wireless Access Protocol.

A web protocol for mobile devices (ie "sort of" HTTP for mobile devices).

Claims (10)

1. Telecommunication system with GPRS and/or UMTS architecture and which provides data communication between GPRS and/or UMTS adapted user terminals (UT) (12,13) which are connected to the system, which system includes at least one transmitter/receiver station (17) which comprises a data switching node and an SGSN (14) with a session controller which handles calls between the user terminals, which data switching node has a control input in communication with the session controller and which enables the connection of an uplink data path (6) between a first associated user terminal (12) and the at least one transmitter -/receiver station of a downlink data path (7) between another associated user terminal (13) and the at least one transmitter/receiver station (17), which session controller is arranged to establish a first section (6) in a call setup from a first user terminal which reaction to a "PDPActivate" call setup request message from the first user terminal and a second line (7) in a call setup from a second user terminal specified in the first user terminal's "PDP_Activate" call setup request message, characterized in that the session manager is further arranged to: Identify GPRS- and/or UMTS-compatible user terminals connected to the system through the same at least one transmitter/receiver station, and if the the first user terminal and the second user terminal are identified as user terminals connected to the system through the same at least one transmitter/receiver station: al) Intercepting the "PDP Activate" call setup request message (1) from it first user terminal and to complete at the SGSN, by means of PDP activation, the first leg call setup as a call setup between the first user terminal (12) and the second user terminal (13) via the uplink data path (16) and the second leg call setup as a call setup between the first user terminal (12) and the second user terminal (13) via the downlink data path (7), or a2) to intercept the "PDP Activate" call setup request message from the first the user terminal and to complete at the SGSN, using PDP activation, the first leg call setup as a call setup between the first user terminal (12) and the second user terminal (13) via the downlink data path (7) and the second leg call setup as a call setup between the first user terminal (12) and the second user terminal (13) via the uplink data path (6), and bl) commanding the data switching node to connect the first user terminal uplink data path (6) to the second user terminal's downlink data path (7), or b2) to command the data switching node to connect the first terminal's downlink data path (6) to the other terminal's uplink data path (7). 2. Telecommunications system with GPRS and/or UMTS architecture and which provides data communication between GPRS and/or UMTS adapted user terminals (UT) (12,13) which are connected to the system, which system includes at least one transmitter/receiver station (17) which comprises a data switching node and an SGSN (14) with a session controller which handles calls between the user terminals, which data switching node has a control input in communication with the session controller and which enables the connection of an uplink data path (6) between a first associated user terminal (12) and the at least one transmitter -/receiver station (17) to a downlink data path (7) between another associated user terminal (13) and the at least one transmitter/receiver station (17), which session manager is arranged to establish a first section (6) in a call setup between the SGSN and a first user terminal in response to a "PDP Activate" call setup request message from the first user terminal and a second line (7) of a call setup seen between the SGSN and a second user terminal indicated in the "PDP_Activate" call setup request message from the first user terminal, characterized in that the session manager is further arranged to: Identify GPRS- and/or UMTS-adapted user terminals connected to the system through the same at least one transceiver station, and if the first user terminal and the second user terminal are identified as user terminals connected to the system through the same at least one transceiver station: cl) To cut off the "PDP_Activate" call setup request message (1) from the first user terminal and to complete at the SGSN, by means of PDP activation, the first leg's call setup as a call setup between the first user terminal (12) and the at least one sending subscriber station via the uplink data path (6) and the second leg's call setup as a call setup between the second user terminal (13) and the at least one transmitter/receiver station via the downlink data path (7), or c2) to intercept the "PDP Activate" call setup response message from the first the user terminal (12) and to complete at the SGSN by means of PDP activation the first leg (6) call setup as a call setup between the first user terminal (12) and the at least one transceiver station (17) via the downlink data path (7) and the second leg's call setup as a call setup between the second user terminal (13) and the at least one transmitter/receiver station (17) via the uplink data path (6), and dl) commanding the data switch node to connect the first user terminal uplink data path (6) to the second user terminal's downlink data path (7), or d2) to command the data switching node to connect the first terminal's downlink data path (7) to the other terminal's uplink data path (6). 3. Telecommunications system as specified in claim 1 or 2, characterized in that the transmitter/receiver station comprises a device for adapting and/or transforming the format and/or code of user data signals from a transmitting UT into the format and/or code of data signals that can be received by a receiving OUT. 4. Telecommunications system as specified in claim 1, 2 or 3, characterized in that the transmitter/receiver station is a satellite transmitter/receiver station or a ground transmitter/receiver station. 5. Telecommunications system as specified in claim 1, 2, 3 or 4, characterized in that the user terminal is allocated to a satellite network subscriber. 6. Method in a telecommunications system with GPRS and/or UMTS architecture for establishing a "direct" user terminal (UT)-to-user terminal (UT) user data packet path between a calling user terminal (12) (A-subscriber UT) and a called user terminal ( 13) (B subscriber UT) via a single transceiver station (17), which telecommunications system provides data packet transmission to/from GPRS and/or UMTS-enabled user terminals (12,13) (UT) and includes an SGSN (14) with a session manager handling calls between user terminals and at least one transceiver station (17) comprising one with a controllable user data packet switching device, which method comprises the steps: e) sending from the A subscriber's UT an "Activate_PDP_Context_Request" message (1) to a SGSN, which "Activate_PDP_Context_Request" message includes NSAPI, TI, PDP type, PDP address, access point name (APN), QOS requested and PDP configuration selection data, f) to validate, by the SGSN, "Activate_PDP_Context_Reques t" message, as the APN(R) (or APN(S)) identifies the B subscriber's UT, characterized by: g) determining in the session manager whether the B subscriber's UT communicates using the the same transmitter-subscriber station as the A-subscriber's UT, and if the B-subscriber's UT communicates using the same transmitter-subscriber station as the A-subscriber's UT: h) to send a "Request_PDP_Context_Activation" (2) message from the SGSN to the called UT (the B-subscriber's UT) to activate the specified B-subscriber's PDP Context; i) activating (3) the B subscriber's PDP_Context with a GPRS PDPContext activation procedure; j) sending a configuration message (4) from the SGSN to the controllable user data packet switching device which initiates the routing of packet data units (PDUs) on an uplink data path from the A subscriber's UT to a downlink data path to the B subscriber's UT, or of packet data units (PDUs 'er) on an uplink data path from the B subscriber's UT to a downlink data path to the A subscriber's UT; and k) sending an "Activate_PDP_Context_Accept" message (5) from the SGSN to the A subscriber's UT and the B subscriber's UT for completion of the PDP_Context activation procedure. 7. Method as stated in claim 6, characterized in that activating the B subscriber's PDP Context with GPRS PDP_Context activation procedure is performed by the B subscriber's UT sending an "Activate_PDP_Context_Request" (3) message to the SGSN. 8. Method as stated in claim 6 or 7, characterized in that it further includes adapting and/or transforming the format and/or code of user data packet signals from the A subscriber's UT to the format and/or code of user data packet signals that are receivable in the B subscriber's UT, or vice versa. 9. Method as stated in claim 6, 7 or 8, characterized in that the transmitter/receiver station (17) is a satellite transmitter/receiver station or a ground transmitter/receiver station. 10. Method as stated in claim 6, 7, 8 or 9, characterized in that the first user terminal (12) and the second user terminal (13) are allocated to satellite network subscribers.