Background
Dual mode phones capable of communicating via GSM and CDMA or GSM and DECT networks have been available for some time. However, although dual mode phones supporting e.g. GSM and bluetooth or W-LAN or other short range radio systems, fixed network access, infrared access or optical network access may already exist, methods and devices supporting both modes of call processing have not been widespread.
In recent years, the percentage of households that have broadband connectivity at home is increasing. Currently in germany, 11% of homes are equipped with broadband connections (mainly ADSL). In sweden this percentage reaches 22% (50% is ADSL, 50% is other technologies). It is expected that the percentage will also increase significantly in the coming years. Most of these users will install private WLAN (wireless local area network) -access points to connect their PCs (personal computers), PDAs (personal digital assistants), mobile phones, etc. to their fixed broadband connections.
Furthermore, it is also expected that the number of public WLAN-hotspots in europe will increase from about 18.000(2003) to 36.000 (2009).
With the increasing number of broadband connections, users are beginning to use their WLAN-IP (internet protocol) phones over broadband connections via PCs and PDAs. In the coming years, mobile phone providers will put on the market so-called GSM/WLAN dual mode phones (e.g. nokia 2005).
For these users of GSM/WLAN dual mode mobile phones it will be very easy to initiate a call via a SIP-client over the WLAN-radio interface towards a SIP-client connected to the same network or even the internet.
Currently, several architectures such as the one disclosed in US 2004/0105434a1 are proposed for integrating cellular networks with WLAN-access points. The main focus is on integrating the WLAN-access point towards the packet switched network.
For example, mobilehome (mobile home) proposes an architecture in which a WLAN-access point is connected to a BSC via a broadband connection. The drawback of this solution is that the same operator has to provide both cellular mobile network and broadband connection. In addition, mobilehome also proposes a solution based on ADSL (asymmetric digital subscriber line) technology.
It is therefore an object of the present invention to provide a method and apparatus that supports more flexible handling of connections to dual mode mobile stations.
Disclosure of Invention
The object of the invention is advantageously achieved by a method as claimed in claim 1, a mobile station as claimed in claim 3 and a node as claimed in claim 4. Further advantageous embodiments can be derived from the dependent claims.
The present invention introduces a method for connecting a mobile station with a cellular telecommunications network, wherein the cellular telecommunications network comprises a core network and a first cellular access network. The core network is connected to the second access network via at least one node operating according to a session initiation protocol. The method comprises the following steps performed by the at least one node operating according to the session initiation protocol: receiving a request for registering the mobile station at least one node, registering the mobile station at said at least one node, receiving a request for registering the mobile station with the cellular telecommunication network, wherein said request is sent in at least one session initiation part message comprising a message according to a protocol used between the first cellular access network and the core network, unpacking said message according to the protocol used between the first cellular access network and the core network, and forwarding said message according to the protocol used between the first cellular radio access network domain and the core network to a control node of the cellular telecommunication network.
In one embodiment of the invention, the method comprises the additional step of determining a control node as a recipient of the unpacked message.
The present invention also provides a mobile station for communicating via a cellular telecommunications network. The mobile station comprises a first part operating according to at least one protocol used between the mobile station and a core network of a cellular telecommunication network, a second part operating according to a session initiation protocol and a connection unit operating according to one of a short range radio protocol, a fixed network protocol, an optical network protocol or an infrared connection protocol.
It is also an object of the invention to provide a node for connecting a core network of a cellular telecommunications network to an access network, wherein said access network operates according to a session initiation protocol. The node acts towards the core network like a cellular access network node and towards the access network like a session initiation protocol proximity server.
In an embodiment of the invention the node further comprises an unpacking unit for unpacking a message according to a protocol used between an access network and a core network of the cellular telecommunication network from at least one message according to the session initiation protocol, and the node further comprises an encapsulating unit for including a message according to a protocol used between an access network and a core network of the cellular telecommunication network into the at least one message according to the session initiation protocol.
In one embodiment of the invention, the first access network is one of a wireless local area network, a bluetooth network, a short-range radio network, a fixed network or an optical network.
A basic concept of the invention is that primary call control, i.e. control of all calls received via a network connected to the second access network, is handled in the core network of the cellular telecommunication network. In addition, location management of mobile stations is also handled in cellular networks. Location management and call control in the second access network is performed on behalf of the cellular telecommunications network or for calls received from another party in the second access network.
Detailed Description
The invention will be further described below by way of examples and figures.
It should be noted that WLAN access is only a typical example and may be replaced by any other access technology, such as bluetooth, optical connection, short-range radio or fixed line connection. In particular, lower cost or higher value access technologies with transmission resources like bandwidth than cellular telecommunication access networks may be advantageously used for the second access network. The cellular telecommunications network may be operated according to any standard, such as PDC (personal digital cellular), AMPS (advanced mobile phone service), D-AMPS (digital advanced mobile phone service), WCDMA (wideband code division multiple access) or CDMA (code division multiple access).
Fig. 1 shows an architecture for enabling a mobile station 101 to access a telecommunications network 113, 114, 115, 110 via a second access network 102, 103, 104, 105, 107, 108, 109, 110. The telecommunications network comprises a home location register 114, a gateway mobile services switching centre 115, a mobile services switching centre 113 and a combined base station controller/session initiation protocol proxy 110 (proximity server), which are interconnected. The combined base station controller/SIP proxy 110 may also be seen as being external to the cellular telecommunication network, depending only on the point of view and without affecting the solution of the invention. The combined base station controller/SIP proxy does not have to support the complete base station controller functionality but performs the actions of the base station controller at least to the extent that the interface used between the mobile services switching centre and the base station controller can be supported. Since the invention is not limited to GSM, the combined base station controller/SIP proxy may be a combination of a respective access network node and SIP proxy supporting an interface used between the respective call control node and a cellular telecommunications access network node. In one embodiment of the invention, the base station controller and the SIP proxy are not combined into a single node, but are connected to each other.
The combined base station controller/SIP proxy 110 is located in an internet domain 109, which internet domain 109 comprises a second SIP proxy 111 connected to a telephone 112 adapted to send signals according to SIP.
The internet domain is connected via an ISP (internet service provider) 108 and a DSLAM (digital subscriber line access multiplexer) 107 to a local exchange 105, which local exchange 105 is connected to a public switched telephone network 106.
The local exchange is also connected to a WLAN access point 103 via a DSL (digital subscriber line) modem 104. The mobile station 101 is connected to a WLAN access point 103 via a WLAN radio connection 102. The mobile station comprises a first part operating according to a protocol compliant with the GSM standard, a second part operating according to a session initiation protocol and a connection unit operating according to the W-LAN protocol.
According to the invention, the mobile station 101 registers in the first SIP proxy 110 using the WLAN radio connection 102. To this end, the mobile station 101 may send a SIP register message to the SIP proxy 110 via the WLAN radio connection. After successful registration, the SIP proxy may return a 2000K message to the mobile station.
As shown in fig. 1a, the mobile station registers with the cellular telecommunications network in a first step 116 by sending a message to the base station controller/SIP proxy 110 via the second access network. The messages are compliant to protocols used between mobile stations and control nodes of the cellular telecommunication network, such as DTAP (direct transfer application part) location update messages. The message is sent in at least one SIP message.
In a next step 117 the base station controller/SIP proxy 110 receives the message, unpacks the message from the at least one SIP message and forwards it to the call control node, mobile services switching centre 113, via the standard interface between the base station controller and the mobile services switching centre. In a subsequent step 118 the mobile services switching centre 113 receives the message, updates the entries in the database for storing subscriber data like the home location register 114 and the visitor location register (not shown) and returns an acknowledgement message. In step 119, the base station controller/SIP proxy 110 receives the message over the interface, encapsulates it into at least one SIP message and sends it towards the mobile station 101 via the second access network. Messages sent between the base station controller/SIP proxy 110 and the mobile station do not necessarily have to conform to SIP but may be sent according to any other protocol used by the second access network for transporting messages.
Fig. 1 does not show a connection to a mobile station via a cellular telecommunications access network. This is due to the fact that according to the invention such a connection is not used and is even not available, for example because it has been deactivated in the mobile station or due to lack of coverage or lack of capacity. This lack of coverage occurs because no equipment is installed in buildings or tunnels, or at temporarily high demand points like trade fairs, sports arenas, etc.
In one embodiment of the invention, the base station controller/SIP proxy 110 uses a table to determine the mobile services switching center to which the mobile services switching center is assigned location information for the mobile station. Such location information may be, for example, an identification of a W-LAN access point, a location area identification, or geographic coordinates. The contents of the table may be configured using the management interface. However, there may also be a fixed relationship between the second access network and the mobile services switching centre.
The basic concept of the present invention is that the base station controller/SIP proxy 110 acts towards the cellular telecommunication network like a node of the cellular telecommunication network and towards the second access network like a node supporting the protocol used in the second access network. The base station controller/SIP proxy 110 tunnels messages received from the cellular telecommunications network, e.g. messages according to 3GPP standard 24.008 version 6.6.0 of 9.2004, through the second access network.
Fig. 2 shows a connection set-up according to the invention. Fig. 2 shows the structure as described for fig. 1. In a first step 201, the gateway mobile services switching centre 115 receives a call request. In step 202 it queries the home location register 114 for routing information. In step 203 the home location register receives the request, looks up which mobile services switching centre is currently serving the mobile station 101, and requests the MSRN (mobile station roaming number) from the mobile services switching centre. In step 204 the mobile services switching centre checks with its visitor location register (not shown) that the mobile station is currently located in the service area of the mobile services switching centre and returns an MSRN. The home location register forwards the MSRN together with the address of the mobile services switching centre in step 205. Steps 201 to 205 are prior art and reflect in a simplified manner the usual procedure for setting up a call to a user served by an access network of a cellular telecommunications network.
For the solution of the invention, the mobile services switching centre does not necessarily have to have information that the mobile station is served by the second access network. It may also operate correctly as if the mobile station were served by a node of the cellular telecommunications network access network. In a preferred embodiment of the invention, the mobile services switching centre stores an indication that the mobile station is served by the second access network. The indication may be, for example, an identification of a base station controller associated with the mobile station's location area associated with, belonging to, or identifying the second access network with which it cooperates or belongs to the information of the second access network.
In step 206, the mobile services switching centre 113 receives the call request message from the gateway mobile services switching centre 115. It performs the usual call setup towards the base station controller serving the location area stored for the mobile station, e.g. in a visitor location register (not shown). In this case, the base station controller/SIP proxy 110. The base station controller/SIP proxy 110 acts like a base station controller towards the mobile services switching centre at least to the extent that: it receives call setup related DTAP messages compliant with 3GPP 24.008 and relays them piggybacked (piggyback) to the mobile station via W-LAN access in SIP messages and vice versa, i.e. receives call setup messages from the mobile station using SIP messages, unpacks the call setup messages from the SIP messages and relays them to the mobile services switching centre. It is irrelevant for the solution of the invention whether the call setup message is transmitted as a SIP message or as according to any other protocol used by the second access network.
In the circuit-switched client of the mobile station 101, the call setup message is terminated, processed and, if appropriate, a response is generated.
Fig. 3 shows a SIP call in the architecture shown in fig. 1 according to the present invention. It should be noted that the architecture of fig. 1 is only one possible embodiment of an architecture that supports the solution of the present invention. A call has been established from a telephone operating according to the session initiation protocol 112 to the mobile station 101 via the second SIP proxy 111, the DSLAM107, the local exchange 105, the DSL modem 104, the WLAN-access point 103 and the WLAN radio connection 102. More specifically, the call is established via a WLAN radio module that provides radio access functionality of the mobile station for a SIP client of the mobile station adapted to run IP multimedia subsystem protocols as defined by 3 GPP. The illustrated call is set up independently of the call control of the cellular telecommunications network and is therefore one of the exceptions to the primary call control principle described above.
Fig. 4 shows a mobile station MS4 according to the invention. The mobile station comprises a first part 1STP operating according to at least one protocol used between the mobile station and a core network of the cellular telecommunication network, a second part 2NDP operating according to a session initiation protocol and a connection unit CU4 operating according to one of a short range radio protocol, a fixed network protocol, an optical network protocol or an infrared connection protocol. The first part 1STP may be a circuit switched client, for example according to a cellular network specification compliant with PDC, AMPS, D-AMPS, WCDMA or CDMA, for example. The second part may for example be a SIP client adapted to run IP multimedia subsystem related protocols as defined by for example 3 GPP. For example, can be implemented by a WLAN radio module, a bluetooth transceiver, a short-range radio unit providing radio access functionality; an optical input-output unit as an infrared interface, for example; or a fixed network input/output unit. The units and portions can be implemented using software, hardware, or a combination thereof.
Fig. 5 shows a node according to the invention. The node is adapted to act towards a core network of a cellular telecommunications network like a cellular access network node and towards a second access network like a session initiation protocol proximity server. In one embodiment of the invention, the node N5 comprises an input output unit IOU5 for sending and receiving messages, an unpacking unit UU5 for unpacking a message according to a protocol used between an access network and a core network of a cellular telecommunication network from at least one message according to the session initiation protocol, and an encapsulating unit PU5 for including a message according to a protocol used between an access network and a core network of a cellular telecommunication network into at least one message according to the session initiation protocol. It further comprises a control unit for controlling the other units and for operating towards a control node of the cellular telecommunications network like an associated cellular telecommunications access network node and towards the second access network like a SIP proxy. The node does not have to support the entire base station controller functionality but performs the actions of the base station controller at least to the extent that the interface used between the mobile services switching centre and the base station controller can be supported. As the invention is not limited to GSM, the node may be a combination of a corresponding cellular telecommunications access network (UTRAN, GERAN, D-AMPS, PDC, CDMA) node and a SIP proxy supporting an interface used between the corresponding call control node and the cellular telecommunications access network node. The session initiation protocol may also be replaced or supplemented by any other protocol for sending messages in the second access network. The units can be implemented using software, hardware or a combination thereof.
Fig. 6 shows a method according to the invention. The method is for connecting a mobile station with a cellular telecommunications network via a second access network. The method comprises the following steps performed by a node operating according to the session initiation protocol, such as a base station controller/SIP proxy as shown in fig. 1.
In a first step 601, the method starts. In a following step 602 the node receives a request for registering the mobile station on at least one node, it registers the mobile station in step 603, receives a request for registering the mobile station with the cellular telecommunications network in step 604, wherein the request is sent in at least one session initiation part message comprising a message according to a protocol used between the first cellular access network and the core network. In step 605 the node unpacks the message and in step 606 forwards the message according to the protocol used between the first cellular access network and the core network to the control node of the cellular telecommunication network. The request for registration may be sent from the mobile station after the connection unit CU5, e.g. a WLAN radio unit, has detected WLAN coverage. It then requests registration and if it is authorized, acquires it. The registration request may be according to known SIP registration procedures.