WO2007141190A1

WO2007141190A1 - Method for supporting handoff calls for ims/cs handover in existing hybrid ims/cs networks

Info

Publication number: WO2007141190A1
Application number: PCT/EP2007/055337
Authority: WO
Inventors: Klaus Hoffmann
Original assignee: Nokia Siemens Networks Gmbh & Co. Kg
Priority date: 2006-06-02
Filing date: 2007-05-31
Publication date: 2007-12-13
Also published as: DE102006025978A1

Abstract

One problem in prior art is that a switching of a call section for a call existing between two subscribers in an FMC (Fixed Mobile Conversion) network (Handoff) to another transmission protocol is not supported by the network. To solve this problem, a switching request originating from a dual mode terminal (DMH) prompts the network to switch the last call section for this terminal to another transmission protocol and in so doing to leave the remaining call section unaffected for the other subscriber.

Description

description

Method for supporting handoff calls for IMS / CS handover in existing hybrid IMS / CS networks

Newer communication architectures provide for the separation of switching networks in connection service-related units and the transport of the user information (Bearer Control). This results in a decomposition / separation of connection structure and medium or Beareraufbau. The

Transfer of user information (switching through the data channel) can thereby port technologies across different high bit rate Trans ^¬ such as ATM, IP and Frame Relay made.

With such a separation, the currently tied networks in narrow ^¬-run telecommunications services are band networks in broad ^¬ to realize. In this case, the subscribers are connected either directly (eg via a DSS1 protocol) or via exchanges configured as media gateway controllers (MGC) (eg via the ISUP protocol). The Nutzinformati ^¬ tions themselves are converted via Media Gateways (MG) in the per ^¬ weils used transport technology.

The control of the media gateways are carried out by each zugeord ^¬ Neten Media Gateway Controllers (MGC). To STEU ^¬ the media gateways augmentation using the Media Gateway Control ^¬ ler standardized protocols such. As the MGCP protocol or the H.248 protocol. Verwen- Data communication between the media gateway controller to a standardized by the ITU ^¬ overbased BICC (Bearer Independent Call Control) protocol, which is formed of a plurality of standardized protocols and thus comprises a protocol family.

An adequate protocol to the BICC protocol is the IETF

Standardization body with the SIP protocol (RFC3261) or the addition SIP-T (RFC3204) / SIP-I emerged. With the latter, ISUP messages - in contrast to the SIP protocol - be transmitted. ISUP messages are generally transmitted through tunnels, ie through transparent transmission.

The connection between two or more SIP subscribers is established with the help of SIP protocol elements. Among other things, SDP (Session Desing Protocol) data is exchanged. SDP data is (bearer) endpoint related data that includes information about the terminals or codecs, IP port, IP address, etc. Should one

Connection between a SIP subscriber and a H.323 or TDM / ISDN participants are created, these SIP protocol elements in the participating Media Gateway Control ^¬ learning accordingly in H.323, TDM or ISDN protocol elements to be implemented.

First fundamental considerations have led within the ITU-T for Draft Recommendation Q .1912.5 "Interworking SIP and BICC / ISUP". These have also been the first considerations of from the ISDN world known supplementary services made same applies to the standardization ^¬ making body 3GPP. for mobile subscribers where SIP-based services are specified (TS 24.229) In particular, an architecture is specified and standardized in the IMS (IP multimedia subsystem), as shown in FIG.

Basically, the ITU-T Q.1912.5 recommendation specifies the conditions that arise between SIP and PSTN subscribers. There is no difference between line-bound and mobile subscribers. However, FMC networks (fixed mobile conversion, ie mixed mobile fixed networks) also use non-mobile subscribers. Thus, in such FMC networks with different units such as clients and gateway units (MGCF, MGC, etc.), there will be interworking of all interlinked units. This is the case, for example, with the feature "hand off call". This feature, for example, Zvi ^¬ rule the SIP protocol / WLAN protocol and the GSM protocol are used. "Hand Off Call" means that two participants - ie a SIP / WLAN participant and any participant - communicate with each other via a SIP protocol, and the SIP / WLAN participant decides during the conversation, his communication over SIP / WLAN over It is of course also possible to change the transmission protocol, eg from GSM to SIP / WLAN. The terminals must be designed ent ^¬ accordingly, ie they must support both protocols (DMH, dual mode phones, GSM / SIP). The connection is not cleared during the switchover process. "Hand Off Call" requires the signaling to a central device in the network (MCF, Mobility Control Function), which controls the switching from the IMS system from SIP / WLAN to the GSM terminal or vice versa for the involved terminal DMH.

The invention has the object of providing a way aufzei ^¬ gene, as the feature "Hand Off Call" in FMC networks can be realized.

The invention is achieved on the basis of the features specified in the preamble of claim 1 by the features claimed in the characterizing part features.

The advantage of the invention is to be seen in the fact is that with the proposed solution is a purely by signaling gesteu- ertes switching ( "hand off") between two Übertragungspro ^¬ protocols flexibly controlled. The compound (CAIL) remains on during the Umschaltevorganges between the ^It is not necessary to disconnect or set up the entire connection.The switchover request can be initiated by any terminal or any point in the network. The control is performed by providing a unique logical identifier (Global Identifier) representing a combination of the telephone number of the A-subscriber and the B-subscriber. Thus, no changes in the existing networks are required, only the terminals and a central facility (MCF) in the network are affected, which offer the feature. This makes it much easier to market the new feature because existing network not ge ^¬ must be changed.

So that the seam or the connecting portion Zvi ^¬ can rule the controller and the participant who is designated by the logical identifier uniquely found again and the reversal of the old connection portion toward for the new connection portion. B. according to RFC3725 (3pcc) accomplished. Furthermore, the mapping of this new logical identifier or the transfer of this new logical identifier from one to the other protocols is provided.

The invention will be explained in more detail below with reference to a figuratively illustrated embodiment.

Show it:

FIG. 1 shows the basic relationships between PSTN and / or mobile subscribers, between which an Internet network is arranged.

FIG. 2 the IM subsystem according to standard TS24.229, FIG. 3 the concrete embodiment of an FMC network,

1 shows the basic relationships between PSTN and / or mobile subscribers, between which an Internet network is arranged. Here are fenbart example 2 PSTN networks of ^¬, in each of a plurality of PSTN subscribers is connected in a known manner. These are brought to local exchanges LE, which in turn are connected to transit exchanges TX. In the transit exchanges TX, the separation between signaling information and payload information is now performed. The signaling information is supplied directly from the transit exchange TX via an ISUP protocol to a respectively assigned media gateway controller MGC (MGC A or MGC B). The payload information is transmitted to a (on the input side) arranged Media Gateway MG (MG A or MG B), which acts as an interface between the TDM network and an ATM or IP transmission network and are transmitted packet-oriented over the relevant transmission network. The media gateway MG A is also controlled by the media gateway controller MGC A, such as the Media Ga ^¬ B teway MG by the media gateway controller MGC B. In the case of transmission of the payload information by the media gateway MG to the media gateway MG A B are the payloads again under the control of the media gateway MG B assigned Media Gate ^¬ way controller MGC B converted into a TDM data stream and supplied to the candidate PSTN participants. The data transferred between the Media Gateway Controller MGC and the respectively assigned Media Gateway are supported by a standardized protocol. This can be at ^¬ play as the MGCP or H.248 protocol. Between the two media gateway controllers MGC A, MGC B, the SIP protocol is preferably used according to the present embodiment. Finally, a subsystem IMS with facilities P-CSCF, PDF is introduced at the media gateway controller MGC B, via the mobile subscriber with z. B. the PSTN participants are ^¬ participants connected. Basically, the configuration shown in FIG. 1 is already an FMC network in its simplest form.

Fig. 2 shows the definition and role of the IMS system ge ^¬ Mäss 3GPP TS 23.002 V6.5.0 (2004-06) standard. Here is ei ^¬ ne BGCF (Breakout gateway control function) functionality described. Furthermore, devices CSCF, P-CSCF and other devices are shown whose interaction is also explained in the above standard. For example, from the BGCF function (Breakout Gateway Control Function) the Network (domain, eg PSTN) is selected, in which the call originating from a SIP terminal UE is to be routed. If the BGCF function determines that the destination is on its own network, ie the network in which the BGCF function is located, the BGCF function selects MGCF functionality responsible for interworking with the PSTN network. If the destination is on a different network, the BGCF functi ^¬ passes on the signaling to the other network. Finally, Fig. 2 may be taken from the device P-CSCF, which acts as the control of the interface Gq. Here a radio ^¬ tion PDF (Policy Decision Function) is stored, which sets the rules in the net.

Fig. 3 shows an FMC network with a plurality of structures. Accordingly, a plurality of meshed networks are removable. These include mobile (GPRS, UMTS) and solid (xDSL, LAN) part ^¬ participants access networks as well as wireless subscriber access ^¬ networks (WLAN) and the conventional GSM networks and PSTN / ISDN networks. As a transition point each network subsystems IMS or domains are arranged. Further, FIG. 3 is a device MCF removed, which controls the conditions in the network for the Leis ^¬ tung characteristic "hand off".

It is now assumed that a subscriber wants A with egg nem subscriber B, for example, via the SIP protocol ^¬ cate commu. In this case, it must already be known when establishing the connection that subscriber A wishes a connection to a terminal DMH. All setup requests of calls to or from terminals DMH are routed via the MCF facility. This has is formed that at ^¬ game as the terminal of the subscriber B as a dual-mode device End ^¬ DMH administration due to the knowledge of how and thus also supports SIP / WLAN protocol, the GSM protocol. Since the terminal of subscriber B according to the present embodiment is to be constructed as a mobile end terminal, it is connected to the Einrich ^¬ tung MCF via the WLAN (or DSL) protocol. Both terminals communicate directly or indirectly via the SIP protocol, which means that the SIP signa- tion from the device MCF to the terminal of subscriber B. If necessary, the SIP bearer (RTP) is introduced via WLAN or DSL via the media proxy to subscriber B (Gi / Mb). This means that this is a SIP via WLAN / DSL subscriber. Likewise, the device MCF can communicate via SIP and subsequently via the GSM protocol with the terminal DMH.

Basically, a DMH terminal has two signaling protocols: a) SIP over WLAN b) Radio Interface (Reference Point Um or Uu, see 3GPP TS 24.002 or 3GPP TS 23.002) (and 24.008), as GSM protocol.

The device MCF must be in the connection path between

Participants A and B are involved, so that the existing connection section between terminal B and the device MCF can be replaced by the new connection section between the terminal and the same. Instead of using a new identifier, it is proposed to use existing parameters and to signal intelligently within existing networks so that the device MCF finds the interface again.

It proposes a combination of existing parameters of SIP and the U / I interfaces. In this case, a combination of the telephone number of the P-asserted ID headers (= SIP protocol element, which has the telephone number of the calling A subscriber) and the telephone number of the TO header (= SIP protocol element, which has the telephone number of the called B subscriber) is made. This combination is when connecting both the SIP protocol element "initial INVITE" for calls back to the terminal DMH of the B ^¬ taker as well as in the SIP protocol element "response (18x / 200)" the "initial INVITE" for calls from the terminal DMH of In the SIP response the p-asserted Id header the remote subscriber (in this example, the B subscriber). So that Endge ^¬ has advised DMH the information that it sends later on "hand off" again to set MCF, so that the seam is clearly found again.

In the present embodiment, it is assumed that subscriber A has established a connection with subscriber B, and the GSM protocol is used between the MCF device and subscriber B. Subscriber B would now like to terminate the communication with the GSM protocol according to the present embodiment and continue with a new protocol as in ^¬ example, the SIP / WLAN protocol. For this purpose, it is provided that subscriber B actuates a button arranged on his terminal. To this end, the terminal sends the DMH ^¬ se information with the feature "hands off call" for the establishment MCF. In order to "hand off call" recognizable as such / Mark, is a predetermined for it and administ tured handoff chosen ^¬ service number.

The further process steps for the SIP component (RFC3261) are shown in Tab. The terminal DMH now establishes a connection with the aid of the SIP protocol to the MCF device. First, a number is entered in the SIP protocol element REQUEST URI that uniquely identifies the "Hand Off Call" feature (eg 0800 500 500). In the p-asserted identity header of the SIP protocol, the address / phone number ^¬ the initiating participant (in this case the subscriber B, z. B. 0049897221234) already has a connection, and the section is to be replaced, called the network eingetra ^¬ This can be done through the network as the network usually guarantees who the actual subscriber is. In the TO HEADER, the address / telephone number of the partner who already has a connection with the initiating subscriber (in this case subscriber A, eg 00415589888) is entered. In the FROM HEADER is the address / phone number of the initiating Participant (participant B) who already has a connection and whose section is to be replaced.

Tab. 1 The device MCF thus receives an INVITE message in which the logical global identifier is inserted. Insbesonde ^¬ re is hereby specified which part / section of the ge ^¬ entire connection path will now be driving overall with the SIP / WLAN protocol to be so here replaced by this Protocol. According to the present embodiment is assumed as ^¬ of that only the connecting portion between the device and MCF subscriber B to the SIP / WLAN protocol is used. Between participant A and the MCF facility, the information shall continue to be provided by means of the

SIP protocol (because, for example, the terminal of subscriber A only supports SIP). Of course, it is obvious that both participants can be equipped with terminals DMH. In the course of the change of the transmission protocol, the physical Verbindungswe ^¬ are further change ge over which useful information is transmitted. The corresponding control operations are also performed by the device MCF (eg with the aid of RFC3725).

The combination for creating the logical global identifier takes place in such a way that the device MCF receives its own address (telephone number eg 0800 500500) in the R-URI upon receipt of the initial INVITE for the handoff call. Thus, rantiert network side the right / unique information ga ^¬ that identifies the handoff. The subscriber number 0049897221234 is stored in the p-asserted identity header and the subscriber number 00415589888 is stored in the to header. The MCF will then look up its table of sections it had built on the original call

004989722123400415589888 (= Global Identifier) to the ex ^¬ cut to uniquely identify between MCF and initiating user.

As a result of these operations, in the device MCF, the connection section or sections are known which are driven in the course of "hand-off call" with the new protocol. In the following, the relationships which result when information about the connection section between the device MCF and subscriber B is transmitted with the aid of the SIP / WLAN protocol and subscriber B wishes to use the GSM protocol as the transmission protocol will now be described. This may be necessary if subscriber B wishes to leave the WLAN area during an existing connection with subscriber A. As a criterion for switching already operating a button located on the terminal has been addressed. Another criterion would be, for example, the radio strength or similar parameters in question. The corresponding ^¬ conditions are addressed in Tab. 2.

Tab. 2

In order to flexibly control the "Hand Off Call" feature by means of signaling, the following procedure is proposed in the SETUP for the GSM component (UU interface) in order to initiate the feature "Hand Off Call":

The GSM protocol element "calling party subaddress" is defined in TS24.008 (chapter 10.5.4.10), and in 3GPP TS 24.081 V6.0.0 (2004-12) CLI the field "subaddress" is defined. In the following, a connection setup from subscriber B to the MCF device is now controlled. In the GSM protocol element "Called party number" an address / telephone number is now entered, which uniquely identifies the service "Hand Off". Furthermore, the address / telephone number of the partner is entered in the GSM protocol element "Subaddress" (ie subscriber A), which already has a connection with the subscriber initiating the service (in this case subscriber B). Finally, in the GSM protocol element "calling party number" the address / Te ^¬ lefonnummer the initiating subscriber (ie subscriber B) is entered, which already has a connection and its section should be replaced. In this way, the device MCF is aware of the connection section to the initiating subscriber (in this case subscriber B), that is to say the connection section which is to be replaced. All three protocol mentioned elements are part of the GSM SETUP connection establishment of Part B ^¬ contractor establishing MCF.

According to the invention it is provided that the device MCF always a SIP protocol element "INVITE" is. In the case of the table Tab. 1 this is already the case, the "INVITE" is sent from subscriber B to the device MCF the SIP Proto ^¬ kollelement. In the case of table Tab. 2 still ei ^¬ ne mapping functionality is thus indicate required. For this an IN service (for the agreed handoff service number) has to be set up, which translates the "calling party subaddress" into the "originally called number". Table 3 shows the mapping functionality:

Tab. 3

First, the content of the GSM protocol element "called party number" is transferred to the ISUP protocol element "Called Party Num ^¬ ber" The IN service (CAMEL / IN Q1601) takes this information and writes it. 1: 1 (ie unchanged in this case) into the ISUP protocol element "Called Party Number." The device MGCF (FIG. 2) receives this information and transmits it to the SIP protocol element "Request URI ", which is fed to the device MCF, the latter thus receiving the same information as in Tab.

Similarly, the content of the GSM protocol elements "Calling Party Number" is moved, in which the device MGCF (see FIG. 2) according to the prior art supplies the p-asserted ID header in the SIP protocol. The same applies to the original Called party number and the associated To header in SIP.

The establishment MCF recognizes therefore be both for calls from the CS on the establishment MGCF as a start for direct SIP in recom- R-URI (service number as a trigger point in user profiling ^¬ le must be in the S-CSCF set in order to MCF gerou ^¬ tet) that this is the desire to "hand off" the legs (section) between the participant, who is in the p-asserted identity and the device MCF, where the part of the participant in the To The device MCF can uniquely find the old existing call between the subscribers by means of the p-Asserted-Identity header and To Header.With the help of a re-INVITE message, the old connection section within the call found is replaced by the new connection section replaced (using RFC3725 (3pcc)).

The described conditions only work if no telephone number suppression (CLIR) is provided. If this is the case, "Hand Off Call" can nevertheless be executed, and the device MCF must then have an individual telephone number that is unique for the respective call (but call numbers not previously allocated in the international call number plan, eg beginning with a country code the establishment MCF is not used which today) used / are sent. Zusätz ^¬, there must SIP privacy header that has the content "id" either completely remove or replace the contents of "id" with the value "none" so that the infor- mation in the P-asserted ID header is not removed from the other network elements (P-CSCF, etc), and is passed to the terminal DMH. Thus, when initiating the handoffff, the subscriber can send this unique identification so that the device MCF finds the original call again. The use of an E.164 numbering plan not verwen ^¬ Deten address space is proposed so that the DMH terminal (and only to such terminals are sent these special numbers) this phone number does not display, and instead this number as "partial replacement identifier" for later handoff call used.

Claims

claims

1. A method for supporting the feature "hand off call" in communication networks, wherein between a first (A) and a second subscriber (B) of the communication network, a connection is formed, which is guided via a central device (MCF) and between the first subscriber (A) and the central device (MCF) via a first connection section, a first transmission protocol (SIP) and between the latter and the second subscriber (B) via a second connection section, if appropriate, a second transmission protocol (SIP, GSM) ge ^¬ long, characterized in that of one of the terminals (A, B) a Umschaltewunsch in

Transmission protocol (GSM, SIP / WLAN) of the central device (MCF) is communicated that from the central device (MCF), the connection section is affected, which is affected by the switching of the transmission protocol that from the central device (MCF) one further connection with the new communications protocol (GSM) to the order ^¬ unlock request initiating terminal (A, B) is constructed such that signaling data and Bearerdaten be taken of the Umschalte- wish non-initiating terminal (A, B) in the further connection, and that the existing connection between the central device (MCF) and the initiating terminal (A, B) with the old transmission protocol (SIP) is degraded.

2. The method according to claim 1, characterized in that the central device (MCF) via only one transmission protocol (SIP) can be addressed.

3. Apparatus according to claim 1, 2, characterized in that that in the event that the initiating end Umschaltewunsch ^¬ device (B) will be addressed via the second communication protocol (GSM) ^¬, the messages sent by the latter to the central device (MCF) is transmitted in the first transmission protocol.

4. The method according to any one of the preceding claims, characterized in that the determination of the connection section, which is affected by the switching of the transmission protocol by a logical combination of an identifier (eg the telephone numbers and / or a replacement identifier) of the switching request initiating terminal (B ) and the remaining device (A).

5. The method according to any one of the preceding claims, characterized in that the Umschaltewunsch is initiated by a multiple Übertragungsproto ^¬ coll supporting terminal (DMH).

6. The method according to any one of the preceding claims, characterized in that the first transmission protocol is designed as a SIP Übertragungspro ^¬ tokoll.

7. The method according to any one of the preceding claims, characterized in that the second transmission protocol as GSM or ISUP or ISDN / Q.931 or analog terminal transmission protocol is formed.

8. The method according to any one of the preceding claims, characterized in that the Umschaltewunsch is initiated by any terminal or any point in the network.