Title of Invention

METHOD FOR PROVIDING MOBILITY BETWEEN EVOLVED UNIVERSAL MOBILE TELECOMMUNICATION SYSTEM AND UNIVERSAL MOBILE TELECOMMUNICATION SYSTEM

Abstract This invention provides a system and method to perform Mobility between the access systems with optimized authentication procedure using security context transfer between the access systems and also minimize the data loss by buffering the data during the handover. The invention explains a method and system for providing mobility between EUMTS and UMTS access systems Using GTP-c between the SGSN and the EGGSN, using AAA proxy functionality at the EGGSN and the SGSN. This also explains mobility between EUMTS and UMTS access systems where the handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture is performed when Inter AS MM is analogous to the MIP Home Agent and also when handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and the IP gateway of the respective Access Systems act as Home Agents where the Inter AS MM is considered. The invention further explains a mobility between EUMTS and UMTS access systems involving the handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and EGGSN acts as the Home Agent where UE moving from the EUMTS network to the UMTS network or UE moves from UMTS network to an l-WLAN network or UE moves from UMTS network back to the EUMTS network.
Full Text FIELD OF THE INVENTION
This invention relates, in general, to wireless technologies. Further, this invention relates to Mobility and Handover between heterogeneous wireless networks. More particularly, this invention relates to a method and system for providing mobility between EUMTS and UMTS access systems.
The scope of the invention also covers the case when the UE is not capable of accessing both the EUMTS and UMTS access systems simultaneously.
This invention provides a system and method to perform Mobility between the access systems with optimized authentication procedure using security context transfer between the access systems and also minimize the data loss by buffering the data during the handover.
DESCRIPTION OF RELATED ART
The radio access network (RAN), system architecture (SA) and the core terminal (CT) working groups of the third generation partnership project (3GPP) aim to develop an enhanced UTRAN (E-UTRAN) architecture for next generation wireless systems. The E-UTRAN system is also called as the system architecture evolution/ long-term evolution (SAE/LTE system). The enhanced UTRAN system is also called as E-UMTS access system. The E-UTRAN system is required to co-exist with the current second (2G) and third generation (3G) wireless systems, and in particular, support handovers between the existing systems and the newly evolved E-UTRAN system, specified in the 3GPP TR 23.882.
The E-UTRAN system is an evolution of the 3GPP UTRAN system, in which the main entities are the user equipment (UE), the enhanced Node B (ENB) and the enhanced GGSN (EGGSN), as shown in the Figure 1. The ENB of the EUMTS system is expected to have the features of the Node B and the radio network controller (RNC) of the legacy UTRAN system. The EGGSN is expected to have the

functionalities of the SGSN and the GGSN of the legacy UTRAN systems.
The 3GPP TR 23.882 also specifies an architecture for integration of 3GPP LTE/SAE and other 3GPP and Non 3GPP access systems as shown in Figure 2.The entities in Figure 2 are as follows:
• The GERAN consists of the Base Transceiver Station (BTS) and the Base Station Controller (BSC).
• The UTRAN consists of the Node B and the Radio Network Controller (RNC).
• The Evolved RAN is the Enhanced Node B (ENB).
• The Evolved Core Network is the Enhanced GGSN (EGGSN) and the Inter AS MM. The EGGSN can also be split into two nodes called mobility management entity (MME) and user plane entity (UPE). The MME and UPE can be combined into a single entity or can exist as two separate entities in the network.
• The Inter Access System Mobility Manager (Inter AS MM) acts as the user plane (UP) IP gateway for Inter RAT handover. It may have the functions of a Mobile IP Home Agent (MIP HA). To all the access networks, the Inter AS MM behaves like an external IP node. The Inter AS Mobility manager can also be called as Inter AS Anchor or SAE anchor. It is possible that GGSN be co-located with the entity or exists as a separate entity in the network.
• The WLAN 3GPP IP access depicts a scenario 3 Inter worked WLAN (l-WLAN).
• The Home Subscription Server (HSS) consists of the Home Location Register (HLR) and the Authentication Center (AuC).
• The Policy and Charging Rules Function (PCRF) specifies the allowed quality-of-service (QoS) for the users as well as the charging policies for the users.
The reference points in Figure 2 are as follows:

• The Gb reference point exists between the SGSN and the BSC of the GERAN. The lu reference point exists between the SGSN and the RNC of the UTRAN.
• The S1 reference point exists between the ENB and EGGSN
• The S2 reference point exists between the Inter AS Anchor and the Non 3GPP access systems
• The S3 reference point exists between the SGSN and MME
• The S4 reference point is between the SGSN and GGSN or between SGSN and Inter AS Anchor (if co-located with GGSN) and is the Gn interface
• The S5 interface exists between the EGGSN and the Inter AS Anchor
• The S6 interface exists between the Evolved packet core and the HSS
• The S7 interface exists between the Evolved packet core and the PCRF. It is an emhanced Rx, Gx interface
• The SGi reference point between the Inter AS MM and external PDN.
Currently there is no efficient mechanism specified to provide handover between the EUMTS and the UMTS access systems.
SUMMARY OF THE INVENTION
The primary object of the invention is to define a system and method to provide handover between the EUMTS and the UMTS access systems.
Another object of the invention is to define a method to optimize the network access authentication procedure during handover.
Accordingly the present invention explains a method for providing mobility between EUMTS and UMTS access systems Using GTP-c between the SGSN and the EGGSN comprising the steps of:
(a) performing the authentication of the UE by the SGSN of the legacy core network;
(b) allocating IP address to the UE when the UE is served by the UMTS network

by the GGSN which acts as the IP gateway;
(c) performing authentication in the EUMTS network by the EGGSN; and
(d) allocating IP address to the UE when the UE is served by the EUMTS network by the EGGSN which acts as the IP gateway;
where ENB of the EUMTS network is capable of converting the RRC protocol messages of the EUMTS network to the RRC messages of the UMTS network and vice-versa.
Accordingly, this invention further explains a method for providing mobility between EUMTS and UMTS access systems using AAA proxy functionality at the EGGSN and the SGSN comprising the steps of:
(a) obtaining the UE security context from a AAA server where the SGSN of the legacy core network acts as an AAA proxy;
(b) allocating IP address to the UE when the UE is served by the UMTS network where GGSN acts as the IP gateway in the UMTS network; and
(c) allocating IP address to the UE when the UE is served by the EUMTS network by EGGSN which acts as IP gateway where the EGGSN of the EUMTS network acts as an AAA proxy for the UE served by the EUMTS network;
where ENB of the EUMTS network is capable of converting the RRC messages of the EUMTS to the RRC messages of the UMTS network and vice-versa.
Accordingly, this invention further explains a method for providing mobility between EUMTS and UMTS access systems where the handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture is performed when Inter AS MM is analogous to the MIP Home Agent, where the Inter AS MM is capable of:
(a) mapping the UMTS cell ID reported by the UE to the appropriate SGSN of the UMTS network;
(b) mapping the cell ID of the EUMTS network to the appropriate EGGSN of the EUMTS network;
(c) resolving the appropriate GGSN for the UE based on the APN specified by the UE;

where the upgradations of the UMTS network is performed where the said upgradation involves:
(d) upgradation of the GGSN and considering it capable of issuing a HO Initiate command to the SGSN over GTP-c;
(e) upgradation of the SGSN to understand the HO initiate command issued by the GGSN and send an HO Response command in response to the HO Initiate Command;
(f) upgrading the SGSN to send an inter RAT HO command to the GGSN Where the GGSN is upgraded to understand the above command and relay it to the Inter AS MM; and
(g) upgrading the SGSN to be capable of passing UE security context information to the Inter AS MM through the GGSN and obtain the security context information from the Inter AS MM through the GGSN.
Accordingly, this invention further explains a method for providing mobility between EUMTS and UMTS access systems involves the Handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and the IP gateway of the respective Access Systems act as Home Agents where the Inter AS MM is considered to be capable of:
(a) resolving SGSN ID from the UMTS cell ID and the EGGSN ID from the EUMTS cell ID;
(b) resolving GGSN from APN;
(c) resolving PDG from W-APN; and
(d) mapping the IMSI to the EGGSN or GGSN that acts as HA for the UE.
where the upgradations of the UMTS network is performed where the said
upgradation involves:
(e) up-grading the GGSN where the GGSN is considered capable of issuing a HO Initiate command to the SGSN over GTP-c;
(f) up-grading the SGSN to understand the HO initiate command issued by the GGSN as well as to send an HO Response command in response to the HO Initiate Command;
(g) up-grading the SGSN to send an inter RAT HO command to the GGSN

where the GGSN is upgraded to understand the above command and relay it to the Inter AS MM; and (h) up-grading the SGSN to consider the SGSN capable of passing UE security context information to the GGSN and obtain the security context information from the EGGSN through the GGSN.
Accordingly, this invention explains a method for providing mobility between EUMTS and UMTS access systems involving the handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and EGGSN acts as the Home Agent where UE moving from the EUMTS network to the UMTS network or UE moves from UMTS network to an l-WLAN network or UE moves from UMTS network back to the EUMTS network.
Accordingly, this invention also explains a method for providing mobility between EUMTS and UMTS access systems involving handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and GGSN acts as the Home Agent where UE moving from the UMTS network to the EUMTS network or UE moves from EUMTS network to an l-WLAN network or UE moves from EUMTS network back to the UMTS network.
Accordingly, this invention explains a system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and UMTS access systems is performed when the SGSN communicate with the EGGSN using the GTP-c protocol.
Accordingly, this invention explains a system for providing mobility between EUMTS and UMTS access systems wherein handover between EUMTS and UMTS access systems is performed when the SGSN and the EGGSN has functionalities of the AAA proxy.
Accordingly, this invention explains a system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and

UMTS Access Systems for the SAE/LTE Architecture is performed when Inter AS MM is analogous to the MIP Home Agent.
Accordingly, this invention explains a system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture is performed when Inter AS MM is used only for signaling and the IP gateway of the respective Access Systems act as Home Agents.
Accordingly, this invention explains a system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture is performed when Inter AS MM is used only for signaling and EGGSN acts as the Home Agent.
Accordingly, this invention explains a system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture is performed when Inter AS MM is used only for signaling and GGSN acts as the Home Agent.
The present invention is related to the scenario where a UE handover from the EUMTS to the UMTS access networks and also from the UMTS to the EUMTS Access system. The method of the invention comprises of mechanisms that provides mobility solution for the UE which cannot access the access systems simultaneously. This invention also includes a mechanism to utilize the active authentication key in one access system to be used in the other access system to optimize the authentication procedure during handover. The invention describes four alternatives for handover between the EUMTS and UMTS access systems by optimizing the authentication procedure during handover.
Accordingly, the present invention comprises a method for providing mobility between the EUMTS and the UMTS access systems wherein the said method includes solutions for the UE which is not capable of simultaneous access; wherein

the said method includes buffering the data destined to the UE by the serving AS during handover procedure and forward the data to the UE after handover procedure.
Accordingly, the present invention further comprises a method as above wherein the said method includes the Handover preparation or request message, sent by the UE in the EUMTS access network to the UMTS access network through the EGGSN or any other entity which has the functionality of SGSN; wherein the said method includes conversion of RRC specific protocols of the UMTS AS to the RRC specific protocol of the EUMTS AS and vice-versa at the ENB of the EUMTS network; wherein the said method includes Handover preparation or request message sent by the UE from the EUMTS AS to UMTS AS contains the, accessing RAT type, Authentication Vectors, EGGSN IP address and other parameters relevant to mobility and security mechanism. Authentication Vectors and EGGSN IP address are included by the serving EGGSN while forwarding the Handover Initiate message; wherein the SGSN and EGGSN can communicate with each other using the GTP-c protocol and exchange UE security context and mobility related messages; wherein the said method includes to provide signaling interface between the EGGSN and the AAA server to exchange messages between them.
Accordingly, the present invention further comprises a method as above wherein the said method includes storing the IP address of the serving EGGSN, active and unused authentication vector in the AAA server corresponding to the NAI of the UE, if HO request is from the EUMTS network; wherein the said method includes to derive tunnel authentication keys using the active EUMTS network access keys by the UE and the AAA server for authentication optimization; wherein the said method includes triggering the EGGSN to release the radio resource of the UE in the EUMTS by the AAA server after attaching itself to the SGSN.
Accordingly, the present invention further comprises a method as above wherein the said method includes triggering the SGSN to release the radio resource of the UE in the EUMTS by the AAA server after attaching itself to the EGGSN; wherein

the said method includes to release the IP address of the UE if MIP based solution is not used; wherein the said method includes initiating buffering of the data at the EGGSN or the GGSN through some signaling message like HO Initiate or HO Response; wherein the Inter AS MM entity in the SAE/LTE Architecture can act similar to an MIP Home Agent and can tunnel UE packets.
Accordingly, the present invention further comprises a method as above wherein the Inter AS MM has a trust relationship with all the access systems and can retrieve UE security context from one AS and can forward to another AS; wherein the said method includes up-gradation of the UMTS SGSN and GGSN where in the GGSN can forward HO Initiate command to the SGSN; wherein the said method includes up-gradation of the UMTS SGSN and GGSN where in the SGSN can forward Inter RAT HO command to the GGSN including the UE security context and identity and respond to the HO Initiate command from the GGSN by sending an HO Response command.
Accordingly, the present invention further comprises a method as above wherein the Inter AS MM of the SAE/LTE Architecture can resolve EGGSN ID from EUMTS cell ID and UE active flows, SGSN ID from UMTS cell ID, GGSN IP address from APN, PDG IP address from the NAI and W-APN; wherein the Inter AS MM can only assist in signaling and the respective IP gateways of the different AS behave like MIP HA and tunnel UE packets; wherein the Inter AS MM can only assist in signaling and the EUMTS network is the home network of the UE and EGGSN acts like the HA for the UE; wherein the Inter AS MM can only assist in signaling and the EUMTS network is the home network of the UE and EGGSN acts like the HA for the UE.
Accordingly, the present invention further comprises a method as above wherein the Inter AS MM can only assist in signaling and the UMTS network is the home network of the UE and GGSN acts like the HA for the UE.
These and other objects, features and advantages of the present invention will

become more apparent from the ensuing detailed description of the invention taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates the EUMTS system architecture and network elements.
Figure 2 illustrates the SAE/LTE Architecture for the integration of LTE and other 3GPP and Non 3GPP access systems with the network elements and reference points.
Figure 3 illustrates the sequence of the message flow during handover from the EUMTS AS to the UMTS AS, when the EGGSN and SGSN can communicate with each other using the GTP-c protocol.
Figure 4 illustrates the sequence of the message flow during handover from the UMTS AS to the EUMTS AS, when the EGGSN and SGSN can communicate with each other using the GTP-c protocol.
Figure 5 illustrates the sequence of the message flow during handover from the EUMTS AS to the UMTS AS, when the EGGSN and SGSN have AAA proxy functionalities and can communicate with the AAA server.
Figure 6 illustrates the sequence of the message flow during handover from the UMTS AS to the EUMTS AS, when the EGGSN and SGSN have AAA proxy functionalities and can communicate with the AAA server.
Figure 7 illustrates the sequence of the message flow during handover from the EUMTS AS to the UMTS AS, for the SAE/LTE architecture when the Inter AS MM tunnels behaves similar to the MIP Home Agent the UE data packets.
Figure 8 illustrates the sequence of the message flow during handover from the

UMTS AS to the EUMTS AS, for the SAE/LTE architecture when the Inter AS MM tunnels behaves similar to the MIP Home Agent the UE data packets
Figure 9 illustrates the sequence of the message flow during handover from the EUMTS AS to the UMTS AS, for the SAE/LTE architecture when the Inter AS MM assists only in signaling and the EGGSN behaves similar to the MIP Home Agent the UE data packets.
Figure 10 illustrates the sequence of the message flow during handover from the UMTS AS to the l-WLAN AS, for the SAE/LTE architecture when the Inter AS MM assists only in signaling and the EGGSN behaves similar to the MIP Home Agent the UE data packets.
Figure 11 illustrates the sequence of the message flow during handover from the UMTS AS to the EUMTS AS, for the SAE/LTE architecture when the Inter AS MM assists only in signaling and the EGGSN behaves similar to the MIP Home Agent the UE data packets.
Figure 12 illustrates the sequence of the message flow during handover from the UMTS AS to the EUMTS AS, for the SAE/LTE architecture when the Inter AS MM assists only in signaling and the GGSN behaves similar to the MIP Home Agent the UE data packets.
Figure 13 illustrates the sequence of the message flow during handover from the EUMTS AS to the l-WLAN AS, for the SAE/LTE architecture when the Inter AS MM assists only in signaling and the GGSN behaves similar to the MIP Home Agent the UE data packets.
Figure 14 illustrates the sequence of the message flow during handover from the EUMTS AS to the UMTS AS, for the SAE/LTE architecture when the Inter AS MM assists only in signaling and the GGSN behaves similar to the MIP Home Agent the UE data packets.

DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. It should be understood however that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. The following description and drawings are not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail.
Operation of the Invention
The present invention provides a system and method for supporting mobility between the EUMTS access system and the UMTS access system and optionally uses MIP protocol to support the mobility.
The method of the invention comprises of mechanisms to move between the EUMTS access system and the l-WLAN access system when the UE have the capability of simultaneous access and also when the UE does not have capability to access simultaneously.
The invention is operated as detailed below:
Mechanism 1: Using GTP-c between the SGSN and the EGGSN
In this mechanism, we present a procedure for handover between the EUMTS and UMTS access systems when the SGSN can communicate with the EGGSN using the GTP-c protocol or alternatively any using any other tunneling protocol. In this

mechanism, the functions performed by the various network entities are as follows:
• The SGSN of the legacy core network performs the authentication of the UE.
• The GGSN acts as the IP gateway in the UMTS network and allocates/assigns IP address to the UE when the UE is served by the UMTS network.
• The authentication in the EUMTS network is performed by the EGGSN. The EGGSN also acts as the IP gateway to the EUMTS network and allocates/assigns IP address to the UE when the UE is served by the EUMTS network.
• The ENB of the EUMTS network can be capable of converting the RRC protocol messages of the EUMTS network to the RRC messages of the UMTS network and vice-versa.
Handover from the EUMTS to the UMTS access system
The optimization of the authentication procedure during the handover can be performed by making the SGSN obtain the UE security from the EGGSN. In this mechanism we consider an interface between the SGSN and the EGGSN that uses the GTP-c or any other tunneling protocol.
For lossless handover, we propose buffering of the packets destined to the UE at the EGGSN during the handover. The GGSN needs to know the EGGSN IP address to obtain the packets and forward then to the UE after the handover. The EGGSN IP address can be obtained in any one of the following ways
• The UE can mention the old IP address and RAI in the PDP context activation procedure, using which the GGSN can resolve the EGGSN IP address
• The HSS can inform the EGGSN IP address to the GGSN
• The GGSN can contact the HSS during the PDP context activation procedure and obtain the EGGSN IP address

The procedure for EUMTS to UMTS handover is explained below.
• The EGGSN takes the decision to handover the UE based on the signal strength measurements. The HO command is given to the UE, with the Cell ID of the UMTS network to which to handover to. The EGGSN also simultaneously starts buffering packets.
• The UE attaches to the given NodeB. After the L2 attach, UE sends the first L3 message to the SGSN. On receipt of the RAU from the UE, the SGSN can obtain the EGGSN address in any one of the following ways:
1. Using the old IP address of the UE (if included in the RAU)
2. Through interaction with HSS
3. Through GGSN which contacts HSS during the PDP context activation.

• User context is now transferred from EGGSN using GTP-C mechanism or through any other control plane protocol. The user context contains the information which can be used for authentication optimization.
• When the UE requests for PDP context, through PDP context Request procedure, the GGSN obtains the IP address of the EGGSN in any one of the following ways:
1. SGSN forwards the EGGSN IP address to the GGSN
2. EGGSN IP address can be obtained by contacting the HSS.
• GGSN forms a tunnel with EGGSN through which the buffered packets are forwarded. Simultaneously, PDP context is also completed. The packets from the EGGSN are now forwarded through appropriate PDP contexts.
• After the formation of the PDP context, MIP Based mobility mechanism can be used for completing the mobility. After MIP procedures have been completed, the HO Complete message is sent, and the resources at the EUMTS network are released.
An illustrative example of the handover procedure from EUMTS access system to the UMTS access system in this scenario is depicted in Figure 3. The description of the handover procedure is provided below.

UE sends periodic or event based measurements to the EUMTS network.
If EGGSN finds that UE measurement is below the threshold or EGGSN decides by any other mean that EUMTS RAT cannot be continued, then EGGSN/ENB can request the UE to start scanning other RATs or alternatively by L2 messaging or by some other means, the UE decides that the EUMTS cannot be continued and starts scanning the other RATs.
. UE scans UMTS RATs and sends the measurement reports to the EGGSN. The measurement report message contains the received signal strength indication (RSSI), cell ID, RAT type (UMTS)
The EGSSN issues a Handover (HO) command signal to the UE and starts buffering the packets destined for the UE. The EGGSN can optionally before sending the HO command, can prepare the target SGSN for the handover by sending a HO request containing the cell ID. The SGSN, in turn, can resolve the RNC ID from the cell ID and prepare the RNC for the impending handover to reserve radio resources.
On receiving the HO Command, the UE performs an L2 establishment with the target Node B of the UMTS network. In the initial L3 message, the UE mentions the pervious routing area identity (RAI).
The SGSN makes use of this information and obtains the UE security context (i. e., the ciphering key (CK), the integrity key (IK), the key set identifier (KSI)) from the EGGSN.
The UE then activates the PDP context with the SGSN of the UMTS network. The GGSN resolves the EGGSN IP address. The GGSN shall also maintain a mapping of the old IP address of the UE to the new IP address which is allocated during PDP context activation to the UE.

The GGSN establishes a tunnel with the EGGSN and obtains the packets destined to the UE that were buffered at the EGGSN as mentioned in step 4 above.
The SGSN then sends a PDP context activation complete message and forwards the buffered packets (obtained from the EGGSN) to the UE.
The SGSN then sends a trigger to the EGGSN to release the radio resources that were used/reserved for the UE. In order to avoid ping pong effect, the EGGSN could start a timer and release the resources after expiry of the timer.
The UE performs the MIP like binding update or MIP binding update with the Home Agent (HA) and the correspondent node (CN).
On obtaining the binding acknowledgement (BACK) from the CN, the UE sends a HO complete message to the serving SGSN.
The SGSN, in turn, intimates the EGGSN about the hand off completion by sending a HO confirm command. This command is a trigger for the EGGSN to release the IP address allocated to the UE in case there were no TCP sessions incident on the UE.
In case the UE does not have any incident TCP sessions and has IMS sessions incident on it, then the UE can avoid the MIP registration procedure and can perform a SIP update procedure.
Handover from the UMTS to the EUMTS access system
The optimization of the authentication procedure during the handover can be

performed by making the EGGSN obtain the UE security from the SGSN. In this mechanism we consider an interface between the SGSN and the EGGSN that uses the GTP-c or any other tunneling protocol.
For lossless handover, we propose buffering of the packets destined to the UE at the GGSN during the handover. The EGGSN needs to know the GGSN IP address to obtain the packets and forward then to the UE after the handover. The GGSN IP address can be obtained in any one of the following ways
• The SGSN can forward the GGSN IP address during the HO preparation phase
• The UE can mention the old IP address and RAI in the user plane (UP) set up procedure, using which the EGGSN can resolve the GGSN IP address
• The HSS can inform the GGSN IP address to the EGGSN
• The EGGSN can contact the HSS during the UP set up procedure and obtain the GGSN IP address
The procedure for UMTS to EUMTS handover is explained below.
• The SGSN takes the decision to handover the UE based on the signal strength measurements. The HO command is given to the UE, with the Cell ID of the EUMTS network to which to handover to. The SGSN also triggers the GGSN to buffer the packets destined to the UE. The GGSN starts buffering packets.
• The UE attaches to the given ENB. After the L2 attach, UE sends the first L3 message to the EGGSN, which could be the Routing Area Update (RAU) or any other equivalent message. On receipt of the RAU from the UE, the EGGSN can obtain the GGSN address in any one of the following ways:
1. Using the old IP address of the UE (if included in the RAU)
2. Through interaction with HSS
• User context is now transferred from SGSN to the EGGSN using GTP-C mechanism or through any other control plane protocol. The user context contains the information which can be used for authentication optimization.
• When the UE requests for User plane set up to activate the flows, EGGSN

forms a tunnel with GGSN through which the buffered packets are forwarded. Simultaneously, UP set up is also completed. The packets from the EGGSN are now forwarded through appropriate flows. • MIP Based mobility mechanism can be used for completing the mobility. After MIP procedures have been completed, the HO Complete message is sent, and the resources at the UMTS network are released.
An illustrative example of the handover procedure from UMTS access system to the EUMTS access system in this scenario is depicted in Figure 4. The description of the handover procedure is provided below:
The UE sends the UMTS measurement reports to the SGSN.
Based on the signal strength of UMTS or by other means, the SGSN requests the UE to scan the other RATs. UE start scanning the other RAT.
UE sends the EUMTS measurement reports to the SGSN and can request the SGSN for a handover to the EUMTS network or the SGSN can decide that the UE attach with the EUMTS AS.
The SGSN can optionally prepare the EGGSN for the impending handoff by sending a handoff request and the EGGSN, in turn, can prepare the target ENB.
On reserving the required radio and network resources, the EGGSN sends an HO accept message to the SGSN.
Upon receiving HO accept from the EGGSN, the SGSN issues a HO command to the UE and also in parallel, triggers the GGSN to buffer the packets destined to the UE. The GGSN then starts buffering the UE packets.

The UE establish L2/RRC connection with the EUMTS network. Then the UE send the RAU message or alternatively any initial L3 message after the L2 connection, including the HO preparation message containing the old RAI.
The EGGSN obtains the AV's from the SGSN. EGGSN updates the HSS about the new location of the UE.
The EGGSN allocates/assigns a new IP address to the UE while accepting the RA update
The UE performs a UP set up procedure in the EUTRAN network to activate the flows. The EGGSN maintains the mapping between the old IP address of the UE (in the UMTS domain) and the new IP address allocated by the EGGSN in the EUMTS domain.
The EGGSN obtains the GGSN IP address from the HSS.
The EGGSN establishes an IP Sec tunnel (or any other secure tunnel) with the GGSN and obtains the packets destined to the UE that were buffered at the GGSN as mentioned in step 6
.The UE may do MIP based route optimization procedure with the CN, if CN supports MIP and tunnel overhead is not considered to be disadvantage.
.The UE can intimate the release of IP to the EGGSN in the HO complete message.
The EGGSN relays the HO complete message to the GGSN, which, in turn, shall release the old IP address allocated to the UE in case there are no TCP sessions incident on the UE.

If no active TCP connections are present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.
Mechanism 2: Using AAA proxy functionality at the EGGSN and the SGSN
In this mechanism we describe a method for handover between EUMTS and UMTS access systems when the SGSN and the EGGSN has functionalities of the AAA proxy. In other words, we consider a scenario where the authentication in the EUMTS network is AAA based. We now describe the procedure for optimization of the authentication procedure during handover. It is noted that in this scenario, there is no interface between the SGSN and the EGGSN. The functions of the various network entities in this scenario are as follows:
• The SGSN of the legacy core network acts as an AAA proxy and obtains the UE security context from the AAA server.
• The GGSN acts as the IP gateway in the UMTS network and allocates IP address to the UE when the UE is served by the UMTS network.
• The EGGSN of the EUMTS network acts as an AAA proxy for the UE served by the EUMTS network. The EGGSN also acts as the IP gateway to the EUMTS network and allocates IP address to the UE when the UE is served by the EUMTS network.
• The ENB of the EUMTS network can be capable of converting the RRC protocol messages of the EUMTS to the RRC messages of the UMTS network and vice-versa.
Handover from the EUMTS to the UMTS Access System
For lossless handover, we propose buffering of the packets destined to the UE at the EGGSN during the handover. The GGSN needs to know the EGGSN IP

address to obtain the packets and forward then to the UE after the handover. The EGGSN IP address can be obtained in any one of the following ways
• The AAA server can forward the EGGSN IP address to the SGSN when the SGSN retrieves security context and the SGSN can forward the EGGSN IP address to the GGSN during the PDP context creation procedure
• The UE can mention the old IP address and RAI in the PDP context activation procedure, using which the GGSN can resolve the EGGSN IP address
• The HSS can inform the EGGSN IP address to the GGSN
• The GGSN can contact the HSS during the PDP context activation procedure and obtain the EGGSN IP address
The procedure for EUMTS to UMTS handover is explained below.
• The EGGSN takes the decision to handover the UE based on the signal strength measurements. The HO command is given to the UE, with the Cell ID of the UMTS network to which to handover to. The EGGSN also simultaneously starts buffering packets.
• The UE attaches to the given NodeB. After the L2 attach, UE sends the first L3 message to the SGSN. On receipt of the RAU from the UE, the SGSN resolves the AAA server ID.
• The SGSN can obtain the EGGSN address in any one of the following ways:
1. Using the old IP address of the UE (if included in the RAU)
2. Through interaction with HSS
3. Through GGSN which contacts HSS during the PDP context activation.
4. Through the AAA server while obtaining the UE security context information

• User context is now obtained from AAA server through any control plane protocol. The user context contains the information which can be used for authentication optimization.
• When the UE requests for PDP context, through PDP context Request procedure, the GGSN obtains the IP address of the EGGSN in any one of

the following ways:
1. SGSN forwards the EGGSN IP address to the GGSN
2. EGGSN IP address can be obtained by contacting the HSS.
• GGSN forms a tunnel with EGGSN through which the buffered packets are forwarded. Simultaneously, PDP context is also completed. The packets from the EGGSN are now forwarded through appropriate PDP contexts.
• After the formation of the PDP context, MIP Based mobility mechanism can be used for completing the mobility. After MIP procedures have been completed, the HO Complete message is sent, and the resources at the EUMTS network are released.
An illustrative example of the handover procedure from EUMTS access system to the UMTS access system in this scenario is depicted in Figure 5. The description of the handover procedure is provided below.
UE sends periodic or event based measurements to the ENB/EGGSN.
The EGGSN, on finding the EUMTS measurements unsatisfactory, can request the UE to scan other RATs. Alternatively by L2 or any other means the UE can decide that the EUMTS cannot be continued and starts scanning other RATs.
The UE sends measurements reports of UMTS network.
The EGGSN decides the target Node B and issues a HO command. Alternatively, the UE could specify the preferred target Node B and the EGGSN could issue HO command accepting the UE preferred target Node B. The EGGSN also starts buffering the UE packets before issuing the HO command.
The UE performs L2 attach procedure with the target UMTS network and the RAU with the corresponding SGSN. In the RAU, the UE mentions the

old RAI. The SGSN resolves the home AAA server identity using the old RAI and contacts the home AAA server to obtain the authentication vectors. The AAA also can mention the EGGSN IP address to the SGSN
Upon PDP context activation request from the UE, the SGSN chooses an appropriate GGSN and mentions the EGGSN IP address to the GGSN. This enables the GGSN to establish an IP Sec tunnel with the EGGSN and retrieve the buffered packets for the UE. The GGSN also maintains a mapping between the old IP address of the UE and the newly allocated IP address in the UMTS domain.
The GGSN establishes an IP Sec or any other secure tunnel with the EGGSN and obtains the buffered packets the EGGSN destined to the UE.
The buffered packets are delivered to the UE as part of completion of the PDP context activation procedure.
The SGSN triggers the EGGSN to release the resources used/reserved for the UE. To avoid ping pong effect a timer can be added to the EGGSN and release of resources can be made after expiry of the timer.
. The UE performs the MIP binding update with the CN, if CN supports MIP and tunnel overhead is not considered to be disadvantage.
.After successful MIP update procedure, the UE sends a HO complete message to the SGSN.
.The SGSN, in turn, forwards the message to the EGGSN triggering the release of the old IP address allocated to the UE in case there are no active TCP sessions incident on the UE using the old IP address.
. If no active TCP connections were present, then the UE can do SIP based

terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.
Handover from the UMTS to the EUMTS Access System
For lossless handover, we propose buffering of the packets destined to the UE at the GGSN during the handover. The EGGSN needs to know the GGSN IP address to obtain the packets and forward then to the UE after the handover. The GGSN IP address can be obtained in any one of the following ways
• The AAA server can forward the GGSN IP address to the EGGSN when the EGGSN retrieves security context
• The UE can mention the old IP address and RAI in the UP Set up procedure, using which the EGGSN can resolve the GGSN IP address
• The HSS can inform the GGSN IP address to the EGGSN
• The EGGSN can contact the HSS during the UP set up procedure and obtain the GGSN IP address
The procedure for UMTS to EUMTS handover is explained below.
• The SGSN takes the decision to handover the UE based on the signal strength measurements. The HO command is given to the UE, with the Cell ID of the EUMTS network to which to handover to. The SGSN also triggers the GGSN to buffer the packets destined to the UE. The GGSN starts buffering packets.
• The UE attaches to the given ENB. After the L2 attach, UE sends the first L3 message to the EGGSN, which could be the Routing Area Update (RAU) or any other equivalent message. On receipt of the RAU from the UE, the EGGSN resolves the AAA server ID.
• User context is now transferred from AAA server to the EGGSN using GTP-C mechanism or through any other control plane protocol. The user context contains the information which can be used for authentication optimization.
• The EGGSN can obtain the GGSN address in any one of the following ways:

1. Using the old IP address of the UE (if included in the RAU)
2. Through interaction with HSS
3. From the AAA server while obtaining the User context

• When the UE requests for User plane set up to activate the flows, EGGSN forms a tunnel with GGSN through which the buffered packets are forwarded. Simultaneously, UP set up is also completed. The packets from the EGGSN are now forwarded through appropriate flows.
• MIP Based mobility mechanism can be used for completing the mobility. After MIP procedures have been completed, the HO Complete message is sent, and the resources at the UMTS network are released.
An illustrative example of the handover procedure from UMTS access system to the EUMTS access system for Mechanism 2 is depicted in Figure 6. The description of the handover procedure is provided below.
UE sends periodic or event based measurements to the SGSN.
If the SGSN finds the UMTS measurements unsatisfactory, it requests the UE to scan other RATs. Alternatively, by L2 or any other means, the UE decides that the UMTS measurements are unsatisfactory and scans other RATs.
The UE sends the EUMTS measurement report to the SGSN specifying the ENB id. The SGSN decides the target ENB. Optionally, the UE can specify a preferred target ENB and the SGSN could accept the UE preferred ENB.
On deciding the target ENB, the SGSN can optionally send a HO request to the AAA server.
The AAA server, in turn, can assign a stateful IP address to the UE in the EUMTS network and include the IP address in the HO accept message.

Optionally, the AAA server could forward the HO request to the EGGSN enabling the EGGSN and ENB reserve resources for the UE as a preparation phase.
The SGSN then issues a HO command to the UE and also in parallel intimates the GGSN to buffer the packets destined for the UE.
The GGSN starts buffering packets destined to the UE.
The UE performs the L2 attach and RAU procedures in the EUMTS network. The UE mentions the old IP address and RAI in the RAU message.
The EGGSN retrieves the UE security context from the SGSN through the AAA server. The AAA server also intimates the GGSN IP address to the EGGSN, thus enabling the EGGSN establish a tunnel to the GGSN to retrieve the buffered packets for the UE.
.The EGGSN allocates/assigns IP address to the UE and sends an RAU accept to the UE including the new IP address.
.The UE performs a UP set up procedure with the EGGSN.
The EGGSN establishes a tunnel with the GGSN and retrieves the buffered packets destined for the UE.
The EGGSN also maintains a mapping between the old IP address of the UE and the new IP address and forwards the buffered packets to the UE.
The EGGSN sends a trigger to the SGSN to release the resources reserved/used for the UE in the UMTS network. To avoid ping pong effect, the SGSN maintains a timer and the resources are released after expiry of

the timer.
.The UE may do MIP based route optimization procedure with the CN, if CN supports MIP and tunnel overhead is not considered to be disadvantage.
. The UE can intimate the release of IP to the EGGSN in the HO complete message.
The EGGSN sends an HO complete message to the GGSN to release the old IP address if there were no active TCP sessions incident on the UE.
.. If no active TCP connections were present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.
Handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture
We now present the handover procedure between the EUMTS and UMTS access systems for the SAE/LTE architecture. We consider two scenarios:
a) The Inter AS MM acts analogous to the mobile IP home agent for the UE and tunnels downlink packets to the UE from the CN as well as uplink packets from the UE to the CN and there exists a trust relation between the Inter AS MM and all the access systems.
b) The Inter AS MM only assists in signaling and the IP gateways of the respective access systems act as the Home Agents for the UE.
Mechanism 3: Handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is analogous to the MIP Home

Agent
We first present the handover procedure between the EUMTS and UMTS access systems for the SAE/LTE architecture when the Inter AS MM acts like the HA for the UE. As mentioned earlier, the Inter AS MM also has a trust relation with the core network of each of the access systems. Further, the Inter AS MM is also considered to be capable of the following functions:
• Mapping the UMTS cell ID reported by the UE to the appropriate SGSN of the UMTS network.
• Mapping the cell ID of the EUMTS network to the appropriate EGGSN of the EUMTS network.
• Resolving the appropriate GGSN for the UE based on the APN specified by the UE.
We also consider the following up-gradations to the UMTS network
• The GGSN is up-graded and is considered capable of issuing a HO Initiate command to the SGSN over GTP-c.
• The SGSN is upgraded to understand the HO initiate command issued by the GGSN as well as to send an HO Response command in response to the HO Initiate Command
• The SGSN is also upgraded to send an Inter RAT HO command to the GGSN. The GGSN is upgraded to understand the above command and relay it to the Inter AS MM.
• The SGSN is also considered to be upgraded to be capable of passing UE security context information to the Inter AS MM through the GGSN and obtain the security context information from the Inter AS MM through the GGSN.
Handover from the EUMTS to the UMTS access system
We first present the handover procedure from the EUMTS to the UMTS access

system. The handover procedure for the EUMTS to UMTS AS handover is as explained below:
■ The EGGSN takes the handover decision based on the UE measurement reports and issues an Inter RAT HO command to the Inter AS MM including the UMTS cell ID, the User context, IMSI and APN.
■ The Inter AS MM resolves the appropriate SGSN from the UMTS cell ID and the GGSN from the APN and forwards an HO Initiate command to the GGSN including the SGSN ID.
■ The GGSN forwards the command to the SGSN and the SGSN can optionally prepare the RNC for the HO and radio and network resources can be reserved. After reserving radio resources, the SGSN sends an HO Response to the GGSN accepting the HO and the GGSN forwards this command to the Inter AS MM.
■ The Inter AS MM forwards the HO Response to the EGGSN, which sends an HO command and starts buffering the packets destined for the UE. In case Route Optimization (RO) is not supported, the Inter AS MM buffers the packets destined to the UE before forwarding the HO Response to the EGGSN.
■ The UE performs an L2 attach with the RNC and an RAU with the SGSN. Upon receiving the RAU message the SGSN requests the GGSN for the UE security context. The GGSN obtains the UE security context from the Inter AS MM. The UE security context contains information that enables optimization of the authentication procedure.
■ Upon PDP context activation request from the UE, the SGSN chooses the same GGSN from which it obtained the HO initiate command. If the SGSN chooses another GGSN then it needs to inform the Inter AS MM IP address to the GGSN. Upon successful establishment of the PDP context, the GGSN sends an HO complete message to the Inter AS MM.
■ The HO complete message is relayed to the EGGSN to enable release of resources in the EUMTS network.
■ The UE performs MIP update procedure with the Inter AS MM. This triggers

Inter AS MM to obtain the buffered packets at the EGGSN destined to the UE and forward the packets to the GGSN. In case RO is not supported, then the Inter AS MM directly forwards the buffered packets destined to the UE, to the GGSN.
An illustrative example of the handover flow diagram is depicted in Figure 7. The detailed procedure is as follows:
The UE sends the EUMTS measurement reports to the EGGSN.
Based on the signal strength of EUMTS the EGGSN requests the UE to scan other RATs. Alternatively, by L2 or by other means, the UE start scanning the other RATs.
The UE sends the measurement report of the UMTS AS to the EGGSN. This includes the UMTS RAN ID.
The EGGSN could decide to handover the UE to the UMTS AS or alternatively, the UE could request an HO to the UMTS AS. In either case, the EGGSN sends an Inter RAT HO request to the Inter AS MM indicating the cell ID of the UMTS network, the UE security context, the APN and the IMSI.
The Inter AS MM resolves the SGSN ID from the cell ID and the GGSN from the APN.
The Inter AS MM sends an HO Initiate command to the appropriate GGSN.
The GGSN relays the HO initiate command to the SGSN along with the IMSI.

The SGSN can optionally prepare the RNC for the impending handover. However, this requires translation of EUMTS RRC containers to the UMTS RRC containers. This function can performed at the ENB of the EUMTS and the RRC containers can be included in the Inter RAT HO request sent to the Inter AS MM, which, in turn, relays it to the SGSN through the GGSN in the HO Initiate command.
The RNC sends an HO response command accepting the handover.
On obtaining the response from the RNC, the SGSN relays the HO Response command to the GGSN.
The GGSN, in turn, relays the HO Response command to the Inter AS MM.
The Inter AS MM relays the response to the EGGSN.
Upon receiving the HO response, the EGGSN issues an HO command to the UE and starts buffering the UE packets. In case route optimization (RO) is not supported, then the buffering of packets is done at the Inter AS MM instep 12.
The UE performs an L2 establishment with the UMTS RNC.
The UE then performs an RA Update procedure with the SGSN. Based on the IMSI in the RAU message the SGSN sends a request to the GGSN to obtain the UE security context. The GGSN obtains the security context from the Inter AS MM and passes it to the SGSN.
Upon PDP context activation from the UE, the SGSN chooses the same GGSN from which it obtained the HO Initiate command for the UE.

However, if the SGSN chooses any other GGSN, then it needs to intimate the GGSN of the IP address of the Inter AS MM.
. Upon successful establishment of the PDP context, the GGSN sends an HO complete message to the Inter AS MM.
.The Inter AS MM relays the HO complete message to the EGGSN.
.The HO complete message triggers the EGGSN and ENB to release the network and radio resources allocated to the UE. Optionally, to avoid ping-pong effect, there can be a timer at the EGGSN and the release of the network and radio resources can be made after the expiry of the timer. The HO complete message can also be a trigger for the EGGSN to release the IP address allocated to the UE in case there are no active TCP sessions.
.The UE performs an MIP binding update with the Inter AS MM intimating the Inter AS MM of the new IP address. Also, if the CN supports MIP and tunnel over head is not considered a disadvantage then a BU is performed with the CN.
. Upon receiving the BU, the Inter AS MM forwards the buffered packets to the GGSN.
.In case RO is supported, then the Inter AS MM obtains the buffered packets from the EGGSN, changes the destination IP address to the new IP address of the UE, and forwards the packets to the GGSN.
If no active TCP connections are present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.

Handover from the UMTS to the EUMTS Access System
The handover procedure for the UMTS to EUMTS AS handover is as explained below:
■ The SGSN takes the handover decision based on the UE measurement reports and issues an Inter RAT HO command to the Inter AS MM through the GGSN including the EUMTS cell ID, the User context, IMSI and UE flow information.
■ The Inter AS MM resolves the appropriate EGGSN from the UMTS cell ID and the UE flow information and forwards an HO Initiate command to the EGGSN.
■ The EGGSN can optionally prepare the ENB for the HO and radio and network resources can be reserved. After reserving radio resources, the EGGSN sends an HO Response to the Inter AS MM accepting the HO.
■ The Inter AS MM forwards the HO Response to the GGSN, which forwards the HO response to the SGSN and starts buffering the packets destined to the UE. In case Route Optimization (RO) is not supported, the Inter AS MM buffers the packets destined to the UE before forwarding the HO Response to the GGSN.
■ The SGSN sends an HO command to the UE.
■ The UE performs an L2 attach with the ENB and an RAU or an equivalent initial L3 attach procedure with the EGGSN. Upon receiving the RAU message the EGGSN requests the Inter AS MM for the UE security context. The UE security context contains information that enables optimization of the authentication procedure.
■ Upon successful completion of the UP establishment procedure, the EGGSN sends an HO complete message to the Inter AS MM.
■ The HO complete message is relayed to the GGSN and the GGSN relays the message to the SGSN to enable release of resources in the UMTS network.

■ The UE performs MIP update procedure with the Inter AS MM. This triggers Inter AS MM to obtain the buffered packets at the GGSN destined to the UE and forward the packets to the EGGSN. In case RO is not supported, then the Inter AS MM directly forwards the buffered packets destined to the UE, to the EGGSN.
An illustrative example of the message flows/sequence for the UMTS to EUMTS handover is illustrated in Figure 8: The detailed description is as given below
The UE sends the UMTS measurement reports to the SGSN.
Based on the signal strength of UMTS the SGSN requests the UE to scan other RATs. Alternatively, by L2 or by other means, the UE start scanning the other RATs.
The UE sends the EUMTS measurement reports to the SGSN.
The SGSN decides to handover the UE to the EUMTS network or alternatively, the UE can request for handover to the EUMTS network. In either case, the SGSN sends an Inter RAT HO message to the GGSN including the UE security context, the EUMTS cell ID and the IMSI.
The GGSN relays the Inter RAT HO message to the Inter AS MM.
The Inter AS MM resolves the EGGSN ID from the cell ID. In case a single ENB can be connected to multiple EGGSN, the Inter AS MM can choose the EGGSN based on the flows incident on the UE.
The Inter AS MM sends an HO Initiate message to the EGGSN including the IMSI of the UE.
Optionally, the Inter RAT HO message from the SGSN can also contain

RRC specific containers, which the Inter AS MM can include in the HO Initiate message. Upon receiving the HO Initiate message, the EGGSN can prepare the ENB for the HO and radio as well as network resources can be reserved for the UE.
The ENB responds with an HO Response message accepting the handover.
The HO Response message from the EGGSN is relayed to the Inter AS MM.
The Inter AS MM relays the HO response message to the GGSN. If RO is not supported then the Inter AS MM also begins to buffer packets destined to the UE.
.The GGSN, upon receiving the HO response, relays the message to the SGSN and starts buffering the packets destined to the UE in case RO is supported.
.Upon receiving the HO Response from the GGSN, the SGSN issues an HO Command to the UE.
The UE performs an L2 attach with the ENB.
The UE performs an RAU or L3 attach with the EGGSN. From the IMSI obtained in the RAU, the EGGSN obtains the UE security context from the Inter AS MM.
The UE performs the user plane (UP) set up procedure for activating the flows.
After completion of the UP set up, the EGGSN sends an HO complete

message to the Inter AS MM.
The Inter AS MM, in turn, relays the HO complete message to the GGSN.
The HO complete message is relayed to the SGSN by the GGSN. The SGSN deletes the PDP context and releases the radio resources. Optionally, to avoid ping-pong effect, a time out can be added to the SGSN to delete the PDP context and release the radio resources. The HO complete message can also be a trigger for the GGSN to release the IP address allocated to the UE in case there are no active TCP sessions.
The UE performs an MIP update procedure with the Inter AS MM indicating the new IP address. If the CN supports MIP and tunneling overhead is not considered a disadvantage, then the UE also performs a BU with the CN.
Upon completion of the MIP update procedure, the Inter AS MM obtains the buffered UE packets from the GGSN, changes the destination IP address to the new UE IP address.
The Inter AS MM forwards the packets to the EGGSN. In case RO is not supported, then the Inter AS MM directly forwards the UE buffered packets to the EGGSN and step 21 does not exist.
If no active TCP connections are present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.
Handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and the IP gateway of the respective Access Systems act as Home Agents

We now present the handover procedures between the EUMTS and UTRAN access systems for the scenarios in which the Inter AS MM does not behave like an HA but only assists in signaling. Also, in this case, we consider no trust relationship between the Inter AS MM and the core networks of the respective AS. However, the Inter AS MM is considered to be capable of the following functions:
• Resolving SGSN ID from the UMTS cell ID and the EGGSN ID from the EUMTS cell ID.
• Resolving GGSN from APN.
• Resolving PDG from W-APN.
• Mapping the IMSI to the EGGSN or GGSN that acts as HA for the UE.
In this scenario also the UMTS network is considered to be upgraded as follows:
• The GGSN is up-graded and is considered capable of issuing a HO Initiate command to the SGSN over GTP-c.
• The SGSN is upgraded to understand the HO initiate command issued by the GGSN as well as to send an HO Response command in response to the HO Initiate Command
• The SGSN is also upgraded to send an Inter RAT HO command to the GGSN. The GGSN is upgraded to understand the above command and relay it to the Inter AS MM.
• The SGSN is also considered to be upgraded to be capable of passing UE security context information to the GGSN and obtain the security context information from the EGGSN through the GGSN.
We present two cases in this scenario
a) The EUMTS network is the home network of the UE. In this case, the EGGSN acts as the Home Agent for the UE.
b) The UMTS network is the home network of the UE. In this case, the GGSN acts as the Home Agent for the UE.
Mechanism 4: Handover between the EUMTS and UMTS Access Systems for

the SAE/LTE Architecture when Inter AS MM is used only for signaling and EGGSN acts as the Home Agent
We first present the handover mechanism when the EUMTS network is the home network of the UE and the EGGSN acts as the HA for the UE. Here, we first consider a UE moving from the EUMTS network to the UMTS network. From the UMTS network, we consider two more cases:
(i) UE moves from UMTS network to an l-WLAN network
(ii) UE moves from UMTS network back to the EUMTS network.
Handover from the EUMTS to the UMTS access system
The handover procedure for the EUMTS to UMTS handover when the EGGSN acts as the HA, is as explained below:
■ The EGGSN takes the handover decision based on the UE measurement reports and issues an Inter RAT HO command to the Inter AS MM including the UMTS cell ID, IMSI and APN.
■ The Inter AS MM resolves the appropriate SGSN from the UMTS cell ID and the GGSN from the APN and forwards an HO Initiate command to the GGSN including the SGSN ID and the EGGSN IP address.
■ The GGSN forwards the command to the SGSN and the SGSN can optionally prepare the RNC for the HO and radio and network resources can be reserved. After reserving radio resources, the SGSN sends an HO Response to the GGSN accepting the HO and the GGSN forwards this command to the Inter AS MM.
■ The Inter AS MM forwards the HO Response to the EGGSN, which sends an HO command and starts buffering the packets destined for the UE.
■ The UE performs an L2 attach with the RNC and an RAU with the SGSN. Upon receiving the RAU message the SGSN requests the GGSN for the UE security context. The GGSN obtains the UE security context from the EGGSN. The UE security context contains information that enables

optimization of the authentication procedure.
■ Upon PDP context activation request from the UE, the SGSN chooses the same GGSN from which it obtained the HO initiate command. In case the SGSN chooses another GGSN, then it needs to inform EGGSN IP address to the other GGSN. Upon successful establishment of the PDP context, the GGSN sends an HO complete message to the Inter AS MM.
■ The HO complete message is relayed to the EGGSN to enable release of resources in the EUMTS network.
■ The UE performs MIP update procedure with the EGGSN. This triggers the EGGSN to forward the buffered packets destined to the UE to the GGSN.
An illustrative example for the message flow/sequence for the EUMTS to UMTS network handover when the EGGSN acts as the HA, is illustrated in Figure 9. The detailed description of the procedure is as follows:
The UE sends the EUMTS measurement reports to the EGGSN.
Based on the signal strength of EUMTS the EGGSN requests the UE to scan other RATs. Alternatively, by L2 or by other means, the UE decides to start scanning the other RATs.
UE sends the measurement report of the UMTS AS to the EGGSN.
The EGGSN could decide to handover the UE to the UMTS AS or alternatively, the UE could request an HO to the UMTS AS. In either case, the EGGSN sends an Inter RAT HO request to the Inter AS MM indicating the cell ID of the UMTS network, the IMSI and the APN.
The Inter AS MM resolves the SGSN ID from the cell ID and the GGSN from the APN.
The Inter AS MM sends an HO Initiate command to the appropriate GGSN.

The Inter AS MM also includes the EGGSN IP address in the HO Initiate.
The GGSN relays the HO initiate command to the SGSN along with the IMSI.
The SGSN can optionally prepare the RNC for the impending handover. However, this requires translation of EUMTS RRC containers to the UMTS RRC containers. This functions can performed at the ENB of the EUMTS and the RRC containers can be included in the Inter RAT HO request sent to the Inter AS MM, which, in turn, relays it to the SGSN through the GGSN in the HO Initiate command.
. The RNC sends an HO response command to the SGSN accepting the HO.
On obtaining the response form the RNC, the SGSN relays the HO Response command to the GGSN.
The GGSN, in turn, relays it to the Inter AS MM.
The Inter AS MM relays the response to the EGGSN.
Upon receiving HO Response, the EGGSN issues an HO command to the UE and starts buffering the UE packets.
The UE performs an L2 attach with the UMTS RNC.
The UE performs an RAU procedure with the SGSN. Based on the IMSI in the RAU message the SGSN sends a request to the GGSN to obtain the UE security context. The GGSN obtains the security context from the EGGSN (since it obtains the EGGSN IP address from the Inter AS MM in the HO Initiate command) and passes it to the SGSN.

Upon PDP context activation from the UE, the SGSN chooses the same GGSN from which it obtained the HO Initiate command for the UE. However, if the SGSN chooses any other GGSN, then it needs to intimate the GGSN of the IP address of the EGGSN.
Upon successful establishment of the PDP context, the SGSN sends an HO complete message to the GGSN.
The GGSN relays the HO complete command to the Inter AS MM.
The Inter AS MM relays the HO complete message to the EGGSN.
The HO complete message triggers the EGGSN and ENB to release the network and radio resources allocated to the UE. Optionally, to avoid ping-pong effect, there can be a timer at the EGGSN and the release of the network and radio resources can be made after the expiry of the timer. The HO complete message can also be a trigger for the EGGSN to release the IP address allocated to the UE in case there are no active TCP sessions.
The UE performs an MIP binding update with the EGGSN intimating the EGGSN of the new IP address. Also, if the CN supports MIP and tunnel overhead is not considered a disadvantage then a BU is performed with the CN.
Upon receiving the BU, the EGGSN forwards the buffered packets to the GGSN by changing the destination address in the IP packets to the new IP address of the UE.
If no active TCP connections are present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and

can avoid the MIP based mobility procedure.
Handover from the UMTS Access System to the l-WLAN access system
The handover procedure for the UMTS to l-WLAN AS handover when the EGGSN acts as HA, is as explained below:
■ The SGSN takes the handover decision based on the UE measurement reports and issues an Inter RAT HO command to the GGSN including the WLAN ID, the UE security context, the NAI, IMSI and W-APN. The GGSN forwards the command including all parameters except the UE security context.
■ The Inter AS MM resolves the appropriate PDG from the W-APN and the UE flow information and forwards an HO Initiate command to the PDG including the GGSN IP address, WLAN ID and NAI.
■ The PDG can optionally prepare the AP for the HO and radio and network resources can be reserved. After reserving radio resources, the PDG sends an HO Response to the Inter AS MM accepting the HO.
■ The Inter AS MM forwards the HO Response to the GGSN and the EGGSN including the PDG IP address. The EGGSN starts buffering the packets destined to the UE. The GGSN forwards the HO response to the SGSN.
■ The SGSN sends an HO command to the UE.
■ The UE performs an L2 association with the AP and establishes an IP Sec tunnel with the PDG, which requests the GGSN for the UE security context. The UE security context contains information that enables optimization of the authentication procedure.
■ Upon successful completion of the tunnel establishment procedure and UE flow activation, the PDG sends an HO complete message to the Inter AS MM.
■ The HO complete message is relayed to the GGSN and the GGSN relays the message to the SGSN to enable release of resources in the UMTS network.

■ The UE performs MIP update procedure with the EGGSN. This triggers the EGGSN to forward the buffered packets destined to the UE to the PDG.
An illustrative example of the message flow/sequence for the UMTS network to l-WLAN network handover when the EGGSN acts as the HA, is illustrated in Figure 10. The detailed description of the procedure is as follows
The UE sends the UMTS measurement report to the SGSN. Based on the signal strength of UMTS the SGSN requests the UE to scan other RATs. Alternatively, by L2 or by other means, the UE decides to start scanning start scanning the other RATs.
The UE sends the l-WLAN measurement reports to the SGSN. The measurement reports include the WLAN ID, the Network Access Identifier (NAI) and the Wireless Access Point Name (W-APN) based on the flows incident on the UE.
The SGSN decides to handover the UE to the l-WLAN network or alternatively, the UE can request for handover to the l-WLAN network. In either case, the SGSN sends an Inter RAT HO message to the GGSN including the UE security context, the WLAN ID, the W-APN and the IMSI.
The GGSN relays this message including all parameters except the UE security context, to the Inter AS MM.
The Inter AS MM resolves the PDG from the W-APN
The Inter AS MM sends an HO Initiate command to the PDG indicating the GGSN IP address, the WLAN ID, the NAI and the EGGSN IP address. Optionally, the Inter RAT HO message from the SGSN can also contain RRC specific containers, which the Inter AS MM can include in the HO Initiate message.

Upon receiving the HO Initiate message, the PDG can prepare the AP for the HO by sending HO Prepare command, and radio as well as network resources can be reserved for the UE.
The AP responds with an HO Response accepting the HO.
.The HO Response message from the AP is relayed to the Inter AS MM by the PDG.
.The Inter AS MM forwards the HO Response command to the GGSN including the PDG IP address. The Inter AS MM, in parallel, also forwards the HO response message to the EGGSN. The EGGSN starts buffering the packets destined to the UE.
The GGSN relays the HO Response to the SGSN including the PDG IP address.
. Upon receiving the HO response, the SGSN issues an HO Command to the UE. The HO command message includes the PDG IP address
The UE performs an L2 association with the WLAN AP.
The UE establishes an IP Sec tunnel with the PDG. The PDG retrieves the UE security context from the SGSN through the GGSN.
After completion of the activating the flows, the PDG sends an HO complete message to the GGSN.
The GGSN, in turn, relays the HO complete to the SGSN.
.The SGSN deletes the PDP context and releases the radio resources.

Optionally, to avoid ping-pong effect, a timer can be added at the SGSN and the deletion of the PDP context and release of the radio resources can be made after expiry of the timer. The HO complete also triggers the GGSN to release the tunnel established with the EGGSN. If a timer is used, then the expiry of the timer triggers release of the tunnel between the GGSN and the EGGSN. The HO complete message can also be a trigger for the GGSN to release the IP address allocated to the UE in case there are no active TCP sessions.
The UE performs an MIP update procedure with the EGGSN indicating the new IP address. If the CN supports MIP and tunneling overhead is not considered a disadvantage, then the UE also performs a BU with the CN.
Upon completion of the MIP update procedure, the EGGSN forwards the buffered UE packets to the PDG by changing the destination IP address to the new UE IP address.
If no active TCP connections are present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.
Handover from the UMTS Access System to the EUMTS access system
The handover procedure for the UMTS to EUMTS AS handover when the EGGSN acts as HA, as explained below:
■ The SGSN takes the handover decision based on the UE measurement reports and issues an Inter RAT HO command to the GGSN including the EUMTS cell ID, the User context, IMSI and UE flow information. The GGSN forwards the command to the Inter AS MM including all the parameters except the UE security context.
■ The Inter AS MM resolves the appropriate EGGSN from the UMTS cell ID

and the UE flow information and forwards an HO Initiate command to the EGGSN including the GGSN IP address.
■ The EGGSN can optionally prepare the ENB for the HO and radio and network resources can be reserved. After reserving radio resources, the EGGSN starts buffering the packets destined to the UE and sends an HO Response to the Inter AS MM accepting the HO.
■ The Inter AS MM forwards the HO Response to the GGSN, which forwards the HO response to the SGSN.
■ The SGSN sends an HO command to the UE.
■ The UE performs an L2 attach with the ENB and an RAU or an equivalent initial L3 attach procedure with the EGGSN. Upon receiving the RAU message the EGGSN requests the GGSN for the UE security context. The UE security context contains information that enables optimization of the authentication procedure.
■ Upon successful completion of the UP establishment procedure, the EGGSN sends an HO complete message to the Inter AS MM.
■ The HO complete message is relayed to the GGSN and the GGSN relays the message to the SGSN to enable release of resources in the UMTS network.
■ The UE performs MIP update de-registration procedure with the EGGSN. This triggers the EGGSN to forward the buffered packets to the UE.
An illustrative example of the message flow/sequence for the UMTS network to EUMTS network handover when the EGGSN acts as the HA, is illustrated in Figure 11. The detailed description of the procedure is as follows
The UE sends the UMTS measurement reports to the SGSN.
Based on the signal strength of UMTS the SGSN requests the UE to scan other RATs. Alternatively, by L2 or by other means, the UE decides to start scanning the other RATs.

The UE sends the EUMTS measurement reports to the SGSN.
The SGSN decides to handover the UE to the EUMTS network or alternatively, the UE can request for handover to the EUMTS network. In either case, the SGSN sends an Inter RAT HO message to the GGSN including the UE security context, IMSI and the EUMTS cell ID.
The GGSN relays the Inter RAT HO message including all parameters except the UE security context, to the Inter AS MM.
The Inter AS MM resolves the EGGSN ID from the cell ID. In case there can be multiple EGGSN that can serve the same cell, then the Inter AS MM resolves the EGGSN from the UE flow information.
The Inter AS MM sends an HO Initiate command to the EGGSN indicating the GGSN IP address and the IMSI. Optionally, the Inter RAT HO message from the SGSN can also contain RRC specific containers, which the Inter AS MM can include in the HO Initiate message.
Upon receiving the HO Initiate message, the EGGSN can prepare the ENB for the HO by sending an HO Prepare command and radio resources as well as network resources can be reserved for the UE.
The ENB responds with an HO Response accepting the HO.
The EGGSN starts buffering the UE packets and sends an HO response to the Inter AS MM.
The Inter AS MM relays the HO Response message to the GGSN.
The GGSN, in turn, relays the HO Response command to the SGSN.

The SGSN, upon receiving the HO Response, issues an HO Command to theUE
The UE performs an L2 association with the ENB.
The UE performs an RAU with the EGGSN. The EGGSN retrieves the UE security context from the SGSN through the GGSN.
The UE performs the user plane (UP) set up procedure for activating the flows.
After completion of the UP set up, the EGGSN sends an HO complete message to the GGSN.
The GGSN, in turn, relays the HO Complete message to the SGSN.
The SGSN deletes the PDP context and releases the radio resources. Optionally, to avoid ping-pong effect, a timer can be added at the SGSN and the deletion of the PDP context and release of the radio resources can be made after expiry of the timer. The HO complete also triggers the GGSN to release the tunnel established with the EGGSN. If a timer is used, then the expiry of the timer triggers release of the tunnel between the GGSN and the EGGSN. The HO complete message can also be a trigger for the GGSN to release the IP address allocated to the UE in case there are no active TCP sessions.
The UE performs an MIP de-registration procedure with the EGGSN indicating that it is back in the home network. If the CN supports MIP and tunneling overhead is not considered a disadvantage, then the UE also performs a BU with the CN. Upon completion of the MIP update procedure, the EGGSN forwards the buffered UE packets by changing the destination IP address to the new UE IP address.

. If no active TCP connections are present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.
Mechanism 5: Handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when inter AS MM is used only for signaling and GGSN acts as the Home Agent
We first present the handover mechanism when the UMTS network is the home network of the UE and the GGSN acts as the HA for the UE. Here, we first consider a UE moving from the UMTS network to the EUMTS network. From the UMTS network, we consider two more cases:
(i) UE moves from EUMTS network to an l-WLAN network (ii) UE moves from EUMTS network back to the UMTS network.
Handover from the UMTS Access System to the EUMTS access system
The handover procedure for the UMTS to EUMTS AS handover when the GGSN acts as HA, as explained below:
■ The SGSN takes the handover decision based on the UE measurement reports and issues an Inter RAT HO command to the GGSN including the EUMTS cell ID, the User context, IMSI and UE flow information. The GGSN forwards the command to the Inter AS MM including all the parameters except the UE security context.
■ The Inter AS MM resolves the appropriate EGGSN from the UMTS cell ID and the UE flow information and forwards an HO Initiate command to the EGGSN including the GGSN IP address.
■ The EGGSN can optionally prepare the ENB for the HO and radio and network resources can be reserved. After reserving radio resources, the sends an HO Response to the Inter AS MM accepting the HO.

■ The Inter AS MM forwards the HO Response to the GGSN, which forwards the HO response to the SGSN and starts buffering packets destined to the UE.
■ The SGSN sends an HO command to the UE.
■ The UE performs an L2 attach with the ENB and an RAU or an equivalent initial L3 attach procedure with the EGGSN. Upon receiving the RAU message the EGGSN requests the GGSN for the UE security context. The UE security context contains information that enables optimization of the authentication procedure.
■ Upon successful completion of the UP establishment procedure, the EGGSN sends an HO complete message to the Inter AS MM.
■ The HO complete message is relayed to the GGSN and the GGSN relays the message to the SGSN to enable release of resources in the UMTS network.
■ The UE performs MIP update de-registration procedure with the GGSN. This triggers the GGSN to forward the buffered packets destined to the UE, to the EGGSN.
An illustrative example of the message flow/sequence for the UMTS network to EUMTS network handover when the GGSN acts as the HA, is illustrated in Figure 12. The detailed description of the procedure is as follows
The UE sends the UMTS measurement reports to the SGSN.
Based on the signal strength of UMTS the SGSN requests the UE to start scanning other RATs. Alternatively, by L2 or by other means, the UE decides to start scanning the other RATs.
The UE sends the EUMTS measurement reports to the SGSN.
The SGSN decides to handover the UE to the EUMTS network or alternatively, the UE can request for handover to the EUMTS network. In

either case, the SGSN sends an Inter RAT HO message to the GGSN including the UE security context, IMSI and the EUMTS cell ID.
The GGSN relays this message including all parameters except the UE security context, to the Inter AS MM.
The Inter AS MM resolves the EGGSN ID from the cell ID.
The Inter AS MM sends an HO Initiate command to the EGGSN indicating the GGSN IP address and the IMSI. Optionally, the Inter RAT HO message from the SGSN can also contain RRC specific containers, which the Inter AS MM can include in the HO Initiate message.
Upon receiving the HO Initiate message, the EGGSN can prepare the ENB for the HO by sending an HO Prepare command and radio resources as well as network resources can be reserved for the UE.
The ENB sends an HO Response command accepting the HO.
.The EGGSN relays the HO response to the Inter AS MM.
.The HO Response message from the EGGSN is relayed to the GGSN by the Inter AS MM.
.The GGSN buffers the packets destined to the UE and forwards the HO Response command to the SGSN.
. Upon receiving the HO response, the SGSN issues an HO Command to the UE.
The UE performs an L2 establishment with the ENB.

The UE performs an RAU with the EGGSN. The EGGSN retrieves the UE security context from the SGSN through the GGSN.
The UE performs the user plane (UP) set up procedure for activating the flows.
After completion of the UP set up, the EGGSN sends an HO complete message to the Inter AS MM.
The Inter AS MM forwards the HO Complete message to the GGSN.
The GGSN, in turn, relays the HO Complete message to the SGSN.
The SGSN deletes the PDP context and releases the radio resources. Optionally, to avoid ping-pong effect, a timer can be added at the SGSN and the deletion of the PDP context and release of the radio resources can be made after expiry of the timer. The HO complete message can also be a trigger for the GGSN to release the IP address allocated to the UE in case there are no active TCP sessions.
The UE performs an MIP update procedure with the GGSN indicating the new IP address. If the CN supports MIP and tunneling overhead is not considered a disadvantage, then the UE also performs a BU with the CN.
Upon completion of the MIP update procedure, the GGSN forwards the buffered UE packets to the EGGSN by changing the destination IP address to the new UE IP address.
If no active TCP connections are present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure

Handover from the EUMTS Access System to the l-WLAN access system
The handover procedure for the EUMTS to l-WLAN AS handover when the GGSN acts as HA, is as explained below:
■ The EGGSN takes the handover decision based on the UE measurement reports and issues an Inter RAT HO command to the Inter AS MM including the WLAN ID, the NAI, IMSI and W-APN.
■ The Inter AS MM resolves the appropriate PDG from the W-APN and the UE flow information and forwards an HO Initiate command to the PDG including the EGGSN IP address, WLAN ID and NAI.
• The PDG can optionally prepare the AP for the HO and radio and network resources can be reserved. After reserving radio resources, the PDG sends an HO Response to the Inter AS MM accepting the HO.
■ The Inter AS MM forwards the HO Response to the GGSN and the EGGSN including the PDG IP address. The GGSN starts buffering the packets destined to the UE.
■ The EGGSN sends an HO command to the UE.
■ The UE performs an L2 association with the AP and establishes an IP Sec tunnel with the PDG, which requests the EGGSN for the UE security context. The UE security context contains information that enables optimization of the authentication procedure.
■ Upon successful completion of the tunnel establishment procedure and UE flow activation, the PDG sends an HO complete message to the Inter AS MM.
■ The HO complete message is relayed to the EGGSN to enable release of resources in the EUMTS network.
■ The UE performs MIP update procedure with the GGSN. This triggers the GGSN to forward the buffered packets destined to the UE to the PDG.
An illustrative example for the message flow/sequence for the EUMTS network to l-WLAN network handover when the GGSN acts as the HA, is illustrated in Figure

The detailed description of the procedure is as follows
The UE sends the EUMTS measurement reports to the EGGSN.
Based on the signal strength of EUMTS the EGGSN requests the UE to scan other RATs. Alternatively, by L2 or by other means, the UE decides to start scanning the other RATs.
The UE sends the l-WLAN measurement reports to the EGGSN. The measurement reports include the WLAN ID, the Network Access Identifier (NAI) and the Wireless Access Point Name (W-APN) based on the flows incident on the UE.
The EGGSN decides to handover the UE to the l-WLAN network or alternatively, the UE can request for handover to the l-WLAN network. In either case, the EGGSN sends an Inter RAT HO message to the Inter AS MM including the WLAN ID, the W-APN the EGGSN IP address and the GGSN IP address.
The Inter AS MM resolves the PDG from the W-APN.
The Inter AS MM sends an HO Initiate command to the PDG indicating the GGSN IP address, the WLAN ID, the NAI and the EGGSN IP address. Optionally, the Inter RAT HO message from the EGGSN can also contain RRC specific containers, which the Inter AS MM can include in the HO Initiate message.
Upon receiving the HO Initiate message, the PDG can prepare the AP for the HO by sending an HO Prepare command and radio resources as well as network resources can be reserved for the UE.
The AP responds with an HO Response.

The HO Response message from the AP is sent to the Inter AS MM by the PDG.
i. The HO Response command from the PDG is relayed to the EGGSN by the Inter AS MM by including the PDG IP address. The Inter AS MM also sends the HO Response command to the GGSN, upon receiving which the GGSN starts buffering the packets for the UE.
Upon receiving the HO response, the EGGSN issues an HO Command to the UE. The HO command message includes the PDG IP address
The UE performs an L2 association with the WLAN AP.
The UE establishes an IP Sec tunnel with the PDG. The PDG retrieves the UE security context from the EGGSN.
After completion of the UE flow activation, the PDG sends an HO complete message to the Inter AS MM
The Inter AS MM, in turn, relays the HO complete message to the EGGSN.
The EGGSN releases the radio resources and network resources. Optionally, to avoid ping-pong effect, a timer can be added at the EGGSN and the release of the radio resources and network resources can be made after expiry of the timer. The HO complete also triggers the EGGSN to release the tunnel established with the GGSN. If a timer is used, then the expiry of the timer triggers release of the tunnel between the GGSN and the EGGSN. The HO complete message can also be a trigger for the EGGSN to release the IP address allocated to the UE in case there are no active TCP sessions.

The UE performs an MIP update procedure with the GGSN indicating the new IP address. If the CN supports MIP and tunneling overhead is not considered a disadvantage, then the UE also performs a BU with the CN.
Upon completion of the MIP update procedure, the GGSN forwards the buffered UE packets to the PDG by changing the destination IP address to the new UE IP address.
If no active TCP connections are present, then the UE can do SIP based terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.
Handover from the EUMTS Access System to the UMTS access system
The handover procedure for the EUMTS to UMTS handover when the EGGSN acts as the HA, is as explained below:
■ The EGGSN takes the handover decision based on the UE measurement reports and issues an Inter RAT HO command to the Inter AS MM including the UMTS cell ID, IMSI and APN.
■ The Inter AS MM resolves the appropriate SGSN from the UMTS cell ID and the GGSN from the APN and forwards an HO Initiate command to the GGSN including the SGSN ID and the EGGSN IP address.
■ The GGSN forwards the command to the SGSN and the SGSN can optionally prepare the RNC for the HO and radio and network resources can be reserved. After reserving radio resources, the SGSN sends an HO Response to the GGSN accepting the HO and the GGSN starts buffering the packets destined to the UE and forwards the HO Response command to the Inter AS MM.
■ The Inter AS MM forwards the HO Response to the EGGSN, which sends an HO Command to the UE.

■ The UE performs an L2 attach with the RNC and an RAU with the SGSN. Upon receiving the RAU message the SGSN requests the GGSN for the UE security context. The GGSN obtains the UE security context from the EGGSN. The UE security context contains information that enables optimization of the authentication procedure.
■ Upon PDP context activation request from the UE, the SGSN chooses the same GGSN from which it obtained the HO initiate command. Upon successful establishment of the PDP context, the GGSN sends an HO complete message to the Inter AS MM.
■ The HO complete message is relayed to the EGGSN to enable release of resources in the EUMTS network.
■ The UE performs MIP updated-registration procedure with the GGSN. This triggers the GGSN to forward the buffered packets to the UE.
An illustrative example of the message flow/sequence for the EUMTS network to UMTS network handover when the GGSN acts as the HA, is illustrated in Figure 14. The detailed description of the procedure is as follows
The UE sends the EUMTS measurement reports to the EGGSN.
Based on the signal strength of EUMTS, the EGGSN requests the UE to scan other RATs. Alternatively, by L2 or by other means, the UE decides to start scanning the other RATs.
The UE sends the measurement report of the UMTS AS to the EGGSN.
The EGGSN could decide to handover the UE to the UMTS AS or alternatively, the UE could request an HO to the UMTS AS. In either case, the EGGSN sends an Inter RAT HO request to the Inter AS MM indicating the cell ID of the UMTS network, the IMSI and the APN.
The Inter AS MM resolves the SGSN ID from the cell ID and GGSN from

the APN. The Inter AS MM knows the GGSN that acts as the HA. Hence if the active flows of the UE allow use of the GGSN acting as HA, then the Inter AS MM chooses the GGSN with HA functionality.
The Inter AS MM sends an HO Initiate command to the GGSN including the SGSN ID. The Inter AS MM also includes the EGGSN IP address in the HO Initiate.
The GGSN relays the HO initiate command to the SGSN along with the IMSI.
The SGSN can optionally prepare the RNC for the impending handover by sending an HO Prepare command. However, this requires translation of EUMTS RRC containers to the UMTS RRC containers. This functions can performed at the ENB of the EUMTS and the RRC containers can be included in the Inter RAT HO request sent to the Inter AS MM, which, in turn, relays it to the SGSN through the GGSN in the HO Initiate command.
The RNC responds with an HO Response accepting the HO.
On obtaining the response form the RNC, the SGSN relays the HO Response command to the GGSN.
The GGSN, in turn, relays the HO Response message to the Inter AS MM and starts buffering the UE packets.
The Inter AS MM relays the HO response to the EGGSN.
Upon receiving the HO Response, the EGGSN issues an HO command to the UE.
The UE performs an L2 establishment with the UMTS RNC.

The UE performs an RA Update procedure with the SGSN. Based on the IMSI in the RAU message the SGSN sends a request to the GGSN to obtain the UE security context. The GGSN obtains the security context from the EGGSN (since it obtains the EGGSN IP address from the Inter AS MM in the HO Initiate command) and passes it to the SGSN.
The UE performs the PDP context activation procedure. Upon PDP context activation from the UE, the SGSN chooses the same GGSN from which it obtained the HO Initiate command for the UE.
. Upon successful establishment of the PDP context, the GGSN sends an HO complete message to the Inter AS MM.
The Inter AS MM relays the HO complete message to the EGGSN.
The HO complete message triggers the EGGSN and ENB to release the network and radio resources allocated to the UE. Optionally, to avoid ping-pong effect, there can be a timer at the EGGSN and the release of the network and radio resources can be made after the expiry of the timer. The HO complete message can also be a trigger for the EGGSN to release the IP address allocated to the UE in case there are no active TCP sessions.
'.The UE performs an MIP de-registration procedure with the GGSN indicating that it is back in the home network. Also, if the CN supports MIP and tunnel overhead is not considered a disadvantage then a BU is performed with the CN. Upon receiving the BU, the GGSN forwards the buffered packets to the UE by changing the destination address in the IP packets to the new IP address of the UE.
. If no active TCP connections are present, then the UE can do SIP based

terminal mobility procedure, if it has any active IMS based sessions and can avoid the MIP based mobility procedure.
It will also be obvious to those skilled in the art that other control methods and apparatuses can be derived from the combinations of the various methods and apparatuses of the present invention as taught by the description and the accompanying drawings and these shall also be considered within the scope of the present invention. Further, description of such combinations and variations is therefore omitted above. It should also be noted that the host for storing the applications include but not limited to a microchip, microprocessor, handheld communication device, computer, rendering device or a multi function device.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.

GLOSSARY OF TERMS AND DEFINITIONS THEREOF
3GPP: 3rd Generation Partnership Project
AAA: Authentication, Authorization and Accounting
AP: Wireless Local Area Network (WLAN) Access Point
APN: Access Point Name
AS: Access System
AV: Authentication Vector
AuC: Authentication Center
BTS: Base Transceiver Station
BSC: Base Station Controller
CK: Ciphering Key
ENB: Evolving Node B
EUMTS: Evolving UMTS Terrestrial Radio Access Network
EGGSN: Evolving GGSN
GERAN: GSN EDGE Radio Access Network consisting of the BTS and BSC
GGSN: Gateway GPRS Support Node
GPRS: Generalized Packet Radio Services
HA: Home Agent, a router on a mobile node's home network that tunnels packets to
the mobile node while it is away from home.
HLR: Home Location Register
HO: Handover
HSS: Home Subscription Server
IMS: IP Multimedia Service
IK: Integrity Key
IP: Internet Protocol
IP Sec: Internet Protocol Security
IKEv2: Internet Key Exchange Protocol version 2,
Inter AS MM: Inter Access System Mobility Manager, an entity assisting in mobility
across access systems
l-WLAN: WLAN integrated with a 3GPP network allowing WLAN users to access
3GPP PS services

KSI: Key Set Identifier
L2: Layer 2
L3: Layer 3
MIP: Mobile Internet Protocol includes version 4 and version 6
MME: Mobility Management Entity
NAI: Network Address Identifier;
Node B: The base station in a UMTS network
PCRF: Policy and Charging Rules Function
PDG: Packet Data Gateway
PDP: Packet Data Protocol
QoS: Quality of Service
RAI: Routing Area Identity
RAT: Radio Access Technology
RAU: Routing Area Update
RNC: UMTS Radio Network Controller
RO: Route Optimization (in MIP)
RRC: Radio Resource Control
SGSN: Serving GPRS Support Node
UE: User Equipment
User terminal: the end user equipment e.g., the Mobile Station (MS) or User
Equipment (UE).
UMTS: Universal Mobile Telecommunication System
UPE: User Plane Entity. This combined with the MME can form the EGGSN
UTRAN: UMTS Terrestrial Radio Access Network consisting of the Node B and the
RNC.
W-APN: WLAN APN
WLAN 3GPP IP Access Network: Scenario 3 l-WLAN Network
WLAN AN: WLAN Access Network



WE CLAIM
1. A method for providing mobility between EUMTS and UMTS access systems
Using GTP-c between the SGSN and the EGGSN comprising the steps of:
(a) performing the authentication of the UE by the SGSN of the legacy core network;
(b) allocating IP address to the UE when the UE is served by the UMTS network by the GGSN which acts as the IP gateway;
(c) performing authentication in the EUMTS network by the EGGSN; and
(d) allocating IP address to the UE when the UE is served by the EUMTS network by the EGGSN which acts as the IP gateway;
where ENB of the EUMTS network is capable of converting the RRC protocol messages of the EUMTS network to the RRC messages of the UMTS network and vice-versa.
2. A method as claimed in claim 1 wherein for providing mobility between EUMTS and UMTS access systems a handover from the EUMTS to the UMTS access system is performed.
3. A method as claimed in claim 2 wherein optimization of the authentication procedure during the handover is performed by making the SGSN obtain the UE security from the EGGSN.
4. A method as claimed in claim 3 wherein buffering of the packets destined to the UE at the EGGSN during the handover is done for the lossless handover.
5. A method as claimed in claim 4 wherein the GGSN obtains the EGGSN IP address by any of the following steps:

(a) resolving the EGGSN IP address when the UE mentions the old IP address and RAI in the PDP context activation procedure;
(b) informing the EGGSN IP address by HSS to the GGSN;
(c) contacting and obtaining the HSS during the PDP context activation

procedure by GGSN.
6. A method as claimed in claim 2 wherein the EGGSN takes the decision to handover the UE based on the signal strength measurements.
7. A method as claimed in claim 6 wherein a HO command is given to the UE, with the Cell ID of the UMTS network where the EGGSN simultaneously starts buffering packets.
8. A method as claimed in claim 7 wherein UE sends a first L3 message to the SGSN after a L2 attach, when UE attaches to a Node.
9. A method as claimed in claim 8 wherein on receipt of the RAU from the UE, the SGSN obtains the EGGSN address in any one of the following ways:

(a) using the old IP address of the UE if included in the RAU;
(b) through interaction with HSS;
(c) through GGSN which contacts HSS during the PDP context activation.

10. A method as claimed in claim 9 wherein user context gets transferred from EGGSN using GTP-C mechanism where the user context contains the information which is used for authentication optimization.
11. A method as claimed in claim 10 wherein when the UE requests for PDP context, through PDP context Request procedure, the GGSN obtains the IP address of the EGGSN in any one of the following ways:

(a) SGSN forwarding the EGGSN IP address to the GGSN;
(b) EGGSN IP address obtained by contacting the HSS.
12. A method as claimed in claim 11 wherein GGSN forms a tunnel with EGGSN
through which the buffered packets are forwarded and simultaneously
completing PDP context where the packets from the EGGSN are forwarded
through appropriate PDP contexts.

13. A method as claimed in claim 12 wherein after the formation of the PDP context, MIP Based mobility mechanism is used for completing the mobility.
14. A method as claimed in claim 13 wherein after MIP procedures have been completed, the HO Complete message is sent, and the resources at the EUMTS network are released.
15. A method as claimed in claim 1 wherein during handover from the UMTS to the EUMTS access system the optimization of the authentication procedure is performed by making the EGGSN obtain the UE security from the SGSN.
16. A method as claimed in claim 15 wherein for lossless handover, buffering of the packets destined to the UE at the GGSN during the handover is performed and the EGGSN gets GGSN IP address to obtain the packets and forward them to the UE after the handover.
17. A method as claimed in claim 16 wherein the GGSN IP address is obtained in any one of the following ways:

(a) the SGSN forwarding the GGSN IP address during the HO preparation phase;
(b) resolving the GGSN IP address when the UE mentions the old IP address and RAI in the user plane (UP) set up procedure;
(c) the HSS informing the GGSN IP address to the EGGSN;
(d) the EGGSN contacting the HSS during the UP set up procedure and obtain the GGSN IP address.

18. A method as claimed in claim 15 wherein the procedure for UMTS to EUMTS handover involves the SGSN taking the decision to handover the UE based on the signal strength measurements.
19. A method as claimed in claim 15 wherein the HO command is given to the UE,

with the Cell ID of the EUMTS network to which to handover to where the SGSN triggers the GGSN to buffer the packets destined to the UE and the GGSN starts buffering packets.
20. A method as claimed in claim 15 wherein the UE attaches to the given ENB where after the L2 attach, UE sends the first L3 message to the EGGSN, which is the Routing Area Update (RAU) or an equivalent message.
21. A method as claimed in claim 15 wherein on receipt of the RAU from the UE, the EGGSN obtains the GGSN address in any one of the following ways:

(a) using the old IP address of the UE if included in the RAU;
(b) through interaction with HSS.

22. A method as claimed in claim 15 wherein user context is transferred from SGSN to the EGGSN using GTP-C mechanism where the user context contains the information which is used for authentication optimization.
23. A method as claimed in claim 15 wherein when the UE requests for User plane set up to activate the flows, EGGSN forms a tunnel with GGSN through which the buffered packets are forwarded and simultaneously, completing the UP set up where the packets from the EGGSN are forwarded through appropriate flows.
24. A method as claimed in claim 15 wherein MIP based mobility mechanism is used for completing the mobility where after MIP procedures have been completed, the HO Complete message is sent, and the resources at the UMTS network are released.
25. A method for providing mobility between EUMTS and UMTS access systems using AAA proxy functionality at the EGGSN and the SGSN comprising the steps of:
(a) obtaining the UE security context from a AAA server where the SGSN of

the legacy core network acts as an AAA proxy;
(b) allocating IP address to the UE when the UE is served by the UMTS network where GGSN acts as the IP gateway in the UMTS network; and
(c) allocating IP address to the UE when the UE is served by the EUMTS network by EGGSN which acts as IP gateway where the EGGSN of the EUMTS network acts as an AAA proxy for the UE served by the EUMTS network;
where ENB of the EUMTS network is capable of converting the RRC messages of the EUMTS to the RRC messages of the UMTS network and vice-versa.
26. A method as claimed in claim 25 wherein for lossless handover from the EUMTS to the UMTS, buffering of the packets destined to the UE at the EGGSN during the handover is performed where the GGSN needs the EGGSN IP address to obtain the packets and forward to the UE after the handover.
27. A method as claimed in claim 25 wherein the EGGSN IP address is obtained in any one of the following ways:

(a) the AAA server forwarding the EGGSN IP address to the SGSN when the SGSN retrieves security context and the SGSN forwards the EGGSN IP address to the GGSN during the PDP context creation procedure;
(b) the UE mentioning the old IP address and RAI in the PDP context activation procedure, using which the GGSN resolving the EGGSN IP address;
(c) the HSS informing the EGGSN IP address to the GGSN;
(d) the GGSN contacting the HSS during the PDP context activation procedure and obtaining the EGGSN IP address.
28. A method as claimed in claim 25 wherein the procedure for EUMTS to UMTS
handover comprises the steps of;
(a) the EGGSN taking the decision to handover the UE based on the signal strength measurements and giving the HO command to the UE, with the

Cell ID of the UMTS network to which to handover to and simultaneously starting buffering packets by EGGSN;
(b) the UE attaching to the given Node and after the L2 attach, UE sending the first L3 message to the SGSN where on receipt of the RAU from the UE, the SGSN resolves the AAA server ID;
(c) obtaining the EGGSN address by the SGSN;
(d) obtaining the user context from AAA server through a control plane protocol where the user context contains the information which is used for authentication optimization;
(e) obtaining the IP address of the EGGSN When the UE requests for PDP context, through PDP context Request procedure by GGSN;
(f) GGSN forming a tunnel with EGGSN through which the buffered packets are forwarded and simultaneously, completing the PDP context where the packets from the EGGSN are forwarded through appropriate PDP contexts; and
(g) using MIP Based mobility mechanism for completing the mobility after the formation of the PDP context where after MIP procedures have been completed, the HO Complete message is sent, and the resources at the EUMTS network are released.
29. A method as claimed in claim 28 wherein obtaining the IP address of the
EGGSN when the UE requests for PDP context, through PDP context Request
procedure by GGSN is performed in any one of the following ways:
(a) SGSN forwards the EGGSN IP address to the GGSN;
(b) EGGSN IP address can be obtained by contacting the HSS.
30. A method as claimed in claim 28 wherein the SGSN obtains the EGGSN
address in any one of the following ways:
(a) using the old IP address of the UE if included in the RAU;
(b) through interaction with HSS;
(c) through GGSN which contacts HSS during the PDP context activation;
(d) through the AAA server while obtaining the UE security context

information.
31. A method as claimed in claim 25 wherein lossless handover from the UMTS to the EUMTS Access System involves buffering of the packets destined to the UE at the GGSN during the handover where the EGGSN needs the GGSN IP address to obtain the packets and forward to the UE after the handover.
32. A method as claimed in claim 31 wherein the GGSN IP address is obtained in any one of the following ways:

(a) the AAA server forwarding the GGSN IP address to the EGGSN when the EGGSN retrieves security context;
(b) the UE mentioning the old IP address and RAI in the UP Set up procedure, using which the EGGSN resolving the GGSN IP address;
(c) the HSS informing the GGSN IP address to the EGGSN;
(d) the EGGSN contacting the HSS during the UP set up procedure and obtaining the GGSN IP address.
33. A method as claimed in claim 31 wherein the procedure for UMTS to EUMTS
handover comprise the steps of:
(a) the SGSN taking the decision to handover the UE based on the signal strength measurements and giving HO command to the UE, with the Cell ID of the EUMTS network to which to handover to where the SGSN triggers the GGSN to buffer the packets destined to the UE and the GGSN starts buffering packets;
(b) the UE attaching to the given ENB and after the L2 attach, UE sending the first L3 message to the EGGSN, which is the Routing Area Update (RAU) or any equivalent message where on receipt of the RAU from the UE, the EGGSN resolves the AAA server ID;
(c) transferring the user context from AAA server to the EGGSN using GTP-C mechanism or through other control plane protocol where the user context contains the information which is used for authentication optimization;
(d) obtaining the GGSN address by the EGGSN;

(e) EGGSN forming a tunnel with GGSN through which the buffered packets are forwarded when the UE requests for User plane set up to activate the flows simultaneously, completing the UP set up and forwarding the packets from the EGGSN through appropriate flows; and
(f) using the MIP Based mobility mechanism for completing the mobility and after MIP procedures have been completed, the HO Complete message is sent, and the resources at the UMTS network are released.
34. A method as claimed in claim 33 wherein the EGGSN obtains the GGSN
address in any one of the following ways:
(a) using the old IP address of the UE if included in the RAU;
(b) through interaction with HSS;
(c) from the AAA server while obtaining the User context.
35. A method for providing mobility between EUMTS and UMTS access systems
where the handover between the EUMTS and UMTS Access Systems for the
SAE/LTE Architecture is performed when Inter AS MM is analogous to the MIP
Home Agent, where the Inter AS MM is capable of:
(a) mapping the UMTS cell ID reported by the UE to the appropriate SGSN of the UMTS network;
(b) mapping the cell ID of the EUMTS network to the appropriate EGGSN of the EUMTS network;
(c) resolving the appropriate GGSN for the UE based on the APN specified by the UE;
where the upgradations of the UMTS network is performed where the said upgradation involves:
(d) upgradation of the GGSN and considering it capable of issuing a HO Initiate command to the SGSN over GTP-c;
(e) upgradation of the SGSN to understand the HO initiate command issued by the GGSN and send an HO Response command in response to the HO Initiate Command;
(f) upgrading the SGSN to send an inter RAT HO command to the GGSN

Where the GGSN is upgraded to understand the above command and relay it to the Inter AS MM; and (g) upgrading the SGSN to be capable of passing UE security context information to the Inter AS MM through the GGSN and obtain the security context information from the Inter AS MM through the GGSN.
36. A method as claimed in claim 35 wherein a handover from the EUMTS to the UMTS access system involves the steps of:
(a) the EGGSN taking the handover decision based on the UE measurement reports and issuing an Inter RAT HO command to the Inter AS MM including the UMTS cell ID, the User context, IMSI and APN;
(b) the Inter AS MM resolving the appropriate SGSN from the UMTS cell ID and the GGSN from the APN and forwarding an HO Initiate command to the GGSN including the SGSN ID;
(c) the GGSN forwarding the command to the SGSN and the SGSN optionally preparing the RNC for the HO and radio and network resources reservation where after reserving radio resources, the SGSN sends an HO Response to the GGSN accepting the HO and the GGSN forwards the command to the Inter AS MM;
(d) the inter AS MM forwarding the HO Response to the EGGSN, which sends an HO command and starts buffering the packets destined for the UE where in case of Route Optimization (RO) is not supported, the Inter AS MM buffers the packets destined to the UE before forwarding the HO Response to the EGGSN;
(e) the UE performs an L2 attach with the RNC and an RAU with the SGSN and upon receiving the RAU message the SGSN requests the GGSN for the UE security context where the GGSN obtains the UE security context from the Inter AS MM and the UE security context contains information that enables optimization of the authentication procedure;
(f) the SGSN choosing the same GGSN from which SGSN obtained the HO initiate command and upon PDP context activation request from the UE if the SGSN chooses another GGSN then it inform the Inter AS MM IP address to

the GGSN were upon successful establishment of the PDP context, the GGSN sends an HO complete message to the Inter AS MM;
(g) the HO complete message relayed to the EGGSN to enable release of resources in the EUMTS network; and
(h) the UE performing MIP update procedure with the Inter AS MM which triggers Inter AS MM to obtain the buffered packets at the EGGSN destined to the UE and forwarding the packets to the GGSN where in case RO is not supported, then the Inter AS MM directly forwards the buffered packets destined to the UE, to the GGSN.
37. A method as claimed in claim 35 wherein the handover from the UMTS to the EUMTS Access System involves the steps of:
(a) the SGSN taking the handover decision based on the UE measurement reports and issuing an Inter RAT HO command to the Inter AS MM through the GGSN including the EUMTS cell ID, the User context, IMSI and UE flow information;
(b) the Inter AS MM resolving the appropriate EGGSN from the UMTS cell ID and the UE flow information and forwarding an HO Initiate command to the EGGSN;
(c) the EGGSN optionally preparing the ENB for the HO and reserving radio and network resources where after reserving radio resources, the EGGSN sends an HO Response to the Inter AS MM accepting the HO;
(d) the Inter AS MM forwarding the HO Response to the GGSN, which forwards the HO response to the SGSN and starting buffering the packets destined to the UE where in case Route Optimization (RO) is not supported, the Inter AS MM buffers the packets destined to the UE before forwarding the HO Response to the GGSN;
(e) the SGSN sending an HO command to the UE;
(f) the UE performs an L2 attach with the ENB and an RAU or an equivalent initial L3 attach procedure with the EGGSN and upon receiving the RAU message the EGGSN requests the Inter AS MM for the UE security context where the UE security context contains information that enables optimization

of the authentication procedure; (g) the EGGSN sending an HO complete message to the Inter AS MM upon
successful completion of the UP establishment procedure; (h) the HO complete message relayed to the GGSN and the GGSN relays the
message to the SGSN to enable release of resources in the UMTS network;
and (i) the UE performing MIP update procedure with the Inter AS MM which
triggers Inter AS MM to obtain the buffered packets at the GGSN destined to
the UE and forward the packets to the EGGSN where in case RO is not
supported, then the Inter AS MM directly forwards the buffered packets
destined to the UE, to the EGGSN.
38. A method for providing mobility between EUMTS and UMTS access systems involves the Handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and the IP gateway of the respective Access Systems act as Home Agents where the Inter AS MM is considered to be capable of:
(a) resolving SGSN ID from the UMTS cell ID and the EGGSN ID from the EUMTS cell ID;
(b) resolving GGSN from APN;
(c) resolving PDG from W-APN; and
(d) mapping the IMSI to the EGGSN or GGSN that acts as HA for the UE
where the upgradations of the UMTS network is performed where the said
upgradation involves:
(e) up-grading the GGSN where the GGSN is considered capable of issuing a HO Initiate command to the SGSN over GTP-c;
(f) up-grading the SGSN to understand the HO initiate command issued by the GGSN as well as to send an HO Response command in response to the HO Initiate Command;
(9) up-grading the SGSN to send an inter RAT HO command to the GGSN where the GGSN is upgraded to understand the above command and relay it to the Inter AS MM; and

(h) up-grading the SGSN to consider the SGSN capable of passing UE security context information to the GGSN and obtain the security context information from the EGGSN through the GGSN.
39. A method as claimed in claim 38 wherein when the EUMTS network is the home network of the UE, the EGGSN acts as the Home Agent for the UE.
40. A method as claimed in claim 38 wherein when the UMTS network is the home network of the UE, the GGSN acts as the Home Agent for the UE.
41. A method for providing mobility between EUMTS and UMTS access systems involves the handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and EGGSN acts as the Home Agent where UE moving from the EUMTS network to the UMTS network or UE moves from UMTS network to an l-WLAN network or UE moves from UMTS network back to the EUMTS network.
42. A method as claimed in claim 41 wherein the handover procedure for the EUMTS to UMTS handover when the EGGSN acts as the HA, involves:

(a) the EGGSN taking the handover decision based on the UE measurement reports and issuing an Inter RAT HO command to the Inter AS MM including the UMTS cell ID, IMSI and APN;
(b) the Inter AS MM resolving the appropriate SGSN from the UMTS cell ID and the GGSN from the APN and forwards an HO Initiate command to the GGSN including the SGSN ID and the EGGSN IP address;
(c) the GGSN forwarding the command to the SGSN and the SGSN optionally preparing the RNC for the HO and reserving radio and network resources and after reserving radio resources, the SGSN sends an HO Response to the GGSN accepting the HO and the GGSN forwarding the command to the Inter AS MM;
(d) the Inter AS MM forwarding the HO Response to the EGGSN, which sends an HO command and starts buffering the packets destined for the UE;

(e) the UE performing an L2 attach with the RNC and an RAU with the SGSN and upon receiving the RAU message the SGSN requests the GGSN for the UE security context where the GGSN obtains the UE security context from the EGGSN and the UE security context contains information that enables optimization of the authentication procedure;
(f) the SGSN choosing the same GGSN from which SGSN obtained the HO initiate command Upon PDP context activation request from the UE and in case the SGSN chooses another GGSN, then SGSN needs to inform EGGSN IP address to the other GGSN where upon successful establishment of the PDP context, the GGSN sends an HO complete message to the Inter AS MM;
(g) the HO complete message relayed to the EGGSN to enable release of resources in the EUMTS network; and
(h) the UE performing MIP update procedure with the EGGSN which triggers the EGGSN to forward the buffered packets destined to the UE to the GGSN.
43. A method as claimed in claim 41 wherein Handover from the UMTS Access System to the l-WLAN access system involves:
(a) the SGSN taking the handover decision based on the UE measurement reports and issuing an Inter RAT HO command to the GGSN including the WLAN ID, the UE security context, the NAI, IMSI and W-APN where the GGSN forwards the command including all parameters except the UE security context;
(b) the inter AS MM resolving the appropriate PDG from the W-APN and the UE flow information and forwarding an HO Initiate command to the PDG including the GGSN IP address, WLAN ID and NAI;
(c) the PDG optionally preparing the AP for the HO and reserving radio and network resources and after reserving radio resources, the PDG sends an HO Response to the Inter AS MM accepting the HO;
(d) the inter AS MM forwarding the HO Response to the GGSN and the EGGSN including the PDG IP address where the EGGSN starts buffering the packets destined to the UE where the GGSN forwards the HO response to the SGSN

and the SGSN sends an HO command to the UE;
(e) the UE performing an L2 association with the AP and establishes an IP Sec tunnel with the PDG, which requests the GGSN for the UE security context where the UE security context contains information that enables optimization of the authentication procedure;
(f) the PDG sending an HO complete message to the Inter AS MM upon successful completion of the tunnel establishment procedure and UE flow activation;
(g) the HO complete message is relayed to the GGSN and the GGSN relays the message to the SGSN to enable release of resources in the UMTS network; and
(h) the UE performing MIP update procedure with the EGGSN which triggers the EGGSN to forward the buffered packets destined to the UE to the PDG.
44. A method as claimed in claim 41 wherein the handover from the UMTS Access System to the EUMTS access system when the EGGSN acts as HA, involves:
(a) the SGSN taking the handover decision based on the UE measurement reports and issuing an Inter RAT HO command to the GGSN including the EUMTS cell ID, the User context, IMSI and UE flow information where the GGSN forwards the command to the Inter AS MM including all the parameters except the UE security context;
(b) the Inter AS MM resolving the appropriate EGGSN from the UMTS cell ID and the UE flow information and forwards an HO Initiate command to the EGGSN including the GGSN IP address;
(c) the EGGSN optionally preparing the ENB for the HO and reserving radio and network resources and after reserving radio resources, the EGGSN starts buffering the packets destined to the UE and sends an HO Response to the Inter AS MM accepting the HO;
(d) the Inter AS MM forwarding the HO Response to the GGSN, which forwards the HO response to the SGSN;
(e) the SGSN sending an HO command to the UE;
(f) the UE performing an L2 attach with the ENB and an RAU or an equivalent

initial L3 attach procedure with the EGGSN and upon receiving the RAU
message the EGGSN requests the GGSN for the UE security context where
the UE security context contains information that enables optimization of the
authentication procedure; (g) the EGGSN sends an HO complete message to the Inter AS MM upon
successful completion of the UP establishment procedure; (h) the HO complete message relayed to the GGSN and the GGSN relays the
message to the SGSN to enable release of resources in the UMTS network;
and (i) the UE performing MIP update de-registration procedure with the EGGSN
which triggers the EGGSN to forward the buffered packets to the UE.
45. A method for providing mobility between EUMTS and UMTS access systems involving handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture when Inter AS MM is used only for signaling and GGSN acts as the Home Agent where UE moving from the UMTS network to the EUMTS network or UE moves from EUMTS network to an l-WLAN network or UE moves from EUMTS network back to the UMTS network.
46. A method as claimed in claim 45 wherein the handover from the UMTS Access System to the EUMTS access system when the GGSN acts as HA, involves:

(a) the SGSN taking the handover decision based on the UE measurement reports and issuing an Inter RAT HO command to the GGSN including the EUMTS cell ID, the User context, IMSI and UE flow information where the GGSN forwards the command to the Inter AS MM including all the parameters except the UE security context;
(b) the Inter AS MM resolving the appropriate EGGSN from the UMTS cell ID and the UE flow information and forwarding an HO Initiate command to the EGGSN including the GGSN IP address;
(c) the EGGSN optionally preparing the ENB for the HO and reserving radio and network resources and after reserving radio resources, sending an HO Response to the Inter AS MM accepting the HO;

(d) the Inter AS MM forwarding the HO Response to the GGSN, which forwards the HO response to the SGSN and starts buffering packets destined to the UE;
(e) the SGSN sending an HO command to the UE;
(f) the UE performing an L2 attach with the ENB and an RAU or an equivalent initial L3 attach procedure with the EGGSN and upon receiving the RAU message the EGGSN requests the GGSN for the UE security context where the UE security context contains information that enables optimization of the authentication procedure;
(g) the EGGSN sending an HO complete message to the inter AS MM upon successful completion of the UP establishment procedure;
(h) the HO complete message relayed to the GGSN and the GGSN relays the
message to the SGSN to enable release of resources in the UMTS network;
and (i) the UE performing MIP update de-registration procedure with the GGSN and
triggering the GGSN to forward the buffered packets destined to the UE, to
the EGGSN.
47. A method as claimed in claim 45 wherein the handover from the EUMTS Access System to the l-WLAN access system when the GGSN acts as HA, involves:
(a) the EGGSN taking the handover decision based on the UE measurement reports and issuing an Inter RAT HO command to the Inter AS MM including the WLAN ID, the NAI, IMSI and W-APN;
(b) the Inter AS MM resolving the appropriate PDG from the W-APN and the UE flow information and forwarding an HO Initiate command to the PDG including the EGGSN IP address, WLAN ID and NAI;
(c) the PDG optionally preparing the AP for the HO and reserving the radio and network resources and after reserving radio resources, the PDG sends an HO Response to the Inter AS MM accepting the HO;
(d) the Inter AS MM forwarding the HO Response to the GGSN and the EGGSN including the PDG IP address where the GGSN starts buffering the packets destined to the UE;

(e) the EGGSN sending an HO command to the UE;
(f) the UE performing an L2 association with the AP and establishing an IP Sec tunnel with the PDG, which requests the EGGSN for the UE security context where the UE security context contains information that enables optimization of the authentication procedure;
(g) the PDG sending an HO complete message to the Inter AS MM upon successful completion of the tunnel establishment procedure and UE flow activation;
(h) the HO complete message relayed to the EGGSN to enable release of
resources in the EUMTS network; and (i) the UE performing MIP update procedure with the GGSN where and triggers
the GGSN to forward the buffered packets destined to the UE to the PDG.
48. A method as claimed in claim 45 wherein the handover from the EUMTS Access System to the UMTS access system when the EGGSN acts as the HA, involves:
(a) the EGGSN taking the handover decision based on the UE measurement reports and issuing an Inter RAT HO command to the Inter AS MM including the UMTS cell ID, IMSI and APN;
(b) the Inter AS MM resolving the appropriate SGSN from the UMTS cell ID and the GGSN from the APN and forwarding an HO Initiate command to the GGSN including the SGSN ID and the EGGSN IP address;
(c) the GGSN forwarding the command to the SGSN and the SGSN optionally preparing the RNC for the HO and reserving the radio and network resources and after reserving radio resources, the SGSN sends an HO Response to the GGSN accepting the HO and the GGSN starts buffering the packets destined to the UE and forwards the HO Response command to the Inter AS MM;
(d) the Inter AS MM forwarding the HO Response to the EGGSN, which sends an HO Command to the UE;
(e) the UE performing an L2 attach with the RNC and an RAU with the SGSN and upon receiving the RAU message the SGSN requests the GGSN for the UE security context and the GGSN obtains the UE security context from the

EGGSN where the UE security context contains information that enables optimization of the authentication procedure;
(f) the SGSN choosing the same GGSN from which the SGSN obtains the HO initiate command upon PDP context activation request from the UE and upon successful establishment of the PDP context, the GGSN sends an HO complete message to the Inter AS MM;
(g) the HO complete message relayed to the EGGSN to enable release of resources in the EUMTS network; and
(h) the UE performing MIP updated-registration procedure with the GGSN which triggers the GGSN to forward the buffered packets to the UE.
49. A system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and UMTS access systems is performed when the SGSN communicates with the EGGSN using the GTP-c protocol.
50. A system for providing mobility between EUMTS and UMTS access systems wherein handover between EUMTS and UMTS access systems is performed when the SGSN and the EGGSN has functionalities of the AAA proxy.
51. A system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture is performed when Inter AS MM is analogous to the MIP Home Agent.
52. A system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and UMTS Access Systems for the SAE/LTE Architecture is performed when Inter AS MM is used only for signaling and the IP gateway of the respective Access Systems act as Home Agents.
53. A system for providing mobility between EUMTS and UMTS access systems wherein handover between the EUMTS and UMTS Access Systems for the

SAE/LTE Architecture is performed when Inter AS MM is used only for signaling and EGGSN acts as the Home Agent.
54. A system for providing mobility between EUMTS and UMTS access systems
wherein handover between the EUMTS and UMTS Access Systems for the
SAE/LTE Architecture is performed when Inter AS MM is used only for signaling
and GGSN acts as the Home Agent.
55. A method for providing mobility between EUMTS and UMTS access systems
substantially explained with respect to the accompanied drawings.
56. A system for providing mobility between EUMTS and UMTS access systems
substantially explained with respect to the accompanied drawings.

Documents:

1779-CHE-2005 EXAMINATION REPORT REPLY RECEIVED 08-03-2013.pdf

1779-CHE-2005 AMENDED CLAIMS 08-03-2013.pdf

1779-CHE-2005 AMENDED PAGES OF SPECIFICATION 08-03-2013.pdf

1779-CHE-2005 FORM-1 08-03-2013.pdf

1779-CHE-2005 FORM-13 08-03-2013.pdf

1779-CHE-2005 FORM-13 19-06-2006.pdf

1779-CHE-2005 OTHER PATENT DOCUMENT 08-03-2013.pdf

1779-CHE-2005 POWER OF ATTORNEY 08-03-2013.pdf

1779-che-2005-abstract.pdf

1779-che-2005-claims.pdf

1779-che-2005-correspondnece-others.pdf

1779-che-2005-description(complete).pdf

1779-che-2005-description(provisional).pdf

1779-che-2005-drawings.pdf

1779-che-2005-form 1.pdf

1779-che-2005-form 13.pdf

1779-che-2005-form 26.pdf

1779-che-2005-form 5.pdf


Patent Number 255972
Indian Patent Application Number 1779/CHE/2005
PG Journal Number 15/2013
Publication Date 12-Apr-2013
Grant Date 10-Apr-2013
Date of Filing 05-Dec-2005
Name of Patentee SAMSUNG INDIA SOFTWARE OPERATIONS PRIVATE LIMITED
Applicant Address BAGMANE LAKEVIEW, BLOCK B, NO.66/1, BAGMANE TECH PARK, CV RAMAN NAGAR, BYRASANDRA, BANGALORE-560 093.
Inventors:
# Inventor's Name Inventor's Address
1 ANAND SANTHANA KRISHNAN EMPLOYED AT SAMSUNG ELECTRONICS CO. LTD., INDIA SOFTWARE OPERATIONS (SISO) J.P. TECHNO PARK, 3/1 MILLERS ROAD, BANGLORE
2 R. RAJAVELSAMY EMPLOYED AT SAMSUNG ELECTRONICS CO. LTD., INDIA SOFTWARE OPERATIONS (SISO) J.P. TECHNO PARK, 3/1 MILLERS ROAD, BANGLORE 560 052, KARNATAKA, INIDA
3 RAHUL SUHAS VAIDYA EMPLOYED AT SAMSUNG ELECTRONICS CO. LTD., INDIA SOFTWARE OPERATIONS (SISO) J.P. TECHNO PARK, 3/1 MILLERS ROAD, BANGLORE 560 052, KARNATAKA, INIDA
4 JEEDIGUNTA VENATESWAR EMPLOYED AT SAMSUNG ELECTRONICS CO. LTD., INDIA SOFTWARE OPERATIONS (SISO) J.P. TECHNO PARK, 3/1 MILLERS ROAD, BANGLORE 560 052, KARNATAKA, INIDA
5 OSOK SONG EMPLOYED AT SAMSUNG ELECTRONICS CO. LTD., INDIA SOFTWARE OPERATIONS (SISO) J.P. TECHNO PARK, 3/1 MILLERS ROAD, BANGLORE 560 052, KARNATAKA, INIDA
6 sungho choi EMPLOYED AT SAMSUNG ELECTRONICS CO. LTD., INDIA SOFTWARE OPERATIONS (SISO) J.P. TECHNO PARK, 3/1 MILLERS ROAD, BANGLORE 560 052, KARNATAKA, INIDA
PCT International Classification Number H04Q7/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA