Abstract:
A method where a first type location area of a mobile node is registered to a first mobility management node. A second type location area is determined based on a location of the mobile node. A second type location area of the mobile node is registered to a second mobility management node of a second system. A request to perform user plane bearer establishment through the second system is received. Thereupon, radio measurements associated with at least two candidate cells are obtained from the mobile node. Candidate cells are searched to find at least one cell associated with the second type location area. A cell is selected among the at least one cell, which is indicated to the selected cell to the mobile node. A handover request is provided to the mobile node.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to mobile communications comprising, for example, data, voice and multimedia. Particularly, the invention relates to a method for performing a handover in mobile communication system. 
         [0003]    2. Description of the Related Art 
         [0004]    Fourth generation mobile communication systems are being developed as a further step of evolution since the introduction of 2G and 3G mobile communication systems. A notable example of a 2G mobile communication system is the Global System of Mobile Communication (GSM) standardized by European Telecommunication Standards Institute (ETSI), which provides a digital circuit switched data using a Time Division Multiple Access (TDMA) based radio interface. GSM achieves downlink data rates up to 64 kbps with circuit switched data and up to 144 kbps with packet switched data using the General Packet Radio Systems (GPRS) technology also standardized in ETSI. From the 3G side of the family of mobile communication systems most notable example is the Wideband Code Division Multiple Access (WCDMA) radio technology based Universal Mobile Communications System (UMTS). UMTS supports packet switched data rates up to 384 kbps and up to 4 Mbps with High-Speed Downlink Packet Access (HSDPA). The fourth generation mobile communication systems, also referred to as the Next Generation Mobile Networks (NGMN), aim to provide downlink data rates up to 100 Mbps and uplink data rates up to 50 Mbps. The downlink data rates basically enable the receiving of High Definition Television (HDTV) signals. A 4G mobile communication system is being standardized by the 3G Partnership Project (3GPP) under the title Long-Term Evolution (LTE). The LTE architecture, referred to also as the Evolved Packet System (EPS), comprises an Evolved Packet Core (EPC) and an Evolved UMTS Radio Access Network (E-UTRAN). LTE relies on the Orthogonal Frequency Division Multiplexing (OFDM) radio technology. EPC also supports a variety of radio access technologies in addition to OFDM based E-UTRAN. EPC supports alternative radio access technologies such as WLAN and WiMAX. It is also a necessary objective for the EPC to support legacy Radio Access Technology (RAT) based access networks such as GSM-EDGE Radio Access Networks (GERAN) and UMTS Radio Access Networks (UTRAN). It has been postulated that there will be a long transition period in the deployment of full coverage using E-UTRANs or alternative RAT based RANs. Therefore, the support of legacy RATs is essential. There is also going to be interworking between the EPC and legacy core networks such the Circuit Switched (CS) GSM core network and the CS domain of the UMTS core network. 
         [0005]    Reference is now made to  FIG. 1 , which illustrates an Evolved Packet System (EPS) in prior art. In  FIG. 1  there is illustrated an Evolved Packet System (EPS)  100 . In Evolved Packet System  100  there is an Evolved UTRAN (E-UTRAN)  102 . E-UTRAN  102  communicates with Evolved Packet Core (EPC)  104 . Evolved Packet Core  104  communicates with IP Network  116 . There is also a UTRAN  106 , which communicates with Packet Switched Core  108 . Packet Switched Core  108  communicates with an IP Network  116 . There is also a GERAN  110  which communicates with Circuit Switched (CS) core  112 . CS core  112  communicates with Public Switched Telephone Network (PSTN)  114 , which may represent any circuit switched network. 
         [0006]    There is also illustrated a UE  101 , in other words, a mobile station. UE  101  may comprise a smart card such as, for example, a USIM or a SIM. 
         [0007]    In E-UTRAN  102  there are illustrated three eNodeBs, namely an eNodeB  120 , an eNodeB  122  and an eNodeB  124 . ENodeBs  120 - 124  have a signaling plane connection to a Mobility Management Entity (MME)  130  as illustrated with lines encircled by oval  180 . ENodeBs  120 - 124  have user plane connections to an S-GW  132 , as illustrated with lines encircled by oval  181 . In EPC  104 , there is a Mobile Management Entity (MME)  130 . S-GW  132  is connected to a Packet Data Network (PDN) Gateway (P-GW)  134 , as illustrated with the line  182 . EPC  104  is connected to IP Network  116  as illustrated with line  183 . 
         [0008]    In UTRAN  106  there are illustrated two nodeBs, namely a nodeB  140  and a nodeB  142 , which communicate with a Radio Network Controller (RNC)  144 . The lines representing user plane and signaling plane connections from nodeB  142  to RNC  144  are encircled with oval  185 . The user plane and signaling plane connections from nodeB  140  to RNC  144  are encircled with oval  186 . 
         [0009]    In PS Core  108 , there is an SGSN  150  and a GGSN  152 . The user plane and signaling plane connections from RNC  144  to SGSN  50  are illustrated with oval  187 . The user plane and signaling plane connections between SGSN  150  and GGSN  152  are illustrated with oval  188 . The GGSN  152  has an Access Point (AP) to IP network  116 . 
         [0010]    In GERAN  110  there is a base station  160  and a base station controller  162 . The signaling plane and user plane connections are encircled oval  190 . In circuit switched core  112  there is an MSC  170 . In practice MSC  170  may comprise an MSC server and a media gateway and a signaling gateway. The user plane and signaling plane connections from BSC  162  to MSC  170  are encircled with oval  191 . The user plane and signaling plane connections from CS Core  112  to PSTN  114  are encircled with oval  192 . 
         [0011]    An eNodeB such as eNodeB  120  acts as a base station in an EPS. An eNodeB performs radio resource management comprising radio bearer control radio admission control, connection mobility control and dynamic allocation of resources to UEs. An eNodeB also performs IP header compression and encryption of user plane data traffic. An eNodeB selects an MME at UE attachment when no routing to an MME can be determined from the information provided by the UE. An eNodeB also performs mobility management signaling with an MME. It routes a user plane data towards a serving gateway. An MME performs mobility management related functions. It performs tracking area list management, selects an S-GW and a P-GW for a UE. It selects MME in association with handovers. A serving gateway acts as local mobility anchor point for inter eNodeB handover. It performs packet routing and forwarding towards eNodeBs. A serving gateway also performs E-UTRAN idle mode downlink packet buffering an initiation of network trigged service requests. It also performs transport level packet marking in the uplink and the downlink directions. It also performs accounting and charging. A P-GW performs UE IP address allocation. It performs per user based package filtering by the package inspection. It performs transport level package marking in the downlink. It generally acts as an interface towards an external IP-NW such as the internet or an intranet. 
         [0012]    EPC provides only a packet switched domain wherein calls may only be established as multimedia sessions using, for example, an IP Multimedia Subsystem (IMS). A problem with the existing packet switched EPC architecture is that call establishment may take up to several seconds. Another related problem is that the EPC architecture regarding the interworking with CS networks is complicated, which may contribute to a further delay. 
         [0013]    In order to support CS calls and CS data bearers without necessitating User Equipments (UE) to camp exclusively on GERAN or UTRAN provided cells, it would be beneficial to be able to perform fallbacks to GERANs or UTRAN to establish CS calls or CS data bearers. It may be estimated that call establishment is initially faster through a legacy CS core network. Furthermore, in the case of mobile terminated CS calls initiated via the Public Switched Telephone Network (PSTN) there is no need to perform interworking through a VoIP gateway system. Furthermore, it is necessary to be able to perform a fallback to a correct Mobile Switching Center (MSC) which serves the current location area of the UE and to avoid unnecessary call attempts via a wrong MSC. 
       SUMMARY OF THE INVENTION 
       [0014]    The invention relates to a method, comprising: registering a first type location area of a mobile node to a first mobility management node; determining a second type location area based on a location of the mobile node; registering a second type location area of the mobile node to a second mobility management node of a second system; receiving a request to perform user plane bearer establishment through the second system; obtaining radio measurements associated with at least two candidate cells from the mobile node; checking the at least two candidate cells to find at least one cell associated with the second type location area; selecting a cell among the at least one cell; indicating the selected cell to the mobile node; and providing at least one of a handover request, a cell change order and a request for a redirection to the mobile node. 
         [0015]    The invention relates also to a system, comprising: a mobile node configured to perform radio measurements, to send a registration for a first type location area of the mobile node to a base station node and to receive at least one of a handover request, a cell change order and a request for a redirection from the base station node; a first mobility management node configured to receive a registration of a first type location area; a second mobility management node configured to receive a registration of a second type location area; and a base station node configured to register a first type location area of a mobile node to a first mobility management node, to determine a second type location area based on a location of the mobile node, to register a second type location area of the mobile node to a second mobility management node of a second system, to receive a request to perform user plane bearer establishment through the second system, to obtaining radio measurements associated with at least two candidate cells from the mobile node, to check the at least two candidate cells for at least one cell associated with the second type location area, to selecting a cell among the at least one cell, to indicate the selected cell to the mobile node and to provide at least one of a handover request, a cell change order and a request for a redirection to the mobile node. 
         [0016]    The invention relates also to an apparatus, comprising: a memory configured to store a design under test comprising at least one of a reference model and a register transfer level model; and at least one processor configured to register a first type location area of a mobile node to a first mobility management node, to determine a second type location area based on a location of the mobile node, to register a second type location area of the mobile node to a second mobility management node of a second system, to receive a request to perform user plane bearer establishment through the second system, to obtaining radio measurements associated with at least two candidate cells from the mobile node, to checking the at least two candidate cells to find at least one cell associated with the second type location area, to selecting a cell among the at least one cell, to indicate the selected cell to the mobile node and to provide at least one of a handover request, a cell change order and a request for a redirection to the mobile node. 
         [0017]    The invention relates also to an apparatus, comprising: means for registering a first type location area of a mobile node to a first mobility management node; means for determining a second type location area based on a location of the mobile node; means for registering a second type location area of the mobile node to a second mobility management node of a second system; means for receiving a request to perform user plane bearer establishment through the second system; means for obtaining radio measurements associated with at least two candidate cells from the mobile node; means for checking the at least two candidate cells for at least one cell associated with the second type location area; means for selecting a cell among the at least one cell; means for indicating the selected cell to the mobile node; and means for providing at least one of a handover request, a cell change order and a request for a redirection to the mobile node. 
         [0018]    The invention relates also to a computer program comprising code adapted to perform the following steps when executed on a data-processing system: registering a first type location area of a mobile node to a first mobility management node; determining a second type location area based on a location of the mobile node; registering a second type location area of the mobile node to a second mobility management node of a second system; receiving a request to perform user plane bearer establishment through the second system; obtaining radio measurements associated with at least two candidate cells from the mobile node; checking the at least two candidate cells for at least one cell associated with the second type location area; selecting a cell among the at least one cell; indicating the selected cell to the mobile node; and providing at least one of a handover request, a cell change order and a request for a redirection to the mobile node. 
         [0019]    The invention relates also to a computer program product comprising: registering a first type location area of a mobile node to a first mobility management node; determining a second type location area based on a location of the mobile node; registering a second type location area of the mobile node to a second mobility management node of a second system; receiving a request to perform user plane bearer establishment through the second system; obtaining radio measurements associated with at least two candidate cells from the mobile node; checking the at least two candidate cells for at least one cell associated with the second type location area; selecting a cell among the at least one cell; indicating the selected cell to the mobile node; and providing at least one of a handover request, a cell change order and a request for a redirection to the mobile node. 
         [0020]    The invention relates also to a method comprising: registering a first type location area of a mobile node to a first mobility management node; determining a second type location area based on a location of the mobile node; registering a second type location area of the mobile node to a second mobility management node of a second system; receiving a request to perform user plane bearer establishment through the second system; receiving an index to a locally defined configuration from the first mobility management node; obtaining prioritization information to prioritize at least one cell that belongs to the second type location area over other cells in the second system; and providing the prioritization information obtained to the mobile node. 
         [0021]    The invention relates also to a method comprising: registering a first type location area of a mobile node to a first mobility management node; determining a second type location area based on a location of the mobile node; registering a second type location area of the mobile node to a second mobility management node of a second system; receiving a request to perform user plane bearer establishment through the second system; providing a handover restriction list indicating the second type location area as the only allowed location area of the second system for the mobile node; detecting an incoming communication for the mobile node in the second system; checking at least one transmission from at least one neighboring cell in the mobile node; checking the restriction list by the mobile node; and skipping a location update in response to finding at least one neighboring cell in the restriction list. 
         [0022]    In one embodiment of the invention, the restriction list checking is performed in the mobile node when the mobile node is in idle mode, whereas the restriction list checking is performed in a base station node and/or in the core network when the mobile node is in an active state, for example, in a connected state. 
         [0023]    In one embodiment of the invention, the base station node comprises a UMTS Long-Term Evolution (LTE) nodeB, in other words, an eNodeB. In one embodiment of the invention, the base station node is any radio base station or a controller unit associated with at least one base station. 
         [0024]    In one embodiment of the invention, by a first type location area is meant a location area of a first type and by a second type location area is meant a location area of a second type. 
         [0025]    In one embodiment of the invention, the first system may comprise an OFDM based packet system. In one embodiment of the invention, the first system may comprise a 4G network, for example, an LTE system. In one embodiment of the invention, the first system may comprise an Ultra Mobile Broadband system. In one embodiment of the invention, the first system may comprise a multiple-input and multiple-output based system. In one embodiment of the invention, the first system may comprise an Evolution Data Only (EVDO) network. 
         [0026]    In one embodiment of the invention, the first system may be any cellular radio system. 
         [0027]    In one embodiment of the invention, the sec- and system comprises at least one of AMPS, GSM, UMTS, GPRS and CDMA2000. 
         [0028]    In one embodiment of the invention, the first mobility management entity comprises an LTE mobility management entity. In one embodiment of the invention, the second mobility management node comprises a visitor location register or a mobile switching centre or a mobile switching centre server. In one embodiment of the invention, the second mobility management node comprises a 1xRTT MSC or MSC server. CDMA-2000 1xRTT is a 3G wireless technology based on the CDMA platform. The 1x in 1xRTT refers to 1x the number of 1.25 MHz channels. The RTT in 1xRTT stands for Radio Transmission Technology. 
         [0029]    In one embodiment of the invention, a radio resource control entity in the base station node is configured to receive a list of at least two second type location area identifiers associated with the second mobility management node and to search for at least one cell in the list in response to failing to find a cell among the at least two candidate cells. 
         [0030]    In one embodiment of the invention, the mobile node is configured to establish a user plane connection via the selected cell to a network element associated with the second mobility management node. The network element may be a mobile switching center or a media gateway that communicates with a mobile switching center server. 
         [0031]    In one embodiment of the invention, the user plane connection comprises a circuit switched call and the network element is at least one of a mobile switching centre and mobile switching centre server. The circuit switched call may be a speech call, a video call or an unrestricted digital circuit switched data connection. 
         [0032]    In one embodiment of the invention, a radio resource control entity within the base station node is configured to obtain the location of the mobile node as a first type location area, to map the first type location area to the second type location area using a mapping table. 
         [0033]    In one embodiment of the invention, a radio resource control entity within the base station node is configured to receiving an index to a locally defined configuration from the first mobility management node and to obtaining information to prioritize at least one cell that belongs to the second type location area over other cells in the second system. The prioritization information may be stored in a memory in association with the base station node. 
         [0034]    In one embodiment of the invention, the radio resource control entity provides the prioritization information obtained to the mobile node. 
         [0035]    In one embodiment of the invention, a radio resource control entity in the base station node is configured to obtain information to prioritize additionally at least one cell that belongs to a list of prioritized location areas over other cells in the second system. 
         [0036]    In one embodiment of the invention, a radio resource control entity in the base station node is configured to obtain a handover restriction list indicating the second type location area as the only allowed location area of the second system for the mobile node. 
         [0037]    In one embodiment of the invention, a core network node such as a gateway MSC or visitor MSC or a mobility management node is configured to detect an incoming communication for the mobile node in the second system. The mobile node is configured to checking at least one transmission from at least one neighboring cell, to check the restriction list and to skip, that is, not to perform a location update in response to the finding at least one neighboring cell in the restriction list. The restriction list checking is performed in the mobile node when the mobile node is in idle mode, whereas the restriction list checking is performed in a base station node and/or in the core network when the mobile node is in an active state, for example, in a connected state. The base station node may not send the mobile node during handover to a cell that does not belong to the second type location area. 
         [0038]    In one embodiment of the invention, the second type location area comprises at least one of a global system of mobile communications location area, a general packet radio service routing area and universal mobile telecommunication system location area. 
         [0039]    In one embodiment of the invention, the first type location area comprises an evolved packet system tracking area. 
         [0040]    In one embodiment of the invention, said system comprises a mobile communication network. In one embodiment of the invention, the mobile node, in other words, a user equipment or user comprises a mobile station or generally a mobile terminal. In one embodiment of the invention a user of a mobile terminal is identified using a subscriber module, for example, User Services Identity Module (UMTS) or a Subscriber Identity Module (SIM). The combination of Mobile Equipment (ME) and a subscriber module may be referred to as a mobile subscriber. 
         [0041]    In one embodiment of the invention, the communication system comprises at least one of a Global System of Mobile Communications (GSM) network, a Universal Mobile Telephone System (UMTS) network and a 4G system such as LTE Evolved Packet System (EPS). The mobile station may be, for example, a GSM mobile station or a UMTS mobile station or an EPS user equipment with a dual mode or multimode functionality to support different access types. 
         [0042]    In one embodiment of the invention, the computer program is stored on a computer readable medium. The computer readable medium may be a removable memory card, a removable memory module, a magnetic disk, an optical disk, a holographic memory or a magnetic tape. A removable memory module may be, for example, a USB memory stick, a PCMCIA card or a smart memory card. 
         [0043]    The embodiments of the invention described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment of the invention. A method, a system, an apparatus, a computer program or a computer program product to which the invention is related may comprise at least one of the embodiments of the invention described hereinbefore. 
         [0044]    The benefits of the invention are related to improved speed in establishing connections to a mobile node, the avoiding of extra handovers and avoiding connection establishment to a wrong core network node. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0045]    The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings: 
           [0046]      FIG. 1  is a block diagram illustrating a Evolved Packet System (EPS) in prior art; 
           [0047]      FIG. 2  is a block diagram illustrating a combined Tracking Area Update (TAU) and Location Area Update (LAU) in one embodiment of the invention; 
           [0048]      FIG. 3  is a block diagram illustrating a mobile originated call with fallback to a Circuit Switched (CS) Core Network (CN) in one embodiment of the invention; 
           [0049]      FIG. 4  is a block diagram illustrating a mobile terminated call with fallback to a Circuit Switched (CS) Core Network (CN) in one embodiment of the invention; 
           [0050]      FIG. 5  is a block diagram illustrating overlapping Tracking Areas (TA) and Location Areas (LA) and the assignment of location areas to different Mobile Switching Centers (MSC) in one embodiment of the invention; 
           [0051]      FIG. 6  is a flow chart illustrating a fallback method to a circuit switched network in one embodiment of the invention; and 
           [0052]      FIG. 7  is a block diagram illustrating a radio node in one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0053]    Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
         [0054]      FIG. 2  is a block diagram illustrating a combined Tracking Area Update (TAU) and Location Area Update (LAU) in one embodiment of the invention. In  FIG. 2  there is illustrated a UE  101 , which decides to perform a tracking area update. UE  101  detects that it must start camping on a cell that belongs to a new tracking area. UE  101  detects that the new tracking area TAI is not in the list of TAIs that the UE  101  has registered with the network. As illustrated with arrow  201 , UE  101  sends a TAU request to eNodeB  120 . The TAU request message comprises a Globally Unique Temporary Identifier (GUTI), last visited TAI, selected network, the Globally Unique MME Identifier (GUMMEI) for an old MME. As illustrated with arrow  202 , eNodeB  120  sends a TAU request message to MME  130 . MME  130  obtains the mobility management context regarding UE  101 . From the mobility management context MME  130  determines if a visitor location register must also be updated. A new location area identifier is determined in MME  130  based on a mapping from the tracking area identifier that was obtained in the TAU request. The number for the visitor location register is derived from the tracking area identifier or the GUTI allocated to UE  101 . As illustrated with arrow  203 , MME  130  performs a location update procedure with MSC  170 . A Location Update (LU) accept message is illustrated with arrow  204 . In response to the location update accept message MME  130  sends a TAU accept message to eNodeB  120 , as illustrated with arrow  205 . ENodeB  120  sends the TAU accept message to UE  101 , as illustrated with arrow  206 . The TAU accept message comprises a GUTI, if MME  130  allocated a new GUTI. The TAU accept message also comprises a TAI list indicating a list of tracking area identifiers. UE  101  may be registered to a number of tracking areas and may be paged from all of them. 
         [0055]    In TAU accept message illustrated with arrow  205 , eNodeB receives an index to a locally defined configuration which affects handovers. MME  130  has earlier obtained the index from a Home Subscriber Server (HSS) (not shown) in a network attach procedure or from an earlier MME from which a TAU update has been performed to MME  130 , which is the current MME. In one embodiment of the invention, the index is the index to RAT/Frequency Selection Priority (RFSP) index. The locally defined configuration may provide in eNodeBs an indication to prefer 2G or 3G cells associated with the location area registered by UE  101 . The index may also be used to derive cell reselection priorities when UE  101  is in idle mode and to decide whether to redirect UE  101  in active mode to different frequency layers or radio access technologies. 
         [0056]    In one embodiment of the invention, the locally defined configuration may comprise an indication to prefer  2 G or  3 G cells associated with the location area registered by UE  101  and other allowed or prioritized location areas. The list of other location areas may comprise location areas associated with MSC  170 , that is, the MSC comprising the VLR to which the location update was performed with messages  203  and  204 . The list may have been received from MSC  170 . 
         [0057]    In eNode there may be information on the association of cells with location areas, which may be stored in the locally defined configuration or elsewhere. The information on the association may have been obtained from MME  130  or from another network element such as MSC  170  or a network management node. 
         [0058]    In one embodiment of the invention, eNodeB  120  may provide in message  206  a handover restriction list, which indicates the registered location area as the only allowed location area for UE  101  until a new TA update is performed which provides a new registered location area. By obtaining the handover restriction list UE  101  is prevented from making a location update before responding to a paging received from MSC  170 . 
         [0059]    In one embodiment of the invention, eNodeB  120  may indicate the registered location area and a list of other location areas as the allowed location areas to UE  101  in message  206 . The list of other location areas may comprise location areas associated with MSC  170 , that is, the MSC comprising the VLR to which the location update was performed with messages  203  and  204 . The list may have been received from MSC  170 . 
         [0060]    In one embodiment of the invention, the locally defined information may also comprise at least one radio parameter threshold, which indicates how much worse the radio parameter value may be in a cell preferred because of belonging to the register location area in order to justify it being selected instead of the cell providing the best radio parameter value. There may also be defined an absolute minimum value for a radio parameter to allow it to be selected. 
         [0061]    The embodiments of the invention described in association with  FIG. 2  may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment of the invention. 
         [0062]      FIG. 3  is a block diagram illustrating a mobile originated call with fallback to a Circuit Switched (CS) Core Network (CN) in one embodiment of the invention. 
         [0063]    The starting point in  FIG. 3  is that UE  101  is camping on a cell within a tracking area, to which eNodeB  120  belongs. As illustrated with arrow  301 , UE  101  sends a service request message to eNodeB  120 . ENodeB  120  send the service request messages onwards to MME  130 , as illustrated with arrow  302 . MME  130  sends an S1-AP message to eNodeB  120  as illustrated with arrow  303 . The S1 AP message comprises a CS full-back indicator. The CS fallback indicator tells that the call to be established must be established via the circuits switch domain within either a 2G network or a 3G network. ENodeB  120  solicits measurement reports from UE  101 , as illustrated with message  304 . UE  101  performs the cell quality measurements and sends them in response to eNodeB  120 , as illustrated with arrow  305 . In order to avoid the sending of UE  101  to a wrong location area, eNodeB  120  checks if there are any suitable cells in the location area to which UE  101  has been registered by way of location update procedure. Should it be the case that UE  101  is sent to wrong MSC, the service request must be rejected and new location area update must be performed before a new circuit switched call may be established via another MSC. If there are no cells available in the location area registered, eNodeB  120  checks a list of location area identifiers obtained from MME  130  in message  303 . ENodeB  120  checks if there are any cells with sufficient quality available in any of the location areas identified in the location area identifier list. If no cells are found in any of the location areas in the location area identifier list, eNodeB  120  selects any available cell. Upon having selected a cell, UE  101  sends a service request to BSC  162 , as illustrated with arrow  306 . The service request is transmitted via a base transceiver station (not shown). The service request is forwarded to MSC  170 , as illustrated with arrow  307 . By a service request message may also be meant a Radio Resource Control (RRC) connection request message. MSC  170  sends a response message to BSC  162 , as illustrated with arrow  308 . The response message may be a call proceeding message. The response message is forwarded from BSC  162  to UE  101 , as illustrated with arrow  309 . The bearer establishment from UE  101  to BSC  162  is illustrated with arrow  310 . The bearer is further connected from BSC  162  to MSC  170 , as illustrated with arrow  311 . The lines representing signalling plane and user planes connections towards a PSTN  114  are encircled with oval  312 . The circuit switched connection is bidirectional by nature. 
         [0064]    In one embodiment of the invention, the numbering of arrows  301  to  311  indicates a possible temporal order of messages and actions in response thereto. 
         [0065]      FIG. 4  is a block diagram illustrating a mobile terminated call with fallback to a Circuit Switched (CS) Core Network (CN) in one embodiment of the invention. 
         [0066]    The starting point in  FIG. 4  is that UE  101  is camping on a cell within eNodeB  120 . UE  101  is also registered to a location area which has been mapped from the current tracking area of UE  101 . As illustrated with arrow  401 , MSC  170  receives an Initial Address Message (IAM) from PSTN  114 . In response to the IAM, MSC  170  sends a paging message to MME  130 , as illustrated with arrow  402 . The paging message is sent further from MME  130  to eNodeB  120 , as illustrated with arrow  403 . The paging message is sent from eNodeB  120  to UE  101 , as illustrated with arrow  404 . In response to the paging UE  101  sends a service request message to eNodeB  120 , as illustrated with arrow  405 . The service request message is forwarded eNodeB  120  to MME  130 , as illustrated with arrow  406 . In response MME  130  sends an initial UE context setup message to eNodeB  120 , as illustrated with arrow  407 . UE  101  sends a paging response message to BSC  162  as illustrated with arrow  408 . The paging response message is forwarded from BSC  162  to MSC  170 , as illustrated with arrow  409 . In response to successful channel assignment (not shown) MSC  170  sends a Call Control (CC) Setup message  410  to BSC  162 . The CC Setup message is forwarded to UE  101 , as illustrated with arrow  411 . The allocation of a Traffic Channel (TCH) is illustrated with arrow  412 . The traffic channel allocation may also be performed earlier. 
         [0067]    In one embodiment of the invention, the numbering of arrows  401  to  412  indicates a possible temporal order of messages and actions in response thereto. 
         [0068]      FIG. 5  is a block diagram illustrating overlapping Tracking Areas (TA) and Location Areas (LA) and the assignment of location areas to different Mobile Switching Centers (MSC) in one embodiment of the invention. 
         [0069]    In  FIG. 5  there is illustrated an Evolved Packed System (EPS)  500 . EPS  500  comprises three tracking areas, namely a tracking area  502 , a tracking area  504  and a tracking area  506 . There are also three location areas, namely a location area  510 , a location area  512  and a location area  516 . There is a first MSC  520  and a second MSC  522 . In location area  510  there are a nodeB  530  and a nodeB  532 . In tracking area  506  there are illustrated three eNodeBs that are referred to with reference numeral  534 . The number of eNodeBs and NodeBs is just for illustrative purposes and may vary in actual implementations. Location areas  510  and  512  are under the control of MSC  520 . Location area  516  is under the control of MSC  522 . Location area  512  is located in the boarder area between tracking areas  504  and  506 . If UE has been registered to MSC  520 , it must prefer cells in location area  512  instead of cells in location area  516  even if they provide marginally better radio quality. 
         [0070]    In  FIG. 5  there are shown cells  540 - 544  associated with location area  512  and cells  550 - 554  associated with location area  516 . It is assumed a mobile node (not shown) is currently camping on a 4G cell (not shown) provided by tracking area  504  and it has previously performed a location update to a visitor location register in association with MSC  520 . The location update has been performed in association with tracking area update for tracking area  504 . 
         [0071]    In one embodiment of the invention, in response to the tracking area update, the mobile node has obtained a list of allowed or prioritized location areas, which has comprised location areas  510  and  512 . The list of location areas is used by the mobile node to avoid performing a handover from cell  544  to any of the cells  550 - 554  belonging to location area  516 , while the mobile node is in the process of initiating a call or session via MSC  520 . 
         [0072]    In one embodiment of the invention, in response to the tracking area update, an eNodeB supporting the 4G cell has obtained an index to RAT/Frequency Selection Priority. The index provides information that prioritizes cells  540 - 544  over cells  550 - 554 . The prioritization information is provided to the mobile node in the form of a prioritized cell or location area information, for example, a list. The priority information has the effect to minimize the probability of a handover from cell  544  to any of the cells  550 - 554  belonging to location area  516 , while the mobile node is in the process of initiating a call or session via MSC  520 . 
         [0073]    In one embodiment of the invention, there may be defined number of radio parameter thresholds associated with different radio parameters that indicate how much a preferred cell from a preferred location area may differ from an actually better cell in order to allow the use of the cell from the preferred location area. For at least one radio parameter there is defined value margin that must not be exceeded in the preference of cells from the preferred location area over the cells that actually provide better radio quality. 
         [0074]    The embodiments of the invention described in association with  FIG. 5  may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment of the invention. 
         [0075]      FIG. 6  is a flow chart illustrating a fallback method to a circuit switched network in one embodiment of the invention. 
         [0076]    At step  600  circuit switched fall back indication and location area information are received to an eNodeB from an MME. 
         [0077]    At step  602  eNodeB obtains measurement report from user equipment regarding neighboring cells currently received by the user equipment. 
         [0078]    At step  604  the eNodeB checks for suitable cells within the location area to which the user equipment performed a location update. 
         [0079]    At step  606  it is checked whether such cells were found. If at least one such cell was found the method continues at step  608 , otherwise the method continues at step  610 . 
         [0080]    At step  608  a fallback to the best cell within the registered location area is performed by the UE under the command of eNodeB. 
         [0081]    At step  610  eNodeB checks for suitable cells within location areas listed for the UE by the MME. At step  612  it checked if such cells where found. If the answer is yes, the method continues at step  614 , otherwise the method continues at step  616 . 
         [0082]    At step  614  is performed fallback to the best cell within the listed location areas. The fallback is performed by the command of eNodeB to the UE. 
         [0083]    At step  616  it is checked whether there are any suitable cells in any location area. At step  618  it is checked whether such cells were found. If the answer is yes, the method continues at step  620 , otherwise the method continues at  622 . 
         [0084]    At step  620  a fallback to the best cell within any location area is performed by the UE, by the command of the eNodeB. 
         [0085]    At step  622  a packet switched session is established or call establishment is abandoned. Typically a mobile originated call may be established via packed switched access, in case the establishment via circuit switched access is not possible. 
         [0086]    In one embodiment of the invention, any of the method steps listed  FIG. 6  may be performed by any base transceiver station or radio node instead of an eNodeB. 
         [0087]      FIG. 7  is a block diagram illustrating a base station node in one embodiment of the invention. 
         [0088]    Base station node  700  comprises at least one processor such as a processor  710 , a primary memory  730  and a secondary memory  720 . Processor  710  may comprise multiple cores. Base station node also comprises at least one network interfaces such as, for example, an Ethernet card or an optical carrier interface. Primary memory  730  may be a Random Access Memory (RAM). Secondary memory  720  is a non-volatile memory such as, for example, a magnetic or optical disk. 
         [0089]    In memory  730  there is stored software relating to functional entities  732  to  750 . Regarding to interface to a Mobility Management Entity (MME) there are functional entities  732 - 740 . Regarding the interface to UE, there are functional entities  742 - 750 . There is also a relay functional entity  741 . Functional entity  732  corresponds to OSI layer  1 . Functional entity  734  corresponds to OSI layer  2 . Functional entity  736  corresponds to IP Protocol layer. Functional entity  738  corresponds to stream control transmission protocol. Functional entity  740  corresponds to S1 interface application protocol. Functional entity  742  corresponds to OSI layer  1 . Functional entity  744  corresponds to the media access control sublayer. Functional entity  746  corresponds to the radio link control sublayer. Functional entity  748  corresponds to the Packet Data Convergence Protocol (PDCP). Functional entity  750  corresponds to radio resource control protocol. Functional entity  750  corresponds to the S1 interface application protocol. In one embodiment of the invention, radio resource control functional entity  750  is configured to provide to a mobile node cell selection related information, such information for the preference of cell belonging to a registered location area and/or the preference of cells in listed location areas. In one embodiment of the invention radio resource control functional entity is configured to perform at least one of the method steps explained in association with  FIG. 6 . In one embodiment of the invention, at least one of the method steps associated with  FIG. 6  may be performed either in the relay functional entity or in the radio resource control functional entity. 
         [0090]    When the at least one processor  710  executes functional entities associated with the invention, memory  730  comprises entities such as, any of the functional entities  732 - 750 . The functional entities within apparatus  700  illustrated in  FIG. 7  may be implemented in a variety of ways. They may be implemented as processes executed under the native operating system of the network node. The entities may be implemented as separate processes or threads or so that a number of different entities are implemented by means of one process or thread. A process or a thread may be the instance of a program block comprising a number of routines, that is, for example, procedures and functions. The functional entities may be implemented as separate computer programs or as a single computer program comprising several routines or functions implementing the entities. The program blocks are stored on at least one computer readable medium such as, for example, a memory circuit, memory card, magnetic or optic disk. Some functional entities may be implemented as program modules linked to another functional entity. The functional entities in  FIG. 1  may also be stored in separate memories and executed by separate processors, which communicate, for example, via a message bus or an internal network within the network node. An example of such a message bus is the Peripheral Component Interconnect (PCI) bus. 
         [0091]    The exemplary embodiments of the invention can be included within any suitable device, for example, including any suitable servers, workstations, PCs, laptop computers, PDAs, Internet appliances, handheld devices, cellular telephones, wireless devices, other devices, and the like, capable of performing the processes of the exemplary embodiments, and which can communicate via one or more interface mechanisms, including, for example, Internet access, telecommunications in any suitable form (for instance, voice, modem, and the like), wireless communications media, one or more wireless communications networks, cellular communications networks, 3 G communications networks, 4 G communications networks Public Switched Telephone Network (PSTNs), Packet Data Networks (PDNs), the Internet, intranets, a combination thereof, and the like. 
         [0092]    It is to be understood that the exemplary embodiments are for exemplary purposes, as many variations of the specific hardware used to implement the exemplary embodiments are possible, as will be appreciated by those skilled in the hardware art(s). For example, the functionality of one or more of the components of the exemplary embodiments can be implemented via one or more hardware devices. 
         [0093]    The exemplary embodiments can store information relating to various processes described herein. This information can be stored in one or more memories, such as a hard disk, optical disk, magnetooptical disk, RAM, and the like. One or more databases can store the information used to implement the exemplary embodiments of the present inventions. The databases can be organized using data structures (e.g., records, tables, arrays, fields, graphs, trees, lists, and the like) included in one or more memories or storage devices listed herein. The processes described with respect to the exemplary embodiments can include appropriate data structures for storing data collected and/or generated by the processes of the devices and subsystems of the exemplary embodiments in one or more databases. 
         [0094]    All or a portion of the exemplary embodiments can be implemented by the preparation of application-specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be appreciated by those skilled in the electrical art(s). 
         [0095]    As stated above, the components of the exemplary embodiments can include computer readable medium or memories according to the teachings of the present inventions and for holding data structures, tables, records, and/or other data described herein. Computer readable medium can include any suitable medium that participates in providing instructions to a processor for execution. Such a medium can take many forms, including but not limited to, non-volatile media, volatile media, transmission media, and the like. Non-volatile media can include, for example, optical or magnetic disks, magneto-optical disks, and the like. Volatile media can include dynamic memories, and the like. Transmission media can include coaxial cables, copper wire, fiber optics, and the like. Transmission media also can take the form of acoustic, optical, electromagnetic waves, and the like, such as those generated during radio frequency (RF) communications, infrared (IR) data communications, and the like. Common forms of computer-readable media can include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other suitable magnetic medium, a CD-ROM, CDRW, DVD, any other suitable optical medium, punch cards, paper tape, optical mark sheets, any other suitable physical medium with patterns of holes or other optically recognizable indicia, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other suitable memory chip or cartridge, a carrier wave or any other suitable medium from which a computer can read. 
         [0096]    While the present inventions have been described in connection with a number of exemplary embodiments, and implementations, the present inventions are not so limited, but rather cover various modifications, and equivalent arrangements, which fall within the purview of prospective claims. 
         [0097]    It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.