Abstract:
Certain embodiment relate to public land mobile network resolution in a shared and a dedicated network. The method may include receiving, at the serving base station, a handover restriction list (HRL) comprising information on serving public land mobile networks (PLMN) or equivalent public land mobile networks (EPLMN) of the user equipment. The method may also include receiving a PLMN list comprising a plurality of PLMNs that are hosted by the target base station. The method may further include selecting a target PLMN for the user equipment using the HRL and the PLMN list, wherein the selected target PLMN is on the PLMN list but is not on the HRL. The method may also include sending a handover request message indicating the selected target PLMN for the user equipment to the target base station.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    Certain embodiments relate to communication systems, such as third generation partnership project (3GPP) and long term evolution (LTE). More particularly, certain embodiments relate to a method and apparatus for serving a public land mobile network (PLMN) resolution during multi-operator core network (MOCN)/shared and dedicated network environment involving multiple partner hosting which may utilize evolved-universal terrestrial radio access network (EUTRAN), inter public land mobile network (PLMN) handover (HO) either via S1 or X2 application protocols, automatic neighbor relation (ANR), self-optimizing network (SON), etc. 
         [0003]    2. Description of the Related Art 
         [0004]    In mobile networks, a handover restriction list (HRL) information element (IE) defines area roaming or access restrictions for subsequent mobility action for which the evolved Node B (eNB) provides information about the target of the mobility action towards the user equipment (UE), for example, handover (HO) and cell change order (CCO). According to current 3GPP 36.413 specification, whenever an eNB receives the handover restriction list, it shall overwrite previously received HRL information. In other words, the target eNB proceeds with roaming to targets all indicated in the handover restriction list received. 
         [0005]    Further, with an inter PLMN handover between a dedicated LTE network and a shared LTE network in a multi-operator core network (MOCN) configuration, the source eNB is not able to continue the handover while the target selected PLMN is not included in the UE HRL IE, although still broadcasted by the target eNB. The 3GPP standards also do not address this particular use case scenario. 
         [0006]    According to current 3GPP specification, the handover required message or handover request message (HRM) may be processed only if the target selected PLMN is included in UE HRL. 
         [0007]    Accordingly, the source eNB located within a dedicated LTE network is not able to or does not know how to proceed with processing the HRM when the dedicated LTE network&#39;s eNB does not know if the handover to the target selected PLMN is even allowed. 
       SUMMARY 
       [0008]    According to a first embodiment, a method for handing over a user equipment from a serving base station in a dedicated network to a target base station in a shared network, where the method may include receiving, at the serving base station, a handover restriction list (HRL) comprising information on serving public land mobile networks (PLMN) or equivalent public land mobile networks (EPLMN) of the user equipment. The method may also include receiving a PLMN list comprising a plurality of PLMNs that are hosted by the target base station. The method may further include selecting a target PLMN for the user equipment using the HRL and the PLMN list. The selected target PLMN is on the PLMN list but is not on the HRL. The method may also include sending a handover request message indicating the selected target PLMN for the user equipment to the target base station. 
         [0009]    According to a second embodiment, an apparatus for handing over a user equipment from a dedicated network to a target base station in a shared network, where the apparatus may include at least one processor and at least one memory including computer program code, where the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to receive a handover restriction list (HRL) comprising information on serving public land mobile networks (PLMN) or equivalent public land mobile networks (EPLMN) of the user equipment. The at least one memory and the computer program code may also cause the apparatus to receive a PLMN list comprising a plurality of PLMNs that are hosted by the target base station. The at least one memory and the computer program code may also cause the apparatus to select a target PLMN for the user equipment using the HRL and the PLMN list. The selected target PLMN is on the PLMN list but is not on the HRL. The at least one memory and the computer program code may also cause the apparatus to send a handover request message indicating the selected target PLMN for the user equipment to the target base station. 
         [0010]    According to a third embodiment, a computer program embodied on a computer-readable medium, the computer program may be configured to control a processor to perform operations including receiving, at a serving base station, a handover restriction list (HRL) comprising information on serving public land mobile networks (PLMN) or equivalent public land mobile networks (EPLMN) of a user equipment. The computer program may also be configured to control a processor to perform operations including receiving a PLMN list comprising a plurality of PLMNs that are hosted by a target base station. The computer program may be further configured to control a processor to perform operations including selecting a target PLMN for the user equipment using the HRL and the PLMN list, wherein the selected target PLMN is on the PLMN list but is not on the HRL. The computer program may also be configured to control a processor to perform operations including sending a handover request message indicating the selected target PLMN for the user equipment to the target base station. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For proper understanding of the invention, reference should be made to the accompanying drawings, wherein: 
           [0012]      FIG. 1  illustrates a dedicated and shared LTE network according to certain embodiments. 
           [0013]      FIG. 2  illustrates a flowchart of handover decision logic for an eNB according to certain embodiments. 
           [0014]      FIG. 3  illustrates a flowchart of handover decision logic for a dedicated and a shared LTE network according to certain embodiments. 
           [0015]      FIG. 4  illustrates a dedicated and shared LTE network for building a PLMN Selection List according to certain embodiments. 
           [0016]      FIG. 5  illustrates a flowchart of handover decision logic for a dedicated and a shared LTE network according to certain embodiments. 
           [0017]      FIG. 6  illustrates a network system according to certain embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Certain embodiments are related to inter PLMN handover between dedicated long term evolution (LTE) networks and a shared LTE network in a multi-operator core network (MOCN) configuration, while a target selected cell is supporting multiple broadcast PLMNs. In the MOCN approach, the shared evolved-universal terrestrial radio access network (eUTRAN) is connected to several core networks (CNs) such as the evolved packet core (EPC) via the Si interface, and one cell can be used by multiple operators&#39; core networks. In this regard, multiple PLMNs may be available for each shared LTE network&#39;s evolved-Node B (eNB). 
         [0019]    A single shared LTE network&#39;s eNB may, therefore, broadcast a list of multiple PLMN IDs in the same cell. The first entry of the PLMN list may be referred to as a primary PLMN in air interface, which is included in several identifiers such as eUTRAN cell global ID (ECGI), and Global eNB ID, etc. The shared LTE network&#39;s eNBs behave based on the assumption that a CN such as EPC is configured to perform routing via a primary PLMN of a target cell. In other words, routing can be based on ECGI (which is based on Primary PLMN ID). Also, routing can be based on Global eNB ID. 
         [0020]    An inter PLMN handover procedure can be initiated through a mobility management entity (MME) by sending a handover required message (in case of S1 HO) or a handover request message (in case of X2 HO) to the target eNB. The handover required message or the handover request message can contain a handover restriction list (HRL) information element (IE), which contains the serving PLMN and can contain equivalent PLMNs (EPLMNs), and roaming area or access restrictions. 
         [0021]    Most LTE network operators do not have enough radio resource spectrum to meet their subscriber data demand. The LTE network operator who has an abundance of spectrum often realizes their business goals by sharing their spectrum with other operators who lack spectrum. 
         [0022]    One effective way for an operator to share its spectrum with multiple partner networks/operators is by operating their eUTRAN network in MOCN configuration mode, thus enabling eUTRAN sharing. Another approach involves an operator hosting multiple partners&#39; PLMNs. These networks are referred to as shared networks. 
         [0023]    Partners who own and operate their own LTE network without sharing are often referred to as dedicated networks or conventional networks. Usage of both a dedicated network and a shared network results in a heterogeneous network scenario. 
         [0024]    Mobility across such a heterogeneous network poses unique challenges which are not currently addressed in 3GPP standards. Mobility challenges between the dedicated LTE network and the shared LTE network of an operator may need to be addressed for efficient usage of the dedicated and shared network spectrum. These deployments can often lend to a network overlay scenario for improving capacity or for coverage reasons. 
         [0025]      FIG. 1  illustrates a dedicated and a shared LTE network  100  according to certain embodiments.  FIG. 1  shows serving gateway (SGW)  110 , mobility management entity (MME)  120 , evolved Node B (eNB)  150 , and source eNB  160  in dedicated LTE network  102  and MME  130 , SGW  140 , target eNB  170 , and eNB  180  in shared LTE network  104 . 
         [0026]    In dedicated network  102 , eNB  150  and source eNB  160  are serving primary PLMN D1. Dedicated network  102  includes an EPC which may include MME  110  and SGW  120  and serves eNB  150 , source eNB  160 , and PLMN D1. An operator of dedicated network  102  may plan to use shared PLMN-S1 for excess capacity/coverage reasons; therefore, shared PLMN S1 may be served by the EPC of dedicated network  102 , the EPC may include MME  110  and SGW  120 . PLMN-S1 may be defined as an equivalent public land mobile network (EPLMN) to PLMN-D1 in MME  120  of dedicated network  102 . Thus, EPLMN can be defined as part of an MME configuration. 
         [0027]    Shared network  104 , target eNB  170 , and eNB  180  can serve primary PLMN-P1 and a shared PLMN-S1. Primary PLMN-P1 of MOCN (target) eNB  170  and eNB  180  are served by the EPC of shared network  104  which includes MME  130  and SGW  140 . 
         [0028]    The UEs  185  associated with dedicated network  102  may have a handover restriction list (HRL), for example, PLMN-D1 and S1. The operator of shared network  104  may have PLMN-P1 as serving PLMN. When UE  185  of dedicated network  102  is in serving PLMN-D1, the HRL may have serving PLMN-D1, EPLMN-S1 listed. When UE  185  of dedicated network  102  is in shared network  104 , the HRL may have serving PLMN-S1, EPLMN-D1 listed. Further, the primary PLMN-P1 cannot be defined as EPLMN for PLMN ID (D1 or S1) as it belongs to a main operator of shared network  104  and connects to its own independent EPC including MME  130  and SGW  140 . 
         [0029]    In the case of mobility from source eNB  160  belonging to dedicated network  102  to target eNB  170  belonging to shared network  104  in MOCN configuration, hosting multiple PLMNs, the following challenges may exist: UE  185  of an operator in dedicated network  102 , in PLMN-D1, measures a target physical cell ID (PCI) of target eNB  170  in shared network  104  and reports the target PCI to the serving source eNB  160  in dedicated network  102 , PLMN-D1. If the target PCI cannot be resolved by source eNB  160  of dedicated network  102 , then source eNB  160  may request UE  185  for the ECGI reporting. UE  185  may send the target cell an enhanced cell global identity (ECGI) defined as P1+ target eNB  170 , tracking area code (TAC) and PLMN list S1 supported by the target cell. TAC is common to all the broadcast PLMNs of the target eNB  170  in shared network  104 . UEs  185  serving eNB  160 , do not have any information about primary PLMN-P1 of shared network  104  and eNB  170  and may not initiate self-optimizing network (SON) related procedure to resolve the target eNB transport network layer (TNL). 
         [0030]    Additional challenges may exist, for example, even if an X2 link is already setup between source eNB  160  and target eNB  170 , then source eNB  160  may not attempt handover to target PLMN-P1 as source eNB  160  cannot be resolved using the HRL information available for UE  185 . Also, primary PLMN-P1 of target eNB  170  may not be in the HRL information associated with UE  185  of the operator of dedicated network  102 . Further, in the case of non-availability of X2 due to the above mentioned scenario, even the S1 handover cannot be initiated as source eNB  160  cannot resolve target PLMN-P1 despite the fact that the target cell serves PLMN-S1 which is EPLMN to UEs  185  serving PLMN-D1. 
         [0031]    Also, it should further be noted that a handover target cell may only be considered as allowed handover target if it broadcasts a PLMN-ID which is either the UE&#39;s serving PLMN-ID or contained in the UE&#39;s HRL within equivalent PLMN list Information Element. 
         [0032]      FIG. 2  illustrates a flowchart  200  of handover decision logic for an eNB according to certain embodiments.  FIG. 2  shows a decision flow graph in a source eNB, involved during a handover scenario. UE  185  is registered in serving PLMN-D1 and HRL is received in initial context set up request and may indicate the serving PLMN-D1, EPLMN-S1, no restrictions, etc. 
         [0033]    At  205 , source eNB  160  receives a measurement report from UE  185  with target cell eNB  170 &#39;s physical cell ID (PCI-X), Reference Signal Received Power (RSRP), and Reference Signal Received Quality (RSRQ). At  210 , source eNB  160  is checked via neighbor relation table (NRT) for target cell PCI, enhanced cell global identity (ECGI) being present in the NRT table. At  215 , the target cell PCI is not found in the NRT. At  220 , an ECGI request is sent to UE  185 . At  225 , optionally an automatic neighbor relation (ANR) method is utilized to get the details of PCI from an external SON/ANR database to resolve PCI, PLMN. Next, the NRT is updated. At  230 , an ECGI based on primary PLMN-P1, TAC is received and eNB checks the PLMN list/global unique mobility management entity (GUMMEI) received on  51  set up. At  235 , upon resolving the P1, TAC, an eNB configuration transfer is sent to candidate MME else an eNB configuration transfer message may be sent to any MME. At  240 , if there is a response from MME with Transport Network Layer (TNL), then at  245 , an X2 link is setup between source eNB  160  to target eNB  170 . Otherwise, at  275 , if target serving PLMN is allowed, then the logic proceeds to  280  and a handover required command is sent to MME, or if target serving PLMN is not allowed, then the logic proceeds to  265  and the handover process is stopped. At  250 , the target PLMN is checked and the UE HRL is received in the initial context setup request is checked to see if target PLMN is allowed or has restrictions, etc. At  255 , if target serving PLMN is allowed, then at  260 , the GU-Group ID is checked to see whether target eNB belongs to same pool area of source eNB. Otherwise, at  265 , the handover process is stopped if the target serving PLMN is not allowed. At  270 , if the GU-Group ID and target eNB  170  belong to the same pool area of source eNB  160 , then an X2 application protocol (AP) handover request message is sent to target eNB  170 , with HRL serving PLMN=target eNB  170  serving PLMN, EPLMN=current registered PLMN. Otherwise, at  280 , a handover required command is sent to MME. 
         [0034]      FIG. 3  illustrates a flowchart  300  of handover decision logic for a dedicated and a shared LTE network according to certain embodiments.  FIG. 3  illustrates why the handover fails in source eNB  160  in the scenario described above. It can be seen that the target PLMN-P1 cannot be resolved in source eNB  160  to initiate handover process although target eNB  170  serves both PLMN-P1, PLMN-S1 and PLMN-S1 being EPLMN to UE&#39;s current serving PLMN-D1. UE  185  is registered in serving PLMN-D1 and HRL is received in initial context set up request and may indicate the serving PLMN-D1, EPLMN-S1, no restrictions, etc. 
         [0035]    At  305 , source eNB  160  receives a measurement report from UE  185  with target cell&#39;s target eNB  170  physical cell ID (PCI-X), Radio Signal Receive Power (RSRP), and Reference Signal Received Quality (RSRQ). At  310 , source eNB  160  is checked via neighbor relation table (NRT) for target cell PCI, ECGI being present in the NRT table. At  315 , the target cell PCI is not found in the NRT. At  320 , an ECGI request is sent to UE  185 . At  325 , optionally an automatic neighbor relation (ANR) method is utilized to get the details of PCI from an external SON/ANR database to resolve PCI, PLMN. Next, the NRT is updated. At  330 , an ECGI based on primary PLMN-P1, TAC is received and source eNB  160  checks the PLMN list/global unique mobility management entity (GUMMEI) received on S1 set up. At  335 , the primary PLMN-P1 cannot be resolved and target GUMMEI is not available, therefore, an eNB configuration transfer message is sent to any MME. At  340 , if there is a response from MME with transfer network layer (TNL), then at  345 , an X2 link is setup between source eNB  160  to target eNB  170 . Otherwise, then at  350 , before initiating handover, source eNB  160 , the UE HRL serving PLMN-D1, EPLMN-S1 is checked. At  355 , if target PLMN P1 is not found in HRL, then at  360 , the handover process is stopped. 
         [0036]    The above mentioned problems can be addressed, provided the primary PLMN-P1 and the shared PLMN-S1 can be associated in eNB  150  and source eNB  160  of dedicated network  102 , such that UE  185  can be handed over from dedicated PLMN-D1 to shared PLMN-S1. 
         [0037]    Certain embodiments address how a logical association between primary PLMN-P1 and shared PLMN-S1 can be achieved using HRL information of UE  185  and PLMN list of target eNB  170 , for example, via the PLMN selection list, thereby deriving target PLMN-S1 to be used for handover to target cell (target eNB  170 ). Further, certain embodiments are fully backward compatible and would not impact existing functionality. 
         [0038]      FIG. 4  illustrates a dedicated and a shared LTE network  400  for building a PLMN selection list according to certain embodiments. In  FIG. 4  certain embodiments provide a solution to ensure a successful handover from dedicated LTE network  402  to shared LTE network  404  when a target selected PLMN is not included in the HRL of UE  470 . Dedicated network  402  includes MME  410 , eNB  430  and source eNB  440 . Shared network  404  includes MME  420 , target eNB  450  and eNB  460 . In particular, certain embodiments provide a solution to identify or determine if a target eNB  450  in shared network  404  is allowed to handle or proceed with a handover from dedicated LTE network  402  to shared LTE network  404  for a target selected PLMN that is not included in the HRL of UE  470 . In addition, certain embodiments provide a solution on how to select the target PLMN not included in the HRL of UE  470 , in connection with a correct target eNB  450  serving or primary PLMN in the eNBs of dedicated LTE network  402 . It should be noted that HRL of UE  470  can be stored in source eNB  440 , not in UE  470  itself. 
         [0039]    In this regard, certain embodiments introduce a new parameter called target PLMN selection list for use along with the HRL of UE  470  to resolve the target selected PLMN for handovers evaluation. For example, the target PLMN selection list may be used in the following order when available to derive target PLMN using: (1) PLMN list reported by UE as part of ECGI reporting and (2) PLMN list exchanged between source eNB  440  and target eNB  450 , such as in the case when X2 is setup. Also, other orders/sequences may fall within the scope of various embodiments. 
         [0040]    The target selected PLMN in the source eNB  440  in dedicated LTE network  402  may be derived from following formula: 
         [0000]      Target PLMN={(PLMN Selection LIST of Target eNB) ∩(Serving PLMN, EPLMN, in HRL of UE)}  (1)
 
         [0000]    where, “PLMN Selection List” of target eNB  450  can be obtained, for example, when source eNB  440  receives target ECGI and target cell broadcast PLMNs as part of ECGI measurement report or when X2 link is setup between source eNB  440  and target eNB  450 . In terms of precedence, when reported, the PLMN list obtained as part of target ECGI resolution may be considered as first choice to resolve the target PLMN. For example, the PLMN list obtained as part of X2 setup between the source eNB  440  and target eNB  450  may be considered as second choice for the target PLMN selection list. 
         [0041]    The handover restriction list (HRL) for UE  470  is relayed to source eNB  440  during the initial context setup procedure as part of an attach process as shown  FIG. 1 . 
         [0042]    Certain embodiments enable continuing a handover procedure from dedicated LTE network  402  to shared LTE network  404  when a target selected PLMN is not included in the HRL of UE  470 , wherein cells in shared LTE network  404  behave in accordance with a corresponding primary or serving PLMN and a target cell in shared LTE network  404  for the handover is supporting multiple broadcast PLMNs. 
         [0043]    In addition, certain embodiments enable using exemplary languages, such as messages/interfaces/protocols in  3 GPP specifications to illustrate how certain embodiments may be applied to ensure a successful handover from dedicated LTE network  402  to shared LTE network  404  in a multi-operator core network (MOCN) configuration when a target selected PLMN is not included in the HRL of UE  470 , where cells in shared LTE network  404  behave in accordance with a corresponding primary or serving PLMN. 
         [0044]    As described above, certain embodiments derive a logical association between PLMN-S1 and primary PLMN-P1 of shared network  404  in order to ensure smooth mobility between these networks. The primary PLMN-P1 cannot be defined as EPLMN for PLMN ID D1 or S1 as it belongs to main operator and connects to its own independent EPC which includes MME  420  and SGW2 (not shown). Mobility agreements between dedicated network  402  and shared network  404  may restrict users of PLMN-P1 from registering or camping in dedicated network  402 , PLMN D1, S1. 
         [0045]    Therefore, certain embodiments are directed to a unique way of deriving the relationship, that is, the target PLMN between PLMN-P1 and PLMN-S1 for handover using HRL of UE  470  and PLMN selection list of target eNB  450 . This is represented in equation (1) above. 
         [0046]    In the above case, when UE  470  attaches to the EPC which includes MME  410  in dedicated network  402 , source eNB  440  receives the HRL as part of initial context set up message. The HRL of UE  470  may indicate serving PLMN ID=D1 and EPLMN=S1. Now that source eNB  440  has both “PLMN Selection List” and the “HRL of UE  470 ”, it can derive the target PLMN based on certain embodiments via equation (1). 
         [0047]    If the PLMN selection list of target eNB  450  intersection with serving, EPLMN in HRL of UE  470  results in both serving and EPLMN yielding a value, then the intersection result with serving PLMN will take precedence over intersection result with EPLMN. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 ECGI Based  
                   
                   
                   
               
               
                   
                 on Target 
                   
                 HRL for  
                 Target PLMN = 
               
               
                 Information  
                 PLMN  
                 “PLMN  
                 the UE 
                 PLMN Selection  
               
               
                 Source  
                 (i.e Primary 
                 Selection  
                 (Serving,  
                 List ∩ Serving,  
               
               
                 at eNB-2 
                 PLMN) 
                 List” 
                 EPLMN) 
                 EPLMN in HRL 
               
               
                   
               
             
             
               
                 Measurement  
                 P1 
                 P1, S1 
                 D1, S1 
                 S1 
               
               
                 Report 
                   
                   
                   
                   
               
               
                 X2 Setup  
                 P1 
                 P1, S1 
                 D1, S1 
                 S1 
               
               
                 Procedure 
               
               
                   
               
             
          
         
       
     
         [0048]    Referring to Table 1 above, source eNB  440  in dedicated network  402  may use the “eNB Configuration Transfer Message” to resolve the TNL address of target eNB  450 . Based on the target PLMN  51 , derived using techniques described herein, source eNB  440  can now select appropriate GUMMEI to route the eNB configuration transfer message for TNL resolution in the case where the X2 link/interface between source eNB  440  and target eNB  450  is not setup. 
         [0049]    The eNB configuration transfer message may have a SON configuration transfer Information Element (IE) which may include: target eNB  450 : global eNB ID, selected tracking area identity (TAI)=&gt;target eNB  450 , S1+target TAC; and source eNB  440 : global eNB ID, selected TAI=&gt;source eNB  440 , D1+ serving TAC. 
         [0050]    In certain embodiments, if the target eNB  450  has a dedicated X2-IP address, for example, X2-C IP1 for PLMN-P1 and X2-C IP2 for PLMN-S1, for its MOCN partner, the target selected TAI, such as S1+Target TAC value composed by source eNB  440  helps target eNB  450  to resolve the MME configuration transfer message to provide an X2-IP TNL address relevant for its partner, for example, X2-C IP2 for PLMN-S1 is returned. It should be noted that when dedicated X2 IP addresses are defined per PLMN in shared eNB  450 , certain embodiments facilitate the request for obtaining PLMN specific X2 IP addresses. This is done by denoting target TAI in the eNB configuration transfer message as “Target selected PLMN+TAC”. 
         [0051]    In certain embodiments, upon receipt of TNL information of target eNB  450 , source eNB  440  can setup the X2 link. The GU-Group ID information may also be shared between source eNB  440  and target eNB  450  as part of X2 setup. The source eNB  440  may use the PLMN ID, for example, PLMN-S1 derived using techniques described herein to evaluate X2 handover. Further, the GU-Group ID information may be used in source eNB  440  in order to determine if X2 handover is supported. If target eNB  450  does not belong to the same pool area of the source eNB  440 , then S1 handover should be attempted. If X2 handover to target cell is allowed, then source eNB  440  may send handover request message to target eNB  450  with HRL which may indicate serving=S1 and EPLMN=D1. If S1 handover has to be used, then source eNB  440  may send handover required message to the MME with target PLMN based on S1, as derived. 
         [0052]      FIG. 5  illustrates a flowchart  500  of handover decision logic for a dedicated and a shared LTE network according to certain embodiments. UE  470  is registered in serving PLMN D1 and HRL is received in initial context set up request and may indicate the serving PLMN-D1, EPLMN-S1, no restrictions, etc. 
         [0053]    Referring, in part, also to reference numerals in  FIG. 4 , at  505 , source eNB  440  receives a measurement report from UE  470  with target cell&#39;s target eNB  450  physical cell ID (PCI-X), Radio Signal Receive Power (RSRP), and Reference Signal Received Quality (RSRQ). At  510 , source eNB  440  is checked via neighbor relation table (NRT) for target cell PCI, ECGI being present in the NRT table. At  515 , the target cell PCI is not found in the NRT. At  520 , an ECGI request is sent to UE  470 . At  525 , an automatic neighbor relation (ANR) method is utilized to get the details of PCI from an external SON/ANR database to resolve PCI, PLMN. Next, the NRT is updated. At  530 , an ECGI based on primary PLMN-P1, TAC is received and eNB checks the PLMN list/global unique mobility management entity (GUMMEI) received on  51  set up. At  535 , primary PLMN-P1 cannot be resolved, so source eNB  440  determines a target PLMN based on a formulation of the intersection of “PLMN Selection List” and “Serving, EPLMN in HRL of UE”. At  540 , target PLMN=PLMN S1, GUMMEI=S1+MMEGI+MMEC and target selected TAI=S1+target TAC, where MMEGI is mobility management entity group ID and MMEC is mobility management entity code. At  545 , if there is a response from MME with transfer network layer (TNL), then at  550 , an X2 link is setup between source eNB  440  to target eNB  450 . At  555 , the target PLMN is checked and the UE HRL is received in the initial context setup request is checked to see if target PLMN is allowed, restrictions, etc. At  560 , if target serving PLMN-S1 is allowed then the logic proceeds to  565 . Otherwise, at  580 , the handover process is stopped. At  565 , if the GU-Group ID and target eNB  450  belong to the same pool area of source eNB  440 , then an X2 application protocol handover request message is sent to target eNB  450 , with HRL serving PLMN=S1, EPLMN=D1, then the logic proceeds to  570 . At  570 , the GU-Group ID is checked to see whether target eNB  450  belongs to same pool area of source eNB  440 . Otherwise, at  575 , a handover required command is sent to MME, such as target PLMN=S1. S1 and X2 handover process may proceed as per 3GPP. 
         [0054]    The use of the above logic can be selected by activating a parameter in the source eNB  440 , for example, called “Target PLMN resolution parameter (Enable/Disable)”. When the above parameter is active, the source eNB  440  may resolve the primary PLMN in ECGI to PLMN ID obtained by intersection of PLMN selection list of target eNB  450  and PLMN supported in HRL which may indicate the serving PLMN-D1, EPLMN-S1, no restrictions, etc., otherwise the normal procedure as depicted in  FIG. 1  may resume. 
         [0055]    Certain embodiments focus on deriving the target PLMN for handover from a dedicated network to a shared network, that is, inter PLMN mobility support for networks that have a dedicated and a shared eUTRAN network based on different PLMN IDs. 
         [0056]    The target PLMN thus selected as per certain embodiments is also used in selecting the correct: GUMMEI (MME) to route the eNB configuration transfer message; target selected TAI while composing the eNB configuration transfer message; source PLMN in the HRL for X2 handover; and target PLMN in S1 handover required message in case of S1 handover. 
         [0057]    Certain embodiments include an implementation of an additional logic in the eNB, that would use UE specific HRL and the “Target PLMN Selection List” which is derived from PLMN list send by UE as part of ECGI reporting or PLMN list exchanged by eNBs as part of X2 set up between eNBs, to determine the target PLMN and target TAI for initiating the inter PLMN handover process. The target PLMN may also be used for selecting the correct MME for sending the eNB configuration transfer message associated with X2 TNL resolution. 
         [0058]    The logic would make use of following information available with eNB: PLMN served by EPC (MME); PLMN list of target eNB received as part of ECGI reporting; PLMN list received as part of X2 setup; and HRL information associated with the UE, received as part of initial context set up or a previous handover message. 
         [0059]    In certain embodiments, this use case is also applicable in a scenario in which a shared network operator may allocate dedicated X2-IP addresses for partner&#39;s network. If the target eNB has dedicated X2-IP address (X2-C IP1 for PLMN-P1 and X2-C IP2 for PLMN-S1) for its MOCN partner, the target selected TAI (S1+Target TAC) value composed by source eNB helps the target eNB to resolve the MME configuration transfer message to provide X2-IP TNL address relevant for its partner (X2-C IP2 for PLMN-S1 is returned). 
         [0060]    In certain embodiments, the operator of a dedicated network may host multiple PLMNs, for example, multiple tenants with different PLMNs, in addition to PLMN-D1 there are PLMN-D2, PLMN-D3, etc. on the source eNB. All tenant PLMNs are defined as equivalent to PLMN-S1 broadcast on the shared network eNB. Certain embodiments can now be used to send tenant subscribers on shared network eNB to respective PLMNs on dedicated network eNB. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 HRL for the  
                   
               
               
                   
                 ECGI Based 
                 “PLMN 
                 UE (Tenant 
                   
               
               
                   
                 on Target 
                 Selection 
                 based on 
                 Target PLMN = 
               
               
                 Information 
                 PLMN  
                 List” on 
                 PLMN-D2) 
                 PLMN Selection  
               
               
                 Source at 
                 (i.e., Primary 
                 Target  
                 (Serving, 
                 List ∩ Serving,  
               
               
                 Target eNB 
                 PLMN) 
                 eNB 
                 EPLMN) 
                 EPLMN in HRL 
               
               
                   
               
             
             
               
                 Measurement 
                 D1 
                 D1, D2 
                 D2, S1 
                 D2 
               
               
                 Report 
                   
                   
                   
                   
               
               
                 X2 Setup 
                 D1 
                 D1, D2 
                 D2, S1 
                 D2 
               
               
                 Procedure 
               
               
                   
               
             
          
         
       
     
         [0061]    Table 2 above depicts in certain embodiments, how the target PLMN is resolved in a situation where a UE belonging to PLMN-D2 attempts to move from shared PLMN-S1 to PLMN-D2 on source eNB  440 . It should be noted that the HRL for this UE while on PLMN-S1 is serving PLMN=&gt;S1 and EPLMN=&gt;D2. 
         [0062]    Alternatively, as part of a separate handover decision logic, when a UE reports a ECGI with primary PLMN information that is not known at an initial eNB then the initial eNB checks if the broadcast PLMN list of other eNBs is available from ECGI measurement report. If the initial eNB finds a common PLMN within the broadcast list and HRL list of the UE, then the common PLMN is used as the target PLMN. However, if the broadcast PLMN list of the other eNBs is available from a previous X2 application protocol signaling between the eNBs, then the initial eNB finds a common PLMN within broadcast list and HRL list of the UE and the common PLMN is used as target PLMN. Otherwise, a target transport network layer (TNL) resolution is not allowed as a self-optimizing network (SON) eNB configuration transfer message cannot be routed to the target side of the shared LTE network. Further, a handover is not allowed due to the target PLMN resolution was not possible, leading to resort to a S1 handover. 
         [0063]      FIG. 6  illustrates a system according to certain embodiments. In one embodiment, a system may include several devices, such as, for example, network element  600 , source eNB  630 , and target eNB  655 . Network element  600  may correspond to MMEs  120 ,  130 ,  410  and  420  or SGWs  110  and  140 , as shown in  FIGS. 1 and 4 . Source eNB  630  may correspond to eNBs  160  and  440  and target eNB  655  may correspond to eNBs  170  and  450 , as shown in  FIGS. 1 and 4 . The system may include more than one eNB, although only two eNBs are shown for the purposes of illustration. 
         [0064]    Each of the devices in the system may include at least one processor, respectively indicated as  610 ,  640 , and  665 . At least one memory may be provided in each device, and indicated as  615 ,  645 , and  670 , respectively. The memory may include computer program instructions or computer code contained therein. One or more transceiver  605 ,  635 , and  660  may be provided, and each device may also include an antenna, respectively illustrated as  620 ,  650 , and  675 . Although only one antenna each is shown, many antennas and multiple antenna elements may be provided to each of the devices. Other configurations of these devices, for example, may be provided. For example, network element  600 , source eNB  630 , and target eNB  655  may be additionally or solely configured for wired communication (not shown), and in such a case antennas  620 ,  650 , and  675  may illustrate any form of communication hardware, without being limited to merely an antenna. 
         [0065]    Transceivers  605 ,  635 , and  660  may each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception. 
         [0066]    Processors  610 ,  640 , and  665  may be embodied by any computational or data processing device, such as a central processing unit (CPU), application specific integrated circuit (ASIC), or comparable device. The processors may be implemented as a single controller, or a plurality of controllers or processors. 
         [0067]    Memories  615 ,  645 , and  670  may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate therefrom. Furthermore, the computer program instructions may be stored in the memory and may be processed by the processors may be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. 
         [0068]    The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as network element  600 , source eNB  630 , and target eNB  655 , to perform any of the processes described above (see, for example,  FIGS. 2 ,  3 , and  5 ). Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, may perform a process such as one of the processes described herein. Alternatively, certain embodiments of the invention may be performed entirely in hardware. 
         [0069]    One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention. In order to determine the metes and bounds of the invention, therefore, reference should be made to the appended claims. 
       LIST OF ABBREVIATIONS AND DEFINITIONS: 
       [0070]    3G Third Generation 
         [0071]    3GPP Third Generation Partnership Project for UMTS 
         [0072]    3GPP2 Third Generation Partnership Project for CDMA 2000 
         [0073]    ECGI Enhanced Cell Global Identity 
         [0074]    eNB Evolved Node B 
         [0075]    EPC Evolved Packet Core 
         [0076]    EUTRAN Evolved UTRAN 
         [0077]    GSM Global System for Mobile Communications 
         [0078]    GUGI Global Unique Group ID 
         [0079]    GUMMEI Global Unique Mobility Management Entity 
         [0080]    HRL Handover Restriction List 
         [0081]    LTE Long Term Evolution 
         [0082]    MME Mobility Management Entity 
         [0083]    MOCN Multi-Operator Core Network 
         [0084]    PCI Physical Cell ID 
         [0085]    SGW Serving Gateway 
         [0086]    SON Self-optimizing Network 
         [0087]    TAI Tracking Area Identity 
         [0088]    TAC Tracking Area Code 
         [0089]    TNL Transport Network Layer