Abstract:
The present invention relates to mobile communication systems, and more particularly to technology that enables a User Equipment (UE) to obtain authorization to use Proximity-based Services. 
     In a first aspect of the invention, a method is performed by a home network proximity service function ( 104 ) for authorizing a mobile terminal ( 100 ) to use a proximity service, comprising receiving a request from the mobile terminal to obtain proximity service authorization in at least one other network ( 107, 108 ), obtaining authorization information from a proximity service function ( 103, 105 ) of the at least one other network for which proximity service authorization is requested, and providing the mobile terminal with authorization information required for authorization with said at least one other network for which the request is made.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to mobile communication systems, and more particularly to technology that enables a User Equipment (UE) to obtain authorization to use Proximity-based Services. 
       BACKGROUND 
       [0002]    The Third Generation Partnership Project (3GPP) produces standards that govern aspects of known mobile communications systems, such as the system known as Long Term Evolution (LTE). In Release 12 of technical specification TS 23.303, the 3GPP specifies functionality called Proximity-based Services (ProSe). This functionality includes methods that enable User Equipment (UE) to communicate directly with one another, UE to UE, by using a new radio channel (D2D—direct UE to UE radio channel for ProSe) based on LTE technology; i.e. communication between two or more UEs in proximity that are ProSe-enabled, by means of user plane transmission using Evolved Universal Terrestrial Radio Access (E-UTRA) technology via a path not traversing any network node. 
         [0003]    Before a UE can start to use the ProSe services, the UE needs to reach ProSe Functions/Servers (PFs) in the LTE Evolved Packet Core (EPC) network in order to obtain authorization. This presents problems, as are described in the following. 
         [0004]    PFs can be located in a number of places: There may be a PF in the home Network (NW), in the visited NW (if the UE is roaming), and in local NWs (i.e., in the vicinity of the UE). A local NW is an NW which is not the serving NW of the UE, and in whose radio resources the UE is authorized by the home NW to engage in so called ProSe Direct Discovery, which is a procedure employed by a ProSe-enabled UE to discover other ProSe-enabled UEs in its vicinity by using only the capabilities of the two UEs with E-UTRA technology. 
         [0005]    The 3GPP specifies UE-to-PF-signalling over the user plane. In general, the UE is not aware of whether a Packet Data Network (PDN) Connection is home-routed or whether it is a Local Break-Out (LBO); that is, the routing of roaming traffic that is handled by a local operator without going back to the home NW. The signalling from user to NW through the Internetwork Packet Exchange (IPX) across NW borders requires tunnelling and extensive configuration and should be avoided. Also, setting up a new home-routed PDN connection should be avoided if possible. The reason is because of the limit on the number of PDN connections that can be set up (e.g., three connections in some NWs) and the limited number of bearers (up to eight). 
       SUMMARY 
       [0006]    An object of the present invention is to solve, or at least mitigate, this problem in the art and to provide an improved method and device for authorizing a mobile terminal to use a proximity service. 
         [0007]    This object is attained in a first aspect of the invention by a method performed by a home network proximity service function for authorizing a mobile terminal to use a proximity service, comprising receiving a request from the mobile terminal to obtain proximity service authorization in at least one other network, obtaining authorization information from a proximity service function of the at least one other network for which proximity service authorization is requested, and providing the mobile terminal with authorization information required for authorization with said at least one other network for which the request is made. 
         [0008]    This object is attained in a second aspect of the invention by a home network proximity service function configured to authorize a mobile terminal to use a proximity service, which comprises a processing unit and a memory, said memory containing instructions executable by said processing unit, whereby said home network proximity service function is operative to receive a request from the mobile terminal to obtain proximity service authorization in at least one other network, obtain authorization information from a proximity service function of the at least one other network for which proximity service authorization is requested, and to provide the mobile terminal with authorization information required for authorization with said at least one other network for which the request is made. 
         [0009]    This object is attained in a third aspect of the invention by a method performed by a visiting network proximity service function for authorizing a mobile terminal to use a proximity service, comprising receiving a request from the mobile terminal to obtain proximity service authorization in at least one other network, forwarding the request to a home network proximity service function, receiving, from the home network proximity service function, authorization information of the at least one other network for which proximity service authorization is requested, and providing the mobile terminal with the authorization information received from the home network proximity service function. 
         [0010]    This object is attained in a fourth aspect of the invention by a visiting network proximity service function configured to authorize a mobile terminal to use a proximity service, which comprises a processing unit and a memory, said memory containing instructions executable by said processing unit, whereby said visiting network proximity service function is operative to receive a request from the mobile terminal to obtain proximity service authorization in at least one other network, forward the request to a home network proximity service function, receive, from the home network proximity service function, authorization information of the at least one other network for which proximity service authorization is requested, and provide the mobile terminal with the authorization information received from the home network proximity service function. 
         [0011]    This object is attained in a fifth aspect of the invention by a method performed by a mobile terminal of requesting authorization to use a proximity service, comprising submitting a request to obtain proximity service authorization, receiving a response indicating to which proximity service function the authorization request should be submitted, submitting the proximity service authorization request to the proximity service function indicated in the response. 
         [0012]    This object is attained in a sixth aspect of the invention by a mobile terminal configured to request authorization to use a proximity service, which comprises a processing unit and a memory, said memory containing instructions executable by said processing unit, whereby said mobile terminal is operative to submit a request to obtain proximity service authorization, receive a response indicating to which proximity service function the authorization request should be submitted, and submit the proximity service authorization request to the proximity service function indicated in the response. 
         [0013]    This object is attained in a seventh aspect of the invention by a method performed by a Packet Data Network Gateway (PGW) of addressing proximity service functions, comprising receiving a request of a mobile terminal to obtain proximity service authorization, and submitting a response to the request indicating to which proximity service function the authorization request should be submitted. 
         [0014]    This object is attained in an eight aspect of the invention by a Packet Data Network Gateway (PGW) configured to address proximity service functions, which comprises a processing unit and a memory, said memory containing instructions executable by said processing unit, whereby said PGW is operative to receive a request of a mobile terminal to obtain proximity service authorization, and submit a response to the request indicating to which proximity service function the authorization request should be submitted. 
         [0015]    This object is attained in a ninth aspect of the invention by a method performed by a Mobility Management Entity (MME) of addressing proximity service functions, comprising receiving a request of a mobile terminal to obtain proximity service authorization, and submit a response to the request indicating to which proximity service function the authorization request should be submitted. 
         [0016]    This object is attained in a tenth aspect of the invention by a Mobility Management Entity (MME) configured to address proximity service functions, which comprises a processing unit and a memory, said memory containing instructions executable by said processing unit, whereby said MME is operative to receive a request of a mobile terminal to obtain proximity service authorization, and submit a response to the request indicating to which proximity service function the authorization request should be submitted. 
         [0017]    Further provided is computer programs causing devices to perform the methods according to the present invention, and computer program products comprising computer readable medium having the computer program embodied therein. 
         [0018]    In conventional technology, issues exist with respect to PC3 signalling between a UE and a ProSe Function, when the ProSe Function and the UE reside in different networks. The authorization procedure as defined in the 3GPP TS 23.303 makes use of signalling over the PC3 interface towards a ProSe Function in the Home PLMN, in the Visited PLMN and in Local PLMNs. The PC3 signalling is carried over the user plane over the SGi interface, the SGi being the interface between the PGW and the PDN. 
         [0019]    There are potential problems related to the PC3 signalling over the SGi interface involving e.g. e issues with availability and security. The Internet connection may not be available to UEs at all times. There may be unwillingness by operators to open the ProSe Functions for access via Internet, and related to that possible security attacks. If the PC3 signalling will be transported over an Internetwork Packet Exchange (IPX) network, the security issues may be addressed, but the traffic needs to be tunnelled in Generic Routing Encapsulation (GRE) tunnels, General Packet Radio Service Tunnelling Protocol (GTP) or Internet Protocol Security (IP Sec) tunnels. 
         [0020]    In an aspect of the invention, a UE reaches the home ProSe Function by means of a home routed PDN connection. Thus, the UE connects an SGW via a S1-U interface and an H-PGW via S8 interface using IPX. 
         [0021]    Hence, the UE requests ProSe authorization from the ProSe Function in the LPLMN via the HPLMN ProSe Function using interface PC6; as the UE resides in the HPLMN, no roaming is undertaken. Thereafter, the ProSe Function in HPLMN obtains authorization information from the ProSe Function in the LPLMN. Finally, the HPLMN ProSe Function provides authorization info to the UE by merging the authorization information from LPLMN with its own authorization information before providing the UE with the required ProSe authorization information. 
         [0022]    Advantageously, the LPLMN is not directly addressed via PC3 but instead, signalling between the HPLMN and the LPLMN is done via the home ProSe Function over the PC6 interface. The IPX network need not tunnel network-to-network interface (NNI) signalling. Thereby, the problem of sending UE to ProSe server traffic requiring tunnelling through the IPX NW is advantageously eliminated. 
         [0023]    Policy decisions for ProSe authorization may be negotiated between ProSe Functions in the Home, Visited and Local PLMNs; the UE reaches the home ProSe Function, the home ProSe Function signals towards the visited ProSe Function and the local ProSe Function(s) over PC6 and PC7. After the negotiation, the home ProSe Function provides the authorization to the UE via the H-PGW and the SGW. 
         [0024]    In a further aspect of the invention, the UE reaches the visiting ProSe Function by means of an LBO PDN connection, i.e. the UE  100  is roaming. Thus, the UE connects to the SGW via the S1-U interface and the V-PGW via the S5 interface and further on to the VPLMN ProSe Function via PC3. The VPLMN ProSe Function forwards the UE request via PC7 to the home ProSe Function. 
         [0025]    The HPLMN ProSe Function receives the UE request for ProSe authorization over the PC7 interface and obtains authorization information from the ProSe Function in the VPLMN via PC7 and authorization information from the ProSe Function in the LPLMN (if applicable) via the PC6 interface. Thereafter, the ProSe Function in HPLMN merges the authorization information from VPLMN and LPLMN with its own authorization information before providing the UE with the applicable ProSe authorization information via the VPLMN ProSe Function, the V-PGW and the SGW. 
         [0026]    Again, the problem of sending UE to ProSe server traffic requiring tunnelling through the IPX NW, as is done in the art, is advantageously eliminated. 
         [0027]    Preferred embodiments of the present invention will be described in the following. 
         [0028]    Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the element, apparatus, component, means, step, etc.” are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The invention is now described, by way of example, with reference to the accompanying drawings, in which: 
           [0030]      FIG. 1  shows a signalling diagram illustrating a first conceivable procedure for ProSe authorization; 
           [0031]      FIG. 2  shows a signalling diagram illustrating a second conceivable procedure for ProSe authorization; 
           [0032]      FIG. 3  shows a signalling diagram illustrating a third conceivable procedure for ProSe authorization; 
           [0033]      FIG. 4  shows a signalling diagram that compares conventional procedures with new procedures described herein; 
           [0034]      FIG. 5  shows a signal routing diagram illustrating a routing possibility for a UE obtaining ProSe authorization according to an embodiment of the invention; 
           [0035]      FIG. 6  illustrates a flowchart of a ProSe authorization process carried out by a home ProSe Function according to an embodiment of the present invention; 
           [0036]      FIG. 7  shows a signal routing diagram illustrating a routing possibility or a UE obtaining ProSe authorization according to a further embodiment of the invention; 
           [0037]      FIG. 8  illustrates a flowchart of a ProSe authorization process carried out by a visiting ProSe Function according to an embodiment of the present invention; 
           [0038]      FIG. 9  illustrates a flowchart of UE signalling for requesting ProSe authorization according to an embodiment of the present invention; 
           [0039]      FIG. 10  illustrates a flowchart of a PGW managing UE signalling for requesting ProSe authorization according to an embodiment of the present invention; 
           [0040]      FIG. 11  illustrates a flowchart of UE signalling for requesting ProSe authorization according to an alternative embodiment of the present invention; 
           [0041]      FIG. 12  illustrates a UE according to an embodiment of the present invention; and 
           [0042]      FIG. 13  illustrates a network node according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description. 
         [0044]    It should be emphasized that the terms “comprises” and “comprising”, when used in this specification, are taken to specify the presence of stated features, integers, steps or components; but the use of these terms does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 
         [0045]    Moreover, reference letters may be provided in some instances to facilitate identification of various steps and/or elements. However, the use of reference letters is not intended to impute or suggest that the so-referenced steps and/or elements are to be performed or operated in any particular order. 
         [0046]    The various aspects of the invention will now be described in greater detail in connection with a number of exemplary embodiments. To facilitate an understanding of the invention, many aspects of the invention are described in terms of sequences of actions to be performed by elements of a computer system or other hardware capable of executing programmed instructions. It will be recognized that in each of the embodiments, the various actions could be performed by specialized circuits (e.g., analog and/or discrete logic gates interconnected to perform a specialized function), by one or more processors programmed with a suitable set of instructions, or by a combination of both. The term “circuitry configured to” perform one or more described actions is used herein to refer to any such embodiment (i.e., one or more specialized circuits and/or one or more programmed processors). Moreover, the invention can additionally be considered to be embodied entirely within any form of computer readable carrier, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein. Thus, the various aspects of the invention may be embodied in many different forms, and all such forms are contemplated to be within the scope of the invention. For each of the various aspects of the invention, any such form of embodiments as described above may be referred to herein as “logic configured to” perform a described action, or alternatively as “logic that” performs a described action. 
         [0047]    Additional aspects of embodiments consistent with the invention will be appreciated from the following descriptive material. The following description is particularly oriented towards the 3GPP Release 12 version of requirements for the ProSe PC3 interface and possible ways of improvement. As such, the terminology used in the description will be well understood by those of ordinary skill in the art. However, it will be understood that this orientation towards 3GPP Release 12 is for purposes of illustration, and is not intended to limit the scope and applicability of the various technical aspects in any way, since such aspects are believed to be applicable in other contexts as well. 
         [0048]    In conventional technology, issues exist with respect to PC3 signalling between a UE and a ProSe Function, when the ProSe Function and the UE reside in different networks. The authorization procedure as defined in the 3GPP TS 23.303 makes use of signalling over the PC3 interface towards a ProSe Function in the Home PLMN, in the Visited PLMN and in Local PLMNs. The PC3 signalling is carried over the user plane over the SGi interface, the SGi being the interface between the PGW and the PDN. 
         [0049]    There are potential problems related to the PC 3  signalling over the SGi interface:
       If the PC3 signalling will be transported over the Internet, there may be issues with availability and security. The Internet connection may not be available to UEs at all times. There may be unwillingness by operators to open the ProSe Functions for access via Internet, and related to that possible security attacks.   If the PC3 signalling will be transported over an Internetwork Packet Exchange (IPX) network, the security issues may be addressed. On the other hand, there are requirements from Groupe Speciale Mobile Association (GSMA) as expressed in the IR.34 specification, whereby UE to Server traffic must not be transported directly over IPX but needs to be tunnelled in Generic Routing Encapsulation (GRE) tunnels, General Packet Radio Service Tunnelling Protocol (GTP) or Internet Protocol Security (IP Sec) tunnels.       
 
         [0052]    The following looks at the requirements and discusses tentative solutions to the PC3 transport problem. 
         [0053]    From the 3GPP specification TS 22.278, requirements from stage 1 are:
       The HPLMN operator shall be able to authorize a ProSe-enabled UE to use ProSe Communication, separately for the HPLMN and for roaming in VPLMNs. This requirement applies to any ProSe E-UTRA Communication between two ProSe-enabled UEs, ProSe Group Communication, ProSe Broadcast Communication and ProSe-assisted Wireless Local Area Network (WLAN) direct communication.   The HPLMN operator shall be able to authorize the ability of a ProSe-enabled UE to use ProSe Communication to communicate with ProSe-enabled UEs served by a different PLMN. This requirement applies to any ProSe E-UTRA Communication between two ProSe-enabled UEs, ProSe Group Communication, ProSe Broadcast Communication and ProSe-assisted WLAN direct communication.   The VPLMN operator shall be able to turn on or off the ability for all the inbound roamers from a specific PLMN to use ProSe Communication. This requirement applies to any ProSe E-UTRA Communication between two ProSe-enabled UEs, ProSe Group Communication, ProSe Broadcast Communication and ProSe-assisted WLAN direct communication.       
 
         [0057]    From the TS 23.303 specification, the following requirements are extracted:
       the operator should be enabled to control the ProSe discovery feature in its network, and to authorize the functionality required for the ProSe discovery functions for each UE.       
 
         [0059]    From the GSMA IR.34 and IR.88, it can be deducted that:
       IPX requires that Server Server traffic and UE to UE/Server traffic is routed separately and that UE to Server traffic is encapsulated in tunnelling.       
 
         [0061]    The requirements require the HPLMN and the VPLMN to authorize the UE; however, for the Local PLMN, the ability for an operator to control discovery feature in its NW is only mentioned in the TS 23.303. This may apply to the Local NW; however, it is not required that the Local PLMN is able to communicate directly towards the UE for the authorization. 
         [0062]    A first conceivable procedure for ProSe authorization is illustrated in the signal flow diagram depicted in  FIG. 1 . This embodiment uses IPX and home routed PDN connection, i.e. the session is established via the home PGW (H-PGW)  102   a  of the UE  100 . In order to meet the requirement on tunnelling through the IPX network, the H-PGW  102   a  shall set up a GRE tunnel and if required an IP Sec tunnel through the IPX towards the ProSe Function  103 ,  105  in the VPLMN  107  and the LPLMN  108 , respectively. The H-PGW  102   a  may filter out PC3 traffic towards each ProSe Function  103 ,  105  in the V-PLMN  107  or LPLMN  108 . The H-PGW  102   a  may then set up tunnels towards the respective ProSe Function  103 ,  105  via the PC3 interfaces. This would require agreements between the operators such that the ProSe Function  103 ,  105  in each PLMN (local  107  or visited  108 ) is known by the H-PGW  102   a.  In particular, if the PC3 is home routed, it may be possible to configure this in the H-PGW  102   a  since there must be roaming agreements between the operators for the use of PC6 and PC7 interfaces between the ProSe Functions  103 ,  105  in VPLMN  107  and LPLMN  108 . The required authorization information to be provided to the UE  100  is collected by the H-PGW  102   a  from the respective ProSe Function  103 ,  104 ,  105  over the PC3 interface and submitted to the UE  100  via the SGW  101 . 
         [0063]    This procedure requires that each PGW for the roaming partners is configured with IP-addresses for ProSe Functions, and every time any roaming partner adds or removes a server, all PGWs in the networks are re-configured. It is not practically scalable, unless ProSe is only used between more than a few operators. 
         [0064]    A second conceivable procedure for ProSe authorization is illustrated in the signal flow diagram depicted in  FIG. 2 . This option uses IPX and LBO routed PDN connection. It is basically the same solution as discussed with reference to  FIG. 1 , but the configuration may be even more problematic in this scenario. In a commercial setting, the VPLMN  107  and the LPLMNs  108  may very well not have roaming relations. The required authorization information to be provided to the UE  100  is collected by the V-PGW  102   b  from the respective ProSe Function over the PC3 interface and submitted to the UE  100  via the SGW  101 . 
         [0065]    A third conceivable procedure for ProSe authorization is illustrated in the signal flow diagram depicted in  FIG. 3 . This option uses IPX and two PDN connections, one LBO routed PDN Connection via the V-PGW  102   b  and one home routed PDN connection via the H-PGW  102   a.  It is basically the same solution as discussed above with reference to  FIG. 1 , but using two PDN Connections, without any obvious benefits. Reaching the ProSe Function  105  in the LPLMN  108  is still problematic. There is no information supplied to the UE  100  indicating whether a PDN connection is home routed or using a local break-out. The UE  100  has two PDN connections, but the UE  100  is unaware of which one to use for signalling towards each ProSe Function. The required authorization information to be provided to the UE  100  is collected on the one hand by the V-PGW  1021 ) from the respective ProSe Function  103 ,  105  in the VPLMN  107  and LPLMN  108  over the PC3 interface and submitted to the UE  100  via the SGW  101 , and on the other hand by the H-PGW  102   a  from the ProSe Function  104  in the HPLMN  106  over the PC3 interface and submitted to the UE  100  via the SGW  101 . 
         [0066]    In a fourth conceivable procedure for ProSe authorization, the ProSe Function is reached by signalling over the Internet. The Internet connection may be protected by IP Sec tunnelling from the UE to the ProSe Functions. This embodiment may not always be feasible due to uncertain availability and quality of service of the connection. 
         [0067]    In a fifth conceivable procedure for ProSe authorization, different solutions for commercial and for public safety scenarios are used. For commercial use cases, lower security provided by an Internet connection may be acceptable, while for the public safety use cases, the higher security of a protected (possibly IPX) NW may be provided. In the public safety case, there may be less of a configuration problem than for the commercial uses. Public safety solutions may be operating within country borders. Other options for the public safety operations may be to use separate APNs. 
         [0068]      FIG. 4  shows a signalling diagram that compares conventional procedures with new procedures described herein. In the prior art procedure shown in the upper three steps of  FIG. 4 , the UE  100  initially requests ProSe authorization from the ProSe Function  103 ,  105  in the VPLMN  107  or LPLMN  108  in order to receive authorization info applicable to the present PLMN. Thereafter, the ProSe Function  103 ,  105  in VPLMN  107  or LPLMN  108  obtains authorization info from ProSe Function  104  of the HPLMN  106  and merges with own authorization policy. Finally, the ProSe Function  103 ,  105  in VPLMN  107  or LPLMN  108  provides authorisation info to the UE  100 . 
         [0069]    The lower three steps of  FIG. 4  illustrates an embodiment of the method for ProSe authorization of the UE  100  according to the invention. In step S 101 , the UE  100  requests ProSe authorization from the ProSe Function  103 , 105  in the VPLMN  107  or LPLMN  108  via the ProSe Function  104  in the HPLMN  106 , in order to receive authorization info applicable to the VPLMN/LPLMN  107 / 108 . Thereafter, in step S 102 , the ProSe Function  104  in HPLMN  106  obtains authorization info from the ProSe Function  103 ,  105  in VPLMN  107  or LPLMN  108  (or both, if applicable). Finally, in step S 103 , the ProSe Function  104  of the HPLMN  106  provides authorization info to the UE  100 . Hence, the HPLMN ProSe Function  104  merges the authorization info from VPLMN/LPLMN  107 / 108  with its own authorization policy before providing the UE  100  with the applicable VPLMN/LPLMN authorization information. 
         [0070]    The LPLMN  108  is a PLMN close to a current position of the requesting UE  100 , where another UE may be registered, i.e. another UE with which the UE  100  requesting authorization may want to communicate or discover. 
         [0071]    Thus, as will be described in the following, if the UE  100  already resides in the HPLMN  106 , no authorization is obtained from VPLMN  107 , but there is a LPLMN  108  from which the authorization information is obtained. This is referred to as a home routed connection, and the UE  100  request is received at the HPLMN ProSe Function  104  via a home PGW  102   a.    
         [0072]    If the UE  100  is roaming, authorization information is obtained from a VPLMN  107 , and there may well be a LPLMN  108  from which the authorization information is further obtained. This is referred to as a local break-out (LBO) connection and the UE request is received at the HPLMN ProSe Function  104  via a VPLMN ProSe Function  103 . 
         [0073]      FIG. 5  shows a signal routing diagram illustrating a routing possibility or a UE  100  obtaining ProSe authorization according to an embodiment of the invention. The new procedure involves changing the signalling procedure for authorization compared to conventional technology.  FIG. 5  illustrates the UE  100  reaching the home ProSe Function  104 , i.e. the ProSe Function  104  in the HPLMN  106 , by means of a home routed PDN connection. Thus, the UE  100  connects to the SGW  101  via the S1-U interface and the H-PGW  102   a  via the S8 interface using IPX. 
         [0074]    Hence, the UE  100  requests ProSe authorization from the ProSe Function  105  in the LPLMN  108  via the HPLMN ProSe Function  104  using interface PC6; as the UE  100  resides in the HPLMN  106 , no roaming is undertaken, Thereafter, the ProSe Function  104  in HPLMN  106  obtains authorization information from the ProSe Function  105  in the LPLMN  108 . Finally, the HPLMN ProSe Function  104  provides authorization info to the UE  100  by merging the authorization information from LPLMN  108  with its own authorization information before providing the UTE  100  with the required ProSe authorization information. 
         [0075]    Advantageously, the LPLMN  108  is not directly addressed via PC3 but instead, signalling between the HPLMN  106  and the LPLMN  108  is done via the home ProSe Function  104 , typically embodied by a server, over the PC6 interface. The IPX network need not tunnel network-to-network interface (NNI) signalling. Thereby, the problem of sending UE to ProSe server traffic requiring tunnelling through the IPX NW is advantageously eliminated. These procedures require changing the existing 3GPP agreed upon procedure. 
         [0076]    Policy decisions for ProSe authorization may be negotiated between ProSe Functions  104 ,  103 ,  105  in the Home, Visited and Local PLMNs  106 ,  107 ,  108  as previously shown in  FIG. 4 . The UE  100  reaches the home ProSe Function  104 . The home ProSe Function  104  signals towards the visited ProSe Function  103  and the local ProSe Function(s)  105  over PC6 and PC7. After the negotiation, the home ProSe Function  104  provides the authorization to the UE  100  via the H-PGW  102   a  and the SGW  101 . 
         [0077]      FIG. 6  illustrates a flowchart of a ProSe authorization process carried out by the home ProSe Function  104  according to an embodiment of the present invention. In step S 101 , the ProSe Function  104  in the HPLMN  106  receives a UE request for ProSe authorization. Then, in step Siena, the HPLMN ProSe Function  104  determines whether the UE  100  is roaming or not. If that is the case, the HPLMN ProSe Function  104  obtains in step S 102   a  the required authorisation information from the VPLMN ProSe Function  103 . Then, it proceeds to step S 102   b  and obtains the required authorisation information from the VPLMN ProSe Function  105  (if applicable; otherwise step S 102   b  is omitted). Finally, in step S 103 , the HPLMN ProSe Function  104  merges the authorization information from the ProSe Functions  103 , 105  of the VPLMN  107  and LPLMN  108  with its own authorization information before providing the UE  100  with the merged authorization information. 
         [0078]    If the HPLMN ProSe Function  104  determines in step S 101   a  that the UE  100  is not roaming, i.e. the UE  100  does not reside in a VPLMN  107 , the HPLMN ProSe Function  104  proceeds to step S 102   b  and obtains the required authorisation information from the VPLMN ProSe Function  103 . Finally, in step S 103 , the HPLMN ProSe Function  104  merges the authorization information from the LPLMN ProSe Function  105  with its own authorization information before providing the UE  100  with the merged authorization information. 
         [0079]      FIG. 7  shows a signal routing diagram illustrating a routing possibility for a UE  100  obtaining ProSe authorization according to a further embodiment of the invention. The new procedure involves changing the signalling procedure for authorization compared to conventional technology.  FIG. 7  illustrates the UE  100  reaching the visiting ProSe Function  103 , i.e. the ProSe Function  103  in the VPLMN  107 , by means of an LBO PDN connection, i.e. the UE  100  is roaming. Thus, the UE  100  connects to the SGW  101  via the S1-U interface and the V-PGW  102   b  via the S5 interface and further on to the VPLMN ProSe Function  103  via PC3. The VPLMN ProSe Function  103  forwards the UE  100  request via PC7 to the home ProSe Function  104 . 
         [0080]    In an embodiment of the invention, the VPLMN ProSe Function  103  forwards the UE request via a ProSe Proxy  109 , as will be discussed later. However, from a functional point of view, the visiting ProSe Function  103  and the proxy  109  can be regarded as being combined in a single network element. 
         [0081]    The HPLMN ProSe Function  104  receives the UE request for ProSe authorization over the PC7 interface and obtains authorization information from the ProSe Function  105  in the VPLMN  108  via PC7 and authorization information from the ProSe Function  105  in the LPLMN  108  (if applicable) via the PC6 interface. Thereafter, the ProSe Function  104  in HPLMN  106  merges the authorization information from VPLMN  107  and LPLMN  108  with its own authorization information before providing the UE  100  with the applicable ProSe authorization information via the VPLMN ProSe Function  103 , the V-PGW  102   b  and the SGW  101 . 
         [0082]    Again, the problem of sending UE to ProSe server traffic requiring tunnelling through the IPX NW, as is done in the art, is advantageously eliminated. 
         [0083]      FIG. 8  illustrates a flowchart of a ProSe authorization process carried out by the visiting ProSe Function  103  according to an embodiment of the present invention. In step S 201 , the ProSe Function  103  in the VPLMN  107  receives a UE request for ProSe authorization. Thereafter, in step S 202 , the VPLMN ProSe Function  103  forwards the request to the HPLMN ProSe Function  104  over the PC7 interface, whereby the HPLMN ProSe Function  103  obtains the required authorization information via PC6 and PC7. Thereafter, as previously has been discussed, the ProSe Function  103  in HPLMN  106  merges the authorization information from VPLMN  107  and LPLMN  108  with its own authorization information before providing the VPLMN ProSe Function  103  with the required ProSe authorization information in step S 203 . Finally, the VPLMN ProSe Function  103  submits the merged authorization information to the requesting UE  100  in step S 204 . 
         [0084]    As illustrated in the signal routing diagrams of  FIGS. 5 and 7 , respectively, the UE  100  may use any PDN connection for ProSe signalling and the UE  100  may not be aware if the PDN connection is home routed or a LBO connection. Therefore, it is required that both the home routed and the LBO PDN connections can be used. Reaching the home ProSe Function  104  via a home routed PDN connection presents no problem. However, if the LBO is used, a ProSe Function  103  in the visited NW  107  may provide a proxy function (as mentioned with reference to  FIG. 7 ) for routing of ProSe authorization messages to/from the home ProSe Function  104 . 
         [0085]    The visiting ProSe Function  103  (and the proxy  109 ) is in the same NW as the V-PGW  102   b  to avoid tunnelling and configuration problems. 
         [0086]    A visited operator that supports ProSe in its network should support the proxy function in the ProSe Function. A visited operator not supporting ProSe may not implement the ProSe proxy; however, it is unlikely that the ProSe UE will get ProSe service in this visited NW. Even such an unlikely use case may be supported by, for example, a specific ProSe APN in the HPLMN. 
         [0087]    A VPLMN operator supporting ProSe functionality includes a new functionality in the form of a Proxy ProSe Function (PF) on the SGi interface (defined, for example, by 3GPP standards), such that the UE can reach the home ProSe Function through this proxy. Thus, in an embodiment, the VPLMN ProSe Function  103  communicates with the HPLMN ProSe Function  104  via a VPLMN ProSe proxy  109 . The proxy  109  is connected to the VPLMN ProSe Function  103 , either as a separate element, or integrated with the VPLMN ProSe Function  103 . 
         [0088]    It should be noted that in case no response is received by the visiting ProSe Function  103  from the home ProSe Function  104  in step S 203  due to e.g. an error in communication path PC7, it cannot provide the UE  100  with the requested authorization information. Therefore, the UE  100  may need to implement a timer for re-transmission of the authorization in case it does not receive a response within the time limit stipulated by the timer. 
         [0089]      FIG. 9  illustrates a flowchart of UE signalling for requesting ProSe authorization according to an embodiment of the present invention. In a first step S 301 , the UE  100  makes a request to a PGW  102   a / 102   b  to establish a PDN connection for accessing the applicable ProSe Function  104 ,  103  in the HPLMN  106  for a home routed connection, or in the VPLMN  107  for an LBO connection. It should be noted that the UE  100  may not know whether a PDN connection is home routed or an LBO, but a Home Subscriber Server (HSS) can provide info to a Mobility Management Entity (MME) for PGW selection (as described for instance in TS  23 . 401 ) whether the allocation of a PGW from the visited PLMN is allowed or whether a PGW from the home PLMN shall be allocated. 
         [0090]    The PGW  102   a / 102   b  returns a VPLMN ProSe Function or ProSe proxy destination address (if applicable) in step S 302  in a Protocol Configuration Options (PCO) field in its response to the requesting UE  100 . The destination address may be embodied e.g. in the form of an Internet Protocol (IP) address or an FQDN that the UE uses for a Domain Name System (DNS) server look-up to obtain the actual address. 
         [0091]    The PCO field is thus used to return a new parameter, the ProSe Function/proxy address, to the UE  100 . A VPLMN  107  thus returns the ProSe 
         [0092]    Function/proxy address while a HPLMN  106  returns the home ProSe Function address (or a Fully Qualified Domain Name (FQDN) resolvable to the ProSe Function address) in the PCO field at establishment of a PDN connection. The UE  100  contacts the indicated ProSe Function for authorization. 
         [0093]    Hence, if the PGW in step S 302  returns a VPLMN ProSe Function/proxy address, i.e. the PGW is the V-PGW  102   b,  the UE  100  turns to the VPLMN ProSe Function/proxy  103 / 109  for authorization in step S 303  as previously has been discussed in detail with reference to  FIG. 7 . 
         [0094]    Otherwise, a home routed PDN connection is set up in step S 304 , wherein the UE  100  turns to the HPLMN ProSe Function  104  for authorization in step S 303  as previously has been discussed in detail with reference to  FIG. 5 . 
         [0095]    As can be deducted from  FIG. 9  (and in  FIGS. 5 and 7 ), UE signalling for ProSe Authorization shall advantageously always go to the ProSe Function  104  in the home NW  106 . The home ProSe Function  104  will then negotiate with the ProSe Function/proxy  103 / 109  in the visiting NW  107  and with the ProSe Function(s)  105  in the Local NW(s)  108 . 
         [0096]    Since the UE  100  is ProSe-enabled, it can be assumed that the HPLMN  106  has implemented ProSe. The only case when there is no ProSe Function/proxy address or FQDN in the PCO field is thus in the LBO scenario when the VPLMN  107  has not implemented ProSe functionality, in which case a home routed PDN connection is set up and used for authorization. 
         [0097]    For efficiency, the UE  100  should preferably first try to use the PDN connection that it already has established (which may be LBO), and then set up one or further PDN connection(s) towards the HPLMN  106  only in exceptional cases. 
         [0098]    As illustrated in  FIG. 9 , UE signalling shall go to a ProSe Function  104  in the HPLMN  106 . A visited NW  107  supporting ProSe shall in an embodiment implement a ProSe proxy  109 . Any NW (home  106  or visited  107 ) that supports ProSe shall preferably include a ProSe Function (or proxy) address in the PCO for a new PDN Connection. The home NW  106  includes the ProSe Function address, while the visited NW  107  provides the ProSe Function/proxy address. The UE  100  will use the address (proxy/ProSe Function /FQDN) if included, or otherwise set up a new PDN connection to HPLMN  106  to a preconfigured APN, which is configured to always be home routed. 
         [0099]      FIG. 10  illustrates a flowchart of PGW  102   a / 102   b  managing UE signalling for requesting ProSe authorization according to an embodiment of the present invention. In a first step S 401 , the PGW  102   a / 102   b  receives a request to create a session (e.g. at attach). 
         [0100]    If it is determined in step S 402  that the PGW  102   a / 102   b  indeed is ProSe-enabled, the PGW  102   a / 102   b  returns a VPLMN ProSe Function or ProSe proxy destination address (in case of a V-PGW  102   b ), or a HPLMN ProSe destination address (in case of an H-PGW  102   a ) in step S 403  in the PCO field in its response via the SGW  101  to the requesting UE woe Thus, if the UE  100  is roaming it will be directed to the VPLMN ProSe Function/proxy  103 / 109  and if not, the UE  100  is directed to the HPLMN ProSe Function  104  for authorization. 
         [0101]    If it is determined in step S 402  that the PGW  102   a / 102   b  is not ProSe-enabled, the PGW  102   a / 102   b  returns a response accordingly in step S 404 , wherein a home routed PDN connection subsequently will be set up, and the UE  100  will turn to the HPLMN ProSe Function  104  for authorization as previously has been discussed in detail with reference to  FIG. 5 . 
         [0102]      FIG. 11  illustrates a flowchart of UE signalling for requesting ProSe authorization according to an alternative embodiment of the present invention. In a first step S 501 , a roaming UE  100  makes a request to a Mobility Management Entity (MME) to establish a PDN connection for accessing the ProSe Function  103  in the VPLMN  107 . It should be noted that the UE  100  may not know whether a PDN connection is home routed or an LBO. 
         [0103]    The MME (not shown) returns a VPLMN ProSe Function or ProSe proxy destination (if applicable) in step S 502  in its response to the requesting UE  100 , if it has access to such a destination address. Hence, if the MME in step S 502  returns a VPLMN ProSe Function/proxy address, the UE turns to the VPLMN ProSe Function/proxy for authorization in step S 503  as previously has been discussed in detail with reference to  FIG. 7 . 
         [0104]    Otherwise, a home routed PDN connection is set up in step S 504 , wherein the UE turns to the HPLMN ProSe Function  104  in step S 505  using a preconfigured address to the ProSe Function  104  in the home NW  106 . The home ProSe Function will then negotiate with the ProSe Function/proxy  103 / 109  in the visiting NW  107  and with the ProSe Function(s)  105  in the Local NIN(s)  108  as previously discussed. 
         [0105]    It can be seen that aspects of embodiments of the invention involve the following changes to conventional procedures/technology:
       removal of the direct UE-to-Local ProSe Function signalling as is conventionally known from Release 12 of specification TS 23.303;   communication between the home ProSe Function to visiting ProSe Function and local ProSe Function over the PC6 and PC7 interfaces;   using a UE-to-server communication to the home ProSe Function via a home routed PDN connection or via local breakout if there is a Proxy ProSe Function in the VPLMN.       
 
         [0109]      FIG. 12  is a block diagram of an exemplary UE  1200  in accordance with embodiments consistent with the invention. This is a processor-implemented embodiment, but alternative embodiments may use hardwired elements or a combination of both. The UE  1200  comprises an authorization controller  1201  that includes a processor  1203  (e.g., one or more of a Central Processing Unit (CPU), dedicated circuitry and/or a software module), a memory  1205  and other circuitry/hardware  1207  as would be found in a conventional UE, such as radio circuitry  1209  and a user interface  1211 . The memory  1205  stores a program (“Pgm”)  1213  that, when executed by the processor  1203 , causes the processor to carry out various aspects of embodiments as described above. The memory  1205  can also store data  1215  that is used and/or generated as part of this functionality. 
         [0110]      FIG. 13  is a block diagram of an exemplary network node  1300  in accordance with various embodiments consistent with the invention. This is a processor-implemented embodiment, but alternative embodiments may use hardwired elements or a combination of both. The network node  1300  comprises an authorization controller  1301  that includes a processor  1303  (e.g., one or more of a Central Processing Unit (CPU), dedicated circuitry and/or a software module), and a memory  1305 . The network node  1300  includes other circuitry/hardware as would be found in a conventional network node, such as network interface  1307 . 
         [0111]    The memory  1305  stores a program (“Pgm”)  1309  that, when executed by the processor  1303 , causes the processor to carry out various aspects of embodiments as described above. The memory  1305  can also store data  1311  that is used and/or generated as part of this functionality. 
         [0112]    The various aspects of technology in accordance with the invention provide improvements over existing technology. For example:
       The ProSe Authorization is improved such that the user-to-NW signaling through the IPX across NW borders, which requires tunneling and extensive configuration, is avoided.   Except in rare cases, ProSe authorization is made possible without setting up a home routed PDN connection.       
 
         [0115]    The invention has been described with reference to particular embodiments. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the embodiment described above. The described embodiments are merely illustrative and should not be considered restrictive in any way.