Patent Publication Number: US-2021195507-A1

Title: Traffic Steering Between LTE and NR

Description:
TECHNICAL FIELD 
     The present invention is directed to methods and apparatuses involving Packet Data Network, PDN, level traffic steering between Long Term Evolution, LTE, and New Radio, NR, radio access technologies. 
     BACKGROUND 
     The well-known SAE-LTE (System Architecture Evolution-Long Term Evolution) architecture has been shown in  FIG. 1 . In the 5G work in 3GPP a split between Mobility Management (MM) and Session Management (SM) has been defined compared to in EPC, (Evolved Packet Core) where MME (Mobility management Entity) supports both MM (Mobility management) and some SM (Session management) functionality. The Access and Mobility Function (AMF) supports MM functionality and the Session Management Function (SMF) supports SM functionality. The AMF (Application Mobility Function) selects the SMF. Different SMFs may be selected for different PDU (Packet Data Unit) Sessions of a UE (User Entity), e.g. PDU Sessions to different Data Network Names (DNNs)/Access Point Name, APNs, or the same SMF may be used. The reference architecture is shown in the  FIG. 2 , which corresponds to TS 23.501 V0.5.0 (2017 May), FIG. 4.2.3-3. 
     In  FIG. 3  corresponding to 3GPP TS 38.300 V1.2.1 (2017 November),  FIGS. 4.1-1 , the Overall Architecture and Functional Split is shown. An NG-RAN (Next Generation/New radio-Radio Access Node) node is either:
         a gNodeB, QNB, providing NR (New Radio/5G) user plane and control plane protocol terminations towards the UE; or   a next generation eNodeB, ng-eNB, providing E-UTRA (Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access) user plane and control plane protocol terminations towards the UE.       

     The gNBs and ng-eNBs are interconnected with each other by means of the Xn interface. The gNBs and ng-eNBs are also connected by means of the NG interfaces to the SGC, more specifically to the AMF (Access and Mobility Management Function) by means of the NG-C interface and to the UPF (User Plane Function) by means of the NG-U interface (see 3GPP TS 23.501). 
     In 5G scenarios in 3GPP NR &amp; Next Generation Core (NG Core) so-called options 3, 3a, 3x, c.f.  FIG. 4 , are known as deployment options for 5G where NR can serve as the secondary RAT (Radio Access Technology) to LTE. For the S1 control plane interface, it is the same for all these options and it is always anchored in LTE eNodeB. For S1 user plane interface, it is specific per option: for option 3, it is always anchored in LTE eNodeB; for option 3a, it can be anchored on both LTE eNodeB (corresponding to ng-eNB) and NR GNodeB (gNB); for option 3x, it is always anchored on NR GNodeB (gNB). 
       FIG. 5  and  FIG. 6  show known control plane and user plane interfaces. 
     For the radio interface, the UE can connect to both eNodeB (LTE) and GNodeB (NR) simultaneously if UE supports dual radio. In each particular option, for each EPS bearer, it is the eNodeB that decides the traffic steering between the LTE and the NR radio interface. 
     However, these options may give rise to certain technical complications. 
     SUMMARY 
     For the options 3, 3a, 3x, shown in  FIG. 4 , the eNodeB decides, or enforces, the traffic steering between the LTE and the NR radio for each EPS bearer. However, for the IMS service VoLTE (Voice Over LTE) and ViLTE (Video Over LTE) there might be problems for some UEs, e.g. the UEs which have two processors (one for LTE and one for NR) to have the traffic from voice and video bearers to be transferred on different radio access technologies, RAT&#39;s. Meanwhile, from a network perspective, depending on the local policy (in HPLMN (Home Public Land Mobile Network) and VPLMN (Visitor Public Land Mobile Network) respectively in case of roaming) and depending on the roaming agreement, there might be different RAT usage policies for service to different APN&#39;s, e.g. the IP Multimedia Subsystem, IMS, service may not be allowed on NR while internet service is allowed. The inventors of the present application have reckoned that for deciding to apply the appropriate traffic steering between LTE and NR for a UE in question, the eNodeB does not have sufficient information. The same problem may exist also for other dualconnectivity deployments specified in the art, i.e., for Option 4 and Option 7. 
     It is a first object to set forth a methods and apparatuses for providing improved and more reliable services for such dual connectivity UE&#39;s. 
     This object has been solved by at least one of the following methods: 
     A method for a system comprising a mobility management entity, MME, a first Radio Access node, RAN offering Long Term Evolution, LTE, access, and a second radio access node, RAN offering New Radio, NR, access; 
     a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN.
 
     The MME is
         receiving or looking-up internally instances of Radio Access Technology restriction information, RAT RI, from at least two of the HSS, the PCRF and the MME; the instances of RAT RI pertaining to restrictions for a UE as to support dual connectivity over LTE access and NR access respectively for a Packet Data Network, PDN, connectivity session;   resolving a RAT RI from the at least two instances of RAT RI;   transmitting the resolved RAT RI at least to the first RAN;
 
and the first RAN is
   receiving the resolved RAT RI;   enforcing bearer setup in accordance with the resolved RAT RI.       

     A method for a mobility management entity, MME, in a system comprising a first Radio Access node, RAN offering Long Term Evolution, LTE, access, and a second radio access node, RAN offering New Radio, NR, access;
         a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN; and wherein
       

     the MME 
     
         
         
           
             receiving or looking-up instances of Radio Access Technology restriction information, RAT RI, pertaining to restrictions for a UE as to support dual connectivity over LTE and NR for a PDN connectivity session, from at least two of
 
the HSS, the PCRF and internally in the MME;
 
             resolving a RAT RI from the at least two instances of RAT RI&#39;s; 
             transmitting the resolved RAT RI at least to the RAN. 
           
         
       
    
     A method for a first Radio Access node, RAN offering Long Term Evolution, LTE, access in a system comprising a mobility management entity, MME, and a second radio access node, RAN offering New Radio, NR, access; 
     a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT;
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF.
 
     The system is providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN; 
     the MME is moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF; 
     the RAN; 
     
         
         
           
             receiving a resolved RAT RI; 
             enforcing bearer setup in accordance with the resolved RAT RI. 
           
         
       
    
     A method for a Home Subscriber Sever, HSS, in in a system comprising a mobility management entity, MME, a first Radio Access node, RAN offering Long Term Evolution, LTE, access, and a second radio access node, RAN offering New Radio, NR, access; 
     a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN;
 
the method comprising the HSS
 
upon receiving an Update Location Request message from the MME;
         providing an Update Location Response message comprising a RAT RI, having a value indicative of at least the UE&#39;s ability to handle RAT&#39;s to the MME.       

     A method for a gateway entity comprising a SGW and/or PGW, in in a system comprising a mobility management entity, MME, a first Radio Access node, RAN offering Long Term Evolution, LTE, access, and a second radio access node, RAN offering New Radio, NR, access; 
     a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF.
 
     The system is providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN; 
     the gateway entity is
         receiving from the MME a Create Session Request;   transmitting a CCR-I message to the PCRF;   receiving from the PCRF a CCA-I message comprising an instance of RAT RI;   transmitting a create session response message including the received instance of the instance of the RAT RI to the MME.       

     A method for a user entity, UE, in a system comprising a mobility management entity, MME, a first Radio Access node, RAN offering Long Term Evolution, LTE, ac-cess, and a second radio access node, RAN offering New Radio, NR, access; 
     the user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN.
 
     The user entity is being adapted for
         transmitting a PDN connectivity request from a dual connectivity UE comprising an instance of a RAT RI,   receiving from the MME an activate default EPS bearer context request.       

     The object mentioned above has moreover been solved by at least one of: 
     A system comprising a mobility management entity, MME, a first Radio Access node, RAN offering Long Term Evolution, LTE, access, and a second radio access node, RAN offering New Radio, NR, access; 
     a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN;
 
the MME being adapted for
         receiving or looking-up internally instances of Radio Access Technology restriction information, RAT RI, from at least two of the HSS, the PCRF and the MME; the instances of RAT RI pertaining to restrictions for a UE as to support dual connectivity over LTE access and NR access respectively for a Packet Data Network, PDN, connectivity session;   resolving a RAT RI from the at least two instances of RAT RI;   transmitting the resolved RAT RI at least to the first RAN;
 
the first RAN
   receiving the resolved RAT RI;   enforcing bearer setup in accordance with the resolved RAT RI.       

     A mobility management entity, MME, in a system comprising a first Radio Access node, RAN offering Long Term Evolution, LTE, access, and a second radio access node, RAN offering New Radio, NR, access; 
     a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN;
 
the MME comprising processing circuitry being operative to
         receiving or looking-up instances of Radio Access Technology restriction information, RAT RI, pertaining to restrictions for a UE as to support dual connectivity over LTE and NR for a PDN connectivity session, from at least two of
 
the HSS, the PCRF and internally in the MME;
   resolving a RAT RI from the at least two instances of RAT RI&#39;s;   transmitting the resolved RAT RI at least to the RAN.       

     A Radio Access node, RAN offering Long Term Evolution, LTE, access in a system comprising a mobility management entity, MME, and a second radio access node, RAN offering New Radio, NR, access; 
     a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT;
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN;
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
RAN comprising processing circuitry being operative to:
         receiving a resolved RAT RI;   enforcing bearer setup in accordance with the resolved RAT RI.       

     A User entity, UE, in a system comprising a mobility management entity, MME, a first Radio Access node, RAN offering Long Term Evolution, LTE, access, and a second radio access node, RAN offering New Radio, NR, access;
         the user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN;
 
the user entity comprising processing circuitry being adapted for
   transmitting a PDN connectivity request from a dual connectivity UE comprising an instance of a RAT RI,   receiving from the MME an activate default EPS bearer context request.       

     A gateway entity comprising a SGW and/or PGW, in in a system comprising a mobility management entity, MME, a first Radio Access node, RAN offering Long Term Evolution, LTE, access, and a second radio access node, RAN offering New Radio, NR, access; 
     a user entity, UE, supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS, a Serving Packet Data Network Gateway, a PDN Gateway, and a Policy and Charging Rules Function, PCRF;
 
the system providing control plane functionality via the first RAN and user plane functionality via either the first RAN or the second RAN;
 
the gateway entity comprising processing circuitry being adapted for
         receiving from the MME a Create Session Request;   transmitting a CCR-I message to the PCRF;   receiving from the PCRF a CCA-I message comprising an instance of RAT RI;   transmitting a create session response message including the received instance of the instance of the RAT RI to the MME.       

     According to an embodiment of the invention IMS services, such as VoLTE and ViLTE services, can be provided reliably. The services may moreover be dependent on a UE&#39;s service capability and network policies. 
     According to one aspect during PDN connection setup procedure, if configured in the UE, the UE additionally includes RAT restriction information in the PDN Connectivity Setup Request message. 
     Also during a PDN connection setup procedure, the network decides the RAT restriction for this PDN. The decision can be based on subscription data, roaming agreement, local policy, etc. 
     MME gathers all the information from UE and network and makes the final decision of RAT restriction for this PDN. Then MME transfers the RAT restriction information to eNodeB for each EPS bearer belonging to the PDN. 
     According to one aspect of the invention during a PDN connection setup procedure, if configured in UE, the UE additionally includes RAT restriction information in the PDN Connectivity Setup Request message. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a known reference architecture for a LTE access and core network system for a non-roaming scenario, 
         FIG. 2  shows a known reference architecture for a 5G access and core network system for a non-roaming scenario, 
         FIG. 3  shows a known reference architecture for a LTE and 5G access and 5G core network system, 
         FIG. 4  shows known various options for a user entity having access to the  FIG. 3  system, 
         FIG. 5, 6  show known control plane and user plane interfaces, 
         FIG. 7  shows an embodiment of the invention, 
         FIG. 8  shows additional flow diagrams of embodiments of the invention, 
         FIGS. 9-13  show further embodiments of the invention, 
         FIG. 14  shows examples of how user plane bearers according to embodiments of the invention are enforced, 
         FIG. 15  show various nodes for implementing aspects of the invention, 
         FIG. 16  shows an implementation of aspects of the invention in a virtualized environment, 
         FIG. 17  schematically illustrates a telecommunication network connected via an intermediate network to a host computer, 
         FIG. 18  is a generalized block diagram of a host computer communicating via a base station with a user equipment over a partially wireless connection, 
         FIGS. 19 and 20  are flowcharts illustrating methods implemented in a communication system including a host computer, a base station and a user equipment. 
     
    
    
     DETAILED DESCRIPTION 
     According to aspects of the invention an information element denoted Radio Access Technology restriction information, RAT RI, pertaining to restrictions for a UE as to support dual connectivity over LTE access and NR access respectively for a PDN connectivity session is provided. 
     According to an aspect of the invention, RAT RI indicates whether a dual connectivity UE generally capable of handling LTE and NR is incapable of supporting dual connectivity for IMS services. Also during PDN connection setup procedure, the network decides the RAT restriction for this PDN. The decision can be based on subscription data, roaming agreement, local policy, etc. The MME gathers information from the UE and the network and makes the final decision of RAT restriction for this PDN. Then MME transfers the RAT RI to eNodeB for each EPS bearer belonging to the PDN. 
     Aspects of the invention eNodeB is assisted to make a correct steering between LTE and NR for the EPS bearers based on UE capability. Moreover, subscription data, network policy, etc may be considered. This can help avoid the potential impact on service experience, e.g. VoLTE (Voice over LTE) and ViLTE (Video over LTE), and provide a way for operators to enforce local policy and roaming agreement regarding the usage of NR or LTE. 
     According to an aspect of the invention it is provided that during a PDN connection setup procedure, if configured in the UE, the UE additionally includes Radio Access Technology, RAT, restriction information, RI, in the PDN Connectivity Setup Request message. 
     According to embodiments of the invention, two respective flags indicate a restriction for LTE and NR respectively. The RAT can only be used when it is not restricted by any node as signalled by the flags. The flags may be arranged as two flags (bits) for NR and LTE restriction respectively and signalled by the RAT RI information. If any node sets one bit, the corresponding RAT cannot be used. On the other hand, one node may omit setting any bit (e.g. set value 0) and may thus not infer any restrictions. In theory, there may be the case where no RAT can be used (in which case, the PDN setup should fail), but, it should not happen since the operator should be able to align the policy (and most likely the restriction is on NR). 
     According to the invention the following function tables may be used: 
     
       
         
           
               
            
               
                   
               
               
                 RAT RI (NR; LTE) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Received RAT 
                   
                   
                   
               
               
                 Received RAT 
                 RI from subscrip- 
                 Received RAT 
                   
                 Forwarded value 
               
               
                 RI from UE (PDN 
                 tion data (PDN 
                 RI from PCRF 
                 RAT RI (policy) in 
                 (to ENB) (Bearer 
               
               
                 level) 
                 level) 
                 (PDN level) 
                 MME (PDN level) 
                 level) 
               
               
                   
               
               
                 NR 
                 NR 
                 NR 
                 NR 
                 NR 
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 1 
                 0 
                 0 
                 0 
                 1 
               
               
                 0 
                 1 
                 0 
                 0 
                 1 
               
               
                 0 
                 0 
                 1 
                 0 
                 1 
               
               
                 0 
                 0 
                 0 
                 1 
                 1 
               
               
                 1 
                 1 
                 1 
                 1 
                 1 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                 RAT RI (NR; LTE) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Received RAT 
                   
                   
                   
               
               
                 Received RAT 
                 RI from subscrip- 
                 Received RAT 
                   
                 Forwarded value 
               
               
                 RI from UE (PDN 
                 tion data (PDN 
                 RI from PCRF 
                 RAT RI (policy) in 
                 (to eNB) (Bearer 
               
               
                 level) 
                 level) 
                 (PDN level) 
                 MME (PDN level) 
                 level) 
               
               
                   
               
               
                 LTE 
                 LTE 
                 LTE 
                 LTE 
                 LTE 
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 1 
                 0 
                 0 
                 0 
                 1 
               
               
                 0 
                 1 
                 0 
                 0 
                 1 
               
               
                 0 
                 0 
                 1 
                 0 
                 1 
               
               
                 0 
                 0 
                 0 
                 1 
                 1 
               
               
                 1 
                 1 
                 1 
                 1 
                 1 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
            
               
                   
               
               
                   
                   
                 Exemplary E-RAB 
               
            
           
           
               
               
            
               
                   
                 bearer 
               
               
                 RAT RI (NR; LTE) Forwarded value to eNB 
                 decision in eNB 
               
               
                   
               
            
           
           
               
               
               
            
               
                 NR 
                 LTE 
                   
               
               
                 0 
                 0 
                 No restrictions 
               
               
                 0 
                 1 
                 Traffic scheduled only 
               
               
                   
                   
                 on NR 
               
               
                 1 
                 0 
                 Traffic scheduled 
               
               
                   
                   
                 only on LTE 
               
               
                 1 
                 1 
                 — 
               
               
                   
               
            
           
         
       
     
     Further restrictions, for instance regarding up-link and down-link, may apply for eventually setting up bearers. The bearer set-up enforcement according to the resolved RAT RI indication may according to the invention be applied to operate within—or in connection with—such further restrictions. 
     With regard to the options discussed in 3GPP (3/3a/3x). The outcome of this study was the definition of different radio bearer types:
         MCG (Master Cell Group) bearer (uses only LTE)   MCG split bearer (uses LTE and possibly NR)   SCG (Secondary Cell Group) bearer (uses only NR)   SCG split bearer (uses NR and possibly LTE)       

     If there are no restrictions (NR=0; LTE=0) according to embodiments of the invention, then the RAN (eNB) decides, and based on policy, which radio bearer type to assign to which QCI bearer (e.g. QCI=5 bearer is MCG bearer, QCI=9 bearer is SCG split bearer). 
     If there are further restrictions, then the following is a possible way to apply the enforcement:
         If NR UL (Up-Link) and DL (Down-Link) are restricted (NR=1; LTE=0), then naturally only MCG bearer can be used.   If NR UL is restricted, then SCG bearer cannot be used.   If NR DL is restricted, then SCG bearer cannot be used.       

     Note: there might be other reasons for the RAN to not assign a specific bearer type, e.g. due to frequency being used for NR or load. 
     The enforcement may be further subject to certain CQI&#39;s that apply. E.g. RAN needs to know whether NR is allowed for QCI=6/7/8/9 or whether the UE has a restriction for NR. If the UE has a restriction, then NR may be allowed only for QCI=6/7/9 but not for QCI=8. The actual values of the restricted QCI is configured on eNB. 
     The QoS Class Identifier (QCI) is a mechanism used in 3GPP Long Term Evolution (LTE) networks to ensure bearer traffic is allocated appropriate Quality of Service (QoS). Different bearer traffic requires different QoS and therefore different QCI values. QCI value 9 is typically used for the default bearer of a UE/PDN for non-privileged subscribers. 
     The QoS concept as used in LTE networks is class-based, where each bearer type is assigned one QoS Class Identifier (QCI) by the network. The QCI is a scalar that is used within the access network (namely the eNodeB) as a reference to node specific parameters that control packet forwarding treatment, for example scheduling weight, admission thresholds and linklayer protocol configuration. The QCI is also mapped to transport network layer parameters in the relevant Evolved Packet Core (EPC) core network nodes (for example, the PDN Gateway (P-GW), Mobility Management Entity (MME) and Policy and Charging Rules Function (PCRF)), by preconfigured QCI to Differentiated Services Code Point (DSCP) mapping. According to 3GPP TS 23.203 V15.0.0, (c.f. Table 6.1.7: Standardized QCI characteristics), 15 QCI values are standardized and associated with QCI characteristics in terms of packet forwarding treatment that the bearer traffic receives edge-to-edge between the UE and the P-GW. For example, QCI 5 relates to IMS. 
     In  FIG. 7  an embodiment of the invention is shown for PDN connection establishment in which a RAT restriction information, RAT RI, element is provided in various signals. The RAT RI comprises the exemplary two flags defined above. 
     There is shown a UE, an eNodeB, a MME, a Home Subscriber Server, HSS, a SGW/PGW (S/PGW) and a Policy and Coordination Rules Function, PCRF. In  FIG. 7 , the SGW and PGW is indicated as a collocated gateway entity although it is understood that these nodes could be separate entities. 
     As a first step—1, the UE  101  initiates the PDN connection establishment procedure by sending a PDN Connectivity Request message  61  to MME and may include an instance of a RAT RI by means of an information element as defined above. The PDN connection establishment procedure can be part of the UE initiated attach procedure. 
     2. The MME  103  may optionally be aware of a local policy which applies for the UE in question and performs a look-up internally  62 .
 
3. If the PDN Connectivity Request is part of an attach procedure and the MME  103  does not have the subscription data, the MME sends an Update Location Request  63  to the HSS.
 
4. The HSS  104  sends an Update Location Answer  65  to the MME and includes an instance of a RAT restriction information in the APN (Access Point Name) configuration data for any APN for which that RAT restriction is provisioned.
 
5. The MME sends Create Session Request  67  to SGW  105  and then to PGW  105 .
 
6. the PGW sends a CCR (Credit Control Request)-I  69  to the PCRF  106 .
 
7. The PCRF answers with CCA (Credit Control Answer)-I  71  and includes an instance of the RAT restriction information if it is indicated by local policy.
 
8. The PGW sends Create Session Response  73  to the SGW and then to the MME and includes the RAT restriction information if it is received from PCRF  71 .
 
9. The MME resolves a final RAT restriction based on subscriber data from the HSS, the indication from PGW and the local policy in MME along the lines described above. Then MME sends  75  E-RAB setup Request to eNodeB and includes the resolved RAT restriction information for the E-RAB (E-UTRAN Radio Access Bearer) corresponding to the default bearer. MME also sends an Activate Default EPS Bearer Context request to UE  76 .
 
10. eNodeB enforces bearer set up  77  and answers  79  with an E-RAB setup response. The E-RAB setup is adapted to the properties of the UE in question such that if dual use restrictions apply for the UE in question, these restrictions are taken into consideration in the bearer set up.
 
11. UE responds with Activate Default EPS Bearer Context Accept  81 .
 
     In  FIG. 8 , flow diagrams for MME, eNB and UE according to the embodiments of the invention are shown. 
     As further exemplified in the figures there is provided: 
     Method for a system comprising a mobility management entity, MME  103 , a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  108 , gNB offering New Radio, NR, access; 
     a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
     the MME  103   
     
         
         
           
             receiving  61  or looking-up internally  62  instances of Radio Access Technology restriction information, RAT RI, from at least two of the HSS  104 , the PCRF  106  and the MME  103 ; the instances of RAT RI pertaining to restrictions for a UE as to support dual connectivity over LTE access and NR access respectively for a Packet Data Network, PDN, connectivity session; 
             resolving  74  a RAT RI from the at least two instances of RAT RI; 
             transmitting  75  the resolved RAT RI at least to the first RAN  102 ;
 
the first RAN  102 
 
             receiving  75  the resolved RAT RI; 
             enforcing  77  bearer setup in accordance with the resolved RAT RI. 
           
         
       
    
     The MME may further
         receive a PDN connectivity request  61  comprising an instance of a RAT RI from the UE.       

     According to embodiments, an instance of or resolved value of a RAT RI comprises at least two flags, a first flag indicating that a LTE restriction applies when being set and second flag indicating that a NR restriction applies when being set, the resolving  74  involving that any received instance of a RAT RI having a set flag for a respective RAT implies a set flag in the resolved RAT RI, for the corresponding respective RAT. 
     The enforcement involves if in the received resolved RAT RI
         no flags are set-enforcing no restrictions of setting up a user plane bearer on either LTE or NR;   a LTE flag is set-enforcing a restriction of setting up a user plane bearer on LTE access and a allowing traffic to be scheduled only on NR access via the second RAN  108 , gNB;   a NR flag is set-enforcing a restriction of setting up a user plane bearer on NR access and allowing traffic to be scheduled only on LTE access via the first RAN eNB— 102 .       

     In  FIGS. 9-13 , additional procedures are indicated. 
     In  FIG. 9 , a Dedicated Bearer setup with RAT restriction is shown. 
       87 . PGW sends a Create Bearer Request  87  to SGW and then to MME. 
       89 . If RAT restriction is applicable for the PDN on which dedicated bearer is created, MME sends an E-RAB setup Request to eNodeB  89  and includes RAT restriction information for the E-RAB corresponding to the dedicated bearer. 
     RAT RI is on the PDN level. This procedure is for any additional dedicated bearer setup under this PDN. MME will include the RAT RI in the message sent to ENB. One PDN can have one or several bearers. One bearer means on E-RAB and one data radio bearer over air interface 
     In  FIG. 10 , a Service Request with RAT restriction procedure according to an embodiment of the invention is shown moving the UE from idle to connected. RAT RI is stored in MME. When the UE in IDLE state initiates a service request procedure to enter CONNECTED state, MME sends the RAT RI to eNB. 
     UE sends a service request  91  to MME. 
     MME sends an Initial Context Setup request  92  to eNodeB and includes RAT restriction information for any E-RAB belonging to the PDN to which RAT restriction is applicable. eNB can subsequently enforce restrictions for bearer set-up. 
     Hence its is provided that upon the UE transmitting a service request  91  to the MME  103 , the MME  103  may be
         transmitting an Initial Context Setup request  92  to the first RAN  102  comprising an instance of RAT RI for any E-RAB belonging to the PDN to which RAT RI is applicable such that the first RAN  102  can subsequently enforce restrictions for bearer set-up.       

     The system may moreover comprise a further mobility management entity, MME  103 , denoted target MME T-MME, and a further Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, denoted target RAN T-eNB, the first RAN eNB; S-eNB. 
       FIG. 11  shows an embodiment for a S1-based handover with RAT restriction where MME sends the stored RAT RI to a target MME during inter-MME Handover. In this case, i.e. inter-MME handover, source MME sends the stored RAT RI information to target MME and then target MME sends RAT RI information to target ENB. 
     If MME is not changed, then MME sends the stored RAT RI to the target MME. 
     Source eNodeB sends a Handover Required  121  to the source MME. 
     Source MME sends Forward Relocation Request  123  to Target MME and includes an instance of RAT RI restriction information for each applicable PDN. 
     Target MME sends a Handover Request  125  to the target eNodeB and includes RAT restriction information for any E-RAB belonging to PDN to which RAT restriction is applicable. 
     In this procedure, the MME sends the stored RAT RI to eNB. 
     It is thus provided that the system may moreover comprise a further mobility management entity, MME, denoted target MME T-MME, and a further Radio Access Node, RAN eNB offering Long Term Evolution, LTE, access, denoted target RAN T-eNB, 
     the first RAN  102 ; eNB; S-eNB
         transmitting a Handover Required  121  to the MME  103 , S-MME;       

     the MME  103 , S-MME 
     
         
         
           
             transmitting a Forward Relocation Request  123  to the further MME T-MME comprising an instance of RAT RI for each applicable PDN;
 
the further MME T-MME
 
             transmitting a Handover Request  125  to the further RAN T-eNB comprising an instance of RAT RI for any E-RAB belonging to PDN to which RAT RI is applicable. 
           
         
       
    
       FIG. 12  shows a X2-based handover with RAT restriction. In this X2-based handover procedure, source ENB sends the RAT RI to target ENB over X2 interface. 
       131 . Source eNodeB sends X2 AP (application protocol): Handover Request to target eNodeB and includes RAT restriction information for each applicable E-RAB. 
       133 . Target eNodeB acknowledges the request. 
     Hence it is provided, that the system may moreover comprise a further mobility management entity, MME  103 , denoted target MME T-MME, and a further Radio Access Node, RAN  102 , eNB offering Long Term Evolution, LTE, access, denoted target RAN T-eNB, the first RAN eNB; S-eNB, 
     the first RAN  102 , S-eNB
         transmitting  131  a X2 AP Handover Request to the further RAN T-eNB RAT comprising an instance of RAT RI for each applicable radio access bearer;
 
the further RAN T-eNB
   acknowledging  133  the a X2 AP Handover Request to the first RAN  102 , eNB.       

       FIG. 13  shows an embodiment for Traffic Area Update, TAU, with RAT restriction. This is another procedure and accordingly the messages, where MME send the stored RAT RI to the target MME during inter-MME idle mobility 
     The Target MME sends a Context Request  141  to source MME. 
     Source MME sends Context Response  143  to Target MME and includes RAT restriction information for each applicable PDN. 
       FIG. 14  is an exemplary illustration showing the enforced effects for option 3, 3a and 3x for the example where the flag for LTE restriction is set in a resolved RAT RI. In all examples bearers are not allowed between the UE and gNB on the NR interface. 
     In  FIG. 15 , there is shown a user equipment, UE, apparatus according to an embodiment of the invention. 
     The UE comprises a processor PCU_UE an interface IF_UE and a memory, MEM_UE, in which memory instructions are stored for carrying out the method steps explained above. The UE communicates via the interface IF_UE. The IF_UE comprises both an external interface, communicating with a transmitter and receiver, and internal interfaces (not shown). 
     There is also shown a RAN comprising a processor PCU_A, an interface IF_A; and a memory, MEM_A. Instructions are stored in the memory for being performed by the processor such that the method steps explained above are carried out and signalling is communicated on the interface. 
     Further, a MME is provided comprising a processor PCU_M, an interface IF_M; and a memory, MEM_M. Instructions are stored in the memory for being performed by the processor such that the method steps explained above are carried out and signalling is communicated on the interface. 
     Moreover, a PCRF is provided comprising a processor PCU_P, an interface IF_P; and a memory, MEM_P. Instructions are stored in the memory for being performed by the processor such that the method steps explained above are carried out and signalling is communicated on the interface. 
     In  FIG. 15 , there is moreover shown a HSS comprising a processor PCU_S, an interface IF_S; and a memory, MEM_S. Instructions are stored in the memory for being performed by the processor such that the method steps explained above are carried out and signalling is communicated on the interface. 
     Finally, a S/PGW is provided comprising a processor PCU_W an interface IF_W; and a memory, MEM_W. Instructions are stored in the memory for being performed by the processor such that the method steps explained above are carried out and such that corresponding signalling is effectuated on the interface. 
     The above apparatuses/entities are adapted to communicate over known external telecom interfaces or via application programming interfaces, API, as appropriate. 
     It is noted that the features of the methods described above and in the following, may be implemented in software and carried out on a data processing device or other processing circuitry caused by the execution of program code means such as computer-executable instructions. Here and in the following, the term processing circuitry comprises any circuit and/or device suitably adapted to perform the above functions. In particular, the above term comprises general- or special-purpose programmable microprocessors, Digital Signal Processors (DSP), Application Specific Integrated Circuits (ASIC), Programmable Logic Arrays (PLA), Field Programmable Gate Arrays (FPGA), special purpose electronic circuits, etc., or a combination thereof. 
     For example, the program code means may be loaded in a memory, such as a RAM (Random Access Memory), from a storage medium, such as a read-only memory (ROM) or other nonvolatile memory, such as flash memory, or from another device via a suitable data interface, the described features may be implemented by hardwired circuitry instead of software or in combination with software. 
     A computer program or computer program product is provided carrying out the method steps defined above. 
     The methods discussed above may alternatively be implemented by means of a system based on network functions virtualization. In  FIG. 16 , further embodiments of the invention are implemented by means of such a network function virtualization system, NFVS, formed on e.g. general-purpose servers, standard storage and switches. The NFVS may be arranged along the lines described in  FIG. 4 , ETSI GS NFV 002 V. 1.1.1 (2013 October) and comprises the following elements: A NFV management and orchestration system comprising an Orchestrator, ORCH, a VNF manager, VNF_MGR, and a virtualised Infrastructure manager, VIRT_INFRA_MGR. The NFVS moreover comprises an operational/business support system, OP/BUSS_SUPP_SYST; a number of virtual network function instances, VNF, by which the method steps explained above are instantiated; and a virtualised infrastructure, VIRT_INFRA. The VIRT_INFRA comprises a virtual computing, VIRT_COMP, virtual network; VIRT_NETW, and virtual memory, VIRT_MEM, a virtualisation layer, VIRT_LAYER, (e.g. hypervisor) and shared hardware resources, SHARED_HARDW_RES comprising computing devices, COMP, network devices, NETW, comprising e.g. standard switches and other network devices, and standard data storage devices, MEM. 
     According to embodiments of the invention the following methods are disclosed, that may be implemented in the  FIG. 15  or  FIG. 16  realisations: 
     Method for a mobility management entity, MME  103 , in a system comprising a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; 
     a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
     the MME  103   
     
         
         
           
             receiving  61  or looking-up  62  instances of Radio Access Technology restriction information, RAT RI, pertaining to restrictions for a UE as to support dual connectivity over LTE and NR for a PDN connectivity session, from at least two of
 
the HSS  104 , the PCRF  106  and internally in the MME  103 ;
 
             resolving  74  a RAT RI from the at least two instances of RAT RI&#39;s; 
             transmitting  75  the resolved RAT RI at least to the RAN  102 . 
           
         
       
    
     Method for a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access in a system comprising a mobility management entity, MME  103 , and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; 
     a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT;
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
     the RAN  102 ; 
     
         
         
           
             receiving  75  a resolved RAT RI; 
             enforcing  77  bearer setup in accordance with the resolved RAT RI. 
           
         
       
    
     A method may comprise further
         receiving  61  a PDN connectivity request from a dual connectivity UE comprising an instance of a RAT RI,   forwarding  61  the PDN connectivity request to the MME  103 ;   receiving  75  from the MME an E-RAB setup request comprising the resolved RAT RI.       

     The enforcement involves 
     if in the received resolved RAT RI
         no flags are set-enforcing no restrictions of setting up a user plane bearer on either LTE or NR;   if a LTE flag is set enforcing a restriction of setting up a user plane bearer on LTE and a allowing traffic to be scheduled only on NR via the second RAN gNB;   if a NR flag is set enforcing a restriction of setting up a user plane bearer on NR and al-lowing traffic to scheduled only on LTE via the first RAN eNB.       

     Method for a Home Subscriber Sever, HSS  104 , in in a system comprising a mobility management entity, MME  103 , a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT, 
     the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the method comprising the HSS
 
upon receiving an Update Location Request message  63  from the MME;
         providing  65  an Update Location Response message comprising a RAT RI, having a value indicative of at least the UE&#39;s ability to handle RAT&#39;s to the MME.       

     Method for a gateway entity  105  comprising a SGW and/or PGW, in in a system comprising a mobility management entity, MME  103 , a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; 
     a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME  103  moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the gateway entity  105 
         receiving  67  from the MME  103  a Create Session Request  67 ;   transmitting  69  a CCR-I message to the PCRF;   receiving  71  from the PCRF a CCA-I message comprising an instance of RAT RI;   transmitting  73  a create session response message including the received instance  71  of the instance of the RAT RI to the MME  103 .       

     Method for a user entity, UE, in a system comprising a mobility management entity, MME  103 , a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; 
     the user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the user entity being adapted for
         transmitting  61  a PDN connectivity request from a dual connectivity UE comprising an instance of a RAT RI,   receiving  76  from the MME an activate default EPS bearer context request.       

     Also one or more programs for a computer or computer program products, comprising instructions for carrying out any of methods according to the method steps above, are provided. 
     According to embodiments of the invention systems and apparatuses are disclosed, that may be realized by means of the  FIG. 15  examples. Alternatively, systems and apparatuses may be instantiated in a cloud computing environment as a virtual node, c.f.  FIG. 16 , the cloud environment comprising shared hardware resources comprising at least computing devices (COMP), memory devices (MEM) and network devices (NETW). 
     A system is provided comprising a mobility management entity, MME  103 , a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  108 , gNB offering New Radio, NR, access; 
     a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT, the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the MME  103  comprising processing circuitry being adapted for
         receiving  61  or looking-up internally  62  instances of Radio Access Technology restriction information, RAT RI, from at least two of the HSS  104 , the PCRF  106  and the MME  103 ; the instances of RAT RI pertaining to restrictions for a UE as to support dual connectivity over LTE access and NR access respectively for a Packet Data Network, PDN, connectivity session;   resolving  74  a RAT RI from the at least two instances of RAT RI;   transmitting  75  the resolved RAT RI at least to the first RAN  102 ;
 
the first RAN  102  comprising processing circuitry operative to
   receiving  75  the resolved RAT RI;   enforcing  77  bearer setup in accordance with the resolved RAT RI.       

     A mobility management entity, MME  103 , is provided in a system comprising a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; 
     a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the MME  103  comprising processing circuitry being operative to
         receiving  61  or looking-up  62  instances of Radio Access Technology restriction information, RAT RI, pertaining to restrictions for a UE as to support dual connectivity over LTE and NR for a PDN connectivity session, from at least two of
 
the HSS  104 , the PCRF  106  and internally in the MME  103 ;
   resolving  74  a RAT RI from the at least two instances of RAT RI&#39;s;   transmitting  75  the resolved RAT RI at least to the RAN  102 .       

     In the Mobility management entity, MME  103 , the processing circuitry can comprise a memory MEM-M, a processor PCU-M and an interface IF-M, the processor being adapted for executing instructions stored in the memory. 
     Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access in a system comprising a mobility management entity, MME  103 , and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; 
     a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT;
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
RAN  102  comprising processing circuitry being operative to:
         receiving  75  a resolved RAT RI;   enforcing  77  bearer setup in accordance with the resolved RAT RI.       

     The RAN may be further being adapted to
         receiving  61  a PDN connectivity request from a dual connectivity UE comprising an instance of a RAT RI,   forwarding  61  the PDN connectivity request to the MME  103 ;   receiving  75  from the MME an E-RAB setup request comprising the resolved RAT RI.       

     In the RAN, the enforcement may involve 
     if in the received resolved RAT RI
         no flags are set-enforcing no restrictions of setting up a user plane bearer on either LTE or NR;   if a LTE flag is set enforcing a restriction of setting up a user plane bearer on LTE and a allowing traffic to be scheduled only on NR via the second RAN gNB;   if a NR flag is set enforcing a restriction of setting up a user plane bearer on NR and al-lowing traffic to scheduled only on LTE via the first RAN eNB.       

     The system or any node may be instantiated in a cloud computing environment as a virtual node, the cloud environment comprising shared hardware resources comprising at least computing devices COMP, memory devices MEM and network devices NETW. 
     A User Entity, UE  101 , is provided in a system comprising a mobility management entity, MME  103 , a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; 
     the user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the user entity  101  comprises processing circuitry being adapted for
         transmitting  61  a PDN connectivity request from a dual connectivity UE comprising an instance of a RAT RI,   receiving  76  from the MME an activate default EPS bearer context request.       

     The UE processing circuitry may comprise a memory MEM-U, a processor PCU-UE and an interface IF-UE, the processor being adapted for executing instructions stored in the memory. 
     A gateway entity  105 , S/PGW is provided comprising a SGW and/or PGW, in in a system comprising a mobility management entity, MME  103 , a first Radio Access node, RAN  102 , eNB offering Long Term Evolution, LTE, access, and a second radio access node, RAN  107 , gNB offering New Radio, NR, access; 
     a user entity, UE  101 , supporting both Long Term Evolution, LTE, and New Radio, NR, Radio Access Technology, RAT,
 
the MME  103  moreover being adapted for signalling with a Home Subscription Server, HSS  104 , a Serving Packet Data Network PDN Gateway, a PDN Gateway  105 , and a Policy and Charging Rules Function, PCRF  106 ;
 
the system providing control plane functionality via the first RAN  102 , eNB and user plane functionality via either the first RAN or the second RAN;
 
the gateway entity  105  comprising processing circuitry being adapted for
         receiving  67  from the MME  103  a Create Session Request  67 ;   transmitting  69  a CCR-I message to the PCRF;   receiving  71  from the PCRF a CCA-I message comprising an instance of RAT RI;   transmitting  73  a create session response message including the received instance  71  of the instance of the RAT RI to the MME  103 .       

     In the gateway the processing circuitry comprises a memory MEM-W, a processor PCU-W and an interface IF-W, the processor being adapted for executing instructions stored in the memory. 
     With reference to  FIG. 17 , in accordance with an embodiment, a communication system includes a telecommunication network  3210 , such as a 3GPP-type cellular network, which comprises an access network  3211 , such as a radio access network, and a core network  3214 . The access network  3211  comprises a plurality of base stations  3212   a ,  3212   b ,  3212   c , such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area  3213   a ,  3213   b ,  3213   c . Each base station  3212   a ,  3212   b ,  3212   c  is connectable to the core network  3214  over a wired or wireless connection  3215 . A first user equipment (UE)  3291  located in coverage area  3213   c  is configured to wirelessly connect to, or be paged by, the corresponding base station  3212   c . A second UE  3292  in coverage area  3213   a  is wirelessly connectable to the corresponding base station  3212   a . While a plurality of UEs  3291 ,  3292  are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station  3212 . The telecommunication network  3210  is itself connected to a host computer  3230 , which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer  3230  may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections  3221 ,  3222  between the telecommunication network  3210  and the host computer  3230  may extend directly from the core network  3214  to the host computer  3230  or may go via an optional intermediate network  3220 . The intermediate network  3220  may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network  3220 , if any, may be a backbone network or the Internet; in particular, the intermediate network  3220  may comprise two or more subnetworks (not shown). 
     The communication system of  FIG. 17  as a whole enables connectivity between one of the connected UEs  3291 ,  3292  and the host computer  3230 . The connectivity may be described as an over-the-top (OTT) connection  3250 . The host computer  3230  and the connected UEs  3291 ,  3292  are configured to communicate data and/or signalling via the OTT connection  3250 , using the access network  3211 , the core network  3214 , any intermediate network  3220  and possible further infrastructure (not shown) as intermediaries. The OTT connection  3250  may be transparent in the sense that the participating communication devices through which the OTT connection  3250  passes are unaware of routing of uplink and downlink communications. For example, a base station  3212  may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer  3230  to be forwarded (e.g., handed over) to a connected UE  3291 . Similarly, the base station  3212  need not be aware of the future routing of an outgoing uplink communication originating from the UE  3291  towards the host computer  3230 . 
     Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to  FIG. 18 . In a communication system  3300 , a host computer  3310  comprises hardware  3315  including a communication interface  3316  configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system  3300 . The host computer  3310  further comprises processing circuitry  3318 , which may have storage and/or processing capabilities. In particular, the processing circuitry  3318  may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer  3310  further comprises software  3311 , which is stored in or accessible by the host computer  3310  and executable by the processing circuitry  3318 . The software  3311  includes a host application  3312 . The host application  3312  may be operable to provide a service to a remote user, such as a UE  3330  connecting via an OTT connection  3350  terminating at the UE  3330  and the host computer  3310 . In providing the service to the remote user, the host application  3312  may provide user data which is transmitted using the OTT connection  3350 . The communication system  3300  further includes a base station  3320  provided in a telecommunication system and comprising hardware  3325  enabling it to communicate with the host computer  3310  and with the UE  3330 . The hardware  3325  may include a communication interface  3326  for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system  3300 , as well as a radio interface  3327  for setting up and maintaining at least a wireless connection  3370  with a UE  3330  located in a coverage area (not shown in  FIG. 18 ) served by the base station  3320 . The communication interface  3326  may be configured to facilitate a connection  3360  to the host computer  3310 . The connection  3360  may be direct or it may pass through a core network (not shown in  FIG. 18 ) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware  3325  of the base station  3320  further includes processing circuitry  3328 , which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station  3320  further has software  3321  stored internally or accessible via an external connection. 
     The communication system  3300  further includes the UE  3330  already referred to. Its hardware  3335  may include a radio interface  3337  configured to set up and maintain a wireless connection  3370  with a base station serving a coverage area in which the UE  3330  is currently located. The hardware  3335  of the UE  3330  further includes processing circuitry  3338 , which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE  3330  further comprises software  3331 , which is stored in or accessible by the UE  3330  and executable by the processing circuitry  3338 . The software  3331  includes a client application  3332 . The client application  3332  may be operable to provide a service to a human or nonhuman user via the UE  3330 , with the support of the host computer  3310 . In the host computer  3310 , an executing host application  3312  may communicate with the executing client application  3332  via the OTT connection  3350  terminating at the UE  3330  and the host computer  3310 . In providing the service to the user, the client application  3332  may receive request data from the host application  3312  and provide user data in response to the request data. The OTT connection  3350  may transfer both the request data and the user data. The client application  3332  may interact with the user to generate the user data that it provides. 
     It is noted that the host computer  3310 , base station  3320  and UE  3330  illustrated in  FIG. 18  may be identical to the host computer  3230 , one of the base stations  3212   a ,  3212   b ,  3212   c  and one of the UEs  3291 ,  3292  of  FIG. 17 , respectively. This is to say, the inner workings of these entities may be as shown in  FIG. 18  and independently, the surrounding network topology may be that of  FIG. 17 . 
     In  FIG. 18 , the OTT connection  3350  has been drawn abstractly to illustrate the communication between the host computer  3310  and the use equipment  3330  via the base station  3320 , without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE  3330  or from the service provider operating the host computer  3310 , or both. While the OTT connection  3350  is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., since load balancing consideration or reconfiguration of the network). 
     The wireless connection  3370  between the UE  3330  and the base station  3320  is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE  3330  using the OTT connection  3350 , in which the wireless connection  3370  forms the last segment. More precisely, the teachings of these embodiments may improve the services for such dual connectivity UE&#39;s. 
     A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection  3350  between the host computer  3310  and UE  3330 , in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection  3350  may be implemented in the software  3311  of the host computer  3310  or in the software  3331  of the UE  3330 , or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection  3350  passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software  3311 ,  3331  may compute or estimate the monitored quantities. The reconfiguring of the OTT connection  3350  may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station  3320 , and it may be unknown or imperceptible to the base station  3320 . Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signalling facilitating the host computer&#39;s  3310  measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software  3311 ,  3331  causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection  3350  while it monitors propagation times, errors etc. 
       FIG. 19  is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE. For simplicity of the present disclosure, only drawing references to  FIG. 19  will be included in this section. In a first step  3410  of the method, the host computer provides user data. In an optional sub step  3411  of the first step  3410 , the host computer provides the user data by executing a host application. In a second step  3420 , the host computer initiates a transmission carrying the user data to the UE. In an optional third step  3430 , the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth step  3440 , the UE executes a client application associated with the host application executed by the host computer. 
       FIG. 20  is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE. For simplicity of the present disclosure, only drawing references to  FIG. 20  will be included in this section. In a first step  3510  of the method, the host computer provides user data. In an optional sub-step (not shown) the host computer provides the user data by executing a host application. In a second step  3520 , the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step  3530 , the UE receives the user data carried in the transmission. 
     Further Numbered Embodiments 
     
         
         1. A communication system including a host computer comprising:
       processing circuitry configured to provide user data; and   a communication interface configured to forward the user data to a cellular network for transmission to a user equipment (UE),   wherein the cellular network comprises a base station having a radio interface and processing circuitry, the base station&#39;s processing circuitry configured to—receiving ( 75 ) a resolved RAT RI; —enforcing ( 77 ) bearer setup in accordance with the resolved RAT RI.   
     
         2. The communication system of embodiment 1, further including the base station. 
         3. The communication system of embodiment 2, further including the UE, wherein the UE is configured to communicate with the base station. 
         4. The communication system of embodiment 3, wherein:
       the processing circuitry of the host computer is configured to execute a host application, thereby providing the user data; and   the UE comprises processing circuitry configured to execute a client application associated with the host application.   
     
         5. A method implemented in a communication system including a host computer, a base station and a user equipment (UE), the method comprising:
       at the host computer, providing user data; and   at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station, wherein the base station—receiving ( 75 ) a resolved RAT RI; —enforcing ( 77 ) bearer setup in accordance with the resolved RAT RI.   
     
         6. The method of embodiment 5, further comprising:
       at the base station, transmitting the user data.   
     
         7. The method of embodiment 6, wherein the user data is provided at the host computer by executing a host application, the method further comprising:
       at the UE, executing a client application associated with the host application.   
     
         8. A communication system including a host computer comprising:
       processing circuitry configured to provide user data; and   a communication interface configured to forward user data to a cellular network for transmission to a user equipment (UE),   wherein the UE comprises a radio interface and processing circuitry, the UE&#39;s processing circuitry configured to—transmitting ( 61 ) a PDN connectivity request from a dual connectivity UE comprising an instance of a RAT RI, —receiving ( 76 ) from the MME an activate default EPS bearer con-text request.   
     
         9. The communication system of embodiment 8, further including the UE. 
         10. The communication system of embodiment 9, wherein the cellular network further includes a base station configured to communicate with the UE. 
         11. The communication system of embodiment 8 or 9, wherein:
       the processing circuitry of the host computer is configured to execute a host application, thereby providing the user data; and   the UE&#39;s processing circuitry is configured to execute a client application associated with the host application.   
     
         13. A method implemented in a communication system including a host computer, a base station and a user equipment (UE), the method comprising:
       at the host computer, providing user data; and   at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station, wherein the UE—transmitting ( 61 ) a PDN connectivity request from a dual connectivity UE comprising an instance of a RAT RI, —receiving ( 76 ) from the MME an activate default EPS bearer context request.   
     
         14. The method of embodiment 35, further comprising:
       at the UE, receiving the user data from the base station.