Patent Publication Number: US-11399322-B2

Title: User equipment, network node and methods in a wireless communications network

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a User Equipment, UE, a source network node and methods therein, for resuming a Radio Resource Control, RRC, connection of the UE to a target cell in a wireless communications network. 
     BACKGROUND 
     In a typical wireless communications network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or User Equipments (UE), communicate via a Local Area Network such as a Wi-Fi network or a Radio Access Network (RAN) to one or more Core Networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio network node such as a radio access node e.g., a Wi-Fi access point or a Radio Base Station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in 5G. A service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio network node. 
     Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network also referred to as 5G New Radio (NR). The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs used in 3G networks. In general, in E-UTRAN/LTE the functions of a 3G RNC are distributed between the radio network nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio network nodes, this interface being denoted the X2 interface. 
     The wireless communications network described in this disclosure may involve any of the above example networks and will frequently be referred to herein as “the network” for short. 
     Multi-antenna techniques may significantly increase the data rates and reliability of a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO. 
     Radio Resource Control, RRC, Connection Resume 
     The RRC state model is updated in NR and in eLTE, i.e. LTE connected to 5GC, and a new RRC_INACTIVE state is introduced in addition to the existing RRC_IDLE and RRC_CONNECTED states inherited from LTE. In RRC_INACTIVE, a UE context from the previous RRC connection is stored in the RAN and is re-used next time an RRC connection is established. The UE context includes information such as the UE security configuration, configured radio bearers, etc. By storing the UE context in the RAN, the signaling required for security activation and bearer establishment can be avoided, which is normally required when transitioning from RRC_lDLE to RRC_CONNECTED. Storing and re-using the UE context improves latency and reduces the signaling overhead. 
     RRC_INACTIVE mode is realized by introducing two new procedures referred to as “RRC connection suspend”, also called “RRC connection release with SuspendConfig”, and “RRC connection resume”. The gNB suspends a connection and moves the UE from RRC_CONNECTED to RRC_INACTIVE by sending a RRC release message with suspend indication (or configuration) to the UE. This is illustrated in  FIG. 1 . Suspension of the connection may be performed for example after the UE has been inactive for a certain period which causes an internal inactivity tinier in the gNB to expire, as indicated in  FIG. 1 . Both the UE and the gNB store the UE context and an associated identifier, referred to as I-Radio Network Temporary Identifier, I-RNTI. It has been recently updated that two identifiers will be configured in the suspend configuration, a long I-RNTI and a short I-RNTI. The identifier to be used in a resume procedure depends on an indication from the network in system information of the cell the UE tries to resume in. The above two I-RNTI identifiers were introduced to support scenarios when the UE is resuming in a cell which only gives the UE a small scheduling grant for the first UL message. For this purpose, also two different resume messages have been introduced namely RRCResumeRequest and RRCResumeRequest1. In the following disclosure, the term “RRC resume request” is used to refer to either of the two messages. 
     At the next transition to RRC_CONNECTED, the UE resumes the connection by sending a RRC resume request including the following information to the gNB of a target cell towards which the UE attempts to resume the connection. A signaling procedure for resuming a connection of the UE to the target cell/gNB is illustrated in  FIG. 2 . It should be noted that the target cell/gNB may be another cell/gNB compared to the cell/gNB where the connection was suspended, in  FIG. 2  denoted source gNB. 
     The RRC resume request sent by the UE at 2:1 comprises the following information:
         The I-RNTI (either the long or short I-RNTI depending on the system information indication)   A security token (called resumeMAC-I in the specification) which is used to identify and verify the UE at RRC connection resume   An indication of the cause of the resume, e.g, mobile originated data, denoted resume cause in  FIG. 2 .       

     The gNB which serves the cell in which the UE is resuming is sometimes referred to as the target gNB, while the gNB serving the cell in which the UE was suspended in is sometimes referred to as the source gNB, as indicated in  FIG. 2 . To resume the connection, the target gNB determines which gNB is the source gNB, considering the gNB part of the I-RNTI, and requests that gNB at 2:2 to send the UE&#39;s context. In the request the target provides, among other things, the UE ID and security token received from the UE as well as the target cell Cell ID. 
     At 2:3, the source gNB then locates and fetches the UE context based on the I-RNTI and verifies the request based on the security token which could be done in a manner to be described below. If successful, the gNB forwards the UE context to the target gNB at 2:4, which then responds to the UE with RRC resume at 2:5, to confirm the connection is being resumed. Finally, the UE acknowledges the reception of the RRC resume by sending a RRC resume complete at 2:6. Thereby, the UE is able to transmit uplink (UL) data to the target gNB and the target gNB is able to transmit downlink (DL) data to the UE on the resumed connection, as indicated by respective dashed arrows. 
     It should be noted that the RRC resume procedure works in a similar way in LTE and eLTE. 
     Security Token Calculation for RRC Connection Resume 
     The security token included in the RRC resume request is verified by the source gNB and assures the network that the request originated from the correct UE, The security token is calculated using an integrity key K RRCint  derived from the source gNB base key K gNB  with the following additional inputs:
         Source C-RNTI   Source PCI   Target Cell Identity, ID       

     From a security perspective, a significant parameter of the parameters above is the target Cell ID. The Cell ID uniquely identifies a cell within a PLMN, and by including the target Cell ID in the calculation the security token is bound to the target cell. This ensures that the security token can only be used within the intended cell, and if an attacker intercepts the security token, which could be done as the resume requests are sent on SRB0, i.e., without encryption, and uses the intercepted security token in a request in some other cell the request will be rejected since the target Cell ID is different from the Cell ID of said other cell. 
     The calculation of the security token, in NR called resumeMAC-I which is represented by a 16 bit string, is described as follows in the RRC specification, see section 5.3.13.3 in TS 38.331 1 and R2-1813492, CR to 38.331 “Introduction of NR SA”): 
     5.3.13.3 Actions Related to Transmission of RRCResumeRequest or RRCResumeRequest1 Message 
     The UE shall set the contents of RRCResumeRequest or RRCResumeRequest1 message as follows: 
     1&gt; set the resumeMAC-I to the 16 least significant bits of the MAC-I calculated:
         2&gt; over the ASN.1 encoded as per section 8 (i.e., a multiple of 8 bits) VarResumeMAC-Input;   2&gt; with the K RRCint  key and the previously configured integrity protection algorithm; and   2&gt; with at input bits for COUNT, BEARER and DIRECTION set to binary ones;       

     Editor&#39;s Note: FFS Additional input to VarResumeMAC-Input (replay attacks mitigation). 
     Furthermore, the input variables to the security token are described in detail as a UE variable called VarResumeMAC-Input which is described as follows in the RRC specifications, see section 7.4 in TS 38.331 1 and R2-1813492, CR to 38.331 “Introduction of NR SA”: 
     UE Variables 
     VarResumeMAC-Input 
     The UE variable VarResumeMAC-Input specifies the input used to generate the resurneMAC-I during RRC Connection Resume procedure. 
     
       
         
           
               
             
               
                   
               
               
                 VarResumeMAC-Input variable 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 -- ASN1START 
               
               
                 -- TAG-VAR-RESUMEMACINPUT-START 
               
            
           
           
               
               
            
               
                 VarResumeMAC-Input ::= 
                 SEQUENCE { 
               
            
           
           
               
               
            
               
                     sourcePhysCellId 
                 PhysCellId, 
               
               
                     targetCellIdentity 
                 CellIdentity, 
               
               
                     source-c-RNTI 
                 RNTI-Value 
               
               
                 } 
               
               
                 -- TAG-VAR-RESUMEMACINPUT-STOP 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     VarResumeMAC-Input Field Descriptions 
     targetCellIdentity 
     Set to CellIdentity of the target cell i.e. the cell the UE is trying to resume. 
     Source-c-RNTI 
     Set to C-RNTI that the UE had in the PCell it was connected to prior to suspension of the RRC connection. 
     SourcePhysCellId 
     Set to the physical cell identity of the PCell the UE was connected to prior to suspension of the RRC connection. 
     Editor&#39;s Note: FFS Additional input to VarResumeMAC-Input (replay attacks mitigation). 
     As mentioned above, the security token is the 16 least significant bytes of the MAC-I. In LTE and NR, integrity protection of messages is performed in the Packet Data Convergence Protocol (PDCP) in both the network and the UE by computing a Message Authentication Code—Integrity (MAC-I) which is included in the PDCP header. The MAC-I is a secure checksum calculated using an integrity protection algorithm. When the receiver receives the PDCP packet it computes and verifies the MAC-I using the same inputs and algorithms as the transmitter has used, so that each side can be authenticated. The derivations are specified in TS 33.401 and TS 33.501 for EPS and 5GS respectively, although the only difference is which algorithms are applied. For LTE connected to either EPC or 5GC, the algorithms used are defined in TS 33.401, while for NR, the algorithms used are defined in 33.501. Unlike the MAC-I which is included at and verified by the PDCP layer, the security token is included and verified at the RRC layer. 
     Below is an excerpt from the 5G security specification, see section D.3.1.1 in TS 33.501 2 and 3GPP TS 33.501 “Security architecture and procedures for 5G System”, v15.1.0, for the derivation of the MAC-I: 
     Inputs and Outputs 
     The input parameters to the integrity algorithm are a 128-bit integrity key named KEY, a 32-bit COUNT, a 5-bit bearer identity called BEARER, the 1-bit direction of the transmission i.e. DIRECTION, and the message itself i.e. MESSAGE. The DIRECTION bit shall be 0 for uplink and 1 for downlink. The bit length of the MESSAGE is LENGTH. 
       FIG. 3  illustrates Derivation of MAC-I/NAS-MAC (or XMAC-I/XNAS-MAC), the use of the integrity algorithm NIA to authenticate the integrity of messages. 
     Based on these input parameters, the sender of a message computes a 32-bit message authentication code (MAC-I/NAS-MAC) using the integrity algorithm NIA. The computed message authentication code is then appended to the message when sent. For integrity protection algorithms, the receiver of the message computes an expected message authentication code (XMAC-I/XNAS-MAC) on the message received in the same way as the sender computed its message authentication code on the message sent, and verifies the data integrity of the message by comparing the computed message authentication code to the received message authentication code, i.e. MAC-I/NAS-MAC. If the computed message authentication code matches the received message authentication code, the message is verified. 
     In  FIG. 3 , it is thus illustrated how the sender generates the message authentication code denoted MAC-I/NAS-MAC by using the parameters KEY, COUNT, MESSAGE, DIRECTION and BEARER as input to the NIA. In the same manner, the receiver generates the expected message authentication code denoted XMAC-I/XNAS-MAC by using the same parameters KEY, COUNT, MESSAGE, DIRECTION and BEARER as input to the same integrity algorithm NIA. The message is verified by the receiver if the received MAC-I/NAS-MAC matches, e.g. equals, the computed XMAC-I/XNAS-MAC. 
     However, it may be a problem that the above-described Cell ID is sometimes not globally unique across multiple PLMNs so that when the Cell ID is included in the security token calculation, the security token might not be bound to one and the same cell, resulting in reduced security in the network. 
     SUMMARY 
     It is an object of embodiments described herein to address at least some of the problems and issues outlined above. It is possible to achieve this object and others by using a UE, a source network node and methods therein, as defined in the attached independent claims. 
     According to one aspect, a method is performed by a User Equipment, UE, for resuming a Radio Resource Control, RRC, connection to a target cell in a wireless communications network. In this method, when the target cell has been found, the UE generates a security token, wherein an input value in a security token generating function comprises a set of input parameters, which set of input parameters comprises at least a cell identifier of the target cell arid an indication of a Public Land Mobile Network, PLMN, of the target cell. The UE further sends a resuming request to a target network node serving the target cell, which resuming request comprises the security token. 
     According to another aspect, a User Equipment, UE, is configured for resuming a Radio Resource Control, RRC, connection to a target cell in a wireless communications network. When the target cell is found, the UE is configured to generate a security token, wherein an input value in a security token generating function is adapted to comprise a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier of the target cell and an indication of a Public Land Mobile Network, PLMN, of the target cell. The UE is further configured to send a resuming request to a target network node serving the target cell, which resuming request is adapted to comprise the security token. 
     According to another aspect, a method is performed by a source network node for resuming a Radio Resource Control, RRC, connection of a User Equipment, UE, to a target cell in a wireless communications network. In this method, the source network node receives from a target network node serving the target cell, a security token, and the source network node then generates a security token itself. When generating the security token, an input value in a security token generating function comprises a set of input parameters, which set of input parameters comprises at least a cell identifier of the target cell and an indication of a Public Land Mobile Network, PLMN, of the target cell. 
     If the received security token is successfully verified when compared with the generated security token, the source network node provides to the target network node a UE context related to the RRC connection of the UE, to enable the target network node to resume the RRC connection. 
     According to another aspect, a source network node is configured for resuming a Radio Resource Control, RRC, connection of a User Equipment, UE, to a target cell in a wireless communications network. The source network node is configured to receive from a target network node serving the target cell, a security token, arid to generate a security token. When generating the security token, an input value in a security token generating function is adapted to comprise a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier of the target cell and an indication of a Public Land Mobile Network, PLMN, of the target cell. 
     If the received security token is successfully verified when compared with the generated security token, the source network node is configured to provide to the target network node a UE context related to the RRC connection of the UE, to enable the target network node to resume the RRC connection. 
     When using either of the above methods, UE and source network node, it is an advantage that the security token generated by both the UE and the source network node indicates or represents a unique combination of the intended target cell and the PLMN of the target cell, so that the security token can only be used to resume a connection within the intended target cell. This effectively prevents an attacker, having intercepted the security token, to resume an RRC connection with some other cell by using the intercepted security token in an RRC resuming request. This is because the RRC resuming request will be rejected as the security token therein does not match the intended other cell. 
     The above methods, UE and source network node may be configured and implemented according to different optional embodiments to accomplish further features and benefits, to be described below. 
     A computer program is also provided comprising instructions which, when executed on at least one processor in either of the above UE and source network node, cause the at least one processor to carry out the respective methods described above. A carrier is also provided which contains the above computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. It should be noted that the above processor may also be referred to as a processing circuitry which is basically a synonym for processor. Throughout this description, the term processor could thus be substituted by “processing circuitry”. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which: 
         FIG. 1  is a communication sequence illustrating how a gNB suspends a connection by moving a UE from RRC Connected to RRC Inactive after a period of inactivity, according to the prior art. 
         FIG. 2  is a communication sequence illustrating how the UE resumes the connection by sending a RRC resume request to the gNB, according to the prior art. 
         FIG. 3  illustrates how a message authentication code can be computed by a sender and by a receiver, respectively, which may be useful for the embodiments herein. 
         FIG. 4  is a schematic overview depicting a wireless communications network where the embodiments herein may be used. 
         FIG. 5  is a flow chart illustrating a procedure in a UE, according to some example embodiments. 
         FIG. 6  is a flow chart illustrating a procedure in a source network node, according to further example embodiments. 
         FIGS. 7 a  and 7 b    are block diagrams illustrating how a UE may be structured, according to further example embodiments. 
         FIGS. 8 a  and 8 b    are block diagrams illustrating how a source network node may be structured, according to further example embodiments. 
         FIGS. 9-14  illustrate further scenarios, structures and procedures that may be employed when the solution is used, according to further possible embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     As a part of developing embodiments herein, various problems which have been identified in existing solutions for determining a security token, will now be discussed. 
     First, some existing solution for security token calculation will be briefly described. 
     In NR and LTE/eLTE, the security token needs to be calculated when a UE tries to resume an RRC connection. That can either be an NR or eLTE (LTE connected to 5GC) UE coming from RRC_INACTIVE state, or an RRC_IDLE UE in LTE with a suspended connection. The UE then uses the parameters in the UE variable associated to the security token which contains the C-RNTI and PCI from the source cell, stored by the UE when the UE was suspended, and the target Cell ID obtained from the system information of the target cell. It may be rioted that the field description of the Cell ID simply indicates that this is the cell the UE is trying to resume a connection to. That is, obtained from the system information associated to that cell, more precisely from SIB1 in cellAccessRelatedInfo in the case of NR. 
     If a single target Cell ID is being broadcasted, the currently specified solution is useful for providing security. However, in case of RAN sharing with multiple PLMNs sharing the same cell, there may be more than one Cell ID associated with a cell. For example, if two RANs PLMN A and PLMN B both share the same cell, PLMN A can use one Cell ID while PLMN B use another Cell ID. Compared to using a single common Cell ID, it is a benefit that the PLMNs can plan their networks without having to coordinate the Cell IDs used for the cells in the respective networks. Which Cell ID to use as input to the security token calculation in a RAN sharing scenario may focus on RRC connection resume and RAN sharing in LTE but most of the problems and solutions discussed herein apply to the NR case as well. 
     For example, either of the following two alternatives may be applied to determine which Cell ID to use as input to the security token calculation:
         the UE uses the Cell ID associated with the so-called primary PLMN which is the PLMN occurring first in the broadcasted PLMN list, and   the UE uses the Cell ID associated with its selected PLMN which is the UE&#39;s registered PLMN or an equivalent PLMN.       

     Using the Cell ID of the selected PLMN according to the second alternative above is arguably a preferable solution. However, the input parameters including the exact target cell ID to use for the calculation of the Resume MAC-I must be known at both the UE and at the source gNB or any other network node that needs to verify the UE before sending the UE context to the target gNB, in order to enable safe verification of the security token. Further, it is not certain that the PLMN selected by the UE at the target cell is the same as the PLMN previously selected which can be part of the UE context. One reason for that difference in PLMNs may be when the UE reselects to an equivalent PLMN. In that case, that selected PLMN is only indicated to the network in the RRC resume complete message, while the Resume MAC-I shall be computed by the network upon receiving RRC resume request message which occurs at 2:1 before the RRC resume complete message at 2:6, as shown in  FIG. 2 . Two options for solving this problem may be:
         The UE may indicate the selected PLMN already in the RRC resume request. However, due the strict size constraint of the RRC resume request message this option may not be possible to use.   The source gNB may include the Cell IDs of all PLMNs in the Xn retrieve UE context request and the source gNB determines which one to use. This can be achieved by the source gNB by trying each Cell ID in turn until the token verification either succeeds or all Cell IDs have been attempted. Alternatively, the source gNB can use the information stored in the UE context to determine the registered PLMN and then use this information to determine the selected PLMN and the associated Cell ID.       

     Some problems that may occur when an existing solution for security token calculation, will now be identified. 
     An important security property of the security token used in RRC connection resume is that the security token is only valid within a specific cell. This ensures that a security token that is intercepted in one cell by an attacker cannot be used to resume a connection in another cell. As described above, this can be accomplished by including the Cell ID in the security token calculation. However, when RRC resume is combined with RAN sharing of cells, the Cell ID no longer uniquely identifies a cell as the same Cell ID may be used by several PLMNs, The Cell ID collisions that can occur differ depending on which solution is adopted, i.e. which Cell ID that is used as input to the security token calculation according to either of Case 1 and Case 2 below: 
     Case 1: The primary PLMN Cell ID, which is the Cell ID associated with the first PLMN in the broadcasted PLMN list, is used as input to the security token calculation. 
     In this case, a security token generated in one cell will be valid also in other cells if the primary PLMN of the other cell uses the same Cell ID as the primary PLMN of the first cell. The same is true also when the Cell ID is selected according to similar rules, e.g. the Cell ID associated with the i:th PLMN in the broadcasted PLMN list. 
     Case 2: The selected PLMN Cell ID, which is the Cell ID associated with the registered PLMN or an equivalent PLMN, is used as input to the security token calculation: 
     In this case a security token may be valid in more than one cell if the same Cell ID is used both in the registered PLMN and in one of its equivalent PLMNs or in two of the equivalent PLMNs. 
     An object of embodiments herein may therefore be to improve security of RRC resuming in a wireless communications network. 
     According to some example embodiments herein, to ensure that the security token only can be used within specific target cell a globally unique cell identifier is included in the token calculation. For example, one way to construct such a cell identifier is to combine the PLMN ID with the Cell ID, i.e. use the so-called Cell Global Identity (CGI). Other methods to construct such identifiers also exist for example by taking the hash of broadcasted system information or parts thereof. 
     It should be noted that although this disclosure mainly refers to RRC connection resume in NR, a similar problem may also occur for RRC connection resume in eLTE and LTE. The embodiments and examples described herein may be adapted to address the problem also in these other types of network. 
     The embodiments herein are also applicable in an inter-RAT context, i.e. the UE is suspended in one Radio Access technology, RAT and resumes connection in another RAT. 
     To ensure that the security token in RRC resume can only be used in the intended cell, i.e. the cell in which the legitimate UE attempts to resume a connection and for which the security token was originally generated), the security token is bound to the target cell by including a globally unique cell identifier for the target cell in the security token calculation. 
     An advantage of embodiments herein is that the inclusion of a globally unique cell identifier in the security token calculation ensures that the security token can only be used to resume a connection within the intended cell. If an attacker intercepts the security token bound to one cell and attempts to use it in a RRC resume request in some other cell, the request will be rejected since the globally unique cell identifier of the intercepted security token does not match that of the intended other target cell. 
     Other benefits of the solution may include: 
     Embodiments herein do not introduce any additional radio signaling, commonly referred to as overhead, since the inclusion of additional input to the security token calculation does not require any increase of the token size or additional messages over radio. 
     Thanks to the globally unique cell identifier, embodiments herein prevent remote attacks, e.g. denial of service attacks, where an attacker is trying to disturb a user located somewhere else in the system. 
     Embodiments herein also avoid the need to coordinate Cell IDs among operators. Each operator can plan their own Cell IDs even in networks with shared cells where Cell ID collisions may occur. For example, there is no need to maintain a common data base for all cells, and no need to share internal cell planning strategies with competing operator, 
     Embodiments herein relate to wireless communications networks in general.  FIG. 4  is a schematic overview depicting a wireless communications network  100 . The wireless communications network  100  comprises one or more RANs and one or more CNs. The wireless communications network  100  may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, 5G, New Radio (NR), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments herein relate to recent technology trends that are of particular interest in a 5G context, however, embodiments are also applicable in further development of the existing wireless communication systems such as e.g. WCDMA and LTE. 
     In the wireless communications network  100 , UEs such as a UE  120  operate. The UE  120  may be a mobile station, a non-access point (non-AP) STA, a STA, a wireless terminal, which is capable to communicate via one or more Access Networks (AN), e.g. RAN, to one or more core networks (CN). It should be understood by the skilled in the art that “wireless device” is a non-limiting term which could denote any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station communicating within a cell. Although the term UE is used when describing the examples and embodiments herein, the term wireless device could also be used as a synonym for UE. 
     The wireless communications network  100  comprises one or more radio network nodes such as a network node  111  and a network node  112 , herein also referred to as a source network node  111  and a target network node  112 , respectively, where each radio network node  111 ,  112  may provide radio communication in multiple Public Land Mobile Networks, PLMNs, and where each radio network node also provide radio coverage over a respective geographical area referred to as one or more cells  11 ,  12 , which may also be referred to as a beam or a beam group of a first radio access technology (RAT), such as 5G, LTE, Wi-Fi or similar. Each of the source network node  111  and the target network node  112  may be any of a NG-RAN node, a transmission and reception point e.g. a base station, a radio access network node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g, a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a gNB, a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of communicating with a wireless device within the service area served by the source network node  111  and a target network node  112  depending e.g. on the first radio access technology and terminology used. 
     Methods herein may be performed by the UE  120  and the source network node  111 , As an alternative, any Distributed Node (DN) and functionality, e.g. comprised in a cloud  140  as shown in  FIG. 4 , may be used for performing or partly performing the methods. The network aspects of embodiments herein may be deployed in a cloud environment. 
       FIG. 5  shows an example method performed by the UE  120  for resuming an RRC connection to a target cell in the wireless communications network  100 . In this method, the UE performs the actions below. 
     In Action  501 , when the target cell has been found such as identified, the UE  120  generates a security token, wherein an input value in a security token generating function comprises a set of input parameters. The set of input parameters comprises at least a cell identifier, e.g. a cell ID, preferably associated to the PLMN, of the target cell and an indication of a PLMN of the target cell. In this action, the target cell may e.g. be the same cell as a source cell in which the UE had a previous connection. Further, the cell identifier of the target cell may be a cell ID associated to the PLMN of the target cell. 
     In Action  502 , the UE  120  sends a resuming request to a target network node  112  serving the target cell, which resuming request comprises the security token. 
     In some embodiments, the target network node  112  may then send the security token to the source network node  111  for verification, see the description of  FIG. 6  below. 
     The above actions  501  and  502  may be implemented in the UE  120  by means of a computer program comprising instructions, which when executed by a processor, causes the processor to perform actions  501  and  502 . This computer program may be comprised in a suitable carrier. 
     Some further example embodiments that may be employed by the UE  120  in the method of  FIG. 5  will now be described. 
     In some example embodiments, any of the cell identifier, and the indication of the PLMN of the target cell, which were mentioned above as possible input parameters in action  501 , may be represented by any one or more out of the following: 
     a PLMN Identity, ID, 
     a Cell Identity, ID, 
     a hash and/or checksum of broadcasted system information or parts thereof comprising the PLMN and Cell ID information, 
     multiple PLMN IDs wherein the Cell identity comprises multiple Cell IDs, 
     a Tracking Area Code, TAC, associated to the PLMN, and 
     a RAN Area Code, RANAC, associated to the PLMN. 
     In some further example embodiments, the Cell ID and the PLMN ID may be associated with a primary PLMN which is the PLMN occurring first in a broadcasted PLMN list, or with a selected PLMN which is the UE&#39;s registered PLMN. 
     In some further example embodiments, the set of input parameters used in action  401  may further comprise: 
     a Tracking Area Code, TAC, associated to the PLMN, or 
     a RAN Area Code, RANAC, associated to the PLMN. 
       FIG. 6  shows an example method performed by the source network node  111  for resuming an RRC connection to a target cell in the wireless communications network  100 . In this method, the source network node  111  performs the actions below. 
     In Action  601 , the source network node  111  receives the security token from the target network node  112  serving the target cell. This action corresponds to the above action  502  where the UE  120  sends a resuming request comprising the security token to the source network node  111 . 
     In Action  602 , the source network node  111  generates a security token, wherein an input value in the security token generating function comprises a set of input parameters. The set of input parameters comprises at least a cell identifier of the target cell and an indication of a PLMN of the target cell. 
     In Action  603 , if the received security token is successfully verified when compared with the generated security token, the source network node  111  provides to the target network node  112 , a UE context related to the RRC connection of the UE  120 . This is to enable the target network node  112  to resume the RRC connection. 
     The above actions  601 - 603  may be implemented in the source network node  111  by means of a computer program comprising instructions, which when executed by a processor, causes the processor to perform actions  601 - 603 . This computer program may be comprised in a suitable carrier. 
     Some further example embodiments that may be employed by the source network node  111  in the method of  FIG. 6  will now be described. 
     In some example embodiments, any of the cell identifier, and the indication of the PLMN of the target cell, which were mentioned above as possible input parameters in action  602 , may be represented by any one or more out of the following: 
     a PLMN Identity, ID, 
     a Cell Identity, ID, 
     a hash and/or checksum of broadcasted system information or parts thereof comprising the PLMN and Cell ID information, 
     multiple PLMN IDs wherein the Cell identity comprises multiple Cell IDs, 
     a Tracking Area Code, TAC, associated to the PLMN, and 
     a RAN Area Code, RANAC, associated to the PLMN. 
     In some further example embodiments, the Cell ID and the PLMN ID may be associated with a primary PLMN which is the PLMN occurring first in a broadcasted PLMN list, or with a selected PLMN which is the UE&#39;s registered PLMN. 
     In some further example embodiments, the set of input parameters used in action  502  may further comprise: 
     a Tracking Area Code, TAC, associated to the PLMN, or 
     a RAN Area Code, RANAC, associated to the PLMN. 
     Some embodiments and examples of using a globally unique cell identifier based on combination of Cell ID and PLMN ID, will now be described. 
     To bind the security token to the target cell a globally unique cell identifier may be included in the security token calculation. As the PLMN ID uniquely identifies a PLMN and the Cell ID uniquely identifies a cell within a PLMN, a globally unique cell identifier may be formed by combining the PLMN ID and Cell ID. The PLMN ID does not need to be the PLMN the UE  120  is connecting to or has been connected to, but preferably it may be associated with the Cell ID used in the security token calculation. 
     As described above, a cell may be shared by multiple PLMNs and it has also been described that a UE may use either the Cell ID associated with the primary PLMN or the Cell ID associated with the selected PLMN to generate the security token. Regardless of which one of the above alternatives is used, the UE  120  may use the PLMN ID associated with the Cell ID to construct the above-mentioned cell global identity CGI. This could be done according to either of the following alternatives:
         If the primary PLMN is used the cell global identity is formed or calculated from the primary PLMN&#39;s PLMN ID and Cell ID.   If the selected PLMN is used the cell global identity is formed or calculated from the selected PLMN&#39;s PLMN ID and Cell ID.       

     In both alternatives the combined cell identifier or cell global identity is guaranteed to be globally unique and therefore achieves the intended purpose of creating a security token that is bound to the cell of the chosen PLMN. 
     Below is an example of how the embodiments above may be captured in the RRC specification (additions are marked as  underlined ). It is noted that the security token is denoted as resumeMAC-I in the specification and the input parameters to the security token calculation are comprised in an UE variable called VarResumeMAC-Input. At present the RRC specification is still not fully finished and therefore some of the parameter names may be changed in the RRC specification. The example below provides for both alternatives of using the primary PLMN and using the selected PLMN, as described above, although in the actual specification only one of these alternatives is likely to be included. Variations of the example below are also possible; for example, the target PLMN ID and Cell ID fields may be combined into a single field called targetCellGloballIdentity or similar. 
     UE Variables 
     VarResumeMAC-Input 
     The UE variable VarResumeMAC-Input specifies the input used to generate the resumeMAC-I during RRC Connection Resume procedure. 
     
       
         
           
               
             
               
                   
               
               
                 VarResumeMAC-Inputvariable 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 -- ASN1START 
               
               
                 -- TAG-VAR-RESUMEMACINPUT-START 
               
               
                 VarResumeMAC-Input ::=     SEQUENCE { 
               
            
           
           
               
               
            
               
                     sourcePhysCellId 
                 PhysCellId, 
               
               
                     targetPLMN-Identity 
                 PLMN-Identity, 
               
               
                      targetCellIdentity   
                 
                   CellIdentity, 
                 
               
               
                     source-c-RNTI 
                 RNTI-Value 
               
               
                 } 
               
               
                 -- TAG-VAR-RESUMEMACINPUT-STOP 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     VarResumeMAC-Input Field Descriptions 
     TargetPLMN-Identity 
     
       Alternative 1: Set to PLMN identity of the primary PLMN i.e. the first PLMN in the PLMN lists in cell access related info in the target cell. 
     
     
       Alternative 2: Set to PLMN identity of the selected PLMN i.e. the PLMN which the UE is connecting to in the target cell. 
     
     TargetCellIdentity 
     Set to CellIdentity of the target cell i.e. the cell the UE is trying to resume. 
     Source-C-RNTI 
     Set to C-RNTI that the UE had in the PCell it was connected to prior to suspension of the RRC connection. 
     SourcePhysCellId 
     Set to the physical cell identity of the PCell the UE was connected to prior to suspension of the RRC connection. 
     Editor&#39;s Note: EFS Additional input to VarResumeMAC-Input (replay attacks mitigation). 
     In another embodiment, the UE  120  may include a hash and/or checksum of the broadcasted system information or parts thereof, e.g. only SIB1, in the security token calculation. As the system information, e.g. SIB1, includes the PLMN and Cell ID information the hash/checksum can also serve as a cell global identifier. In this embodiment, in order for the source network node  111  such as the source gNB to be able to verify the security token when received, the target network node  112  such as the target gNB may need to include the target cell system information, or its hash, together with the security token in an Xn retrieve UE context request sent to the source gNB. 
     In yet another embodiment, the UE  120  may include multiple PLMN IDs and/or Cell IDs in the security token calculation. In another example, all PLMN and/or Cell IDs could be included in the security token calculation. Using multiple PLMN IDs and/or Cell IDs in the security token calculation could ensure that the input parameters are unique, e.g. bound to the target cell, even in scenarios when the operator reuses Cell IDs outside the shared area. One example scenario where this could be useful is when the shared network is planned by a different legal/corporate entity, which still uses the main PLMN IDs of the operator sharing their network. 
     Some alternative embodiments of calculating a security token using other inputs instead or in addition to PLMN ID, will now be described. 
     Although the usage of the PLMN ID as input parameter for generating the security token has been mostly described, there may be embodiments applying a similar principle but including in the calculation of the security token other parameters, e.g., included in cell access related information in SIB1. That can be employed either in addition to the PLMN ID as described, or instead of using the PLMN ID. The parameters below may contribute to make the input to the security calculation unique in order to either provide a complement or an alternative to using the PLMN ID. 
     For reference, an excerpt from the RRC specification, see TS 38.331 1 and R2-1813492, CR to 38.331 “Introduction of NR SA”, describing the cell access related info structure in SIB1 for NR, is provided below. 
     Radio Resource Control Information Elements 
     CellAccessRelatedInfo 
     The IE CellAccessRelatedInfo indicates cell access related information for this cell. 
     
       
         
           
               
             
               
                   
               
               
                 CellAccessRelatedInfo information element 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 -- ASN1START 
               
               
                 -- TAG-CELL-ACCESS-RELATED-INFO-START 
               
               
                 CellAccessRelatedInfo  ::= SEQUENCE { 
               
            
           
           
               
               
            
               
                     plmn-IdentityList 
                 PLMN-IdentityInfoList, 
               
               
                     cellReservedForOtherUse 
                 ENUMERATED {true} 
               
               
                   
                 OPTIONAL,-- Need R 
               
               
                     ... 
               
               
                 } 
               
            
           
           
               
            
               
                 -- TAG- CELL-ACCESS-RELATED-INFO-STOP 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     CellAccessRelatedInfo Field Descriptions 
     CellReservedForOtherUse 
     Indicates whether the cell is reserved, as defined in 38.304. The field is applicable to all PLMNs. 
     PLMN-IdentityList 
     The PLMN-IdentityList is used to configure a set of PLMN-IdentityInfo elements. Each of those elements contains a list of one or more PLMN identities and additional information associated with those PLMNs. The total number of PLMNs in the PLMNIdentityInfoList does not exceed 12. The PLMN index is defined as b1+b2+ . . . +b(n−1)+i If this PLMN is included at the n-th entry of PLMN-IdentityInfoList and the i-th entry of its corresponding PLMN-IdentityInfo, where b(j) is the number of PLMN-Identity entries in each PLMN-IdentityInfo respectively. 
     PLMN-IdentityInfoList 
     Includes a list of PLMN identity information. 
     
       
         
           
               
             
               
                   
               
               
                 PLMN-IdentityInfoList information element 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 -- ASN1START 
               
               
                 -- TAG-PLMN-IDENTITY-LIST-START 
               
               
                 PLMN-IdentityInfoList ::= SEQUENCE (SIZE (1..maxPLMN)) OF PLMN-IdentityInfo 
               
               
                 PLMN-IdentityInfo ::=   SEQUENCE { 
               
            
           
           
               
               
            
               
                 plmn-IdentityList 
                 SEQUENCE (SIZE (1..maxPLMN)) OF PLMN-Identity, 
               
               
                 trackingAreaCode 
                 TrackingAreaCode  OPTIONAL, -- Need R 
               
            
           
           
               
               
            
               
                 ranac 
                 RAN-AreaCode  OPTIONAL,  -- Need R 
               
            
           
           
               
               
            
               
                 cellIdentity 
                 CellIdentity, 
               
               
                 cellReservedForOperatorUse 
                 ENUMERATED {reserved, notReserved}, 
               
               
                 ... 
               
               
                 } 
               
            
           
           
               
            
               
                 -- TAG-PLMN-IDENTITY-LIST-STOP 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     PLMN-IdentityInfo Field Descriptions 
     CellReservedForOperatorUse 
     Indicates whether the cell is reserved for operator use (per PLMN), as defined in 38.304 [20]. 
     TrackingAreaCode 
     Indicates Tracking Area Code to which the cell indicated by cellIdentity field belongs. The presence of the field indicates that the cell supports at least standalone operation; the absence of the field indicates that the cell only supports EN-DC functionality. 
     In some embodiments, the UE  120  may include the Tracking Area Code, TAC, associated to the first PLMN Identity Info element in the list within cell access related info, as input parameter for generating the security token. This has the benefit of preventing attacks outside the tracking area and could be useful if operator for some reason in the future would reuse Cell IDs in other tracking areas. 
     In some other embodiments, the UE  120  may include the RAN Area Code, RANAC, associated to the first PLMN Identity Info element in the list within cell access related info, as input parameter for generating the security token. This has the benefit of preventing attacks outside the RAN area and could be useful if operator for some reason in the future would reuse Cell IDs in other RAN areas. 
     In some other embodiments, the UE  120  may include the Tracking Area Code, TAC, associated to the selected PLMN Identity Info entry in the list within cell access related info, as input parameter for generating the security token. This has the benefit of preventing attacks outside the tracking area and could be useful if operator for some reason in the future would reuse Cell IDs in other tracking areas. 
     In some other embodiments, the UE  120  may include the RAN Area Code, RANAC, associated to the selected PLMN Identity Info entry in the list within cell access related info, as input parameter for generating the security token. This has the benefit of preventing attacks outside the RAN area and could be useful if operator for some reason in the future would reuse Cell IDs in other RAN areas. 
     Some further embodiments that may be used for error handling when resuming an RRC connection of a UE  120  to a target cell, will now be described. 
     In further embodiments, upon detecting that there might be some ambiguity in which Cell ID is used for the context verification, the UE may perform different actions. 
     In some embodiments, before starting the resume procedure, when the UE acquires system information in the target cell, e.g. cell access related information in SIB1, and detecting that there are multiple Cell IDs being broadcasted, e.g. associated to multiple PLMNs, the UE inform upper layers of a failure to resume and that NAS recovery is triggered. In other words, the UE enters RRC_IDLE from RRC_INACTIVE and instead of initiating an RRC connection resume procedure, it initiated and RRC connection setup procedure. On the network side, the UE context can be refreshed by the absence of periodic RAN area updates. Alternatively, the RRC setup complete could include some additional information concerning the failure so that network could use it to refresh or “clean up” the UE context. A possible limitation of the above approach is that the resume procedure may not be supported in a RAN sharing scenario, but it would simplify RRC specifications. 
     In another embodiment, before starting a resume procedure, when the UE acquires system information in the target cell, e.g. cell access related information in SIB1, and detects that there are multiple Cell IDs being broadcasted, e.g. associated to multiple PLMNs, upon identifying that the UE needs to select an equivalent PLMN, i.e. change of PLMN compared to the one in the UE context known at the network, the UE informs upper layers about a failure to resume and that NAS recovery is triggered. In other words, the UE enters RRC_IDLE from RRC_INACTIVE and instead of initiating an RRC connection resume procedure, the UE initiated an RRC connection setup procedure. A possible limitation of the latter approach is that the resume procedure is supported in a RAN sharing scenario as long as the registered PLMN is being broadcasted in the target cell. 
     In another embodiment, before starting a resume procedure, when the UE acquires system information in the target cell, e.g. cell access related information in SIB1, and detects that there are multiple Cell IDs being broadcasted, e.g. associated to multiple PLMNs, upon identifying that the UE needs to select an equivalent PLMN, i.e. change of PLMN compared to the one in the UE context known at the network, the UE indicates that occurrence to the network via a 1 bit flag, e.g. using RACH preambles. Thereby, the network can possibly provide a larger grant for the RRC resume request message or alternatively directly performs a fallback procedure i.e. wait for an RRC resume request and respond with an RRC setup so that the UE comes back via RRC_IDLE after informing upper layers about the fallback. 
     In yet another embodiment, before starting a resume procedure, when the UE acquires system information in the target cell, e.g. cell access related information in SIB1, and detects that there are multiple Cell IDs being broadcasted, e.g. associated to multiple PLMNs, upon identifying that the UE needs to select an equivalent PLMN, i.e. change of PLMN compared to the one in the UE context known at the network, the UE indicates that occurrence to the network via a flag in the RRC resume request. Thereby, the network can directly respond with an RRC setup, or, if the serving gNB and target gNB are the same node, the RRC resume could anyway be provided as there would be no need for verification for the purpose of context fetching. 
       FIGS. 7 a  and 7 b    show examples of arrangements in the UE  120 . 
     With reference to  FIG. 7 a   , the UE  120  may comprise an input and output interface configured to communicate with each other. The input and output interface may comprise a wireless receiver (not shown) and a wireless transmitter (not shown). 
     With reference to  FIG. 7 b   , the UE  120  may comprise a generating unit  120 A and a sending unit  120 B configured to perform the method actions of  FIG. 5  as described herein. 
     In more detail, and with further reference to  FIG. 4 , the UE  120  of  FIGS. 7 a  and 7 b    is configured for resuming an RRC connection to a target cell in a wireless communications network  100 . 
     When the target cell is found, the UE  120  is configured to generate a security token, wherein an input value in a security token generating function is adapted to comprise a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier of the target cell and an indication of a PLMN of the target cell. This operation may be performed by the generating unit  120 A, as also illustrated in action  501 . 
     The UE  120  is further configured to send a resuming request to a target network node  112  serving the target cell, which resuming request is adapted to comprise the security token. This operation may be performed by the sending unit  120 B, as also illustrated in action  402 . 
     The embodiments herein may be implemented through a respective processor or one or more processors, such as the processor of a processing circuitry in the UE  120  depicted in  FIG. 7 a   , together with respective computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the UE  120 . One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the UE  120 . 
     The UE  120  may further comprise a memory comprising one or more memory units. The memory comprises instructions executable by the processor in the UE  120 . The memory is arranged to be used to store instructions, data, security token, parameters, configurations, and applications to perform the methods herein when being executed in the UE  120 . 
     In some embodiments, are computer program comprises instructions, which when executed by the at least one processor, cause the at least one processor of the UE  120  to perform the actions above. As indicated above, the processor(s) of the UE  120  could also be denoted a processing circuitry. 
     In some embodiments, a respective carrier comprises the respective computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. 
     Those skilled in the art will also appreciate that the functional units in the UE  120 , described below may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the UE  120 , that when executed by the respective one or more processors such as the processors described above cause the respective at least one processor to perform actions according to any of the actions above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC). 
       FIGS. 8 a  and 8 b    show examples of arrangements in the source network node  111 , 
     With reference to  FIG. 8 a   , the source network node  111  may comprise an input and output interface configured to communicate with each other. The input and output interface may comprise a wireless receiver (not shown) and a wireless transmitter (not shown). 
     With reference to  FIG. 8 b   , the source network node  111  may comprise a receiving unit  111 A, a generating unit  111 B, and a providing unit  111 C, configured to perform the method actions of  FIG. 6  as described herein. 
     In more detail, and with further reference to  FIG. 4 , the source network node  111  is configured for resuming an RRC connection to a target cell in a wireless communications network  100 . 
     The source network node  111  is configured to receive from a target network node  112  serving the target cell, a security token. This operation may be performed by the receiving unit  111 A, as also illustrated in action  601 . 
     The source network node  111  is also configured to generate a security token, wherein an input value in a security token generating function is adapted to comprise a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier of the target cell and an indication of a PLMN of the target cell. This operation may be performed by the generating unit  111 B, as also illustrated in action  602 . 
     If the received security token is successfully verified when compared with the generated security token, the source network node  111  is configured to provide to the target network node  112  a UE context related to the RRC connection of the UE  120 , to enable the target network node  112  to resume the RRC connection. This operation may be performed by the providing unit  111 C, as also illustrated in action  603 . 
     The embodiments herein may be implemented through a respective processor or one or more processors, such as the processor of a processing circuitry in the source network node  111  depicted in  FIG. 8 a   , together with respective computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the source network node  111 . One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the source network node  111 . 
     The source network node  111  may further comprise respective a memory comprising one or more memory units. The memory comprises instructions executable by the processor in the UE  120 . The memory is arranged to be used to store instructions, data, security token, parameters, configurations, and applications to perform the methods herein when being executed in the source network node  111 . 
     In some embodiments, are computer program comprises instructions, which when executed by the at least one processor, cause the at least one processor of the UE  120  to perform the actions above. As indicated above, the processor(s) of the source network node  111  could also be denoted a processing circuitry. 
     In some embodiments, a respective carrier comprises the respective computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. 
     Those skilled in the art will also appreciate that the functional units in the source network node  111 , described below may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the source network node  111 , that when executed by the respective one or more processors such as the processors described above cause the respective at least one processor to perform actions according to any of the actions above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC). 
     Throughout this description, when using the word “comprise” or “comprising” it shall be interpreted as non-limiting, i.e. meaning “consist at least of”. 
     The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used. 
     Below, some numbered example embodiments 1-20 are shortly described. See e.g.  FIGS. 4, 5, 6, 7   a  and b,and  8   a  and  b.    
     Embodiment 1. A method performed by a User Equipment, UE,  120  e.g. for resuming an Radio Resource Control, RRC, connection to a target cell in a wireless communications network  100 , the method comprising: 
     when the target cell has been found such as identified, the target cell and source cell may e.g. be the same, generating  501  a security token, wherein an input value in the security token generating function comprises a set of input parameters, which set of input parameters comprises at least a cell identifier, (e.g. a cell ID, preferably associated to the PLMN), of the target cell and an indication of a Public Land Mobile Network PLMN of the target cell. 
     sending  502  a resuming request to a target network node  112  serving the target cell, which resuming request comprises the security token. 
     Embodiment 2. The method according to embodiment 1, wherein any of the cell identifier, and the indication of the PLMN of the target cell is represented by any one or more out of: 
     PLMN Identity, ID, e.g. the PLMN ID of the first PLMN or the selected PLMN, 
     a cell ID, 
     a hash and/or checksum of broadcasted system information or parts thereof, e.g. SIB1, comprising the PLMN and Cell ID information, 
     multiple PLMN IDs and/or and wherein the cell identity comprises multiple Cell IDs 
     Tracking Area Code TAC associated to the PLMN, e.g. the first PLMN or the selected PLMN, 
     the RAN Area Code RANAC associated to the PLMN, e.g. the first PLMN or the selected PLMN. 
     Embodiment 3. The method according to any of the embodiments 1-2, wherein the set of input parameters further comprises: 
     a Tracking Area Code TAC associated to the PLMN, e.g. the first PLMN or the selected PLMN, 
     a RAN Area Code RANAC associated to the PLMN, e.g. the first PLMN or the selected PLMN 
     Embodiment 4. A computer program comprising instructions, which when executed by a processor, causes the processor to perform actions according to any of the embodiments 1-3. 
     Embodiment 5. A carrier comprising the computer program of embodiment 4, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. 
     Embodiment 6. A method performed by a source network node  111  e.g. for resuming a Radio Resource Control, RRC, connection of a UE  120  to a target cell in a wireless communications network  100 , the method comprising: 
     receiving  601  from a target network node  112  serving the target cell, a security token, 
     generating  602  a security token, wherein an input value in the security token generating function comprises a set of input parameters, which input parameters comprises at least a cell identifier, e.g. a cell ID, of the target cell and an indication of a PLMN of the target cell, 
     if the received security token is successfully verified when compared with the generated security token, providing  603  to the target network node  112  a UE context related to the RRC connection of the UE  120 , to enable the target network node  112  to resume the RRC connection. 
     Embodiment 7. The method according to embodiment 6, wherein any of the cell identifier, and the indication of the PLMN of the target cell is represented by any one or more out of: 
     PLMN Identity, ID, e.g. the PLMN ID of the first PLMN or the selected PLMN, 
     a cell ID, 
     a hash and/or checksum of broadcasted system information or parts thereof, e.g. SIB1, comprising the PLMN and Cell ID information, 
     multiple PLMN IDs and/or and wherein the cell identity comprises multiple Cell IDs 
     Tracking Area Code TAC associated to the PLMN, e.g, the first PLMN or the selected PLMN, 
     the RAN Area Code RANAC associated to the PLMN, e.g, the first PLMN or the selected PLMN. 
     Embodiment 8. The method according to any of the embodiments 6-7, wherein the set of input parameters further comprises: 
     a Tracking Area Code TAC associated to the PLMN, e.g. the first PLMN or the selected PLMN, 
     a RAN Area Code RANAC associated to the PLMN, e.g. the first PLMN or the selected PLMN 
     Embodiment 9. A computer program comprising instructions, which when executed by a processor, causes the processor to perform actions according to any of the embodiments 6-8. 
     Embodiment 10. A carrier comprising the computer program of embodiment 9, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. 
     Embodiment 11. A method performed by a User Equipment, UE,  120  e.g. for any one out of re-establishing and resuming, a Radio Resource Control, RRC, connection to a target cell in a wireless communications network  100 , the method comprising: 
     when the target cell has been found such as identified, the target cell and source cell may e.g. be the same, generating  501  a security token, wherein an input value in the security token generating function comprises a set of input parameters, which set of input parameters comprises at least a cell identifier, e.g. a cell ID, preferably associated to the PLMN, of the target cell and an indication of a Public Land Mobile Network PLMN of the target cell, 
     sending  502  any one out of a re-establishment and resuming, request to a target network node  112  serving the target cell, which one out of a re-establishment and resuming, request comprises the security token. 
     Embodiment 12. A method performed by a source network node  111  e.g, for any one out of re-establishing and resuming a Radio Resource Control, RRC, connection of a UE  120  to a target cell in a wireless communications network  100 , the method comprising: 
     receiving  601  from a target network node  112  serving the target cell, a security token, 
     generating  602  a security token, wherein an input value in the security token generating function comprises a set of input parameters, which input parameters comprises at least a cell identifier, e.g. a cell ID, of the target cell and an indication of a PLMN of the target cell, 
     if the received security token is successfully verified when compared with the generated security token, providing  503  to the target network node  112  a UE context related to the RRC connection of the UE  120 , to enable the target network node  112  to any one out of re-establish and resume the RRC connection. 
     Embodiment 13. A User Equipment, UE,  120  configured e.g. for resuming a Radio Resource Control, RRC, connection to a target cell in a wireless communications network  100 , the UE  120  being configured to: 
     when the target cell has been found such as identified, the target cell and source cell may e.g. be the same, generate a security token, wherein an input value in the security token generating function comprises a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier, e.g. a cell ID, preferably associated to the PLMN, of the target cell and an indication of a Public Land Mobile Network PLMN of the target cell, e.g. by means of a generating unit in the UE  120 , 
     send a resuming request to a target network node  112  serving the target cell, which resuming request is adapted to comprise the security token, e.g, by means of a sending unit in the UE  120 . 
     Embodiment 14. The UE according to embodiment 13, wherein any of the cell identifier, and the indication of the PLMN of the target cell is adapted to be represented by any one or more out of: 
     a PLMN Identity, ID, e.g. the PLMN ID of the first PLMN or the selected PLMN, 
     a cell ID, 
     a hash and/or checksum of broadcasted system information or parts thereof, e.g. SIB1, comprising the PLMN and Cell ID information, 
     multiple PLMN IDs and/or and wherein the cell identity comprises multiple Cell IDs 
     a Tracking Area Code TAC associated to the PLMN, e.g. the first PLMN or the selected PLMN, and 
     a RAN Area Code RANAC associated to the PLMN, e.g. the first PLMN or the selected PLMN. 
     Embodiment 15. The UE according to any of the embodiments 13-14, wherein the set of input parameters are adapted to further comprise: 
     a Tracking Area Code TAC associated to the PLMN, e.g. the first PLMN or the selected PLMN, 
     a RAN Area Code RANAC associated to the PLMN, e.g. the first PLMN or the selected PLMN 
     Embodiment 16. A source network node  111  configured e.g. for resuming a Radio Resource Control, RRC, connection of a UE  120  to a target cell in a wireless communications network  100 , the source network node  111  being configured to: 
     receive from a target network node  112  serving the target cell, a security token, e.g. by means of a receiving unit in the source network node  111 , 
     generate a security token, wherein an input value in the security token generating function is adapted to comprise a set of input parameters, which input parameters are adapted to comprise at least a cell identifier, e.g. a cell ID, of the target cell and an indication of a PLMN of the target cell, e.g. by means of a generating unit in the source network node  111 , 
     if the received security token is successfully verified when compared with the generated security token, provide to the target network node  112  a UE context related to the RRC connection of the UE  120 , to enable the target network node  112  to resume the RRC connection, e.g. by means of a providing unit in the source network node  111 . 
     Embodiment 17. The source network node  111  according to embodiment 16, wherein any of the cell identifier, and the indication of the PLMN of the target cell is adapted to be represented by any one or more out of: 
     a PLMN Identity, ID, e.g. the PLMN ID of the first PLMN or the selected PLMN, 
     a cell ID, 
     a hash and/or checksum of broadcasted system information or parts thereof, e.g. SIB1, comprising the PLMN and Cell ID information, 
     multiple PLMN IDs and/or and wherein the cell identity comprises multiple Cell IDs 
     a Tracking Area Code TAC associated to the PLMN, e.g. the first PLMN or the selected PLMN, and 
     a RAN Area Code RANAC associated to the PLMN, e.g. the first PLMN or the selected PLMN. 
     Embodiment 18. The method according to any of the embodiments 16-17, wherein the set of input parameters are adapted to further comprise: 
     a Tracking Area Code TAC associated to the PLMN, e.g. the first PLMN or the selected PLMN, 
     a RAN Area Code RANAC associated to the PLMN, e.g. the first PLMN or the selected PLMN. 
     Embodiment 19. A User Equipment, UE,  120  configured e.g. for any one out of re-establishing and resuming a Radio Resource Control, RRC, connection to a target cell in a wireless communications network  100 , the UE  120  being configured to: 
     when the target cell has been found such as identified, the target cell and source cell may e.g. be the same, generate a security token, wherein an input value in the security token generating function is adapted to comprise a set of input parameters, which set of input parameters are adapted to comprise at least a cell identifier, e.g. a cell ID, preferably associated to the PLMN, of the target cell and an indication of a Public Land Mobile Network PLMN of the target cell, e.g. by means of a generating unit in the UE  120 , 
     send any one out of a re-establishment and resuming request to a target network node  112  serving the target cell, which any one out of a re-establishment and resuming request is adapted to comprise the security token, e.g. by means of a sending unit in the UE  120 . 
     Embodiment 20. A source network node  111  configured e.g. for any one out of re-establishing and resuming a Radio Resource Control, RRC, connection of a UE  120  to a target cell in a wireless communications network  100 , the source network node  111  being configured to: 
     receive from a target network node  112  serving the target cell, a security token, e.g. by means of a receiving unit in the source network node  111 , 
     generate a security token, wherein an input value in the security token generating function is adapted to comprise a set of input parameters, which input parameters are adapted to comprise at least a cell identifier, e.g. a cell ID, of the target cell and an indication of a PLMN of the target cell, e.g. by means of a generating unit in the source network node  111 , 
     if the received security token is successfully verified when compared with the generated security token, provide to the target network node  112  a UE context related to the RRC connection of the UE  120 , to enable the target network node  112  to any one out of re-establish and resume the RRC connection, e.g. by means of a providing unit in the source network node  111 . 
     Some further extensions and variations where the above-described embodiments and examples could be employed, will now be described. 
     With reference to  FIG. 9 , in accordance with an embodiment, a communication system includes a telecommunication network  3210  such as the wireless communications network  100 , e.g. an IoT network, or a WLAN, 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 the network node  110 ,  130 , access nodes, AP STAs 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) e.g. the UE  120  such as a Non-AP STA  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  e.g. the wireless device  122  such as a Non-AP STA 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 sub-networks (not shown). 
     The communication system of  FIG. 9  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 signaling 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. 10 . 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) 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. 10 ) 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 non-human 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. 10  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. 9 , respectively. This is to say, the inner workings of these entities may be as shown in  FIG. 10  and independently, the surrounding network topology may be that of  FIG. 9 , 
     In  FIG. 10 , 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., on the basis of 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 applicable RAN effect; data rate, latency, power consumption, and thereby provide benefits such as corresponding effect on the OTT service: e.g. reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime. 
     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 signaling 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. 11  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 such as the network node  110 , and a UE such as the UE  120 , which may be those described with reference to  FIG. 9  and  FIG. 10 . For simplicity of the present disclosure, only drawing references to  FIG. 11  will be included in this section. In a first action  3410  of the method, the host computer provides user data. In an optional subaction  3411  of the first action  3410 , the host computer provides the user data by executing a host application. In a second action  3420 , the host computer initiates a transmission carrying the user data to the UE. In an optional third action  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 action  3440 , the UE executes a client application associated with the host application executed by the host computer. 
       FIG. 12  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 such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to  FIG. 9  and  FIG. 10 . For simplicity of the present disclosure, only drawing references to  FIG. 12  will be included in this section. In a first action  3510  of the method, the host computer provides user data. In an optional subaction (not shown) the host computer provides the user data by executing a host application. In a second action  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 action  3530 , the UE receives the user data carried in the transmission. 
       FIG. 13  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 such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to  FIG. 9  and  FIG. 10 . For simplicity of the present disclosure, only drawing references to  FIG. 13  will be included in this section. In an optional first action  3610  of the method, the UE receives input data provided by the host computer. Additionally or alternatively, in an optional second action  3620 , the UE provides user data. In an optional subaction  3621  of the second action  3620 , the UE provides the user data by executing a client application. In a further optional subaction  3611  of the first action  3610 , the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third subaction  3630 , transmission of the user data to the host computer. In a fourth action  3640  of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure. 
       FIG. 14  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 such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to  FIG. 9  and  FIG. 10 . For simplicity of the present disclosure, only drawing references to  FIG. 14  will be included in this section. In an optional first action  3710  of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second action  3720 , the base station initiates transmission of the received user data to the host computer. In a third action  3730 , the host computer receives the user data carried in the transmission initiated by the base station. 
     Some further numbered example embodiments A1-A8 and B1-B8 of the solution will now be outlined as further suggestions of how apparatuses may be configured to implement the above-described UE and source network node, respectively.
     Embodiment A1 A User Equipment, UE, ( 120 ) configured for resuming a Radio Resource Control, RRC, connection to a target cell in a wireless communications network ( 100 ), the UE ( 120 ) comprising processing circuitry configured to:   

     when the target cell is found, generate a security token, wherein an input value in a security token generating function comprises a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier of the target cell and an indication of a Public Land Mobile Network, PLMN, of the target cell, and 
     send a resuming request to a target network node ( 112 ) serving the target cell, which resuming request is adapted to comprise the security token.
     Embodiment A2: The UE ( 120 ) according to embodiment A1, wherein any of the cell identifier and the indication of the PLMN of the target cell is adapted to be represented by any one or more out of:   

     a PLMN Identity, ID, 
     a Cell Identity, ID, 
     a hash and/or checksum of broadcasted system information or parts thereof comprising the PLMN and Cell ID information, 
     multiple PLMN IDs wherein the Cell identity comprises multiple Cell IDs, 
     a Tracking Area Code, TAC, associated to the PLMN, and 
     a RAN Area Code, RANAC, associated to the PLMN.
     Embodiment A3: The UE ( 120 ) according to embodiment A2, wherein the Cell ID and the PLMN ID are associated with a primary PLMN which is the PLMN occurring first in a broadcasted PLMN list, or with a selected PLMN which is the UE&#39;s registered PLMN.   Embodiment A4: The UE ( 120 ) according to any of the embodiments A1-A3, wherein the set of input parameters is adapted to further comprise:   

     a Tracking Area Code, TAC, associated to the PLMN, or 
     a RAN Area Code, RANAC, associated to the PLMN.
     Embodiment A5: A source network node ( 111 ) configured for resuming a Radio Resource Control, RRC, connection of a User Equipment, UE, ( 120 ) to a target cell in a wireless communications network ( 100 ), the source network node ( 111 ) comprising processing circuitry configured to:   

     receive from a target network node ( 112 ) serving the target cell, a security token, 
     generate a security token, wherein an input value in a security token generating function is adapted to comprise a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier of the target cell and an indication of a Public Land Mobile Network, PLMN, of the target cell, and 
     if the received security token is successfully verified when compared with the generated security token, provide to the target network node ( 112 ) a UE context related to the RRC connection of the UE ( 120 ), to enable the target network node ( 112 ) to resume the RRC connection.
     Embodiment A6: The source network node ( 111 ) according to embodiment A5, wherein any of the cell identifier and the indication of the PLMN of the target cell is adapted to be represented by any one or more out of:   

     a PLMN Identity, ID, 
     a Cell Identity, ID, 
     a hash and/or checksum of broadcasted system information or parts thereof comprising the PLMN and Cell ID information, 
     multiple PLMN IDs wherein the Cell identity comprises multiple Cell IDs, 
     a Tracking Area Code, TAC, associated to the PLMN, and 
     a RAN Area Code, RANAC, associated to the PLMN.
     Embodiment A7: The source network node ( 111 ) according to embodiment A6, wherein the Cell ID and the PLMN ID are associated with a primary PLMN which is the PLMN occurring first in a broadcasted PLMN list, or with a selected PLMN which is the UE&#39;s registered PLMN.   Embodiment A8: The source network node ( 111 ) according to any of the embodiments A5-A7, wherein the set of input parameters is adapted to further comprise:   

     a Tracking Area Code, TAC, associated to the PLMN, or 
     a RAN Area Code, RANAC, associated to the PLMN.
     Embodiment B1: A User Equipment, UE, ( 120 ) configured for resuming a Radio Resource Control, RRC, connection to a target cell in a wireless communications network ( 100 ), the UE ( 120 ) comprising:   

     a generating unit ( 120 A) configured to, when the target cell is found, generate a security token, wherein an input value in a security token generating function comprises a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier of the target cell and an indication of a Public Land Mobile Network, PLMN, of the target cell, and 
     a sending unit ( 120 B) configured to send a resuming request to a target network node ( 112 ) serving the target cell, which resuming request is adapted to comprise the security token.
     Embodiment B2: The UE ( 120 ) according to embodiment B1, wherein any of the cell identifier and the indication of the PLMN of the target cell is adapted to be represented by any one or more out of:   

     a PLMN Identity, ID, 
     a Cell Identity, ID, 
     a hash and/or checksum of broadcasted system information or parts thereof comprising the PLMN and Cell ID information, 
     multiple PLMN IDs wherein the Cell identity comprises multiple Cell IDs, 
     a Tracking Area Code, TAC, associated to the PLMN, and 
     a RAN Area Code, RANAC, associated to the PLMN.
     Embodiment B3: The UE ( 120 ) according to embodiment B2, wherein the Cell ID and the PLMN ID are associated with a primary PLMN which is the PLMN occurring first in a broadcasted PLMN list, or with a selected PLMN which is the UE&#39;s registered PLMN.   Embodiment B4: The UE ( 120 ) according to any of the embodiments B1-B3, wherein the set of input parameters is adapted to further comprise:   

     a Tracking Area Code, TAC, associated to the PLMN, or 
     a RAN Area Code, RANAC, associated to the PLMN.
     Embodiment B5: A source network node ( 111 ) configured for resuming a Radio Resource Control, RRC, connection of a User Equipment, UE, ( 120 ) to a target cell in a wireless communications network ( 100 ), the source network node ( 111 ) comprising:   

     a receiving unit ( 111 A) configured to receive from a target network node ( 112 ) serving the target cell, a security token, 
     a generating unit ( 111 B) configured to generate a security token, wherein an input value in a security token generating function is adapted to comprise a set of input parameters, which set of input parameters is adapted to comprise at least a cell identifier of the target cell and an indication of a Public Land Mobile Network, PLMN, of the target cell, and 
     a providing unit ( 111 C) configured to, if the received security token is successfully verified when compared with the generated security token, provide to the target network node ( 112 ) a UE context related to the RRC connection of the UE ( 120 ), to enable the target network node ( 112 ) to resume the RRC connection.
     Embodiment B6: The source network node ( 111 ) according to embodiment B5, wherein any of the cell identifier, and the indication of the PLMN of the target cell is adapted to be represented by any one or more out of:   

     a PLMN Identity, ID, 
     a Cell Identity, ID, 
     a hash and/or checksum of broadcasted system information or parts thereof, e.g. SIB1, comprising the PLMN and Cell ID information, 
     multiple PLMN IDs wherein the Cell identity comprises multiple Cell IDs, 
     a Tracking Area Code, TAC, associated to the PLMN, and 
     a RAN Area Code, RANAC, associated to the PLMN.
     Embodiment B7: The source network node ( 111 ) according to embodiment B6, wherein the Cell ID and the PLMN ID are associated with a primary PLMN which is the PLMN occurring first in a broadcasted PLMN list, or with a selected PLMN which is the UE&#39;s registered PLMN.   Embodiment B8: The source network node ( 111 ) according to any of the embodiments B5-B7, wherein the set of input parameters is adapted to further comprise:   

     a Tracking Area Code, TAC, associated to the PLMN, or 
     a RAN Area Code, RANAC, associated to the PLMN.