User Equipment and Method Performed by a User Equipment - Patent application

Abstract

To separate user plane communication and control plane communication.SOLUTION: A first base station receives a first message regarding a security key update from a second base station when a PDCP count is about to wrap around. The first base station uses the first base station's security key to derive the second base station's updated security key while UE is connected to the first base station and the second base station. The first base station transmits to the second base station a message for delivering the updated security key from which an updated user plane security key can be derived to protect user plane traffic between the UE and the second base station.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to mobile communication devices and networks, particularly but not exclusively to mobile communication devices and networks operating in accordance with 3rd Generation Partnership Project (3GPP®) standards or equivalents or derivatives thereof. The present invention is particularly but not exclusively related to the so-called Long Term Evolution (LTE) / Evolved LTE (LTE-Advanced (LTE-A)) further evolution of UTRAN, referred to as Evolved Universal Terrestrial Radio Access Network (E-UTRAN). [Background technology]

[0002] As part of the 3GPP standardization process, it was decided that downlink operation for system bandwidths above 20 MHz will be based on aggregation of multiple component carriers at different frequencies. Such carrier aggregation can be used to support operation in systems with both contiguous and non-contiguous spectrum (e.g., a non-contiguous system may include component carriers at 800 MHz, 2 GHz and 3.5 GHz). Legacy mobile devices may only be able to communicate using a single, backward-compatible component carrier, but more advanced multi-carrier capable terminals may be able to use multiple component carriers simultaneously.

[0003] As mobile (cellular) communications technology has evolved, it has been proposed to provide improved communications in a relatively small geographic area by having small cells (e.g., "pico" or "femto" cells) coexist with larger ("macro") cells, and to provide improved communications capabilities in the localized geographic area that the small cells cover. These small cells may be provided on the same carrier as the macro cells, or may be provided on a different (e.g., higher frequency) dedicated carrier.

[0004] More recently, it has been proposed to allow user data for a particular user device, such as a mobile telephone or other mobile communications device (also referred to as "user equipment" or "UE"), to be communicated via a different cell to a cell to which control data for that user device is communicated. Specifically, it has been proposed to allow the user plane (U-plane) and control plane (C-plane) for a particular user device to be split between a small cell and a macro cell, such that U-plane data is communicated via the small cell and C-plane data is communicated via the macro cell.

[0005] The proposed small cells are effectively "pseudo" or "phantom" cells, since they do not provide traditional cell-specific signals and / or channels such as carrier reference signals, master information / system information broadcasts, primary / secondary synchronization signals, etc.

[0006] In theory, the proposed C-plane / U-plane split provides an optimization between the benefits of better connectivity typically provided by macro cells for critical control signaling, and the benefits of higher throughput and more versatile, energy-efficient, and cost-effective communications provided by small cells using higher and / or wider frequency bands for larger amounts of user data.

[0007] However, the C-plane / U-plane split proposal presents several challenges that need to be addressed if such a proposal is to be actually implemented in global communication networks.

[0008] One such challenge is providing adequate communications security where different base stations are responsible for U-plane and C-plane signaling, respectively, while ensuring that user devices can correctly encrypt / decrypt user and control data, which can undesirably significantly complicate signaling between the core network, base stations, and user devices.

[0009] Furthermore, to ensure adequate security, it is beneficial to be able to regenerate the security keys used for encryption and integrity protection from time to time ("key update" or "key refresh"). Such dynamic key changes can be the result of an explicit key update procedure or an implicit key refresh procedure. To ensure that the security parameters used for encryption and integrity protection remain unique, key refresh is usually required, for example, when a Packet Data Convergence Protocol (PDCP) counter ("PDCP COUNT") used as encryption input reaches its limit value and "wraps around" or "rolls over" back to its initial value. Key update / key refresh avoids the risk that a previously used PDCP COUNT is reused in combination with the same security key as input for encryption, thereby avoiding periodic reuse of previous security parameters.

[0010] However, since PDCP counts are maintained in the U-plane, while the control signaling required for key updates occurs in the C-plane, it is currently not possible to perform such dynamic key refresh when the U-plane and C-plane are split. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention aims to provide a base station, user equipment and associated methods which overcome or at least mitigate the above problems. [Means for solving the problem]

[0012] According to one aspect of the invention, a base station of a communication system is provided with: means for providing user plane communications for a user equipment (UE) connected to said base station and to a further base station; means for receiving a first security key from said further base station arranged to provide control plane signalling to said UE; means for deriving a security key K, which is used for user plane traffic according to a predefined encryption algorithm, using said first security key. UPenc and a means for deriving a security key K used for the user plane traffic for user plane communications provided to the UE. UPenc and means for using the same.

[0013] According to a further aspect of the invention, there is provided a method performed by a base station of a communication system, comprising the steps of: providing user plane communications for a user equipment (UE) connected to said base station and a further base station; receiving a first security key from said further base station configured to provide control plane signalling for said UE; and deriving a security key K to be used for user plane traffic according to a predefined encryption algorithm using said first security key. UPenc and deriving a security key K to be used for the user plane traffic for user plane communications provided to the UE. UPenc and using the same.

[0014] According to a further aspect of the present invention, a user equipment (UE) configured for communicating with a plurality of base stations is provided, the user equipment (UE) comprising: means for receiving control plane signaling from a first base station; means for performing user plane communication between a second base station and the UE; means for deriving a security key for the second base station from a security key for the first base station; and means for deriving a security key K for user plane traffic according to a predefined encryption algorithm using the security key for the second base station. UPencand a means for deriving a security key K used for the user plane traffic for the user plane communication between the UE and the second base station. UPenc and means for using the same.

[0015] According to a further aspect of the present invention, there is provided a method performed by a user equipment (UE) configured to communicate with a plurality of base stations, the method comprising: receiving control plane signaling from a first base station; performing user plane communication between a second base station and the UE; deriving a security key for the second base station from a security key for the first base station; and deriving a security key K for user plane traffic according to a predetermined encryption algorithm using the security key for the second base station. UPenc deriving a security key K to be used for the user plane traffic for the user plane communication between the UE and the second base station; UPenc and using the same.

[0016] Aspects of the invention extend to a computer program product, such as a computer readable storage medium having instructions stored thereon, operable to program a programmable processor to perform the methods set out above or as described in the aspects and possibilities set out in the claims, and / or to program a suitably configured computer to provide an apparatus as set out in any of the claims.

[0017] Each feature disclosed in this specification (including the claims) and / or shown in the drawings may be incorporated in the present invention independently of (or in combination with) any other feature disclosed and / or shown. In particular, but not by way of limitation, any feature of a claim dependent on a particular independent claim may be incorporated in that independent claim in any combination or individually.

[0018] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing a communication system. [Diagram 2] FIG. 2 illustrates an encryption / integrity key hierarchy used in the communication system of FIG. [Diagram 3] FIG. 2 illustrates a key derivation scheme used by a base station in the communication system of FIG. [Figure 4] FIG. 2 illustrates a key derivation scheme used by a mobile communication device in the communication system of FIG. [Diagram 5] 2 is a simplified block diagram of a mobile communication device for the communication system of FIG. 1. [Figure 6] 2 is a simplified block diagram of a "macro" base station for the communication system of FIG. 1. [Figure 7] 2 is a simplified block diagram of a "pico" base station for the communication system of FIG. 1. [Figure 8] 2 is a simplified block diagram of a mobility management entity for the communication system of FIG. 1. [Figure 9] 2 is a simplified timing diagram illustrating the operation of the communication system of FIG. 1 when performing a first security procedure. [Figure 10] 2 is a simplified timing diagram illustrating the operation of the communication system of FIG. 1 when performing a second security procedure. [Figure 11] FIG. 2 is a simplified timing diagram illustrating the operation of the communication system of FIG. 1 when performing a third security procedure. [Figure 12] FIG. 2 is a simplified timing diagram illustrating operation of the communication system of FIG. 1 when performing a fourth security procedure. [Figure 13] 2 is a simplified timing diagram illustrating the operation of the communication system of FIG. 1 in performing an authentication and key agreement procedure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Overview Figure 1 illustrates diagrammatically a mobile (cellular) communications system 1 in which any user of a plurality of mobile communications devices 3-1, 3-2, 3-3 can communicate with other users via one or more of a plurality of base stations 5-1, 5-2, 5-3 and a core network 110. In the system illustrated in Figure 1, each illustrated base station 5 is an evolved universal terrestrial radio access network (E-UTRAN) base station (i.e., "eNB") capable of operating in a multi-carrier environment.

[0021] The core network 110 comprises several functional / logical entities, including a Mobility Management Entity (MME) 112, a Home Subscriber Server (HSS) 114 and an Authentication Center (AuC) 116.

[0022] The MME 112 is the key control node for the LTE access network. The MME is responsible, among other things, for authenticating users (by interacting with the HSS 114). Non-Access Stratum (NAS) signaling terminates in the MME 112. The MME 112 is also the intra-network termination point for ciphering / integrity protection for NAS signaling and performs security key management.

[0023] The HSS 114 comprises a central database containing user-related and subscription-related information. The functions of the HSS 114 include functions such as mobility management, call and session establishment assistance, user authentication and access authorization. The HSS 114 includes the functions of the AuC 116 in this exemplary embodiment (although this can also be provided separately). The AuC 116 function provides authentication of each mobile communication device 3 (more specifically, the associated Subscriber Identity Module (SIM) card) that attempts to connect to the core network 110 (e.g., when the mobile communication device 3 is powered on). Upon successful authentication, the HSS 114 manages the SIMs and services as described above. As will be described in further detail below, the AuC 116 function also generates encryption keys, which are subsequently used to encrypt all wireless communications (voice, SMS, etc.) between the mobile communication device 3 and the core network 110.

[0024] In Fig. 1, the base station labeled 5-1 comprises a so-called "macro" base station operating a geographically relatively large "macro" cell 10-1 with an associated component carrier having a first frequency (F1). The other base stations 5-2, 5-3 shown in Fig. 1 each comprise a so-called "pico" base station operating a respective "pico" cell 10-2, 10-3. Each pico cell 10-2, 10-3 is operated on a respective component carrier having a corresponding frequency band (F2). The power used to provide the pico cells 10-2, 10-3 is lower than the power used for the macro cell 10-1, and therefore the pico cells 10-2, 10-3 are smaller than the macro cell 10-1.

[0025] The macro base station 5-1 provides control signaling 13-1 in the control plane ("C-plane") to mobile communication devices, such as mobile communication device 3-1, located in the macro cell 10-1 that it operates. The macro base station 5-1 also communicates user data 11-1 in the user plane ("U-plane") to and from mobile communication devices, such as mobile communication device 3-1, located in the macro cell that it operates.

[0026] However, for picocells 10-2, 10-3, the provision of the U-plane and C-plane is split between the macro base station 5-1 and the pico base station 5-2 or 5-3 operating the picocell 10-2, 10-3. Specifically, the macro base station 5-1 provides control signaling 13-2, 13-3 in a control plane ("C-plane") to mobile communication devices such as mobile communication devices 3-2, 3-3 located in the picocell 10-2, 10-3 operated by the pico base station 5-2, 5-3. In contrast, each pico base station 5-2, 5-3 communicates user data 11-2, 11-3 in the U-plane with the respective mobile communication devices 3-2, 3-3 in the picocell 10-2, 10-3 operated by the pico base station 5-2, 5-3.

[0027] C-plane signaling includes, among other control signaling, signaling related to U-plane communications, such as signaling for controlling resources used for user plane communications, signaling for controlling the establishment and release of user plane communications bearers, and signaling for controlling mobility of user plane communications between cells (e.g., handover).

[0028] More specifically, C-plane signaling includes control signaling including broadcast of system information, paging, establishment, maintenance and release of RRC connections between the mobile communication device 3 and the network, security functions including key management, establishment, configuration, maintenance and release of point-to-point radio bearers, mobility functions (handover and cell reselection), Quality of Service (QoS) management functions, measurement reporting and control of reporting, and Radio Resource Control (RRC) signaling for resource allocation for U-plane communications.

[0029] The security information required to encrypt / decrypt (encrypt / decrypt) the C-plane data for each picocell 10-2, 10-3 (and for integrity protection in the C-plane) is provided to the macro base station 5-1. The macro base station 5-1 uses the security information to derive security keys suitable for encrypting / decrypting (encrypting / decrypting) the control signaling for each mobile communication device 3-2, 3-3 located in either of the picocells 10-2, 10-3.

[0030] The security information required to encrypt / decrypt (encrypt / decrypt) the U-plane data for each picocell 10-2, 10-3 (and for any integrity protection in the U-plane) is provided to the pico base station 5-2, 5-3 operating that picocell 10-2, 10-3. Each pico base station 5-2, 5-3 determines a security key suitable for encrypting / decrypting (encrypting / decrypting) the user data for each mobile communication device 3-2, 3-3 located within the picocell 10-2, 10-3 operated by that base station 5-2, 5-3.

[0031] Each mobile communication device 3 is also provided with the security information needed to encrypt / decrypt (encrypt / decrypt) the C-plane and U-plane data (as well as for any integrity protection). From the security information, each mobile communication device 3 derives the appropriate security keys to encrypt / decrypt (encrypt / decrypt) the user and control data for that device.

[0032] Each mobile communication device 3-2, 3-3 communicating through the pico cell 10-2, 10-3 is also given an indication that the C-plane and U-plane are split between the macro base station and the pico base station. This is beneficial as it helps ensure that the mobile communication devices 3-2, 3-3 know which base station 5 is responsible for the C-plane and which base station 5 is responsible for the U-plane. Thus, the mobile communication devices 3-2, 3-3 can derive keys for encrypting / decrypting (encrypting / decrypting) their respective U-plane data (and for any integrity protection in the U-plane) even if the base station handling the U-plane communications is different from the base station providing the C-plane communications.

[0033] Security Key Hierarchy and Key Derivation 2 to 4 show the security key hierarchy and key derivation in the mobile communication system of FIG.

[0034] Specifically, Figure 2 illustrates an encryption / integrity key hierarchy used in the mobile communications system of Figure 1. Figure 3 illustrates a key derivation scheme used by a base station in the communications system of Figure 1, and Figure 4 illustrates a key derivation scheme used by a mobile communications device in the communications system of Figure 1.

[0035] 2-4 are based on similar figures from 3GPP Technical Standard (TS) 33.401v12.6.0, which includes further details of the security mechanisms used in the mobile communication system of FIG. 1, as will be appreciated by those skilled in the art.

[0036] 2-4, the mobile communication system 1 uses several security key parameters, which for illustrative purposes can be considered to be arranged in a hierarchy, where keys at lower levels in the hierarchy can be derived from keys higher in the hierarchy (possibly in combination with other parameters) using an appropriate key derivation function (KDF). In this exemplary embodiment, the KDF used to derive the security keys is the KDF described in 3GPP TS 33.220v11.4.0 (Appendix B) using inputs as described in 3GPP TS 33.401v12.6.0 (Appendix A).

[0037] As can be seen in FIGS. 2 to 4 , the security information used in the mobile communication system 1 includes the following security key parameters: General key parameters: · K is a permanent key stored in the mobile communication device 3 and on the USIM or UICC in the AuC 116 . CK and IK ("cipher key" and "integrity key", respectively) are a pair of keys derived in the AuC 116 and on the USIM / UICC during the AKA procedure. CK, IK are treated differently depending on whether they are used in an evolved packet system or a legacy security context, as described in 3GPP TS 33.401 subclause 6.1.2. ·K ASME is an intermediate key derived within the HSS 114 and within the mobile communication device 3 from the CK and IK (and the serving network identification (SNid)). ·K eNB is K ASME , which is a key derived by the mobile communication device 3 and the MME 112 (or possibly by the mobile communication device 3 and a target eNB during handover). Keys for NAS traffic: ·K NASintis the key used to protect NAS traffic using a specific integrity algorithm. This key is calculated using the KDF with inputs as specified in 3GPP TS 33.401, clause A.7, to obtain K ASME , and an identifier for the integrity algorithm, by the mobile communication device 3 and the MME 112. ·K NASenc is the key used to protect NAS traffic using a particular encryption algorithm. This key is calculated using the KDF with inputs as specified in 3GPP TS 33.401, clause A.7, to obtain K ASME , and the encryption algorithm identifier by the mobile communication device 3 and the MME 112. Keys for user plane traffic: ·K UPenc is the key used to protect U-Plane traffic using a particular encryption algorithm. This key is calculated using the KDF with inputs as specified in 3GPP TS 33.401, clause A.7, to obtain K eNB , and an identifier for the encryption algorithm by the mobile communication device 3 and the macro base station 5-1. However, if the U-plane / C-plane is split between the pico base station and the macro base station as described above, K UPenc is obtained at the pico base stations 5-2, 5-3 for use in protecting U-plane traffic using a particular encryption algorithm (described in more detail below). ·K UPint is the key used to protect U-Plane traffic between the relay node (RN) and the donor eNB (DeNB) using a specific integrity algorithm. This key is calculated using the KDF with inputs as specified in 3GPP TS 33.401, clause A.7, as eNB , and an identifier for the integrity algorithm by the RN and DeNB. Keys for control plane (RRC) traffic: ·K RRCintis the key used to protect Radio Resource Control (RRC) traffic with a specific integrity algorithm. RRCint is calculated using a KDF with input as specified in 3GPP TS 33.401, clause A.7. eNB and an identifier for the integrity algorithm is derived by the mobile communication device 3 and the macro base station 5-1. ·K RRCenc is the key used to protect the RRC traffic using a specific encryption algorithm. RRCenc is calculated using a KDF with input as specified in 3GPP TS 33.401, clause A.7. eNB and an identifier for the encryption algorithm by the mobile communication device 3 and the macro base station 5-1. Intermediate key: NH ("next hop") is a key derived by the mobile communication device 3 and the MME 112 using a KDF with inputs as specified in clause A.4 of 3GPP TS 33.401 to provide forward security (e.g. during handover) as described in clause A.7.2.8 of 3GPP TS 33.401. ·K eNB * NH or currently valid K for use in deriving keys during handover / context change using a KDF with input as specified in 3GPP TS 33.401, clause A.5. eNB , which is a key derived by the mobile communication device 3 and the source base station. eNB * is transferred from the source base station to the target base station. The target base station is the base station that is to be used when the mobile communication device 3 is handed over. eNB As the received K eNB * As will be explained in more detail later, in one example method, this parameter is advantageously reused when the C-plane / U-plane is split.

[0038] Several other notable parameters are also used in the security architecture of the mobile telecommunications system 1. These parameters include: · AMF, a so-called authenticated management field, in a database in the AuC 116 and on the SIM card of the mobile communication device 3. The AMF is pre-shared between the mobile communication device 3 and the AuC 116 and is used when calculating certain security parameters (e.g. MAC and XMAC as explained later). · OP, the so-called operator variant algorithm configuration field in the database in the AuC 116 and on the SIM card of the mobile communication device 3. · SQN, a sequence number that is incremented each time the network attempts to authenticate the mobile communication device 3. RAND, a random number used in key generation and authentication. ·AK, the so-called anonymous key, generated in AuC116. · XRES, the so-called “expected responses” generated in AuC116. ·RES is a response parameter equivalent to XRES, but is generated by the mobile communication device 3 for sending to the MME 112 for comparison with XRES for authentication purposes. ·MAC is a message authentication code generated in AuC116. · XMAC is an expected MAC value generated in the mobile communication device 3 to authenticate the message against the received MAC. ·AUTN is the so-called authentication token generated in AnC116.

[0039] When the MME 112 receives an attach request from the mobile communication device 3, it sends an authentication data request to the AuC 116 / HSS 114. After deriving the RAND, XRES, CK, IK and AUTN, the AuC 116 combines those parameters to generate a so-called authentication vector (AV=RAND|XRES|CK|IK|AUTN), which is sent to the MME 112. The MME 112 can then retrieve the individual parameters from the AV for sending to the mobile communication device during the authentication and key generation process as described in more detail below.

[0040] To encrypt / decrypt user plane data, we take as input K UPenc An encryption function is used having information identifying the radio bearer used for the communication ("BEARER"), a single bit indicator of the direction of the communication ("DIRECTION"), the length of the required key stream ("LENGTH"), and a bearer specific, but time and direction dependent, 32-bit value of an incremental counter ("COUNT") corresponding to the 32-bit PDCP COUNT held in the PDCP layer for the mobile communication device 3 and the pico base stations 5-2, 5-3.

[0041] Mobile Communication Devices Figure 5 is a block diagram illustrating the main components of the mobile communication devices 3 shown in Figure 1. Each mobile communication device 3 consists of a mobile (or "cell") telephone capable of operating in a multi-carrier environment. The mobile communication devices 3 comprise transceiver circuitry 510 operable to transmit and receive signals to and from a base station 5 via at least one antenna 512. The mobile communication devices 3 comprise a user interface 514 (e.g., touch screen, keypad, microphone, speaker, etc.) through which a user can interact with the device.

[0042] The mobile communication device includes a subscriber identity module (SIM) 530 in the form of a universal SIM (USIM) operating on a universal integrated circuit card (UICC). The SIM 530 comprises a USIM / UICC security module 532 for obtaining and storing a permanent key "K" 534-1, which in operation is used to generate other security parameters used for communication security. The USIM / UICC security module 532 is also operable to derive other security parameters 534-2, such as a cipher key (CK) and an integrity key (IK), using K and a "random" value (e.g., a value of RAND provided by the AuC 116 via the MME 112). The SIM 530 has an identity 536 in the form of an international mobile subscriber identity (IMSI).

[0043] The operation of the transceiver circuitry 510 is controlled by a controller 516 according to software stored in a memory 518 .

[0044] The software includes, among other things, an operating system 520 , a communications control module 522 , and a security administration module 525 .

[0045] The communication control module 522 is configured to manage communications with macros and / or base stations 5 on associated component carriers. The communication control module 522 is configured to manage NAS communications (indirectly via base stations) with the MME 112. The communication control module 522 includes a U-plane module 523 for handling user data and a C-plane module 524 for handling control signaling such as radio resource control messages.

[0046] The security management module 525 is configured to manage communication security including execution of authentication procedures, key and related security parameter generation and usage, authentication and key agreement (AKA) within the scope of execution in the mobile communication device 3. The security management module 525 may handle retrieval / generation of parameters 526 suitable for use in the authentication / key generation procedures. These parameters include UICC / USIM parameters 526-1 retrieved from the SIM 530 (e.g. parameters 534-2 such as CK and IK derived by the SIM 530), parameters 526-2 received from other sources (e.g. parameters such as AUTN and RAND received from the MME 112 in Non-Access Stratum (NAS) signaling) and parameters 526-3 that may be derived in the mobile communication device (e.g. parameters 534-4 such as CK and IK derived by the SIM 530). ASME , K NASint , K NASenc , K eNB , K eNB * , N.H., K. UPenc , K RRCint , K RRCenc The security administration module 525 also includes an AKA module 528 for managing AKA procedures to the extent performed by the mobile communication device 3.

[0047] Macro base station Figure 6 is a block diagram showing the main components of the macro base station 5-1 shown in Figure 1. The macro base station 5-1 consists of an E-UTRAN multi-carrier capable base station comprising a transceiver circuit 610 operable to transmit signals to and receive signals from the mobile communication device 3 via at least one antenna 612. The base station 5-1 is also operable to transmit and receive signals to and from the MME 112 of the core network 110 via an MME(S1) interface 614, and to and from other base stations 5 via an eNB(X2) interface 616.

[0048] The operation of the transceiver circuitry 610 is controlled by a controller 616 according to software stored in a memory 618 .

[0049] The software includes, among other things, an operating system 620 , a communications control module 622 , and a security administration module 625 .

[0050] The communication control module 622 is configured to manage communications between the macro base station 5-1 and the mobile communication devices 3 operating within the geographic area covered by the macro cell 10-1. The communication control module 622 is also configured to manage S1-AP signaling between the macro base station 5-1 and the MME 112 and X2-AP signaling between the macro base station 5-1 and other base stations.

[0051] The communications control module 622 includes a U-plane module 623 for handling user data for the mobile communications device 3-1 communicating via the macrocell 10-1, and a C-plane module 624 for generating control signaling, such as radio resource control (RRC) messages, for transmission to the mobile communications device 301 communicating via the macrocell 10-1 and for the mobile communications devices 3-2, 3-3 communicating user data via their respective picocells 10-2, 10-3.

[0052] The security management module 625 is configured to manage communication security within the scope implemented in the macro base station 5-1, including the execution of authentication procedures, key and related security parameter generation and utilization, and authentication and key agreement (AKA) procedures.

[0053] The security management module 625 may handle the receipt / generation of parameters 626 suitable for use in the authentication / key generation procedure. These parameters 626 may include parameters 626-1 received from other sources (e.g., K 626-2 received from the MME 112). eNBor NH, or K received from the source base station during handover eNB * ) The parameters 626 may also be derived in the macro base station 5-1 during normal operation (for example, K UPenc , K RRCint , K RRCenc ), or may be derived in the macro base station 5-1 during handover (for example, K eNB * or K when acting as a target node eNB (=K eNB * ) etc.) parameters 626-2. The security management module 625 also includes an AKA module 628 for managing the AKA procedures to the extent performed by the macro base station 5-1.

[0054] Pico Base Station Figure 7 is a block diagram showing the main components of the pico base station 5-2, 5-3 shown in Figure 1. The pico base station 5-2, 5-3 comprises an E-UTRAN multi-carrier capable base station comprising transceiver circuitry 710 operable to transmit signals to and receive signals from mobile communication devices 3 via at least one antenna 712. The pico base station 5-2, 5-3 is also operable to transmit and receive signals to and from the MME 112 of the core network 110 via an MME(S1) interface 714, and to and from other base stations via an eNB(X2) interface 716.

[0055] The operation of the transceiver circuitry 710 is controlled by a controller 716 according to software stored in memory 718 .

[0056] The software includes, among other things, an operating system 720 , a communications control module 722 , and a security administration module 725 .

[0057] The communication control module 722 is configured to manage communications between the pico base stations 5-2, 5-3 and the mobile communication devices 3-2, 3-3 communicating via the pico cells 10-2, 10-3. The communication control module 722 is also configured to manage S1-AP signaling between the pico base stations 5-2, 5-3 and the MME 112, and X2-AP signaling between the pico base stations 5-2, 5-3 and other base stations.

[0058] The communication control module 722 includes a U-plane module 723 for handling user data for the mobile communication devices 3-2, 3-3 communicating via the picocells 10-2, 10-3.

[0059] The security management module 725 is configured to manage communications security within the scope implemented in the pico base stations 5-2, 5-3, including the performance of authentication procedures, key and associated security parameter generation and utilization, and authentication and key agreement (AKA) procedures.

[0060] The security administration module 725 may handle the receipt / generation of parameters 726 suitable for use in the authentication / key generation procedure. These parameters 726 may include parameters 726-1 (e.g., in this embodiment, K eNB ) The parameters 726 also include parameters 726-2 (e.g., K UPenc The security administration module 725 also includes an AKA module 728 for managing the AKA procedures to the extent performed by the pico base stations 5-2, 5-3.

[0061] MME Figure 8 is a block diagram illustrating the main components of the mobility management entity (MME) 112 shown in Figure 1. The MME 112 comprises a transceiver circuit 810 operable to transmit signals to and receive signals from other network devices (such as the HSS) via an associated network entity interface 812. The transceiver circuit 810 is also operable to transmit signals to and receive signals from the base stations 5 via an eNB (S1) interface 816, including S1-AP signaling for the base stations 5 and NAS signaling for the mobile communication device 3 that is transparent to the base stations.

[0062] The operation of the transceiver circuitry 810 is controlled by a controller 816 according to software stored in a memory 818 .

[0063] The software includes, among other things, an operating system 820 , a communications control module 822 , and a security administration module 825 .

[0064] The communication control module 822 is configured to manage NAS signaling between the MME 112 and the mobile communication device 3, and S1-AP signaling between the MME 112 and the base station 5.

[0065] The security management module 825 is configured to manage communication security, including performing authentication procedures, key and associated security parameter generation and usage, and authentication and key agreement (AKA) procedures within the scope of execution in the MME 112.

[0066] The security management module 825 may handle the receipt / generation of parameters 826 suitable for use in the authentication / key generation procedure. These parameters 826 may include parameters 826-1 received from other sources (e.g., CK, IK, AUTN, K retrieved from AV received from the HSS 114 / AuC 116, etc.). ASME, RAND, XRES). These parameters 826 also include parameters 826-2 (e.g., K NASint , K NASenc , K eNB , NH, etc. The security management module 825, to the extent executed by the MME 112, also includes an AKA module 828 for managing the AKA procedures.

[0067] Operational Overview - Security parameters provided Figures 9-13 show simplified timing diagrams each illustrating the operation of the communication system of Figure 1 when performing a respective variant of a security procedure. As will be appreciated by those skilled in the art, the timing diagrams show only signaling that is specifically related to security. Other signaling will typically occur, but has been omitted from the simplified timing diagrams for reasons of clarity.

[0068] As can be seen in Figures 9 to 13, each illustrated security procedure involves the selection of appropriate security parameters (in particular, K UPenc Each uses a different mechanism to ensure that the appropriate value of

[0069] Although the different security procedures shown in Figures 9-13 are shown separately, it will be appreciated that significant features of the security procedures may be combined where appropriate, or provided as options for alternative implementations within a deployed system.

[0070] K based on MME eNB offer FIG. 9 shows a simplified timing diagram illustrating the operation of the telecommunications system of FIG. 1 when performing a first security procedure, in which appropriate security parameters, in particular K UPenc The appropriate value of is generated.

[0071] At the start of the illustrated security procedure, a mobile communication device 3 wishing to initiate communications in a pico cell 5-1, 5-2 sends a non-access stratum (NAS) message requesting attachment (e.g., a “NAS Attach Request” message) to the MME 112 (transparently via the macro base station 5-1) at S910, including information identifying the SIM card 530 of the mobile communication device 3 (e.g., the “International Mobile Subscriber Identity (IMSI)”).

[0072] The MME 112 responds to this request by sending a message (e.g., an “Authentication Data Request” message) to the HSS 114 requesting authentication and including information identifying the SIM card 530, at S912. The AuC function 116 of the HSS 114 derives RAND, XRES, CK, IK, AUTN and combines them to form an authentication vector (AV=RAND|XRES|CK|IK|AUTN) for the SIM card 530, at S914, and sends the generated AV to the MME 112 (e.g., in an “Authentication Data Response” message), at S916.

[0073] The MME 112 retrieves the IK, CK, XRES, RAND and AUTN from the AV at S918 and sends the AUTN and RAND parameters to the mobile communication device 3 using NAS signaling at S920 (eg, in a "NAS Authentication Request" message).

[0074] The mobile communication device 3 responds at S922 by authenticating the network using the received AUTN and deriving appropriate security-related parameters (IK, CK, RES, etc.) using the stored permanent security key "K" and the received AUTN and RAND parameters (and any other parameters, e.g., AMF for XMAC determination, if necessary). Assuming authentication is successful, the mobile communication device 3 sends the calculated value of RES to the MME 112 at S924 (e.g., in a "NAS Authentication Response" message).

[0075] The MME 112 checks the received RES value against XRES in S926, resets the downlink NAS count, and ASME , K eNB , K NASint , K NASenc The MME 112 then initiates NAS signaling security between the MME 112 and the mobile communication device 3 at S928 by sending a NAS Security Mode Command message informing the mobile communication device 3 of the respective algorithms to use for integrity protection and (decryption).

[0076] The mobile communication device 3, in S930, ASME , K eNB , K NASint , K NASenc and then responds at S932 by sending a response message informing the MME 112 that the NAS signaling security initialization is complete.

[0077] The method then continues by initiating security context setup in both the pico base stations 5-2, 5-3 and the macro base station 5-1 by sending substantially identical S1 application (A1-AP) messages (e.g., "S1-AP initial context setup request" messages) to the pico base stations 5-2, 5-3 at S934 and to the macro base station 5-1 at S936. eNB and security feature details for the mobile communication device 3. .

[0078] After that, the pico base stations 5-2 and 5-3 receive the K eNB security parameters required for U-plane encryption / decryption (e.g., K UPenc Similarly, in S940, the macro base station 5-1 derives the received K eNBsecurity parameters required for C-plane encryption / decryption (e.g., K RRCint , K RRCenc ) is derived.

[0079] At S942, assuming the security context setup in the pico base station 5-2, 5-3 is successful, the pico base station 5-2, 5-3 confirms this to the MME 112 in an appropriate S1-AP message (eg an "S1-AP Initial Context Setup Response" message).

[0080] The macro base station 5-1 then initiates RRC (and user plane) security context setup in the mobile communication device 3 at S944 using RRC signaling (e.g., an "RRC Security Mode Command" message), the RRC signaling including information identifying the algorithms to be used for integrity protection and / or encryption and information indicating that the U-plane and C-plane are split (e.g., in the form of dedicated information elements (IEs), modified IEs, or reuse of existing IEs).

[0081] The mobile communication device 3, in S946, eNB From the value of RRCint , K RRCenc The mobile communication device 3 responds by initializing an RRC security context for communication with the macro base station 5-1 by deriving a value of K eNB , for use with user plane signaling between pico base stations 5-2, 5-3. UPenc By deriving the value of , it initializes the U-plane security context for communication with the pico base stations 5-2, 5-3.

[0082] Assuming the security context setup is successful, the mobile communication device 3 acknowledges this in S932 by sending an appropriate response message (eg an "RRC security mode complete" message) to the macro base station 5-1 in S950.

[0083] The macro base station 5-1 confirms the success of the security context setup to the MME 112 in an appropriate S1-AP message (eg, an "S1-AP Initial Context Setup Request" message) in S952.

[0084] Upon successful initialization of the various security contexts (NAS and AS) in the various devices, in S954, a control signaling connection and a user signaling connection can be set up and the mobile communication device 3 can start communications where control plane signaling is provided by the macro base station 5-1 (S956) and U-plane signaling is provided via the pico base stations 5-2, 5-3 (S958).

[0085] Therefore, advantageously, the method provides an efficient way of providing appropriate communication security where different base stations are responsible for U-plane and C-plane signaling, respectively, and the user device can maintain appropriate security contexts for both the U-plane and the C-plane, allowing the user device to correctly encrypt / decrypt user and control data, and to know the security parameters (keys) used in the different base stations.

[0086] This approach has the advantage over other methods described herein in that it does not require base station changes in terms of base station signaling (on X2, or possibly on a new interface), and avoids the associated complexity of the X2-AP, but has the advantage that repetition of S1 signaling is avoided, and therefore S1 signaling overhead is reduced.

[0087] K based on base station eNB offer FIG. 10 shows how pico base stations 5-2, 5-3 respond to signaling from the macro base station 5-1 by selecting appropriate security parameters, in particular K UPenc 2 shows a simplified timing diagram illustrating the operation of the communication system of FIG. 1 when performing a second security procedure in which appropriate values ​​of

[0088] At the start of the security procedures shown in FIG. 10, a mobile communication device 3 wishing to initiate communication in a pico cell 5-1, 5-2 sends a non-access stratum (NAS) message requesting attachment (e.g., a “NAS Attach Request” message) to the MME 112 (transparently via the macro base station 5-1) at S1010, including information identifying the SIM card 530 of the mobile communication device 3 (e.g., the “International Mobile Subscriber Identity (IMSI)”).

[0089] The MME 112 responds to this request by sending a message (e.g., an “Authentication Data Request” message) to the HSS 114 requesting authentication and including information identifying the SIM card 530, at S1012. The AuC function 116 of the HSS 114 derives RAND, XRES, CK, IK, AUTN and combines them to form an authentication vector (AV=RAND|XRES|CK|IK|AUTN) for the SIM card 530, at S1014, and sends the generated AV to the MME 112 (e.g., in an “Authentication Data Response” message), at S1016.

[0090] The MME 112 retrieves the IK, CK, XRES, RAND and AUTN from the AV at S1018 and sends the AUTN and RAND parameters to the mobile communication device 3 using NAS signaling at S1020 (eg, in a "NAS Authentication Request" message).

[0091] The mobile communication device 3 responds at S1022 by authenticating the network using the received AUTN and deriving appropriate security related parameters (IK, CK, RES, etc.) using the stored permanent security key "K" and the received AUTN and RAND parameters (and any other parameters, e.g., AMF for XMAC determination, if necessary). Assuming authentication is successful, the mobile communication device 3 sends the calculated value of RES to the MME 112 at S1024 (e.g., in a "NAS Authentication Response" message).

[0092] The MME 112 checks the received RES value against XRES in S1026, resets the downlink NAS count, and ASME , K eNB , K NASint , K NASenc The MME 112 then initiates NAS signaling security between the MME 112 and the mobile communication device 3 at S1028 by sending a NAS security mode command message informing the mobile communication device 3 of the respective algorithms to use for integrity protection and (decryption).

[0093] In S1030, the mobile communication device 3 ASME , K eNB , K NASint , K NASenc and then responds at S1032 by sending a response message informing the MME 112 that the NAS signaling security initialization is complete.

[0094] Thereafter, the method continues by initiating security context setup at the macro base station 5-1 by sending an S1 application (A1-AP) message (e.g., an "S1-AP initial context setup request" message) to the macro base station 5-1 at S1034. eNBand details of security capabilities for the mobile communication device 3.

[0095] The macro base station 5-1 initiates security context setup in the pico base stations 5-2, 5-3 by sending an X2 application (X2-AP) message (e.g., a new "X2-AP context setup" message) to the pico base stations 5-2, 5-3 in S1036. eNB and details of security capabilities for the mobile communication device 3.

[0096] After that, in S1038, the pico base stations 5-2 and 5-3 receive the K eNB from the security parameters required for U-plane encryption / decryption (e.g., K UPenc Similarly, in S1040, the macro base station 5-1 derives K eNB From the above, the security parameters required for C-plane encryption / decryption (e.g., K RRCint , K RRCenc ) is derived.

[0097] Assuming at S1042 that the security context setup in the pico base stations 5-2, 5-3 is successful, the pico base stations 5-2, 5-3 confirm this to the macro base station 5-1 in an appropriate X2-AP message (eg a "X2-AP context setup response" message).

[0098] The macro base station 5-1 then initiates RRC (and user plane) security context setup in the mobile communication device 3 at S1044 using RRC signaling (e.g., an "RRC Security Mode Command" message), the RRC signaling including information identifying the algorithms to be used for integrity protection and / or encryption and information indicating that the U-plane and C-plane are split (e.g., in the form of dedicated information elements (IEs), modified IEs, or reuse of existing IEs).

[0099] In step S1046, the mobile communication device 3 calculates the pre-calculated K eNB From the value of RRCint , K RRCenc The mobile communication device 3 responds by initializing an RRC security context for communication with the macro base station 5-1 by deriving a value of K eNB , for use with user plane signaling between pico base stations 5-2, 5-3. UPenc By deriving the value of , it initializes the U-plane security context for communication with the pico base stations 5-2, 5-3.

[0100] Assuming the security context setup is successful, the mobile communications device 3 acknowledges this in S1032 by sending an appropriate response message (eg, an "RRC security mode complete" message) to the macro base station 5-1 in S1050.

[0101] The macro base station 5-1 confirms the successful security context setup to the MME 112 in an appropriate S1-AP message (eg, an "S1-AP Initial Context Setup Request" message) at S1052.

[0102] Upon successful initialization of the various security contexts (NAS and AS) in the various devices, in S1054, a control signaling connection and a user signaling connection can be set up and the mobile communication devices can start communicating where control plane signaling is provided by the macro base station 5-1 (S1056) and U-plane signaling is provided via the pico base stations 5-2, 5-3 (S1058).

[0103] Therefore, advantageously, the method provides another efficient way of providing proper communication security where different base stations are responsible for U-plane and C-plane signaling, respectively. A user device can maintain a security context suitable for both the U-plane and the C-plane, which allows the user device to correctly encrypt / decrypt user and control data, and to know the security parameters (keys) used in the different base stations.

[0104] Informing the mobile communication device that the C-plane / U-plane is split in this manner allows the mobile communication device to communicate with the pico cell using a user plane security parameter (K UPenc This provides an efficient way to ensure that one has the information needed to establish that a derivation of (a) is required.

[0105] This approach has the advantage over the first method described herein in that it avoids repetitive S1 signaling and therefore reduces S1 signaling overhead, however the first method has the advantage of making base station changes to base station signaling (over X2, or possibly over a new interface) unnecessary and avoiding the associated complexities of the X2-AP.

[0106] K based on base station UPenc offer FIG. 11 shows a simplified timing diagram illustrating the operation of the communication system of FIG. 1 when performing the third security procedure, in which appropriate security parameters, in particular K UPenc Appropriate values ​​of are generated and forwarded to the pico base stations 5-2, 5-3 via the X2 interface.

[0107] At the start of the security procedures shown in FIG. 11, a mobile communication device 3 wishing to initiate communication in a pico cell 5-1, 5-2 sends a non-access stratum (NAS) message requesting attachment (e.g., a “NAS Attach Request” message) to the MME 112 (transparently via the macro base station 5-1) at S1110, including information identifying the SIM card 530 of the mobile communication device 3 (e.g., the “International Mobile Subscriber Identity (IMSI)”).

[0108] The MME 112 responds to this request by sending a message (e.g., an “Authentication Data Request” message) to the HSS 114 requesting authentication and including information identifying the SIM card 530, at S1112. The AuC function 116 of the HSS 114 derives RAND, XRES, CK, IK, AUTN and combines them to form an authentication vector (AV=RAND|XRES|CK|IK|AUTN) for the SIM card 530, at S1114, and sends the generated AV to the MME 112 (e.g., in an “Authentication Data Response” message), at S1116.

[0109] The MME 112 retrieves the IK, CK, XRES, RAND and AUTN from the AV, in S1118, and sends the AUTN and RAND parameters to the mobile communication device 3 using NAS signaling, in S1120 (eg, in a "NAS Authentication Request" message).

[0110] The mobile communication device 3 responds at S1122 by authenticating the network using the received AUTN and by deriving appropriate security-related parameters (IK, CK, RES, etc.) using the stored permanent security key "K" and the received AUTN and RAND parameters (and any other parameters, e.g., AMF for XMAC determination, if necessary). Assuming authentication is successful, the mobile communication device 3 sends the calculated value of RES to the MME 112 at S1124 (e.g., in a "NAS Authentication Response" message).

[0111] The MME 112 checks the received RES value against XRES, resets the downlink NAS count, and ASME , K eNB , K NASint , K NASenc The MME 112 then initiates NAS signaling security between the MME 112 and the mobile communication device 3 at S1128 by sending a NAS Security Mode Command message informing the mobile communication device 3 of the respective algorithms to use for integrity protection and (decryption).

[0112] In S1130, the mobile communication device 3 ASME , K eNB , K NASint , K NASenc and then responds at S1132 by sending a response message informing the MME 112 that the NAS signaling security initialization is complete.

[0113] Thereafter, the method continues by initiating security context setup at the macro base station 5-1 by sending an S1 application (A1-AP) message (e.g., an "S1-AP initial context setup request" message) to the macro base station 5-1 at S1134. eNBand details of security capabilities for the mobile communication device 3.

[0114] In step S1140, the macro base station 5-1 receives the K eNB From the above, the security parameters required for C-plane protection (e.g., K RRCint , K RRCenc ) and security parameters required for U-plane protection (e.g., K UPenc ) is derived.

[0115] The macro base station 5-1 initiates security context setup in the pico base stations 5-2, 5-3 by sending an X2 application (X2-AP) message (e.g., a new "X2-AP context setup" message) to the pico base stations 5-2, 5-3 in S1136. UPenc and details of security capabilities for the mobile communication device 3.

[0116] K from macro base station 5-1 UPenc Upon receipt of this, and assuming the security context setup in the pico base stations 5-2, 5-3 is successful, in S1142 the pico base stations 5-2, 5-3 confirm this to the macro base station 5-1 in an appropriate X2-AP message (e.g. an “X2-AP Context Setup Response” message).

[0117] The macro base station 5-1 then initiates RRC (and user plane) security context setup in the mobile communication device 3 at S1144 using RRC signaling (e.g., an "RRC security mode command" message), the RRC signaling including information identifying the algorithms to be used for integrity protection and / or encryption and information indicating that the U-plane and C-plane are split (e.g., in the form of dedicated information elements (IEs), modified IEs, or reuse of existing IEs).

[0118] In step S1146, the mobile communication device 3 calculates the pre-calculated K eNB From the value of RRCint , K RRCenc The mobile communication device 3 responds by initializing an RRC security context for communication with the macro base station 5-1 by deriving a value of K eNB , for use with user plane signaling between pico base stations 5-2, 5-3. UPenc By deriving the value of , it initializes the U-plane security context for communication with the pico base stations 5-2, 5-3.

[0119] Assuming the security context setup is successful, the mobile communications device 3 acknowledges this in S1132 by sending an appropriate response message (eg, an "RRC security mode complete" message) to the macro base station 5-1 in S1150.

[0120] The macro base station 5-1 confirms the successful security context setup to the MME 112 in an appropriate S1-AP message (eg, an "S1-AP Initial Context Setup Request" message) in S1152.

[0121] Upon successful initialization of the various security contexts (NAS and AS) in the various devices, in S1154, a control signaling connection and a user signaling connection can be set up and the mobile communication devices can start communications where control plane signaling (S1156) is provided by the macro base station 5-1 and U-plane signaling is provided via the pico base stations 5-2, 5-3 (S1158).

[0122] Therefore, advantageously, the method provides another efficient way of providing proper communication security where different base stations are responsible for U-plane and C-plane signaling, respectively. A user device can maintain a security context suitable for both the U-plane and the C-plane, which allows the user device to correctly encrypt / decrypt user and control data, and to know the security parameters (keys) used in the different base stations.

[0123] Informing the mobile communication device that the C-plane / U-plane is split in this manner allows the mobile communication device to communicate with the pico cell using a user plane security parameter (K UPenc This provides an efficient way to ensure that one has the information needed to establish that a derivation of (a) is required.

[0124] This method is a method in which a pico base station UPenc This has the advantage over other methods described herein in that it is not necessary to derive K UPenc This has the advantage over the present method in terms of security in that the value of K (also used by the mobile phone 3) is not transmitted and therefore cannot be easily compromised (e.g., by "eavesdropping") and user data security cannot be compromised. eNB However, if it is at risk, K UPenc Since we need to know other security keys to derive K UPenc It is not trivial to derive

[0125] K based on base station eNB * offer Between base stations eNB and K UPencIt will be appreciated that the transfer of K is not currently supported under any circumstances. FIG. 12 illustrates a simplified timing diagram showing the operation of the communication system of FIG. 1 in performing the fourth security procedure, and illustrates the transfer of security parameters (K) currently supported for transfer between base stations, but in limited circumstances. eNB * ) is transferred. Specifically, currently, K eNB * The transfer of K is supported during handover. Therefore, this fourth security step eNB * This extends the situations in which it is supported to security context configuration when the U-plane / C-plane are split.

[0126] Specifically, in response to the signaling from the MME 112, the macro base station 5-1 eNB * is generated (corresponding during handover) and transferred to the pico base stations 5-2, 5-3 via the X2 interface.

[0127] At the start of the security procedures shown in FIG. 12, a mobile communication device 3 wishing to initiate communication in a pico cell 5-1, 5-2 sends a non-access stratum (NAS) message requesting attachment (e.g., a “NAS Attach Request” message) to the MME 112 (transparently via the macro base station 5-1) at S1210, including information identifying the SIM card 530 of the mobile communication device 3 (e.g., the “International Mobile Subscriber Identity (IMSI)”).

[0128] The MME 112 responds to this request by sending a message (e.g., an “Authentication Data Request” message) to the HSS 114 requesting authentication and including information identifying the SIM card 530, at S1212. The AuC function 116 of the HSS 114 derives RAND, XRES, CK, IK, AUTN and combines them to form an authentication vector (AV=RAND|XRES|CK|IK|AUTN) for the SIM card 530, at S1214, and sends the generated AV to the MME 112 (e.g., in an “Authentication Data Response” message), at S1216.

[0129] The MME 112 retrieves the IK, CK, XRES, RAND and AUTN from the AV at S1218 and sends the AUTN and RAND parameters to the mobile communication device 3 using NAS signaling at S1220 (eg, in a "NAS Authentication Request" message).

[0130] The mobile communication device 3 responds at S1222 by authenticating the network using the received AUTN and deriving appropriate security related parameters (IK, CK, RES, etc.) using the stored permanent security key "K" and the received AUTN and RAND parameters (and any other parameters, e.g., AMF for XMAC determination, if necessary). Assuming authentication is successful, the mobile communication device 3 sends the calculated value of RES to the MME 112 at S1224 (e.g., in a "NAS Authentication Response" message).

[0131] The MME 112 checks the received RES value against XRES in S1226, resets the downlink NAS count, and ASME , K eNB , K NASint , K NASencThe MME 112 then initiates NAS signaling security between the MME 112 and the mobile communication device 3 at S1228 by sending a NAS Security Mode Command message informing the mobile communication device 3 of the respective algorithms to use for integrity protection and (decryption).

[0132] In S1230, the mobile communication device 3 ASME , K eNB , K NASint , K NASenc and then responds at S1232 by sending a response message informing the MME 112 that the NAS signaling security initialization is complete.

[0133] Thereafter, the method continues by initiating security context setup at the macro base station 5-1 by sending an S1 application (A1-AP) message (e.g., an "S1-AP initial context setup request" message) to the macro base station 5-1 at S1234. eNB and details of security capabilities for the mobile communication device 3.

[0134] The macro base station 5-1 initiates security context setup in the pico base stations 5-2, 5-3 by sending an X2 application (X2-AP) message (e.g., a new "X2-AP context setup" message) to the pico base stations 5-2, 5-3 in S1236. The X2-AP message is a K eNB (and in some cases, the value of NH) eNB * and details of security features for the mobile communication device 3. eNB * The value of is derived in substantially the same way as in the handover case, but is given a different name (e.g., K eNB **) may be given.

[0135] The pico base stations 5-2 and 5-3 are connected to the macro base stations 5-1 to eNB * Upon receiving K, the pico base stations 5-2, 5-3 derive the security parameter(s) required for U-plane encryption / decryption in S1238. eNB * From K eNB (In reality, it is "Pico" K eNB ) and derive the value of the derived picoK eNB From K UPenc Similarly, in S1240, the macro base station 5-1 derives the value of K eNB security parameters required for C-plane encryption / decryption (e.g., K RRCint , K RRCenc ) is derived.

[0136] Assuming the security context setup in the pico base stations 5-2, 5-3 is successful, then in S1242 the pico base stations 5-2, 5-3 confirm this to the macro base station 5-1 in an appropriate X2-AP message (eg a "X2-AP context setup response" message).

[0137] The macro base station 5-1 then initiates RRC (and user plane) security context setup in the mobile communication device 3 at S1244 using RRC signaling (e.g., an "RRC security mode command" message), the RRC signaling including information identifying the algorithms to be used for integrity protection and / or encryption and information indicating that the U-plane and C-plane are split (e.g., in the form of dedicated information elements (IEs), modified IEs, or reuse of existing IEs).

[0138] The mobile communication device 3, in S1246, calculates the pre-calculated ("macro") K eNBFrom the value of RRCint , K RRCenc The mobile communication device 3 responds by initializing an RRC security context for communication with the macro base station 5-1 by deriving a value of K eNB * , and therefore the correct K for use with user plane signaling between the pico base stations 5-2, 5-3. UPenc You can find "Pico" K eNB By deriving the value of , it initializes the U-plane security context for communication with the pico base stations 5-2, 5-3.

[0139] Assuming the security context setup is successful, the mobile communications device 3 acknowledges this in S1232 by sending an appropriate response message (eg an "RRC security mode complete" message) to the macro base station 5-1 in S1250.

[0140] The macro base station 5-1 confirms the successful security context setup to the MME 112 in an appropriate S1-AP message (eg, an "S1-AP Initial Context Setup Request" message) at S1252.

[0141] Upon successful initialization of the various security contexts (NAS and AS) in the various devices, in S1254, a control signaling connection and a user signaling connection can be set up and the mobile communication devices can start communicating where control plane signaling is provided by the macro base station 5-1 (S1256) and U-plane signaling is provided via the pico base stations 5-2, 5-3 (S1258).

[0142] Therefore, advantageously, the method provides another efficient way of providing proper communication security where different base stations are responsible for U-plane and C-plane signaling, respectively. A user device can maintain a security context suitable for both the U-plane and the C-plane, which allows the user device to correctly encrypt / decrypt user and control data, and to know the security parameters (keys) used in the different base stations.

[0143] Informing the mobile communication device that the C-plane / U-plane is split in this manner allows the mobile communication device to communicate with the pico cell using a user plane security parameter (K UPenc This provides an efficient way to ensure that one has the information needed to establish that a derivation of (a) is required.

[0144] This approach has an advantage over other methods described herein in that it does not require the transfer of security parameters that are not currently supported for transfer between base stations. However, other methods described herein do not support the transfer of K eNB * This has the advantage that it requires additional complexity to properly derive .

[0145] Individual Authentication and Key Agreement (AKA) Procedure FIG. 13 shows a simplified diagram illustrating the operation of the communications system of FIG. 1 when performing further security procedures, in which rather than performing a single AKA procedure for the macro base station 5-1 (e.g. as shown in FIGS. 9 to 11, respectively), in which appropriate security parameters are passed to and / or derived in the pico base stations 5-2, 5-3 during the security procedures, separate AKA procedures are performed for the macro base station 5-1 and the pico base stations 5-2, 5-3.

[0146] As shown in Figure 13, the procedure involves an AS security procedure being performed for communication between the macro base station 5-1 and the mobile communication device 3 at S1313. During this procedure, the mobile communication device 3, the macro base station 5-1 and the MME 112 each generate and maintain their own security context for C-plane signalling between the macro base station 5-1 and the mobile communication device 3 at S1312-1, S1312-2, S1312-3. The creation of each security context involves the use of an appropriate macro / C-plane specific security key (e.g. K RRCint , K RRCenc This includes the derivation of

[0147] The procedure also involves AS security procedures being performed in S1314 for communication between the pico base stations 5-2, 5-3 and the mobile communication device 3. During this procedure, the mobile communication device 3, the pico base stations 5-2, 5-3 and the MME 112 each generate and maintain their own security context for U-plane signalling between the pico base stations 5-2, 5-3 and the mobile communication device 3 in S1316-1, S1316-2, S1316-3. The creation of each security context involves the use of appropriate pico / U-plane specific security keys (e.g. K UPenc This includes the derivation of

[0148] The steps of S1313 and S1314 may be performed sequentially in any suitable order, or simultaneously.

[0149] It can therefore be seen that as a result of the procedure in Figure 13, the MME 112 and the mobile communication device 3 each maintain two ongoing security contexts. To support the existence of two ongoing security contexts, the handover signalling (for handover from macro+pico to another macro+pico) is modified in this example to allow for the exchange of two security contexts. For example, the signalling is modified to include (each K eNB Based on the two K eNB *, to signal different security algorithms (if different algorithms are used), and to signal other general information associated with the two different security contexts.

[0150] Additionally, the RRC and NAS messages are appropriately modified to support the dual AKA procedure of Figure 13. For example, the RRC security mode command is modified to include information identifying the security algorithms per AKA procedure, and the NAS security messages are modified to include duplication of security parameters as necessary.

[0151] The mobile communication device 3 holds two encryption instances (e.g., at the PDCP layer), each with its own set of security keys, one key for control plane encryption and one key for user plane encryption.

[0152] It will be appreciated that a similar procedure can be applied, if necessary, to generate separate NAS contexts for the pico and macro base station AKA procedures being performed, which is similar to the procedure described with reference to Figures 9 to 12, but during this procedure the mobile communication device 3 and the MME 112 will generate and maintain a NAS security context for the macro base station 5-1 and separate NAS security contexts for the pico base stations 5-2, 5-3, respectively. The generation and transmission of the NAS security contexts may include the derivation and transmission of duplicate security parameters (one copy per context), if necessary.

[0153] Key change in progress procedure Regardless of which of the above procedures is implemented, in order to avoid potential security issues associated with PDCP COUNT rollover, the pico base stations 5-2, 5-3 may determine when a PDCP COUNT rollover has occurred or is about to occur by using K UPencAn information element indicating that the UPenc In response to receiving this message, the macro base station 5-1 may initiate an inter-cell handover, ultimately resulting in a new pico / macro cell pair, but with a different K key for user plane encryption. UPenc The communication will continue using the value.

[0154] Similarly, K eNB If other security parameters such as are dynamically changed and given to the macro base station 5-1 by the MME 112 (according to the current procedure), when the procedure shown in FIG. 10 is performed, the macro base station 5-1 will eNB 11 is implemented, the macro base station 5-1 is configured to forward the new K UPenc When the procedure shown in FIG. 12 is performed, the macro base station 5-1 is configured to forward the new K eNB * 9 is implemented, the MME 112 forwards the new K eNB to the pico base stations 5-2 and 5-3.

[0155] Modifications and Alternatives Detailed embodiments have been described above. As those skilled in the art will appreciate, several modifications and alternatives to the above embodiments and variations can be made while still benefiting from the invention embodied herein.

[0156] In the above embodiment, one macrocell 7 and two picocells 10 are described. The picocells are operated using component carriers having the same frequency band (F2) and the macrocell is operated using a component carrier having a different frequency band (F1). It will be appreciated that in a deployed system there may be any number of picocells, each of which may be operated on a component carrier having a different respective frequency band, potentially even on a component carrier having the same frequency band as the macrocell.

[0157] In the above embodiments, the macro and pico base stations may have the same security capabilities, however, if different security capabilities are supported, the mobile communication device is informed of the appropriate capabilities for each base station (e.g. in the "RRC Security Mode Command" or other similar message) so that the mobile communication device can use the correct algorithms.

[0158] In the above embodiment, the ciphering key is forwarded from the macro base station or derived by the pico base station based on security information received from either the MME or the macro base station. It will be appreciated that other parameters required for U-plane ciphering / deciphering may be derived as follows: COUNT may be maintained at PDCP level by the pico base station; BEARER identity may be forwarded from the macro base station or selected by the pico base station; DIRECTION may be set in either the macro base station or the pico base station. For example, appropriate synchronization may be provided between the macro base station and the pico base station to ensure that the correct bearer identity is known in both the macro base station and the pico base station. If both base stations have the information and capability to determine a particular parameter (e.g., "DIRECTION"), only one base station will make the decision and this will be signaled to the other base station.

[0159] The detailed description given for the embodiment of Figures 9-12 relates to the procedure for initial connection establishment. It will be appreciated that a similar approach can be used when the decision to split the U-plane and C-plane is made at a later stage. For example, if a mobile communication device is involved in one type of user plane communication provided by a macro cell (e.g., Voice over IP "VoIP") and then starts a different form of user plane communication provided by a pico cell (e.g., a web browsing session), it may be necessary to initiate a C-plane / U-plane split. In this case, an S1 UE context modification (with corresponding response) may be used to provide the pico base station with appropriate security information (similar to the process of Figure 9). Similarly, a new X2 message (with corresponding response) may be provided (e.g., an X2-AP context modification message) (similar to any of the processes of Figures 10-12). Furthermore, the RRC signaling used to provide the mobile communication device with appropriate security information (if security parameters have changed) and / or an indication that a split has occurred may be a message such as an RRC reconfiguration message (with corresponding response).

[0160] Although specific new X2-AP messages (X2-AP Context Setup and X2-AP Context Setup Response) have been described, it will be appreciated that any suitable X2-AP messages may be used, including re-use of existing messages with the addition of appropriate information elements. Let's do it.

[0161] Furthermore, K eNB Although such information is shown as being exchanged over the X2 interface between the pico base station and the macro base station, it will be appreciated that the interface between the base stations may be a new dedicated interface (e.g., an “X3” interface).

[0162] Although the RRC security mode command message has been described as including information indicating that the U-plane and C-plane are split (e.g., in the form of a dedicated information element (IE), a modified IE, or reuse of an existing IE), the indication that the U-plane and C-plane are split may also be communicated to the mobile communication device in a NAS message, such as a NAS security mode command message (alternatively or in addition).

[0163] Information elements contained in such messages typically include, for example: · Security key IE for messages from macro base station to pico base station (can be used in the procedures of Figs. 10 to 13 or for key change in progress procedures). This can be the KeNB or the next hop (NH). In the embodiment of FIG. 10, for example, it is macro K eNB It can be said that: In the embodiment of FIG. 12, it is the macro K eNB * It can be said that: ° In the case of dual AKA in Figure 13, it is a new AKA for Pico K eNB It can be said that: UE security capabilities IE for messages from macro base station to pico base station (e.g., indicating a change in security capabilities) · Kupenc key change IE for a message from a pico base station to a macro base station (indicating that an intra-cell handover procedure is required when the PDCP COUNT rollover occurs)

[0164] When referring to the timing diagrams, it will be understood that in many cases message transmissions need not follow the specific order shown, but can follow any logical order.

[0165] 9, by way of example, the S1-AP messages sent to the pico and macro base stations to initiate the AS security context setup (S934, S936) and the resulting U-plane and C-plane key derivation (S938, S940) are shown to occur in a particular order (for clarity of illustration), but those skilled in the art will appreciate that the messages may occur in any suitable order or simultaneously, as appropriate. Specifically, for example, the initiation of security context initialization and key derivation at the pico base stations 5-2, 5-3 (S934, S938) may occur generally before, generally after, or substantially simultaneously with the corresponding initiation of security context initialization and key derivation at the macro base station 5-1 (S936, S940). Similarly, the associated S1-AP response message may be sent at any suitable time after successful security context initialization.

[0166] Additionally, although in FIG. 9 a copy of only one S1-AP message (S1-AP Initial Context Setup) is shown being sent to the pico base station to provide the appropriate security parameters, it will be appreciated that a copy of any appropriate S1-AP message carrying security parameters may be provided to the pico base station including, for example, a UE context modification message, etc.

[0167] It will be appreciated that in relation to the dual AKA procedure described with reference to Figure 13, there may also be scenarios where a pico base station is not an E-UTRAN base station but instead connects to a non-EUTRAN or even non-3GPP network. In this case, the non-3GPP network may perform its own security procedures for the user plane, while the macro base station still performs 3GPP security procedures, resulting in a non-3GPP security context for the user plane and a 3GPP security context for the control plane.

[0168] Although the communications system 1 has been described with respect to base stations 5 operating as macro or pico base stations, it will be appreciated that the same principles may be applied to base stations operating as femto base stations, relay nodes providing elements of base station functionality, or other such communications nodes.

[0169] In the above embodiment, a mobile telephone-based communication system is described. As will be appreciated by those skilled in the art, the signaling techniques described in this application can be used in other communication systems. Other communication nodes or devices can include user devices such as, for example, personal digital assistants, laptop computers, web browsers, etc. As will be appreciated by those skilled in the art, it is not essential that the relay system described above is used for mobile communication devices. The system can be used to extend the coverage of a base station in a network having one or more fixed computing devices together with or instead of mobile communication devices.

[0170] In the above embodiments, the base station 5 and the mobile communication device 3 each comprise a transceiver circuit. Typically, this circuit is formed by a dedicated hardware circuit. However, in some embodiments, part of the transceiver circuit can be implemented as software executed by a corresponding controller.

[0171] In the above embodiment, a number of software modules are described. As will be appreciated by those skilled in the art, the software modules may be provided in compiled or uncompiled form and may be provided to the base station or relay station as a signal over a computer network or on a recording medium. Furthermore, the functions performed by some or all of this software may be performed using one or more dedicated hardware circuits.

[0172] Various other modifications will be apparent to those skilled in the art and will not be described in further detail herein.

[0173] This application claims priority to UK Patent Application No. 1300884.2, filed January 17, 2013, the disclosure of which is incorporated herein in its entirety.

Claims

1. A user equipment configured for a connection involving simultaneous connection with a first communication device and a second communication device, comprising: means for deriving a security key for the first communication device; means for deriving at least one control plane security key for control plane communications between the user equipment and the first communication device using the derived security key of the first communication device; means for deriving a security key for the second communication device using the derived security key of the first communication device during the establishment of the connection; means for deriving user plane security keys using the security keys of the second communication device; and means for using the derived user plane security key for user plane communications between the user equipment and the second communication device. User equipment.

2. The security key and the user plane security key of the second communication device are derived after receiving a first RRC message from the first communication device; The user device further comprises: means for transmitting a second RRC message to the first communication device in response to receiving the first RRC message. The user device of claim 1. The user plane security key is derived based on the first RRC message from the first communication device.

3. A user device according to claim 2.

4. The first communication device provides a first communication cell; the second communication device providing a second communication cell; A user equipment according to any one of claims 1 to 3.

5. The second communication cell is located within the first communication cell. A user device according to claim 4.

6. The method further comprises: means for transmitting to or receiving from the second communication device user plane signaling protected using the derived user plane security key. A user equipment according to any one of claims 1 to 5.

7. The control plane communications and the user plane communications are separated. A user device according to claim 6.

8. A method performed by a user equipment configured for a connection involving simultaneous connection with a first communication device and a second communication device, comprising: deriving a security key for the first communication device; deriving at least one control plane security key for control plane communications between the user equipment and the first communications device using the derived security keys of the first communications device; deriving a security key for the second communication device using the derived security key of the first communication device during establishing the connection; deriving user plane security keys using the security keys of the second communication device; and using the derived user plane security key for user plane communications between the user equipment and the second communication device. method.

9. The method of claim 8, wherein the security key and the user plane security key of the second communication device are derived after receiving a first RRC message from the first communication device; The method further comprises: transmitting a second RRC message to the first communication device in response to receiving the first RRC message. The method according to claim 8.

10. The method of claim 1, wherein the user plane security key is derived based on the first RRC message from the first communication device.

10. The method of claim 9.

11. The first communication device, comprising: the second communication device providing a second communication cell; 11. The method according to any one of claims 8 to 10.

12. The second communication cell is located within the first communication cell. The method of claim 11.

13. The method of claim 12, further comprising transmitting user plane signaling to or receiving from the second communication device, the user plane signaling being protected using the derived user plane security key.

13. A method according to any one of claims 8 to 12.

14. The control plane communications and the user plane communications are separated. The method of claim 13.

Images