JP4653231B2 - Mobile communication method - Google Patents

Description

  The present invention relates to a mobile communication method for performing communication between a mobile station and a radio base station using a predetermined key.

  Conventionally, an LTE (Long Term Evolution) type mobile communication system defined by 3GPP is configured to perform communication between a mobile station UE and a radio base station eNB using a predetermined key.

As the predetermined key, for example, a key K _{RRC_Ciph} used in “Ciphering” in the RRC protocol that is a C plane protocol (Access Stratum, AS) between the mobile station UE and the radio base station eNB, or “Integrity” in the RRC protocol. Key K _{RRC_IP} used in “Protection” and key K _{UP_Ciph} used in “Ciphering” in the U plane between the mobile station UE and the radio base station eNB (Access Stratum, AS). The predetermined key is generated using the first key K _eNB .

If such a predetermined key or the first key K _eNB is used for a long time, it is not preferable because the system becomes weak for security. Therefore, a procedure for updating the predetermined key and the first key K _eNB when a handover is performed is devised in 3GPP.

Here, with reference to FIG. 12, in the handover procedure of the mobile station UE, an operation in which the handover destination radio base station (Target eNB) obtains the first key K _eNB ^** used for generating a predetermined key will be described.

As shown in FIG. 12, first, the handover source radio base station (Source eNB) stores the first key K _eNB , the parameter “Next Hop”, and the parameter “Handover Type” indicating the type of handover. And an intermediate key K _eNB ^* is generated based on the parameter “Target PCI” indicating the identification information of the handover destination cell.

Second, the handover source radio base station (Source eNB) transmits the generated intermediate key K _eNB ^* to the handover destination radio base station (Target eNB).

Third, based on the received intermediate key K _eNB ^* and the “C-RNTI (Cell Radio Network Temporary ID)” assigned by the handover destination cell, the handover destination radio base station (Target eNB) A first key K _eNB ^** used to generate a predetermined key is generated in a radio base station (Target eNB).

3GPP TS33.401 v8.0.0

However, as described above, in the handover procedure of the conventional mobile communication system, handover is performed using a plurality of parameters and functions in both the handover source radio base station (Source eNB) and the handover destination radio base station (Target eNB). There has been a problem that the first key K _eNB ^** used in the destination radio base station (Target eNB) has to be generated.

In particular, the handover source radio base station (Source eNB) and the handover destination radio base station (Target eNB) must use a K _eNB conversion function (Key Derivation Function, KDF) using different parameters, and the mobile station UE However, it is necessary to equip these KDFs, and there is a complicated problem.

In addition, there is a need to update K _eNB according to PCI (Physical Cell ID) of the handover destination radio base station.

Furthermore, since it is necessary to update the _KeNB according to the C-RNTI, there is a restriction in flexibly performing the change allocation of the C-RNTI.

  Therefore, the present invention has been made in view of the above problems, and a mobile communication method capable of generating a first key used in a handover destination radio base station (Target eNB) with a simplified procedure. The purpose is to provide.

  A first feature of the present invention is a mobile communication method for performing communication between a mobile station and a radio base station using a predetermined key. In the handover procedure of the mobile station, the handover destination radio base station A first key for generating a predetermined key used for communication with the station and a first key for generating a predetermined key used for communication between the next handover destination radio base station and the mobile station. The gist is to acquire both.

  As described above, according to the present invention, it is possible to provide a mobile communication method capable of generating a first key used in a handover destination radio base station (Target eNB) with a simplified procedure.

1 is an overall configuration diagram of a mobile communication system according to a first embodiment of the present invention. It is a figure which shows an example of the key hierarchy used in the mobile communication system which concerns on the 1st Embodiment of this invention, and a calculation procedure. It is a sequence diagram which shows the initial setting procedure in the mobile communication system which concerns on the 1st Embodiment of this invention. FIG. 3 is a sequence diagram showing an X2 handover procedure in the mobile communication system according to the first embodiment of the present invention. FIG. 3 is a sequence diagram showing an S1 handover procedure in the mobile communication system according to the first embodiment of the present invention. FIG. 3 is a sequence diagram showing an Intra-eNB handover procedure in the mobile communication system according to the first embodiment of the present invention. It is a sequence diagram which shows the S1 handover procedure in the mobile communication system which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the hierarchical structure and calculation procedure of a key used with the mobile communication system which concerns on the 3rd Embodiment of this invention. It is a sequence diagram which shows the X2 handover procedure in the mobile communication system which concerns on the 2nd Embodiment of this invention. It is a sequence diagram which shows the S1 handover procedure in the mobile communication system which concerns on the 3rd Embodiment of this invention. FIG. 3 is a sequence diagram showing an Intra-eNB handover procedure in the mobile communication system according to the first embodiment of the present invention. It is a figure which shows an example of the calculation procedure of the key used with the mobile communication system concerning a prior art.

(Mobile communication system according to the first embodiment of the present invention)
With reference to FIG. 1 thru | or FIG. 6, the mobile communication system which concerns on the 1st Embodiment of this invention is demonstrated.

  The mobile communication system according to the present embodiment is a mobile communication system to which the LTE scheme is applied. As shown in FIG. 1, a plurality of switching stations MME # 1, # 2... And a plurality of radio base stations eNB # 11, # 12, # 21, # 22...

  For example, the mobile station UE is configured to communicate with the radio base station eNB # 11 using the predetermined key described above in the cell # 111 under the radio base station eNB # 11.

In the handover procedure of the mobile station UE, the handover destination radio base station (for example, the radio base station eNB # 12) is an intermediate key K _eNB generated by the handover source radio base station (for example, the radio base station eNB # 11). The first key K _eNB [n + 1], K _eNB [n + 2] and the like for generating a predetermined key used for communication with the mobile station UE is acquired without using ^* .

  FIG. 2 shows an example of the hierarchical structure and calculation procedure of keys used in the mobile communication system according to the present embodiment (that is, keys used for calculating a predetermined key).

As shown in FIG. 2, the key _{K RRC - IP} used for "Integrity Protection" in the RRC protocol, a key _{K UP_Ciph} used for "Ciphering" in the U-plane of the key _{K RRC - Ciph} and AS used for "Ciphering" in the RRC protocol, the It is generated using the first key K _{eNB [n]} .

Further, the first key K _{eNB [n]} is calculated by the following equation using the parent key K _ASME .

K _{eNB [0]} = KDF ₀ (K _ASME , NAS SN)
K _{eNB [n + 1]} = KDF ₁ (K _ASME , K _{eNB [n]} ), (n ≧ 0)
Here, the master key K _ASME is known only by the mobile station UE and the switching center MME, and should not be known by the radio base station eNB.

  The NAS SN is a sequence number (Sequence Number, SN) of a NAS protocol that is a C plane protocol between the mobile station UE and the switching center MME (Non Access Stratum, NAS).

  Hereinafter, the operation of the mobile communication system according to the present embodiment will be described with reference to FIGS. 3 to 6.

  First, with reference to FIG. 3, an initial setup procedure (Initial Establishment Procedure) in the mobile communication system according to the present embodiment will be described.

As shown in FIG. 3, in a stage before the start of the initial setting procedure, the mobile station UE holds K _ASME (step S101), and the radio base station eNB holds a key used for generating a predetermined key. However, the exchange MME holds K _ASME (step S103).

  In step S104, the mobile station UE transmits an “RRC Connection Request (RRC connection request signal)” to the radio base station eNB. In step S105, the radio base station eNB transmits “RRC Connection Request” to the mobile station UE. RRC Connection Setup (RRC connection setup signal) "is transmitted.

  In Step S106, the mobile station UE transmits, to the radio base station eNB, “NAS Service Request (NAS sequence number)” including “RRC Connection Setup Complete (RRC connection setup completion signal)” and “NAS SN (NAS sequence number)”. Service request signal) ".

  In step S107, the radio base station eNB transmits “S1 Initial UE Message” and “NAS Service Request (NAS service request signal)” including “NAS SN” to the switching center MME.

In step S108, the switching center MME calculates K _{eNB [0]} and K _{eNB [1] according} to the following equations.

K _{eNB [0]} = KDF ₀ (K _ASME , NAS SN)
K _{eNB [1]} = KDF ₁ (K _ASME , K _{eNB [0]} )
In step S109, the mobile switching center MME sends “S1 Initial UE Context Setup (initial UE context setup signal)” including K _{eNB [0]} , K _{eNB [1]} , and “NAS SN” to the radio base station eNB. Send. Further, “KI (= 0)” may be included in this message, but this is not essential.

  In step S110, the radio base station eNB transmits “RRC Security Mode Command (RRC security mode instruction signal)” including “NAS SN” to the mobile station UE.

In step S111, the mobile station UE calculates K _{eNB [0]} by the following equation.

K _{eNB [0]} = KDF ₀ (K _ASME , NAS SN)
Further, the mobile station _UE, based on _{K eNB [0], K RRC_IP} , K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

At this stage, the mobile station UE holds K _{eNB [0]} and “KI (= 0)” (step S114), and the radio base station eNB is configured to _receive K _{eNB [0]} , K _{eNB [1]} , “KI (= 0)” is held (step S113), and the exchange MME holds K _ASME , K _{eNB [1]} , and “KI (= 0)” (step S112).

  When “KI (= 0)” is not included in “S1 Initial UE Context Setup (initial UE context setup signal)” in step S109, the radio base station eNB automatically receives the message. “KI (= 0)” may be initialized.

The radio base station _eNB, based on _{K eNB [0], K RRC_IP} , K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  In step S115, the radio base station eNB transmits “RRC Connection Reconfiguration (RRC connection reconfiguration signal)” to the mobile station UE.

  In steps S116 and S117, the mobile station UE transmits “RRC Security Mode Command Complete (RRC security mode instruction completion signal)” and “RRC Connection Reconfiguration Complete (RRC connection reconfiguration completion signal)” to the radio base station eNB. Send.

  In step S118, the radio base station eNB transmits “S1 Initial UE Context Setup Complete (initial UE context setting completion signal)” to the switching center MME.

  With the above procedure, all the keys necessary for protection of communication (Integrity Protection and Ciphering) in the AS are obtained in the mobile station UE, the radio base station eNB, and the exchange MME.

  Secondly, with reference to FIG. 4, the X2 handover procedure (handover procedure between different radio base stations) in the mobile communication system according to the present embodiment will be described.

As shown in FIG. 4, in the stage before the start of the X2 handover procedure, the mobile station UE holds K _{eNB [n]} and “KI (= n)” (step S1001), and the handover source radio base station (Source eNB) holds K _{eNB [n]} , K _{eNB [n + 1]} , and “KI (= n)” (step S1002), and the switching center MME has K _ASME , K _{eNB [n + 1]} , “ KI (= n) "is held (step S1003).

  In step S1004, the mobile station UE transmits “RRC Measurement Report (measurement report signal)” to the handover source radio base station (Source eNB) when a predetermined condition is satisfied.

In step S1005, the handover source radio base station (Source eNB) performs “X2 HO Preparation (handover preparation) including K _{eNB [n + 1]} and“ KI (= n + 1) ”with respect to the handover destination radio base station (Target eNB). Signal) ".

In step S1006, the handover destination radio base station (Target eNB) stores the received K _{eNB [n + 1]} and “KI (= n + 1)”. In step S1007, the handover destination radio base station (Target eNB) , “X2 HO Preparation Ack (handover preparation response signal)” is transmitted.

The radio base station _eNB, based on _{K eNB [n + 1],} K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  In step S1008, the handover source radio base station (Source eNB) transmits “RRC HO Command (handover instruction signal)” to the mobile station UE.

In step S1009, the mobile station UE calculates K _{eNB [n + 1]} by the following equation, and in step S1010, stores K _{eNB [n + 1]} and “KI (= n + 1)”.

K _{eNB [n + 1]} = KDF ₁ (K _ASME , K _{eNB [n]} )
The mobile station _Ue, based on _{K eNB [n + 1],} K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  In step S1011, the mobile station UE transmits “RRC HO Complete (handover completion signal)” to the handover destination radio base station (Target eNB).

  In step S1012, the handover destination radio base station (Target eNB) transmits “S1 Path Switch (path switch signal)” including “KI (= n + 1)” to the switching center MME.

In step S1013, the switching center MME calculates K _{eNB [n + 2] according} to the following equation, and stores K _{eNB [n + 2]} and “KI (= n + 1)” in step S1014.

K _{eNB [n + 2]} = KDF ₁ (K _ASME , K _{eNB [n + 1]} )
In step S1015, the switching center MME sends “S1 Path Switch Ack (path switch response signal)” including K _{eNB [n + 2]} and “KI (= n + 1)” to the handover destination radio base station (Target eNB). Send.

In step S1016, the handover destination radio base station (Target eNB) stores K _{eNB [n + 1]} , K _{eNB [n + 2]} , and “KI (= n + 1)”.

Through the above procedure, the K _eNB and the predetermined key are updated at the time of X2 handover.

  Thirdly, with reference to FIG. 5, the S1 handover procedure (inter-exchange center handover procedure) in the mobile communication system according to the present embodiment will be described.

As shown in FIG. 5, in the stage before the start of the S1 handover procedure, the mobile station UE holds K _{eNB [n]} and “KI (= n)” (step S2001), and the handover source radio base station (Source eNB) holds K _{eNB [n]} , K _{eNB [n + 1]} , and “KI (= n)” (step S2002), and the exchange MME receives K _ASME , K _{eNB [n + 1]} , “ KI (= n) "is held (step S2003).

  In step S2004, the mobile station UE transmits “RRC Measurement Report (measurement report signal)” to the handover source radio base station (Source eNB) when a predetermined condition is satisfied.

In step S2005, the handover source radio base station (Source eNB) performs “S1 HO Required (handover request reception) including K _{eNB [n + 1]} and“ KI (= n + 1) ”with respect to the handover source switching center (Source MME). Signal) ".

In step S2006, the handover source switching center (Source MME) sends “Relocation Request (allocation request) including K _ASME , K _{eNB [n + 1]} ,“ KI (= n + 1) ”to the handover destination switching center (Target MME). Signal) ".

In step S2007, the handover destination switching center (Target MME) calculates K _{eNB [n + 2] according} to the following formula, and stores K _{eNB [n + 2]} and “KI (= n + 1)” in step S2008.

K _{eNB [n + 2]} = KDF ₁ (K _ASME , K _{eNB [n + 1]} )
In step S2009, the handover destination switching center (Target MME) includes, for the handover destination radio base station (Target eNB), “S1 including K _{eNB [n + 1]} , K _{eNB [n + 2]} ,“ KI (= n + 1) ”. HO Request (handover request signal) "is transmitted.

  In step S2010, the handover destination radio base station (Target eNB) transmits “S1 HO Request Ack (handover request response signal)” to the handover destination switching center (Target MME).

  In step S2011, the handover destination switching center (Target MME) transmits “Relocation Request Ack (allocation request response signal)” including “KI (= n + 1)” to the handover source switching center (Source MME).

  In step S2012, the handover source switching center (Source MME) sends “S1 HO Required Ack (handover request reception response signal)” including “KI (= n + 1)” to the handover source radio base station (Source eNB). Send.

  In step S2013, the handover source radio base station (Source eNB) transmits “RRC HO Command (handover instruction signal)” to the mobile station UE.

In step S2014, the mobile station UE calculates K _{eNB [n + 1]} by the following formula, and in step S2015, stores K _{eNB [n + 1]} and “KI (= n + 1)”.

K _{eNB [n + 1]} = KDF ₁ (K _ASME , K _{eNB [n]} )
Further, the mobile station _UE, based on _{K eNB [n + 1],} K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

At this stage, the handover target radio base station (Target eNB) holds K _{eNB [n + 1]} , K _{eNB [n + 2]} , and “KI (= n + 1)” (step S2016). The radio base station _eNB, based on _{K eNB [n + 1],} K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  In step S2017, the mobile station UE transmits “RRC HO Complete (handover completion signal)” to the handover destination radio base station (Target eNB).

  In step S2018, the handover destination radio base station (Target eNB) transmits “S1 HO Complete (handover completion signal)” to the handover destination switching center (Target MME).

  In step S2019, the handover destination switching center (Target MME) transmits a “Relocation Complete (allocation completion signal)” to the handover source switching center (Source MME), and in step S2020, the handover source switching center (Source MME). ) Transmits “Relocation Complete Ack (allocation completion response signal)” to the handover destination switching center (Target MME).

Through the above procedure, the K _eNB and the predetermined key are updated at the S1 handover.

  In the S1 handover procedure, the operation performed by the mobile station UE is the same as the operation in the X2 handover procedure shown in FIG. The mobile station UE can perform both the X2 handover procedure and the S1 handover procedure based on the same process. That is, the mobile station UE can perform handover without having to be aware of whether the handover type is “X2 handover” or “S1 handover”.

  Fourthly, an intra-eNB handover procedure (intra-radio base station handover procedure) in the mobile communication system according to the present embodiment will be described with reference to FIG.

As shown in FIG. 6, in the stage before the start of the Intra-eNB handover procedure, the mobile station UE holds K _{eNB [n]} and “KI (= n)” (step S4001), and the radio base station (Source eNB) holds K _{eNB [n]} , K _{eNB [n + 1]} , and “KI (= n)” (step S4002), and the switching center MME receives K _ASME , K _{eNB [n + 1]} , “ KI (= n) "is held (step S4003).

  In step S4004, the mobile station UE transmits “RRC Measurement Report (measurement report signal)” to the radio base station (Source eNB) when a predetermined condition is satisfied.

  In step S4005, the radio base station (Source eNB) transmits “RRC HO Command (handover instruction signal)” to the mobile station UE.

In step S4006, the mobile station UE calculates K _{eNB [n + 1]} by the following equation, and stores K _{eNB [n + 1]} and “KI (= n + 1)” in step S4007.

K _{eNB [n + 1]} = KDF ₁ (K _ASME , K _{eNB [n]} )
Further, the mobile station _UE, based on _{K eNB [n + 1],} K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

At this stage, the radio base station (Source eNB) holds K _{eNB [n + 1]} and “KI (= n + 1)” (step S4008). The radio base station _eNB, based on _{K eNB [n + 1],} K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  In step S4009, the mobile station UE transmits “RRC HO Complete (handover completion signal)” to the radio base station (Source eNB).

  In step S4010, the radio base station (Source eNB) transmits “S1 Path Switch (path switch signal)” including “KI (= n + 1)” to the switching center MME.

In step S4011, the switching center MME calculates K _{eNB [n + 2] according} to the following equation, and stores K _ASME , K _{eNB [n + 2]} , and “KI (= n + 1)” in step S4012.

K _{eNB [n + 2]} = KDF ₁ (K _ASME , K _{eNB [n + 1]} )
In step S4013, the switching center MME transmits “S1 Path Switch Ack (path switch response signal)” including K _{eNB [n + 2]} and “KI (= n + 1)” to the radio base station (Source eNB). .

In step S4014, the radio base station (Source eNB) stores K _{eNB [n + 1]} , K _{eNB [n + 2]} , and “KI (= n + 1)”. At this stage, the mobile station UE holds K _{eNB [n + 1]} and “KI (= n + 1)” (step S4015).

Through the above procedure, the K _eNB and the predetermined key are updated at the time of intra-eNB handover.

  Further, in the intra-eNB handover procedure, the operation performed by the mobile station UE is the same as the operation in the X2 handover procedure shown in FIG. 2 and the operation in the S1 handover procedure shown in FIG. The mobile station UE can perform all of the X2 handover procedure, the S1 handover procedure, and the Intra-eNB handover procedure based on the same process. That is, the mobile station UE can perform handover without having to be aware of whether the handover type is “X2 handover”, “S1 handover”, or “Intra-eNB handover”.

(Operations and effects of the mobile communication system according to the first embodiment of the present invention)
According to the mobile communication system according to the first embodiment of the present invention, K _{eNB [n + 1] and the} like used in the handover destination radio base station (Target eNB) can be generated by a simplified procedure.

  Further, according to the mobile communication system according to the first embodiment of the present invention, the operation of the mobile station UE during the handover procedure is changed regardless of the type of handover (X2 handover, S1 handover, Intra-eNB handover). There is no need.

(Mobile communication system according to the second embodiment of the present invention)
With reference to FIG. 7, the mobile communication system according to the second embodiment of the present invention will be described while focusing on the differences from the mobile communication system according to the first embodiment described above.

  Specifically, with reference to FIG. 7, the S1 handover procedure (inter-exchange center handover procedure) in the mobile communication system according to the present embodiment will be described.

  As shown in FIG. 7, the operations in steps S3001 to S3006 are the same as the operations in steps S2001 to S2006 shown in FIG.

In step S3007, the handover destination switching center (Target MME) calculates K _{eNB [n + 3] according} to the following equation, and stores K _{eNB [n + 3]} and “KI (= n + 2)” in step S3008.

K _{eNB [n + 2]} = KDF ₁ (K _ASME , K _{eNB [n + 1]} )
K _{eNB [n + 3]} = KDF ₁ (K _ASME , K _{eNB [n + 2]} )
In step S3009, the handover destination switching center (Target MME) includes, for the handover destination radio base station (Target eNB), “S1 including K _{eNB [n + 2]} , K _{eNB [n + 3]} , and“ KI (= n + 2) ”. HO Request (handover request signal) "is transmitted.

  In step S3010, the handover destination radio base station (Target eNB) transmits “S1 HO Request Ack (handover request response signal)” to the handover destination switching center (Target MME).

  In step S3011, the handover destination switching center (Target MME) transmits “Relocation Request Ack (allocation request response signal)” including “KI (= n + 2)” to the handover source switching center (Source MME).

  In step S3012, the handover source switching center (Source MME) sends “S1 HO Required Ack (handover request reception response signal)” including “KI (= n + 2)” to the handover source radio base station (Source eNB). Send.

  In step S3013, the handover source radio base station (Source eNB) transmits “RRC HO Command (handover instruction signal)” to the mobile station UE. This message may include information indicating “KI (= n + 2)”.

In step S3014, the mobile station UE calculates K _{eNB [n + 2] according} to the following equation, and in step S3015, stores K _{eNB [n + 2]} and “KI (= n + 2)”.

K _{eNB [n + 1]} = KDF ₁ (K _ASME , K _{eNB [n]} )
K _{eNB [n + 2]} = KDF ₁ (K _ASME , K _{eNB [n + 1]} )
Further, the mobile station _UE, based on _{K eNB [n + 2],} K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

At this stage, the handover target radio base station (Target eNB) holds K _{eNB [n + 2]} , K _{eNB [n + 3]} , and “KI (= n + 2)” (step S3016). The radio base station _eNB, based on _{K eNB [n + 2],} K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  Hereinafter, operations in steps S3017 to S3020 are the same as those in steps S3017 to S2020 shown in FIG.

By this procedure, the predetermined key and K _eNB used for AS communication in the handover destination radio base station (Target eNB) cannot be known in the handover source radio base station (Source eNB), and the security of the system is improved.

(Mobile communication system according to the third embodiment of the present invention)
With reference to FIG. 8 to FIG. 11, a mobile communication system according to a third embodiment of the present invention will be described focusing on differences from the above-described mobile communication system according to the first embodiment.

  FIG. 8 shows an example of a hierarchical structure and calculation procedure of keys used in the mobile communication system according to the present embodiment (that is, keys used for calculating a predetermined key).

As shown in FIG. 8, a key _{K RRC - IP} used for "Integrity Protection" in the RRC protocol, a key _{K UP_Ciph} used for "Ciphering" in the U-plane of the key _{K RRC - Ciph} and AS used for "Ciphering" in the RRC protocol, the K _{eNB [n] [m]} .

K _{eNB [n] [m]} is calculated by the following equation using K _{eNB [n]} .

K _{eNB [n] [0]} = K _{eNB [n]}
K _{eNB [n] [m + 1]} = KDF ₂ (K _{eNB [n] [m]} ), (m ≧ 0)
Furthermore, K _{eNB [n]} is calculated by the following equation using K _ASME .

K _{eNB [0]} = KDF ₀ (K _ASME , NAS SN)
K _{eNB [n + 1]} = KDF ₁ (K _ASME , K _{eNB [n]} ), (n ≧ 0)
Hereinafter, the operation of the mobile communication system according to the present embodiment will be described with reference to FIGS. 9 to 11.

  First, with reference to FIG. 9, the X2 handover procedure (handover procedure between different radio base stations) in the mobile communication system according to the present embodiment will be described.

As shown in FIG. 9, in the stage before the start of the X2 handover procedure, the mobile station UE performs K _{eNB [n]} , K _{eNB [n] [m]} , “KI (= n)”, “RC (= m ) ”(Step S6001), and the handover source radio base station (Source eNB) is K _{eNB [n]} , K _{eNB [n + 1]} , K _{eNB [n] [m]} ,“ KI (= n) ”And“ RC (= m) ”(step S6002), and the exchange MME holds K _ASME , K _{eNB [n + 1]} , and“ KI (= n) ”(step S6003).

  In step S6004, when a predetermined condition is satisfied, the mobile station UE transmits “RRC Measurement Report (measurement report signal)” to the handover source radio base station (Source eNB).

In step S6005, the handover source radio base station (Source eNB) performs “X2 HO Preparation (handover preparation) including K _{eNB [n + 1]} and“ KI (= n + 1) ”with respect to the handover destination radio base station (Target eNB). Signal) ".

In Steps S6006 and S6007, the handover destination radio base station (Target eNB) performs K _{eNB [n + 1]} , K _{eNB [n + 1] [0]} , “KI (= n + 1)”, and “RC (= 0)”. Remember. Here, it is assumed that K _{eNB [n + 1] [0]} = K _{eNB [n + 1]} .

  In step S6008, the handover destination radio base station (Target eNB) transmits “X2 HO Preparation Ack (handover preparation response signal)” to the handover source radio base station (Source eNB).

  In step S6009, the handover source radio base station (Source eNB) sends “RRC HO Command (handover instruction signal)” including “KI (= n + 1)” and “RC (= 0)” to the mobile station UE. Send.

In step S6010, the mobile station UE calculates K _{eNB [n + 1]} and K _{eNB [n + 1] [0] according} to the following _equations , and in step S1010, the K _{eNB [n + 1]} and K _{eNB [n + 1] [0]} , “KI (= n + 1)”, “RC (= 0)”.

K _{eNB [n + 1]} = KDF ₁ (K _ASME , K _{eNB [n]} )
K _{eNB [n + 1] [0]} = K _{eNB [n + 1]}
Further, the mobile station _UE, based on _{K eNB [n + 1] [} 0], K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  Hereinafter, operations in steps S6012 to S6017 are the same as those in steps SS1011 to S1016 shown in FIG.

  Secondly, with reference to FIG. 10, the S1 handover procedure (inter-exchange center handover procedure) in the mobile communication system according to the present embodiment will be described.

As shown in FIG. 10, in the stage before the start of the S1 handover procedure, the mobile station UE performs K _{eNB [n]} , K _{eNB [n] [m]} , “KI (= n)”, “RC (= m ) ”(Step S7001), and the handover source radio base station (Source eNB) includes K _{eNB [n]} , K _{eNB [n + 1]} , K _{eNB [n] [m]} ,“ KI (= n) ”And“ RC (= m) ”(step S7002), and the exchange MME holds K _ASME , K _{eNB [n + 1]} , and“ KI (= n) ”(step S7003).

  Hereinafter, operations in steps S7004 to S7012 are the same as those in steps S2004 to S2012 shown in FIG.

  In step S7013, the handover source radio base station (Source eNB) sends “RRC HO Command (handover instruction signal)” including “KI (= n + 1)” and “RC (= 0)” to the mobile station UE. Send.

Here, in step S7014, the handover destination radio base station (Target eNB) calculates and stores K _{eNB [n + 1] [0] according} to the following equation.

K _{eNB [n + 1] [0]} = K _{eNB [n + 1]}
At this stage, the handover target radio base station (Target eNB) is configured as K _{eNB [n + 1]} , K _{eNB [n + 2]} , K _{eNB [n + 1] [0]} , “KI (= n + 1)”, “RC (= 0). "Is stored (step S7015). The radio base station _eNB, based on _{K eNB [n + 1] [} 0], K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

In step S7016, the mobile station UE calculates K _{eNB [n + 1]} and K _{eNB [n + 1] [0] according} to the following equations, and in step S7017, the K _{eNB [n + 1]} and K _{eNB [n + 1] [0]} , “KI (= n + 1)”, “RC (= 0)”.

K _{eNB [n + 1]} = KDF ₁ (K _ASME , K _{eNB [n]} )
K _{eNB [n + 1] [0]} = K _{eNB [n + 1]}
Further, the mobile station _UE, based on _{K eNB [n + 1] [} 0], K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  Hereinafter, the operations in steps S7018 through S7021 are the same as the operations in steps S2017 through S2020 shown in FIG.

  Thirdly, an intra-eNB handover procedure (intra-radio base station handover procedure) in the mobile communication system according to the present embodiment will be described with reference to FIG.

As shown in FIG. 11, in the stage before the start of the Intra-eNB handover procedure, the mobile station UE _transmits K _{eNB [n]} , K _{eNB [n] [m]} , “KI (= n)”, “RC ( = M) "(step S5001), and the radio base station (Source eNB) is K _{eNB [n]} , K _{eNB [n + 1]} , K _{eNB [n] [m]} ," KI (= n) ”And“ RC (= m) ”(step S5002), and the exchange MME holds K _ASME , K _{eNB [n + 1]} , and“ KI (= n) ”(step S5003).

  In step S5004, when a predetermined condition is satisfied, the mobile station UE transmits “RRC Measurement Report (measurement report signal)” to the radio base station (Source eNB).

  In step S5005, the radio base station (Source eNB) transmits “RRC HO Command (handover instruction signal)” including “KI (= n)” and “RC (= m + 1)” to the mobile station UE. .

In step S5006, the radio base station (Source eNB) calculates K _{eNB [n] [m + 1]} by the following equation, and in step S5007, K _{eNB [n]} , K _{eNB [n + 1]} , K _{eNB [n ] [M + 1]} , “KI (= n + 1)”, “RC (= m + 1)”.

K _{eNB [n] [m + 1]} = KDF ₂ (K _{eNB [n] [m]} )
The radio base station _eNB, based on _{K eNB [n] [m +} 1], K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

Similarly, in step S5008, the mobile station UE calculates K _{eNB [n] [m + 1]} by the following equation, and in step S5009, K _{eNB [n]} , K _{eNB [n] [m + 1]} , “KI”. (= N + 1) ”and“ RC (= m + 1) ”are stored.

K _{eNB [n] [m + 1]} = KDF ₂ (K _{eNB [n] [m]} )
Further, the mobile station _UE, based on _{K eNB [n] [m +} 1], K RRC_IP, K RRC_Ciph, calculates _{K UP_Ciph,} applied to subsequent AS communications.

  In step S5010, the mobile station UE transmits “RRC HO Complete (handover completion signal)” to the radio base station (Source eNB).

  According to the present embodiment, “Path Switch” in the Intra-eNB handover procedure can be omitted.

Above, as shown in FIGS. 9 to 11, by introducing the update of K _eNB of the wireless base station according to the parameter "RC", while omitting an inquiry to the switching center MME, it can update the K _eNB.

  In the procedure of FIGS. 9 to 11, the parameter “RC” may be omitted from the “RRC HO Command (handover instruction signal)”.

  When the parameter “RC” is omitted without being included in the “RRC HO Command (handover instruction signal)”, it is determined whether or not “RC” should be incremented based on whether or not the parameter “KI” is incremented. it can.

  When “KI” is incremented, “RC” is reset to “0”, and when “KI” is not incremented, “RC” may be incremented.

  Alternatively, when the parameter “RC” is omitted without being included in the “RRC HO Command (handover instruction signal)”, the mobile station UE keeps the value of “RC” as it is and increases it from the current value. It may be possible to autonomously determine which case is correct by trying each case when resetting to “0” and checking “Integrity” for the received message.

(Example of change)
Note that the operations of the exchange MME, the radio base station eNB, and the mobile station UE described above may be implemented by hardware, may be implemented by a software module executed by a processor, or may be implemented by a combination of both. May be.

  The software module includes a RAM (Random Access Memory), a flash memory, a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electronically Erasable and Programmable ROM, a hard disk, a registerable ROM, a hard disk). Alternatively, it may be provided in a storage medium of an arbitrary format such as a CD-ROM.

  Such a storage medium is connected to the processor so that the processor can read and write information from and to the storage medium. Further, such a storage medium may be integrated in the processor. Such a storage medium and processor may be provided in the ASIC. Such an ASIC may be provided in the exchange MME, the radio base station eNB, or the mobile station UE. Further, the storage medium and the processor may be provided as a discrete component in the exchange MME, the radio base station eNB, or the mobile station UE.

  Although the present invention has been described in detail using the above-described embodiment, it is obvious for those skilled in the art that the present invention is not limited to the embodiment described in the present specification. The present invention can be implemented as modified and changed modes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Accordingly, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

MME ... Switching station eNB ... Radio base station UE ... Mobile station

Claims (2)

A mobile communication method in which a mobile station performs handover from a handover source radio base station to a handover destination radio base station using an interface via an exchange,
The handover destination radio base station acquires, from the exchange, a first key for generating a predetermined key used for communication between the handover destination radio base station and the mobile station;
When the mobile station receives a handover command signal from the handover source radio base station, the mobile station includes the first key used for communication with the handover source radio base station, which is included in the handover command signal Generating a first key for generating a predetermined key used for communication between the handover destination radio base station and the mobile station, based on a parameter obtained by incrementing a parameter used when generating A mobile communication method comprising: A mobile station that can be handed over from a handover source radio base station to a handover destination radio base station using an interface via an exchange,
When a handover instruction signal is received from the handover source radio base station, the parameter used to generate the first key used for communication with the handover source radio base station included in the handover instruction signal is incremented The mobile station is configured to generate a first key for generating a predetermined key used for communication with the handover destination radio base station based on the parameter obtained.

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