Mobile communication method and radio base station

The present invention relates to mobile communication methods and radio base stations.

With reference to FIG. 12, in the "LTE (Long Term Evolution)" type mobile communication system defined by 3GPP, the mobile station UE for which RRC connection # 1 is set in cell # 1 is RLF (wireless link). The operation when a failure (Radio Link Failure) is detected will be explained.

As shown in FIG. 12, RRC connection # 1 is set between the mobile station UE and the radio base station eNB # 1, and S1 connection # 1 is established between the radio base station eNB # 1 and the exchange MME. When the mobile station UE detects RLF (Radio Link Failure) in step S5001 in the set state, cell selection processing (Cell Selection) is performed in step S5002.

In step S5003, the mobile station UE transmits an RRC Connection Re-establishment Request to the radio base station eNB # 2 that manages the cell # 2 selected by the cell selection process.

The radio base station eNB # 2 is the context of the mobile station UE corresponding to "Physical Cell Identy", "C-RNTI" and "short MAC-I" included in the received "RRC Connection Re-establishment Request" in step S5004. When the information (UE context) is stored, "RRC Connection Re-establishment" is transmitted to the mobile station UE in step S5005.

In step S5006, the mobile station UE transmits "RRC Connection Re-establishment Complete" to the radio base station eNB # 2.

The radio base station eNB # 2 transmits "S1 Path Switch" to the switching station MME in step S5007, and transmits "RRC Connection Reconfiguration" to the mobile station UE in step S5008.

In step S5009, the mobile station UE transmits "RRC Connection Reconfiguration Complete" to the radio base station eNB # 2, and in step S5010, the switch station MME sends "S1" to the radio base station eNB # 2. Send "Path Switch Ack".

As a result, the switching of the RRC connection # 1 to the RRC connection # 2 and the switching of the S1 connection # 1 to the S1 connection # 2 are completed. Here, RRC connection # 2 is an RRC connection set between the mobile station UE and the radio base station eNB # 2, and S1 connection # 2 is a connection between the radio base station eNB # 2 and the exchange station MME. It is an S1 connection set between.<nplcit num="1"><text>3GPP TS36.331 v8.3.0</text></nplcit><nplcit num="2"><text>3GPP TS36.321 v8.3.0</text></nplcit>

<p> However, in such a mobile communication system, the mobile station UE is configured to be able to perform a handover only to a cell under the radio base station eNB that stores the context information (UE context) of the mobile station UE. There is.</p><p> Therefore, if the above-mentioned radio base station eNB # 2 does not store the context information of the mobile station UE, the above-mentioned "RRC Connection Re-establishment" is rejected, and the mobile station UE performs the cell selection process. There was a problem that RRC connection # 2 could not be set up with the radio base station eNB # 2 that manages cell # 2 selected by.</p><p> Therefore, the present invention has been made in view of the above-mentioned problems, and is a mobile communication method and a wireless base station that enable connection resetting (reconnection) to a wireless base station that does not store the context information of the mobile station. The purpose is to provide.</p>

<p> The first feature of the present invention is a mobile communication method, in which a mobile station for which a first connection is set in a first cell performs a cell selection process when a failure in the first connection is detected. A, the step B in which the mobile station transmits a connection reset request signal to the second cell selected by the cell selection process, and the radio base station that manages the second cell reset the connection. In the step C of determining whether or not the context information of the mobile station is stored in response to the request signal, and the radio base station that manages the second cell does not store the context information of the mobile station. When the determination is made, the step D of acquiring the context information of the mobile station from the radio base station that manages the first cell, and the radio base station that manages the second cell based on the context information of the mobile station. The gist is that the mobile station has a step E of setting a second connection in the second cell for the mobile station.</p><p> The second feature of the present invention is a radio base station that manages the second cell, and is a connection reset request signal addressed to the second cell received from a mobile station for which the first connection is set in the first cell. When it is determined by the determination unit that the determination unit is configured to determine whether or not the context information of the mobile station is stored, and the determination unit does not store the context information of the mobile station. In addition, the acquisition unit configured to acquire the context information of the mobile station from the radio base station that manages the first cell cooperates with the mobile station based on the context information of the mobile station. Therefore, it is a gist to include a setting unit configured to set a second connection in the second cell for the mobile station.</p>

<p> As described above, according to the present invention, it is possible to provide a mobile communication method and a wireless base station that enable connection resetting (reconnection) for a wireless base station that does not store the context information of the mobile station. ..</p>

(Structure of Mobile Communication System According to First Embodiment of the Present Invention) The configuration of the mobile communication system according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 7.

As shown in FIG. 1, the mobile communication system according to the present embodiment is an LTE mobile communication system, which includes an exchange station MME, a radio base station eNB # 1 that manages cell # 1, and cell # 2. It is equipped with a radio base station eNB # 2 to be managed.

In such a mobile communication system, the mobile station UE is configured to be able to perform a handover only to a cell under the radio base station eNB that stores the context information of the mobile station UE, that is, "Backward". "Handover" has been applied.

The present invention is applicable not only to the LTE mobile communication system but also to any mobile communication system to which the "Backward Handover" is applied.

As shown in FIG. 2, the radio base station eNB has a UE context storage unit 11, an RRC (Radio Resource Control) processing unit 12, a determination unit 13, a MAC (Media Access Control) processing unit 14, and an X2 processing unit. It includes 15 and an S1 processing unit 16. Hereinafter, the configuration of the radio base station eNB # 2 that manages the cell # 2 (second cell) will be described on behalf of the radio base station eNB.

The UE context storage unit 11 is configured to store the short MAC-I that can uniquely identify the mobile station UE and the context information of the mobile station UE in association with each other.

Here, "shortMAC-I" was generated using "VarShortMAC-Input" consisting of "cell ID", "PCI (Physical Cell ID)" and "C-RNTI" as shown in FIG. It is a 16-bit security parameter.

Specifically, "shortMAC-I" is a subordinate to "VarShortMAC-Input", which is a tampering check code "MAC-I" calculated using the security key and security algorithm currently used by the mobile station UE. It is an extract of 16 bits.

Further, the context information of the mobile station UE includes, for example, "AS-Context" including "ue-RadioAccessCapabilityInfo", "ue-SecurityCapabilityInfo", and "reestablishmentInfo" as shown in FIG.

The RRC processing unit 12 is configured to perform RRC processing in cooperation with the RRC function of the mobile station UE.

For example, the RRC processing unit 12 receives an "RRC Connection Re-establishment Request (connection reestablishment request signal)" or "RRC Connection Re-establishment Complete (connection)" from the mobile station UE to a subordinate cell (for example, cell # 2). It is configured to receive "RRC Connection Reconfiguration Complete" and "RRC Connection Reconfiguration Complete".

Further, the RRC processing unit 12 is configured to transmit "RRC Connection Re-establishment (connection reconfiguration signal)" and "RRC Connection Reconfiguration (connection reconfiguration signal)" to the mobile station UE.

The RRC processing unit 12 cooperates with the mobile station UE based on the context information of the mobile station UE, that is, by exchanging the above-mentioned RRC message with the mobile station UE, the mobile station UE It is configured to set RRC connection # 2 in cell # 2 for.

Here, FIG. 5 shows an example of the format of such RRC Connection Re-establishment Request.

The determination unit 13 is configured to determine whether or not the context information of the mobile station UE is stored in the UE context storage unit 11 in response to the "RRC Connection Re-establishment Request" received by the RRC processing unit 12. Has been done.

Specifically, the determination unit 13 stores the "Physical Cell Identity", "C-RNTI" and "C-RNTI" included in the "RRC Connection Re-establishment Request" received by the RRC processing unit 12 in the UE context storage unit 11. It is configured to determine whether or not the context information of the mobile station UE corresponding to "short MAC-I" is stored.

The MAC processing unit 12 is configured to perform MAC processing in cooperation with the MAC function of the mobile station UE.

The X2 processing unit 15 is configured to perform an interface function with another radio base station (for example, radio base station eNB # 1).

For example, when the determination unit 13 determines that the context information of the mobile station UE is not stored in the X2 processing unit 15, the context information of the mobile station UE is transmitted from the radio base station eNB # 1 that manages the cell # 1. Is configured to get.

Specifically, when the determination unit 13 determines that the context information of the mobile station UE is not stored, the X2 processing unit 15 sends a Forward HO Request (forward handover) to the radio base station eNB # 1. It is configured to acquire the context information of the mobile station UE via the "X2 HO Prepartion (handover preparation signal)" by transmitting the "request signal)".

Here, FIGS. 6 and 7 show an example of the format of such "X2 HO Prepartion".

The S1 processing unit 16 is configured to perform an interface function with the exchange MME. The S1 processing unit 16 is configured to manage the settings of the S1 connection with the exchange MME.

For example, the S1 processing unit 16 is configured to transmit "S1 Path Switch" to the exchange MME and receive "S1 Path Switch Ack" from the exchange MME.

(Operation of the mobile communication system according to the first embodiment of the present invention) The operation of the mobile communication system according to the first embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 8, RRC connection # 1 is set between the mobile station UE and the radio base station eNB # 1, and S1 connection # 1 is established between the radio base station eNB # 1 and the exchange MME. When the mobile station UE detects RLF (failure in RRC connection # 1) in step S1001 in the set state, cell selection processing is performed in step S1002.

For example, the mobile station UE detects an out-of-sync state in RRC connection # 1 N310 times, then activates the timer T310, and if the out-of-sync state is not resolved by the time the timer T310 expires, the RLF Is detected.

In step S1003, the mobile station UE transmits an RRC Connection Re-establishment Request to the radio base station eNB # 2 that manages the cell # 2 selected by the cell selection process.

The radio base station eNB # 2 is the context of the mobile station UE corresponding to "Physical Cell Identity", "C-RNTI" and "short MAC-I" included in the received "RRC Connection Re-establishment Request" in step S1004. If it is determined that the information is not stored, in step S1005, the radio base station eNB # 1 is specified based on the above-mentioned "Physical Cell Identity", and the above-mentioned "C" is given to the radio base station eNB # 1. -Send a "Forward HO Request" containing "RNTI" and "short MAC -I" (may be called by another name, such as "UE Context Request").

In step S1006, the radio base station eNB # 1 determines that the context information of the mobile station UE corresponding to "C-RNTI" and "short MAC-I" included in the received "Forward HO Request" is stored. In this case, in step S1007, "X2 HO Prepartion" including the context information of the mobile station UE is transmitted to the radio base station eNB # 2 (when it is determined that the context information of the mobile station UE is not stored). Send "Forward HO Reject" instead of "X2 HO Preparation").

In step S1008, the radio base station eNB # 2 transmits "RRC Connection Re-establishment" to the mobile station UE.

Here, when "Forward HO Reject" is returned from the radio base station eNB # 1, "RRC Connection Re-establishment Reject" is transmitted instead. As a result, the connection reset ends in failure, and the mobile station UE releases the RRC connection and enters the "RRC_IDLE state".

In step S1009, the mobile station UE transmits "RRC Connection Re-establishment Complete" to the radio base station eNB # 2.

The radio base station eNB # 2 transmits "X2 HO Prepartion Ack" to the radio base station eNB # 1 in step S1010, and transmits "S1 Path Switch" to the exchange MME in step S1011. Then, in step 1012, "RRC Connection Reconfiguration" is transmitted to the mobile station UE.

In step S1013, the mobile station UE transmits "RRC Connection Reconfiguration Complete" to the radio base station eNB # 2, and in step S1014, the switch station MME sends "S1" to the radio base station eNB # 2. Send "Path Switch Ack".

As a result, the switching of the RRC connection # 1 to the RRC connection # 2 and the switching of the S1 connection # 1 to the S1 connection # 2 are completed. Here, RRC connection # 2 is an RRC connection set between the mobile station UE and the radio base station eNB # 2, and S1 connection # 2 is a connection between the radio base station eNB # 2 and the exchange station MME. It is an S1 connection set between.

(Action / Effect of Mobile Communication System According to First Embodiment of the Present Invention) According to the mobile station UE used in the mobile communication system according to the first embodiment of the present invention, the radio base station eNB # 2 does not store the context information of the mobile station UE even when the radio base station eNB # 2 does not store the context information of the mobile station UE. Since the context information of the mobile station UE can be acquired from the station eNB # 1, the mobile station UE reconfigures (reconfigures) the connection to the radio base station eNB # 2 that does not store the context information of the mobile station UE. Can be connected).

(Modification 1 of the present invention) The mobile communication system according to the first modification of the present invention will be described with reference to FIGS. 9 to 11. Hereinafter, the mobile communication system according to the first modification will be described focusing on the differences from the mobile communication system according to the first embodiment described above.

In the mobile communication system according to the first modification, the mobile station UE transmits an "RRC Connection Re-establishment Request" to the radio base station eNB # 2 selected by the cell selection process using the random access procedure. It is configured to do.

Here, such an operation will be described with reference to FIGS. 9 and 10.

As shown in FIG. 9, in step S3001, the mobile station UE transmits a random access preamble to the radio base station eNB # 2.

In step S3002, the radio base station eNB # 2 transmits a random access response to the mobile station UE according to the received random access preamble. Here, the radio base station eNB # 2 transmits a random access response to the mobile station UE via the PDCCH including RA-RNTI.

In step S3003, the mobile station UE sends an "RRC Connection Re-establishment Request" using the uplink radio resource (UL Grant) specified by the random access response. HARQ (Hybrid ARQ) processing is applied to the transmission of such "RRC Connection Re-establishment Request".

In step S3004, the radio base station eNB # 2 transmits "Contention Resolution" in response to the reception of the "RRC Connection Re-establishment Request".

In step S3005, the radio base station eNB # 2 transmits "RRC Connection Re-establishment" which is a response signal to "RRC Connection Re-establishment Request". HARQ processing is applied to the transmission of such "RRC Connection Re-establishment".

The MAC processing unit 14 of the radio base station eNB # 2 is before the CR (Contention Resolution) timer (predetermined timer) that was started when the mobile station UE transmits the "RRC Connection Re-establishment Request" expires. , Is configured to send "Contention Resolution".

Here, as shown in FIG. 10A, the MAC processing unit 14 of the radio base station eNB # 2 sets "Contention Resolution" and "RRC Connection Re-establishment" in the same TTI (Transmission Time Interval). It may be concatenated and transmitted, or as shown in FIG. 10 (b), "Contention Resolution" and "RRC Connection Re-establishment" may be transmitted separately.

The MAC processing unit 14 of the radio base station eNB # 2 should copy the received "RRC Connection Re-establishment Request" to the "Contention Resolution" field of FIGS. 10 (a) and 10 (b). It is configured in.

In addition, the mobile station UE first sends "Contention Resolution" in the control information transmitted via PDCCH including Temp-C-RNTI after sending "RRC Connection Re-establishment Request" by the random access procedure. Is configured to determine if is included.

Temp-C-RNTI is a temporary C-RNRI (identifier of the mobile station UE in the cell) assigned by a random access response.

Specifically, the mobile station UE analyzes the MAC header and the MAC extension header in such control information, assuming that the field of "Contention Resolution" starts from the 3rd or 4th byte as shown in FIG. 10 (a). It may be configured to determine whether or not "Contention Resolution" is included, or the field of "Contention Resolution" starts from the second byte as shown in FIG. 10 (b). As such, it may be configured to determine whether or not "Contention Resolution" is included without parsing the MAC header.

HARQ is applied to "Contention Resolution", but unlike normal HARQ MAC processing, it moves because multiple mobile station UEs may perform random access at the same time and collide. The station UE sends HARQ Ack feedback only when it is confirmed that the "RRC Connection Re-establishment Request" sent by itself has been echoed back by "Contention Resolution".

In other cases (decoding fails and HARQ Nack does not match, and the echoback content of "Contention Resolution" does not match), the mobile station UE does not send HARQ Ack / Nack feedback.

However, HARQ feedback needs to be transmitted at a timing that satisfies the RTT (round trip time) in which HARQ operates. Therefore, the demand for processing speed is strict, and it is not possible to take the processing time for analyzing the MAC header.

Therefore, it is desirable that the mobile station UE is configured so that the byte position of "Contention Resolution" can be determined and the bit strings of the echoback contents can be directly compared without analyzing the MAC header.

Hereinafter, the operation of the mobile communication system according to the first modification will be described with reference to FIG.

As shown in FIG. 11, RRC connection # 1 is set between the mobile station UE and the radio base station eNB # 1, and S1 connection # 1 is established between the radio base station eNB # 1 and the exchange MME. When the mobile station UE detects RLF (failure in RRC connection # 1) in step S2001 in the set state, cell selection processing is performed in step S2002.

In step S2003, the mobile station UE transmits an RRC Connection Re-establishment Request to the radio base station eNB # 2 that manages the cell # 2 selected by the cell selection process.

At this time, in step S2003A, the radio base station eNB # 2 transmits "Contention Resolution" to the mobile station UE at an arbitrary timing before the CR timer expires.

The operation of steps S2004 to S2014 is the same as the operation of steps S1004 to S1014 shown in FIG.

If the "RRC Connection Re-establishment" in step S2008 does not reach the mobile station UE by the time the timer T301 expires, the mobile station UE determines that the setting of RRC connection # 2 in cell # 2 has failed. To do. In such a case, the mobile station UE releases the RRC connection and enters the "RRC_IDLE state".

Hereinafter, the operation / effect of the mobile communication system according to the first modification will be described.

In the mobile communication system according to the first embodiment of the present invention, when the radio base station eNB # 2 receives the "RRC Connection Re-establishment Request" from the mobile station UE, and the context information of the mobile station UE is input. If it is not stored, it is necessary to acquire the context information of the mobile station UE from the radio base station eNB # 1.

Therefore, when the radio base station eNB # 2 concatenates and transmits "RRC Connection Re-establishment" and "Contention Resolution" in the same TTI, "Contention Resolution" is set to the mobile station UE by the time the CR timer expires. Random access procedure may be repeated even if "RRC Connection Re-establishment Request" reaches the radio base station eNB # 2 normally without reaching.

Therefore, as in the mobile communication system according to the first modification, the radio base station eNB # 2 transmits "Contention Resolution" to the mobile station UE at an arbitrary timing before the CR timer expires. Therefore, such a problem can be solved.

In particular, when the radio base station eNB # 2 receives the "RRC Connection Re-establishment Request" from the mobile station UE and does not store the context information of the mobile station UE, the CR timer expires. It is preferable to transmit "Contention Resolution" to the mobile station UE at any previous timing.

The features of the present embodiment described above may be expressed as follows.

The first feature of the present embodiment is the mobile communication method, in which the mobile station UE for which the RRC connection # 1 (first connection) is set in the cell # 1 (first cell) is in the RRC connection # 1. "RRC Connection Re-establishment Request (RRC Connection Re-establishment Request) for cell # 2 (second cell) selected by the mobile station UE in step A and the mobile station UE when a failure (RLF) is detected. Process B for transmitting the "connection reconfiguration request signal)" and the radio base station eNB # 2 that manages cell # 2 perform "RRC Connection Re-establishment". In response to "Request", step C for determining whether or not the context information of the mobile station UE is stored, and when the radio base station eNB # 2 determines that the context information of the mobile station UE is not stored. , Step D of acquiring the context information of the mobile station UE from the radio base station eNB # 1 that manages the cell # 1, and the radio base station eNB # 2 and the mobile station UE based on the context information of the mobile station UE. The gist is to have step E for setting RRC connection # 2 (second connection) in cell # 2 for mobile station UE.

In the first feature of the present embodiment, in the step B, the mobile station UE transmits a random access preamble to the radio base station eNB # 2, and the radio base station eNB # 2 receives the step B1. Step B2 of transmitting a random access response to the mobile station UE according to the random access preamble, and the mobile station UE makes an "RRC Connection Re-establishment Request" using the resources specified by the random access response. In step B4, the radio base station eNB # 2 has a step B3 of transmitting and a step B4 of transmitting "Contention Resolution (collision resolution signal)" in response to the reception of "RRC Connection Re-establishment Request". , Radio base station eNB # 2 is separate from "RRC Connection Re-establishment" which is a response signal to "RRC Connection Re-establishment Request" before the CR timer (predetermined timer) activated in step B1 expires. , "Contention You may send "Resolution".

In the first feature of the present embodiment, the radio base station eNB # 2 stores the short MAC-I (security parameter) that can uniquely identify the mobile station UE and the context information of the mobile station UE in association with each other. When it is determined in step D that the radio base station eNB # 2 does not store the context information of the mobile station UE corresponding to "short MAC-I" included in the "RRC Connection Re-establishment Request". , The context information of the mobile station UE may be acquired from the radio base station eNB # 1.

The second feature of this embodiment is the radio base station eNB # 2 that manages cell # 2, and is addressed to cell # 2 received from the mobile station UE that sets RRC connection # 1 in cell # 1. In response to the "RRC Connection Re-establishment Request", the determination unit 13 is configured to determine whether or not the context information of the mobile station UE is stored, and the determination unit 13 determines the context information of the mobile station UE. When it is determined that the memory is not stored, the X2 processing unit 16 configured to acquire the context information of the mobile station UE from the radio base station eNB # 1 that manages the cell # 1 and the mobile station UE The gist is to include an RRC processing unit 12 configured to set RRC connection # 2 in cell # 2 for mobile station UE in cooperation with mobile station UE based on context information. ..

In the second feature of the present embodiment, a random access response is transmitted to the mobile station UE according to the random access preamble received from the mobile station UE, and the mobile station uses the resource specified by the random access response. The MAC processing unit 14 is configured to transmit the "Contention Resolution" in response to the reception of the received "RRC Connection Re-establishment Request", and the MAC processing unit 14 is the "RRC Connection" by the mobile station UE. Before the CR timer started when sending the "Re-establishment Request" expires, "Contention Resolution" is set separately from the "RRC Connection Re-establishment" which is the response signal to the "RRC Connection Re-establishment Request". It may be configured to transmit.

In the second feature of the present embodiment, the UE context storage unit 11 configured to store the short MAC-I that can uniquely identify the mobile station UE and the context information of the mobile station UE in association with each other is provided. When the RRC processing unit 12 determines that the context information of the mobile station UE corresponding to the "short MAC-I" included in the "RRC Connection Re-establishment Request" is not stored, the radio base station eNB # It may be configured to acquire the context information of the mobile station UE from 1.

The operations of the mobile station UE, the radio base station eNB # 1 / eNB # 2, and the exchange station MME described above may be performed by hardware or by a software module executed by a processor. , It may be carried out by a combination of both.

Software modules include RAM (Random Access Memory), flash memory, ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electronically Erasable and Programmable ROM), registers, hard disks, and removable disks. Or, it may be provided in an arbitrary format storage medium such as a CD-ROM.

Such a storage medium is connected to the processor so that the processor can read and write information to the storage medium. Further, such a storage medium may be integrated in the processor. Further, such a storage medium and a processor may be provided in the ASIC. Such an ASIC may be provided in the mobile station UE, the radio base station eNB # 1 / eNB # 2, or the exchange station MME. Further, such a storage medium and a processor may be provided as discrete components in the mobile station UE, the radio base station eNB # 1 / eNB # 2, or the exchange station MME.

Although the present invention has been described in detail using the above-described embodiments, it is clear to those skilled in the art that the present invention is not limited to the embodiments described in the present specification. The present invention can be implemented as modifications and modifications without departing from the spirit and scope of the invention as defined by the claims. Therefore, the description of the present specification is for the purpose of exemplification and does not have any limiting meaning to the present invention.

<figref num="1">It is an overall block diagram of the mobile communication system which concerns on 1st Embodiment of this invention.</figref><figref num="2">It is a functional block diagram of the radio base station which concerns on 1st Embodiment of this invention.</figref><figref num="3">It is a figure for demonstrating "short MAC-I" used in the mobile communication system which concerns on 1st Embodiment of this invention.</figref><figref num="4">It is a figure for demonstrating "AS-Context" used in the mobile communication system which concerns on 1st Embodiment of this invention.</figref><figref num="5">It is a figure for demonstrating "RRC Connection Re-establishment Request" used in the mobile communication system which concerns on 1st Embodiment of this invention.</figref><figref num="6">It is a figure for demonstrating "X2 HO Prepaartion" used in the mobile communication system which concerns on 1st Embodiment of this invention.</figref><figref num="7">It is a figure for demonstrating "AS-Configuration" included in "X2 HO Prepaartion" used in the mobile communication system which concerns on 1st Embodiment of this invention.</figref><figref num="8">It is a sequence diagram which shows the operation of the mobile communication system which concerns on 1st Embodiment of this invention.</figref><figref num="9">It is a sequence diagram which shows the operation of the mobile communication system which concerns on modification 1 of this invention.</figref><figref num="10">It is a figure for demonstrating operation of the mobile communication system which concerns on modification 1 of this invention.</figref><figref num="11">It is a sequence diagram which shows the operation of the mobile communication system which concerns on modification 1 of this invention.</figref><figref num="12">It is a sequence diagram which shows the operation of the conventional mobile communication system.</figref>

Code description

eNB ... wireless base station 11 ... UE context storage 12 ... RRC processing unit 13 ... Judgment unit 14 ... MAC processing unit 15 ... X2 processing unit 16 ... S1 processing unit