LTE Typical Service Procedure_V1.0

HUAWEI UMTS 电路交换核心网 协议与信令分析 信令流程

Contents 1 Typical Service Procedure............................................................................................1-1 1.1 Basic Access Procedure................................................................................................................1-1 1.1.1 Initial Context Setup...........................................................................................................1-1 1.1.2 Idle to Active Setup Procedure...........................................................................................1-8 1.1.3 Tracking Area Update (TAU) Procedure..........................................................................1-10 1.1.4 E-RAB Setup Procedure...................................................................................................1-15 1.1.5 E-RAB Modification Procedure.......................................................................................1-19 1.1.6 E-RAB Release Procedure................................................................................................1-23 1.1.7 Mobility Management: Handover Measurement..............................................................1-29 1.1.8 Mobility Management: Handover Procedure....................................................................1-45 1.1.9 Redirection Procedure.......................................................................................................1-55 1.1.10 ANR（Automatic Neighbour Relation）.......................................................................1-68 1.1.11 MRO Algorithm Procedure.............................................................................................1-77 1.1.12 CSFB Procedure from LTE to UMTS (L2U PSHO)......................................................1-79 1.1.13 CSFB from LTE to GERAN (L2G PSHO).....................................................................1-89 1.1.14 X2 Self-Setup Procedure.................................................................................................1-99

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目 录

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

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1Typical Service Procedure

Typical Service Procedure

This chapter describes the typical service procedure in the E-UTRAN, including basic access and handover procedures.

1.1 Basic Access Procedure The basic access procedure consists of the initial context setup procedure and ERAB setup procedure.

1.1.1 Initial Context Setup If the UE initiates a context setup in the E-UTRAN, initial context access is requested by the EPC.The default bearer is set up during the initial context setup procedure. According to 3GPP TS 23.401, a default bearer is allocated to the UE by the EPC if the UE is connected to the PDN for the first time. This default bearer takes effect unless the connection between the UE and PDN ends up. Apart from the default bearer, other bearers between the UE and the same PDN is called dedicated bearer.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.1.1 The initial context setup procedure is as follows: Step 1 If the UE accesses the network for the first time, it initiates random access by sending a RRC CONNECTION REQ message to the eNodeB.

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1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Step 2

The eNodeB allocates resources for the UE if the RRC CONNECTION request is accepted. The eNodeB replies the RRC CONNECTION REQ message with a RRC CONNECTION SETUP message containing configuration parameters for SRB1 setup.

Step 3

The UE submits RRC CONNECTION SETUP COMPLETE report after the configuration by the newly set SRB.The RRC CONNECTION SETUP COMPLETE message also contains the NAS signaling (Attach Request or Service Request).If the UE does not agree with the configuration parameters, it initiates random access again.

Scenarios where the Attach Request message is contained in the NAS signaling: Because the UE initiates a Detach procedure on the EPC side, the UE contexts are deleted on the EPC side; when the UE is powered off abnormally, the data card is removed or inserted. This results in the losing of the UE running data. Therefore, the UE context setup request is delivered through the Attach Request in the NAS signaling. Scenarios where the Service Request message is contained in the NAS signaling in the commercial network:

Step 4

If a Attach Request message is contained in the NAS signaling, security inspection is initiated by the EPC to authenticate and encrypt the NAS signaling.The NAS signaling is transmitted between the UE and the EPC through the SRB.

Step 5

After the exchange of the NAS signaling, the EPC delivers an INITIAL UE CONTEXT SETUP REQ message to the eNodeB. The following parameters are contained in the INITIAL UE CONTEXT SETUP REQ message:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name UE Aggregate Maximum Bit

Presence

Range

M

1Typical Service Procedure

Explaination The UE Aggregate Maximum Bitrate is applicable for all

Rate

Non-GBR bearers per UE which is defined for the Downlink and the Uplink direction and provided by the MME to the eNB.

E-RAB to Be Setup List

1

>E-RAB to Be Setup Item

1 to
IEs

RABs>

>>E-RAB ID

M

ERAB ID

>>E-RAB Level QoS

M

This IE defines the QoS to be applied to an E-RAB.

M

This information element is an IP address.

M

This information element is the GTP Tunnel Endpoint

Parameters >>Transport Layer Address >>GTP-TEID

Identifier to be used for the user plane transport between eNB and the serving gateway. >>NAS-PDU

UE Security Capabilities

O

This information element contains an EPC – UE or UE – EPC message that is transferred without interpretation in the eNB. The UE Security Capabilities IE defines the supported

M

algorithms for encryption and integrity protection in the UE. Security Key

M

The Security Key IE is used to apply security in the eNB for different scenarios.

Trace Activation

O

Defines parameters related to a trace activation.

Handover Restriction List

O

This IE defines area roaming or access restrictions for subsequent mobility action for which the eNB provides information about the target of the mobility action towards the UE, e.g., handover and CCO. If the eNB receives the Handover Restriction List, it shall overwrite previously received restriction information.

UE Radio Capability

O

This IE contains UE Radio Capability information.

Subscriber Profile ID for

O

The Subscriber Profile ID IE for RAT/Frequency

RAT/Frequency priority

Selection Priority is used to define camp priorities in Idle mode and to control inter-RAT/inter-frequency handover in Active mode TS 36.300 [14].

CS Fallback Indicator

O

The IE indicates that a fallback to the CS domain is needed.

SRVCC Operation Possible

O

This element indicates that both UE and MME are SRVCC-capable. E-UTRAN behaviour on receipt of this IE is specified in TS 23.216 [9].

CSG Membership Status

O

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name Registered LAI

Presence

Range

1Typical Service Procedure

Explaination

O

Step 6 After receiving the INITIAL CONTEXT SETUP REQUEST message, the eNodeB allocates the access layer resources to the UE based on the RRM algorithm and security-related algorithms. The eNodeB configures the UE through the RRC reconfiguration and the security handling procedure. Step 7 After the configuration, the eNodeB sends the UE an INITIAL CONTEXT SETUP RESPONSE message indicating the completion of the UE contexts setup. Multiple E-RABs, including the default bearer, are set up during the UE context setup. Besides, a series of UE contexts information related to security, handover rules, UE capability and so on is set. With the UE contexts setup, the UE RRC state is transferred from the RRC_IDLE state to the RRC_CONNECTED state. The UE ECM state is also shifted from the ECM_IDLE state to the ECM_REGISTERED state. In addition, the security mode configuration for the UE is completed. During the initial UE context setup, the MME set up a default bearer between the UE and the P-GW. This default bearer takes effect until the UE and the P-GW is disconnected. If the UE is connected to several P-GWs, a default bearer is setup between the UE and each P-GW.Except the default bearers, bearers between the UE and each P-GW are called dedicated bearers.

1.1.1.2 Frequent failures in the initial UE context setup procedure are as follows: 

No response to the RRC SETUP REQ message

If the eNodeB does not response to the RRC SETUP REQ message from the UE, the UE requests for the RRC setup again. In most cases, there are no extra resources for the newly connected UEs. 

No RRC CONNECTION SETUP COMPLETE message from the

UE

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1Typical Service Procedure

The UE does not send a RRC SETUP CMP message as a respond to the RRC SETUP message from the eNodeB. If the waiting for the RRC CONNECTION SETUP COMPLETE message times out, the eNodeB releases the resources allocated to the UE and waits for the next setup of the UE.Due to the bad performance of the uplink channel, the UE cannot connect to the eNodeB by using the allocated resources. 

No response to the INIT UE MESSAGE from the MME

The eNodeB assembles the NAS-PDU IEs from the RRC CONNECTION SETUP COMPLETE message into INIT UE MESSAGE to the EPC. With no response from the EPC, the eNodeB releases the UE without informing the MME. The eNodeB does not receive the MME S1AP ID (in the first downlink signalling) for the UE allocated by the EPC, so the eNodeB cannot inform the MME with the UE CONTEXT REL REQ message. If the preceding problem occurs, the configuration of the MME needs to be checked, such as whether the TAC in the INIT UE MESSAGE is valid in the MME. If there is no exception in the configuration of the MME in the RANsharing scenario, the EPC that the UE is connected to is the one the operator uses. 

Direct UE-release by the EPC

After receiving the INIT UE MESSAGE, the EPC delivers the DL INFO TRANS to the eNodeB. Afterwards, the UE CONTEXT REL CMD message is delivered.According to the message from the EPC, the eNodeB releases the UE.

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1Typical Service Procedure

If this problem occurs, check for the NASPDU information in the INIT UE MESSAGE and the NAS signaling in the DL INFO TRANS message. Generally, the reject message on the NAS layer, such as Attach Reject and Service Reject, is included in the DL INFO TRANS message. You are advised to send the preceding messages to the technical support personnel for the EPC. Because the assigned value of the NAS PDU information is subject to the APN and the SIM card, you are also advised to change the UE or the SIM card. 

Initial context setup failure

The eNodeB responds to the INIT UE CONTEXT SETUP REQ message with an INIT SETUP FAIL message. If the preceding problem occurs, check for the assigned value of the CAUSE in the INIT SETUP FAIL message. If the assigned value is Transport resource unavailable, check whether the Peer IP PATH in the IP PATHs configured in the eNodeB is consistent with that in the INIT SETUP REQ message. If the IP PATHs are consistent, check whether the corresponding IP route is configured. The assigned value, such as semantic error, Transport syntax error, and abstract syntax error, indicates that the analysis of the UE context information by the eNodeB fails. Under this circumstance, you are advised to compare the initial UE context with the UE context that is set up successfully or ask for help from the technical support personnel for the EPC. 

Initial context setup failure

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1Typical Service Procedure

The eNodeB responds to the INIT UE CONTEXT SETUP REQ message with an INIT SETUP FAIL message. If this problem occurs, check for the security mode configuration. Generally, the same encryption algorithms enjoy the same priority, namely, if the AES enjoys the highest priority in the integrity protection algorithms, it enjoys the highest priority in the encryption algorithms. Some UEs do not support the null integrity protection algorithm, so if both encryption and integrity protection algorithms are set to null, you are advised to modify the algorithms of the AES or SNOW 3G. Because some UEs support the security mode configuration only if the authentication is completed and the authentication switch in the EPC needs to be turned on. If there is no exception in the security mode configuration, check whether the NAS authentication procedure is contained in the network access procedure of the UE.

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1Typical Service Procedure

1.1.2 Idle to Active Setup Procedure

1.1.2.1 The Idle to Active setup procedure is as follows: Step 8 The UE-initiate RRC connection indicates the initial access of the UE. The RRC connection is for the initial UE context setup after the ATTACH REQUEST is delivered. Table 1.1 Analysis of the IEs in the RRC CONN REQ message during the Attach procedure IE/Group Name

Value

Semantics description

ue-Identity

randomValue

Integer value in the range 0 to 240  1.

establishmentCause

mo-Signalling

Indicates Mobile Originating Signalling.

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1Typical Service Procedure

Step 9 After the expiry of the UE inactivity timer, the eNodeB releases the RRC connection between the UE and the eNodeB. However, the UE context is retained by the MME. Table 1.1 Analysis of the IEs in the S1AP UE Context Release Request message IE/Group Name

Value

Semantics description

Message Type MME UE S1AP ID eNB UE S1AP ID Cause

radioNetwork: ----

Indicates a UE has neither received nor

user-inactivity (20)

sent data for a duration exceeding this period of UE inactive timer.

GW Context Release Indication

Table 1.2 Analysis of the IEs in the RRC Release message IE/Group Name

Value

rrc-TransactionIdentifier

0x0 (0)

releaseCause

other (1)

Semantics description Conversion from user-inactivity

Step 10 In terms of the upper level service requirement, the UE requests for the RRC connection again. Because the UE has attached to the eNodeB, the IEs in message in the Idle To Active procedure differ from that in the initial setup procedure.

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1Typical Service Procedure

Table 1.1 Analysis of the IEs in the S1AP_INITIAL_CONTEXT_SETUP_REQ message in the Idle To Active setup procedure IE/Group Name

Value

Semantics description

Message Type MME UE S1AP ID eNB UE S1AP ID UE Aggregate Maximum Bit Rate e-

Only the E-

The E-RAB to be setup is out of

RABToBeSetupListCtxtSUR

RAB setup list

the upper-layer service, so the E-RAB to

eq

information but no

be setup contains no NAS-PDU

NAS-PDU

information elements of the ATTACH

information

ACCEPT message.

elements uERadioCapability

ueEutraCap

If the UE access the network for the first time, the UE capability information needs to be collected after it attaches to the eNodeB. In the Idle to Active procedure, the UE capability information is transmitted from the EPC to the eNodeB in the uERadioCapability message. And therefore, the eNodeB does not needs to query the UE capability.

1.1.3 Tracking Area Update (TAU) Procedure In the TAU procedure, the UE requests for the updating of the current TA. This request is triggered by the following factors:

Generally, the UE requests for updating the registered TA in the network. For periodical updates, the UE availability is submitted to the network periodically. If the RAT changes, such as the conversion from UMTS to LTE or from GSM to LTE, the TAU is triggered. 1.1.3.1 Successful TAU Procedure The successful TAU procedure is shown in Figure 2-1.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Step 11

1Typical Service Procedure

The UE requests for the TAU.

The UE sends the TACKING_AREA_UPDATE_REQ message to the MME. The EMM-TRACKING-AREA-UPDATING-INITIATED is initiated with the start of the T3430 timer.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程



Stop the T3402 timer if it is running.



Stop the T3411 timer if it is running.

 Stop the T3442 timer if it is running. For details about the T3442 timer, see section Timers of EPS mobility management in 3GPP.TS 24.301-10.2.

Table 1.1 Analysis of the IEs in the TRACKING AREA UPDATE REQUEST message

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1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Information Element GPRS ciphering key sequence number

Type Ciphering key sequence number

1Typical Service Procedure

Description

Presence

Length

The UE shall include this IE if the UE

O

1

O

4

O

13

O

5

O

4-15

O

6

O

3

O

1

O

4

O

4-10

O

6

O

1

performs an A/Gb mode or Iu mode to S1 mode inter-system change in EMMIDLE mode and the TIN indicates "PTMSI". Old P-TMSI signature

P-TMSI signature

The UE shall include this IE if the TIN indicates "P-TMSI" and the UE holds a valid P-TMSI signature, P-TMSI and RAI.

Additional GUTI

EPS mobile identity

The UE shall include this IE if the TIN indicates "P-TMSI" and the UE holds a valid GUTI, P-TMSI and RAI.

NonceUE

Nonce

The UE shall include this IE if the TIN indicates "P-TMSI" and the UE holds a valid GUTI, P-TMSI and RAI.

UE network capability

UE network capability

The UE shall include this IE, unless the UE performs a periodic tracking area updating procedure.

Last visited registered TAI

Tracking area identity

This IE shall be included if the UE holds a valid last visited registered TAI.

DRX parameter

DRX parameter

This IE is included by the UE to indicate a change of UE specific DRX parameters to the network.

UE radio capability information update UE radio capability information needed

update needed

The UE shall include this IE if the UE radio capability information in the network needs to be updated.

EPS bearer context status

EPS bearer context status

This IE shall be included if the UE wants to indicate the EPS bearer contexts that are active within the UE.

MS network capability

MS network capability

A UE supporting A/Gb mode or Iu mode shall include this IE, unless the UE performs a periodic tracking area updating procedure.

Old location area identification

Location area identification

The UE shall include this IE during a combined tracking area updating procedure if it has a valid location area identification.

TMSI status

TMSI status

The UE shall include this IE during a combined tracking area updating procedure if it has no valid TMSI available.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Mobile station classmark 2

Mobile station classmark 2

1Typical Service Procedure

This IE shall be included if the UE

O

5

O

2-34

O

5-n

O

1

O

3

The UE shall include this IE.

O

1

This IE shall be included if the UE is

O

1

O

1

O

4

supports SRVCC to GERAN or UTRAN (see 3GPP TS 23.216 [8]), or if the UE is performing a combined tracking area updating procedure. Mobile station classmark 3

Mobile station classmark 3

This IE shall be included if the UE supports SRVCC to GERAN.

Supported Codecs

Supported Codec List

This IE shall be included if the UE supports SRVCC to GERAN or UTRAN to indicate its supported speech codecs for CS speech calls.

Additional update type

Additional update type

The UE shall include this IE if the UE requests "SMS only".

Voice domain preference and UE's

Voice domain preference and

This IE shall be included if the UE

usage setting

UE's usage setting

supports CS fallback and SMS over SGs, or if the UE is configured to support IMS voice, but does not support 1xCS fallback.

Old GUTI type

GUTI type

Device properties

Device properties

configured for NAS signalling low priority. MS network feature support

MS network feature support

This IE shall be included if the UE supports extended periodic timer T3412.

TMSI based NRI container

Network resource identifier

The UE shall include this IE during a

container

combined attach procedure if it has a valid TMSI.

Step 12

The MME accepts the TAU request.

The MME responds to the UE with a TRACKING_AREA_UPDATE_ACCEPT message. If there are UE network capability and MS network capability in the TRACKING_AREA_UPDATE_REQ message, the MME stores these two IEs in the message. If the UE radio capability information update needed IE is included in the TACKING_AREA_UPDATE_REQ message, the MME needs to delete the existed UE radio capability information. If the DRX parameter IE is included in the TRACKING_AREA_UPDATE_REQ message, the MME needs to replace the

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1Typical Service Procedure

existed DRX parameter with that in the message and applies the parameter to the transmission of the downlink data and the user data. If the EPS bearer context status IE is included in the TACKING_AREA_UPDATE_REQ message, the MME needs to indicate the activated bearers in the TRACKING_AREA_UPDATE_ACCEPT message. The MME needs to add the GUTI newly allocated the UE in the TRACKING_AREA_UPDATE_ACCEPT message. The EMM-COMMON-PROCEDURE-INITIATED is initiated with the start of the T3450 timer. The MME adds the new TA list in the TRACKING_AREA_UPDATE_ACCEPT message.

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1Typical Service Procedure

Table 1.1 Analysis of the IEs in the TRACKING AREA UPDATE ACCEPT message Information Element GUTI

Type EPS mobile identity

Description

Presence

Length

This IE may be included to

O

13

O

8-98

O

4

O

6

O

7-10

O

2

O

2

O

2

O

5-47

assign a GUTI to a UE. TAI list

Tracking area identity list

This IE may be included to assign a TAI list to a UE.

EPS bearer context status

EPS bearer context status

This IE shall be included if the network wants to indicate the EPS bearer contexts that are active for the UE in the network.

Location area identification

Location area identification

This IE may be included to assign a new location area identification to a UE during a combined TA/LA update.

MS identity

Mobile identity

This IE may be included to assign or unassign a new TMSI to a UE during a combined TA/LA update.

EMM cause

EMM cause

This IE shall be included if the combined tracking area updating procedure was successful for EPS services only.

T3402 value

GPRS timer

This IE may be included to indicate a value for timer T3402.

T3423 value

GPRS timer

This IE may be included to indicate a value for timer T3423. If this IE is not included, the UE shall use the default value.

Equivalent PLMNs

PLMN list

This IE may be included in order to assign a new equivalent PLMNs list to a UE.

Step 13 The UE responds to the TACKING_AREA_UPDATE_ACCEPT message.

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1Typical Service Procedure

The UE accepts TACKING_AREA_UPDATE_ACCEPT message. The T3430 timer is stopped. The TAU attempt time counter is reset. The EMM-REGISTERED initiated and the EPS updating status is modified to EU1 UPDATED. If the GUTI is included in the TRACKING_AREA_UPDATE_ACCEPT message, the UE shall use this GUTI as new temporary identity for EPS services and shall store the new GUTI. If no GUTI is included in the TRACKING_AREA_UPDATE_ACCEPT message, the existing GUTI continues to take effect. If a new TAI is included in the TRACKING_AREA_UPDATE_ACCEPT message, the existing TAI needs to be replaced with the new one. If no TAI is included in the TRACKING_AREA_UPDATE_ACCEPT message, the existing TAI continues to take effect. If the EPS bearer context IE is included in the TRACKING_AREA_UPDATE_ACCEPT message and the inactive EPS bearers in the EPS bearer context IE is active on the UE side, the UE needs to deactivate these EPS bearers locally. Finally, the TRACKING_AREA_UPDATE_CMP message is delivered by the MME.

Step 14

The MME receives the TAU completion message.

The MME receives the TRACKING_AREA_UPDATE_CMP message. The T3450 timer is stopped. The GUTI in the TRACKING_AREA_UPDATE_ACCEPT message continues is regarded as valid. ----End

1.1.4 E-RAB Setup Procedure If new services are required after the completion of the UE context access, the ERAB setup is initiated. The exchange of the NAS signaling in the The E-RAB

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1Typical Service Procedure

Step 15 If new services are required after the initial UE context setup, the UE applies for the dedicated bearers through the NAS signaling from the MME. Step 16 In response to the UPLINK NAS TRANSPORT message, the MME allocates dedicated bearers to the UE based on the NAS signaling and delivers the E-RAB SETUP REQUEST message to the eNodeB. The E-RAB SETUP REQUEST message contains the E-RAB setup list including the E-RAB ID, QoS information of the bearers, and the configuration information of the transport layer and NAS layer information.Main parameters in the E-RAB SETUP REQUEST message are described in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name UE Aggregate Maximum Bit

Presence

1Typical Service Procedure

Range

O

Explaination The UE Aggregate

Rate

Maximum Bitrate is applicable for all NonGBR bearers per UE which is defined for the Downlink and the Uplink direction and provided by the MME to the eNB.

E-RAB to be Setup List

M

>E-RAB To Be Setup Item

1 to
IEs

RABs>

>> E-RAB ID

M

ERAB ID

>> E-RAB Level QoS

M

This IE defines the QoS

Parameters

to be applied to an ERAB.

>> Transport Layer

M

This information

Address >> GTP-TEID

element is an IP address. M

This information element is the GTP Tunnel Endpoint Identifier to be used for the user plane transport between eNB and the serving gateway.

>>NAS-PDU

M

This information element contains an EPC – UE or UE – EPC message that is transferred without interpretation in the eNB.

Step 17 In response to the E-RAB SETUP REQUEST message, the eNodeB allocates related resources including the transmission resource, radio resource, scheduling resource, power resource, and antenna resource based on the RRM algorithm and delivers the RRC Connection Reconfiguration message to the UE. Step 18 The UE configures parameters based on the resources allocated and informs the eNodeB of the configuration with a RRC Connection Reconfiguration Complete message. Step 19 The eNodeB sends an E-RAB SETUP RESPONSE to the MME, indicating the E-RAB setup completion.

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1Typical Service Procedure

Several E-RABs are set up during the E-RAB setup procedure. If new services are required by the UE or new services are provided to the UE by the network, the E-RAB can be set up by activating the dedicated bearers on the NAS layer. The access network allocates resources to the UE based on the negotiated QoS policy. Description of the tracking message of the E-RAB setup procedure is as follows:

Message exchange over the S2 interface during the E-RAB setup procedure:

Message exchange over the Uu interface during the E-RAB setup procedure:

Content and key IEs of the E-RAB SETUP REQUEST message

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Content and key IEs of the E-RAB SETUP RESPONSE message

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1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

1.1.5 E-RAB Modification Procedure If the service property required by the subscribers is changed and related parameters needs to be modified, the E-RAB modification is triggered. The typical E-RAB modification procedure is shown in the following figure:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

E-RAB modification procedure is as follows: Step 20 If new services are required after the setup of the initial UE context and E-RABs, the UE applies for modifying bearers through the NAS signaling from the MME. Step 21 In response to the UPLINK NAS TRANSPORT message, the MME allocates bearers to the UE based on the service modifications and delivers the E-RAB MODIFY REQUEST message to the eNodeB. The E-RAB MODIFY REQUEST message contains the E-RAB setup list including the E-RAB ID, QoS information of the bearers, the configuration information of the transport layer, and NAS layer information. Main parameters in the E-RAB MODIFY REQUEST message are described in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name Message Type

Presence

1Typical Service Procedure

Range

M

Explaination The Message Type IE uniquely identifies the message being sent. It is mandatory for all messages.

MME UE S1AP ID

M

The MME UE S1AP ID uniquely identifies the UE association over the S1 interface within the MME.

eNB UE S1AP ID

M

The eNB UE S1AP ID uniquely identifies the UE association over the S1 interface within the eNB.

UE Aggregate Maximum Bit

O

The UE Aggregate

Rate

Maximum Bitrate is applicable for all NonGBR bearers per UE which is defined for the Downlink and the Uplink direction and provided by the MME to the eNB.

E-RAB to be Modified List

M

>E-RAB To Be Modified

1 to
Item IEs

RABs>

>> E-RAB ID

M

ERAB ID

>> E-RAB Level QoS

M

This IE defines the

Parameters

QoS to be applied to an E-RAB.

>> NAS-PDU

M

This information element contains an EPC – UE or UE – EPC message that is transferred without interpretation in the eNB.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Step 22 In response to the E-RAB MODIFY REQUEST message, the eNodeB re-allocates related resources including the transmission resource, radio resource, scheduling resource, power resource, and antenna resource based on the RRM algorithm and delivers a RRC Connection Reconfiguration message to the UE. Step 23 The UE configures parameters based on the resources allocated and informs the eNodeB of the configuration with a RRC Connection Reconfiguration Complete message. Step 24 An E-RAB MODIFY RESPONSE from the eNodeB to the MME indicates the completion of the E-RAB modification. Several E-RABs are set up during the E-RAB modification procedure. If new services are required by the UE or new services are provided to the UE by the network, the E-RAB can be set up by activating the dedicated bearers on the NAS layer. The access network allocates resources to the UE based on the negotiated QoS policy.

Content and key IEs of the E-RAB MODIFY REQUEST message

26

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Content and key IEs of the E-RAB MODIFY RESPONSE message

27

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

1.1.6 E-RAB Release Procedure The E-RABs set up are released in the E-RAB release procedure. If corresponding services are finished, the UE initiates an E-RAB release. The typical E-RAB release procedure is described in the following figure:

28

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Step 25 If corresponding services are finished, the UE initiates an E-RAB release. The UE applies for the E-RAB release from the MME through deactivating the EPS bearer. Step 26 In response to the UPLINK NAS TRANSPORT message, the MME releases resources on the EPC side based on the resource release information and delivers an E-RAB RELEASECOMMAND message to the eNodeB. The E-RAB RELEASECOMMAND message contains the E-RAB release list including the ERAB ID, QoS information of bearers, configuration information of the transport layer, and NAS layer information. Main parameters in the E-RAB RELEASECOMMAND message are described in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name Message Type

Presence M

1Typical Service Procedure

Range

Explaination The Message Type IE uniquely identifies the message being sent. It is mandatory for all messages.

MME UE S1AP ID

M

The MME UE S1AP ID uniquely identifies the UE association over the S1 interface within the MME.

eNB UE S1AP ID

M

The eNB UE S1AP ID uniquely identifies the UE association over the S1 interface within the eNB.

UE Aggregate Maximum Bit

O

The UE Aggregate

Rate

Maximum Bitrate is applicable for all NonGBR bearers per UE which is defined for the Downlink and the Uplink direction and provided by the MME to the eNB.

E-RAB To Be Released List

M

NAS-PDU

O

This information element contains an EPC – UE or UE – EPC message that is transferred without interpretation in the eNB.

Step 27 Responding to the E-RAB RELEASE COMMAND message, the eNodeB releases dedicated bearers on the E-UTRAN side. ：

Step 28 Because resources in the physical layer are multiplexed, if users do not release bearers, resource reconfiguration occurs over the interface. The reconfiguration signaling over the Uu interface supports the DRB release. The key IE in the reconfiguration signaling over the Uu interface is the DRB release list. In response to the RRC Connection Reconfiguration message, the UE releases the

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

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DRB and configures AS layer parameters based on the resources allocated and the DRB release list. The UE informs the eNodeB of the completion of the E-RAB release with a RRC Connection Reconfiguration Complete message. Step 29 An E-RAB RELEASE COMPLETE message from the eNodeB to the MME indicates the completion of the E-RAB release.

Several E-RABs are released during the E-RAB release procedure. If some services needs to be released by the UE or dedicated bearers needs to be released by the network, the E-RAB release is initiated by releasing the bearer resources on the NAS layer.

Description of the tracking message of the E-RAB release procedure is as follows: Message exchange over the S1 interface during the E-RAB release procedure is shown in the following figure:

Message exchange over the Uu interface during the E-RAB release procedure is shown in the following figure:

31

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Content and key IEs of the E-RAB RELEASE COMMAND message

32

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Content and key IEs of the E-RAB RELEASE RESPONSE message

33

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.7 Mobility Management: Handover Measurement A UE in the connected mode may perform handovers between cells due to cell coverage or load. A complete handover process consists of two stages: handover measurement and handover procedure. In case of blind handovers, handover measurement is not required. 1.1.7.1 Handover Measurement 

Measurement The LTE Uu interface protocol lists multiple types of measurements. It also

describes how to trigger, configure, and report measurements. For details, see

34

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

3GPP TS 36.300, 3GPP TS 36.133, 3GPP TS 36.214, and 3GPP TS 36.331.3GPP TS 36.331 defines measurement types. The measurement types to be used for handovers and radio resource management (RRM) algorithms depend on product policies. The multiple measurements to be configured for the UE are subject to the UE measurement capability and the sharing configuration of different measurement types. The configuration of the measurement parameters depends on the measurement frequency, measurement accuracy of the UE physical layer, measurement algorithm used by the UE, and key coefficients. The measurement is performed by the UE. Typical measurement procedure is shown in the following figure.

Step 1 The physical layer measures the specified counters. Step 30 The physical layer submits the basic measurement output to the upper layer for filtering and event evaluation. Step 31 The UE RRC layer submits the cells meeting the evaluation criteria with the best cell included first to the eNodeB. ----End



Measurement-related Signaling

The measurement configuration IE is included in the RRCConnectionReconfiguration message, as shown in the following figure.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

The measurement report is submitted through a separate uplink RRC signaling as shown in the following figure.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.7.2

Measurement Mechanism of the Air Interface 

Intra-frequency Measurement

37

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

The intra-frequency measurement includes the measurement of an E-UTRAN serving cell and a neighboring E-UTRAN cell with the same frequency as the serving cell of the UE.



Inter-frequency Measurement

The inter-frequency measurement includes the measurement of an E-UTRAN serving cell and a neighboring E-UTRAN cell with different frequency from the serving cell of the UE. For a UE with only one baseband receive channel, during inter-frequency measurement, the BBU instructs the RRU to work at the frequency to be measured. After the measurement, the RRU continues to work at the original frequency. If the UE works with multiple receiver channels, different frequency can be supported. Therefore, whether the measurement GAP is required during inter-frequency measurement depends on the UE capability. There are multiple specifications for inter-frequency measurements. If a measurement GAP is required, the basic measurement period is 480 ms. The UE reports measurement output to layer 3 every 480 ms. The UE must measure at least four inter-frequency neighboring cells in the neighboring cell list within 480 ms.

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After the measurement, the UE submits the measurement output to the eNodeB based on the parameters configured by the eNodeB. 

Inter-RAT Measurement The UE measures the neighboring cells of the GSM, UMTS, or CDMA2000

cells. Similar to the inter-frequency measurement, the measurement GAP is needed in the inter-RAT measurement. There are multiple measurement specifications in terms of the measurement GAP and the GAP mode configured. The UE must measure a minimum of six inter-RAT neighboring cells of the UTRAN cells in the neighboring cell list within 480 ms. For the GERAN system, the UE must measure the RSSIs of a minimum of ten GSM carriers within each measurement GAP period. Details about the content of the inter-RAT measurement are described in another section. 

Measurement GAP Literally, the GAP means slot. Measurement GAPs, just like the depressions drivers are confronted with for every certain distance. The eNodeB must negotiate with the UE about the time for entering the measurement GAP when both the uplink and downlink data is not scheduled. If a measurement GAP is set, the eNodeB periodically enters a measurement GAP until one of the following situations occurs: a. The eNodeB stops the measurement GAP. b. The UE stops the measurement GAP configuration due to a handover. For details about the measurement GAP started by the UE, see sections in the

corresponding SON protocols of the R9 version. Capability indicators related to measurement GAPs The UE-EUTRA-Capability IEs (the following figures show two IEs) indicate whether the measurement GAPs are required in inter-frequency measurement at a specified frequency. InterFreqBandInfo ::=

SEQUENCE {

interFreqNeedForGaps

BOOLEAN }

−

RSRP/RSRQ/RSSI

The measurement indicator for an EUTRAN cell are RSRP, RSRQ, and RSSI. For details about the measurement indicators for different access networks, see 3GPP 36.214.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Reference signal received power (RSRP) is defined as the linear average value of the transmit power for reference signals on a specific bandwidth in a cell. RSRP reflects the downlink signal strength of the cell detected by the UE. Received Signal Strength Indicator (RSSI) is defined as the linear average value of the transmit power for reference signals on a specific bandwidth. The RSSI is the total transmission power of the reference signal. The RSSI is calculated based on more types of signals than RSRP, such as, data channel signals, neighboring channels signals, and noises. The RSSI is subject to services. For example, adding the transmit power of the reference signal during the packet injection increases the RSSI.

Reference Signal Received Quality (RSRQ) is calculated according to the following formula: RSRQ = N × RSRP/RSSI where: N indicates the number of RBs on the specified bandwidth. The RSRQ is a relative value indicating the amplitude difference between the effective signal strength and the total power. It reflects the real-time signal quality of the current cell. Cell load changes affect the measurement result of the RSRQ. If inappropriate parameters are set for related events, there is a high possibility that an event is reported when services are performed.

Examples of the measurement results of RSRP, RSSI, and RSRQ are listed in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

The air interface protocol does not include negative values, and therefore a conversion is required between the IE values over the interfaces and actual value according to the following formulas: RSRP = IE value – 140 dBm RSRQ= (IE value – 40)/2 dB The measurement output submitted by the UE to the eNodeB is converted based on the 3GPP TS 36.133, as shown in the following table. Reported value

Measured quantity value

Unit

RSRP_00

RSRP  -140

dBm

RSRP_01

-140  RSRP < -139

dBm

RSRP_02

-139  RSRP < -138

dBm

…

…

…

RSRP_95

-46  RSRP < -45

dBm

RSRP_96

-45  RSRP < -44

dBm

RSRP_97

-44  RSRP

dBm

Reported value

Measured quantity value

Unit

RSRQ_00

RSRQ  -19.5

dB

RSRQ_01

-19.5  RSRQ < -19

dB

RSRQ_02

-19  RSRQ < -18.5

dB

…

…

…

RSRQ_32

-4  RSRQ < -3.5

dB

RSRQ_33

-3.5  RSRQ < -3

dB

RSRQ_34

-3  RSRQ

dB



Measurement Indicators

The QuantityConfig in the 3GPP TS36.331 specifies the measurement coefficients for evaluating and calculating the measurement output of the physical layer. One of the parameters is a filtering coefficient to smoothen the measurement. Point A represents sampling measurement values at the physical layer. The linear average of these sampling measurement values is obtained after layer 1 filtering. Point B represents the interface between the physical layer and an upper layer. Over the interface, the physical layer periodically reports measurement outputs to the RRC layer. Parameters in the IE QuantityConfig are used in layer 3 filtering.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

RRC configures parameters

Layer 1 filtering

A

B

Layer 3 filtering

RRC configures parameters

C C'

Evaluation of reporting criteria

D

The layer 3 filtering on the UE is calculated according to the following formula:

Fn  (1  a )  Fn 1  a  M n Where: F indicates the filtered value; M indicates the original value reported by the physical layer. a is equal to 1/2(k/4) . Parameter K, known as the filter coefficient, can be configured on the eNodeB. If K is set to 0, the UE does not perform filtering on layer 3.A larger value of this parameter indicates a greater smoothing effect on the signal and a higher anti-fading capability but a lower tracing capability of signal fluctuations. 

Triggering Quantity

The triggerQuantity in the 3GPP TS 36.331 specifies the measurement indicators for triggering measurement events submitted by the UE.With several measurement indicators, the indicator that can trigger event report must be specified. For example, if the RSRP is specified, an event is reported only when the measurement output reaches the specification. Only one triggering quantity can be specified in one measurement output. 

Report Quantity

The reportQuantity IE defined in 3GPP TS 36.331 specifies the content to be included in the measurement report. There are two alternatives for setting the report quantity: One is to keep it the same as either the RSRP or the RSRQ; the other is to report both the RSRP and RSRQ to the eNodeB.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程



1Typical Service Procedure

TimeToTrigger and Hysteresis

TimeToTrigger and hysteresis help prevent jitter and ping-pong handovers in terms of the time and the signal strength, respectively. The TimeToTrigger and hysteresis are used at the RRC layer of the UE and they must be configured based on the measurement of the physical layer. For example, in intra-frequency measurement, the physical layer of the UE submits the measurement result to the RRC layer every 200 ms. If the timeToTrigger used in intra-frequency measurement is less than 200 ms, the parameter cannot help prevent jitter. 

Offset

The frequently used offset parameters are ofs, ofn, ocs, and ocn. s indicates the serving cell. n indicates the neighboring frequency or neighboring cell. f indicates the frequency. c indicates the cell. They are in the unit of dB.These parameters can be configured by customers in MML commands related to neighboring frequencies and cells. The cell individual offset (CIO) mentioned in handover tests is the specific offset of the neighboring cell, which is defined as the ocn parameter in the 3GPP TS 36.331. Offsets exert positive and negative effect on the signal amplitude. A positive offset enhances the measurement result and a negative one weakens the measurement result. A greater positive offset number helps handover to a preferred frequency. On the contrary, a negative offset reduces the handover to a cell that is not preferred. If the serving cell offset is set to a great positive value and the neighboring cell offset is set to 0, there is a low possibility that a UE hands over to other cells. 1.1.7.3 Event Measurement Event measurement is based on the monitoring and evaluation of the downlink signal quality of the serving cell and neighboring cell by the UE. Event measurement reflects the signal coverage changes during UE movement. Event measurement can trigger coverage-based handovers and identify UE motivation directions and locations.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

The event defined in the protocol is selected depending on the product policy. For example, event A3 or A4 is used for triggering intra-frequency handovers or event A3 is used for triggering inter-frequency handovers. 

Event A1/A2

If the signal quality increases and remains good in the time-to-trigger period, event A1 is reported with the following conditions are met: Ms  Hys  Thresh

If the signal quality decreases and remains bad in the time-to-trigger period, event A2 is reported with the following conditions are met: Ms  Hys  Thresh

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

The Threshold in the preceding figures and the Thresh in the inequalities, refer to the same thing, that is, the threshold for triggering event A1 or A2.The Hysteresis in the preceding figures equals to the Hys in the inequalities.



Event A3

Measurement Quality

Cell1

Offset + Hysteresis

Cell2 Time-To-Trigger

Time

The blue line in the preceding figure indicates the signal quality of the serving cell (cell 1) and the red line indicates that of the neighboring cell (cell 2). When the signal quality of cell 2 is far better than that of cell 1 during the TimeToTrigger period and the signal amplitude meets the inequality 1, the UE submits an entering event A3 report:

Inequality 1 (condition for entering event A3): Mn  Ofn  Ocn  Hys  Ms  Ofs  Ocs  Off

Inequality 2 (condition for leaving event A3): Mn  Ofn  Ocn  Hys  Ms  Ofs  Ocs  Off

(For details about the ofs, ofn, ocs, and ocn, see offset description in section 2.1.)

Entering event A3 indicates that the signal quality of the neighboring cell starts to prevail over that of the serving cell. Leaving event A3 indicates that the quality of the prevailing of the signal quality of the neighboring cell ends up. This can help determine whether the UE moves towards the cell edge or cell center in intra-frequency coverage.

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1Typical Service Procedure

Leaving event A3 is reported only after entering event A3 is reported. Therefore, the UE must check whether the cell is in the list of the cells that have entered event A3 before reporting leaving event A3.If the UE is required to report the leaving event, the UE can be informed by sending the reportOnLeave IE in the event A3 configuration, as shown in the following figure. eventA3

SEQUENCE { a3-Offset

INTEGER (-30..30),

reportOnLeave

BOOLEAN}



Event A4

Definition Mn  Ofn  Ocn  Hys  Thresh 

Event B1

Similar to the mechanism of event A4, event B1 also indicates the signal quality of the neighboring cell turns to be better.The difference lies in that in event A4, the neighboring cell is an EUTRAN cell, and in event B1, the neighboring cell is an inter-frequency cell. 

Event-Triggered Periodical Report

A reportAmount parameter is configured for an event measurement. If the value of this parameter is set to 1, the report is an event-triggered periodical report. Event-triggered periodical report has the following two functions: (1) If one-off algorithm processing, such as handover is carried out when the eNodeB enters an event, this report helps prevent non-processing of the algorithm

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

or the loss of the report. (2) If signal quality needs to be evaluated for several times, this report is submitted periodically until the leaving conditions are met. 1.1.7.4 Periodical Measurement Periodical measurement is not triggered by an event and does not have a threshold. The measurement result must be reported periodically to the eNodeB if the UE grasps the signal quality of a neighboring cell. Two types of periodical measurements are defined for EUTRAN and GERAN cells, namely, reportStrongestCells and reportCGI, as shown in the following IE. periodical

SEQUENCE {

purpose

ENUMERATED { reportStrongestCells, reportCGI } }

A third type of periodical measurement is defined for UTRAN and CDMA2000 cells, that is, reportStrongestCellsForSON. 

CGI Measurement

The cell global identification (CGI) measurement is used to support the SONANR function. The CGI information obtained by the UE helps complete the neighboring cell list on the eNodeB. When to trigger a measurement and how to use a measurement report is subject to the ANR algorithm. The CGI measurement has a long delay. All CGI measurements including intra-frequency CGI measurements require specific scheduling, such as the discontinuous reception (DRX).  Timer T321 defined for the CGI measurement in the protocol specifies the maximum delay for measuring an E-UTRAN cell is 1 second, and 8 seconds for inter-RAT measurements. Three parameters are fixed for CGI measurements, namely, number of reporting times is set to 1, reporting interval is set to unavailable, and the maximum number of cells in a report is set to 1.Inter-RAT SON Measurement

The inter-frequency self-organizing network (SON) measurement is dedicated to the measurement of UTRAN and CDMA2000 cells. The objects to be measured in the UTRAN and CDMA2000 systems are cells, however, that to be measured in the LTE and GSM systems are frequencies. Even if no neighboring cell is configured in the LTE and GSM systems, the UE can detect new neighboring cells based on the frequencies configured in intra- or inter-frequency measurement. Neighboring cells must be configured for the measurement in the UTRAN and

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

CDMA2000 systems. If the UE is expected to detect new neighboring cells, the UE needs to be informed through the reportStrongestCellsForSON message. After being informed, the UE reports the physical cell ID of the neighboring cell with the strongest signal on the related frequency and the measurement result to the eNodeB. 

Measurement of the Cell with the Strongest Signal

reportStrongestCells The protocol specifies that results of the CGI measurement and the inter-RAT SON measurement are reported only once. However, measurements of cells with the strongest signal are real periodical measurements. The UE reports the measurement result based on the number of reported times and the period configured by the eNodeB without limitations. Periodical measurements and event measurements are different. Periodical measurements are released by the UE, however, event measurements are released by the eNodeB. For example, if the number of the measurement time is set to 2, the UE releases the measurement after reporting the measurement result twice. If the number of the measurement time is set to definite, the measurement must be released by the eNodeB. The physical layer of the UE measures the object related to the measurement ID, such as a frequency; therefore, the physical cell IDs of multiple cells can be reported but is not limited to the cell with the strongest signal. If no neighboring cell is detected, the UE reports the serving cell ID to the eNodeB. 

UE Tx-Rx Time Difference Measurement

The result of the UE Rx - Tx time difference measurement can be used for locating the UE. In the UE Tx-Rx time difference measurement, the UE measures the serving cell instead of the serving frequency as configured. Besides, the neighboring cell is not included in the measurement report. The result of the UE Tx-Rx time difference measurement is not filtered by layer 3 filtering. That is, this measurement is not subject to the layer 3 filtering coefficient. For details about the conversion between the actual measurement result and the result in the measurement report, see table 9.1.9.2-1 in the 3GPP TS 36.133. 1.1.7.5 Measurement Association

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1Typical Service Procedure

MeasId List measObjectId

measId

reportConfigId

MeasObject List measObject EUTRA measObject GERAN

ReportConfig List

measObject UTRA measObject CDMA2000

reportConfig reportConfig EUTRA InterRAT reportConfig Periodical

One measurement control ID is associated with one measurement object and one measurement report. The eNodeB allocates and manages measurement IDs. Based on the measurement result and measurement ID in the measurement report sent by the UE, the eNodeB can determine the purpose of the measurement report. The measurement object is multiplexed by frequency. Each frequency is configured with only one measurement object. Follow-up configurations overwrite original configurations. A measurement report can also be configured with a dedicated ID. A measurement association example is described in the following figure. Suppose two neighboring cells with frequencies A and B respectively are configured. Four intra-frequency cells and these two neighboring cells are measured.

Measurement Type

Measurement ID

MeasurementObj ID

RprtCfg ID

A3 for algorithm 1 A3 for algorithm 2 A1 for algorithm 1 A2 for algorithm 1 Measurement of the cell with the strongest signal for algorithm 3 Measurement of the cell with the strongest for algorithm 3

1 2 3 4 5

1 1 1 1 2 for frequency A

1 2 3 4 5

6

3 for frequency B

6

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1Typical Service Procedure

1.1.8 Mobility Management: Handover Procedure If the handover is measured to reach the threshold, the eNodeB initiates a handover. The handover procedure in LTE networks is classified into the following types: 

Intra-RAT handover

X2-based handover S1-based handover Intra- eNodeB handover Intra-cell handover (synchronized with the UE) 

Inter-RAT handover

Handover to the WCDMA system Handover to the GSM or EDEG system Handover to the CDMA2000 system 1.1.8.1 Intra- eNodeB handover

Step 1 UE submits measurement reports to the eNodeB to trigger the eNodeB to initiate a handover. Step 2 The eNodeB delivers a RRCConnectionReconfiguration (mobilityControlInfo) message to the UE to request the UE to hand over to another cell. IEs in the RRCConnectionReconfiguration(mobilityControlInfo) message are listed in the following table. The most important IE in the RRCConnectionReconfiguration message is MobilityControlInfo. This IE indicates a handover command. RRCConnectionReconfiguration > MobilityControlInfo >> targetPhysCellId

Indicating a handover command. Indicating the physical cell ID of the target cell.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

>> carrierFreq >> carrierBandwidth >> T304 >> newUE-Identity >> radioResourceConfigCommon >> Rach-ConfigDedicated > RadioResourceConfigDedicated

1Typical Service Procedure

Indicating the frequency of the target cell and needing to be carried for inter-frequency handovers. Indicating the bandwidth of the target cell. Indicating the expiry limitation of timer T304 in the target cell. Indicating a new CRNTI the target cell allocates to the UE. Indicating the common radio resource configured for the target cell. Specifies the dedicated random access parameters. Adjusting dedicated radio resources used by the UE, such as signaling radio bears (SRBs) and data radio bears (DRBs) during the handover

Step 3 After receiving the RRCConnectionReconfiguration message, the UE accesses the target cell based on the configurations contained in the message. After successfully entering the target cell, the UE sends an RCConfigurationReconfigurationComplete message to the eNodeB, indicating that the handover succeeds. Step 4 After receiving the RCConfigurationReconfigurationComplete message, the eNodeB delivers measurement configurations based on the configurations of the new cell. ----End 1.1.8.2 Inter-eNodeB X2-based handover

Step 1 The UE submits measurement reports to the eNodeB to trigger the eNodeB to initiate a handover. Step 32 The source eNodeB sends a HandoverRequest message to the target eNodeB. The IEs in the HandoverRequest message are listed in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name

Presence

Old eNB UE X2AP ID

M

1Typical Service Procedure

Semantics description Indicating the X2AP ID the source eNodeB allocates to the UE to identify UEs over the X2 interface.

Cause

M

Indicating the handover cause, such as Handover Desirable for Radio Reasons and Resource Optimization Handover.

Target Cell ID

M

Indicating the ID of the target cell.

GUMMEI

M

Indicating the identifier of the EPC the UE is connected to

UE Context Information > MME UE S1AP ID > UE Security Capabiliti

Indicating the UE context M

Indicating the identifier the MME allocates to the UE.

M

Indicating the UE security capabilities.

M

Indicating the security information on the source eNodeB,

es >AS Security Information

including the security cipher key used by the source eNodeB. > UE Aggregate Maximum

M

Indicating the AMBR of the UE.

Bit Rate >E-RABs To Be Setup

Indicating the E-RABs set up by the UE

List >>E-RABs To Be Setup Item >>> E-RAB ID >>> E-RAB Level

M

Indicating the ID of an E-RAB.

M

Indicating the QoS information of an ERAB.

O

Informing the peer eNodeB that the ERAB needs to be

QoS Parameters >>> DL Forwarding

forwarded. >>> UL GTP Tunnel

M

Indicating the GTPU address the EPC allocates for the E-RAB

M

Transmitting the RRC configurations of the source eNodeB to

Endpoint >RRC Context

the target eNodeB using a container over the X2 interface.

During a handover, the source eNodeB must inform the target eNodeB of all parameter configurations of the UE. Parameters related to the X2 and S1 interfaces can be transmitted by IEs, but parameters related to the UE RRC layer must be transmitted using a container.

Step 33 Upon receiving the HandoverRequest message, the target eNodeB evaluate an admission. If the admission is allowed, the target eNodeB sends a HANDOVER REQUEST ACKNOWLEDGE message to the source eNodeB, indicating that the handover preparation is ready. IEs in the HANDOVER REQUEST ACKNOWLEDGE message are listed in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name Old eNB UE X2AP ID

Presence M

1Typical Service Procedure

Semantics description Indicating the UE identifier contained in the HandoverRequest message.

New eNB UE X2AP ID

M

Indicating a new UE identifier the target eNodeB allocates to the UE over the X2 interface.

E-RABs Admitted List

Indicating the ERABs admitted.

>> E-RAB ID

M

>> UL GTP Tunnel

O

Endpoint >> DL GTP Tunnel

O

Endpoint E-RABs Not Admitted List

Indicating the address for forwarding the uplink user plane data to the source eNodeB. Indicating the address for forwarding the downlink user plane data to the source eNodeB.

O

Indicating E-RABs not admitted. This IE is carried only in special conditions.

Target eNB To Source eNB

M

Transparent Container Criticality Diagnostics

Indicating the way used for transparently transmitting Uu interface messages to the source eNodeB

O

Indicating that the handover fails. This IE is carried if handover fails due to message decoding failures at the peer part or incorrect IE fillings.

Step 34 The source eNodeB sends the HANDOVER REQUEST ACKNOWLEDGE message to the UE. Figure 1.1 The source eNodeB sends the HANDOVER REQUEST ACKNOWLEDGE message to the UE. Step 35 The source eNodeB starts the transferring procedure by sending a SNStatusTransfer message if E-RABs are needed to be transferred. IEs in the SNStatusTransfer message are listed in the following table.

53

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Figure 1.1 The source eNodeB starts the transferring procedure by sending the SNStatusTransfer message if ERABs are needed to be transferred. IEs in the SNStatusTransfer message are listed in the following table. IE/Group Name Old eNB UE X2AP ID New eNB UE X2AP ID

Presence

Semantics description

M

Indicating the UE identifier the source eNodeB allocates to the UE.

M

Indicating the UE identifier the target eNodeB allocates to the UE.

E-RABs Subject To Status

Indicating the E-RABs to be transferred

Transfer List >E-RABs Subject To Status Transfer Item >> E-RAB ID

M

Indicating the ID of an E-RAB.

>>Receive Status Of UL

O

Indicating the receiving status of uplink SDUs.

>> UL COUNT Value

M

Indicating the PDCP SN and SDU HFN of the uplink

>> DL COUNT Value

M

Indicating the PDCP SN and SDU HFN of the downlink

PDCP SDUs

Step 36 Based on the RRCConnectionReconfiguration message, the UE reconfigures radio parameters and hands over to the target eNodeB. Step 37 After accessing the target eNodeB, the UE sends a RRCConnectionReconfigurationComplete message to the target eNodeB. Step 38 Upon receiving the RRCConnectionReconfigurationComplete message, the target eNodeB sends a PathSwitchRequest message requesting the EPC to change the user plane path. IEs in the PathSwitchRequest message are listed in the following table. IE/Group Name eNB UE S1AP ID

Presence

Semantics description

M

Indicating a new S1 interface identifier the target eNodeB allocates to the UE

E-RAB To Be Switched in

Indicating the ERABs to be switched.

Downlink List >E-RABs Switched in Downlink Item IEs >>E-RAB ID

M

Indicating the ID of an E-RAB.

>>Transport layer address

M

Indicating a new user plane address that the target eNodeB allocates to the E-RAB.

>>GTP-TEID

M

Indicating a new GTPU TEID that the eNodeB allocates to the ERAB

Source MME UE S1AP ID

M

Indicating an S1 interface identifier the EPC allocates to the UE. This IE is carried in the HandoverRequest message sent from the source eNodeB to the target eNodeB.

E-UTRAN CGI

M

Indicating the ID of the cell the UE hands over to.

TAI

M

Indicating the TAI the UE hands over to

54

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Step 39

1Typical Service Procedure

The EPC sends a PATH SWITCH REQUEST ACKNOWLEDGE message to the target eNodeB if the EPC allows the user plane handover. IEs in the PATH SWITCH REQUEST ACKNOWLEDGE message are listed in the following table.

IE/Group Name

Presence

MME UE S1AP ID UE Aggregate Maximum

Semantics description

M

Indicating the new S1AP ID allocated to the UE by the MME.

O

Indicating the AMBR of the UE.

Bit Rate E-RAB To Be Switched in

Indicating the ID of the E-RABs to be switched.

Uplink List >E-RABs Switched in Uplink Item IEs >>E-RAB ID

M

Indicating the ID of an E-RAB.

>>Transport Layer Address

M

Indicating a transport layer address reallocated by the EPC

>>GTP-TEID

M

Indicating a GTPU TEID reallocated by the EPC

E-RAB To Be Released

O

List

If the handover is not allowed, this IE is contained in the EPC to instruct the eNodeB to the release the E-RABs that cannot be switched.

Security Context

M

Indicating the security context of the UE

Step 40 Upon receiving the PathSwitchRequestAck message, the target eNodeB send a UEContextRelease message to the source eNodeB, instructing the source eNodeB to delete the UE. This indicates that the handover succeeds. The source eNodeB releases the UE until local data transmission is completed. ----End

Traced Messages During an X2-based Handover Message exchange over the Uu interface on the source eNodeB is shown in the following figure:

Message exchange over the X2 interface on the source eNodeB is shown in the following figure:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Message exchange over the Uu interface on the target eNodeB is shown in the following figure:

Message exchange over the X2 interface on the target eNodeB is shown in the following figure:

Message exchange over the S1 interface on the target eNodeB is shown in the following figure:

The content and key IEs in a RRC CON RECFG message are shown in the following figure:

56

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.8.3 Intra-eNodeB S1-based Handover

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Procedure for intra-eNodeB S1-based handover is as follows: Step 1 The UE submits measurement reports to the eNodeB to trigger the eNodeB to initiate a handover. Step 41 The source eNodeB sends a HandoverRequired message to the EPC. IEs in the HandoverRequired message are listed in the following table: IE/Group Name Handover Type

Presence M

Semantics description Indicating the handover type, such as intra-RAT handovers and interRAT handovers

Cause

M

Indicating the reason for a handover. It is the same as that for a X2based handover.

Target ID

M

Indicating the ID of the target NE. For an intra-RAT handover, the target NE is an eNodeB. For an inter-RAT handover, the target ID is the ID of the NE in the target system, such as RNC-ID or CGI.

Direct Forwarding Path

O

Availability

Indicating the availability of a direct forwarding path determined by the source eNodeB.

Source to Target Transparent Container

M

Indicating the RRC layer configurations of the UE transmitted using a container.

Step 42 Upon receiving the HandoverRequired message, the EPC sends a HandoverRequest message to the target eNodeB.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name MME UE S1AP ID Handover Type

Presence

1Typical Service Procedure

Semantics description

M

Indicating a new UE S1AP ID the MME allocates to the UE

M

Indicating the handover type, such as intra-RAT handovers and inter-RAT handovers

Cause

M

Indicating the reason for a handover. It is the same as that for an X2-based handover.

UE Aggregate Maximum Bit

M

Indicating the AMBR of the UE.

Rate E-RABs To Be Setup List

Indicating the E-RABs to be set up by the target eNodeB

>E-RABs To Be Setup Item IEs >>E-RAB ID

M

Indicating the ID of an E-RAB.

>>Transport Layer Address

M

Indicating the address that the E-RAB allocates to the transport layer.

M

This information element is the GTP Tunnel Endpoint Identifier to be used for

>>GTP-TEID

the user plane transport between eNB and the serving gateway.

>> E-RAB Level QoS

M

Indicating the QoS information of an E-RAB.

O

Indicating whether the E-RAB needs to be forwarded

M

Indicating the forwarding of the container from the source eNodeB to

Parameters >>Data Forwarding Not Possible Source to Target Transparent Container

the target eNodeB

UE Security Capabilities

M

Indicating the UE security capabilities

Step 43 Upon receiving the HandoverRequest message, the target eNodeB evaluates the admission and sends a HandoverRequestAck message to the EPC, indicating the handover permission. IEs in the HandoverRequestAck message are listed in the following table:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name

Presence

1Typical Service Procedure

Semantics description

E-RABs Admitted List >E-RABs Admitted Item IEs >>E-RAB ID

M

>>Transport Layer Address

M

ERAB ID Indicating a transport layer address that the target eNodeB allocates to the E-RAB.

>>GTP-TEID

M

Indicating a GTPU TEID that the target eNodeB allocates to the ERAB.

>>DL Transport Layer

O

Indicating the address for forwarding downlink data

>>DL GTP-TEID

O

Indicating the GTPU TEID for forwarding downlink data.

>>UL Transport Layer

O

Indicating the address for forwarding uplink data.

O

Indicating the GTPU TEID for forwarding uplink data.

E-RABs Failed to Setup List

O

Indicating the ERAB that cannot be set up on the target eNodeB.

Target to Source Transparent

M

Indicating the handover command delivered by target eNodeB that

Address

Address >>UL GTP-TEID

Container

needs to be sent to the UE by the source eNodeB using a container

Step 44 Upon receiving the HandoverRequestAck message, the EPC sends a HandoverCommand message to request the source eNodeB to starts a handover. IEs in the HandoverCommand message are listed in the following table: IE/Group Name

Presence

Semantics description

E-RABs Subject to Forwarding List >E-RABs Subject to Forwarding Item IEs >>E-RAB ID

M

Indicating the ID of an E-RAB.

>>DL Transport Layer

O

Indicating the address for forwarding downlink data

>>DL GTP-TEID

O

Indicating the GTPU TEID for forwarding downlink data.

>>UL Transport Layer

O

Indicating the address for forwarding uplink data.

O

Indicating the GTPU TEID for forwarding uplink data.

O

Indicates the E-RABs to be released during the handover. Generally, its value

Address

Address >>UL GTP-TEID E-RABs to Release List

is 0. Target to Source Transparent Container

M

Indicating the handover command forwarded by the target eNodeB to the source eNodeB and then to the UE by using a container

Step 45 Upon receiving the HandoverCommand message, the source eNodeB sends it to the UE. Step 46 The UE accesses the target cell based on the information in the command. After a successful accessing, the UE sends a

60

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

RRCConnectionReconfigurationComplete message to the target eNodeB indicating the handover completion. Step 47 Upon receiving the RRCConnectionReconfigurationComplete message, the target eNodeB sends a HandoverNotify message to the EPC. IEs in the HandoverNotify message are listed in the following table: IE/Group Name

Presence

Semantics description

E-UTRAN CGI

M

Indicating the CGI of the cell that the UE hands over to

TAI

M

Indicating the TAI of the cell that the UE hands over to.

Step 48 Upon receiving the HandoverNotify message, the EPC sends a UEConextReleseCommand (cause = Successful Handover) message to the source eNodeB, indicating that the handover succeeds and the UE can be released on the source eNodeB.The source eNodeB releases the UE until local data transmission is completed. ----End

Traced messages during S1-based handover Message exchange over the Uu interface on the source eNodeB is shown in the following figure:

Message exchange over the S1 interface on the source eNodeB is shown in the following figure:

Message exchange over the Uu interface on the target eNodeB is shown in the following figure:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Message exchange over the S1 interface on the target eNodeB is shown in the following figure:

The content and key IEs in a RRC CON RECFG message are shown in the following figure:

1.1.9 Redirection Procedure Similar to a handover procedure, a redirection procedure starts from the eNodeB. The eNodeB delivers a measurement configuration to the UE and determines whether a redirection is needed based on the measurement result reported by the UE. The eNodeB also delivers a UE_CONTEXT_REL_REQ message to the EPC with an IE indicating the reason for the redirection. The EPC replies the request with a UE_CONTEXT_RELEASE_COMMOND message. The redirection succeeds with a UE_CONTEXT_RELEASE_COMPLETE message from the eNodeB. The

62

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

eNodeB determines the redirection method and the target cell for the redirection. It informs the UE of the frequency of the target cell with a RRCConnectionRelease message.

eNB

MME

UE CONTEXT RELEASE REQUEST

eNB

MME

UE CONTEXT RELEASE COMMAND

UE CONTEXT RELEASE COMPLETE

The content of the S1AP_UE_CONTEXT_REL_REQ message over the S1 interface is as follows: IE/Group Name

Presence

Range

IE type and

Semantics

reference

description

Criticality

Assigned Criticality

Message Type

M

9.2.1.1

YES

ignore

MME UE S1AP ID

M

9.2.3.3

YES

reject

eNB UE S1AP ID

M

9.2.3.4

YES

reject

Cause

M

9.2.1.3

YES

ignore

GW Context Release

O

9.2.1.84

YES

reject

Indication

The Cause IE is interRatRedirection. IEs in the S1AP_UE_CONTEXT_REL_REQ message are as follows:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IEs in the RRCConnectionRelease message over the S1 interface are as follows: IE/Group Name

Presence

Semantics description

releaseCause

M

Indicating the cause for RRC connection release

redirectedCarrierInfo

O

Indicating the target frequency for the UE redirection

64

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IMS-based SRVCC uses the IMS network to provide VoIP services. Due to the limitation of the coverage of the LTE network, IMS-based SRVCC can shift voice services to from the IMS domain to the CS domain in the GERAN or UMTS network. The following figure shows the network architecture of SRVCC.

65

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

SRVCC Structure between E-UTRAN and GERAN/UTRAN

The Sv interface is introduced to connect the MME to the MSC server which is improved to support SRVCC.

The protocol stack over the newly introduced Sv interface follows that over the S3 interface. The protocol stack is shown in the following figure:

Sv interface

66

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

1.1.9.1 UE Capability of SRVCC

Obtaining UE capability

The E-UTRAN sends a UECapabilityEnquiry message to the UE to obtain the UE capability information.The UE responses to the enquiry with a UECapabilityInformation message indicating whether the UE supports SRVCC.

67

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

The IE featureGroupIndicators in the RRC_UE_CAP_INFO message indicates the UE capability. The twenty-seventh bit in the IE indicates whether the UE supports SRVCC to UMTS and the ninth bit indicates whether the UE supports SRVCC to GERAN.

68

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

1.1.9.2 Procedure for SRVCC from E-UTRAN to GERAN without DTM support:

SRVCC from E-Utran to GERAN without DTM support process

The procedure shown in the preceding figure is one of the basic SRVCC procedures. Step 49 According to measurement configuration, the UE carries out an inter-RAT measurement and reports the measurement result. Step 50 Based on the measurement report from the UE and handover algorithms, the eNodeB determines whether to trigger an inter-RAT SRVCC handover.Based on SRVCC capability information of the UE and the MME in the S1 AP Initial Context Setup Request message, the eNodeB figures out that the UE is in voice service by identifying the voice bearer of QCI=1. Step 51 The eNodeB sends a Handover Required (including Target ID and generic Source to Target Transparent Container) message to the MME.The eNodeB adds an old BSS to new BSS IE in the generic Source to Target Transparent Container parameter to indicate that this is a handover to the CS domain. Step 52 According to the type of voice bearer voice bearer of QCI=1 and generic Container, the MME recognizes that this is an SRVCC handover. The MME

69

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

separates the voice bearer from the non-voice bearer and initiates a PS to CS handover. Step 53 It sends SRVCC PS to CS Request (including STN-SR, MSISDN, generic Source to Target Transparent Container, and MM Context) to the MSC SERVER.The MSC SERVER determines whether to trigger the handover based on the Target ID from the eNodeB.The MME obtains the STN-SR and MSISDN from the HSS when the UE is attaching to the E-UTRAN. The MM Context includes the CS security information of the UE.The CS security information of the UE is exported from the EPS security information. For details about the algorithm, see 3GPP TS33.401. Step 54 The handover between MSCs is completed by the interaction between the MSC SERVER and the target MSC. Step 55 The target MSC and target BSS allocate resources through handovers. Step 56 The target MSC sends a Prepare Handover Response message to the MSC SERVER indicating that the handover preparation at the target side is ready. Step 57 The CS link between the MSC SERVER and the target MSC is set up by the ISUP message. Step 58 The Session Transfer procedure is started with the ISUP IAM (STN-SR) message from the MSC SERVER to the IMS domain. For details, seeSession Transfer procedure. Step 59 The MSC SERVER sends an SRVCC PS to CS Response (Target to Source Transparent Container) to the MME. Step 60 The MME sends a Handover Command message (Target to Source Transparent Container) to the eNodeB. This message includes only voice bearer information. iThe eNodeB sends a Handover from E-UTRAN Command message to the UE and instructs the UE to handover afterwards. Step 61

The UE accesses the target GERAN.

Step 62

The target BSS detects the handover.

Step 63 The UE initiates a Suspend procedure.The MME retains the non-GBR of the UE and deactivates voice bearers. Step 64

The target BSS sends a Handover Complete message to the Target MSC.

Step 65 The target MSC sends an SES (Handover Complete) message to the MSC SERVER. Step 66 The MSC SERVER and the target MSC set up a voice bearer through an ISUP ANM message.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Step 67 The MSC SERVER sends an SRVCC PS to CS Complete Notification message to the MME to inform the MME that the UE has accessed the target GSM system. Step 68 After the CS service, the UE proceeds with the PS service that is suspended before through the RAU. ----End

IEs in this procedure differ from those in basic handovers in the S1AP_HANDOVER_REQUIRED message. Protocol IEs in this message are listed in the following table. HANDOVER REQUIRED IE/Group Name

Presence

Range

IE type and

Semantics

reference

description

Criticality

Assigned Criticality

Message Type

M

9.2.1.1

YES

reject

MME UE S1AP ID

M

9.2.3.3

YES

reject

eNB UE S1AP ID

M

9.2.3.4

YES

reject

Handover Type

M

9.2.1.13

YES

reject

Cause

M

9.2.1.3

YES

ignore

Target ID

M

9.2.1.6

YES

reject

Direct Forwarding Path

O

9.2.3.15

YES

ignore

SRVCC HO Indication

O

9.2.1.59

YES

reject

Source to Target Transparent

M

9.2.1.56

YES

reject

O

Source to Target

YES

reject

9.2.1.64

YES

reject

9.2.1.65

YES

ignore

Availability

Container Source to Target Transparent Container Secondary

Transparent Container 9.2.1.56

MS Classmark 2

CifSRVCCto GERAN

MS Classmark 3

CifSRVCCto GERAN

CSG Id

O

9.2.1.62

YES

reject

Cell Access Mode

O

9.2.1.74

YES

reject

PS Service Not Available

O

9.2.1.77

YES

ignore

Details about the SRVCC HO Indication IE are as follows:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name

Presence

Range

1Typical Service Procedure

IE type and

Semantics description

reference SRVCC HO Indication

M

ENUMERATED (PS and CS, CS only, …)

The SRVCC HO Indication IE indicates the service type, namely, a combination of PS and CS service or CS service only. Details about this indication in the protocol IE are as follows:

72

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

73

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

MS Classmark 2

C-

1Typical Service Procedure

9.2.1.64

YES

reject

9.2.1.65

YES

ignore

ifSRVCCto GERAN MS Classmark 3

CifSRVCCto GERAN

The preceding two IEs are mandatory if the Handover Type is set to LTEtoGERAN and the SRVCC HO Indication IE is included in the S1AP_HANDOVER_REQUIRED message.The GSM version, RF capability, and encryption algorithm of the UE are indicates by corresponding bit in the SRVCC HO

74

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Indication IE. For details about the SRVCC HO Indication IE, see 3GPP TS 48.008 and 3GPP TS

24.008.

75

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

1.1.10 ANR（Automatic Neighbour Relation） Automatic Neighbor Relation (ANR) refers to the automatic configuration of neighbor relationships. It facilitates manual operations of neighboring relationship configurations and reduces manpower cost.

The eNodeB or U2000 adds the unknown cell detected by the UE into the neighboring cell list. The U2000 also removes the neighboring cell that is invalid for a long time from the neighboring cell list. Currently, eNodeBs provided by Huawei support two types of ANRs, namely, event-trigged ANR and fast ANR. Event-triggered ANR

76

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

The event-triggered ANR is triggered if the UE is providing services properly and the eNodeB receives the measurement report of an unknown neighboring cell from the UE.After the evaluation based on a series of algorithms, this unknown cell is added into the neighboring cell list. The UE may initiate handovers to this cell afterwards. Fast ANR Different from the event-triggered ANR, in the fast ANR the eNodeB instructs the UE to search for unknown cells. The eNodeB reports the unknown cells searched by the UE to the U2000 who adds these cells into the neighboring cell list.

1.1.10.1 Intra-RAT event-triggered ANR procedure

Intra-RAT event-triggered ANR procedure is as follows: Step 69 figure.

The UE reports the unknown cells detected, as shown in the following

77

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Figure 1.1 UE report PCI of an unknown cell

Step 70 figure.

The eNodeB delivers CGI measurement, as shown in the following

78

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Figure 1.1 CGI measconfig：

Content of the ReportCGI IE in a RRC_CONN_RECFG message is described in the following figure.

79

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Conditional presence reportCGI

1Typical Service Procedure

Explanation The field is optional, need OR, in case purpose is included and set to reportCGI; otherwise the field is not present.

Figure 1.2 UE report CGI of unknown cell：

-- ASN1START

CellGlobalIdEUTRA ::=

SEQUENCE {

plmn-Identity

PLMN-Identity,

cellIdentity

CellIdentity

}

-- ASN1STOP

80

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

CellGlobalIdEUTRA field descriptions cellIdentity Identity of the cell within the context of the PLMN. plmn-Identity Identifies the PLMN of the cell as given by the first PLMN entry in the plmn-IdentityList in SystemInformationBlockType1.

----End

1.1.10.2 Inter-RAT event-triggered ANR procedure The inter-RAT event-triggered ANR differs from the intra-RAT ANR in delivering the event B1 measurement and requesting for reporting cells with the strongest signal.

81

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

-- ASN1START

ReportConfigInterRAT ::= triggerType

SEQUENCE { CHOICE {

event

SEQUENCE {

eventId

CHOICE {

eventB1

SEQUENCE {

b1-Threshold

CHOICE {

b1-ThresholdUTRA

ThresholdUTRA,

b1-ThresholdGERAN

ThresholdGERAN,

b1-ThresholdCDMA2000

ThresholdCDMA2000

} }, eventB2

SEQUENCE {

b2-Threshold1

ThresholdEUTRA,

b2-Threshold2

CHOICE {

b2-Threshold2UTRA

ThresholdUTRA,

82

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

b2-Threshold2GERAN

ThresholdGERAN,

b2-Threshold2CDMA2000

ThresholdCDMA2000

} }, ... }, hysteresis

Hysteresis,

timeToTrigger

TimeToTrigger

}, periodical

SEQUENCE {

purpose

ENUMERATED { reportStrongestCells, reportStrongestCellsForSON, reportCGI}

} }, maxReportCells

INTEGER (1..maxCellReport),

reportInterval

ReportInterval,

reportAmount

ENUMERATED {r1, r2, r4, r8, r16, r32, r64,

infinity},

The rest is similar to the intra-RAT ANR.

1.1.10.3 Intra-RAT ANR procedure As mentioned above, in the fast ANR, the UE detects unknown cells actively. The eNodeB actively delivers measurement configuration to instruct the UE to measure unknown cells if the UE is connected to the eNodeB. However, in the event-triggered ANR the eNodeB delivers the measurement configuration only after the UE has detected unknown cells. Intra-RAT ANR procedure is shown in the following figure:

83

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.10.4 Inter-RAT fast ANR procedure Inter-RAT fast ANR procedure is shown in the following figure:

84

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

1.1.11 MRO Algorithm Procedure The MRO collects causes for handover failures based on algorithm to modify handover parameters. This facilitates self-optimization of the network.

Intra-RAT intra-frequency handover is taken as an example. The formula for triggering of intra-frequency handover (event A3) is as follows: Mn  Ofn  Ocn  Hys  Ms  Ofs  Ocs  Off

Where Mn refers to value of RSRP or RSRQ in the measurement results of neighboring cells; Ofn refers to the frequency offset value; Ocn refers to the offset value of the neighboring cells and is configured in the neighbor relationship configuration; Ms refers to the value of RSRP or RSRQ in the measurement results of serving cells; Ofs refers to the offset value of the serving frequency; Ocs refers to the offset value of serving cells; Hys refers to the hysteresis parameter which is closely related to service features and moving speeds. This parameter is to reduce the probability of ping-pong handovers. MRO algorithm facilitates self-optimization of the network by configuring the Ocn parameter.

85

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

If the UE-initiate handover fails, it returns to the source cell. The MRO calculates this failed handover as a premature handover. A delayed handover is shown in the following figure. The service drop occurs when the UE is in Cell 0 and then the UEReestablishes in the target cell (Cell 1), as shown in the following figure.

86

1Typical Service Procedure

HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

The MRO algorithms are modified based on the number of premature handovers and delayed handovers and the corresponding neighboring cell distribution.。

1.1.12 CSFB Procedure from LTE to UMTS (L2U PSHO) A CSFB procedure is trigged by a CS Fallback Indicator IE in INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages. Related IEs in the INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages are listed in the following table. IE/Group Name CS Fallback Indicator

Presence O

Semantics description Indicating that the CSFB is trigged and the values include CS Fallback required and CS Fallback High Priority.

Registered LAI

O

Indicating the preferential target areas for fallback PLMN and LAC. If LAI is identified by the eNodeB and the LAI is supported by the eNodeB, target cells with the same PLMN and LAC are preferred. Otherwise, target cells with the same PLMN are chosen. Other target cells are chosen only if preceding two conditions are not met.

Types of LTE to UMTS CSFB includes:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

LTE to UMTS PS Handover LTE to UMTS redirection

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1.1.12.1 LTE to UMTS PS handover

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Step 71 The PS handover among UMTS systems can be trigged either by the event B1 measurement report by the UE or by the CSFB Indicator IE in the INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages. The source eNodeB sends a HANDOVER REQUIRED message to the EPC.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Explanation of the HANDOVER REQUIRED message is as follows:

IEs in the HANDOVER REQUIRED message are listed in the following table:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name Handover Type

Presence M

Semantics description Indicating whether it is an intra-RAT handover or an inter-RAT handover

Cause

M

Indicating the cause for handovers, such as the CSFB

Target ID

M

Indicating the ID of the target NE. For an intra-RAT handover, the target NE is an eNodeB. For an inter-RAT handover, the target ID is the ID of the NE in the target system, such as the RNC or CGI.

Source to Target

M

Transparent Container

Indicating the RRC layer configurations of the UE transmitted using a container.

Step 72 The eNodeB starts the handover after it receives a HandoverCommand message from the EPC.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Explanation of the HandoverCommand message is as follows:

IEs in the HandoverCommand message are listed in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name MME UE S1AP ID

Presence

1Typical Service Procedure

Semantics description

M

Indicating a new UE S1AP ID the MME allocates to the UE

Handover Type

M

Indicating whether it is an intra-RAT handover or an inter-RAT handover

NAS Security Parameters

C

from E-UTRAN

Indicating the NAS security parameters from the EUTRAN

E-RABs To Be Setup List

Indicating the E-RABs to be set up by the target eNodeB

>E-RABs To Be Setup Item IEs >>E-RAB ID

M

Indicating the ID of an E-RAB.

>>Transport Layer

O

Indicating the transport layer address allocated to the E-

Address

RAB

>>GTP-TEID

O

Indicates a GTPU TEID on the transport layer allocated to the ERAB

Source to Target

M

Transparent Container

Indicating the encapsulated container by the target eNodeB or the target system and the container is transparently transmitted to the UE by the source eNodeB

Step 73 UE.

The source eNodeB sends a MobilityFromEUTRACommand message to the

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Explanation of the MobilityFromEUTRACommand message is as follows:

IEs in the MobilityFromEUTRACommand message are as follows: IE/Group Name cs-FallbackIndicator

Presence

Semantics description

C

Indicating whether it is a handover triggered by the CSFB

targetRAT-Type

M

Indicating the type of the target RAT

targetRAT-

M

Indicating the target RAT. This IE needs to be

MessageContainer

incorporated into a handover command. Parameters for this handover command include target cell identity and radio parameters. These parameters need to be filled by the target eNodeB and be encoded into a Uu-interface message which is transparently transmitted to the UE.

nas-

O

SecurityParamFromEUTR

Indicating the NAS security parameter from the EUTRAN

A

Step 74 The UE accesses the target eNodeB according to the configuration included in the handover command. The UE informs the eNodeB of the reconfiguration completion, indicating that the handover is completed.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Step 75 The UE sends a UE CONTEXT RELEASE COMMAND message indicating causes for the release to instruct the eNodeB to release the UE context. For example, if the cause value is Successful Handover, the eNodeB can remove the information of the UE. ----End

1.1.12.2 LTE to UMTS Redirection The CSFB is triggered by a CS Fallback Indicator IE in INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages. The eNodeB determines the type and target cell for redirection and informs the UE of the frequency of the target cell through a RRCConnectionRelease message. IEs in the RRCConnectionRelease message are listed in the following table. IE/Group Name

Presence

Semantics description

releaseCause

M

Indicating the cause for releasing RRC connections

redirectedCarrierInfo

O

Indicating the target frequency for the UE redirection

IEs in the RRCConnectionRelease message are as follows:

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.13 CSFB from LTE to GERAN (L2G PSHO) A CSFB procedure is trigged by a CS Fallback Indicator IE in INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages. CSFB-related IEs in INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages are as follows. IE/Group Name CS Fallback Indicator

Presence

Semantics description

O

Indicating that the CSFB is trigged and values includes CS Fallback required and CS Fallback High Priority.

Registered LAI

O

Indicating the target area for the fallback

Types of CSFB from LTE to GERAN include:  LTE to GERAN PS Handover  LTE to GERAN CCO  LTE to GERAN Redirection

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.13.1 LTE to GERAN PSHO

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Procedure for LTE to GERAN PSHO is as follows:

Step 76 PS handover is triggered either by event B1 reported by the UE or the CSFB Indicator IE in the INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Explanation of the HANDOVER REQUIRED message is as follows:

Main IEs in the HANDOVER REQUIRED message are listed in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name Handover Type

Presence M

1Typical Service Procedure

Semantics description Indicating whether the handover is an intra-RAT handover or an inter-RAT one

Cause

M

Indicating the cause for the handover, such CSFB

Target ID

M

Indicating the ID of the target NE. For an intra-RAT handover, the target NE is an eNodeB. For an inter-RAT handover, the target ID is the ID of the NE in the target system, such as the RNC or CGI.

Source to Target

M

Transparent Container

Indicating the RRC layer configurations of the UE transmitted by a container.

Step 77 The eNodeB starts the handover after receiving the HandoverCommand message from the EPC.

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Explanation of the HandoverCommand message is as follows:

Handover-related IEs in the HandoverCommand message are listed in the following table.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

IE/Group Name MME UE S1AP ID

Presence

1Typical Service Procedure

Semantics description

M

Indicating a new UE S1AP ID the MME allocates to the UE

Handover Type

M

Indicating whether the handover type is an intra-RAT handover or an inter-RAT one

NAS Security Parameters

C

from E-UTRAN

Indicating the NAS security parameters from the EUTRAN

E-RABs To Be Setup List

Indicating the E-RABs to be set up by the target eNodeB

>E-RABs To Be Setup Item IEs >>E-RAB ID

M

Indicating the ID of an E-RAB.

>>Transport Layer

O

Indicating the transport layer address allocated to the E-

Address

RAB

>>GTP-TEID

O

Indicating the GTPU TEID of the transport layer allocated to the E-RAB

Source to Target

M

Transparent Container

Indicating the container encapsulated by the target eNodeB or RAT. This container is transparently transmitted to the UE by the source eNodeB

Step 78 UE.

The source eNodeB sends MobilityFromEUTRACommand message to the

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Explanation of the MobilityFromEUTRACommand is as follows:

Handover-related IEs in the MobilityFromEUTRACommand message are listed in the following table. IE/Group Name cs-FallbackIndicator

Presence

Semantics description

C

Indicating whether the handover is triggered by the CSFB

targetRAT-Type

M

Indicating the target RAT for the handover

targetRAT-

M

Indicating the target RAT. This IE needs to be

MessageContainer

incorporated into a handover command. Parameters for this handover command include target cell identity and radio parameters. These parameters need to be filled by the target eNodeB and be encoded into a Uu-interface message which is transparently transmitted to the UE.

nas-

O

SecurityParamFromEUTR

Indicating the NAS security parameter form the EUTRAN

A

Step 79 The UE accesses the target eNodeB according to the configuration included in the handover command. The UE informs the eNodeB of the reconfiguration completion, indicating that the handover is completed. Step 80 The UE sends a UE CONTEXT RELEASE COMMAND message indicating causes for the release to instruct the eNodeB to release the UE context.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

For example, if the cause value is Successful Handover, the eNodeB can remove the information of the UE. ----End

1.1.13.2 LTE to GERAN CCO A CSFB procedure is trigged by a CS Fallback Indicator IE in INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages. The eNodeB determines the type and target cell of the LTE to GERAN CCO and delivers the information of the target cell to the UE through a MobilityFromEUTRACommand message.

CCO-related IEs in the MobilityFromEUTRACommand message are listed in the following table. IE/Group Name cs-FallbackIndicator t304

Presence

Semantics description

C

Indicating whether the CCO is triggered by the CSFB

T

A timer that instructs reestablishment if the CCO times out

targetRAT-Type

M

Indicating the target RAT for the handover, including the ID and frequency of physical cells.

Explanation of the MobilityFromEUTRACommand message is as follows.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.13.3 LTE to GERAN Redirection A CSFB procedure is trigged by a CS Fallback Indicator IE in INITIAL CONTEXT SETUP REQUEST and UE CONTEXT MODIFICATION REQUEST messages. The eNodeB determines the type and target cell of the LTE to GERAN CCO and delivers the information of the target cell to the UE through a RRCConnectionRelease message. Redirection-related IEs in the RRCConnectionRelease message are listed in the following table. IE/Group Name releaseCause redirectedCarrierInfo

Presence

Semantics description

M

Indicating the cause for RRC connection release

O

Indicating the target frequency for the redirection

Explanation of the RRCConnectionRelease message is as follows.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1.1.14 X2 Self-Setup Procedure This section describers an X2 self-setup procedure. An X2 self-setup can be achieved either over the S1 interface or over the U2000.The X2 self-setup method can be viewed by running the LST GLOBALPROCSWITCH command and be modified by the MOD GLOBALPROCSWITCH command, as shown in the following figure.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

Dialog box for viewing X2 self-setup method

Dialog box for modifying X2 self-setup methods

1.1.14.1 X2 Self-Setup over the U2000 The eNodeB facilitates the X2 self-setup through the following parameters, namely, X2ENodeB, X2SIGIP, and X2ServIP. An X2 self-setup procedure is shown in the following figure.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Step 81 The UE hands over between two eNodeBs and triggers an X2 self-setup. Step 82 If the peer X2 is detected as unavailable by the source eNodeB, the source eNodeB sends an X2 self-setup request to the OSS. Step 83 The OSS queries the X2SIGIP and X2ServIP of both the source and target eNodeB in the database. Step 84 The OSS combines the information queried into the X2eNodeB, and delivers the X2eNodeB as a configuration file to both the source and target eNodeBs. Step 85 The eNodeBs perform X2eNodeB configurations based on the received file and automatically set up signaling links and service links. ----End

1.1.14.2 X2 Self-Setup over the S1 interface An S1-based handover triggers an X2 self-setup. Step 1 The X2 link is preferred by the handover. If the X2 link is detected to be unavailable by the Uealg module, an X2 self-setup is triggered. Step 86 The eNodeB1 requests for local information from the transceiver module (TRM). Step 87 After obtaining the local information from the TRM , the eNodeB1 requests for the information of the peer eNodeB2 from the MME through S1ITF.

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HUAWEI LTE EUTRAN 协议与信令分析 信令流程

1Typical Service Procedure

Step 88 After receiving the request from the eNodeB1, the eNodeB2 requests for local information from the TRM. Step 89 The TRM combines the X2SIGIP and X2ServIP information of the source eNodeB1 and the information with the local X2SIGIP and X2ServIP information into the X2ENodeB information. The TRM performs X2eNodeB configurations based on the X2ENodeB information and establishes signaling links and service links.In response to the request from the eNodeB1, the eNodeB2 sends the local information obtained from the TRM to the eNodeB1. Step 90 The eNodeB1 combines the X2SIGIP and X2ServIP information of the peer part and itself into the X2ENodeB information in the TRM. The eNodeB1 performs X2eNodeB configurations based on the X2ENodeB information and establishes signaling links and service links. The procedure for X2 self-setup over the S1 interface can be known through tracing the signaling between the two eNodeBs. After the signaling exchange for the S1 self-setup, the X2 link requests for setup. If the request is responded by the peer part, the X2 self-setup succeeds. ----End

The traced messages of signaling over the S1 interface are shown in the

preceding figure. The traced message of signaling over the X2 link is shown in the following figure.

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