Foreword................................................................................................................................................ 6

1....... Scope........................................................................................................................................... 7

2....... References.................................................................................................................................... 7

3....... Definitions, symbols and abbreviations........................................................................................... 8

3.1......... Definitions............................................................................................................................................................................ 8

3.2......... Symbols................................................................................................................................................................................ 8

3.3......... Abbreviations....................................................................................................................................................................... 8

4....... General......................................................................................................................................... 9

4.1......... Procedure specification principles................................................................................................................................... 9

4.2......... Forwards and backwards compatibility........................................................................................................................... 9

4.3......... Specification notations....................................................................................................................................................... 9

5....... X2AP services............................................................................................................................ 10

5.1......... X2AP procedure modules............................................................................................................................................... 10

5.2......... Parallel transactions.......................................................................................................................................................... 10

6....... Services expected from signalling transport................................................................................... 10

7....... Functions of X2AP...................................................................................................................... 10

8....... X2AP procedures........................................................................................................................ 11

8.1......... Elementary procedures.................................................................................................................................................... 11

8.2......... Basic mobility procedures............................................................................................................................................... 11

8.2.1........... Handover Preparation................................................................................................................................................ 11

8.2.1.1.............. General................................................................................................................................................................... 11

8.2.1.2.............. Successful Operation........................................................................................................................................... 12

8.2.1.3.............. Unsuccessful Operation...................................................................................................................................... 13

8.2.1.4.............. Abnormal Conditions.......................................................................................................................................... 13

8.2.2........... SN Status Transfer.................................................................................................................................................... 14

8.2.2.1.............. General................................................................................................................................................................... 14

8.2.2.2.............. Successful Operation........................................................................................................................................... 14

8.2.2.3.............. Abnormal Conditions.......................................................................................................................................... 14

8.2.3........... UE Context Release................................................................................................................................................... 14

8.2.3.1.............. General................................................................................................................................................................... 14

8.2.3.2.............. Successful Operation........................................................................................................................................... 15

8.2.3.3.............. Unsuccessful Operation...................................................................................................................................... 15

8.2.3.4.............. Abnormal Conditions.......................................................................................................................................... 15

8.2.4........... Handover Cancel........................................................................................................................................................ 15

8.2.4.1.............. General................................................................................................................................................................... 15

8.2.4.2.............. Successful Operation........................................................................................................................................... 15

8.2.4.3.............. Unsuccessful Operation...................................................................................................................................... 16

8.2.4.4.............. Abnormal Conditions.......................................................................................................................................... 16

8.3......... Global Procedures............................................................................................................................................................ 16

8.3.1........... Load Indication.......................................................................................................................................................... 16

8.3.1.1.............. General................................................................................................................................................................... 16

8.3.1.2.............. Successful Operation........................................................................................................................................... 16

8.3.1.3.............. Unsuccessful Operation...................................................................................................................................... 17

8.3.1.4.............. Abnormal Conditions.......................................................................................................................................... 17

8.3.2........... Error Indication........................................................................................................................................................... 17

8.3.2.1.............. General................................................................................................................................................................... 17

8.3.2.2.............. Successful Operation........................................................................................................................................... 17

8.3.2.3.............. Unsuccessful Operation...................................................................................................................................... 17

8.3.2.4.............. Abnormal Conditions.......................................................................................................................................... 17

8.3.3........... X2 Setup....................................................................................................................................................................... 17

8.3.3.1.............. General................................................................................................................................................................... 17

8.3.3.2.............. Successful Operation........................................................................................................................................... 17

8.3.3.3.............. Unsuccessful Operation...................................................................................................................................... 18

8.3.3.4.............. Abnormal Conditions.......................................................................................................................................... 18

8.3.4........... Reset............................................................................................................................................................................. 19

8.3.4.1.............. General................................................................................................................................................................... 19

8.3.4.2.............. Successful Operation........................................................................................................................................... 19

8.3.4.3.............. Unsuccessful Operation...................................................................................................................................... 19

8.3.4.4.............. Abnormal Conditions.......................................................................................................................................... 19

8.3.5........... eNB Configuration Update....................................................................................................................................... 19

8.3.5.1.............. General................................................................................................................................................................... 19

8.3.5.2.............. Successful Operation........................................................................................................................................... 19

8.3.5.3.............. Unsuccessful Operation...................................................................................................................................... 21

8.3.5.4.............. Abnormal Conditions.......................................................................................................................................... 21

8.3.6........... Resource Status Reporting Initiation..................................................................................................................... 21

8.3.6.1......... General......................................................................................................................................................................... 21

8.3.6.2......... Successful Operation................................................................................................................................................. 21

8.3.6.3.............. Unsuccessful Operation...................................................................................................................................... 22

8.3.6.4......... Abnormal Conditions................................................................................................................................................. 22

8.3.7........... Resource Status Reporting........................................................................................................................................ 22

8.3.7.1.............. General................................................................................................................................................................... 22

8.3.7.2.............. Successful Operation........................................................................................................................................... 23

9....... Elements for X2AP Communication............................................................................................. 23

9.0......... General................................................................................................................................................................................ 23

9.1......... Message Functional Definition and Content................................................................................................................ 23

9.1.1........... Messages for Basic Mobility Procedures............................................................................................................... 23

9.1.1.1.............. HANDOVER REQUEST................................................................................................................................... 23

9.1.1.2.............. HANDOVER REQUEST ACKNOWLEDGE............................................................................................... 25

9.1.1.3.............. HANDOVER PREPARATION FAILURE..................................................................................................... 25

9.1.1.4.............. SN STATUS TRANSFER.................................................................................................................................. 26

9.1.1.5.............. UE CONTEXT RELEASE................................................................................................................................. 27

9.1.1.6.............. HANDOVER CANCEL..................................................................................................................................... 28

9.1.2........... Messages for global procedures............................................................................................................................... 28

9.1.2.1.............. LOAD INFORMATION..................................................................................................................................... 28

9.1.2.2.............. ERROR INDICATION....................................................................................................................................... 28

9.1.2.3.............. X2 SETUP REQUEST........................................................................................................................................ 39

9.1.2.4.............. X2 SETUP RESPONSE...................................................................................................................................... 39

9.1.2.5.............. X2 SETUP FAILURE......................................................................................................................................... 40

9.1.2.6.............. RESET REQUEST.............................................................................................................................................. 40

9.1.2.7.............. RESET RESPONSE............................................................................................................................................ 41

9.1.2.8.............. ENB CONFIGURATION UPDATE................................................................................................................ 41

9.1.2.9.............. ENB CONFIGURATION UPDATE ACKNOWLEDGE............................................................................ 43

9.1.2.10............ ENB CONFIGURATION UPDATE FAILURE............................................................................................ 43

9.1.2.11............ RESOURCE STATUS REQUEST................................................................................................................... 43

9.1.2.12............ RESOURCE STATUS RESPONSE................................................................................................................. 44

9.1.2.13............ RESOURCE STATUS FAILURE.................................................................................................................... 45

9.1.2.14............ RESOURCE STATUS UPDATE..................................................................................................................... 45

9.2......... Information Element definitions.................................................................................................................................... 45

9.2.0........... General......................................................................................................................................................................... 45

9.2.1........... GTP Tunnel Endpoint................................................................................................................................................ 46

9.2.2........... Trace Activation......................................................................................................................................................... 46

9.2.3........... Handover Restriction List......................................................................................................................................... 48

9.2.4........... PLMN Identity............................................................................................................................................................ 48

9.2.5........... DL Forwarding............................................................................................................................................................ 49

9.2.6........... Cause............................................................................................................................................................................ 49

9.2.7........... Criticality Diagnostics............................................................................................................................................... 53

9.2.8........... Served Cell Information............................................................................................................................................ 53

9.2.9........... E-RAB Level QoS Parameters................................................................................................................................. 55

9.2.10.......... GBR QoS Information............................................................................................................................................... 55

9.2.11.......... Bit Rate......................................................................................................................................................................... 56

9.2.12.......... UE Aggregate Maximum Bit Rate.......................................................................................................................... 56

9.2.13.......... Message Type.............................................................................................................................................................. 56

9.2.14.......... ECGI............................................................................................................................................................................. 57

9.2.15.......... COUNT Value............................................................................................................................................................ 57

9.2.16.......... GUMMEI..................................................................................................................................................................... 57

9.2.17.......... UL Interference Overload Indication...................................................................................................................... 58

9.2.18.......... UL High Interference Indication.............................................................................................................................. 58

9.2.19.......... Relative Narrowband Tx Power (RNTP)............................................................................................................... 58

9.2.20.......... GU Group Id................................................................................................................................................................ 59

9.2.21.......... Location Reporting Information.............................................................................................................................. 59

9.2.22.......... Global eNB ID............................................................................................................................................................ 59

9.2.23.......... E-RAB ID.................................................................................................................................................................... 60

9.2.24.......... eNB UE X2AP ID...................................................................................................................................................... 60

9.2.25.......... Subscriber Profile ID for RAT/Frequency priority.............................................................................................. 60

9.2.26.......... EARFCN...................................................................................................................................................................... 60

9.2.27.......... Transmission Bandwidth........................................................................................................................................... 61

9.2.28.......... E-RAB List.................................................................................................................................................................. 61

9.2.29.......... UE Security Capabilities........................................................................................................................................... 61

9.2.30.......... AS Security Information........................................................................................................................................... 62

9.2.31.......... Allocation and Retention Priority............................................................................................................................ 62

9.2.32.......... Time to Wait................................................................................................................................................................ 63

9.2.33.......... SRVCC Operation Possible...................................................................................................................................... 63

9.2.34.......... Hardware Load Indicator.......................................................................................................................................... 63

9.2.35.......... S1 TNL Load Indicator............................................................................................................................................. 63

9.2.36.......... Load Indicator............................................................................................................................................................. 63

9.2.37.......... Radio Resource Status............................................................................................................................................... 63

9.2.38.......... UE History Information............................................................................................................................................. 64

9.2.39.......... Last Visited Cell Information................................................................................................................................... 64

9.2.40.......... Last Visited E-UTRAN Cell Information.............................................................................................................. 64

9.2.41.......... Last Visited GERAN Cell Information.................................................................................................................. 65

9.2.42.......... Cell Type...................................................................................................................................................................... 65

9.2.43.......... Number of Antenna Ports......................................................................................................................................... 65

9.3......... Message and Information Element Abstract Syntax (with ASN.1)......................................................................... 66

9.3.1........... General......................................................................................................................................................................... 66

9.3.2........... Usage of Private Message Mechanism for Non-standard Use........................................................................... 66

9.3.3........... Elementary Procedure Definitions.......................................................................................................................... 66

9.3.4........... PDU Definitions......................................................................................................................................................... 71

9.3.5........... Information Element definitions.............................................................................................................................. 84

9.3.6........... Common definitions................................................................................................................................................ 101

9.3.7........... Constant definitions................................................................................................................................................. 102

9.3.8........... Container definitions............................................................................................................................................... 105

9.4......... Message transfer syntax................................................................................................................................................ 109

9.5......... Timers............................................................................................................................................................................... 109

10..... Handling of unknown, unforeseen and erroneous protocol data.................................................... 109

Annex A (informative):....... Change History.................................................................................... 110

 

This Technical Specification has been produced by the 3^rd Generation Partnership Project (3GPP).

The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:

Version x.y.z

where:

x    the first digit:

1    presented to TSG for information;

2    presented to TSG for approval;

3    or greater indicates TSG approved document under change control.

y    the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.

z    the third digit is incremented when editorial only changes have been incorporated in the document.

The present document specifies the radio network layer signalling procedures of the control plane between eNBs in E-UTRAN. X2AP supports the functions of X2 interface by signalling procedures defined in this document. X2AP is developed in accordance to the general principles stated in [2] and [3].

 

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.

·       References are either specific (identified by date of publication, edition number, version number, etc.) or non‑specific.

·       For a specific reference, subsequent revisions do not apply.

·       For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.

[1]                          3GPP TR 21.905: "Vocabulary for 3GPP Specifications".

[2]                          3GPP TS 36.401:  "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Architecture Description".

[3]                          3GPP TS 36.420:  "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 General Aspects and Principles".

 [4]                         3GPP TS 36.413:  " Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP)".

[5]                          ITU-T Recommendation X.691 (07/2002): "Information technology - ASN.1 encoding rules - Specification of Packed Encoding Rules (PER) ".

[6]                          3GPP TS 32.422:  "Telecommunication Management; Subscriber and Equipment Trace; Trace Control and Configuration Management".

[7]                          3GPP TS 32.421: "Telecommunication Management; Subscriber and Equipment Trace; Trace concepts and requirements".

[8]                          3GPP TS 36.424: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 data transport".

[9]                          3GPP TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRAN); Radio Resource Control (RRC) Protocol Specification".

[10]                        3GPP TS 36.211: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation".

[11]                        3GPP TS 36.213: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ".

[12]                        3GPP TS 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".

[13]                        3GPP TS 23.203: "Policy and charging control architecture".

[14]                        3GPP TS 24.301: "Non-Access-Stratum (NAS) protocol for Evolved Packet System; Stage 3".

[15]                        3GPP TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA), Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; stage 2".

[16]                        3GPP TS 36.104: " Base Station (BS) radio transmission and reception ".

[17]                        3GPP TS 24.008: "Mobile Radio Interface Layer 3 Specification; Core Network Protocols; Stage 3".

[18]                        3GPP TS 33.401: "Security architecture".

[19]                        3GPP TS 36.414: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 data transport".

[20]                        3GPP TS 23.216: "Single Radio Voice Call Continuity (SRVCC)".

[21]                        3GPP TS 36.422: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 signaling transport".

[22]                        3GPP TS 36.314: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Layer 2 - Measurements".

[23]                        3GPP TS 23.203: " Policy and charging control architecture".

[24]                        3GPP TS 25.413: "UTRAN Iu interface RANAP signalling"

3.1        Definitions

For the purposes of the present document, the terms and definitions given in [1] and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in [1].

Elementary Procedure: X2AP protocol consists of Elementary Procedures (EPs). An X2AP Elementary Procedure is a unit of interaction between two eNBs. An EP consists of an initiating message and possibly a response message. Two kinds of EPs are used:

-     Class 1: Elementary Procedures with response (success or failure),

-     Class 2: Elementary Procedures without response.

E-RAB: Defined in [2].

3.2        Symbols

For the purposes of the present document, the following symbols apply:

<symbol>             <Explanation>

 

3.3        Abbreviations

For the purposes of the present document, the abbreviations given in [1] and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in [1].

DL                          Downlink

EARFCN              E-UTRA Absolute Radio Frequency Channel Number

eNB                       E-UTRAN NodeB

EP                          Elementary Procedure

EPC                       Evolved Packet Core

E-RAB                  E-UTRAN Radio Access Bearer

E-UTRAN             Evolved UTRAN

GUMMEI             Globally Unique MME Identifier

HFN                       Hyper Frame Number

IE                           Information Element

MME                     Mobility Management Entity

PDCP                     Packet Data Convergence Protocol

PLMN                   Public Land Mobile Network

S-GW                     Serving Gateway

SN                          Sequence Number

TAC                       Tracking Area Code

UE                          User Equipment

UL                          Uplink

4.1        Procedure specification principles

The principle for specifying the procedure logic is to specify the functional behaviour of the terminating eNB exactly and completely. Any rule that specifies the behaviour of the originating eNB shall be possible to be verified with information that is visible within the system.

The following specification principles have been applied for the procedure text in clause 8:

-     The procedure text discriminates between:

1)   Functionality which "shall" be executed

      The procedure text indicates that the receiving node "shall" perform a certain function Y under a certain condition. If the receiving node supports procedure X but cannot perform functionality Y requested in the initiating message of a Class 1 EP, the receiving node shall respond with the message used to report unsuccessful outcome for this procedure, containing an appropriate cause value.

2)   Functionality which "shall, if supported" be executed

      The procedure text indicates that the receiving node "shall, if supported," perform a certain function Y under a certain condition. If the receiving node supports procedure X, but does not support functionality Y, the receiving node shall proceed with the execution of the EP, possibly informing the requesting node about the not supported functionality.

-     Any required inclusion of an optional IE in a response message is explicitly indicated in the procedure text. If the procedure text does not explicitly indicate that an optional IE shall be included in a response message, the optional IE shall not be included. For requirements on including Criticality Diagnostics IE, see section 10.

4.2        Forwards and backwards compatibility

The forwards and backwards compatibility of the protocol is assured by a mechanism where all current and future messages, and IEs or groups of related IEs, include ID and criticality fields that are coded in a standard format that will not be changed in the future. These parts can always be decoded regardless of the standard version.

4.3        Specification notations

For the purposes of the present document, the following notations apply:

Procedure             When referring to an elementary procedure in the specification the Procedure Name is written with the first letters in each word in upper case characters followed by the word "procedure", e.g. Handover Preparation procedure.

Message                When referring to a message in the specification the MESSAGE NAME is written with all letters in upper case characters followed by the word "message", e.g. HANDOVER REQUEST message.

IE                           When referring to an information element (IE) in the specification the Information Element Name is written with the first letters in each word in upper case characters and all letters in Italic font followed by the abbreviation "IE", e.g. E-RAB ID IE.

Value of an IE     When referring to the value of an information element (IE) in the specification the "Value" is written as it is specified in sub clause 9.2 enclosed by quotation marks, e.g. "Value".

The present clause describes the services an eNB offers to its neighbours.

5.1        X2AP procedure modules

The X2 interface X2AP procedures are divided into two modules as follows:

1.   X2AP Basic Mobility Procedures;

2.   X2AP Global Procedures;

The X2AP Basic Mobility Procedures module contains procedures used to handle the UE mobility within E-UTRAN.

The Global Procedures module contains procedures that are not related to a specific UE. The procedures in this module are in contrast to the above module involving two peer eNBs.

5.2        Parallel transactions

Unless explicitly indicated in the procedure specification, at any instance in time one protocol peer shall have a maximum of one ongoing X2AP procedure related to a certain UE.

The signalling connection shall provide in sequence delivery of X2AP messages. X2AP shall be notified if the signalling connection breaks.

X2 signalling transport is described in [21].

The X2AP protocol provides the following functions:

-     Mobility Management. This function allows the eNB to move the responsibility of a certain UE to another eNB. Forwarding of user plane data, Status Transfer and UE Context Release function are parts of the mobility management.

-     Load Management. This function is used by eNBs to indicate resource status, overload and traffic load to each other.

-     Reporting of General Error Situations. This function allows reporting of general error situations, for which function specific error messages have not been defined.

-     Resetting the X2. This function is used to reset the X2 interface.

-     Setting up the X2. This function is used to exchange necessary data for the eNB for setup the X2 interface and implicitly perform an X2 Reset.

-     eNB Configuration Update. This function allows updating of application level data needed for two eNBs to interoperate correctly over the X2 interface.

The mapping between the above functions and X2 EPs is shown in the table below.

Table 7-1: Mapping between X2AP functions and X2AP EPs

Function	Elementary Procedure(s)
Mobility Management	a) Handover Preparation b) SN Status Transfer c) UE Context Release d) Handover Cancel
Load Management	a) Load Indication b) Resource Status Reporting Initiation c) Resource Status Reporting
Reporting of General Error Situations	Error Indication
Resetting the X2	Reset
Setting up the X2	X2 Setup
eNB Configuration Update	eNB Configuration Update

 

8.1        Elementary procedures

In the following tables, all EPs are divided into Class 1 and Class 2 EPs.

Table 8.1-1: Class 1 Elementary Procedures

 

Table 8.1-2: Class 2 Elementary Procedures

 

8.2        Basic mobility procedures

8.2.1       Handover Preparation

8.2.1.1            General

This procedure is used to establish necessary resources in an eNB for an incoming handover.

The procedure uses UE-associated signalling.

8.2.1.2            Successful Operation

Figure 8.2.1.2-1: Handover Preparation, successful operation

The source eNB initiates the procedure by sending the HANDOVER REQUEST message to the target eNB. When the source eNB sends the HANDOVER REQUEST message, it shall start the timer T_RELOCprep.

The allocation of resources according to the values of the Allocation and Retention Priority IE shall follow the principles described for the E-RAB Setup procedure in [4].

The source eNB may include in the GUMMEI IE any GUMMEI corresponding to the source MME node.

If at least one of the requested non-GBR E-RABs is admitted to the cell indicated by the Target Cell ID IE, the target eNB shall reserve necessary resources, and send the HANDOVER REQUEST ACKNOWLEDGE message back to the source eNB. The target eNB shall include the E-RABs for which resources have been prepared at the target cell in the E-RABs Admitted List IE. The target eNB shall include the E-RABs that have not been admitted in the E-RABs Not Admitted List IE with an appropriate cause value.

At reception of the HANDOVER REQUEST message the target eNB shall:

-     prepare configuration of the AS security relation between UE and target eNB using the information in UE Security Capabilities IE and the AS Security Information IE in the UE Context Information IE.

For each E-RAB for which the source eNB proposes to do forwarding of downlink data, the source eNB shall include the DL Forwarding IE within the E-RABs To be Setup Item IE of the HANDOVER REQUEST message. For each E-RAB that it has decided to admit, the target eNB may include the DL GTP Tunnel Endpoint IE within the E-RABs Admitted Item IE of the HANDOVER REQUEST ACKNOWLEDGE message to indicate that it accepts the proposed forwarding of downlink data for this bearer. This GTP tunnel endpoint may be different from the corresponding GTP TEID IE in the E-RAB To Be Switched in Downlink List IE of the PATH SWITCH REQUEST message (see [4]) depending on implementation choice.

For each bearer in the E-RABs Admitted List IE, the target eNB may include the UL GTP Tunnel Endpoint IE to indicate that it requests data forwarding of uplink packets to be performed for that bearer.

Upon reception of the HANDOVER REQUEST ACKNOWLEDGE message the source eNB shall stop the timer T_RELOCprep,  start the timer TX2_RELOCoverall and  terminate the Handover Preparation procedure. The source eNB is then defined to have a Prepared Handover for that X2 UE-associated signalling.

If the Trace Activation IE is included in the HANDOVER REQUEST message then the target eNB shall, if supported initiate the requested trace function as described in [6].

If the Handover Restriction List IE is

-     contained in the HANDOVER REQUEST message, the target eNB shall store the information received in the Handover Restriction List IE in the UE context and the target eNB shall use this information to determine a target cell for the UE during subsequent handover attempts.

-     not contained in the HANDOVER REQUEST message, the target eNB shall consider that no roaming, no area and no access restriction applies to the UE.

If the Location Reporting Information IE is included in the HANDOVER REQUEST message then the target eNB should initiate the requested location reporting functionality as defined in [4].

If the SRVCC Operation Possible IE is included in the HANDOVER REQUEST message, the target eNB shall store the received ‘SRVCC Operation Possible’ in the UE context and use it as defined in [20].

The HANDOVER REQUEST message shall contain the Subscriber Profile ID for RAT/Frequency priority IE, if available.

If the Subscriber Profile ID for RAT/Frequency priority IE is

-     contained in the HANDOVER REQUEST message, the target eNB shall store this information and the target eNB should use the information as defined in [15].

Upon reception of UE History Information IE in the HANDOVER REQUEST message, the target eNB shall collect the information defined as mandatory  in the UE History Information IE, for as long as the UE stays in one of its cells, and store the collected information to be used for future handover preparations.

8.2.1.3            Unsuccessful Operation

Figure 8.2.1.3-1: Handover Preparation, unsuccessful operation

If the target eNB does not admit at least one non-GBR E-RAB, or a failure occurs during the Handover Preparation, the target eNB shall send the HANDOVER PREPARATION FAILURE message to the source eNB. The message shall contain the Cause IE with an appropriate value.

If the target eNB receives a HANDOVER REQUEST message containing RRC Context IE that does not include required information as specified in [9], the target eNB shall send the HANDOVER PREPARATION FAILURE message to the source eNB.

Interactions with Handover Cancel procedure:

If there is no response from the target eNB to the HANDOVER REQUEST message before timer T_RELOCprep expires in the source eNB, the source eNB should cancel the Handover Preparation procedure towards the target eNB by initiating the Handover Cancel procedure with the appropriate value for the Cause IE. The source eNB shall ignore any HANDOVER REQUEST ACKNOWLEDGE or HANDOVER PREPARATION FAILURE message received after the initiation of the Handover Cancel procedure and remove any reference and release any resources related to the concerned X2 UE-associated signalling.

8.2.1.4            Abnormal Conditions

If the target eNB receives a HANDOVER REQUEST message containing several E-RAB ID IEs (in the E-RABs To Be Setup List IE) set to the same value, the target eNB shall not admit the corresponding E-RABs.

If the target eNB receives a HANDOVER REQUEST message containing a E-RAB Level QoS Parameters IE which contains a QCI IE indicating a GBR bearer (as defined in [13]), and which does not contain the GBR QoS Information IE, the target eNB shall not admit the corresponding E-RAB.

If the supported algorithms for encryption defined in the Encryption Algorithms IE in the UE Security Capabilities IE in the UE Context Information IE, plus the mandated support of EEA0 in all UEs [18], do not match any algorithms defined in the configured list of allowed encryption algorithms in the target eNB [18], the target eNB shall reject the procedure using the HANDOVER PREPARATION FAILURE message.

If the supported algorithms for integrity defined in the Integrity Protection Algorithms IE in the UE Security Capabilities IE in the UE Context Information IE, do not match any algorithms defined in the configured list of allowed integrity protection algorithms in the eNB [18] or if all bits in Integrity Protection Algorithms IE are equal to 0, the eNB shall reject the procedure using the HANDOVER PREPARATION FAILURE message.

8.2.2           SN Status Transfer

8.2.2.1            General

The purpose of the SN Status Transfer procedure is to transfer the uplink PDCP SN and HFN receiver status and the downlink PDCP SN and HFN transmitter status from the source to the target eNB during an X2 handover for each respective E-RAB for which PDCP SN and HFN status preservation applies.

The procedure uses UE-associated signalling.

8.2.2.2            Successful Operation

 

Figure 8.2.2.2-1: SN Status Transfer, successful operation

The source eNB initiates the procedure by stop assigning PDCP SNs to downlink SDUs and stop delivering UL SDUs towards the EPC and sending the SN STATUS TRANSFER message to the target eNB at the time point when it considers the transmitter/receiver status to be frozen.

The E-RABs Subject To Status Transfer List IE included in the SN STATUS TRANSFER message contains the E-RAB ID(s) corresponding to the E-RAB(s) for which PDCP SN and HFN status preservation shall be applied.

If the source eNB includes in the SN STATUS TRANSFER message, the information on the missing and received uplink SDUs in the Receive Status Of UL PDCP SDUs IE for each E-RAB for which the source eNB has accepted the request from the target eNB for uplink forwarding, then the target eNB may use it in a Status Report message sent to the UE over the radio.

For each E-RAB for which the DL COUNT Value IE is received in the SN STATUS TRANSFER message, the target eNB shall use it to mark with the value contained in the PDCP-SN IE of this IE the first downlink packet for which there is no PDCP SN yet assigned.

For each E-RAB for which the UL COUNT Value IE is received in the SN STATUS TRANSFER message, the target eNB shall not deliver any uplink packet which has a PDCP SN lower than the value contained in the PDCP-SN IE of this IE.

8.2.2.3            Abnormal Conditions

If the target eNB receives this message for a UE for which no prepared handover exists at the target eNB, the target eNB shall ignore the message.

8.2.3       UE Context Release

8.2.3.1            General

The UE Context Release procedure is initiated by the target eNB to signal to indicate the source eNB that radio and control plane resources for the handed over UE context are allowed to be released.

The procedure uses UE-associated signalling.

8.2.3.2            Successful Operation

Figure 8.2.3.2-1:  UE Context Release, successful operation

 

The UE Context Release procedure is initiated by the target eNB. By sending the UE CONTEXT RELEASE message the target eNB informs the source eNB of Handover success and triggers the release of resources.

Upon reception of the UE CONTEXT RELEASE message, the source eNB may release radio and control plane related resources associated to the UE context. For E-RABs for which data forwarding has been performed, the source eNB should continue forwarding of U-plane data as long as packets are received at the source eNB from the EPC or the source eNB buffer has not been emptied (an implementation dependent mechanism decides that data forwarding can be stopped).

8.2.3.3            Unsuccessful Operation

Not applicable.

8.2.3.4            Abnormal Conditions

If the UE Context Release procedure is not initiated towards the source eNB from any prepared eNB before the expiry of the timer TX2_RELOCoverall, the source eNB shall request the MME to release the UE context.

If the UE returns to source eNB before the reception of the UE CONTEXT RELEASE message or the expiry of the timer TX2_RELOCoverall, the source eNB shall stop the TX2_RELOCoverall and continue to serve the UE.

8.2.4       Handover Cancel

8.2.4.1            General

The Handover Cancel procedure is used to enable a source eNB to cancel an ongoing handover preparation or an already prepared handover.

The procedure uses UE-associated signalling.

8.2.4.2            Successful Operation

Figure 8.2.4.2-1: Handover Cancel, successful operation

The source eNB initiates the procedure by sending the HANDOVER CANCEL message to the target eNB. The source eNB shall indicate the reason for cancelling the handover by means of an appropriate cause value.

At the reception of the HANDOVER CANCEL message, the target eNB shall remove any reference to, and release any resources previously reserved to the concerned UE context.

The New eNB UE X2AP ID IE shall be included if it has been obtained from the target eNB.

8.2.4.3            Unsuccessful Operation

Not applicable.

8.2.4.4            Abnormal Conditions

Should the HANDOVER CANCEL message refer to a context that does not exist, the target eNB shall ignore the message.

8.3           Global Procedures

8.3.1           Load Indication

8.3.1.1            General

The purpose of the Load Indication procedure is to transfer load and interference co-ordination information between eNBs controlling intra-frequency neighboring cells.

The procedure uses non UE-associated signalling.

8.3.1.2            Successful Operation

Figure 8.3.1.2-1: Load Indication, successful operation

An eNB initiates the procedure by sending LOAD INFORMATION message to eNBs controlling intra-frequency neighbouring cells .

If the UL Interference Overload Indication IE is received in the LOAD INFORMATION message, it indicates the interference level experienced by the indicated cell on all resource blocks, per PRB. The receiving eNB may take such information into account when setting its scheduling policy and shall consider the received UL Interference Overload Indication IE value valid until reception of a new LOAD INFORMATION message carrying an update of the same IE.

If the UL High Interference Indication IE is received in the LOAD INFORMATION message, it indicates, per PRB, the occurrence of high interference sensitivity, as seen from the sending eNB. The receiving eNB should try to avoid scheduling cell edge UEs in its cells for the concerned PRBs. The Target Cell ID IE received within the UL High Interference Information IE group in the LOAD INFORMATION message indicates the cell for which the corresponding UL High Interference Indication is meant. The receiving eNB shall consider the value of the UL High Interference Information IE group valid until reception of a new LOAD INFORMATION message carrying an update.

If the Relative Narrowband Tx Power (RNTP) IE is received in the LOAD INFORMATION message, it indicates, per PRB, whether downlink transmission power is lower than the value indicated by the RNTP Threshold IE. The receiving eNB may take such information into account when setting its scheduling policy and shall consider the received Relative Narrowband Tx Power (RNTP) IE value valid until reception of a new LOAD INFORMATION message carrying an update.

8.3.1.3            Unsuccessful Operation

Not applicable.

8.3.1.4            Abnormal Conditions

Void.

8.3.2       Error Indication

8.3.2.1            General

The Error Indication procedure is initiated by an eNB to report detected errors in one incoming message, provided they cannot be reported by an appropriate failure message.

If the error situation arises due to reception of a message utilising UE associated signalling, then the Error Indication procedure uses UE-associated signalling. Otherwise the procedure uses non UE-associated signalling.

8.3.2.2            Successful Operation

Figure 8.3.2.2-1: Error Indication, successful operation.

When the conditions defined in clause 10 are fulfilled, the Error Indication procedure is initiated by an ERROR INDICATION message sent from the node detecting the error situation.

The ERROR INDICATION message shall contain at least either the Cause IE or the Criticality Diagnostics IE.

In case the Error Indication procedure is triggered by UE associated signalling the Old eNB UE X2AP ID IE and New eNB UE X2AP ID IE shall be included in the ERROR INDICATION message. If one or both of Old eNB UE X2AP ID IE and New eNB UE X2AP ID IE are not correct, the cause shall be set to appropriate value e.g. " unknown Old eNB UE X2AP ID", "unknown New eNB UE X2AP ID"  or "unknown pair of UE X2AP ID".

8.3.2.3            Unsuccessful Operation

Not applicable.

8.3.2.4            Abnormal Conditions

Not applicable.

8.3.3       X2 Setup

8.3.3.1            General

The purpose of the X2 Setup procedure is to exchange application level configuration data needed for two eNBs to interoperate correctly over the X2 interface. This procedure erases any existing application level configuration data in the two nodes and replaces it by the one received. This procedure also resets the X2 interface like a Reset procedure would do.

The procedure uses non UE-associated signalling.

8.3.3.2            Successful Operation

 

Figure 8.3.3.2-1: X2 Setup, successful operation

An eNB initiates the procedure by sending the X2 SETUP REQUEST message to a candidate eNB. The candidate eNB replies with the X2 SETUP RESPONSE message. The initiating eNB transfers a list of served cells and, if available, a list of supported GU Group Ids to the candidate eNB. The candidate eNB replies with a list of its served cells and shall include, if available, a list of supported GU Group Ids in the reply.

The initiating eNB may include the Neighbour Information IE in the X2 SETUP REQUEST message. The candidate eNB may also include the Neighbour Information IE in the X2 SETUP RESPONSE message. The Neighbour Information IE shall only include E-UTRAN cells that are direct neighbours of cells in the reporting eNB. A direct neighbour of one cell of eNB₂ may be any cell belonging to an eNB that is a neighbour of that eNB₂ cell e.g. even if the cell has not been reported by a UE. 

The initiating eNB may include the Number of Antenna Ports IE in the X2 SETUP REQUEST message. The candidate eNB may also include the Number of Antenna Ports IE in the X2 SETUP RESPONSE message. The eNB receiving the IE may use it according to [9].

8.3.3.3            Unsuccessful Operation

Figure 8.3.3.3-1: X2 Setup, unsuccessful operation

If the candidate eNB cannot accept the setup it shall respond with an X2 SETUP FAILURE message with appropriate cause value.

If the X2 SETUP FAILURE messages includes the Time To Wait IE the initiating eNB shall wait at least for the indicated time before reinitiating the X2 Setup procedure towards the same eNB.

8.3.3.4            Abnormal Conditions

If the first message received for a specific TNL association is not an X2 SETUP REQUEST, X2 SETUP RESPONSE, or X2 SETUP FAILURE message then this shall be treated as a logical error.

If the initiating eNB₁ does not receive either X2 SETUP RESPONSE message or X2 SETUP FAILURE message, the eNB₁ may reinitiate the X2 Setup procedure towards the same eNB, provided that the content of the new X2 SETUP REQUEST message is identical to the content of the previously unacknowledged X2 SETUP REQUEST message.

If the initiating eNB₁ receives an X2 SETUP REQUEST message from the peer entity on the same X2 interface:

-     In case the eNB₁ answers with an X2 SETUP RESPONSE message and receives a subsequent X2 SETUP FAILURE message, the eNB₁ shall consider the X2 interface as non operational and the procedure as unsuccessfully terminated according to sub clause 8.3.3.3.

-     In case the eNB₁ answers with an X2 SETUP FAILURE message and receives a subsequent X2 SETUP RESPONSE  message, the eNB₁ shall ignore the X2 SETUP RESPONSE message and consider the X2 interface as non operational.

8.3.4       Reset

8.3.4.1            General

The purpose of the Reset procedure is to align the resources in eNB₁ and eNB₂ in the event of an abnormal failure. The procedure resets the X2 interface. This procedure doesn’t affect the application level configuration data exchanged during the X2 Setup procedure.

The procedure uses non UE-associated signalling.

8.3.4.2            Successful Operation

Figure 8.3.4.2-1: Reset, successful operation

The procedure is initiated with a RESET REQUEST message sent from the eNB₁ to the eNB₂. Upon receipt of this message, eNB₂ shall abort any other ongoing procedures over X2 between eNB₁ and eNB_2. The eNB₂ shall delete all the context information related to the eNB₁, except the application level configuration data exchanged during the X2 Setup or eNB Configuration Update procedures, and release the corresponding resources. After completion of release of the resources, the eNB₂ shall respond with a RESET RESPONSE message.

8.3.4.3            Unsuccessful Operation

Void.

8.3.4.4            Abnormal Conditions

If the RESET REQUEST message is received, any other ongoing procedure (except another Reset procedure) on the same X2 interface shall be aborted.

If Reset procedure is ongoing and the eNB₂ receives the RESET REQUEST message from the peer entity on the same X2 interface, the eNB₂ shall respond with the RESET RESPONSE message as described in 8.3.4.2.

If the initiating eNB does not receive RESET RESPONSE message, the eNB₁ may reinitiate the Reset procedure towards the same eNB, provided that the content of the new RESET REQUEST message is identical to the content of the previously unacknowledged RESET REQUEST message.

8.3.5       eNB Configuration Update

8.3.5.1            General

The purpose of the eNB Configuration Update procedure is to update application level configuration data needed for two eNBs to interoperate correctly over the X2 interface.

The procedure uses non UE-associated signalling.

8.3.5.2            Successful Operation

 

Figure 8.3.5.2-1: eNB Configuration Update, successful operation

An eNB₁ initiates the procedure by sending an ENB CONFIGURATION UPDATE message to a peer eNB₂ including an appropriate set of updated configuration data that it has just taken into operational use.

Upon reception of an ENB CONFIGURATION UPDATE message, eNB₂ shall update the information for eNB₁ as follows:

Update of Served Cell Information:

-     If Served Cells To Add IE is contained in the ENB CONFIGURATION UPDATE message, eNB₂ shall add cell information according to the information in the Served Cell Information IE.

-     If Number of Antenna Ports IE is contained in the Served Cell Information IE in the ENB CONFIGURATION UPDATE message, eNB₂ may use this information according to [9].

-     If Served Cells To Modify IE is contained in the ENB CONFIGURATION UPDATE message, eNB₂ shall modify information of cell indicated by Old ECGI IE according to the information in the Served Cell Information IE.

      When either served cell information or neighbour information of an existing served cell in eNB₁ need to be updated, the whole list of neighbouring cells, if any, shall be contained in the Neighbour Information IE.

      The eNB₂ shall overwrite the served cell information and the whole list of neighbour cell information for the affected served cell.

-     If Served Cells To Delete IE is contained in the ENB CONFIGURATION UPDATE message, eNB₂ shall delete information of cell indicated by Old ECGI IE.

Update of GU Group ID List:

-     If GU Group Id To Add List IE is contained in the ENB CONFIGURATION UPDATE message, eNB₂ shall add the GU Group Id to its GU Group Id List. 

-     If GU Group Id To Delete List IE is contained in the ENB CONFIGURATION UPDATE message, eNB₂ shall remove the GU Group Id from its GU Group Id List.  

If Neighbour Information IE is contained in the ENB CONFIGURATION UPDATE message, eNB₂ may use this information to update its neighbour cell relations, or use it for other functions, like PCI selection. The Neighbour Information IE shall only include E-UTRAN cells that are direct neighbours of cells in the reporting eNB. A direct neighbour of one cell of eNB₂ may be any cell belonging to an eNB that is a neighbour of that eNB₂ cell e.g. even if that cell has not been reported by a UE.

After successful update of requested information, eNB₂ shall reply with the ENB CONFIGURATION UPDATE ACKNOWLEDGE message to inform the initiating eNB₁ that the requested update of application data was performed successfully. In case the peer eNB₂ receives an ENB CONFIGURATION UPDATE without any IE except for Message Type IE it shall reply with ENB CONFIGURATION UPDATE ACKNOWLEDGE message without performing any updates to the existing configuration.

The eNB₁ may initiate a further eNB Configuration Update procedure only after a previous eNB Configuration Update procedure has been completed.

8.3.5.3            Unsuccessful Operation

Figure 8.3.5.3-1: eNB Configuration Update, unsuccessful operation

If the eNB₂ can not accept the update it shall respond with an ENB CONFIGURATION UPDATE FAILURE message and appropriate cause value.

If the ENB CONFIGURATION UPDATE FAILURE message includes the Time To Wait IE the eNB₁ shall wait at least for the indicated time before reinitiating the eNB Configuration Update procedure towards the same eNB₂. Both nodes shall continue to operate the X2 with their existing configuration data.

8.3.5.4            Abnormal Conditions

If the eNB₁ after initiating eNB Configuration Update procedure receives neither ENB CONFIGURATION UPDATE ACKNOWLEDGE message nor ENB CONFIGURATION UPDATE FAILURE message, the eNB₁ may reinitiate the eNB Configuration Update procedure towards the same eNB₂, provided that the content of the new ENB CONFIGURATION UPDATE message is identical to the content of the previously unacknowledged ENB CONFIGURATION UPDATE message.

8.3.6           Resource Status Reporting Initiation

8.3.6.1       General

This procedure is used by an eNB to request the reporting of load measurements to another eNB.

The procedure uses non UE-associated signalling.

8.3.6.2       Successful Operation

Figure 8.3.6.2-1: Resource Status Reporting Initiation, successful operation

The procedure is initiated with a RESOURCE STATUS REQUEST message sent from eNB₁ to eNB₂. Upon receipt, eNB₂ shall initiate the requested measurement according to the parameters given in the request in case the Registration Request IE set to "start" and shall terminate the reporting in case the Registration Request IE is set to “stop".

If the Registration Request IE is set to "start" then the Report Characteristics IE shall be included in RESOURCE STATUS REQUEST message.

The Report Characteristics IE indicates the type of measurements eNB₂ shall perform.

For each request cell, the eNB₂ shall include in the RESOURCE STATUS UPDATE message;

-     the Radio Resource Status IE, if  the first bit, “PRB Periodic” of the Report Characteristics IE included in the RESOURCE STATUS REQUEST message is set to 1,

-     the S1 TNL Load Indicator IE, if  the second bit, “TNL Load Ind Periodic” of the Report Characteristics IE included in the RESOURCE STATUS REQUEST message is set to 1,

-     the Hardware Load Indicator IE, if  the third bit, “HW Load Ind Periodic” of the Report Characteristics IE included in the RESOURCE STATUS REQUEST message is set to 1,

If the Reporting Periodicity IE is included in the RESOURCE STATUS REQUEST message, eNB₂ shall use its value as the time interval between two subsequent measurement reports.

If eNB₂ is capable to provide resource status information, it shall initiate the measurements as requested by eNB₁, and respond with the RESOURCE STATUS RESPONSE message. 

8.3.6.3            Unsuccessful Operation

Figure 8.3.6.3-1: Resource Status Reporting Initiation, unsuccessful operation

If the requested measurement cannot be initiated, eNB₂ shall send a RESOURCE STATUS FAILURE message. The Cause IE shall be set to an appropriate value e.g. “Measurement Temporarily not Available”.

8.3.6.4       Abnormal Conditions

If the initiating eNB₁ does not receive either RESOURCE STATUS RESPONSE message or RESOURCE STATUS FAILURE message, the eNB₁ may reinitiate the Resource Status Reporting Initiation procedure towards the same eNB, provided that the content of the new RESOURCE STATUS REQUEST message is identical to the content of the previously unacknowledged RESOURCE STATUS REQUEST message.

If the Report Characteristics IE bitmap is set to "0" (all bits are set to "0") in the RESOURCE STATUS REQUEST message then eNB₂ shall initiate a RESOURCE STATUS FAILURE message, the cause shall be set to appropriate value e.g. "ReportCharacteristicsEmpty".

If the Reporting Periodicity IE value is not specified when at least one of the bits of the Report Characteristics IE, for which semantics is specified, is set to "1" then eNB₂ shall initiate a RESOURCE STATUS FAILURE message, the cause shall be set to appropriate value e.g. "NoReportPeriodicity".

If the eNB₂ received a RESOURCE STATUS REQUEST message which includes the Registration Request IE set to "start" and the eNB1Measurement ID IE corresponding to an existing on-going load measurement reporting, then eNB₂ shall initiate a RESOURCE STATUS FAILURE message, the cause shall be set to appropriate value e.g. "ExistingMeasurementID".

If the Registration Request IE is set to "stop" and the RESOURCE STATUS REQUEST message does not contain eNB2 Measurement ID IE, eNB₂ shall consider the procedure as failed and respond with the RESOURCE STATUS FAILURE message, the cause shall be set to appropriate value e.g. "Unknown eNB Measurement ID".

8.3.7       Resource Status Reporting

8.3.7.1            General

This procedure is initiated by eNB₂ to report the result of measurements requested by eNB₁ using the Resource Status Reporting Initiation.

The procedure uses non UE-associated signalling.

8.3.7.2            Successful Operation

Figure 8.3.7.2-1: Resource Status Reporting, successful operation

The eNB₂ shall report the results of the measurements in RESOURCE STATUS UPDATE message for each requested cell.

9.0        General

Sub clauses 9.1 and 9.2 describe the structure of the messages and information elements required for the X2AP protocol in tabular format. Sub clause 9.3 provides the corresponding ASN.1 definition.

The following attributes are used for the tabular description of the messages and information elements: Presence, Range Criticality and Assigned Criticality. Their definition and use can be found in [4].

9.1        Message Functional Definition and Content

9.1.1       Messages for Basic Mobility Procedures

9.1.1.1            HANDOVER REQUEST

This message is sent by the source eNB to the target eNB to request the preparation of resources for a handover.

Direction: source eNB ®  target eNB.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Old eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated at the source eNB	YES	reject
Cause	M		9.2.6		YES	ignore
Target Cell ID	M		ECGI 9.2.14		YES	reject
GUMMEI	M		9.2.16		YES	reject
UE Context Information		1			YES	reject
> MME UE S1AP ID	M		INTEGER (0..232 -1)	MME UE S1AP ID allocated at the MME	–	–
> UE Security Capabilities	M		9.2.29		–	–
>AS Security Information	M		9.2.30		–	–
> UE Aggregate Maximum Bit Rate	M		9.2.12		–	–
> Subscriber Profile ID for RAT/Frequency priority	O		9.2.25		–	–
>E-RABs To Be Setup List		1			–	–
>>E-RABs To Be Setup Item		1 to <maxnoof Bearers>			EACH	ignore
>>> E-RAB ID	M		9.2.23		–	–
>>> E-RAB Level QoS Parameters	M		9.2.9	Inlcudes necessary QoS parameters	–	–
>>> DL Forwarding	O		9.2.5		–	–
>>> UL GTP Tunnel Endpoint	M		GTP Tunnel Endpoint 9.2.1	SGW endpoint of the S1 transport bearer. For delivery of UL PDUs	–	–
>RRC Context	M		OCTET STRING	 Includes the RRC Handover Preparation Information message as defined in subclause 10.2.2 of [9].	–	–
>Handover Restriction List	O		9.2.3		–	–
>Location Reporting InformationÂ	O		9.2.21	Includes the necessary parameters for location reporting	–	–
UE History Information	M		9.2.38	Same definition as in [4].	YES	ignore
Trace Activation	O		9.2.2		YES	ignore
SRVCC Operation Possible	O		9.2.33		YES	ignore

 

Range bound	Explanation
maxnoofBearers	Maximum no. of E-RABs. Value is 256

 

9.1.1.2            HANDOVER REQUEST ACKNOWLEDGE

This message is sent by the target eNB to inform the source eNB about the prepared resources at the target.

Direction: target eNB ® source eNB.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Old eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated at the source eNB	YES	ignore
New eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated at the target eNB	YES	ignore
E-RABs Admitted List		1			YES	ignore
> E-RABs Admitted Item		1 to <maxnoof Bearers>			EACH	ignore
>> E-RAB ID	M		9.2.23		–	–
>> UL GTP Tunnel Endpoint	O		GTP Tunnel Endpoint 9.2.1	Identifies the X2 transport bearer used for forwarding of UL PDUs	–	–
>> DL GTP Tunnel Endpoint	O		GTP Tunnel Endpoint 9.2.1	Identifies the X2 transport bearer. used for forwarding of DL PDUs	–	–
E-RABs Not Admitted List	O		E-RAB List 9.2.28	a value for E-RAB ID shall only be present once  in E-RABs Admitted List IE + in E-RABs Not Admitted List IE	YES	ignore
Target eNB To Source eNB Transparent Container	M		OCTET STRING	Includes the RRC E-UTRA Handover Command message as defined in subclause 10.2.2 in [9].	YES	ignore
Criticality Diagnostics	O		9.2.7		YES	ignore

 

Range bound	Explanation
maxnoofBearers	Maximum no. of E-RABs. Value is 256

 

9.1.1.3            HANDOVER PREPARATION FAILURE

This message is sent by the target eNB to inform the source eNB that the Handover Preparation has failed.

Direction: target eNB ®  source eNB.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Old eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated  at the source eNB	YES	ignore
Cause	M		9.2.6		YES	ignore
Criticality Diagnostics	O		9.2.7		YES	ignore

 

9.1.1.4            SN STATUS TRANSFER

This message is sent by the source eNB to the target eNB to transfer the uplink/downlink PDCP SN and HFN status during a handover.

Direction: source eNB ® target eNB.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	ignore
Old eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated at the source eNB	YES	reject
New eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated at the target eNB	YES	reject
E-RABs Subject To Status Transfer List		1			YES	ignore
>E-RABs Subject To Status Transfer Item		1 to <maxnoof Bearers>			EACH	ignore
>> E-RAB ID	M		9.2.23		–	–
>>Receive Status Of UL PDCP SDUs	O		BIT STRING  (4096)	PDCP Sequence Number = (First Missing SDU Number + bit position) modulo 4096   0: PDCP SDU has not been received. 1: PDCP SDU has been received correctly.	–	–
>> UL COUNT Value	M		COUNT Value 9.2.15	PDCP-SN and Hyper Frame Number of the first missing UL SDU	–	–
>> DL COUNT Value	M		COUNT Value 9.2.15	PDCP-SN and Hyper frame number that the target eNB should assign for the next DL SDU not having an SN yet	–	–

 

Range bound	Explanation
maxnoofBearers	Maximum no. of E-RABs. Value is 256.

 

9.1.1.5            UE CONTEXT RELEASE

This message is sent by the target eNB to the source eNB to indicate that resources can be released.

Direction: target eNB ® source eNB.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	ignore
Old eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated at the source eNB	YES	reject
New eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated at the target eNB	YES	reject

 

9.1.1.6            HANDOVER CANCEL

This message is sent by the source eNB to the target eNB to cancel an ongoing handover.

Direction: source eNB ® target eNB.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	ignore
Old eNB UE X2AP ID	M		eNB UE X2AP ID 9.2.24	Allocated at the source eNB	YES	reject
New eNB UE X2AP ID	O		eNB UE X2AP ID 9.2.24	Allocated at the target eNB	YES	ignore
Cause	M		9.2.6		YES	ignore

 

9.1.2       Messages for global procedures

9.1.2.1            LOAD INFORMATION

This message is sent by an eNB to neighbouring eNBs to transfer load and interference co-ordination information.

Direction: eNB₁ ® eNB₂.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	ignore
Cell Information	M				YES	ignore
   >Cell Information Item		1 to maxCellineNB			EACH	ignore
   >>Cell ID	M		ECGI 9.2.14	Id of the source cell	–	–
   >>UL Interference Overload Indication	O		9.2.17		–	–
   >>UL High Interference Information		0 to maxCellineNB			–	–
>>>Target Cell ID	 M		ECGI 9.2.14	Id of the cell for which the HII is meant	–	–
>>>UL High Interference Indication	M		9.2.18		–	–
   >>Relative Narrowband Tx Power (RNTP)	O		9.2.19		–	–

 

Range bound	Explanation
maxCellineNB	Maximum no. cells that can be served by an eNB. Value is 256.

 

9.1.2.2            ERROR INDICATION

This message is used to indicate that some error has been detected in the eNB.

Direction: eNB₁ ® eNB₂

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	ignore
Old eNB UE X2AP ID	O		eNB UE X2AP ID 9.2.24	Allocated at the source eNB	YES	ignore
New eNB UE X2AP ID	O		eNB UE X2AP ID 9.2.24	Allocated at the target eNB	YES	ignore
Cause	O		9.2.6		YES	ignore
Criticality Diagnostics	O		9.2.7		YES	ignore

 

9.1.2.3            X2 SETUP REQUEST

This message is sent by an eNB to a neighbouring eNB to transfer the initialization information for a TNL association.

Direction: eNB₁ à eNB₂.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Global eNB ID	M		9.2.22Â		YES	reject
Served Cells		1 to maxCellineNB		This is all the eNB cells	YES	reject
     >Served Cell Information	M		9.2.8		–	–
     >Neighbour Information		0 to maxnoofNeighbours			–	–
         >>ECGI	M		ECGI 9.2.14	E-UTRAN Cell Global Identifier of the neighbour cell	–	–
         >>PCI	M		INTEGER (0..503, …)	Physical Cell Identifier of the neighbour cell	–	–
        >>EARFCN	M		9.2.26	DL EARFCN for FDD and EARFCN for TDD	–	–
GU Group Id List		0 to maxfPools		This is all the pools to which the eNB belongs to	GLOBAL	reject
     >GU Group Id	M		9.2.20		-	-

 

Range bound	Explanation
maxCellineNB	Maximum no. cells that can be served by an eNB. Value is 256.
maxnoofNeighbours	Maximum no. of neighbour cells associated to a given served cell. Value is 512.
maxPools	Maximum no. of pools an eNB can belong to. Value is 16.

 

9.1.2.4            X2 SETUP RESPONSE

This message is sent by an eNB to a neighbouring eNB to transfer the initialization information for a TNL association.

Direction: eNB₂ ® eNB₁.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Global eNB ID	M		9.2.22		YES	reject
Served Cells		1 to maxCellineNB		This is all the eNB cells	YES	reject
     >Served Cell Information	M		9.2.8		–	–
     >Neighbour Information		0 to maxnoofNeighbours			–	–
         >>ECGI	M		ECGI 9.2.14	E-UTRAN Cell Global Identifier of the neighbour cell	–	–
         >>PCI	M		INTEGER (0..503, …)	Physical Cell Identifier of the neighbour cell	–	–
        >>EARFCN	M		9.2.26	DL EARFCN for FDD and EARFCN for TDD	–	–
GU Group Id List		0 to maxPools		This is all the pools to which the eNB belongs to	GLOBAL	reject
    >GU Group Id	M		9.2.20		-	-
Criticality Diagnostics	O		9.2.7		YES	ignore

 

Range bound	Explanation
maxCellineNB	Maximum no. cells that can be served by an eNB. Value is 256.
maxnoofNeighbours	Maximum no. of neighbour cells associated to a given served cell. Value is 512.
maxPools	Maximum no. of pools an eNB can belong to. Value is 16.

 

9.1.2.5            X2 SETUP FAILURE

This message is sent by the eNB to indicate X2 Setup failure.

Direction: eNB₂ ® eNB₁.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Cause	M		9.2.6		YES	ignore
Time To Wait	O		9.2.32		YES	ignore
Criticality Diagnostics	O		9.2.7		YES	ignore

 

9.1.2.6            RESET REQUEST

This message is sent from one eNB to another eNB and is used to request the X2 interface between the two eNB to be reset.

Direction: eNB₁ ® eNB₂.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Cause	M		9.2.6		YES	ignore

 

9.1.2.7            RESET RESPONSE

This message is sent by a eNB as a response to a RESET REQUEST message.

Direction: eNB₂ ® eNB₁.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Criticality Diagnostics	O		9.2.7		YES	ignore

 

9.1.2.8            ENB CONFIGURATION UPDATE

This message is sent by an eNB to a peer eNB to transfer updated information for a TNL association.

Direction: eNB₁ ® eNB₂.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Served Cells To Add		0 to maxCellineNB			GLOBAL	reject
   >Served Cell Information	M		9.2.8		–	–
     >Neighbour Information		0 to maxnoofNeighbours			–	–
         >>ECGI	M		ECGI 9.2.14	E-UTRAN Cell Global Identifier of the neighbour cell	–	–
         >>PCI	M		INTEGER (0..503, …)	Physical Cell Identifier of the neighbour cell	–	–
        >>EARFCN	M		9.2.26	DL EARFCN for FDD and EARFCN for TDD	–	–
Served Cells To Modify		0 to maxCellineNB			GLOBAL	reject
   >Old ECGI	M		ECGI 9.2.14	This is the old E-UTRAN Cell Global Identifier	-	-
   >Served Cell Information	M		9.2.8		–	–
      >Neighbour Information		0 to maxnoofNeighbours			–	–
         >>ECGI	M		ECGI 9.2.14	E-UTRAN Cell Global Identifier of the neighbour cell	–	–
         >>PCI	M		INTEGER (0..503, …)	Physical Cell Identifier of the neighbour cell	–	–
        >>EARFCN	M		9.2.26	DL EARFCN for FDD and EARFCN for TDD	–	–
Served Cells To Delete		0 to maxCellineNB			GLOBAL	reject
   >Old ECGI	M		ECGI 9.2.14	This is the old E-UTRAN Cell Global Identifier of the cell to be deleted	-	-
GU Group Id To Add List		0 to maxPools			GLOBAL	reject
    >GU Group Id	M		9.2.20		-	-
GU Group Id To Delete List		0 to maxPools			GLOBAL	reject
    >GU Group Id	M		9.2.20		-	-

 

Range bound	Explanation
maxCellineNB	Maximum no. cells that can be served by an eNB. Value is 256.
maxnoofNeighbours	Maximum no. of neighbour cells associated to a given served cell. Value is 512.
maxPools	Maximum no. of pools an eNB can belong to. Value is 16.

 

9.1.2.9            ENB CONFIGURATION UPDATE ACKNOWLEDGE

This message is sent by an eNB to a peer eNB to acknowledge update of information for a TNL association.

Direction: eNB₂ ® eNB₁.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Criticality Diagnostics	O		9.2.7		YES	ignore

 

9.1.2.10          ENB CONFIGURATION UPDATE FAILURE

This message is sent by an eNB to a peer eNB to indicate eNB Configuration Update Failure.

Direction: eNB₂ ® eNB₁.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
Cause	M		9.2.6		YES	ignore
Time To Wait	O		9.2.32		YES	ignore
Criticality Diagnostics	O		9.2.7		YES	ignore

 

9.1.2.11          RESOURCE STATUS REQUEST

This message is sent by an eNB₁ to neighbouring eNB₂ to initiate the requested measurement according to the parameters given in the message.

Direction: eNB₁ ® eNB₂.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
eNB1 Measurement ID	M		INTEGER (1..4095,...)	Allocated by eNB1	YES	reject
eNB2 Measurement ID	C-ifRegistrationRequestStop		INTEGER (1..4095,...)	Allocated by eNB2	YES	ignore
Registration Request	M		ENUMERATED(start, stop, …)	In this Release, if the value is set to “stop”, the receiver shall stop all cells measurement.	YES	reject
Report Characteristics	O		BITSTRING (SIZE(32))	Each position in the bitmap indicates measurement object the eNB2 is requested to report. First Bit = PRB Periodic, Second Bit=  TNL load Ind Periodic,   Third Bit = HW Load Ind Periodic. Bits 4 to 32 shall be ignored by the eNB2	YES	reject
Cell To Report		1 to maxCellineNB		Cell ID list for which measurement is needed	EACH	ignore
>Cell ID	M		ECGI 9.2.14
Reporting Periodicity	O		ENUMERATED(1000ms, 2000ms, 5000ms,10000ms, …)		YES	ignore

 

Range bound	Explanation
maxCellineNB	Maximum no. cells that can be served by an eNB. Value is 256.

 

Condition	Explanation
ifRegistrationRequestStop	This IE shall be present if the Registration Request IE is set to the value “stop”.

 

9.1.2.12          RESOURCE STATUS RESPONSE

This message is sent by the eNB₂ to indicate that the requested measurements are successfully initiated.

Direction: eNB₂ ® eNB₁.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
eNB1 Measurement ID	M		INTEGER (1..4095,...)		YES	reject
eNB2 Measurement ID	M		INTEGER (1..4095,...)		YES	reject
Criticality Diagnostics	O		9.2.7		YES	ignore

 

9.1.2.13          RESOURCE STATUS FAILURE

This message is sent by the eNB₂ to indicate requested measurements cannot be initiated.

Direction: eNB₂ ® eNB₁.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	reject
eNB1 Measurement ID	M		INTEGER (1..4095,...)		YES	reject
eNB2 Measurement ID	M		INTEGER (1..4095,...)		YES	reject
Cause	M		9.2.6		YES	ignore
Criticality Diagnostics	O		9.2.7		YES	ignore

 

9.1.2.14          RESOURCE STATUS UPDATE

This message is sent by eNB₂ to neighbouring eNB₁ to report the results of the requested measurements.

Direction: eNB₂ ® eNB₁.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Message Type	M		9.2.13		YES	ignore
eNB1 Measurement ID	M		INTEGER (1..4095,...)		YES	reject
eNB2 Measurement ID	M		INTEGER (1..4095,...)		YES	reject
Cell Measurement Result		1 to maxCellineNB			EACH	ignore
>Cell ID	M		ECGI 9.2.14
>Hardware Load Indicator	O		9.2.34
>S1 TNL Load Indicator	O		9.2.35
>Radio Resource Status	O		9.2.37

 

Range bound	Explanation
maxCellineNB	Maximum no. cells that can be served by an eNB. Value is 256.

 

9.2        Information Element definitions

9.2.0       General

When specifying information elements which are to be represented by bit strings, if not otherwise specifically stated in the semantics description of the concerned IE or elsewhere, the following principle applies with regards to the ordering of bits:

-     The first bit (leftmost bit) contains the most significant bit (MSB);

-     The last bit (rightmost bit) contains the least significant bit (LSB);

-     When importing bit strings from other specifications, the first bit of the bit string contains the first bit of the concerned information.

9.2.1       GTP Tunnel Endpoint

The GTP Tunnel Endpoint IE identifies an X2 transport bearer or the S-GW endpoint of the S1 transport bearer associated to an E-RAB. It contains a Transport Layer Address and a GTP Tunnel Endpoint Identifier. The Transport Layer Address is an IP address to be used for the X2 user plane transport (see [8]) or for the S1 user plane transport (see [19]). The GTP Tunnel Endpoint Identifier is to be used for the user plane transport between eNB and the S-GW or between eNBs.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Transport Layer Address	M		BIT STRING (1..160, ...)	For details on the Transport Layer Address, see ref. [8], [19]	–	–
GTP TEID	M		OCTET STRING (4)		–	–

 

9.2.2       Trace Activation

Defines parameters related to trace activation.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
E-UTRAN Trace ID	M		OCTET STRING (8)	The E-UTRAN Trace ID IE is composed of the following:  Trace Reference defined in [10] (leftmost 6 octets), and Trace Recording Session Reference defined in [10] (last 2 octets)	–	–
Interfaces To Trace	M		BIT STRING (8)	Each position in the bitmap represents a eNB interface first bit =S1-MME, second bit =X2, third bit =Uu other bits reserved for future use.. Value ‘1’ indicates ‘should be traced’ . Value ‘0’ indicates ‘should not be trace’.
Trace Depth	M		ENUMERATED( minimum, medium, maximum, MinimumWithoutVendorSpecificExtension, MediumWithoutVendorSpecificExtension, MaximumWithoutVendorSpecificExtension, ...)	Defined in [7]	–	–
Trace Collection Entity IP Address	M		BIT STRING (1..160,…)	For details on the Transport Layer Address, see ref. [8], [19]	_	_

 

9.2.3       Handover Restriction List

This IE defines area roaming or access restrictions for handover.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Serving PLMN	M		PLMN Identity 9.2.4		–	–
Equivalent PLMNs		0..<maxnoofEPLMNs>		Allowed PLMNs in addition to Serving PLMN. This list corresponds to the list of “equivalent PLMNs list” as defined in [17].	–	–
>PLMN Identity	M		9.2.4		–	–
Forbidden TAs		0..<maxnoofEPLMNsPlusOne>		intra E-UTRAN roaming restrictions	–	–
>PLMN Identity	M		9.2.4	The PLMN of forbidden TACs	–	–
>Forbidden TACs		1..<maxnoofForbTACs>			–	–
>>TAC	M		OCTET STRING(2)	The forbidden TAC	–	–
Forbidden LAs		0..<maxnoofEPLMNsPlusOne>		inter-3GPP RAT roaming restrictions	–	–
>PLMN Identity	M		9.2.4		–	–
>Forbidden LACs		1..<maxnoofForbLACs>			–	–
  >>LAC	M		OCTET STRING(2)		–	–
Forbidden inter RATs	O		ENUMERATED(ALL, GERAN, UTRAN, CDMA2000, …)	inter-3GPP and 3GPP2 RAT access restrictions	–	–

 

Range bound	Explanation
maxnoofEPLMNs	Maximum no. of equivalent PLMN Ids. Value is 15.
maxnoofEPLMNsPlusOne	Maximum no. of equivalent PLMN Ids plus one. Value is 16.
maxnoofForbTACs	Maximum no. of forbidden Tracking Area Codes. Value is 4096.
maxnoofForbLACs	Maximum no. of forbidden Location Area Codes. Value is 4096.

 

9.2.4       PLMN Identity

This information element indicates the PLMN Identity.

 

9.2.5       DL Forwarding

This element indicates that the E-RAB is proposed for forwarding of downlink packets.

 

9.2.6       Cause

The purpose of the cause information element is to indicate the reason for a particular event for the whole protocol.

 

The meaning of the different cause values is described in the following table. In general, "not supported" cause values indicate that the concerned capability is missing. On the other hand, "not available" cause values indicate that the concerned capability is present, but insufficient resources were available to perform the requested action.

Radio Network Layer cause	Meaning
Cell not Available	The concerned cell is not available.
Handover Desirable for Radio Reasons	The reason for requesting handover is radio related.
Handover Target not Allowed	Handover to the indicated target cell is not allowed for the UE in question
Invalid MME Group ID	The target eNB doesn’t belong to the same pool area of the source eNB i.e. S1 handovers should be attempted instead.
No Radio Resources Available in Target Cell	The target cell doesn’t have sufficient radio resources available.
Partial Handover	Provides a reason for the handover cancellation. The target eNB did not admit all E-RABs included in the HANDOVER REQUEST and the source eNB estimated service continuity for the UE would be better by not proceeding with handover towards this particular target eNB.
Reduce Load in Serving Cell	Load on serving cell needs to be reduced.
Resource Optimisation Handover	The reason for requesting handover is to improve the load distribution with the neighbour cells.
Time Critical Handover	handover is requested for time critical reason i.e. this cause value is reserved to represent all critical cases where the connection is likely to be dropped if handover is not performed.
TX2RELOCoverall Expiry	The reason for the action is expiry of timer TX2RELOCoverall
TRELOCprep Expiry	Handover Preparation procedure is cancelled when timer TRELOCprep expires.
Unknown MME Code	The target eNB belongs to the same pool area of the source eNB and recognizes the MME Group ID. However, the MME Code is unknown to the target eNB.
Unknown New eNB UE X2AP ID	The action failed because the New eNB UE X2AP ID is unknown
Unknown Old eNB UE X2AP ID	The action failed because the Old eNB UE X2AP ID is unknown
Unknown Pair of UE X2AP ID	The action failed because the pair of UE X2 AP IDs is unknown
Encryption And/Or Integrity Protection Algorithms Not Supported	The target eNB is unable to support any of the encryption and/or integrity protection algorithms supported by the UE.
ReportCharacteristicsEmpty	The action failed because there is no characteristic reported.
NoReportPeriodicity	The action failed because the periodicity is not defined.
ExistingMeasurementID	The action failed because measurement-ID is already used.
Unknown eNB Measurement ID	The action failed because some eNB Measurement-ID is unknown.
Measurement Temporarily not Available	The eNB can temporarily not provide the requested measurement object.
Unspecified	Sent when none of the above cause values applies but still the cause is Radio Network Layer related

 

Transport Network Layer cause	Meaning
Transport resource unavailable	The required transport resources are not available
Unspecified	Sent when none of the above cause values applies but still the cause is Transport Network Layer related

 

Protocol cause	Meaning
Abstract Syntax Error (Reject)	The received message included an abstract syntax error and the concerned criticality indicated "reject" (see sub clause 10.3)
Abstract Syntax Error (Ignore and Notify)	The received message included an abstract syntax error and the concerned criticality indicated "ignore and notify" (see sub clause 10.3)
Abstract syntax error (falsely constructed message)	The received message contained IEs or IE groups in wrong order or with too many occurrences (see sub clause 10.3)
Message not Compatible with Receiver State	The received message was not compatible with the receiver state (see sub clause 10.4)
Semantic Error	The received message included a semantic error (see sub clause 10.4)
Transfer Syntax Error	The received message included a transfer syntax error (see sub clause 10.2)
Unspecified	Sent when none of the above cause values applies but still the cause is Protocol related

 

Miscellaneous cause	Meaning
Control Processing Overload	eNB control processing overload
Hardware Failure	eNB hardware failure
Not enough User Plane Processing Resources	eNB has insufficient user plane processing resources available
O&M Intervention	Operation and Maintenance intervention related to eNB equipment
Unspecified	Sent when none of the above cause values applies and the cause is not related to any of the categories Radio Network Layer, Transport Network Layer or Protocol.

 

9.2.7       Criticality Diagnostics

The Criticality Diagnostics IE is sent by the eNB when parts of a received message have not been comprehended or were missing, or if the message contained logical errors. When applicable, it contains information about which IEs were not comprehended or were missing.

 

 

9.2.8       Served Cell Information

This IE contains cell configuration information of a cell that a neighbour eNB may need for the X2 AP interface.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
 PCI	M		INTEGER (0..503, …)	Physical Cell ID	–	–
Cell ID	M		ECGI 9.2.14		–	–
TAC	M		OCTET STRING(2)	Tracking Area Code	–	–
Broadcast PLMNs		1..<maxnoofBPLMNs>		Broadcast PLMNs	–	–
>PLMN Identity	M		9.2.4		–	–
CHOICE EUTRA-Mode-Info	M				–	–
>FDD
  >>FDD Info		1			–	–
          >>>UL EARFCN	M		EARFCN 9.2.26	Corresponds to NUL in ref. [16]	–	–
          >>>DL EARFCN	M		EARFCN 9.2.26	Corresponds to NDL in ref. [16]	–	–
>>>UL Transmission Bandwidth	M		Transmission Bandwidth 9.2 27		–	–
>>>DL Transmission Bandwidth	M		Transmission Bandwidth 9.2 27	Same as UL Transmission Bandwidth in this release.	–	–
      >TDD
  >>TDD Info		1			–	–
>>>EARFCN	M		9.2.26	Corresponds to NDL/NUL in ref. [16]	–	–
>>>Transmission Bandwidth	M		Transmission Bandwidth 9.2 27		–	–
>>>Subframe Assignment	M		ENUMERATED(sa0, sa1, sa2, sa3, sa4, sa5, sa6,…)	Uplink-downlink subframe configurationinformation defined in ref. [10].	–	–
>>>Special Subframe Info				Special subframe configurationinformation defined in ref. [10].
>>>>Special Subframe Patterns	M		ENUMERATED(ssp0, ssp1, ssp2, ssp3, ssp4, ssp5, ssp6, ssp7, ssp8, …)		–	–
>>>>Cyclic Prefix DL	M		ENUMERATED(Normal, Extended,…)		–	–
>>>>Cyclic Prefix UL	M		ENUMERATED(Normal, Extended,…)		–	–
Number of Antenna Ports	O		9.2.43		YES	ignore

 

Range bound	Explanation
maxnoofBPLMNs	Maximum no. of Broadcast PLMN Ids. Value is 6.

 

9.2.9       E-RAB Level QoS Parameters

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

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
QCI	M		INTEGER (0..255)	QoS Class Identifier defined in [12]. Logical range and coding specified in [13].	–	–
Allocation and Retention Priority	M		9.2.31		–	–
GBR QoS Information	O		9.2.10	This IE applies to GBR bearers only and shall be ignored otherwise.	–	–

 

9.2.10    GBR QoS Information

This IE indicates the maximum and guaranteed bit rates of a GBR E-RAB for downlink and uplink.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
E-RAB Maximum Bit Rate Downlink	M		Bit Rate 9.2.11	Maximum Bit Rate in DL (i.e. from EPC to E-UTRAN) for the bearer. Details in [12].	–	–
E-RAB Maximum Bit Rate Uplink	M		Bit Rate 9.2.11	Maximum Bit Rate in UL (i.e. from E-UTRAN to EPC) for the bearer. Details in [12].	–	–
E-RAB Guaranteed Bit Rate Downlink	M		Bit Rate 9.2.11	Guaranteed Bit Rate (provided that there is data to deliver) in DL (i.e. from EPC to E-UTRAN) for the bearer. Details in [12].	–	–
E-RAB Guaranteed Bit Rate Uplink	M		Bit Rate 9.2.11	Guaranteed Bit Rate (provided that there is data to deliver) in UL (i.e. from E-UTRAN to EPC) for the bearer. Details in [12].	–	–

 

9.2.11    Bit Rate

This IE indicates the number of bits delivered by E-UTRAN in UL or to E-UTRAN in DL within a period of time, divided by the duration of the period. It is used, for example, to indicate the maximum or guaranteed bit rate for a GBR E-RAB, or an aggregated maximum bit rate.

 

9.2.12    UE Aggregate Maximum Bit Rate

On Handover Aggregate Maximum Bitrate is transferred to the target eNB. The UE Aggregate Maximum Bitrate is applicable for all Non-GBR bearers per UE which is defined for the Downlink and the Uplink direction and provided by the MME to the eNB.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
UE Aggregate Maximum Bit Rate Downlink	M		Bit Rate 9.2.11		–	–
UE Aggregate Maximum Bit Rate Uplink	M		Bit Rate 9.2.11		–	–

 

9.2.13    Message Type

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

IE/Group Name	Presence	Range	IE type and reference	Semantics description
Procedure Code	M		INTEGER (0..255)	"0" = Handover Preparation "1" = Handover Cancel "2" = Load Indication "3" = Error Indication "4" = SN Status Transfer "5" = UE Context Release "6" = X2 Setup "7" = Reset "8" = eNB Configuration Update "9" = Resource Status Reporting Initiation "10" = Resource Status Reporting “11”  = Private Message
Type of Message	M		CHOICE (Initiating Message, Successful Outcome, Unsuccessful Outcome, …)

 

9.2.14    ECGI

The E-UTRAN Cell Global Identifier (ECGI) is used to globally identify a cell (see [2]).

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
PLMN Identity	M		9.2.4	Â	–	–
E-UTRAN Cell Identifier	M		BIT STRING (28)	The leftmost bits of the E-UTRAN Cell Identifier IE value correspond to the value of the eNB ID IE contained in the Global eNB ID IE (defined in section 9.2.22) identifying the eNB that controls the cell	–	–

 

9.2.15        COUNT Value

This information element indicates the 12 bit PDCP sequence number and the corresponding 20 bit Hyper frame number.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
PDCP-SN	M		INTEGER (0..4095)		–	–
HFN	M		INTEGER (0..1048575)		–	–

 

9.2.16    GUMMEI

This information element indicates the globally unique MME identity.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
GU Group ID	M		9.2.20		–	–
MME code	M		OCTET STRING (1)		–	–

 

9.2.17    UL Interference Overload Indication

This IE provides, per PRB, a report on interference overload. The interaction between the indication of UL Interference Overload and UL High Interference is implementation specific.

 

 

9.2.18    UL High Interference Indication

This IE provides, per PRB, a 2 level report on interference sensitivity. The interaction between the indication of UL Overload and UL High Interference is implementation specific.

 

9.2.19    Relative Narrowband Tx Power (RNTP)

This IE provides an indication on DL power restriction per PRB in a cell and other information needed by a neighbour eNB for interference aware scheduling.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
RNTP Per PRB	M		BIT STRING (6..110, …)	Each position in the bitmap represents a nPRB value (i.e. first bit=PRB 0 and so on), for which the bit value represents RNTP (nPRB), defined in [11]. § Value 0 indicates "Tx not exceeding RNTP threshold". Value 1 indicates "no promise on the Tx power is given"	–	–
RNTP Threshold	M		ENUMERATED (-∞, -11, -10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, …)	RNTPthreshold is defined in [11]	–	–
Number Of Cell-specific Antenna Ports	M		ENUMERATED (1, 2, 4, …)	P (number of antenna ports for cell-specific reference signals) defined in [10]	–	–
P_B	M		INTEGER (0..3, …)	PB is defined in [11]	–	–
PDCCH Interference Impact	M		INTEGER (0..4, …)	Measured by Predicted Number Of Occupied PDCCH OFDM Symbols (see [10]).   Value 0 means "no prediction is available"	–	–

 

9.2.20    GU Group Id

The GU Group Id IE is the globally unique group id corresponding to a pool area.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
PLMN Id	M		9.2.4		–	–
MME Group Id	M		OCTET STRING(2)		–	–

 

9.2.21    Location Reporting Information

This information element indicates how the location information should be reported.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Event	M		ENUMERATED (Change of serving cell, …)		–	–
Report Area	M		ENUMERATED (ECGI, …)		–	–

 

9.2.22    Global eNB ID

This IE is used to globally identify an eNB (see [2]).

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
PLMN Identity	M		9.2.4		–	–
CHOICE eNB ID	M				–	–
>Macro eNB ID			BIT STRING (20)	Equal to the 20 leftmost bits of the value of the E-UTRAN Cell Identifier IE contained in the ECGI IE (see section 9.2.14) identifying each cell controlled by the eNB
>Home eNB ID			BIT STRING (28)	Equal to the value of the E-UTRAN Cell Identifier IE contained in the ECGI IE (see section 9.2.14) identifying the cell controlled by the eNB

 

9.2.23    E-RAB ID

This IE uniquely identifies an E-RAB for a UE.

 

9.2.24    eNB UE X2AP ID

This information element uniquely identifies an UE over the X2 interface within an eNB.

The Old eNB UE X2AP ID is allocated by the source eNB and the New eNB UE X2AP ID is allocated by the target eNB, as defined in [2].

 

9.2.25    Subscriber Profile ID for RAT/Frequency priority

The Subscriber Profile ID IE for RAT/Frequency Selection Priority is used to define camp priorities in Idle mode and to control inter-RAT/inter-frequency handover in Active mode [15].

IE/Group Name	Presence	Range	IE type and reference	Semantics description
Subscriber Profile ID for RAT/Frequency Priority	M		INTEGER (1..256)

 

9.2.26    EARFCN

The E-UTRA Absolute Radio Frequency Channel Number defines the carrier frequency used in a cell for a given direction (UL or DL) in FDD or for both UL and DL directions in TDD.

 

Range bound	Explanation
maxEARFCN	Maximum value of EARFCNs. Value is 65535.

 

9.2.27    Transmission Bandwidth

The Transmission Bandwidth IE is used to indicate the UL or DL transmission bandwidth expressed in units of resource blocks  " N_RB " [16]. The values bw6, bw15, bw25, bw50, bw75, bw100 correspond to the number of resource blocks “NRB” 6, 15, 25, 50, 75, 100.

 

9.2.28    E-RAB List

The IE contains a list of E-RAB identities with a cause value. It is used for example to indicate not admitted bearers.  

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
E-RAB List Item		1 to < maxnoofBearers >			EACH	ignore
>E-RAB ID	M		9.2.23		–	–
>Cause	M		9.2.6		–	–

 

Range bound	Explanation
maxnoofBearers	Maximum no. of E-RABs. Value is 256.

 

9.2.29    UE Security Capabilities

The UE Security Capabilities IE defines the supported algorithms for encryption and integrity protection in the UE.

IE/Group Name	Presence	Range	IE Type and Reference	Semantics Description
 Encryption Algorithms	M		BIT STRING (16, ...)	Each position in the bitmap represents an encryption algorithm:  "all bits equal to 0" - UE supports no other algorithm than EEA0  “first bit” - 128-EEA1, “second bit” - 128-EEA2, other bits reserved for future use.  Value ‘1’ indicates support and value “0” indicates no support of the algorithm. Algorithms are defined in  [18].
Integrity Protection Algorithms	M		BIT STRING (16, ...)	 Each position in the bitmap represents an integrity protection  algorithm:   “first bit” - 128-EIA1, “second bit” - 128-EIA2, other bits reserved for future use. Value ‘1’ indicates support and value “0” indicates no support of the algorithm. Algorithms are defined in  [18].

 

9.2.30    AS Security Information

The AS Security Information IE is used to generate the key material to be used for AS security with the UE.

 

9.2.31    Allocation and Retention Priority

This IE specifies the relative importance compared to other E-RABs for allocation and retention of the E-UTRAN Radio Access Bearer.

 

9.2.32    Time to Wait

This IE defines the minimum allowed waiting times.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
Time to Wait	M		ENUMERATED(1s, 2s, 5s, 10s, 20s, 60s, …)

 

9.2.33    SRVCC Operation Possible

The IE indicates that both the UE and the MME are SRVCC-capable. E-UTRAN behaviour on reception of this is specified in [20].

IE/Group Name	Presence	Range	IE type and reference	Semantics description
SRVCC Operation Possible	M		ENUMERATED(Possible, …)

 

9.2.34    Hardware Load Indicator

The Hardware Load Indicator IE indicates the status of the Hardware Load experienced by the cell.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
DL Hardware Load Indicator	M		9.2.36
UL Hardware Load Indicator	M		9.2.36

 

9.2.35    S1 TNL Load Indicator

The S1 TNL Load Indicator IE indicates the status of the S1 Transport Network Load experienced by the cell.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
DL S1TNL Load Indicator	M		9.2.36
UL S1TNL Load Indicator	M		9.2.36

 

9.2.36    Load Indicator

The Load Indicator IE indicates the status of Load.

IE/Group Name	Presence	Range	IE type and reference	Semantics description
Load Indicator	M		ENUMERATED (LowLoad, MediumLoad, HighLoad,  Overload, ...)

 

9.2.37    Radio Resource Status

The Radio Resource Status IE indicates the usage of the PRBs in Downlink and Uplink [22], [23].

IE/Group Name	Presence	Range	IE type and reference	Semantics description
DL GBR PRB usage	M		INTEGER (0..100)
UL GBR PRB usage	M		INTEGER (0..100)
DL non-GBR PRB usage	M		INTEGER (0..100)
UL non-GBR PRB usage	M		INTEGER (0..100)
DL Total PRB usage	M		INTEGER (0..100)
UL Total PRB usage	M		INTEGER (0..100)

 

9.2.38    UE History Information

The UE History Information IE contains information about cells that a UE has been served by in active state prior to the target cell. The overall mechanism is described in [15].

NOTE:      The definition of this IE is aligned with the definition of the UE History Information IE in [4].

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Last Visited Cell List		1 to maxnoofCells		Most recent information is added to the top of this list	–	–
>Last Visited Cell Information	M		9.2.39		–	–

 

 

9.2.39    Last Visited Cell Information

The Last Visited Cell Information may contain E-UTRAN or UTRAN cell specific information.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
CHOICE Last Visited Cell Information	M				-	-
>E-UTRAN Cell	M		Last Visited E-UTRAN Cell Information 9.2.40		-	-
>UTRAN Cell	M		OCTET STRING	Defined in [24]	-	-
>GERAN Cell	M		Last Visited GERAN Cell Information 9.2.41

 

9.2.40    Last Visited E-UTRAN Cell Information

The Last Visited E-UTRAN Cell Information contains information about a cell that is to be used for RRM purposes.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Global Cell ID	M		ECGI 9.2.14		-	-
Cell Type	M		9.2.42		-	-
Time UE stayed in Cell	M		INTEGER (0..4095)	The duration of the time the UE stayed in the cell in seconds. If the UE stays in a cell more than 4095s, this IE is set to 4095	-	-

 

9.2.41    Last Visited GERAN Cell Information

The Last Visited Cell Information for GERAN is currently undefined.

NOTE:      If in later Releases this is defined, the choice type may be extended with the actual GERAN specific information.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
CHOICE Last Visited GERAN Cell Information	M				-	-
>Undefined	M		NULL		-	-

 

9.2.42    Cell Type

The cell type provides the cell coverage area.

IE/Group Name	Presence	Range	IE type and reference	Semantics description	Criticality	Assigned Criticality
Cell Size	M		ENUMERATED (verysmall, small, medium, large, …)		-	-

 

9.2.43    Number of Antenna Ports

The Number of Antenna Ports IE is used to indicate the number of cell specific antenna ports.