5G & 4G in WIRELESS: 2011

RRC connection Re-configuration Failure

Triggering points of Re-configuration Failure

The UE receiving RRC Connection Reconfiguration message -with any related action, for e.x. mobility, measurements, physical config, radio config etc.- will validate a set of necessary conditions. If these conditions are not met then UE will trigger Re-establishment Procedure. There are couple of scenarios where the UE can behave in a different way and are stated below:

if the UE is unable to comply with (part of) the configuration included in the RRCConnectionReconfiguration message then roll back to the previous configurations
if security has not been activated and UE receives RRCConnectionReconfiguration message then proceed to release the RRC Connection with release cause 'other'

or else:

initiate the connection Re-establishment procedure, upon which the connection reconfiguration procedure ends (click here to know about the RRC CONNECTION RE-ESTABLISHMENT procedure in detail)

Important Points:

If the UE is unable to comply with part of the configuration, it does not apply any part of the configuration, i.e. there is no partial success/ failure

GUTI in LTE

Query_1: What is GUTI and why it is needed?

It stands for Globally Unique Temporary Identifier
Assigned by MME during the Initial Attach procedure of the UE
If the UE transmits it's IMSI every-time when it wants to talk to the network, then any intruder can hack the interface and determine the IMSI. With this information the intruder can play the role of the original subscriber of the UE and fulfill his/her vested interest. Therefore, there was a need of a different Identity through which the network will recognize the UE. This solves the purpose of the GUTI. Therefore, in other words, GUTI is used for the identification of the UE which doesn't reveal the UE's permanent identity.
GUTI allows identification of the MME to which the UE attaches

Let us see the ingredients and their resemblance to construct GUTI

MMEI: MME Identifier (Identify a MME uniquely; operator configures in eNB)
MMEGI: MME Group ID (Unique within a PLMN, used to identify different MME Groups)
MMEC: MME Code (Identify a MME uniquely within a MME group)
PLMN: MNC + MCC
GUMMEI: Globally Unique MME Identifier globally
M-TMSI: MME-Temporary Mobile Subscriber Identity

Operators make sure that MMEC is unique within the MME pool. A collection of MMEC makes MMEGI as depicted in the following diagram:

Therefore, the unique MME-Code and the MME-Group Identifier makes the MME-Identifier. From the MMEI, a particular MME can be identified. Hence,
MMEI= MMEGI + MMEC

Now, MME-Identifer and PLMN makes the Globally Unique MME-Identifier. Hence,
GUMMEI= PLMN + MMEI

Query_2: What is M-TMSI?

Identifies the UE within the MME
MME allocates M-TMSI to UE, to make M-TMSI, MME uses the UE IMSI
Signalled to UE within the ATTACH ACCEPT or TAU ACCEPT message
M-TMSI changes for the UE, when the UE moves to another MME
is 32 bit

Hence, using GUMMEI and M-TMSI, GUTI is constructed.

Query_3: What is S-TMSI?

stands for SAE-TMSI
a shorter variant of GUTI
used to locally identify a UE within a MME group
used in Paging the UE

S-TMSI (40 bits) = MMEC (8 bits) + M-TMSI (32 bits)

Timers in LTE

LTE UE Timers:

Timer	Start	Stop	At expiry
T300	Transmission of RRCConnectionRequest	Reception of RRCConnectionSetup or RRCConnectionReject message, cell re-selection and upon abortion of connection establishment by upper layers	Reset MAC and Mac configuration. Inform upper layers about the failure
T301	Transmission of RRCConnectionReestabilshmentRequest	Reception of RRCConnectionReestablishment or RRCConnectionReestablishmentReject message as well as when the selected cell becomes unsuitable	Go to RRC_IDLE
T302	Reception of RRCConnectionReject while performing RRC connection establishment	Upon entering RRC_CONNECTED and upon cell re-selection	Inform upper layers
T303	Access barred while performing RRC connection establishment for mobile originating calls	Upon entering RRC_CONNECTED and upon cell re-selection	Inform upper layers
T304	Reception of RRCConnectionReconfiguration message including the MobilityControl Info or	Criterion for successful completion of handover to EUTRA or cell change order is met (the criterion is specified in the target RAT in case of inter-RAT)	In case of cell change order from E-UTRA or intra E-UTRA handover, initiate the RRC connection re-establishment procedure; In case of handover to E-UTRA, perform the actions defined in the specifications applicable for the source RAT.
T304	reception of MobilityFromEUTRACommand message including CellChangeOrder
T305	Access barred while performing RRC connection establishment for mobile originating signalling	Upon entering RRC_CONNECTED and upon cell re-selection	Inform upper layers
T310	Upon detecting physical layer problems i.e. upon receiving N310 consecutive out-of-sync indications from lower layers	Upon receiving N311 consecutive in-sync indications from lower layers, upon triggering the handover procedure and upon initiating the connection re-establishment procedure	If security is not activated: go to RRC_IDLE else: initiate the connection re-establishment procedure
T311	Upon initiating the RRC connection re-establishment procedure	Selection of a suitable E-UTRA cell or a cell using another RAT.	Enter RRC_IDLE
T320	Upon receiving t320 or upon cell (re)selection to E-UTRA from another RAT with validity time configured for dedicated priorities (in which case the remaining validity time is applied).	Upon entering RRC_CONNECTED, when PLMN selection is performed on request by NAS, or upon cell (re)selection to another RAT (in which case the timer is carried on to the other RAT).	Discard the cell reselection priority information provided by dedicated signalling.
T321	Upon receiving measConfig including a reportConfig with the purpose set to reportCGI	Upon acquiring the information needed to set all fields of cellGlobalId for the requested cell, upon receiving measConfig that includes removal of the reportConfig with the purpose set to reportCGI	Initiate the measurement reporting procedure, stop performing the related measurements and remove the corresponding measId

LTE UE Constants:

Constant	Usage
N310	Maximum number of consecutive "out-of-sync" indications received from lower layers. Value in whole number
N311	Maximum number of consecutive "in-sync" indications received from lower layers. Value in whole number

Taken from 3GPP TS 36.331

SIB13 in LTE

SIB13: MBMS control information

contains the information required to acquire the MBMS control information associated with one or more MBSFN areas
introduced in Release9

Signalling radio bearer: N/A
RLC-Mode: TM
Logical channel: BCCH
Direction: E‑UTRAN to UE

Important contents of SystemInformationBlockType13
mbsfn-AreaInfoList

SIB12 in LTE

SIB12: CMAS notification

contains a CMAS notification
CMAS notifications carry high emerygency situations and is defined for three catagories:

-Presiential Alerts (President of a geographical location can send alerts)

-Threat Alerts (Tornado/Hurricane alerts)

-AMBER Alerts (Child abduction, endangered situation)

introduced in Release9

Signalling radio bearer: N/A
RLC-Mode: TMLogical channel: BCCH
Direction: E‑UTRAN to UE

Important contents of SystemInformationBlockType12
messageIdentifier
serialNumber
warningMessageSegmentType
warningMessageSegmentNumber
warningMessageSegment
dataCodingScheme

Field Descriptions:

messageIdentifier	Identifies the source and type of CMAS notification
serialNumber	Identifies variations of a CMAS notification
warningMessageSegmentType	Indicates whether the included CMAS warning message segment is the last segment or not
warningMessageSegmentNumber	Segment number of the CMAS warning message segment contained in the SIB. A segment number of zero corresponds to the first segment, one corresponds to the second segment, and so on
warningMessageSegment	Carries a segment of the Warning Message
dataCodingScheme	Identifies the alphabet/coding and the language applied variations of a CMAS notification

SIB11 in LTE

SIB11: ETWS secondary notification

contains an ETWS secondary notification

Signalling radio bearer: N/A
RLC-Mode: TM
Logical channel: BCCH
Direction: E‑UTRAN to UE

Important contents of SystemInformationBlockType11
messageIdentifier
serialNumber
warningMessageSegmentType
warningMessageSegmentNumber
warningMessageSegment
dataCodingScheme

Field Descriptions:

messageIdentifier	Identifies the source and type of ETWS notification (earthquake, tsunami warning, any emergency or test message)
serialNumber	Identifies variations of an ETWS notification. -uses various mechanisms to alert the user (display message, play a tone or vibrate, location where the message is applicable, also contains an update number which specifies whether a change is in the message content or not)
warningMessageSegmentType [last/not last]	Indicates whether the included ETWS warning message segment is the last segment of the complete segment or not
warningMessageSegmentNumber	# allows oedering of the message segments # Segment number of the ETWS warning message segment contained in the SIB. A segment number of zero corresponds to the first segment, one corresponds to the second segment, and so on
warningMessageSegment	carries actual segment of the message
dataCodingScheme	Identifies the alphabet/coding and the language applied variations of an ETWS notification

SIB10 in LTE

SIB10: ETWS primary notification

contains an ETWS primary notification

Signalling radio bearer: N/A
RLC-Mode: TM
Logical channel: BCCH
Direction: E‑UTRAN to UE

Important contents of SystemInformationBlockType10

messageIdentifier
serialNumber
warningType
warningSecurityInfo

Field Descriptions:

messageIdentifier	Identifies the source and type of ETWS notification (earthquake, tsunami warning, any emergency or test message)
serialNumber	Identifies variations of an ETWS notification. -uses various mechanisms to alert the user (display message, play a tone or vibrate, location where the message is applicable, also contains an update number which specifies whether a change is in the message content or not)
warningType	# Identifies the warning type of the ETWS primary notification (earthquake, tsunami, etc.) and # provides information on emergency user alert and UE popup
warningSecurityInfo	# is optional, only applied when security is applied # Provides security information for the ETWS notification

SIB9 in LTE

SIB9: Home eNB name

contains a home eNB name (HeNB Name)
HeNB provie services to Closed Subscriber Groups. The HeNB name helps the user to select the correct CSG Identity when performing a manual selection

Signalling radio bearer: N/A
RLC-Mode: TM
Logical channel: BCCH
Direction: E‑UTRAN to UE

Important contents of SystemInformationBlockType9
hnb-Name

Field Descriptions:

hnb-Name

Carries the name of the home eNB

SIB7 in LTE

SIB7: Cell-reselection parameters INTER RAT Frequency (GERAN)

contains information relevant only for inter-RAT (GERAN) cell re-selection

Signalling radio bearer: N/A
RLC-Mode: TM
Logical channel: BCCH
Direction: E‑UTRAN to UE

Important contents of SystemInformationBlockType7

t_ReselectionGERAN	Time to trigger for reselection. Value 0 to 7 sec.
carrierFreqsInfoList[0]	carries upto 16 instances of GERAN freq.
carrierFreqs
startingARFCN	Start of the ARFCN
bandIndicator	dcs1800 or pcs1900
followingARFCNs	ARFCN groups
cellReselectionPriority	absolute priority of the GERAN layer. Value 0 to 7, whereas 0 is the lowest priority
ncc_Permitted	Network Color Code. Is a bitmap value
q_RxLevMin	minimum RSSI value required
p_MaxGERAN	maximum allowed UL transmit power
threshX_High	# Threshold (in dB) used by UE for cell re-selection to a HIGHER priority frequency # The Srxlev of the candiate cell is greater then threshX_High # Value 0 to 31 dB. *Actual value= Signaled value 2**
threshX_Low	# Threshold (in dB) used by UE for cell re-selection to a LOWER priority frequency # Cell re-selection is allowed only when Srxlev of the candiate cell is greater then threshX_Low and RSRP of serving cell is less than the value of ThreshServingLow singalled within SIB3 # Value 0 to 31 dB. *Actual value= Signaled value 2**

SIB5 in LTE

SIB5: Cell-reselection parameters for INTER-Frequency

contains information relevant only for inter-frequency cell re-selection i.e. information about other E‑UTRA frequencies and inter-frequency neighbouring cells relevant for cell re-selection
includes cell re-selection parameters common for a frequency as well as cell specific re-selection parameters

Signalling radio bearer: N/A
RLC-Mode: TM
Logical channel: BCCH
Direction: E‑UTRAN to UE

Important contents of SystemInformationBlockType5

InterFreqCarrierFreqInfo	can be specified upto 8 carrier frequencies
dl-CarrierFreq	carrier frequency helps the UE to search the cells
q-RxLevMin	minimum RSRP value of the inter-frequency cell. Value -70 to -22 dBm. Actual value: signalled value * 2
p-Max	maximum allowed UL transmit power of the cell
t-ReselectionEUTRA	defines the time to trigger for cell reselection. Value 0 to 7 sec.
t-ReselectionEUTRA-SF	scaling factors for Medium and High mobility
threshX-High	# Threshold (in dB) used by UE for cell re-selection to a HIGHER priority # The Srxlev of the candiate cell is greater then threshX_High # Value 0 to 31 dB. *Actual value= Signaled value 2**
threshX-Low	# Threshold (in dB) used by UE for cell re-selection to a LOWER priority # Cell re-selection is allowed only when Srxlev of the candiate cell is greater then threshX_Low and RSRP of serving cell is less than the value of ThreshServingLow singalled within SIB3 # Value 0 to 31 dB. *Actual value= Signaled value 2**
allowedMeasBandwidth	defined in terms of Resouce blocks associated with a specific channel bandwidth
cellReselectionPriority	defines the Abolute priority of the frequency layer
neighCellConfig	information regarding the neighbouring cells
q-OffsetFreq	defines the RSRP measurement offset, applied to all cells on the specified RF carrier
interFreqBlackCellList	the mentioned cells are no considered for cell reselection

SIB6 in LTE

SIB6: Cell-reselection parameters INTER RAT Frequency

contains information relevant only for inter-RAT cell re-selection (information about UTRA frequencies and UTRA neighbouring cells relevant for cell re-selection.
includes cell re-selection parameters common for a frequency

Signalling radio bearer: N/A
RLC-Mode: TMLogical channel: BCCH
Direction: E‑UTRAN to UE

Important contents of SystemInformationBlockType6

carrierFreqListUTRA_FDD/TDD
    carrierFreq
    cellReselectionPriority
    threshX_High
    threshX_Low
    q_RxLevMin
    p_Max
    q_QualMin
t_ReselectionUTRA
t_ReselectionUTRA_SF
    SF_Medium
    SF_High

Field Descriptions:

carrierFreqListUTRA_FDD/TDD	Information specified for up to 16 instances of RF carriers for FDD or TDD
carrierFreq	carrier frequency helps the UE to seach
cellReselectionPriority	defines the absolute priority of the UMTS. Value 0-7, 0 is the lowest priority
threshX_High	# Threshold (in dB) used by UE for cell re-selection to a HIGHER priority UMTS frequency # The Srxlev of the candiate cell is greater then threshX_High # Value 0 to 31 dB. *Actual value= Signaled value 2**
threshX_Low	# Threshold (in dB) used by UE for cell re-selection to a LOWER priority UMTS frequency # Cell re-selection is allowed only when Srxlev of the candiate cell is greater then threshX_Low and RSR of serving cell is less than the value of ThreshServingLow singalled within SIB3 # Value 0 to 31 dB. *Actual value= Signaled value 2**
q_RxLevMin	minimum RSCP requirement for candiate UMTS cell. Value -60 to -13 dB. Actual value= Signaled value * 2 +1
p_Max	Value applicable for the intra-frequency neighbouring E-UTRA cells. If absent the UE applies the maximum power according to the UE capability
q_QualMin	# minimum Ec/Io requirement for candiate UMTS cell. Value -24 to 0 dB # applicable for FDD only
t_ReselectionUTRA	# defines the time to trigger cell re-selection # value 0 - 7 seconds
t_ReselectionUTRA_SF	# defines the time to trigger cell re-selection # value 0 - 7 seconds # Scaling factors used for Medium and High mobility # Scaling Factors value 0.25, 0.5, 0.75, 1.0. These values decrease the value of T_reselection which allows more rapid cell re-selections