06a_LTE mobility management v1_0.ppt

1 © Nokia Siemens Networks Presentation / Author / Date
I insert classification level
LTE Mobility management
LTE optimization training, Sao Paulo December 2011

Soc Classification level
Contents
• Connected mode mobility
– Overview
– Mobility triggers and handover thresholds
– Measurement configuration
– LTE intra-frequency handover
– LTE inter-frequency handover
– S1 handover
– RRC release with redirect
– CS fallback
– IRAT HO to WCDMA
– ANR – Automated neighbour relations
• Idle mode mobility
– SIB and SIB-mapping
– Cell selection
– LTE intra-frequency reselection
– LTE inter-frequency reselection
– Inter RAT reselection

Connected Mode Mobility

Connected Mode Mobility
Overview
• Mobility Management sets the mobility procedures when the UE is in active state
• Procedures supported:
– Handover: Transfer of an ongoing call/data session from a radio channel to
another without call interruption. Handovers in LTE are:
o Network controlled
o UE assisted
o Hard handovers: Only a connection exist to one cell at a time
– Redirection: Similar to handover, but requires connection release prior to the
transfer the ongoing call
– Cell change: procedure dedicated for call transfer from LTE to GSM; it requires
connection release
Presentation / Author / Date
Licensing:
• All IRAT HO, inter-frequency HO, CSFT to UTRAN/GERAN via redirect and S1
handovers are optional features:
• When enabled they are activated for the whole eNodeB
• If deactivated the eNB does not configure UE to measure other technologies/
frequencies so handover is not triggered

Mobility triggers and handover thresholds

Mobility triggers (1/2)
• Mobility is handled via events triggering. 3GPP defines following events:
• Event A2/A1: Serving cells RSRP down/upcrossing certain RSRP
threshold
• Event A3: Neighbor cell’s RSRP is a predefined offset better than serving
cell’s RSRP
• Event A5: Serving cell’s RSRP downcrossing certain threshold, while
neighbor cell’s RSRP upcrossing an other threshold
RSRP
RSRP serving
A2 trigger
A2 threshold
move
direction
RSRP
RSRP serving
A3 trigger
A3 offset
move
direction
RSRP
RSRP serving
A5 trigger
A5 thold 1
A5 thold 2
move direction

Mobility Triggers (2/2)
• Inter-RAT measurements (GERAN or UMTS supported in RL30)
• Event B2: Serving cell’s RSRP down crossing threshold 1, while neighbor cell
RSSI or CPICH RSCP or CPICH Ec/No up crossing threshold 2
• Triggers for Inter-RAT reports are:
– RSSI in case of GERAN
– CPICH RSCP or CPICH EC/N0 in case of UMTS
Signal
Level
RSRP serving
B2 trigger
B2 thold 1
B2 thold 2
move direction
Inter-RAT
Neighbor cell
signal

Handover Thresholds
Measurement Activations
• Threshold 1 (Th1): UE does not perform measurements of neighbour cells when
the serving cell RSRP is above Threshold1 (Th1)
• Thresholds 2 (Th2a/ Th2_interfreq/Th2_WCDMA/Th2_GSM):UE starts
performing measurement gaps when one of the Th2 events is reported to the
eNodeB in a measurement report
• Threshold2a (Th2a): Measurement gaps are cancelled if serving cell RSRP rises
above Th2a
• Threshold 4 (Th4):RRC Connection Release with redirection is triggered if no
suitable intra or inter frequency/IRAT cells are found
RSRP (dBm)
No measurements
except serving cell
Intra –LTE
measurements
Intra –LTE + Inter
Freq measurements
Freq + WCDMA
measurements
Freq + WCDMA +
GSM
measurements
Th4
Th2_GSM
Th2_WCDMA
Th2_InterFreq
Th1 Th2a
RRC
Connection
Release and
re-direction

Intra- and inter-frequency handover thresholds
Serving cell
Threshold1
RSRP for
serving cell
decreases
Only serving cell
measurements are
performed. UE is not
measuring or
reporting any
neighbours
Threshold2InterFreq
When RSRP is
below Threshold1,
UE starts to
measure intra-
frequency
neigbhours
When RSRP is below
Threshold2InterFreq,
UE starts
measurements on
other frequencies.
Threshold2a
RSRP increases
When RSRP is above
Threshold2a, UE stops
measurements on other
frequencies.
Threshold3
When RSRP is
below Threshold3,
UE will perform
HO to neighbour.
(Assuming that
neighbour is better
than threshold3a
and A5 handover
is activated)
Threshold4
When RSRP is
below Threshold4,
the eNB can
redirect the call to
other frequeny or
other RAT. This is
also called RRC
release with
redirect
Threshold3_interFreq
When RSRP is below
Threshold3_interFreq, UE will
perform HO to inter-freq
neighbour. (Assuming that
neighbour is better than
threshold3a_InterFreq and IFHO
is activated)

Mobility thresholds comments
RRC_connected mode
• All threshold are relative to -140. This means if for example
threshold3 is set to 21, the true threshold is (-140+21=)
119dBm.
• The following restrictions need to be fulfilled:
– Threshold4 < Threshold3 < Threshold2InterFreq <= Threshold2a <
Threshold1
– Threshold3 < Threshold3a
– Threshold3InterFreq < Threshold3aInterFreq

Measurement configuration

Measurement Configuration
Overview
• Monitoring of cells other than the serving one requires measurement
configuration which is provided to UE
• RRC:ConnectionReconfiguration message with optional IE: MeasConfig is
used for measurement configuration
• Measurement configuration provides the UE with info such as thresholds and
information to handle measurements (intra LTE and IRAT) and the HO procedure

Structure
Measurement configuration requires definition of:
• measurement object
• report configuration
• measurement identities
• quantity configuration
• measurement gaps

Measurement Gaps (1/2)
• Depending on UE capabilities measurement gaps may be required for several
types of handovers. E.g. inter-RAT-HO, inter-frequency-HO, network assisted cell
change
• During measurement Gaps the UE is measuring Inter-frequency/ I-RAT
candidates and does not transmit nor receive any data from the serving cell
MeasGapConfig
The IE MeasGapConfig specifies the measurement gap configuration and controls setup/ release of measurement gaps.
MeasGapConfig information element
-- ASN1START
MeasGapConfig ::= CHOICE {
release NULL,
setup SEQUENCE {
gapOffset CHOICE {
gp0 INTEGER (0..39),
gp1 INTEGER (0..79),
...
}
}
}
-- ASN1STOP
MeasGapConfig field descriptions
gapOffset
Value gapOffset of gp0 corresponds to gap offset of Gap Pattern Id “0” with TGRP = 40ms, gapOffset of gp1
corresponds to gap offset of Gap Pattern Id “1” with TGRP = 80ms. Also used to specify the measurement gap pattern
to be applied, as defined in TS 36.133 [16].

Measurement Gaps (2/2)
• GAP pattern Id 0 is supported in RL30
• Different gap periodicities are a trade off between throughput and Inter-frequency
and IRAT monitoring
• UL and DL scheduler have to track the measurement gap periodicity and gap
pattern in order to avoid allocations whilst the UE is not listening
• Same monitoring gap is used to search all possible RATs
• The 6ms gap is consumed to switch back and forth from the serving frequency to
the other frequencies and bands and measuring
Table 8.1.2.1-1: Gap Pattern Configurations supported by the UE
Gap Pattern
Id
MeasurementGap
Length (MGL, ms)
Measurement Gap
Repetition Period
(MGRP, ms)
Minimum available time
for inter-frequency and
inter-RAT measurements
during 480ms period
(Tinter1, ms)
Measurement Purpose
0 6 40 60 Inter-Frequency E-UTRAN
FDD and TDD, UTRAN
FDD, GERAN, LCR TDD,
HRPD, CDMA2000 1x
1 6 80 30 Inter-Frequency E-UTRAN
FDD and TDD, UTRAN
FDD, GERAN, LCR TDD,
HRPD, CDMA2000 1x
RL30

MeasObjectEUTRA
Example
value DL-DCCH-Message ::=
{
message c1 : rrcConnectionReconfiguration :
{
rrc-TransactionIdentifier 1,
criticalExtensions c1 : rrcConnectionReconfiguration-r8 :
{
measConfig
{
measObjectToAddModList
{
{
measObjectId 1,
measObject measObjectEUTRA :
{
carrierFreq 2075,
allowedMeasBandwidth mbw25,
presenceAntennaPort1 TRUE,
neighCellConfig '00'B
}
},
{
measObjectId 2,
measObject measObjectEUTRA :
{
carrierFreq 2100,
allowedMeasBandwidth mbw50,
presenceAntennaPort1 TRUE,
neighCellConfig '00'B
}
}
},
• Setup of 2 objects (measObjectId)
• One for each band ( 2075 and 2100)
• Each one of them with a different
Bandwidth :
• 5MHz for 2075MHz
• 10MHz for 2100 MHz
• No cell individual offsets specified to
prioritize between cells

Definition of Report Configuration
Id1( A3 event) and Id2 (A5 event)
reportConfigToAddModList
{
{
reportConfigId 1,
reportConfig reportConfigEUTRA :
{
triggerType event :
{
eventId eventA3 :
{
a3-Offset 6,
reportOnLeave FALSE
},
hysteresis 0,
timeToTrigger ms320
},
triggerQuantity rsrp,
reportQuantity sameAsTriggerQuantity,
maxReportCells 8,
reportInterval ms1024,
reportAmount infinity
}
},
{
reportConfigId 2,
{
triggerType event :
{
eventId eventA5 :
{
a5-Threshold1 threshold-RSRP : 30,
a5-Threshold2 threshold-RSRP : 32
},
hysteresis 0,
timeToTrigger ms640
},
maxReportCells 8,
}
},
These reports are used later on for
Intra-frequency measurements

Id3(A5 event) and Id4 (A3 event)
{
reportConfigId 3,
{
triggerType event :
{
eventId eventA5 :
{
a5-Threshold1 threshold-RSRP : 30,
a5-Threshold2 threshold-RSRP : 31
},
hysteresis 0,
timeToTrigger ms64
},
maxReportCells 8,
}
},
{
reportConfigId 4,
{
triggerType event :
{
eventId eventA3 :
{
a3-Offset 0,
reportOnLeave FALSE
},
hysteresis 4,
timeToTrigger ms128
},
maxReportCells 8,
}
},
These reports are used later on for
Inter-frequency measurements

Id5(A2 event) and Id6 (A1 event)
• Event A2 is used to enable the Inter frequency measurements and Event A1 to
disable other cell measurements
{
reportConfigId 5,
{
triggerType event :
{
eventId eventA2 :
{
a2-Threshold threshold-RSRP : 32
},
hysteresis 0,
timeToTrigger ms256
},
maxReportCells 8,
reportInterval min60,
reportAmount r1
}
},
{
reportConfigId 6,
{
triggerType event :
{
eventId eventA1 :
{
a1-Threshold threshold-RSRP : 33
},
hysteresis 0,
timeToTrigger ms128
},
maxReportCells 8,
reportInterval min60,
reportAmount r1
}
}
},

measIdToAddModList
{
{
measId 1,
measObjectId 1,
reportConfigId 1
},
{
measId 2,
measObjectId 1,
reportConfigId 2
},
{
measId 7,
measObjectId 1,
reportConfigId 5
}
},
quantityConfig
{
quantityConfigEUTRA
{
}
},
measGapConfig release :
NULL,
s-Measure 90,
Part of RRC Connection Reconfiguration
• Measurement Object Id’s and Reporting
Configuration Id’s are grouped and enabled here
• Measurement Id 1 is defined as intra-frequency
measurements of A3 events
• S-measure defines the threshold above which the
UE will perform no neighbour cell measurements
(threshold 1)

Intra-frequency handovers

Handovers
• Two main types of handovers in LTE:
– Better Cell Handover, also called A3 HO.
– Coverage Handover, also called A5 HO.
• Better Cell Handover aims to keep the UE always on best
cell (measured by RSRP), e.g. when neighbour cell becomes
more than 4 dB better than serving cell.
• Coverage Handover is used when serving cell RSRP gets
below a certain threshold (for example -95 dBm) AND
neighbour cell RSRP gets better than an absolute threshold
(for example -92 dBm).

Better cell Handover
Event A3
• Entering Condition:
RSRP at serving cell + a3Offset + hysA3offset < RSRP at neighbor cell
• Leaving Condition:
RSRP at serving cell + a3Offset + hysA3offset > RSRP at neighbor cell
Parameters
involved:
Note: Inter-
frequency A3
handovers can also
be performed based
on RSRQ

Coverage Handover
Event A5
• Entering Condition:
RSRP at serving cell < threshold3 - hysThreshold3 AND…
…RSRP at neighbor cell > threshold3a + hysThreshold3
Note: 3GPP defines ‘Hys’
in the equations. i.e. it is
only possible to signal one
value of ‘Hys’. Hys ->
hysThreshold3
• Leaving Condition:
RSRP at serving cell > threshold3 + hysThreshold3 OR…
… RSRP at neighbor cell < threshold3a - hysThreshold3 Parameters
involved:

Example of successful intra-freq HO
Step 1: UE sends measurement report on PCI 274.

Example of successful intra-freq HO
Step 2: UE gets RRCConnectionReconfiguration on DL and replies with
an RRCConnectionReconfigurationComplete on UL. Note that for a
successful HO, this happens twice. The first
RRCConnectionReconfiguration comes from the source cell and the
second one from the target.

Identifying the trigger condition for a Handover
• The measurement report before a handover doesn’t specify the triggering reason
i.e. A3 or A5 handover
• Instead, the measurement report indicates the measurement id (measId).
• It is necessary to look in the second RRC connection reconfiguration msg before
the measurement report in order to identify which measurement id is mapped to
which reportConfigId
– measId1 = A3
– measId2 = A5
– measId3 = A2
• See following slides for example

How to see difference between A3 and A5 HO
A3
A5

How to see difference between A3 and A5 HO

Inter-frequency handovers

Inter frequency handover
• Inter frequency handover (feature LTE55) allows to hand over a UE in RRC
connected mode between two LTE cells on different frequencies, for example
2600MHz and 1800MHz
• The triggers for this procedure are the same as per intra frequency HO:
– Better neighbour cell coverage (A3, RSRP)
– Better neighbour cell quality (A3, RSRQ)
– Limited serving cell AND sufficient neighbour cell coverage (A5)
• Measurement gaps: if needed then gap pattern 0 is used (6ms gap each 40ms)
LNBTS
LNCEL
LNHOIF
• Parameter object for inter-frequency
idle mode parameters: LNHOIF with
similar parameters as for intra
frequency HO:
RL20
RL15TD

eNB controls Inter frequency measurement in UE
• LNCEL/threshold2InterFreq defines the absolute RSRP level for UE
inter frequency measurement activation
RSRP of
serving cell
time
threshold2InterFreq
UE does not measure nor
report inter frequency
neighbor list
UE measures inter frequency
neighbor list and reports A3 or A5 if
respective condition(s) are met
-140 dBm
threshold2InterFreq
threshold2InterFreq
Trigger for inter frequency
measurements
LNCEL; 0..97dB; 1dB; - ;
hysThreshold2InterFreq
Hysteresis of threshold2InterFreq
LNCEL; 0..15dB; 0.5dB; - ;
a2TimeToTriggerActInterFreq
Meas
Duration for which the event A2 must
be valid
LNCEL; 0ms…5120ms; -; - ;
hysteresis

eNB controls Inter frequency measurement in UE
• LNCEL/threshold2a defines the absolute RSRP level for UE inter frequency
measurement de-activation
RSRP of
serving cell
time
threshold2a
-140 dBm
threshold2a
threshold2a
Stop inter frequency
measurements
LNCEL; 0..97dB; 1dB; - ;
hysThreshold2a
Hysteresis of threshold2a
LNCEL; 0..15dB; 0.5dB; - ;
a1TimeToTriggerDeactInterMe
as
Duration for which the event A1 must
be valid
LNCEL; 0ms…5120ms; -; - ;
hysteresis

A3 event based Handover
Signal
level
(RSRP
or
RSRQ)
serving cell (Ms)
inter-frequency
neighbour cell
(Mn)
time
hysA3OffsetRsr(p/q)InterFreq
a3OffsetRsr(p/q)InterFreq
• Inter-frequency better coverage/quality based (A3) handover event evaluation
Mn – hysA3OffsetRsr(p/q)InterFreq > Ms + a3OffsetRsr(p/q)InterFreq
Event A3 condition fullfilled,
UE sends measurement
report Measurement
Report
Measurement
Report
a3ReportIntervalRsr(p/q)InterFreq
a3TimeToTriggerRsr(p/q)InterFreq
a3OffsetRsrp/qInterFreq
Better cell HO margin for RSRP/Q
LNHOIF; 0..15; 0.5; - dB
hysA3OffsetRsrp/qInterFreq
Hysteresis of HO Margin
LNHOIF; 0..15; 0.5; - dB
measQuantInterFreq
def. which quantity to use
for event A3
LNHOIF; RSRP, RSRQ;
both; RSRP
a3TimeToTriggerRsrp/qInterFreq
LNHOIF; 0..5120ms; -; not used
a3ReportIntervalRsrp/qInterFreq
LNHOIF; 120ms..60 min; -; not used

• Inter-frequency coverage based (A5) handover event evaluation
Ms + hysThreshold3InterFreq < threshold3InterFreq
and
Mn – hysThreshold3InterFreq > threshold3aInterFreq
A5 event based Handover
Signal
level
(RSRP)
serving cell (Ms)
inter-frequency
neighbour cell
(Mn)
time
a5TimeToTriggerInterFreq
event A5 condition fullfilled
UE sends measurement report Measurement
Report
Measurement
Report
Hysteresis of HO Margin
LNHOIF; 0..15; 0.5; - dB
threshold3InterFreq
LNHOIF; 0..97; 1; - dB
threshold3aInterFreq
LNHOIF; 0..97; 1; - dB
a5TimeToTriggerInterFreq
LNHOIF; 0..5120ms; -; -
a5ReportIntervalInterFreq
LNHOIF; 120ms..60 min; -; -

Inter-Frequency HO
Configuration
• LNBTS:actIfHo must be
enabled
• Inter-frequency HO is activated
on site level
• Need to create a LNHOIF
object per cell defining the
parameters that will be used in
the Measurement Configuration
message and all the thresholds
for A3/A5 event
• Need to define the LNCEL
parameters regarding
threshold2/2a to
activate/deactivate inter-
frequency measurements
• Inter-frequency HO parameters:

Inter-frequency HO Example
• When Serving Cell RSRP falls below the threshold specified for event A2 , the UE
sends the following measurement report:
{
message c1 : measurementReport :
{
criticalExtensions c1 : measurementReport-r8 :
{
measResults
{
measId 7,
measResultServCell
{
rsrpResult 32,
rsrqResult 23
}
}
}
}
}
1. Remove the measid related to the
A2 event
2. Start checking for A1 event (in case
serving cell becomes good again,
this is defined via parameter th2a)
3. Start checking for A3 and A5 events
in the new frequency.
4. Perform measurement gaps
according to measurement gap
pattern instructed to measure the
inter-frequency neighbours
Measurement Id 7 was defined as intra-frequency measurements
of A2 events (Measurement Configuration recap section)
• Then the UE is instructed via RRC
Connection Reconfiguration message
to:

{
message c1 : rrcConnectionReconfiguration :
{
rrc-TransactionIdentifier 1,
criticalExtensions c1 : rrcConnectionReconfiguration-r8
:
{
measConfig
{
measIdToRemoveList
{
7
},
measIdToAddModList
{
{
measId 5,
measObjectId 1,
reportConfigId 6
},
{
measId 10,
measObjectId 2,
reportConfigId 3
},
{
measId 11,
measObjectId 2,
reportConfigId 4
}
},
measGapConfig setup :
{
gapOffset gp0 : 28
}
}
}
}
}
Inter-frequency HO Example
• When the eNodeB receives the measurement
report with event A2 triggered it will proceed to
command UE to perform measurement gaps so
that it can measure inter-frequency neighbours
• At the same time it specifies:
1. Stop measuring for event A2
2. Criteria to cancel inter-frequency neighbour
search (event A1)
3. Criteria for coverage reason HO for inter-
frequency neighbours (event A5)
4. Criteria for better cell for inter-frequency
neighbours (event A3)
• Measurement gap pattern Id= 0 and offset = 28

Measurement gaps
• Different gap periodicities are a trade off between throughput
and Inter-frequency monitoring
• Example of measurement gaps impact on DL throughput:
TCP and UDP DL tput, with and without measurement gap, 10MHz system
0
10
20
30
40
50
60
70
80
1 6 11 16 21 26 31 36 41 46 51 56
time, seconds
tput,
Mbps
MEAS GAP ON UDP
MEAS GAP OFF UDP
MEAS GAP ON TCP
MEAS GAP OFF TCP

Measurement gaps – example from TTI trace
Meas. gap
7 TTIs
30 TTIs

Inter-frequency handover
UE capability
• Make sure inter-frequency HO is also supported on the UE
side.
– For example, for Qualcomm chipset: QCT3.0 is needed.
• How to find UE capability: check Feature Group Indicator IE
in UE Capability Info message (S1AP or RRC). Bitmap
decoding explained in Annex B, 3GPP TS 36.331
– Not all tools support automatic decoding of this IE!

S1 handover

Intra LTE Handover via S1
Extended mobility option to X2 handover
• Applicable for intra and inter frequency HO
and only for inter-eNB HO
• DL Data forwarding via S1
• Handover in case of
– no X2 interface between eNodeBs, e.g.
not operative, not existing or because
blacklisted usage
– eNodeBs connected to different CN
elements
Feature ID(s): LTE54
RL20
• For the UE there is no difference whether the HO is executed via X2 or S1
interface
• HO reasons ‘better cell HO’ (A3) and ‘coverage HO’ (A5) are supported
• MME and/or SGW can be changed during HO (i.e. if source and target
eNodeB belong to different MME/S-GW)
RL15TD

Intra-LTE handover via S1
Parameter settings 1/2
• S1 handover doesn’t seem to be enabled in live networks but it is normally tested
to ensure the proper configuration and functioning
• Following MOC have to be adapted/created for setting up S1-based HOs:
1. The S1 handover feature needs to be enabled in LNBTS by:
true
2. If the target eNB is able to perform X2-based handovers the target cell has to
be blacklisted for X2 handover. E.g. for functionality testing of S1 HO, the X2
neighbour cell needs to be blacklisted:
LNCEL object:
<list name="blacklistHoL">
<item>
onlyX2
65536
n8
pci
</item>
</list>

Intra-LTE handover via S1
Parameter settings (2/2)
3. LNADLP (Target cell for S1 Handover) needs to be created perS1 neighbour cell
LNBTS object:
<managedObject class="LNADLP" distName="LNBTS-1001/LNADLP-1"
operation="create“
<list name="adjBcPlmnIdOp">
<item>
MCC
MNC
length
<…>
ARFCN
pci
tac
0
</managedObject>
• Note: On RL30, LNADLP object has been removed.

RRC release with redirect

RRC connection release with redirect
• When the serving cell RSRP is very low, the eNodeB can redirect the call
to another LTE frequency or another radio access technology (RAT).
• This is not the same as a handover. The UE does not perform
measurements on the neighbouring frequency or RAT before the RRC
connection is released.
• Can be seen as an ”emergency” measure – when the coverage is so low
that there is a risk of loosing the signalling connection to the UE. ”Last
option” before the call drops.
• 3GPP event A2 is used to define an absolute threshold for the redirection
– LNCEL:threshold4
• The parameters related to RRC release with redirect are defined in the
REDRT object.
LNBTS
LNCEL
REDRT

Mobility LTEWCDMA
E-UTRA
RRC_CONNECTED
E-UTRA
RRC_IDLE
Cell_DCH
UTRA_Idle
Cell_FACH
PS
CS
CSFB via redirect
LTE 562: CS fallback
LTE 762: reselection
RAN2067: reselection
Cell_PCH/URA_PCH
LTE WCDMA

• Redirect feature can be enabled on LNBTS level:
[..] RRC: MEASUREMENT REPORT
RRC: RRC CONNECTION RELEASE
event A2
for redirection
target RAT
indicated
enableCovHo
LNBTS; 0 (disabled), 1 (enabled);
1 (enabled)

LNCEL: threshold4 defines the absolute RSRP level of serving
cell for eNB to trigger RRC connection release with redirection.
RSRP
time
threshold4
-140 dBm
threshold4
A2 condition met
reporting condition met
after Time To Trigger
Measurement
Report
a2TimeToTriggerRedirect
Serving Cell RSRP
threshold4
LNCEL; 0..97dB; 1dB; - ;
1dB -> RSRP = -139dBm
LNCEL; 0ms (0), 40ms (1), 64ms (2), 80ms
(3), 100ms (4), 128ms (5), 160ms (6),
256ms (7), 320ms (8), 480ms (9), 512ms
(10), 640ms (11), 1024ms (12), 1280ms
(13), 2560ms (14), 5120ms (15); - ;
256ms (7)

• The redirection can be defined to another LTE frequency/layer, or to
another RAT.
• It is possible to define several REDRT objects, and each REDRT
frequency/RAT have different priorities. However, since the UE does not
perform measurements on the target frequency/RAT before the
redirection, it is not as in a handover where the UE chooses the most
appropriate frequency/RAT where the coverage is best.
• The selection of which frequency/RAT to redirect the call to (if there are
several REDRT object) is only based on UE capabilities, not coverage.
• Example: For LTE2600 cells, there is one REDRT object towards
LTE1800 (highest priority), and one object towards WCDMA (lower
priority). The eNodeB will remember the UE capability information sent
when the UE attached. If the UE is capable of LTE1800, it will redirect the
call to LTE1800, since this has highest priority. If the UE does not support
1800 MHz, the eNodeB will redirect the call to WCDMA instead.
• Note: Priority 1 is highest! (Not like for the other priority parameters where
7 is highest and 1 is lowest )

REDRT

RRC release with redirect, LTE2600-LTE1800
Signalling example from Nemo
UE is
on
2600
RRC connection is released and redirected to the LTE1800 carrier (1832).

RRC release with redirect, LTE  WDCMA
Signalling example from Nemo
UE is redirected to
WCDMA carrier 10737
UE is
in LTE
UE is
in 3G

FTP download – LTE1800->3G
redirection

RRC release with redirect, throughput vs time
Throughput vs time for RRC release with redirect from LTE2600 to LTE1800. We can see
that throughput drops to zero for a short time, and then comes back up on the new
frequency.
release release

RRC release with redirect, Nemo screendump
Connection
manager in 3G
Throughput over
25Mbit in LTE
Throughput around
10Mbit after a couple
of seconds gap and
then redirection to
3G

Redirect failure due to UE Network Mode setting
Problem summary:
– High RRC and E-RAB Drop Ratio in live TeliaSonera LTE1800 Network
0.00
20.00
40.00
60.00
80.00
100.00
120.00
29/09/2011
30/09/2011
01/10/2011
02/10/2011
03/10/2011
04/10/2011
05/10/2011
06/10/2011
07/10/2011
08/10/2011
09/10/2011
10/10/2011
11/10/2011
12/10/2011
13/10/2011
14/10/2011
15/10/2011
16/10/2011
LTE_5237a E-RAB Release Failure Ratio, EPC init RNL (%) LTE_5090a E-RAB Release Failure Ratio, eNB init RNL (%)
TSDK LTE Optimisation Learning / Evan Lu / 2011-11-02

Analysis Results:
– Only a couple of sites are affected, but because the ZTE connection manager has an
auto-connect feature, one problematic UE can cause thousands of drops in one day. UE
drops -> automatically connects again -> drops etc etc.
– According to eNB traces collected from most affected sites, the drops occur in case when
conditions for RRC connection release with redirect are met on UE side
– The redirect failure is due to “LTE only” Network mode setting of UE by end user. In this
mode UE does not provide any IRAT capabilities to the eNB within “UE Radio Capability”
IE so eNB decides that redirect to 3G WCDMA is not supported by UE and releases the
call after Measurement Report A2.
Solution Options:
– eNB SW RL20 EP4.0 - No A2 triggered RRC Connection Release without redirect in case
target frequency layer or IRAT for redirect is not supported by UE according to “UE Radio
Capability” IE
– Change threshold4 from -110dBm to -120? -126? -130? Risk of quality degradation to all
LTE end users in whole network.
– Inform end users to change UE Network Mode setting from 4G only to 4G preferred

Parameter settings for Redirect in live TeliaSonera LTE1800 Network:
According to drive test results performed at the beginning of October, ZTE UE is performing
very unstable under lower threshold settings.
RSRP
time
-110dBm
-140 dBm
threshold4=30
A2 condition met
reporting condition met
after Time To Trigger
Measurement
Report
Serving Cell RSRP
threshold4
LNCEL; 0..97dB; 1dB; -
Baseline is -140dBm

RRC: MEASUREMENT REPORT
RRC: RRC CONNECTION RELEASE
event A2
for redirection
(Serving LTE Cell
RSRP falls below -
110dBm)
cause: other
(no target RAT
Indicated!!!)
Failure scenario in TeliaSonera live LTE1800 Network:
UE Context Release: due to eutran generated reason

Data Radio Bearer
Commercial Launched Threshold4 Tuning
Improved

E-RAB Release/Drop
Commercial Launched Threshold4 Tuning
60% drop rate
15% drop rate

IRAT HO to WCDMA

Inter RAT Handover to WCDMA
2. Handover preparation:
▪ Resource allocation on target side (E-RAB
parameters mapped into PDP context)
3. Handover execution:
▪ UE moves into WCDMA cell after receiving
‘MobilityfromEUTRACommand’ message
4. Handover completion:
▪ Release of S1 connection and internal
resources after successful HO (no timers
expired)
RL30
RL25TD
• IRAT hard handover from LTE to WCDMA PS domain through S1 interface
• Phases:
1. Handover initiation:
 eNB starts a HO to WCDMA following a received measurement report with event B2
 Max. 8 cells reported (strongest first) that create the TCL (target cell list)

Inter-RAT Handover to WCDMA
Event B2
• Handover from LTE to WCDMA is triggered by poor LTE radio coverage and
sufficient WCDMA cell radio signal quality
• Radio conditions for serving and neigbour cells are defined with event B2
Entering conditions
1. Ms + Hys < Thresh1
and
2. Mn + Ofn – Hys > Thresh2
Leaving conditions
1. Ms - Hys > Thresh1
or
2. Mn + Ofn + Hys < Thresh2
Ms -> RSRP of serving cell
Mn -> RSCP/EcN0 of neigbour cell
Thresh1 -> b2threshold1Utra -> refers to signal level of serving cell
Thresh2 -> b2threshold2UtraRSCP/EcN0 -> refers to signal level of neighbour cell
Hys -> hysB2ThresholdUtra -> hysteresis to prevent ping-pong effect between
entering and leaving conditions; parameter common for both
serving and neigbour cell
Ofn -> OffsetFreqUtra -> refers to neighbour cell only
reportConfigInterRAT
measObjectUTRA

Inter-RAT Handover to WCDMA
Event B2
Entering condition:
RSRP,s < b2threshold1Utra – hysB2thresholdUtra AND
utraRSCP/EcNo,n > b2theshold2UtraRscp/EcNo- offsetFreqUtra + hysB2ThresholdUtra

HO to WCDMA Steps
Simplified
UE MME
Target
RNC
Source
eNB
P-GW
S-GW SGSN
RRC: Measurement Report
target WCDMA cells
RRC: RRC Connection Reconfiguration
LNCEL: A1, A2 & LNHOW: B2 thresholds & LNADJW: WCDMA frequency & scrambling code
Decision to perform
WCDMA HO
S1AP: Handover Required
LNADJW: target WCDMA cell
S1AP: Handover Command
Handover Preparation
RRC: Mobility From EUTRA Command
S1AP: S1 Application Part Protocol
1
Measurements activation/deactivation of
WCDMA based on A2/A1 events. UE
measurement reports triggered by event
B2
2
3
4
5
6

Configuration aspects
New objects and Parameters respect RL20
• LNHOW: For each predefined EUTRA (utraCarrierFreq) defines event B2 related
parameters
• LNADJW: Defines WCDMA neighboring cell(s)
• New parameters in already existing objects LNBTS, LNCEL are introduced

Configuration
LNBTS
• LNBTS/LNADJW to define
candidate 3G neighbor cell
information for handover
• Identifier 0 originally a bug
• LNCEL/Related LNADJW
instance list needs to be
created with “WCDMA Cell
Index ID” according to 3G
neighbor lists need for that
LTE cell. Create per 3G
neighbor cells
• actHOtoWcdma enables
the feature Handover from
LTE to WCDMA
LNADJW-x = LNADJW: lnAdjWIndex

Configuration
LNCEL
• LNCEL/LNHOW
needs to be created
per 3G neighbor
frequency
• One LNHOW
needed per
frequency
• LNCEL/UFFIM
needs to be
created per 3G
neighbor
frequency for
cell reselection

CS Fallback

CSFB to UTRAN or GSM via redirect RL20
CSFB: Call Setup Fallback
IE: Information Element
• Required when there is no Conversational Voice support on LTE side
• Redirection from LTE to UTRAN or to GSM during the call setup. MOC and
MTC setup supported
MOC: Mobile Originated Calls
MTC: Mobile Terminated Calls
• EPC must support
CS inter-working for
mobility
management and
paging
• Redirection by RRC connection release message with a RedirectedCarrierInfo
IE that enforces the UE to search for any cell first at the highest priority UTRA
carrier or within BCCH carrier set for GSM
• UEs supporting CS fallback may stay in current RAT of camp back into the LTE
carrier after termination of the CS call

Configuration
LNBTS, LNCEL, UFFIM, GFIM
• CS fallback needs to be enabled via LNBTS:actCSFBRedir
• Redirection technologies (WCDMA or GSM) need to be configured: UFFIM for
WCDMA and GFIM for GSM
• Activation of SIB6 for WCDMA and
SIB7 for GSM ( within LNCEL)
Screenshots for WCDMA case

Configuration
REDRT
• Necessary to create the REDRT object indicating the RAT for redirection and the
priority for CS fallback with redirection

CS Fallback Signalling Example
MOC in ECM_Connected
UE needs to be
IMSI attached
UE starts Initial Access
procedure and sends
Extended Service Request
message with Service Type
set to “mobile originating CS
fallback”
eNB send
“RRCConnectRelease”
message with redirect
information of WCDMA
Frequency to be used
for redirection
Further examples ( ECM_IDLE, MTC) in:
https://sharenet-
ims.inside.nokiasiemensnetworks.com/Overview/D4376
59035

Successfully MOC to WCDMA

ANR – Automated Neighbour Relations

ANR – Automated Neighbour Relations
Overview
• RL10: LTE539 – Central ANR
– Configurator triggers NetAct Optimizer via eNB Auto Configuration
workflow (pre-planning step)
– NetAct Optimizer creates and provides a list of neighbor eNBs and
physical cell ID (PCI) values
• RL20/RL15TD: LTE492 – ANR for LTE
– NetAct Optimizer creates a list of potential neighbour cells and related
IP connectivity information
– Works with any UE
• RL30/RL25TD: LTE782 – ANR for LTE fully UE based
– Optimizer not needed, but requires SON/ANR-supporting UE.

ANR
RL20/RL15TD: ANR support for LTE with OAM extension (LTE492)
• each newly activated Flexi Multiradio BTS is provided with table that maps
Physical Cell Id & DL EARFCN of adjacent cells to C-plane IP address of
their parent eNBs
• PCI/RF/IP@ mapping tables are generated by NetAct based on the
neighbour site relations analysis and downloaded to BTS during auto-
configuration procedure
• based on PCI/RF/IP@ mapping table, eNB is able to determine adjacent
eNB hosting unknown cells and to retrieve from it necessary (in the
context of neighbour relations) configuration information
• X2 connection setup procedure is triggered by UE measurement reports
containing PCI that is not known to eNB as a neighbour cell but is listed in
PCI/RF/IP@ mapping table
• target eNB accepts incoming X2 connection setup requests from a source
eNB even if no IP-address of the source eNB is configured on the target
site

ANR
RL20/RL15TD: ANR support for LTE with OAM extension (LTE492)

ANR
RL30/RL25TD: LTE782 – ANR for LTE fully UE based
• for unknown UE-reported cells (PCI unknown to eNB) operating on the
same frequency as the serving cell, the corresponding EUTRAN Cell
Global ID (ECGI) is derived with the help of the UE measurements
– UE must support decoding and delivery of ECGI on request coming from eNB
• derived ECGI is used as input to an IP@ resolution procedure over S1 IF
– eNB retrieves, with the help of MME, C-plane IP@ needed to setup X2
connection towards the neighbour eNB parenting the UE-reported cells
– no need for predefined PCI-to-IP@ mapping tables
• automated detection and configuration of unknown intra-frequency
neighbour cells without operator involvement and planning efforts -
no neighbour relation information has to be provided by the operator
via O&M

eNB-B
IP@B
ANR
Phy-ID: physical cell ID
GID: Cell Global ID
2. RRC measurement
report (Phy_ID=3)
1. Measure the signal ( Phy_ID=3)
4. Read GID (“B10”) from BCCH
3. Report request
to report GID for Phy_ID=3
5. Report
GID=“B10”
eNB-A
IP@A
0. UE Measurement Configuration
when UE enters RRC_CONNECTED
Goal: retrieve Global Cell ID from newdiscovered neighbor cell

MME
ANR
Site
eNB - A
Neighbor
Site
eNB - B
New cell
discovered
New cell
identified
by GID
CM
X2 Setup : IPsec, SCTP, X2-AP [site & cell info]
UE
connected
S1 : Request X2 Transport Configuration (GID)
S1: Request X2 Transport Configuration
relays
request
S1: Respond X2 Transport Configuration (IP@)
S1 : Respond X2 Transport Configuration (IP@)
CM
relays
response
Add Site & Cell
parameter of
eNB-A
CM CM
Add Site & Cell
Parameter of
eNB-B
Neighbor Cell Tables in both eNB updated

LTE782 – ANR for LTE fully UE based
signalling example
• The PCI 232 is unknown LTE neighbour cell
and eNB requests UE to decode and report
ECGI of this cell.
/

Connected mode mobility
Exercise – inter-frequency A5 handover
• Operator X has an existing LTE network on 2600MHz, now
they want to launch LTE on 1800MHz also. They have 20MHz
BW on 2600 and only 10MHz BW on 1800, so they want to
keep the traffic as long as possible on the 2600MHz layer.
• Which threshold are suitable for inter-frequency A5 handover
for the 1800 cells? Do any parameters need to be changed
for the 2600 cells?
• Existing thresholds for LTE2600 cells:
– Threshold1: 90
– Threshold3: 45
– Threshold3a: 48

Idle Mode Mobility

SIB and SIB mapping

System Information Blocks (SIBs)
• UE reads the system information within Idle mode to acquire parameters needed
to complete cell selection and reselection
• System information is broadcast using a Master Information Block (MIB) and a
series or System Information Blocks(SIB)
• SIB1..3 are mandatory
• SIB 4,5,6,7,8 are optional and are defined within LNCEL
More info: TS36.331

siXMappingInfo Parameter
• LNCEL/siXMappingInfo parameter indicates which System Information Block is
contained in the SI-X message. Values: SIB4(2), SIB5(3), SIB6(4), SIB7(5), SIB8
(6), notUsed (18)
SI: System Information
MOC: Managed Object Class
• If ‘SIB4’ is defined in any LNCEL/siXMappingInfo
where X={4,5,6,7,8} then the MOC IAFIM (iafimId)
object must be defined
• If 'SIB5' is defined in LNCEL, then MOC IRFIM (irfimId)
needs to be created
• If 'SIB6' is defined in LNCEL, then MOC UFFIM
(uffimId) needs to be created
• If 'SIB7‘ is defined in LNCEL, then MOC GFIM (gfimId)
needs to be created
• If 'SIB8‘ is defined in LNCEL, them MOC CDFIM
(cdfimId) needs to be created
• Example where only si4MappingInfo is configured
indicating that SI-4 carries the SIB4 information:

Cell selection

Cell Selection
• Procedure by which the UE camps on a cell
• UE searches for a suitable cell creating a potential list of candidates (strongest cell
measured and its neighbours) and then each candidate is evaluated according to
the S-criteria
• The UE selects a cell if Srxlev > 0
• SIB1 is used to transmit cell selection parameters
LNCEL: qRxLevMinOffset
Typically 0 (only used when camping in VPLMN)
VPLMN: Visited PLMN
Max(LNCEL:pMaxOwnCell - P_max from UE (*) , 0)
Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) – P_compensation
Measured value
LNCEL:qRxLevMin
Typically -130dBm
(*) P_max from UE : UE class specific
max. UL Tx power; 23 dBm
pMaxOwnCell (SIB1)
Used to calculate
P_compensation
LNCEL; -30..34dBm; 1dBm; -

S – Criterion Cell Selection
P_compensation = max(pMaxOwnCell – P_max from UE, 0)
Cell size defining parameter:
• qrxLevMin I am
outside
I am inside,
but I have
not enough
power


If P_compensation > 0,
S-criteria is more difficult
to achieve. Avoids UEs
camping on cells for which
they have insufficient
power to access (towards
cell edge)
E.g. pMaxOwnCell: 33 dBm in GMC files
• qrxLevMin can be set up differently for intra frequency, inter frequency and IRAT:

Intra frequency cell reselection

Triggering Measurements
• When a UE is camped on a cell it looks for better candidate cells for reselection
according to sIntrasearch parameter:
• If Srxlev > sIntraSearch : UE doesn’t measure the neighbour cells
• If Srxlev <= sIntraSearch : UE starts to measure neighbour cells on the same
frequency
• Example:
– LNCEL: sIntraSearch is 62 dB
– LNCEL: qRxLevMin is -130 dBm
– LNCEL: qRxLevMinOffset is 0
– pCompensation is 0
• Qrxlevmeas< - 68 dBm
• UE will start to measure intra-frequency neighbours when RSRP is worse than
- 68 dBm
-130 dBm
Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) - pcompensation

R-Criterion (Ranking Criterion)
• Once the measurements for neighbor cells have been triggered the UE will rank
the measured cells which fulfill the S-Criterion according to the R-Criterion
– Rankserving cell = Measured RSRPserving cell + LNCEL:qHyst
– Rankneighbour cell = Measured RSRPneighbour cell – IAFIM:qOffsetCell
• Re-selection if :
– Rankneighbour cell > Rankserving cell for tReselEutr and
– More than 1 second has elapsed since the UE camped on the current serving
cell

SIB3
• SIB3 carries the cell reselection parameters (serving cell information)
• All these
parameters are
part of LNCEL
object

SIB4 and IAFIM (1/2)
• IAFIM parameters are broadcasted in SIB4 (neighbour cell information)
• SIB4 contents are
optional!
• Intra Frequency Neighbours plus offsets
• Intra Frequency Blacklisted Cells
• CSG reserved cells i.e. for Home eNB -> not implemented
CSG: Closed Subscribed Group

SIB4 and IAFIM (2/2)
• IAFIM only needs to be created to give some special cell reselection offset (other
than 0) to certain neighbour cells or to blacklist cells
Practice:
• Recommendation is to create a ‘dummy’ SIB4 as it is required for certain terminals
e.g. Huaweii LTE-USB sticks otherwise they crash
• If IAFIM object is created them either blacklisted cells OR neighbour cells need to
be defined
– It is enough to configure a ‘dummy’ PCI in IAFIM
– SIB4 periodicity in this case can also be longer
•
Theory:
• All parameters in IAFIM are optional i.e.
– No need to define intra-frequency idle
mode neighbours
– UE does not need SIB4 as it evaluates
the available found neighbour cells +
any additional cells defined in SIB4 if
configured

Practical Experience
• qOffsetCell (the offset for the neighbouring cells) is in the IAFIM object and has to
be defined separately for each neighbour relation (defined by the neighbours’
PCI).
• Issue: It is not convenient to maintain. E.g. If creating a new PCI plan it is also
necessary to change the PCIs in all the IAFIM objects
• Solution: To ”move” all the offset to the qHyst (the offset for the serving cell)
• E.g. instead of defining qHyst = 1dB and qOffsetCell = 2 dB to change qHyst to 3
dB and qOffsetCell to 0 (or don’t define the IAFIM at all)

Practical Experience: Example
• In the Telia Denmark network:
– LNCEL:qHyst was set to 1 dB
– IAFIM:qOffsetCell was set to 2dB, only defined for intra-site neighbours
• This meant:
– when reselecting to intra-site neighbours: total hysteresis was 3 dB (2+1)
– When reselecting to non intra-site neighbours: total hysteresis was 1 dB (as no
qOffsetCell was defined for the other neighbours)
– 1 dB of hysteresis is too little leading to many cell reselections
List only contains offset
for the two intra site
neighbours

Idle mode PCI plot
Before parameter change, cell
reselections happening too often
After parameter change, less
ping pong between cells

Blacklisting
• If an operator wants to prohibit UEs to camp on certain cells, these cells can be
blacklisted
• The blacklisted PCIs are defined by the parameters IAFIM:startIntraPci and
IAFIM:rangeIntraPci
• Together, these two parameters define the blacklisted PCIs
– startIntraPci defines the lowest PCI in the range
– rangeIntraPci defines the number of PCIs in the range
• There can be 16 ranges in total
PCI 1-4 are black listed

Inter frequency cell reselection

• Measurement trigger depends on the absolute priorities of the serving and non-
serving layers
• The priority of the serving layer is defined in the parameter LNCEL:cellReSelPrio
• For each neighbouring frequency/layer, it is necessary to define the corresponding
priority: IRFIM:eutCelResPrio (7 is highest priority, 0 is lowest)
• For equal priority frequency layers it is possible to define an offset with
IRFIM:qOffFrq
• If IRFIM:eutCelResPrio > LNCEL:cellReSelPrio then measurements of the
neighbour cell are mandatory
• If IRFIM:eutCelResPrio <= LNCEL:cellReSelPrio then measurements are
performed when RSRP of serving cell is below Snonintrasearch threshold:
Srxlev <= SNonIntrsearch

• UE starts inter-frequency measurements when Srxlev <= sNonIntrSearch
• sNonIntrsearch is a valid threshold for inter-frequency and inter-RAT
measurements
• Example:
– LNCEL: sNonIntrSearch is 12 dB
– LNCEL: qRxLevMin is -130 dBm
– LNCEL: qRxLevMinOffset is 0
– pCompensation is 0
• Qrxlevmeas <=-118 dBm
• UE will start to measure inter-frequency neighbours when RSRP is worse than
-118 dBm
-130 dBm
Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) - pcompensation

Inter Frequency Reselection
R-criteria: Equal priority between layers
• Similar to intra frequency
• A frequency-specific offset for equal priority E-UTRAN frequencies can be
considered:
Qoffset = qOffCell,n + qOffFreq

R-criteria: Reselection to higher priority layers
• If the neighbouring cell layer has higher priority than the serving layer,
reselection will happen if:
Srxlevneighbour > IRFIM:interFrqThrH
Where:
Srxlevneighbour = Qrxlevmeas – IRFIM:qRxLevMinInterF - pcompensation
• The criteria above must be satisfied for a time period equal to IRFIM: interTResEut
• And the UE must have been camped in the current cell more than 1 sec.
Qrxlevmeasneighbour > qRxLevMinInterF + interFrqThrH
(Assuming pcompensation = 0)
interFrqThrH > interFrqThrL > threshSrvLow

R-criteria: Reselection to lower priority layers
• If the neighbour cell layer has lower priority, the reselection will happen if:
Srxlevneighbour > IRFIM:interFrqThrL && Srxlevserving < LNCEL:threshSrvLow
Where:
Srxlevneighbour = QrxlevMeasneighbour – IRFIM:qRxLevMinInterF – pcompensation
Srxlevserving= QrxlevMeasserving – LNCEL:qRxLevMin + LNCEL: qRxLevMinOffset –
pcompensation
• The criterias above have to be fullfilled during a time interval IRFIM:interTResEut
• And the UE must have been camped in the current cell more than 1 sec.
Qrxlevmeasserving < qRxLevMin + thresholdSrvLow – qRxLevMinOffset +
pcompensation
AND
Qrxlevmeas neighbour > qRxLevMinInterF + interFreqThrL + pcompensation
interFrqThrH > interFrqThrL > threshSrvLow

Example of reselection to lower priority
-130
LNCEL:qRxLevMin = -130 dBm
LNCEL:threshSrvLow = 10
If suitable neighbour (*) cell is found, reselection will be
performed when RSRP decreases under -120 dBm
-120
-118
Inter frequency measurements
will be started at -118 dBm
LNCEL:sNonIntrSearch = 12
-140
RSRP decreases
Pcompensation =0
LNCEL:qRxLevMinOffset =0
(*) suitable neighbour-> RSRP> qRxLevMinInterF +interFreqThrL

IRFIM object
• Idle mode mobility between two different LTE frequency layers, e.g. LTE 2600MHz
for capacity sites and LTE 800MHz for coverage sites
• IRFIM parameters are
broadcasted in the SIB5
IRFIM object

Inter RAT cell reselection

• Inter RAT cell reselection is idle mode mobility from LTE to another radio access
technology (RAT), e.g. WCDMA or GSM
• UFFIM is the managed object class for idle mode parameters LTE->WCDMA:
– UFFIM parameters are broadcasted in the SIB6
• GFIM and GNFL are the managed object classes for idle mode parameters LTE-
>GSM:
– GFIM/GNFL parameters are broadcasted in the SIB7
LNBTS
LNCEL
UFFIM
LNBTS
LNCEL
GFIM
GNFL

Measurements Trigger
• IRAT cell reselection procedure and related parameters are similar to those for
inter frequency cell reselection
• Similar to the inter frequency case, there is the priority concept (7 is highest
priority, 0 is lowest):
– The priority of serving cell is defined with LNCEL:cellReSelPrio
– The priority of the neighbouring cell is defined:
▪ For WCDMA: UFFIM: uCelResPrio
▪ For GSM: GFIM: gCelResPrio
• If UFFIM: uCelResPrio/GFIM: gCelResPrio > LNCEL:cellReSelPrio then
measurements of the neighbour WCDMA/GSM cell are mandatory
• If UFFIM: uCelResPrio/GFIM: gCelResPrio <= LNCEL:cellReSelPrio then
measurements are performed when RSRP of serving cell is below
Snonintrasearch threshold (same as per inter-frequency):
Srxlev <= SNonIntrsearch

R-criteria
• Reselection to a higher priority RAT will happen if:
WCDMA: Srxlevneighbour > UFFIM:utraFrqThrH
GSM: Srxlevneighbour > GFIM:gerFrqThrH
• Reselection to a lower priority RAT will happen if:
• The criterias above have to be fullfilled during a time interval UFFIM:tResUtra for
WCDMA and GFIM:tResGer for GSM
• And the UE must have been camping in the current cell more than 1 sec.
GSM:
Srxlevneighbour > GFIM:gerFrqThrL &&
Srxlevserving < LNCEL:threshSrvLow
WCDMA:
Srxlevneighbour > UFFIM:utraFrqThrL &&
Srxlevserving < LNCEL:threshSrvLow
utraFrqThrH > utaFrqThrL > threshSrvLow gerFrqThrH > gerFrqThrL > threshSrvLow

R-criteria
• Srxlevneighbour is referred to the candidate cell:
• GSM: Srxlevneighbour = QrxlevMeas – Qrxlevmin – P_compensation
Where:
QrxlevMeas = RSSI
Qrxlevmin = GNFL:qRxLevMinGer
• UMTS: Srxlev = QrxlevMeas – Qrxlevmin – P_compensation
Where:
QrxlevMeas = CPICH RSCP
Qrxlevmin = UFFIM:qRxLevMinUtra
Additionally Squal > 0 required for UMTS FDD
Squal = QrxlevMeas – Qqualmin
Qrxlevmeas = CPICH Ec/No
Qqualmin = UFFIM:qQualMinUtra

SIB6 and UFFIM object
• SIB6 and UFFIM with priorities and reselection
thresholds towards 3 different WCDMA carriers

LTE  3G cell reselection, signalling example
UE is
in LTE
UE is
in 3G

Settings on WCDMA side (1/2)
• ‘RAN2067 LTE interworking feature’ needs to be activated
• Software needs to be appropriate e.g. WBTS SW BTS WN6.0 PP2.03 and activated
on all WCDMA sites
• ‘LTE Cell Reselection in WCEL needs to be enabled
• RNC setting for SIB19

08 April 2022
121
• ADJL configuration
Settings on WCDMA Side (2/2)

LTE to GSM reselection
bandInd
• SIB7 needs to be activated
• Mandatory parameter: GNFL/bandInd
• It distinguishes between GERAN frequency bands if ARFCN values are associated
with either GSM1800 or GSM1900. Values: gsm1800 (0) or gsm1900 (1)
• If other ARFCN bands then the parameter although mandatory is not relevant
• E.g. GNFL/gerArfcnVal = 1-124 (i.e. GSM900 frequencies) then bandInd can be either 0
or 1

Testing notes
Terminals and Measurement Tools
• Nemo is better than XCAL as it provides more information. XCAL also requires a
license upgrade to support Qualcomm chipset
• Terminals:
• ZTE MF820 with the following SW/FW
▪ Firmware : BD_ZTE_MF820V1.0.0.0B12
Software : PCW_TEAGLBLTEP18EMV1.0.0B15
▪ Cost: 265 EUR
• ZTE poor performance:
• When 2 LTE layers (LTE1800 and LTE2600) it camps on LTE1800 even if parameters
are set to camp in LTE2600. See next slide for example.
• Frequent crashes
• Difficult communication with ZTE
• Bandrich UE (C501, Qualcomm chipset):
• Requires engineering mode to see L3 messages (2600 eur vs. 140 eur normal mode).
• Known issues: https://twiki.inside.nokiasiemensnetworks.com/bin/view/LTESyVe/BandrichC501
• Inter frequency HO not supported
• Idle Mode IRAT between GSM and LTE not supported

Inter-frequency cell selection and reselection
Problem with ZTE MF820D
Red/brown: UE is camping
on LTE2600
Blue: UE is camping on
LTE1800
Pink sites: LTE2600
Green sites: LTE1800

Idle mode mobility
Exercise
• Operator X has two layers for LTE, 2600 and 1800.
• 2600 has highest priority, 1800 has second highest priority.
The operator also has WCDMA.
• Define suitable idle mode parameters for 2600 cells and 1800
cells, respectively. The parameters should enable both LTE
intra-frequency mobility and inter-frequency mobility as well
as inter RAT mobility from LTE to WCDMA.

06a_LTE mobility management v1_0.ppt

More Related Content

What's hot

Similar to 06a_LTE mobility management v1_0.ppt

Recently uploaded

06a_LTE mobility management v1_0.ppt