Not all measurements explained, only general things.

1. *
http://id.linkedin.com/in/sofian/
http://babakhalid.com/

2. LTE MEASUREMENT
- LIST List of detected preambles
The eNB shall report a list of detected PRACH preambles to higher layers. Higher layer
utilize this info for the RACH procedure
Transport BLER
The ACK/ NACKs for each transmission of the HARQ process are reported to the MAC.
Based on these ACK/NACKs the higher layers compute the BLER for RRM issues.
TA
The eNB needs to measure the initial timing advance (TA) of the uplink channels based on
the RACH preamble.
Average RSSI
Measured in UL by eNB. It can be used as a level indicator for the UL power control. The
RSSI measurements are all UE related and shall be separately performed for ( TTI
intervals)
· UL data allocation (PUSCH)
· UL control channel (PUCCH)
Sounding reference signal (SRS)
Average SINR
In UL the eNB measures SINR per UE. The average SINR can be used as a quality indicator
for the UL power control
UL CSI
Channel state information per PRB for each UE. The CSI shall be the received signal power
averaged per PRB.
1

3. LTE MEASUREMENT
- LIST Intra LTE measurements ( from LTE to LTE)
UE measurements
• CQI measurements
• Reference Signal Received Power (RSRP)
• Reference Signal Received Quality (RSRQ)
eNB measurements
• Non standardized (vendor specific):TA, Average RSSI, Average SINR, UL CSI, detected
PRACH preambles, transport channel BLER
• Standardized:DL RS Tx Power, Received Interference Power, Thermal Noise Power
Measurements from LTE to other systems
UE measurementsare mainly intended for handover
•
•
•
•
UTRA FDD:CPICH RSCP, CPICH Ec/No and carrier RSSI
GSM:GSM carrier RSSI
UTRA TDD:carrier RSSI, RSCP, P-CCPCH
CDMA2000:1xRTT Pilot Strength, HRPD Pilot Strength
2

4. LTE MEASUREMENT
SAMPLES
REFERENCE SIGNAL RECEIVED POWER (RSRP)
The received power on the resource elements that carry cell-specific
reference signals
3

5. LTE MEASUREMENT
SAMPLES
REFERENCE SIGNAL RECEIVED POWER (RSRP)
There is dependency between RS power and Max Total Tx Power. The relation is given by
PRS = PTx, Max – 10* log (NRB *12)+ 10*log (Pb+1)
where PRS
= RS power per RE (dBm)
PTx, Max = Max eNodeB power per Tx (dBm)
NRB
= number of resource block
Pb
= RS power boosting constant (actual value range = 0~3) recommended value: single antenna = 0, double
antenna =1)
• The higher the maximum transmit power of eNodeB, the higher is the RS power.
• Besides, the RS power also affected by the RS power boosting constant, Pb. A larger value of Pb results in larger increase in RS
4
power, better channel estimation & PDSCH demodulation performance.
Huawei recommended setting for Pb is 0 (single antenna) & 1 (dual antenna)

6. LTE MEASUREMENT
SAMPLES
Reference Signal Received Quality (RSRQ)
The relation of N times the Reference Signal Received Power divided by the
total received power in the channel bandwidth. Within the RSRQ also the
noise and interference contributions are considered.
5

7. LTE MEASUREMENT
TIMING ADVANCE
TIMING ADVANCE (TA)
When UE wish to establish RRC connection with eNB, it transmits a Random Access
Preamble, eNB estimates the transmission timing of the terminal based on this. Now eNB
transmits a Random Access Response which consists of timing advance command, based
on that UE adjusts the terminal transmit timing.
3GPP TA Requirements
• Timing Advance adjustment delay
UE shall adjust the timing of its uplink transmission timing at sub-frame n+6 for a timing
advancement command received in sub-frame n.
• Timing Advance adjustment accuracy
The UE shall adjust the timing of its transmissions with a relative accuracy better than or equal to
4* TS seconds to the signalled timing advance value compared to the timing of preceding uplink
transmission. The timing advance command is expressed in multiples of 16* TS and is relative to the
current uplink timing.
In GSM
Dist = TA * bit-period * light-speed / 2
bit-period = 48/13 (3.69) μs
light-speed = 300000 km/s
6

8. LTE MEASUREMENT
SAMPLES
In LTE
No DL TA
Maintenance of Uplink Time Alignment
The UE has a configurable timer timeAlignmentTimer which is used to control how long the UE is
considered uplink time aligned
• When a Timing Advance Command MAC control element is received then UE applies the Timing
Advance Command and start or restart timeAlignmentTimer.
• When a Timing Advance Command is received in a Random Access Response message then one of
following action is performed by UE.
- if the Random Access Preamble was not selected by UE MAC then UE applies the Timing
Advance Command and starts or restarts timeAlignmentTimer.
- else if the timeAlignmentTimer is not running then UE applies the Timing Advance
Command starts timeAlignmentTimer; when the contention resolution is considered not
successful then UE stops timeAlignmentTimer.
- else ignore the received Timing Advance Command.
• When timeAlignmentTimer expires UE flushes all HARQ buffers, notifies RRC to release PUCCH/SRS
and clears any configured downlink assignments and uplink grants.
7

9. LTE MEASUREMENT
SAMPLES
Timing Advance Command MAC Control Element
3GPP 36.321
The Timing Advance Command MAC control element is identified by MAC PDU subheader with LCID
value = 11101 (Timing Advance Command)
• R: reserved bit, set to "0"
• Timing Advance Command: This field indicates the index value TA (0, 1, 2… 63) used to control the
amount of timing adjustment that UE has to. The length of the field is 6 bits.
8

10. LTE MEASUREMENT
SAMPLES
Signalled granularity = 16 Ts = 0.52 μsec (corresponding to 78 m).
In GSM we got about 553m granularity.
Ts is basic time unit defined by 3GPP
Ts. = 1 / (2048 x 15000) sec = 1 / 30.720.000 = 0.0325520833 e-6
- 15000 = 15 kHz is passband for a subcarrier in LTE
- 2048 FFT-size
Radio frame Tf = 307200 x Ts = 10ms = 20 timeslots (in FDD)
1 timeslot = 15360 Ts
2048 x Ts = 1/15kHz
UMTS bandwidth is 5 MHz and it operates at a high
chip rate 3.84 Mcps/s, which contributes
to the better resolution in timing measurements
compared to GSM. The timing resolution in
UMTS with one sample per chip is ∼0.26 µs which
corresponds to the propagation distance of
∼78 m.
The frequency of TA is sent dependent on speed of
the UE. If UE speed
72km/h = 20m/s  update every 4s
500km/h = 130m/s  max every 2s
NodeB measuring TA based on
Recevide PUSCH on TTI basis
CQI reports on PUCCH
9

11. LTE MEASUREMENT
CQI
10

12. LTE MEASUREMENT
Cell Selection/ReSelection
When the UE is switched on, it attempts to establish a contact with a public land mobile
network (PLMN) using a certain radio access technology.
The overall process is divided into three sub-processes:
• PLMN selection and reselection to search for an available mobile network.
• Cell selection and reselection to search for a suitable cell belonging to the selected PLMN.
• Location registration to register the UE’s presence in a registration area
11

13. LTE MEASUREMENT
PLMN Selection
PLMN Selection
When an UE is switched on, it attempts to make contact with a PLMN. The selection of the PLMN could
be either automatically or manually.
• Automatic mode: Utilizes a list of PLMN to be selected in priority order.
• Manual mode: The mobile station indicates available PLMN to the user.
Normally the UE operates on its home PLMN. At home PLMN, the MCC & MNC match with PLMN identity
stored in USIM.
If the UE loses its present PLMN coverage, a new available PLMN is selected automatically or manually.
12

14. LTE MEASUREMENT
PLMN Selection
PLMN Selection
Service types
LIMITED SERVICE: emergency calls on an acceptable cell.
UE may camp to obtain limited service like emergency call. The minimum set of requirements for initiating an
emergency call in a UTRAN network are:
• The cell is not barred.
• The cell selection criteria are fulfilled.
NORMAL SERVICE: for public use on a suitable cell.
UE may camp on to obtain normal service. Such a cell shall fulfill all the following requirements:
• The cell is part of the selected / registered / equivalent PLMN
• The cell is not barred
• The cell is not part of a forbidden registration area
• The cell selection criteria are fulfilled
• In case of CSG cell it is part of the white list
OPERATOR SERVICE: For operators only on a reserved cell.
Reserved cell: When the cell status "reserved for operator use" is indicated and the Acces Class of the UE is 11 or
15 the UE may select/re-select this cell if in Home-PLMN
Barred cell: When cell status "barred" is indicated the UE is not permitted to select/re-select this cell, not even for
limited services.
This information is set by office data.
13

15. LTE MEASUREMENT
PLMN Selection
14

16. LTE MEASUREMENT
Cell Selection/Reselection
Cell Selection
Upon PLMN selection, UE uses “cell selection” for fast cell searching to camp on. To receive system information UE
tunes to the control channels. This procedure is known as "camping on the cell”.
The UE will then register its presence in the registration area of the chosen cell by NAS (Non Access Stratum)
registration procedure.
NAS registration procedure means the upper layer information is transmitted from UE to CN via AS (Access
Stratum). The NAS offers the E-UMTS service to the users. Cell selection is performed in RRC idle mode.
Control Plane Protocol Stack
The cell will be decided as suitable if it fulfils the cell selection criteria.
The purpose of camping on a cell is:
• To enable UE reception of system information from the selected PLMN
• To allow UE an RRC connection, accessing the network on the cell control channel.
• To receive paging and respond to paging messages on a tuned control channel in the registration area. The PLMN
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knows the tracking area of the cell in which the registered UE is camped.

17. LTE MEASUREMENT
Cell Selection/Reselection
Cell RE-Selection
If the UE finds a "better" cell, UE reselects it and camps on it. After camping on, UE monitors the system
information to get the quality threshold and performs measurements for the cell reselection evaluation procedure.
The UE evaluates whether or not a better cell exists.
The E-UTRAN controls the quality measurements for
cells to be reselected. The UE measurements are
triggered according to the serving cell quality level and
the threshold indicated in the system information. The
measurement must satisfy different requirements for
intra frequency, inter frequency or inter RAT (Radio
Access Technology) quality estimations.
Cell selection is performed in RRC idle mode. The
camping on a cell in idle mode enables the UE to receive
information from the network. UE stays in idle mode
until it transmits a request to establish an RRC
connection. After receiving the RRC connection set up,
the mode changes into connected mode.
16

18. LTE MEASUREMENT
CRITERIA Selection
PLMN Selection
The UE scans all RF channels in the UTRAN band according to its capabilities to find available PLMNs.
On each carrier, the UE searches for the strongest cell according to the cell search procedure (refer cell searching)
and read its system information in order to find out which PLMN the cell belongs to.
If the UE can read the PLMN identity, the PLMN and the measured signal strength is reported to the NAS: if: signal
>= - x dBm (high quality PLMN); without the measured signal strength if < x dBm.
17

19. LTE MEASUREMENT
CRITERIA Selection
PLMN Selection
18

20. LTE MEASUREMENT
CRITERIA Selection
CELL Selection
After selecting a PLMN, the cell selection process starts. The UE selects a suitable cell and the radio access mode
based on idle mode measurements and cell selection criteria. The UE searches a suitable cell of that PLMN to camp
on according to the following steps:
1) The UE creates a candidate list of potential cells to camp on by using one of the two search procedures:
• Initial Cell Selection UE scans all RF channels in the UTRAN band to find a suitable cell. On each carrier, UE
searches for the strongest cell and reads its system information. Once the UE has found the suitable cell for the
selected PLMN, the UE creates a candidate list consisting of this cell and its neighboring cells as received in
measurement control information.
• Stored Information Cell Selection (optionally) This procedure requires information stored from previously
received measurement control information elements (cell parameters, carrier frequencies, etc). After the UE has
found a suitable cell for the selected PLMN, candidate list is created same as the initial cell selection process.
2) Each cell on the candidate list is evaluated according to the selection criteria S as described below.
3) After selecting a suitable cell (S criterion fulfilled) for camp on, UE reports this event to NAS for registration
procedures. If the registration is successful, the UE enters into "camped normally“ state.
19

21. LTE MEASUREMENT
CRITERIA Selection
CELL Selection
If the UE is unable to find any suitable cell in the selected PLMN, the UE enters to "any cell selection" state.
Camped normally state : UE obtains normal service and performs the following tasks:
• Select and monitor the PCH of the cell.
• Performs system information monitoring.
• Performs necessary measurements for the cell reselection evaluation procedure.
• Execute the cell reselection procedure
If after cell reselection evaluation process a better cell is found, the cell reselection is performed. If
no suitable cel is found, the UE enters to next state “any cell selection”
Any cell selection: UE searches an acceptable cell of any PLMN to camp on. If an acceptable cell
is found, the UE reports to NAS and camp on this cell obtaining limited service. And UE enters to
“camp on any cell” state. If the UE can’t find any acceptable cell, it stay in this state.
Camped on any cell state: UE obtains limited service and periodically searches for a suitable cell
in the selected PLMN. If a suitable cell is found the states changed to Camped normally.
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22. LTE MEASUREMENT
CRITERIA Selection
PLMN, CELL Selection & ReSelection Flowchart
21

23. LTE MEASUREMENT
CRITERIA Cell Selection
S-CRITERION
The cell selection criterion S is a pre-condition for suitable cells.
22

24. LTE MEASUREMENT
CRITERIA Cell Re-Selection
R-CRITERION
The cell reselection evaluation process depends on whether Hierarchical Cell Structure (HCS) is used or not.
In order to perform cell reselection UE measures and ranks the neighbor cells.
For each type of neighbor cells (Intra-Frequency; Inter-Frequency; Inter-RAT, i.e. GSM) thresholds are definable.
Measurements of neighbor cells will be triggered if these thresholds are reached.
HIGH MOBILITY / MEDIUM MOBILITY / NORMAL MOBILITY:
For faster moving UEs the procedure alters - speed dependent scaling rules are applied.
If the number of (different cells) cell reselections during the past time period TCRmax exceeds NCR_H, high mobility
has been detected. If the number exceeds NCR_M, and not NCR_H, medium mobility has been detected.
23

25. LTE MEASUREMENT
CRITERIA Cell Re-Selection
R-CRITERION
In high/medium-mobility states, a UE:
• multiplies Qhyst by "Speed dependent ScalingFactor for Qhyst for high/medium mobility state" if sent.
• multiplies TreselectionRAT by "Speed dependent ScalingFactor for TreselectionRAT for * mobility state for RAT cells.
(RAT = EUTRAN, UTRAN, GERAN).
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26. LTE MEASUREMENT
CRITERIA Cell Re-Selection
Neighbor Cell Measurement
For inter-frequency and inter-system measurements,
depending on the UE capability, the network allocates
measurement gaps during which no data are sent for the
UE, so that the UE could perform the necessary
measurements using a single receiver.
During the measurement gaps, the particular UE cannot be
scheduled for data transmission, but the vacant resources
could still be used for other UEs, because of the shared
channel mechanism.
FOR INTRA-FREQUENCY AND EQUAL PRIORITY INTER-FREQUENCY CELLS:
(Re-) Selected cell is a suitable cell (e.g. fulfills the S criterion) and is the best ranked cell (has the highest R).
The UE shall however reselect the new cell, only if the following conditions are met:
• The new cell is better ranked than the serving cell during a time interval Treselections
• more than 1 second has elapsed since the UE has camped on the current serving cell.
The cell-ranking criterion R is defined as shown below:
Note,
s – indicates the serving cell,
n – indicates the candidate cell.
25

27. LTE MEASUREMENT
CRITERIA Cell Re-Selection
Neighbor Cell Measurement
26

28. LTE MEASUREMENT
CRITERIA Cell Re-Selection
Neighbor Cell Measurement
FOR INTER-FREQUENCY AND INTER-RAT NEIGHBOUR CELLS:
If UE camps longer than 1 sec in the serving cell and:
- a higher priority neighbor fulfills (during TreselectionRAT):
SnonServingCell,x > Threshhigh 􀃆 reselect neighbor cell.
- no cell fulfills SnonServingCell,x > Threshhigh :
SServingCell < Threshserving,low and SnonServingCell,x > Threshx,low 􀃆
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reselect neighbor cell.

29. LTE MEASUREMENT
CRITERIA Cell Re-Selection
Neighbor Cell Measurement
Cell Reselection from WCDMA to LTE
UE must measure the LTE frequencies and detect the available LTE cell in order to perform cell reselection to
LTE.
• UE measures two physical properties called for WCDMA signal. One is CPICH RSCP and CPICH EcNo. RSCP
determines Srxlev and EcNo determines Squal.
• Srxlev = Qrxlevemeas - qRxLevMin. Qrxlevemeas is RSCP level measured by UE and qRxLevMin is the value
specified in SIB.
• Squal = Qqualmeas - qQualMin. Qqualmeas is EcNo level measured by UE and qQualMin is the value specified
in SIB.
• The detection measurement of LTE frequencies should be done at least once every 60s for higher priority LTE
frequencies.
• In following condition, detection measurements of lower priority LTE frequency is not required.
Srxlev > absPrioCellRes.sPrioritySearch1
Squal > absPrioCellRes.sPrioritySearch2
• In following condition, UE should detect once every 30s for both lower and higher priority LTE frequencies
Srxlev <= absPrioCellRes.sPrioritySearch1
Squal <= absPrioCellRes.sPrioritySearch2
• The maximum number of LTE FDD Frequencies are 4. In this case, UE should have performed measurement
for detecting LTE cells on all 4 LTE frequencies once every 240 (4 x 60) s or 120(4 x 30) s depending if UE
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measures above or below parameter threshold absPrioCellRes.sPrioritySearch1

30. LTE MEASUREMENT
CRITERIA Cell Re-Selection
Neighbor Cell Measurement
Cell Reselection from LTE to WCDMA
• Measurement Criteria (From High Priority LTE Cell to Lower Priority WCDMA Cell): When LTE cell has higher
priority than WCDMA, it would stay in LTE cell but it performs measurement for the low priority WCDMA if UE is
under the following condition :
Srxlev of the serving cell < sNonIntraSearch (SIB3),
where Srxlev = Qrxlevmeas - qRxLevMin (SIB3),
where Qrxlevemeas = measured RSRP level, qRxLevMin = minimum RSRP level for camping
• Measurement Criteria (From High Priority LTE Cell to Lower Priority WCDMA Cell): When LTE cell has
lower priority than WCDMA (WCDMA cell priority defined in SIB6 is higher than the serving cell priority),The UE
always have to perform measurements on WCDMA cell. How often UE has to measure for WCDMA depends on
whether Srxlev of the serving cell is greater or lower than sNonIntraSearch(SIB3). If no parameter is set
(meaning in default condition), detection of WCDMA cell should be performed at least every 60 seconds.
• Reselection Criteria (From High Priority LTE Cell to Lower Priority WCDMA Cell): If UE in LTE cell is under the
following condition with the duration longer than tReselectionUtra (SIB6), it should reselect to WCDMA cell.
Srxlev of LTE cell (serving cell) < threshServingLow (SIB3),
where Srxlev = Qrxlevmeas - qRxLevMin (SIB3),
where Qrxlevemeas = measured RSRP level, qRxLevMin = minimum RSRP level for camping
Srxlev of WCDMA cell > threshXLow (SIB6),
where Srxlev = Qrxlevmeas - qRxLevMin (SIB3),
where Qrxlevemeas = measured RSCP level, qRxLevMin = minimum RSCP level for camping
Note : If more than one WCDMA meet this condition, UE should select to the cell with highest Srxlev
Note : If these values are not specified in SIB and UE has to apply default values, UE has to perform reselection
when LTE RSRP is lower than -145 dBm and WCDMA cell is better than -119 dBm for at least 2 seconds.
29

31. LTE MEASUREMENT
CRITERIA Cell Re-Selection
Neighbor Cell Measurement
Cell Reselection from LTE to WCDMA
• Reselection Criteria (From Lower Priority LTE Cell to Higher Priority WCDMA Cell): If UE in LTE cell is under the
following condition with the duration longer than tReselectionUtra (SIB6), it should reselect to WCDMA cell.
Srxlev of WCDMA cell > threshXHigh (SIB6),
where Srxlev = Qrxlevmeas - qRxLevMin (SIB3),
where Qrxlevemeas = measured RSCP level, qRxLevMin = minimum RSCP level for camping
30

32. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW
31

33. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA E-UTRAN
Intra E-UTRAN Handover is used to hand over a UE from a source eNodeB to a target eNodeB using X2 when the MME is unchanged.
The intra E-UTRAN HO in RRC_CONNECTED state is UE assisted NW controlled HO, with HO preparation signalling in E-UTRAN.
To prepare the HO, the source eNB passes all necessary information to the target eNB (e.g. E-RAB attributes and RRC context) and UE
accesses the target cell via RACH following a contention-free procedure using a dedicated RACH preamble.
The HO procedure is performed without EPC involvement, i.e. preparation messages are directly exchanged between the eNBs.
32

34. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA E-UTRAN
Detailed explanation of above scenario is below.
• The source eNB configures the UE measurement procedures according to the area restriction information. UE
sends MEASUREMENT REPORT by the rules set by i.e. system information, specification etc.
• Source eNB makes decision based on MEASUREMENT REPORT and RRM information to hand off UE and issues a
HANDOVER REQUEST message to the target eNB passing necessary information to prepare the HO at the target
side.
• Admission Control may be performed by the target eNB dependent on the received E-RAB QoS information to
increase the likelihood of a successful HO. The target eNB configures the required resources according to the
received E-RAB QoS information.
• Target eNB prepares HO with L1/L2 and sends the HANDOVER REQUEST ACKNOWLEDGE to the source eNB. The
HANDOVER REQUEST ACKNOWLEDGE message includes a transparent container to be sent to the UE as an RRC
message to perform the handover.
• The UE receives the RRCConnectionReconfiguration message with necessary parameters (i.e. new C-RNTI, target
eNB security algorithm identifiers, and optionally dedicated RACH preamble, target eNB SIBs, etc.) and is
commanded by the source eNB to perform the HO.
• The source eNB sends the SN STATUS TRANSFER message to the target eNB to convey the uplink PDCP SN
receiver status and the downlink PDCP SN transmitter status of E-RABs for which PDCP status preservation applies
(i.e. for RLC AM).
• After receiving the RRCConnectionReconfiguration message including the mobilityControlInformation , UE
performs synchronisation to target eNB and accesses the target cell via RACH.
33

35. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA E-UTRAN
• The target eNB responds with UL allocation and timing advance.
• UE sends the RRCConnectionReconfigurationComplete message (C-RNTI) to confirm the handover to the target
eNB to indicate that the handover procedure is completed for the UE. The target eNB verifies the C-RNTI sent in
the RRCConnectionReconfigurationComplete message. The target eNB can now begin sending data to the UE.
• The target eNB sends a PATH SWITCH message to MME to inform that the UE has changed cell.
• The MME sends an UPDATE USER PLANE REQUEST message to the Serving Gateway.
• The Serving Gateway switches the downlink data path to the target side. The Serving gateway sends one or
more "end marker" packets on the old path to the source eNB and then can release any U-plane/TNL resources
towards the source eNB.
• Serving Gateway sends an UPDATE USER PLANE RESPONSE message to MME.
• The MME confirms the PATH SWITCH message with the PATH SWITCH ACKNOWLEDGE message.
• By sending UE CONTEXT RELEASE, the target eNB informs success of HO to source eNB and triggers the release
of resources by the source eNB. The target eNB sends this message after the PATH SWITCH ACKNOWLEDGE
message is received from the MME.
• Upon reception of the UE CONTEXT RELEASE message, the source eNB can release radio and C-plane related
resources associated to the UE context. Any ongoing data forwarding may continue.
Source : 3GPP TS 36.300
34

36. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA E-UTRAN (X2)
35

37. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA E-UTRAN (X2)
36

38. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA E-UTRAN (X2)
37

39. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA E-UTRAN (X2)
ANR HO
LTE UE can detect intra LTE neighbours without neighbour lists which simplifies network
management.
The UE reports other cell IDs to the eNodeB. If the target cell ID is known by eNodeB, it will
proceed with the handover.
If the target is not known by eNodeB and no is X2 enabled, the eNodeB asks UE to decode global
cell id of the target cell.
The eNodeB finds out the target cell’s IP address from O&M, enables an X2 connection to the
target cell and proceeds with the handover
38

40. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW (S1)
PREPARATION PHASE

41. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW (S1)
EXECUTION PHASE

42. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW (S1)
COMPLETION PHASE

43. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW (S1)
Step 1. The source eNodeB decides to initiate an S1-based handover to the target eNodeB. This can be triggered e.g. by no X2
connectivity to the target eNodeB, or by an error indication from the target eNodeB after an unsuccessful X2-based handover, or by
dynamic information learnt by the source eNodeB.
Step 2. The source eNodeB sends Handover Required (Direct Forwarding Path Availability, Source to Target transparent container,
target eNodeB Identity, CSG ID, CSG access mode, target TAI, S1AP Cause) to the source MME. The source eNodeB indicates which
bearers are subject to data forwarding. Direct Forwarding Path Availability indicates whether direct forwarding is available from the
source eNodeB to the target eNodeB. This indication from source eNodeB can be based on e.g. the presence of X2. The target TAI is
sent to MME to facilitate the selection of a suitable target MME. When the target cell is a CSG cell or a hybrid cell, the source eNodeB
shall include the CSG ID of the target cell. If the target cell is a hybrid cell, the CSG access mode shall be indicated.
Step 3. The source MME selects the target MME and if it has determined to relocate the MME, it sends a Forward Relocation Request
(MME UE context, Source to Target transparent container, RAN Cause, target eNodeB Identity, CSG ID, CSG Membership Indication,
target TAI, MS Info Change Reporting Action (if available), CSG Information Reporting Action (if available), UE Time Zone, Direct
Forwarding Flag) message to the target MME. The target TAI is sent to the target MME to help it to determine whether S GW relocation
is needed (and, if needed, aid SGW selection).
The source MME shall perform access control by checking the UE's CSG subscription when CSG ID is provided by the source eNodeB. If
there is no subscription data for this CSG ID or the CSG subscription is expired, and the target cell is a CSG cell, the source MME shall
reject the handover with an appropriate cause.
The MME UE context includes IMSI, ME Identity, UE security context, UE Network Capability, AMBR, Selected CN operator ID, APN
restriction, Serving GW address and TEID for control signalling, and EPS Bearer context(s).
An EPS Bearer context includes the PDN GW addresses and TEIDs (for GTP-based S5/S8) or GRE keys (for PMIP-based S5/S8) at the
PDN GW(s) for uplink traffic, APN, Serving GW addresses and TEIDs for uplink traffic, and TI.
RAN Cause indicates the S1AP Cause as received from source eNodeB.
The source MME includes the CSG ID in the Forward Relocation Request when the target cell is a CSG or hybrid cell. When the target
cell is a hybrid cell, the CSG Membership Indication indicating whether the UE is a CSG member shall be included in the Forward
Relocation Request message.
The Direct Forwarding Flag indicates if direct forwarding is applied, or if indirect forwarding is going to be set up by the source side.
The target MME shall determine the Maximum APN restriction based on the APN Restriction of each bearer context in the Forward
Relocation Request, and shall subsequently store the new Maximum APN restriction value.
If the UE receives only emergency services and the UE is UICCless, IMSI can not be included in the MME UE context in Forward
Relocation Request message. For emergency attached UEs, if the IMSI cannot be authenticated, then the IMSI shall be marked as
unauthenticated. Also, in this case, security parameters are included only if available.

44. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW (S1)
Step 4. If the MME has been relocated, the target MME verifies whether the source Serving GW can continue to serve the UE. If not, it
selects a new Serving GW. If the MME has not been relocated, the source MME decides on this Serving GW re-selection.
If the source Serving GW continues to serve the UE, no message is sent in this step. In this case, the target Serving GW is identical to
the source Serving GW.
If a new Serving GW is selected, the target MME sends a Create Session Request (bearer context(s) with PDN GW addresses and TEIDs
(for GTP-based S5/S8) or GRE keys (for PMIP-based S5/S8) at the PDN GW(s) for uplink traffic, Serving Network, UE Time Zone)
message per PDN connection to the target Serving GW. The target Serving GW allocates the S GW addresses and TEIDs for the uplink
traffic on S1_U reference point (one TEID per bearer). The target Serving GW sends a Create Session Response (Serving GW addresses
and uplink TEID(s) for user plane) message back to the target MME.
Step 5. The Target MME sends Handover Request (EPS Bearers to Setup, AMBR, S1AP Cause, Source to Target transparent container,
CSG ID, CSG Membership Indication, Handover Restriction List) message to the target eNodeB. This message creates the UE context in
the target eNodeB, including information about the bearers, and the security context. For each EPS Bearer, the Bearers to Setup
includes Serving GW address and uplink TEID for user plane, and EPS Bearer QoS. If the direct forwarding flag indicates unavailability of
direct forwarding and the target MME knows that there is no indirect data forwarding connectivity between source and target, the
Bearers to Setup shall include "Data forwarding not possible" indication for each EPS bearer. Handover Restriction List is sent if available
in the Target MME.
S1AP Cause indicates the RAN Cause as received from source MME.
The Target MME shall include the CSG ID and CSG Membership Indication when provided by the source MME in the Forward Relocation
Request message.
The target eNodeB sends a Handover Request Acknowledge (EPS Bearer Setup list, EPS Bearers failed to setup list Target to Source
transparent container) message to the target MME. The EPS Bearer Setup list includes a list of addresses and TEIDs allocated at the
target eNodeB for downlink traffic on S1 U reference point (one TEID per bearer) and addresses and TEIDs for receiving forwarded data
if necessary. If the UE AMBR is changed, e.g. all the EPS bearers which are associated to the same APN are rejected in the target
eNodeB, the MME shall recalculate the new UE-AMBR and signal the modified UE AMBR value to the target eNodeB.
If none of the default EPS bearers have been accepted by the target eNodeB, the target MME shall reject the handover.
If the target cell is a CSG cell, the target eNodeB shall verify the CSG ID provided by the target MME, and reject the handover with an
appropriate cause if it does not match the CSG ID for the target cell. If the target eNodeB is in hybrid mode, it may use the CSG
Membership Indication to perform differentiated treatment for CSG and non-CSG members.
Step 6. If indirect forwarding applies and the Serving GW is relocated, the target MME sets up forwarding parameters by sending Create
Indirect Data Forwarding Tunnel Request (target eNodeB addresses and TEIDs for forwarding) to the Serving GW. The Serving GW
sends a Create Indirect Data Forwarding Tunnel Response (target Serving GW addresses and TEIDs for forwarding) to the target MME. If
the Serving GW is not relocated, indirect forwarding may be set up in step 8 below.
Indirect forwarding may be performed via a Serving GW which is different from the Serving GW used as the anchor point for the UE.

45. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW (S1)
Step 7. If the MME has been relocated, the target MME sends a Forward Relocation Response (Cause, Target to Source transparent
container, Serving GW change indication, EPS Bearer Setup List, Addresses and TEIDs) message to the source MME. For indirect
forwarding, this message includes Serving GW Address and TEIDs for indirect forwarding (source or target). Serving GW change
indication indicates a new Serving GW has been selected.
Step 8. If indirect forwarding applies, the source MME sends Create Indirect Data Forwarding Tunnel Request (addresses and TEIDs for
forwarding) to the Serving GW. If the Serving GW is relocated it includes the tunnel identifier to the target serving GW.
The Serving GW responds with a Create Indirect Data Forwarding Tunnel Response (Serving GW addresses and TEIDs for forwarding)
message to the source MME.
Indirect forwarding may be performed via a Serving GW which is different from the Serving GW used as the anchor point for the UE.
Step 9. The source MME sends a Handover Command (Target to Source transparent container, Bearers subject to forwarding, Bearers
to Release) message to the source eNodeB. The Bearers subject to forwarding includes list of addresses and TEIDs allocated for
forwarding. The Bearers to Release includes the list of bearers to be released.
Step 9a. The Handover Command is constructed using the Target to Source transparent container and is sent to the UE. Upon reception
of this message the UE will remove any EPS bearers for which it did not receive the corresponding EPS radio bearers in the target cell.
Step 10. The source eNodeB sends the eNodeB Status Transfer message to the target eNodeB via the MME(s) to convey the PDCP and
HFN status of the E-RABs for which PDCP status preservation applies. The source eNodeB may omit sending this message if none of the
E-RABs of the UE shall be treated with PDCP status preservation.
If there is an MME relocation the source MME sends this information to the target MME via the Forward Access Context Notification
message which the target MME acknowledges. The source MME or, if the MME is relocated, the target MME, sends the information to the
target eNodeB via the eNodeB Status Transfer message.
Step 11. The source eNodeB should start forwarding of downlink data from the source eNodeB towards the target eNodeB for bearers
subject to data forwarding. This may be either direct (step 11a) or indirect forwarding (step 11b).
Step 12. After the UE has successfully synchronized to the target cell, it sends a Handover Confirm message to the target eNodeB.
Downlink packets forwarded from the source eNodeB can be sent to the UE. Also, uplink packets can be sent from the UE, which are
forwarded to the target Serving GW and on to the PDN GW.
Step 13. The target eNodeB sends a Handover Notify (TAI+ECGI) message to the target MME.

46. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW (S1)
Step 14. If the MME has been relocated, the target MME sends a Forward Relocation Complete Notification () message to the source
MME. The source MME in response sends a Forward Relocation Complete Acknowledge () message to the target MME. Regardless if MME
has been relocated or not, a timer in source MME is started to supervise when resources in Source eNodeB and if the Serving GW is
relocated, also resources in Source Serving GW shall be released.
Upon receipt of the Forward Relocation Complete Acknowledge message the target MME starts a timer if the target MME allocated S GW
resources for indirect forwarding.
Step 15. The MME sends a Modify Bearer Request (eNodeB address and TEID allocated at the target eNodeB for downlink traffic on S1
U for the accepted EPS bearers, ISR Activated) message to the target Serving GW for each PDN connection, including the PDN
connections that need to be released. If the PDN GW requested UE's location and/or User CSG information (determined from the UE
context), the MME also includes the User Location Information IE and/or User CSG Information IE in this message. If the UE Time Zone
has changed, the MME includes the UE Time Zone IE in this message. For the case that neither MME nor S-GW changed, if ISR was
activated before this procedure MME should maintain ISR. The UE is informed about the ISR status in the Tracking Area Update
procedure.
The MME releases the non-accepted dedicated bearers by triggering the bearer release procedure. If the Serving GW receives a DL
packet for a non-accepted bearer, the Serving GW drops the DL packet and does not send a Downlink Data Notification to the MME.
If the default bearer of a PDN connection has not been accepted by the target eNodeB and there are other PDN connections active, the
MME shall handle it in the same way as if all bearers of a PDN connection have not been accepted. The MME releases these PDN
connections by triggering the MME requested PDN disconnection procedure.
When the Modify Bearer Request does not indicate ISR Activated the Serving GW deletes any ISR resources by sending a Delete Bearer
Request to the other CN node that has bearer resources on the Serving GW reserved.
Step 16. If the Serving GW is relocated, the target Serving GW assigns addresses and TEIDs (one per bearer) for downlink traffic from
the PDN GW. It sends a Modify Bearer Request (Serving GW addresses for user plane and TEID(s), Serving Network) message per PDN
connection to the PDN GW(s). The S GW also includes User Location Information IE and/or UE Time Zone IE and/or User CSG
Information IE if they are present in step 15. The Serving GW allocates DL TEIDs on S5/S8 even for non-accepted bearers. The PDN
GW updates its context field and returns a Modify Bearer Response (Charging Id, MSISDN) message to the target Serving GW. The
MSISDN is included if the PDN GW has it stored in its UE context. The PDN GW starts sending downlink packets to the target GW using
the newly received address and TEIDs. These downlink packets will use the new downlink path via the target Serving GW to the target
eNodeB.

47. LTE MEASUREMENT
HANDOVER
HANDOVER INTRA MME/SGW (S1)
If the Serving GW is not relocated, but has received the User Location Information IE and/or UE Time Zone IE and/or User CSG
Information IE from the MME in step 15, the Serving GW shall inform the PDN GW(s) about these information that e.g. can be used for
charging, by sending the message Modify Bearer Request (User Location Information IE, UE Time Zone IE, User CSG Information IE) to
the PDN GW(s) concerned. A Modify Bearer Response message is sent back to the Serving GW.
If the Serving GW is not relocated and it has not received User Location Information IE nor UE Time Zone IE nor User CSG Information
IE from the MME in step 15, no message is sent in this step and downlink packets from the Serving GW are immediately sent on to the
target eNodeB.
Step 17. The target Serving GW sends a Modify Bearer Response message to the target MME. The message is a response to a message
sent at step 15.
If the Serving GW does not change, the Serving GW shall send one or more "end marker" packets on the old path immediately after
switching the path in order to assist the reordering function in the target eNodeB.
Step 18. The UE initiates a Tracking Area Update procedure when one of the conditions listed in clause "Triggers for tracking area
update" applies.
The target MME knows that it is a Handover procedure that has been performed for this UE as it received the bearer context(s) by
handover messages and therefore the target MME performs only a subset of the TA update procedure, specifically it excludes the
context transfer procedures between source MME and target MME.
Step 19. When the timer started in step 14 expires the source MME sends a UE Context Release Command () message to the source
eNodeB. The source eNodeB releases its resources related to the UE and responds with a UE Context Release Complete () message.
When the timer started in step 14 expires and if the source MME received the Serving GW change indication in the Forward Relocation
Response message, it deletes the EPS bearer resources by sending Delete Session Request (Cause, LBI) messages to the Source
Serving GW. Cause indicates to the Source Serving GW that the Serving GW changes and the Source Serving GW shall not initiate a
delete procedure towards the PDN GW. The Source Serving GW acknowledges with Delete Session Response () messages. If ISR has
been activated before this procedure, the cause also indicates to the Source S GW that the Source S GW shall delete the bearer
resources on the other old CN node by sending Delete Bearer Request message(s) to that CN node.
Step 20. If indirect forwarding was used then the expiry of the timer at source MME started at step 14triggers the source MME to send
a Delete Indirect Data Forwarding Tunnel Request message to the S GW to release the temporary resources used for indirect forwarding
that were allocated at step 8.
Step 21. If indirect forwarding was used and the Serving GW is relocated, then the expiry of the timer at target MME started at step
14 triggers the target MME to send a Delete Indirect Data Forwarding Tunnel Request message to the target S GW to release temporary
resources used for indirect forwarding that were allocated at step 6.

48. LTE MEASUREMENT
HANDOVER
HANDOVER IRAT TO 2G/3G
47

49. LTE MEASUREMENT
HANDOVER
HANDOVER IRAT TO CDMA2000 1XRTT and HRPD (High Rate Packet Data)
48

50. LTE MEASUREMENT
HANDOVER
HANDOVER EVENTS
If we can see the algorithm, it looks like 3G HO event concept:
“hysteresis” – “time to trigger” – “cell individual offset”
Event Type
Event A1
Event A2
Event A3
Event A4
Event A5
Event B1
Event B2
Description
Serving becomes better than threshold
Serving becomes worse than threshold
Neighbour becomes offset better than serving
Neighbour becomes better than threshold
Serving becomes worse than threshold1 and neighbour becomes better than threshold2
Inter RAT neighbour becomes better than threshold
Serving becomes worse than threshold1 and inter RAT neighbour becomes better than threshold2
49

51. LTE MEASUREMENT
HANDOVER
HANDOVER EVENTS A1
50

52. LTE MEASUREMENT
HANDOVER
HANDOVER EVENTS A2
51

53. LTE MEASUREMENT
HANDOVER
HANDOVER EVENTS A3
52

54. LTE MEASUREMENT
HANDOVER
HANDOVER EVENTS A4
53

55. LTE MEASUREMENT
HANDOVER
HANDOVER EVENTS A5
54

56. LTE MEASUREMENT
HANDOVER
HANDOVER EVENTS B1
55

57. LTE MEASUREMENT
HANDOVER
HANDOVER EVENTS B2
56

58. LTE MEASUREMENT
HANDOVER
Speed dependent scaling of measurement parameters
57

59. LTE MEASUREMENT
HANDOVER
58

60. END
Please contact me if there is something wrong in the slide