LTE Field Training Document_Internal-1

LTE Fi ld MLTE Field Measurement

Prepared By :Surendra Singh Bundela Checked By: Sourabh Bhatham

Physical layer measurements have not been extensively discussed in the LTE standardization.

Overview of LTE Measurements

They could change. Intra LTE measurements ( from LTE to LTE)UE measurements

Reference Signal Received Power (RSRP)Reference Signal Received Power (RSRP)Received signal strength Indicator(RSSI)Reference Signal Received Quality ( RSRQ)Signal to interference noise ratio (SINR)CQI tCQI measurements Physical cell Identification(PCI)Tracking area code(TAC)

eNB measurementsNon standardized (vendor specific): TA, Average RSSI, Average SINR, UL CSI, detected PRACH preambles, transport channel BLERStandardized: DL RS Tx Power, Received Interference Power, Thermal Noise Power

Measurements from LTE to other systemsMeasurements from LTE to other systemsUE measurements are mainly intended for handover.

UTRA FDD: CPICH RSCP, CPICH Ec/No and carrier RSSIGSM: GSM carrier RSSIUTRA TDD i RSSI RSCP P CCPCHUTRA TDD: carrier RSSI, RSCP, P‐CCPCHCDMA2000: 1xRTT Pilot Strength, HRPD Pilot Strength

Reference Signals Received Power (RSRP)RSRP i th i d f i l RS l t– RSRP is the average received power of a single RS resource element.

– UE measures the power of multiple resource elements used to transfer the reference signal but then takes an average of them rather than summing them.

Reporting range 44 140 dBm– Reporting range ‐44…‐140 dBm

Definition Reference signal received power (RSRP), is defined as the linear average over the power contributions (in [W]) of the resource elements that carry cell-specific reference signals within the considered measurement frequency bandwidth. For RSRP determination the cell-specific reference signals R0 according TS 36 211 [3] shall beFor RSRP determination the cell-specific reference signals R0 according TS 36.211 [3] shall be used. If the UE can reliably detect that R1 is available it may use R1 in addition to R0 to determine RSRP. The reference point for the RSRP shall be the antenna connector of the UE. If receiver diversity is in use by the UE, the reported value shall not be lower than the corresponding RSRP of any of the individual diversity branches.

Applicable for RRC_IDLE intra-frequency, RRC_IDLE inter-frequency, RRC_CONNECTED intra-frequency, RRC CONNECTED inter frequencyRRC_CONNECTED inter-frequency

Note1: The number of resource elements within the considered measurement frequency bandwidth and within the measurement period that are used by the UE to determine RSRP is left up to the UE implementation with the limitation that corresponding measurement accuracy requirements have to be fulfilled.

Note 2: The power per resource element is determined from the energy received during the useful part of the symbolNote 2: The power per resource element is determined from the energy received during the useful part of the symbol, excluding the CP.

RSRP mapping 3GPP TS 36.133 V8.9.0 (2010‐03)

– The reporting range of RSRP is defined from ‐140 dBm to ‐44 dBm with 1 dB resolution.

– The mapping of measured quantity is defined in the table below.

R t d l M d tit l U itReported value Measured quantity value UnitRSRP_00 RSRP < -140 dBmRSRP_01 -140 ≤ RSRP < -139 dBmRSRP_02 -139 ≤ RSRP < -138 dBm

… … …RSRP_95 -46 ≤ RSRP < -45 dBmRSRP_96 -45 ≤ RSRP < -44 dBmRSRP_97 -44 ≤ RSRP dBm

RSSI

– RSSI not reported to eNodeB by UE

• Can be computed from RSRQ and RSRP that are reported by UE

– RSSI measures all power within the measurement bandwidth

• Measured over those OFDM symbols that contain RS

• Measurement bandwidth RRC‐signalled to UE

Presentation / Author / Date

RSSI and RSRP

• RSSI = wideband power= noise + serving cell power + interference power

– Without noise and interference, 100% DL PRB activity: RSSI=12*N*RSRP

• RSRP is the received power of 1 RE (3GPP definition) average of power levels received across all Reference Signal symbols within the considered measurement frequency bandwidth

• RSSI is measured over the entire bandwidth

• N: number of RBs across the RSSI is measured and depends on the BW

– Based on the above, under full load and high SNR:

RSRP (dBm)= RSSI (dBm) ‐10*log (12*N)


RSRQ

– RSRQ = N x RSRP / RSSI• N is the number of resource blocks over which the RSSI is measured, typically equal to system bandwidth

• RSSI is pure wide band power measurement, including intracell power,RSSI is pure wide band power measurement, including intracell power, interference and noise

– RSRQ reporting range ‐3…‐19.5dB

Definition Reference Signal Received Quality (RSRQ) is defined as the ratio N×RSRP/(E-UTRA carrier RSSI), where N is the number of RB’s of the E-UTRA carrier RSSI measurement bandwidth. The measurements in the numerator and denominator shall be made over the same set of resource blocks. E-UTRA Carrier Received Signal Strength Indicator (RSSI), comprises the linear average of the total received power (in [W]) observed only in OFDM symbols containing reference symbols for antenna port 0, in the measurement bandwidth, over N number of resource blocks by the UE from all sources, including co-channel serving and non-serving cells, adjacent channel interference, thermal noise etc. The reference point for the RSRQ shall be the antenna connector of the UE. If receiver diversity is in use by the UE, the reported value shall not be lower than the corresponding RSRQ of any of the individual diversity branches.

Applicable for RRC_CONNECTED intra-frequency, RRC CONNECTED inter-frequency


_ q y

RSRQ reporting range

– RSRQ = N x RSRP / RSSI• N is the number of resource blocks over which the RSSI is measured, typically equal to system bandwidth

• RSSI is pure wide band power measurement, including intracell power,RSSI is pure wide band power measurement, including intracell power, interference and noise

– RSRQ reporting range ‐3…‐19.5dB

Reported value Measured quantity value UnitRSRQ_00 RSRQ < -19.5 dBRSRQ_01 -19.5 ≤ RSRQ < -19 dBRSRQ_02 -19 ≤ RSRQ < -18.5 dB

… … …RSRQ_32 -4 ≤ RSRQ < -3.5 dBRSRQ_33 -3.5 ≤ RSRQ < -3 dB


RSRQ_34 -3 ≤ RSRQ dB

SINR definition

• SINR is the reference value used in the system simulation

• SINR can be defined:

1. Wide band SINR

2. SINR for a specific subcarriers (or for a specific resource elements)

• SINR = S/(I+N), all measured over the same bandwidth

– Most drive test UEs and scanners support SINR or SNR measurement

– Example: LG supports RS SNR measurement

– Example: Samsung BT‐3710 measures CINR from RS (e‐mail info from Samsung)


SNR vs. RSRP

• RSRP to SNR mappingRSRP i d f i l b i– RSRP is measured for a single subcarrier• noisepower_for_15KHz= ‐125.2dBm

– Noise figure = 7 dB– Temperature = 290 K

• Assumption: RSRP doesn’t contain noise power• Assumption: RSRP doesn t contain noise power

PRSRPSNR

REn

=

RSRP vs. SNR

35.00

40.00

powernoiseKHzP REn __15_

_

=

10.00

15.00

20.00

25.00

30.00

SNR

(dB

)

SNR

-15 00

-10.00

-5.00

0.00

5.00

-135 -130 -125 -120 -115 -110 -105 -100 -95 -90 -85 -80 -75 -70

S

This curve gives upper limit to SINR with certain RSRP. SINR is always lower than SNR in live


15.00

RSRP (dBm)network due to interference.

RSRQ to SINR mapping

– RSRQ depends on own cell traffic load, but SINR doesn’t depend on own cell load.• Used Resource Elements per Resource Block (RE/RB) in serving cell is an input• Used Resource Elements per Resource Block (RE/RB) in serving cell is an input

parameter for RSRQ ‐> SINR mapping• Assumption: RSRP doesn’t contain noise power

xNPP

PPNRSRPSINR

REnxNn

Nni

12*

__

12_

∗=

+=

RSSIRSRPNRSRQ

PxNRSRPPRSSIRBsN

usedRBREx

Nni

*

*#

_/

12_

=

++===

RSSI

xRSRQ

xNRSRPRSRQ

RSRPNNRSRPSINR

−=

−= 1

12

**12*


RSRQ to SINR mappingRSRQ vs SINR

Difficult to estimate SINR in this

– Equation used:

SINR = 112 15.00

20.00

25.00

30.00

2 RE/RB

4 RE/RB

Difficult to estimate SINR in this region from RSRQ, SINR very sensitive to RSRQ and cell load

• x=RE/RB

xRSRQ

−1

5 00

0.00

5.00

10.00

-20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3

SIN

R (d

B) 4 RE/RB

6 RE/RB

8 RE/RB

10 RE/RB

12 RE/RB

– 2RE/RB equals to empty cell. Only Reference Signal power is considered from serving cell.

RSRP vs. SNR

-10.00

-5.00

RSRQ (dB)

– 12RE/RB equals to fully loaded serving cell. All resource elements are carrying data.

– In practice, mapping from 15 00

20.00

25.00

30.00

35.00

40.00

B)p , pp g

RSRQ to SINR seems difficult• Currently available

measurement UEs and scanners report SINR directly

-10.00

-5.00

0.00

5.00

10.00

15.00

-135 -130 -125 -120 -115 -110 -105 -100 -95 -90 -85 -80 -75 -70

SNR

(dB

SNR


-15.00

10.00

RSRP (dBm)

CQI Measurements4‐bit CQI Table

5

6

70

80

90

100

2

3

4

effic

ienc

y

20

30

40

50

60

code

rate

/ %

0

1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

CQI index

0

10

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

CQI index

Physical cell Identification(PCI)

Planning of the PCI is somewhat similar to planning of the PrSC in WCDMA or even BCCH ARFCN in GSM. The PCI is a physical cell identifier it assumes values from 0 to 503.It is comprised of two identifiers which are linked to corresponding signals on the physical layer. There are three Primary Synchronization Signals (PSS) and 168 Secondary SynchronizationThere are three Primary Synchronization Signals (PSS) and 168 Secondary SynchronizationSignal (SSS). The PSS are numbered 0,1 and 2, while SSS are numbered from 0‐167. The PCI value is linked to corresponding PSS and SSS as

PCI = PSS + 3*SSS

Table 1, provides mapping between PCIs, SSSs and PSSs.

There is no standard way for planning of PCIs but there are some guidelines.

Co‐PCI assignment for close sites needs to be avoidedSectors on the same eNode B should have the same SSS code but different PSS (assuming three sectored sites).

This is not mandatory but helps synchronization of UEs and improves traceability of the PCI assignment.Co‐PCI assignment for the neighbors needs to be avoided. If the neighbors are Co‐PCI, the handover process

may fail Also this is the trickiest requirement (We will be adding an analysis in the LTE toolbox that evaluatesmay fail. Also, this is the trickiest requirement. (We will be adding an analysis in the LTE toolbox that evaluates the PCI assignment and detects this condition)It is common to allocate a separate set of PCIs for outdoor cells and indoor cells. The reason is again

management of the PCIs and the fact that indoor cells are rarely tri‐sectored. They are usually deployed invariety of antenna configurations.

Table 1. Mapping between synchronization signals and PCI

An example of a PCI strategy may be as follows.

Divide PCIs in to groups 0‐449 and 450‐503. The first group provides 450 (150 times 3)g p g p p ( )PCIs for outdoor cells and second group 54 (18 times 3) PCIs for indoor planning and additionof new sites. The first group provides 150 different SSS. Plan, outdoor sites by assigning one SSS to

th it O th SSS i i d t th it PSS 0 i i d t th l h PSS 1 i i dthe site. Once the SSS is assigned to the site, PSS 0 is assigned to the alpha, PSS 1 is assignedto beta and PSS 2 is assigned to gamma sector of the site. Make sure that co‐PCI assignments are spread as far as possible. Plan indoor sites by assigning one of the PCIs from the second group.

Again, make sure that the co‐PCI assignments are separated as far as possible.

Tracking Area Code(TAC)

Tracking Area (TA)It is the successor of location and routing areas from 2G/3G.When a UE is attached to the network the MME will know the UE’s position onWhen a UE is attached to the network, the MME will know the UE s position on tracking area level. In case the UE has to be paged, this will be done in the full tracking area. Tracking areas are identified by a Tracking Area Identity (TAI).

Tracking AreasTracking Area

HSS

MME

TAI2

TAI1

TAI1TAI1

TAI1

TAI1 eNB 1 2

eNB

TAI2

TAI2TAI2

TAI2

TAI2

TAI2

TAI2

TAI2

S‐eNBTAI3

TAI3TAI3

TAI3

TAI3TAI3

TAI2

MME

3

TAI3TAI3

Cell Identity

Tracking Areas OverlappingCurrently under discussion in 3GPP

2.‐ UE is told by the network to be in several tracking areas simultaneously

1.‐ Tracking areas are allowed to overlap: one cell can belong to

multiple tracking areas

simultaneously.

Gain: when the UE enters a new cell, it checks which tracking areas the new cell is part of. If this TA is on UE’ TA li t th t ki

HSS

UE’s TA list, then no tracking area update is necessary.

MMETAI1‐2

TAI1

TAI1

TAI1 eNB 1 2

TAI1‐2

eNB

TAI2TAI2

TAI2

TAI2

TAI2

TAI2

TAI1

Cell Identity

S‐eNBTAI3

TAI3TAI3

TAI3TAI3

TAI2TAI2

MME

3

Cell Identity

TAI3TAI3

TAI3

Tracking Areas: Use of S1‐flex Interface

HSS

TAI1‐2MMETAI1

TAI1eNB

MME 1 2 3

MME

eNB

TAI2

TAI2

TAI2TAI2

TAI2

TAI1

TAI1TAI1‐2 Pooling:

several MME

handle the

S‐eNBTAI2

TAI2TAI2

TAI3TAI3

TAI2TAI2

TAI2

S‐MME

same tracking area321

TAI3TAI3

TAI3

Cell Identity

Timing Advance g

• Why timing advance??

• Because the UL resources are orthogonal and this fact has to be maintained

• Different UEs in the cell may have different position and therefore different propagation delay ‐> this may affect synchronisation

O l UL i i d DL• Only UL timing advance no DL

• In DL possible to manage synchronised transmission to several UEs

Timing Advance – Principle

UE 2

UE 1a) UE Tx timing

UE 2

UE 1

D = 16 Ts

UE 2

UE 1

b) eNB Rx timing

UE 2

UE 1

Timing Advance UE 2

Timing Advance UE 1 time

Timing Advance

• How often ‐> what is the frequency of Timing Advance?

– Granularity of 0,52us corresponding to 78 m

– Dependent on the UE speed:

– 1. E.g. 72 km/h = 20 m/s

– ‐> 78 m in approx 4 s

– ‐> an update every 4 seconds

– 2. E.g. 500 km/h = 130 m/s

– 78 m approx 2 times per second

– ‐> Maximum of 2 updates per second

• How is the Node‐B measuring the TA?

• Based on received PUSCH on TTI basis

• CQI reports on PUCCH

• How is the timing advance signalled to the UE??

• At MAC layer (peer to peer signalling)

Cell Selection and Reselection

Overall ProcessOverall Process

• 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.

•• In the selected PLMN a suitable cell is selected and if this new cell is not in a

i t d l ti i t ti i f d i N d B t th t kregistered area, location registration is performed via eNodeB to the core network.

•• The overall process is divided into three sub‐processes:

•• 1. PLMN selection and reselection to search for an available mobile network.

• 2. Cell selection and reselection to search for a suitable cell belonging to the selected PLMNselected PLMN.

• 3. Location registration to register the UE’s presence in a registration area

PLMN Selection Power on

PLMN Selectionand Reselection

Power on

PLMN

F1PLMNselected

PLMNavailable

Registrationresponse Cell selection

and Reselection

EPS

Reselection

Registration

Location registration

Registration

Service Types (1/2)

• The action of camping on provides access to services. The network provides different levelsThe action of camping on provides access to services. The network provides different levels of service to a UE in either Idle mode or Connected mode. Three levels of services are defined:

LIMITED SERVICE ll t bl ll• LIMITED SERVICE: emergency calls on an acceptable cell.

• 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.

• Suitable cell:

• UE may camp on to obtain normal service. Such a cell shall fulfill all the following requirements: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 a CSG cell it is part of the white list

Service Types (2/2)yp ( / )

• OPERATOR SERVICE: FOR OPERATORS ONLY ON A RESERVED CELL.

• Reserved cell:

• When the cell status "reserved for operator use" is indicated and the Access Class of the UE is 11 or 15 the UE may select/re‐select this cell if in Home PLMN.

• Set by O&M parameter.

•• 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.

PLMN AMCC=**, MNC=XX

PLMN B

PLMN CMCC=**, MNC=YY

PLMN BMCC=**, MNC=ZZ …

USIM card

IMSI=MCC+MNC+MSIN

IMSI format

MCC MNC MSINMCC3 digits

MNC2~3 digits

MSIN(Mobile Subscriber Identity Number)

Maximum 10 digits

Cell Selection and Reselection (1/2) • To get service from the selected PLMN, the UE performs two types of procedures: cellTo get service from the selected PLMN, the UE performs two types of procedures: cell

selection and cell 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 usersvia AS (Access Stratum). The NAS offers the E‐UMTS service to the users.

•• 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 knows the tracking area of the cell in which the registered UE is camped.

Cell Selection and Reselection (2/2)

• CELL RESELECTION

• 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 y ydifferent 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.

Cell 1Cell 4

Optional:

Cell 3

System information / measurement control:‐PLMN identity‐Cell information

Initial Selection‐ Carrier 1:

Cell 2

Carrier 1:strongest cell ‐ Carrier 2:strongest cell‐ Carrier i …..

Stored Information Selection f‐ Previous information

‐ Previous detections

PLMN Selection Process

• 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

d ( f ll hi ) d d it t i f ti i d t fi dprocedure (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 stength is• If the UE can read the PLMN identity, the PLMN and the measured signal stength is

reported to the NAS: if: signal >= ‐ x dBm (high quality PLMN); without the measured signal strength if < x dBm.

Cell Selection Process (1/2)

• 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 search1) 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

h i h f h ll d d i i f i O heach 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. p

•• 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.

Cell Selection Process (2/2) • If the UE is unable to find any suitable cell in the selected PLMN, the UE enters to "any cell

selection" stateselection 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.

• Perform necessary measurements for the cell reselection evaluation procedure.

E h ll l i l i d• Execute the cell reselection evaluation procedure.

•• If after cell reselection evaluation process a better cell is found, the cell reselection is

performed. If no suitable cell is found, the UE enters to next state “any cell selection”.p , y

•• 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 “camped on any cell” state If the UE can not find any acceptable cell it stays in thisenters to camped on any cell state. If the UE can not find any acceptable cell, it stays 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 state changes to Camped normally.

• The figures show the initial cell selection and process for idle mode cell selection and reselection.

New PLMN Selection

NoYes

S d Initial Cell Selection

Stored informationCell Selection

No suitable cell found

Stored information

Suitable cell found

Suitable cell found

Camped normally

found found

Suitable cell found

trigger

Cell Reselection evaluation

No USIM



Connectedmode

Any cell selection

No USIM

USIM inserted

Acceptable cell found

Camped on any cellSuitable cell found

Connectedd

Acceptable cell found

trigger

Cell Reselectionevaluation

No Acceptable cell found

mode(EC only)

Cell Selection Criterion: S

SuitableSuitable cellscells::

E‐UTRAN cells: Srxlev > 0UTRAN cells: Srxlev > 0 AND Squal > 0UTRAN cells: Srxlev > 0 AND Squal > 0GSM cells: Srxlev > 0

Srxlev = Qrxlevmeas – (Qrxlevmin – Qrxlevminoffset*) ‐ Pcompensation **Squal = Qqualmeas – Qqualmin

* Qrxlevminoffset: only when camping in VPLMN

** Pcompensation = max(UE TXPWR MAX RACH ‐ P MAX 0) Pcompensation max(UE_TXPWR_MAX_RACH P_MAX, 0)

Cell Reselection Process • 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.

•• In high/medium‐mobility states, a UE:

• multiplies Qhyst by "Speed dependent ScalingFactor for Qhyst for * mobility state" if sent.

l l l b " d d d l f l f *• multiplies TreselectionRAT by "Speed dependent ScalingFactor for TreselectionRAT for * mobility state for RAT cells. (RAT = EUTRAN, UTRAN, GERAN).

• * = high, medium.

Neighbor Cell Measurements

Measurement Measurement ofof neighborneighbor cellscells::

Intra ‐ Frequency: Srxlev <= Sintrasearch

Inter ‐ Frequency: Srxlev <= Snonintrasearch OR

Prio (inter – f) > Prio (serving)

Inter ‐ RAT: Srxlev <= Snonintrasearch OR

Prio (inter ‐ RAT) > Prio (serving)

For inter‐frequency and inter‐system measurements, depending th UE bilit th t k ll t ton 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 g g p , pscheduled for data transmission, but the vacant resources could still be used for other UEs, because of the shared channel mechanism.

Intra‐frequency/ Equal Priority Case: Cell Ranking C it i RCriterion: R

Ranking Ranking ofof cellscells::

Rs = Qmeas,s + QhystS

R Q Qoffset

Qmeas* RSRP measurement quantity used in cell reselections.

Qoffset For intra‐frequency:Equals to Qoffsets,n, if Qoffsets,n is Rn = Qmeas,n – Qoffsets,nq Q , , Q ,

valid, otherwise this equals to zero.For inter‐frequency:Equals to Qoffsets,n plus Qoffsetfrequency, if Qoffsets,n is valid, otherwise this equals toR R “ ll l ti “ otherwise this equals to Qoffsetfrequency.

s ‐> for serving cell n ‐> for neighbor cell

*3GPP TS 36.304

Rn > Rs =>“cell reselection“

Re‐selected cell: Suitable (S Criterion)Best Rank(Highest R)

o e g bo ce

Best Rank(Highest R)

Inter‐Frequency and Inter‐RAT Cell Reselection q y

• FOR INTER‐FREQUENCY AND INTER‐RAT NEIGHBOUR CELLS:

•• If UE camps longer than 1 sec in the serving cell and:

•• ‐ a higher priority neighbour fullfills (during TreselectionRAT):

• SnonServingCell,x > Threshhigh reselect neighbour cell.

•• ‐ no cell fullfills SnonServingCell,x > Threshhigh :

• SServingCell < Threshserving,low and SnonServingCell,x > Threshx,low reselect neighbour cell. g g, g , ,

•

Type of Handover & Handover Signalingyp g g

Handovers Event A3 used for Better Cell HO

RSRP

RSRP at serving cell + a3Offset < RSRP at neighbor cell

RSRP Neighbour CellA3 condition met

Serving Cell RSRP

a3offset

time

a3TimeToTrigger

MeasurementReport

eNB

a3Report Interval

MeasurementReport

reporting condition met


eNBreporting condition metafter Time To Trigger

Handovers Event A5

RSRP

RSRP at serving cell < threshold3AND (&&)

RSRP at target > threshold3a

threshold3aServing Cell RSRPg

threshold3

timeNeighbour Cell RSRP

shold3

a

shold3

a5TimeToTrigger

MeasurementReport

eNB

a5Report Interval

MeasurementReport

thres

thres


eNB

‐140 dBm

Inter eNB HandoverSimplified

UE eNB9 MMEeNB4

1.22.

3.44.

5.

66.7.

9.

8.

1010.11.

12.

Handover Preparation, step 1/3

UE Source Target MME GW1. The source eNB configures the UE

measurement procedures with an RRC RECONFIGURATION

1. RRC Reconfiguration2. UE is triggered to send

MEASUREMENT REPORT to the source eNB. It can be event triggered or periodic

RRC Reconfiguration Complete

2. Measurement report

3. HO decision

triggered or periodic

3. Source eNB makes handover decision based on UE report + load and service information

4. HO request

5. Admission control

4. The source eNB issues a HANDOVER REQUEST to the target eNB

5 T t NB f d i i6. HO request ack.

5. Target eNB performs admission control

6. Target eNB sends the HANDOVER REQUEST ACKNOWLEDGE to the


REQUEST ACKNOWLEDGE to the source eNB

Handover Execution, step 2/3

UE Source Target MME GW

7. Source eNB generates the RRC RECONFIGURATION towards UE informing it to move to the target cell

7. RRC Reconfiguration

Source eNB starts forwarding packets to target eNB

8. Source eNB sends status information to target eNB

9 UE f th fi l

8. Status transfer

Forward packets to target

9. UE performs the final synchronisation to target eNB and accesses the cell via RACH procedure

DL pre‐synchronisation is obtained


Buffer packets from source

9. Synchronization

DL pre synchronisation is obtained during cell identification and measurements

10. Target eNB gives the uplink allocation and timing advance information

10. UL allocation and timing advance

11. RRC Reconf. Complete

information11. UE sends RRC RECONFIGURATION

COMPLETE to target eNBTarget eNB can begin to send data to UE

Handover Completion, step 3/3

12 Target eNB sends a PATH SWITCH

UE Source Target MME GW

12.Target eNB sends a PATH SWITCHmessage to MME to inform that the UE has changed cell

13.MME sends a USER PLANE UPDATE

12. Path switch request

REQUESTmessage to Serving Gateway14.Serving Gateway switches the

downlink data path to the target side 15.Serving Gateway sends a USER PLANE 13. User plane update

request

14. Switch downlink path

15.Serving Gateway sends a USER PLANE UPDATE RESPONSEmessage to MME

16.MME confirms the PATH SWITCH message with the PATH SWITCH ACKmessage path

15. User plane update response

16 P h i h k

message17.By sending RELEASE RESOURCE the

target eNB informs success of handover to source eNB and triggers h l f 16. Path switch request ack.

17. Release resources

18. Release

the release of resources 18.Upon reception of the RELEASE

RESOURCEmessage, the source eNBcan release radio and C‐plane related


resourcesp

resources associated to the UE context

Intra‐eNB handover

UEeNB CellID 8706

MMEeNB CellID 8706

Signalling example, Attach Request

Step 1: RACH procedure

Step 2: SRB1 establishment + initial NAS msg

Step 3: NAS security + S1

setup Step 4: RRC security + UE capability

Step 5: SRB2 + DRB setup for default bearer

ThanksThanks

Prepared By :Surendra Singh Bundela Checked By: Sourabh Bhatham

LTE Field Training Document_Internal-1

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Transcript of LTE Field Training Document_Internal-1