ICLTERPOP Section 4_Configuration Options for LTE ENBs

Connected Mode Parameters

CONNECTED MODE PARAMETERS

© Informa Telecoms & Media


CONNECTED MODE PARAMETERS Defining RRC Connected Mode LTE IRAT Interactions RRC Reconfiguration Message Measurement Configuration Measurement Objects Reporting Configurations Measurement Identities Other Parameters Measurement Objects E-UTRA Measurement Objects IRAT (UMTS) Measurement Objects IRAT (GSM) Measurement Gap Settings LTE Measurement Reporting Configuration LTE Measurement Report Trigger Events IRAT Measurement Reporting Configuration IRAT Mobility Triggers LTE Speed Scale Factors Measurement Reports Measurement Report for UMTS Cells Measurement Report for GSM/GERAN

4 6 8 10 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40

Measurement Report for CDMA2000 Cells Inter-eNB Handover Procedure IRAT Handover Procedure UMTS Measurement Settings UMTS Event Triggers UMTS Measurement Report UMTS IRAT Handover Procedure Discontinuous Reception (DRX) Procedures Uplink Power Control Timing Advance CQI Reporting

42 44 46 48 50 52 54 56 58 60 62



Defining RRC Connected Mode The LTE RRC connected state is defined in TS 36.331 as shown in the diagram. It is similar to connected mode in other 3GPP technologies, but in LTE there is no dedicated channel. All signalling and traffic transfer between the UE and the eNB is handled through scheduling of the uplink and downlink shared channel resource. To avoid the need for continuous monitoring of the PDCCH for prolonged periods of time while in connected mode, the use of DRX, a feature normally associated with idle mode, is introduced. Note the UE is also required to maintain awareness of system information. Another key differentiator from idle mode is that mobility is under control of the network. Network behaviour in this respect is driven by parameters and mode settings broadcast in system information that are either part of manual or SON-based optimisation activities.

4


E-UTRA RRC CONNECTED

3GPP TS 36.331 defines connected mode with the following:

• Transfer of unicast data to/from UE • At lower layers, the UE may be configured with a UE specific DRX • Network controlled mobility, i.e. handover and cell change order with optional network assistance (NACC) to GERAN • The UE: – monitors a Paging channel to detect incoming calls, system information change; for ETWS capable UEs,

–

– – – –

ETWS-notification; and for CMAS-capable UEs, CMAS notification monitors a Paging channel and/or System Information Block Type 1 contents to detect system information change, for ETWS capable UEs, ETWS notification, and for CMAS capable UEs, CMAS notification monitors control channels associated with the shared data channel to determine if data is scheduled for it provides channel quality and feedback information performs neighbouring cell measurements and measurement reporting acquires system information

Fig. 1 – E-UTRA RRC Connected Mode © Informa Telecoms & Media

5


LTE IRAT Interactions LTE standards define handovers and cell reselection between the E-UTRAN and both UMTS and GSM/GPRS networks. Transition from LTE in idle mode is primarily through cell reselection, with the exception of GPRS, which may employ CCO (Cell Change Orders). In RRC_Connected mode, the E-UTRAN decides which cell a UE should hand over to in order to maintain the radio link. The diagram shows the state transition model for UMTS and GSM/GPRS. A UE will be either Connected or Idle with respect to the E-UTRAN. The substates CELL_PCH, URA_PCH and Cell FACH do not exist in LTE. Handovers will occur between cell DCH and LTE connected. However, a UE in the UMTS states CELL_PCH and URA_PCH would return to LTE through cell reselection. Similarly, real-time traffic will probably handover to/from GSM, whilst non-real-time traffic using GPRS will probably utilise CCO with NACC (Network Assisted Cell Change).

6


UMTS

LTE

GSM/GPRS

GSM Connected CELL_DCH

Handover E-UTRA RRC Handover Connected GPRS Packet transfer mode

CELL_FACH

CCO with optional NACC

CELL_PCH URA_PCH

Connection establishment/ release

Idle

Connection establishment/ release Reselection

Connection establishment/ release

CCO, reselection

Reselection

E-UTRA RRC Idle

Reselection CCO, reselection

GSM_Idle/ GPRS Packet_Idle

Fig. 2 – LTE IRAT Interactions © Informa Telecoms & Media

7


RRC Reconfiguration Message The RRCConnectionReconfiguration message is a multi-purpose message, using many sub headers to control a UE’s behaviour whilst in connected mode. Only relevant information elements will be included for mobility control, which will be investigated in detail throughout this section. The main information element that controls a connected mode UE is measConfig, which is used to set up, modify or remove measurement commands. In a similar manner to UMTS, a UE will be instructed to start measuring, and then when certain triggers or events occur, send measurement reports. Alternatively, measurement reports may be periodical.

8


RRC Connection Reconfiguration Message • Measurement Configuration

•

Mobility Control Information

•

Dedicated Information NAS List

•

Security Configuration

•

Non-Critical Extensions

eNB RRC Connection Reconfiguration DCCH/DL-SCH Periodical or event-

RRC Connection Reconfiguration Complete

based measurement process started

Trigger Event

DCCH/UL-SCH

Measurement Report DCCH/UL-SCH

Fig. 3 – RRC Reconfiguration © Informa Telecoms & Media

9


Measurement Configuration The measConfig IE (information element) consists of the following IE sets: • • • •

Measurement Objects Reporting Configurations Measurement Identities Additional parameters

Measurement Objects Measurement objects define either LTE, UMTS, GSM or CDMA2000 neighbours to measure. Each command is assigned a unique-per-UE measurement identity, and may include up to 32 neighbours per RAT/frequency layer.

10


RRC Connection Reconfiguration Message Measurement Configuration

measConfig Measurement Objects

•


•


measObjectToRemoveList measObjectId

List As Required

measObjectToAddModList

• •

Security Configuration Non-Critical Extensions

measObjectId

List As Required

measObject

LTE, UMTS, GSM or CDMA2000

1…n (Max =32)

Fig. 4 – Measurement Objects © Informa Telecoms & Media

11


Reporting Configurations Triggers or events for reporting are contained within the Reporting Configuration IE. Reports may be set to event based or periodical. Appropriate timers and hysteresis values will also be conveyed to a UE. A report configuration ID is used for each defined configuration message.

12



measConfig Reporting Configurations

•


•


• •


reportConfigTo RemoveList

List As Required

reportConfigToAddModList reportConfigId reportConfig Rat

List As Required

1…n (Max =32)

Event or Periodical and Details

Fig. 5 – Reporting Configurations © Informa Telecoms & Media

13


Measurement Identities Measurement Identities are used to bind together combinations of reporting configurations and measurement objects.

14



measConfig Measurement Identities

•


•


• •


measIdTo RemoveList

List As Required

measIdToAddModList measId

List As Required

1…n (Max =32)

measObjectId measConfigid

Fig. 6 – Measurement Identities © Informa Telecoms & Media

15


Other Parameters Other parameters which may be used are contained here including speed scaling, measurement gaps, measurement filter coefficients and serving cell quality thresholds. These will be covered later in this section.

16



measConfig Other Parameters

•


•


• •


Quality confi guration Meas. filter by type 0–9 and RAT 11, 13, 15, 17, 19 Measurement Gap

Gp1

0…39

Configuration S-Measurements

Gp2 Serving Cell Quality threshold

0…39 0–97 (–140 to – 44dBm)

–

–

preRegistrationInfo HRPD Speed Parameters t-Evaluation

30, 60, 120, 240 seconds

T-HystNorm

30, 60, 120, 240 seconds

N-cellChange Medium

1…16

N-cellChangeHigh 1…16 speedStateScale Factors Sf-Medium

0.25, 0.5, 0.75, 1.0

Sf-High

0.25, 0.5, 0.75, 1.0

Fig. 7 – Other Parameters © Informa Telecoms & Media

17


Measurement Objects E-UTRA The diagram shows an example of the parameters which may be used to control measurements on LTE cells. It is possible to instruct a UE to measure a frequency layer only (from 1.4 MHz to 20 MHz). The inclusion of the optional cellsToAddMod list allows more precise targeting of specific cells. Note that if the cellsToAddMod list is not included, cells may still be barred from the measurement command using black lists.

18


RRC Connection Reconfiguration Message measConfig Measurement Objects measObjectToRemoveList measObjectId

List As Required


Measurement Configuration •


•


•


•


measObjectId

List As Required

measObject


1…n (Max =32)

Measurement Objects EUTRA example CarrierFrequency

EARFCN

allowedmeasBandwidth

6, 15, 25, 50, 75, 100 rbs

presenceAntennaport1

True/false (MIMO)

Ncell configuration

MBSFN or TDD info

OffsetFrequency

–24…24dB

Cells to remove list

Indicies as requested

Cells to add or modify list Cellindex

1…n(Maximum32)

PhysicalcellID

0…503(PCI)

Individual cell offset Black cells to add list

–24…24 dBm 1…32

Black cells to remove list Cellindex

1…n(32max)

Physical cell range Start

0…503 (PCI)

Range

1,4,8,16,24,32,48,64, 84…504

CelltoreportCGI

0…503(PCI)

Fig. 8 – Measurement Objects EUTRA © Informa Telecoms & Media

19


Measurement Objects IRAT (UMTS) The measObject information element may include UMTS cells, as shown in the diagram. Up to 32 UMTS cells may be defined in each UMTS frequency layer. A UARFCN and cell code, corresponding to the primary scrambling code, is defined for UMTS neighbours.

20



List As Required




•


•


•


measObjectId

List As Required

measObject


1…n (Max =32)

Measurement Objects UTRA example CarrierFrequency

EARFCN

Offsetfrequency

–15…15dB

Cells to remove list

Indicies as required

Cells to add or modify list

FDD or TDD

Cellindex

1…n(Maximum32)

PhysicalcellID

FDD0…511 TDD 0…127

CelltoreportCGI

Asabove

Fig. 9 – UMTS Neighbour Definition © Informa Telecoms & Media

21


Measurement Objects IRAT (GSM) The measObject information element may include GSM neighbour cells, as shown in the diagram. Up to 32 GSM cells may be defined by listing ARFCNs. Note that no BSIC is included for GSM neighbours. However, the use of NCC permitted may be used restrict unwanted PLMN measurements.

22



List As Required




•


•


•


measObjectId

List As Required

measObject


1…n (Max =32)

Measurement Objects GERAN example StartingARFCN

ARFCN

Bandindicator

900/1800

Following ARFCNc ListofARFCNs ARFCN spacing

1…n(Maximum32) 1…8

Number of following ARFCNs 0…31 ARFCN bitmap Offset Frequency

Up tp 16 octetcs –15…15 dB (meas eval req)

NCCpermitted

8bit

CelltoreportCGI

BSIC

Fig. 10 – GSM/GERAN Neighbour Definition © Informa Telecoms & Media

23


Measurement Gap Settings Measurement gap parameters are used to define time periods when no uplink or downlink transmission will be scheduled for a specific UE, thus enabling a UE to take neighbour measurements. This is similar in concept to compressed mode in UMTS or Idle frames in GSM. LTE monitoring gap patterns occur in multiples of 10 ms, and have a duration of 6 ms. A single monitoring pattern is defined for both LTE neighbours and Inter-RAT. Note that the 6 ms gap period should be sufficient to allow a UE to synchronise onto LTE neighbours for cell identification. (PSS and SSS every 5 ms). However, careful selection of gap repetition must be employed to allow a UE to decode a GSM synch burst to obtain BSIC and the SFN.

24


Neighbour

Neighbour

Neighbour

MGL

Measurement Gap Length

MGRP

(Measurement Gap Repetition Period) measGapConfig Defines start position

eNB (Serving Cell)

Gap Pattern ID

MGL (MS)

MGRP (MS)

0

6

40

1

6

80

Fig. 11 – Measurement Gap Settings © Informa Telecoms & Media

25


LTE Measurement Reporting Configuration The diagram shows the parameters and trigger events a UE may be instructed to perform on neighbouring LTE cells. Depending on measurement type, a UE may measure and report serving cell, listed cells or any cells detected on a listed frequency. A UE can trigger a report based on either RSRP or RSRQ. However, both may be included in any report. The E-UTRAN can influence the UE report entry condition by setting configurable parameters such as offsets and hysteresis. For any event to be triggered the entry condition must be met for at least the ‘Time-to-Trigger’ value.

26


Event ID

measConfig

Event A1

Measurement Identities

A1 Threshold

Choice

Threshol d – RSRP

0…97 (maps to –140…–44 dBm)

Threshol d RSRQ

0…34 (maps to –19.5…–3 dB)

A2 Thre shold

Choice

Threshol d – RSRP

0…97 (maps to –140…–44 dBm)

Threshol d RSRQ

0…34 (maps to –19.5…–3 dB)

reportConfig Rat

List As Required

1…n (Max =32)


measConfig

Event A3

Report onleave

List As Required

reportConfigToAddModList reportConfigId

Event A2

A3 Off set


–30…3 0 True/false

Triggertype Event EventID

Event A4 A4 Thresh old

Choice

Threshol d – RSRP

0…97 (maps to –140…–44d Bm)

Threshol d RSRQ

0…34 (maps to –19.5…–3 dB)

A5 Thresh old 1

Choice

Threshol d – RSRP

0…97 (maps to –140…–44d Bm)

Threshol d RSRQ

0…34 (maps to –19.5…–3 dB)

A5 Thresh old 2

Choice

Threshol d – RSRP

0…97 (maps to –140…–44 dBm)

Threshol d RSRQ

0…34 (maps to –19.5…–3 dB)

Eventtriggerlist A1,A2,A3,A4,A5

Hysteresis

0…30in0.5bdsteps

Time to trigger

0, 40, 64, 80, 100…2560, 5120 ms

Periodical Purpose

Event A2

Choice

Trigger quantity Reportquantity Maxcellstoreport

Reportstrongestcells/ Report CGI RSRP/RSRQ RSRP/RSRQ 1to8

Report interval

120, 240, 480…102402ms 1, 2, 4, 60 minutes

Report amount

1, 2, 4, 8, 16, 32, 64, infinte

Fig. 12 – Measurement Reporting Configuration © Informa Telecoms & Media

27


LTE Measurement Report Trigger Events The diagram shows the event triggers defined for LTE. • • • • •

Event Event Event Event Event

A1 A2 A3 A4 A5

Serving cell becomes better than an absolute threshold. Serving cell becomes worse than an absolute threshold. Neighbour becomes better than an offset relative to serving cell. Neighbour cell becomes better than an absolute threshold. Serving cell becomes worse than an absolute threshold and neighbour cell becomes better than a second absolute threshold.

Remember that each event will have associated hysteresis and time-to-trigger values.

28


Event A1

Event A2

Serving Cell Absolute Threshold

Absolute Threshold Serving Cell

Event A3

Neighbour cell

Offset Serving Cell

Even At4

Neighbour cell

Absolute Threshold

Even At5

Neighbour cell

Absolute 1 Threshold Absolute Threshold 2 Serving Cell

Fig. 13 – LTE Event Triggers © Informa Telecoms & Media

29


IRAT Measurement Reporting Configuration The parameters relevant for IRAT reports are shown in the diagram. Note that monitoring of IRAT neighbours will be performed during available monitoring gaps. The three UMTS physical channels required for identification and measurement are P-SCH, S-SCH and CPICH. GSM requires RSSI and BSIC decode. Events may be periodical or event based, and as with LTE reports, appropriate hysteresis values and time-to-trigger will be set by the E-UTRAN.

30


Event ID

measConfig

Event B1

Measurement Identities

B1 Threshold UTRA

Choice

UTRA RSCP

–5 to 91(maps to –120…-25 dBm)

UTRAEc/No

0…49(maps to–24…0dB)

B1 Threshold GERAN

0…63 (maps to –110…–44 dBm)

Threshol d RSRQ


List As Required

reportConfigToAddModList reportConfigId reportConfig Rat

0…63

List As Required

1…n (Max =32)


Event B2 B2Threshold1

Choice

Threshol d – RSRP

0…97 (maps to –140…–44 dBm)

Threshol d RSRQ

0…34 (maps to –19.5…–3 dB)

B2Threshold2 B2 Threshold UTRAN

Choice Choice

UTRA RSCP

–5 to 91(maps to –120…-25 dBm)

UTRAEc/No

0…49(maps to–24…0dB)

B1 Threshold GERAN

0…63 (maps to –110…–44 dBm)

B1 Threshold CDMA2000

0…63

measConfig Triggertype Event Event ID

Choice Eventtriggerlist B1, B2

Hysteresis

0…30in0.5bdsteps

Time to trigger

0, 40, 64, 80, 100…2560, 5120 ms

Periodical Purpose

Maxcellstoreport

Reportstrongestcells/ Report strongest cells FOR SON/ Report CGI 1to8

Report interval

120, 240, 480…102402ms 1, 2, 4, 60 minutes

Report amount

1, 2, 4, 8, 16, 32, 64, infinte

Fig. 14 – IRAT Reporting Configuration © Informa Telecoms & Media

31


IRAT Mobility Triggers The diagram shows the two trigger events associated with IRAT mobility. • •

Event B1 Neighbour cell becomes better than an absolute threshold Event B2 Neighbour cell becomes better than an absolute threshold and serving cell becomes worse than an absolute threshold.

As for the other event reports, hysteresis and time-to-trigger values may be employed.

32


Event B1

Inter-RAT Neighbour cell Absolute Threshold

Event B2

Inter-RAT Neighbour cell

Absolute Threshold 2 Absolute Threshold 1 LTE Serving Cell

Fig. 15 – Inter RAT Mobility Triggers © Informa Telecoms & Media

33


LTE Speed Scale Factors In idle mode, it was seen that it is possible to apply hysteresis and scaling factors to a UE based on a number of cell reselections in a given time. The assessment of speed state whilst in connected mode is performed in a similar fashion. However, a UE will now count consecutive handovers. Based on a number of consecutive handovers a UE will apply a speed scaling factor to the time-to-trigger value, thus enabling better mobility management, especially in a hierarchical cell structure.

34


Connected Mode Parameter Value Range

Idle Mode Parameter

t-Evaluation

30,60,120,240secs

TCRmax

t-HystNormal

30,60,120,240secs

TCRmaxHyst

n-CellChangeMedium

1…16

NCR_M

n-CellChangeHigh

1…16

NCR_H

Normal Mobility

No Action

Medium Mobility

Time-to-trigger x sf-Medium

High Mobility

Time-to-trigger x sf-Medium

Fig. 16 – Speed Scale Factors © Informa Telecoms & Media

35


Measurement Reports A periodical or event-based trigger will cause the UE to generate a measurement report. The specific contents of the report will vary dependent on the measurement command provided by the E-UTRAN. Only information elements specifically asked for in the measurement command will be reported by the UE. For example, Cell Global Identity may or may not be included. Usually the physical cell identity will suffice. The diagram shows an example report for LTE (E-UTRA).

36


Measurement Report Triggertype measID

Choice 1…n(max=32)

measResultServingCell rsrp Result

0…97 (maps to –110…–44 dBm)

rsrp Result

0…34(maps to –19.5…–3dB)

measResultN-Cell

Choice

Result List E-UTRA

List as required

E-UTRA results

ResultUTRA

Listasrequired

PhysicalcellID

ResultGERAN

Listasrequired

cgi info

Result CDMA2000

CellGlobalID LAC plmnIDList

0…503

MCC+MNC+CID bit 16 Max=5

Measurement Results rsrpResult

0…97

rsrpResult

0…34 CSG information

Fig. 17 – Measurement Report E-UTRA © Informa Telecoms & Media

37


Measurement Report for UMTS Cells The diagram shows an example report for UMTS (UTRA) cells. Note that on receipt of the MobilityFromEUTRACommand message the UE will start timer T304 and attempt to connect to the new node. Expiry of this timer before a handover complete message will result in handover failure.

38





0…97 (maps to –110…–44 dBm)

rsrp Result

0…34(maps to –19.5…–3dB)

measResultN-Cell

Choice

Result List E-UTRA

List as required

ResultUTRA

Listasrequired

UTRA results

ResultGERAN

Listasrequired

PhysicalcellID

Result CDMA2000

FDD0…511 TDD 0…127

cgi info CellGlobalID LAC

MCC+MNC+CID bit 16

RAC

bit8

plmnIDList

Max=5

Measurement Results UTRA RSCP

–5…91 (maps to –120…–25dBm)

UTRAEc/No

0…49(maps to–24…0dB) CSG information

Fig. 18 – IRAT Measurement Report UMTS © Informa Telecoms & Media

39


Measurement Report for GSM/GERAN The diagram shows an example report for GSM/GERAN cells. Note that the MobilityFromEUTRACommand message will contain either a L3 signalling message from the destination BSS/GERAN or, in the case of CCO, a target cell and frequency.

40





0…97 (maps to –110…–44 dBm)

rsrp Result

0…34(maps to –19.5…–3dB)

measResultN-Cell

Choice

Result List E-UTRA

List as required

ResultUTRA

Listasrequired

ResultGERAN

Listasrequired

Result CDMA2000

GERAN results CarrierFrequency

ARFCN

PhysicalIdentity

BSIC

cgi info CellGlobalID RAC

MCC+MNC+CID bit8

Measurement Results RSSI

0…63(mapsto–110…–47dBm)

Fig. 19 – IRAT Measurement Report GERAN © Informa Telecoms & Media

41


Measurement Report for CDMA2000 Cells The diagram shows an example report for CDMA2000. For CDMA2000, additional procedures have been defined, using SRB1, to register a UE’s presence in the destination core prior to any handover procedure.

42


Measurement Report TriggerType measID



0…97 (maps to –110…–44 dBm)

rsrp Result

0…34(maps to –19.5…–3dB)

measResultN-Cell

Choice

Result List E-UTRA

List as required

ResultUTRA

Listasrequired

ResultGERAN

Listasrequired

Result CDMA2000

CDMA2000 results Physical Identity

0…511 (Pilot PN-Offset)

cgi info Cell Global ID

SID/NID = CID POSS. Sector ID

Measurement Results PilotPNhase Pilotstrength

0…32767 0…63

Fig. 20 – IRAT Measurement Report CDMA2000 © Informa Telecoms & Media

43


Inter-eNB Handover Procedure The diagram shows the air interface signalling flow for an Inter-eNB handover. The stages for handover are as follows: 1. The UE sends a measurement report. 2. The source eNB requests that the target cell prepares for handover. Note that in the case of X2-based handover either lossless or seamless handovers are defined. 3. If no X2 interface is available, an S1-based handover may be triggered by the source eNB. 4. The source eNB sends a RRCConnectionReconfiguration message to the UE, including mobility control IEs (new C-RNTI, Cell identity and, optionally, target cell frequency). 5. The UE will initiate the random access procedure and start timer T304. 6. After the successful random access procedure the UE stops timer T304.

44


MME

eNB

eNB

1. Measurement report

2. X2 Handover prep

3. S1 Handover prep 4. HO Command RRCConnectionReconfiguration 5. Random Access (T304 Started)

6. HO Complete (Stop T304) RRCConnectionReconfigurationComplete

Fig. 21 – LTE Handover Procedure (Inter-eNB) © Informa Telecoms & Media

45


IRAT Handover Procedure The major difference between an Inter E-UTRA handover and IRAT handover is that the E-UTRA has no direct connection to the target radio network. These interactions have to be handled by the MME. Once the MME has relayed the appropriate inter-RAT cell information to the source eNB it can instruct the UE to hand over using the MobilityFromEUTRACommand message. On receipt of this message the UE will change to the appropriate radio technology and implement the handover procedure. RRC or RR handover complete messages will then be used for UMTS and GSM respectively.

46


MME

Target CN

Target RAN

eNB Measurement report

Handover Prep

Handover Prep

Handover Prep

RRCConnectionReconfiguration Mobility from E-UTRA Command Handover Complete

Fig. 22 – LTE IRAT Handover Procedure © Informa Telecoms & Media

47


UMTS Measurement Settings The information elements contained in the diagram are passed to a UE in connected mode using RRC measurement control. For the purpose of LTE handover, the most relevant parameters will be the EARFCN and bandwidth information element. LTE itself is specified as a measurement object and no specific cell identities are defined. Note that a UE that is RRC connected and in the state Cell-DCH will be given compressed mode gap configuration information to enable inter-frequency measurements. Reporting criteria may be either event based or periodical and multiple events can be specified. The trigger points for events can be modified with time-to-trigger values and hysteresis.

48


Measurement Control

New Frequency List (8 maximum)

MeasurementID

E-UTRACarrier

1…n(max=16)

EARFCN

Measurement Command

Setup/modify/release

Bandwidth to measure

6, 15, 25, 50, 75, 100 rbs

Report Mode

AM/UM and Event/Periodical

Blacklistedcells

Listasneeded

Measurementtype

Choice

Physical Cell ID

OCI(0…503)

Intra-Frequency Inter RAT

Measurement Report Criteria (8 maximum)

Etc…

InterRATEventID

EARFCN

Own System Threshold

6, 15, 25, 50, 75, 100 rbs

LTE Inter RAT

W

0to2in0.1steps(3aonly)

Measurement Objects

Other System Threshold

–115…0 dBm (3a, b, c only) Value - IE-25

Hysteresis

0…7.5in0.5steps

Time to Trigger

0, 10, 20, 40…640, 1280, 2560, 5000ms

InterRATCellInfo

N/A

E-UTRA Hz List Removal New Frequencies

List as Required

Max. num. of cells to report

1…12

Measurement Quantity Measurement quantity

RSRP/RSRQ

Filter coefficiant

1, 2, 9, 11, 13, 19

Report quality

Oneor both (RSRP/Q)

Number of cells to report

1…12

Periodical Report Criteria Amount or repo rts

1, 2, 4, 8, 16, 32, Infinite

Report interval

250, 500, 1000, 2000…32000, 64000 millisecs

Report Criteria Measurement report criteria Periodical report criteria No report

Fig. 23 – UMTS Measurement Settings © Informa Telecoms & Media

49


UMTS Event Triggers The diagram shows the inter-RAT events and can be defined as follows: •

Event 3a

• • •

Event 3b Event 3c Event 3d

UMTS active set quality becomes worse than an absolute threshold and an LTE neighbour becomes better than an absolute threshold. An LTE neighbour becomes worse than an absolute threshold. An LTE neighbour becomes better than an absolute threshold. Best LTE neighbour cell change.

As UMTS is a CDMA system, a UE will potentially be involved in a soft handover and thus serving cell quality may be derived across an active set as follows: QUTRAN = 10•LogMUTRAN=W •10•Log •

• + (1-w)•10•logM

best

Where: Mi MBEST Na W

50

Quality of ith cell in active set Quality measure of best cell in active set Number of cells in active set Weighting factor to manipulate sum of Mi and MBEST


Event 3a

Inter-RAT LTE Neighbour cell

Event 3b

Absolute Threshold Other

Absolute Threshold

Absolute Threshold Own

Inter RAT LTE Neighbour cell UMTS Active set (QUTRAN)

Event 3c

Inter-RAT LTE Neighbour cell Absolute Threshold

Event 3d

Change of best n-cell

Inter-RAT LTE Neighbour cell 1

Inter RAT LTE Neighbour cell 2

Fig. 24 – UMTS Event Triggers © Informa Telecoms & Media

51


UMTS Measurement Report When the appropriate trigger conditions or period is met the UE will compose and send a measurement report. Note that prior to release 8, GSM CDMA2000 and intra-UMTS measurements could be reported. New information elements have been included in release 8 and a software upgrade in an existing UTRAN will be required to support LTE measurement reports.

52


Measurement Report

E-UTRA Measured Results

Measurement Identity

1…n (maximum 16)

Measured results list

4x field entities non applicable for LTE

N/A

E-UTRACarrierHz

EARFCN

Measuredcelllist

Maximum4

Additiona l measured resu lts

Up to 4

E-UTRA measured results E-UTRA event results

Maximum 4

Physical Cell ID

PCI(0…503)

RSRP

0…97(mapsto-–40…–144dBm)

RSRQ

0…33(mapsto–19.5…–3dB)

UTRA CSG frequency info

E-UTRA Event Results IRAT event identity

E3a, E3b, E3c, E3d

Eventresultlist

Maximum4

CarrierHz

EARFCN

Reported cells list

Maximum 4

Physical cell ID

PCI (0…503)

Fig. 25 – UMTS Measurement Report © Informa Telecoms & Media

53


UMTS IRAT Handover Procedure A UE that is RRC connected to the UTRAN may not necessarily be in compressed mode. It would be usual for a UE to send a measurement report (1) based on an event trigger such as e6a or e1f (Serving cell RSCP reduction or UE Tx Power respectively). This would allow an RNC to send a Measurement Command and physical channel reconfiguration information (2) to the UE with gap parameters for compressed mode and new measurement commands for LTE Neighbours. Once in compressed mode (3), if the appropriate trigger event is met (Event 3a to 3d) a UE will send a measurement report (4) to the RNC. The source UTRAN may then retrieve appropriate LTE cell information for the target eNB (via core network) and issue a Handover from UTRAN (5) command to the UE. The UE will then attempt to reconnect (6) via LTE using the LTE random access procedure.

54


UE Moving away from Node B

Node B

UE

eNB

1. Measurement report 2. Measurement command 3. UE in compressed mode 4. Measurement report 5. Handover command

6. Handover to LTE 7. Handover complete

A

B

C

Fig. 26 – UMTS IRAT Handover Procedure © Informa Telecoms & Media

55


Discontinuous Reception (DRX) Procedures DRX will be configured for a UE in connected mode so that a UE does not need to permanently monitor the PDCCH, thus saving battery life. The parameters for DRX have a trade-off between latency and battery life and are configurable for LTE. The onDurationTimer (Multiples of 1 ms) defines the amount of time the UE monitors downlink control channels whilst DRX is active. A short and long DRX cycle can be defined for LTE. If we take, for example, a UE involved in an active web browsing session, the long DRX cycle could be employed whilst a UE is RRC connected but no data is being received, and the UE will switch to the short DRX cycle when a web page has been downloaded to ensure no further data is immediately forthcoming. When a UE receives a scheduling message for its c-RNTI, it will start its DRX inactivity timer and begin to decode data. If instructed by a MAC control element, or if this timer expires, the UE will enter the short DRX cycle. If no data is received and the drxShortCycleTimer expires, then the UE may revert to the long DRX cycle.

56


On duration

Scheduling message reception

Inactivity timer or MAC CE reception

Short DRX cycle Timer expiry

Continuous reception

LongDRXcycle

Short DRX cycle

Long DRX cycle

RRC sends DRX parameters MAC CE activates DRX

eNB

Fig. 27 – Two Stage DRX Procedure © Informa Telecoms & Media

57


Uplink Power Control Uplink power control is needed in any mobile system, primarily to achieve a required Eb/No value at the eNB, but also to reduce overall system interference and preserve battery life. Detailed power control formulae are defined for LTE for the PUSCH, PUCCH and sounding reference signals. The formula for each channel follows the same basic principle and consists of a basic open-loop operating point (derived from static or semi-static parameters issued by an eNB) and dynamic offsets derived on a sub-frame basis. Note that a UE will never exceed maximum Tx power (23 dBm). The bandwidth element is derived from the number of scheduled radio blocks. The static/semi-static control point is derived from both the Po-PUSCH(j) (defined cell by cell from –126 dBm to +23 dBm) and Pl (an estimation of path loss made by the UE). TPC (Transmit Power Control) commands are transmitted on the PDCCH to individual UEs via a specific TPC_RNTI to control the dynamic closed loop offset. Note that a UE (for example capable of transmitting 23 dBm) must report power control headroom to the eNB. The eNB can then use this information to schedule uplink bandwidth to a UE. Power control headroom has a range +40 dBm to –23 dBm. The negative value would enable a UE to indicate that it has been allocated more radio blocks than it has power available to transmit in, thus enabling the eNB to reduce allocated uplink bandwidth.

58


UE TX Power = min{PCMAX, 10log10(MPUSCH(i)) + PO_PUSCH(j) + α(j).PL +∆TF(i) +f(i)} dBm Power class Bandwith factor, Basic open 23 dBm no. of RBs loop operating point

Dynamic offset

Individual or Group TPC commands sent In PDCCH Power Headroom report sent in Uplink grant (–23....+40 dB)

eNB

Fig. 28 – Uplink Power Control © Informa Telecoms & Media

59


Timing Advance Like GSM, timing advance must be employed by LTE to ensure uplink transmission from multiple UEs arrives at the eNB orthogonally. Uplink timing advance utilises MAC control elements to update UE transmission time based on distance from the base station to counteract different propagation delays. Initial timing advance is set during the random access procedure, allowing an initial setting with granularity from 0.52 µs to 0.67 ms. Granularity of subsequent timing advance commands is again 0.52 µs (or 16 Ts). The command utilises a 6-bit MAC CE with a range of 0–63. Values 0–31 reduce timing advance, 31–63 increase timing advance.

60


eNB

eNB

DL symbol Txd at eNB

DL symbol RXd at UE, Tp1 propagation delay TP1

Tp1 2Tp1 Timing Advance = 2Tp1

UL transmitted symbol timing

UL symbol arrives at eNB. delay 2Tp1

2Tp1

Tp1

Fig. 29 – Timing Advance © Informa Telecoms & Media

61


CQI Reporting Link adaptation, or the process by which a transmitter should try to match the appropriate data rate for each user’s variable air interface characteristics, is utilised within LTE. The AMC process will define both the modulation scheme (from QPSK to 64QAM) and amount of error protection required for both uplink and downlink transmission. Uplink adaptation should be calculated by the source eNB based on measurements of uplink UE transmission, or, alternatively, an eNB may request a UE to transmit sounding reference signals. A UE can be configured to report CQI values in order to allow the eNB to determine an appropriate downlink Modulation and Coding Scheme (MCS) as seen in the diagram. Note that the CQI value is NOT a direct indication of SINR, but an indication of the highest MCS that it can decode with a transport block error rate probability not exceeding 10%.

62


CQIIndex 0

Modulation Tx

No

CodeRateApprox –

SymbolEfficiency

–

1

QPSK

0.076

0.15

2

QPSK

0.12

0.23

3

QPSK

0.19

0.37

4

QPSK

0.3

0.60

5

QPSK

0.44

0.87

6

QPSK

0.59

1.17

7

16QAM

0.37

1.47

8

16QAM

0.48

1.91

9

16QAM

0.6

2.40

10

64QAM

0.45

2.73

11

64QAM

0.55

3.32

12

64QAM

0.65

3.90

13

64QAM

0.75

4.52

14

64QAM

0.85

5.11

15

64QAM

0.93

5.55

Downlink Adaptation based On UE CQI reporting

64QAM 16QAM

16QAM

QPSK

QPSK

eNB CQI 8

CQI 12

CQI 7

CQI 4

CQI …

Fig. 30 – CQI Reporting © Informa Telecoms & Media

63

ICLTERPOP Section 4_Configuration Options for LTE ENBs

Recommend Documents