module 5-lte optimization guideline

www.DigiTrainee.com Company Confidential

LTE Optimization Guideline

Section-5

RNO Consultant : Ray Khastur

Version: V 1.0 (20151028)


Objectives

Upon completion of this course, you will be able to

Know Drive Test Tools, Site Audit Check.

Know definition of RSRP and how to calculate RSRP transmit power for different Bandwidth.

Know definition of SINR and impact of traffic in different traffic usage, and understand how to improve

SINR in some Drive Test Result.

Know how LTE do Cell Search and Reselection Process and Procedure.

Know how LTE Scheduling Procedure.

Know some SON Feature and the function.

Page 2


Contents

1.Overview

2.RSRP Introduction

3.SINR Introduction

4.Cell Search & Cell Reselection

5.LTE Scheduling

6.LTE SON Feature

Page 3

www.DigiTrainee.com Company ConfidentialPage 4

Overview


Drive Test Peripheral

Page 5

Notebook

GPS

LTE Dongle


Daily Pre Check DT Tools

Configuration

Page 6

Samsung

Galaxy Note 4

Mf90

Samsung

Galaxy J5

To make sure

Drivetest result

showing better

performance.

Each time DT Team will go to

field, they have to

send tools

configuration by

email.


On Site Hardware

Page 7

RRU : Radio Remote Unit

BBU : Baseband Unit

MIMO Antenna


Site Audit Report

Page 8

Compass

View

Tilt Meter

View

Electrical

Tilt Meter

View

Panoramic

View

In this part show details of

site location

In this part show details Hardware Parameter

Value.

Make sure all data taken with correct way to

prevent wrong measurement.


RSRP Introduction


RSRP (Reference Signal Receive Power)

RSRE Power = Psingle port-10*log(12*Nrb)+10*log(1+Pb)

Where ; PSingle Port = PRRU - 10*log(Nport)

Pb is Power Bosting

Page 10

Psingle port = 49-10*log(4)

= 43 dBm

= 20Watt

PB

B/ A

Single

Antenna Port

2 or 4

Antenna Port

0 1 5/4

1 4/5 1

2 3/5

3 2/5

Impact on Radio Network

Performance: A larger value of Pb

results in a larger increase in

ReferenceSignalPwr, better

channel estimation performance,

and better PDSCH demodulation

performance, but it also leads to

lower transmit power of the PDSCH

(type B) and thus increases


RSRP Contd

Page 11

Power Boosting for RS

PB =1 by default

RS Power for 20MHz

= 43 10*log(100*12) + 10*log10(PB+1) = 15.2dBm

Bandwidth PB PRS ( dBm)

10M 1 18.2

15M 1 16.4

20M 1 15.2


Why RSRP Level lower than other Receive Power (2G/3G)

Page 12

Items GSM UMTS LTE

(e)NodeB power per Tx (dBm)43 43 43

Bandwidth (MHz) 0.2 5 20

Number of RB N/A N/A 100

BCCH Power/ CPICH power

/RS power per RE (dBm)

43 33 15.2

CL (dB) 120 120 120

Rx Lev/RSCP/RSRP (dBm)-77 -87 -104.8

Received RS signal strength

over whole bandwidth

-81.8

RSRP is the received signal

strength over 15KHz bandwidth while bandwidth of RSCP is 5MHz

RSRP of LTE is much smaller than RSCP of UMTS under same radio environment

Only 1/6 REs is used for RS transmission

within one RB and hence the total

received RS power is

10*log10(100*12*1/6) = 23dB higher than

RSRP


Recommendation Value

PB PA

0 0

1 -3

2 -4.77

3 -6

Page 13


SINR Introduction


SINR (Signal to Interference & Noise Ratio)

Page 15


If there are 100 UE in a

cell (100RB) in the same scheduled to use PRB, each user will got 1 PRB.

More less UE got PRB more high Tx Power will

be send from the UE. Which causing UL Interference increased

also.


1 2 3 4 5 6 7 8 9 ~ ~ 93 94 95 96 97 98 99 100

x x x x x

x x x x x

x x x x x

1 2 3 4 5 6 7 8 9 ~ ~ 93 94 95 96 97 98 99 100

x x x

x x x

x x x

X : Available PRB on overlapped area

More smaller PRB scheduled for one UE in busy hour, will make power transmit will more high which

causing Noise Figure increase for entire cell and impact to SINR. More high PRB Utilization will causing

high probability of collision PRB on the cell edge which contribute to more degradation on cell edge.


PCI Mod 3 RS shift among neighbor cells

Page 18

Frequency domain location of the RS is determined by value of PCI mod 3

If RS is shifted, then it will help for better performance under low load

RS location vs PCI mod 3:


SINR Comparison

Afternoon 16:00 Midnight 02:00


SINR Comparison


CQI Comparison



DL Throughput Comparison


During Low Utilization of DL PRB on Cell Level give benefit for single UE can get

higher DL PRB which is related to the Higher DL Throughput.


DL Throughput Comparison

During Low Utilization of DL PRB on Cell Level give benefit for single UE can get

higher DL PRB which is related to the Higher DL Throughput.


CQI to MCS

CQI stands for Channel Quality Indicator. As the name implies, it is

an indicator carrying the information on how good/bad the

communication channel quality is. This CQI is for HSDPA. (LTE

also has CQI for its own purpose).

CQI is the information that UE sends to the network and practically

it implies the following two

i) Current Communication Channel Quality is this-and-that..

ii) I (UE) wants to get the data with this-and-that transport block

size, which in turn can be directly converted into throughput

Page 25


LTE Cell Search & Cell Reselection


MIB & SIB Information

Page 27


RNTI

One of the other numbers which you would very frequently come accross is RNTI. RNTI stands for Radio Network

Temporary Identifier.

As the name implies, it is a kind of Identification number. Normally we use indentification number to differntiate one thing

from all other similar things. For example, your driver's license number let you identify yourself from all other drivers.

Social Security number do the same thing as well.

Getting more specifically into LTE, this RNTI is used to indentify one specific radio channel from other radio channel and

one user from another user. As you may recall, in WCDMA is a RNTI concept which is carried as part of MAC header to

deferentiate one user to another while in communication state. and in WCDMA case it used special channelization code to

deferentiate one radio channel from the other.

Types of RNTI

P-RNTI : It stands for Paging RNTI. Used for Paging Message.

SI-RNTI : It stands for System Information RNTI. Used for transmission of SIB messages

RA-RNTI : It stands for Random Access RNTI. Used for PRACH Response.

C-RNTI : It stands for Cell RNTI. Used for the transmission to a specific UE after RACH.

T-CRNTI : It stands for Temporary C-RNTI. Mainly used during RACH

SPS-C-RNTI : It stands for Semi persistance Scheduling C-RNTI

TPC-PUCCH-RNTI : It stands for Transmit Power Control-Physical Uplink Control Channel-RNTI

TPC-PUSCH-RNTI : It stands for Transmit Power Control-Physical Uplink Shared Channel-RNTI

M-RNTI : It stands for MBMS RNTI

Page 28


Signaling Radio Bearer

SRB0 is for RRC messages using the CCCH logical channel;

SRB1 is for RRC messages (which may include a piggybacked NAS

message) as well as for NAS messages prior to the establishment of

SRB2, all using DCCH logical channel;

SRB2 is for RRC messages which include logged measurement

information as well as for NAS messages, all using DCCH logical

channel. SRB2 has a lower-priority than SRB1 and is always configured

by E-UTRAN after security activation.

Page 29


SRB Mapping

MasterInformationBlock

- Signalling radio bearer: N/A

- RLC-SAP: TM

- Logical channel: BCCH

- Direction: E-UTRAN to UE

SystemInformationBlockType1


- RLC-SAP: TM

- Logical channel: BCCH


RRCConnectionRequest

- Signalling radio bearer: SRB0

- RLC-SAP: TM

- Logical channel: CCCH

- Direction: UE to E-UTRAN

RRCConnectionSetup


- RLC-SAP: TM

- Logical channel: CCCH


Page 30

RRCConnectionSetupComplete


- RLC-SAP: AM

- Logical channel: DCCH


RRCConnectionReconfiguration


- RLC-SAP: AM



MeasurementReport


- RLC-SAP: AM



MobilityFromEUTRACommand


- RLC-SAP: AM



UECapabilityEnquiry


- RLC-SAP: AM



UEInformationRequest


- RLC-SAP: AM



DLInformationTransfer

- Signalling radio bearer: SRB2 or

SRB1 (only if SRB2 not established

yet. If SRB2 is suspended, E-

UTRAN does not send this message

until SRB2 is resumed.)

- RLC-SAP: AM



Paging


- RLC-SAP: TM

- Logical channel: PCCH



LTE Cell Search & Uplink

Synchronization

In LTE User Equipment (UE) must be able to do cell search, initial synchronization and random access procedure for

downlink and uplink access. To perform cell search, and initial synchronization, two synchronization signals, Primary

Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS), are periodically transmitted from the base

station in the LTE system. Using these two signals and making use of the properties of Zadoff-Chu (ZC) and Pseudo-

Noise (PN) sequence, the mobile unit will determine on which of the available cell sites it should lock into and it acquires

time and frequency synchronization. After UE will do random access procedure using Physical Random Access Channel

(PRACH). An appropriate design of PRACH preamble is essential to provide frequent enough random access

opportunities and an accurate UE synchronization estimation to adapt to different cell ranges and network conditions

without using unnecessary resources. This paper presents the complete LTE access procedure and more about PRACH

implementation and detection. Then the performance of the PRACH synchronization procedure under different parameter

settings is compared in a typical scenario of LTE.

Page 31


PRACH TDD & FDD

Random Access Channel (RACH)

RACH procedure begins with a preamble (PRACH)

PRACH resources assigned by eNB within PUSCH region

PRACH preamble fits into 6 PRBs

Sufficient for timing estimation

Invariant with bandwidth for low complexity

Zadoff Chu sequence

Excellent correlation properties

Zero correlation zone for different cyclic shifts

Flat frequency spectrum

Different sequences provided first by different cyclic shifts, then by different root sequences

Multiple PRACH formats suitable for different cell sizes

Page 32


PRACH Types

Page 33

Typical 'Contention Based' RACH Procedure is as follows :

i) UE --> NW : RACH Preamble (RA-RNTI, indication for L2/L3

message size)

ii) UE NW : L2/L3 message

iv) Message for early contention resolution

Typical 'Contention Free' RACH Procedure is as follows :

i) UE NW : RACH Preamble (RA-RNTI, indication for L2/L3 message

size)

iii) UE


PRACH Performance

Monitoring Principles

The physical random access channel (PRACH) transmits preambles during random access procedures. Preamble is classified into c ontention

preamble and non-contention preamble. Contention preambles are used in the following scenarios: initial connection establishment,

reestablishment, handover, downlink data transmission for UEs in the out-of-synchronization state, and uplink data transmission for UEs in the out-

of-synchronization state. Non-contention preambles are used in two scenarios: handover and downlink data transmission for UEs in the out-of-

synchronization state. Therefore, PRACH performance can be measured using the following factors:

Conflict probability for contention-based preambles: The more frequently the contention-based access is performed, the higher

probability that the preambles are conflicted. When the conflict probability reaches a certain extent, the access delay increases,

severely affecting user experience.

Assignment success rate for dedicated preambles: The assignment success rate for dedicated preambles decreases with the increase

of non-contention-based accesses. When the success rate decreases to a certain extent, the handover delay increases, affecting user

experience.

Monitoring Methods

Conflict probability for contention-based preambles = L.RA.UeRaInfoRspWithCon.Num / L.RA.UeRaInfoRsp.Num x 100%

Assignment success rate for dedicated preambles = L.RA.Dedicate.PreambleAssign.Num / L.RA.Dedicate.PreambleReq.Num x100%

whereL.RA.UeRaInfoRspWithCon.Num indicates number of times the UEInformationResponse message in which contentionDetected IE value is

TRUE is received, that is, the number of times the conflicting UEInformationResponse message is received.

L.RA.UeRaInfoRsp.Num indicates the number of times the UEInformationResponse message containing RACH information is received.

L.RA.Dedicate.PreambleAssign.Num indicates the number of times the non-connection-based preambles are assigned.

L.RA.Dedicate.PreambleReq.Num indicates the number of times the non-contention-based preamble is requested.

Suggested Measures

If the conflict probability for contention-based preambles reaches or exceeds 5% for X days (three days by default) in a week, enable the

RACH adjustment algorithm by running the command MOD CELLALGOSWITCH: LocalCellId=x, RachAlgoSwitch=RachAdjSwitch-1.

If the assignment success rate for dedicated preambles is less than 99% for X days (three days by default) in a week, enable the RACH

resource adjustment algorithm and reuse of dedicated PRACH preambles between UEs by running the command MOD CELLALGOSWITCH:

LocalCellId=x, RachAlgoSwitch=RachAdjSwitch-1, RachAlgoSwitch=MaksIdxSwitch-1;.

Page 34

http://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/perf/ratL/enodeb/b-enodeb-perf/Mt-1526728913.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/perf/ratL/enodeb/b-enodeb-perf/Mt-1526728913.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/perf/ratL/enodeb/b-enodeb-perf/Mt-1526728939.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/perf/ratL/enodeb/b-enodeb-perf/Mt-1526728937.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/perf/ratL/enodeb/b-enodeb-perf/Mt-1526728913.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/perf/ratL/enodeb/b-enodeb-perf/Mt-1526728913.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/perf/ratL/enodeb/b-enodeb-perf/Mt-1526728939.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/perf/ratL/enodeb/b-enodeb-perf/Mt-1526728937.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/mml/ratL/mml/mod_cellalgoswitch.htmlhttp://localhost:7890/pages/31188306/Darft A/31188306/Darft A/resources/hert/mbts/mml/ratL/mml/mod_cellalgoswitch.html


PLMN Selection

When a UE is powered on or moves from a

coverage hole to a coverage area, the UE first selects the last

RPLMN and attempts to register

with that PLMN. If a UE has registered successfully with a PLMN,

the UE shows the selected

PLMN on its screen, and now it can receive service from an

operator. If the last RPLMN is

unavailable or registration on this PLMN fails, another PLMN can

be automatically or manually

selected based on the priorities of PLMNs stored in the USIM.

Page 35


Uplink Data Transmission

Scheduling - Persistent SchedulingThere are a couple of Data Transmission Scheduling Scheme

in LTE. The most simple in terms of algorithm would be the

persisent scheduling. In this scheduling mode, Network send

'Grant' in DCI Format 0 for every subframe.

i) Network send the first data on DL PDSCH and PDCCH

which has DCI format 1 for DL Data Decoding and DCI format

0 for UL Grant. (If there is no downlink data to be transmitted,

network transmits only DPCCH with DCI format 0 without any

DPSCH data)

ii) UE decode PCFICH to figure CFI value.

iii) UE decode PDCCH and get the information on DCI format

1

iv) Based on DCI format 1, UE decode DL data.

v) UE decode the information on DCI format 0 from PDCCH

vi) UE send ACK/NAK for DL data through UCI (UCI will be

carried by PUCCH)

vii) UE check the Grant field.

viii) If Grant is allowed, UE transmit the uplink data through

PUSCH

ix) Network decode PUSCH data and send ACK/NACK via

PHICH

x) UE decode PHICH and retransmit the data if PHICH

carries NACK

Page 36


Uplink Data Transmission Scheduling - Non Persistent Scheduling

In Persistent Scheduling mode, UE can send the

data to Network anytime since Network is sending UL

Grant all the time. But what if Network does not send

UL Grant all the time ? In this case, UE has ASK the

network to send UL Grant (DCI 0). If network send

UL Grant, then UE can send UL data as allowed by

the UL Grant.

Overall procedure is as follows :

i) UE send SR (Scehduling Request) on PUCCH

ii) Network send UL Grant (DCI 0) on PDCCH

iii) UE decode DCI 0 and transmit PUSCH based on

the RBs specified by DCI 0

iv) Network decode the PUSCH

v) Network send ACK/NACK on PHICH

vi) If Network send NACK, go to step i)

Page 37


Connection Management

UE State

RRC_CONNECTED

ACTIVE SLEEP

DRX

RRC_IDLE MODE

Intra Freq Cell

Reselection

Inter Freq Cell

Reselection

In this PPT only discussed about

INTRA FREQUENCY and INTER FREQUENCY

With Equal Priority


Cell Selection Criteria

During cell selection, a UE selects an E-UTRAN cell that meets the cell selection criteria. The

UE can camp on a cell only when the RSRP and reference signal received quality (RSRQ) of

the cell are greater than the values of the CellSel.Qrxlevmin and CellSel.Qqualmin parameters,

respectively.

A UE selects an E-UTRAN cell to camp on when the cell meets both of the following conditions:

Srxlev > 0

Squal > 0

where: Srxlev = Qrxlevmeas - (Qrxlevmin + Qrxlevminoffset) - Pcompensation

Squal = Qqualmeas - (Qqualmin + Qqualminoffset)

The variables in the previous formulas are described as follows:

l Qrxlevmeas: measured received signal level (that is, measured RSRP), expressed in dBm.

l Qrxlevmin: minimum required received signal level configured on the eNodeB, expressed

in dBm.

l Qrxlevminoffset: offset to the value of Qrxlevmin. In cell selection, this offset is considered

when the UE in a VPLMN attempts to camp on a cell in a higher-priority PLMN.

l Pcompensation: max (PMax - UE Maximum Output Power, 0), expressed in dB.

PMax: maximum transmit power (expressed in dBm) of the UE during uplink

transmission.

UE Maximum Output Power: maximum output power (expressed in dBm) of the UE.

l Qqualmeas: measured received signal quality (that is, measured RSRQ), expressed in dB.

l Qqualmin: minimum required received signal quality configured on the eNodeB, expressed

in dB.

l QQualminoffset: offset to Qqualmin. In cell selection, this offset is considered when the

UE in a VPLMN attempts to camp on a cell in a higher-priority PLMN.

Page 39

www.DigiTrainee.com Company Confidential40

Cell Reselection Trigger (Intra Frequency)

Cell Reselection Trigger

Time Domain

RSRP-60

-70

-80

-90

-100

-110

-120

-130

-140

SIntraSearch = 29 (2dB)

= 58 dB

Srxlev < SintraSearch

RSRP + 128 < 58

RSRP < -70

Cell will implement the

Intra Freq Search if:

-70 >RSRP> -128

SIn

traS

ea

rch

-70

-128 (Srxlevel)


Cell Reselection Trigger (Equal Priority) Intra & Inter

R_s=Qmeas,s + Qhyst

R_n=Qmeas,n - CellQoffset

TR

ES

EL

EU

TR

AN


Time Domain

RSRP-90

-92

-94

-96

-98

-100

-102

-104

-106

Qhyst = 4 dB

CellQoffset = 0 dB

TRESELEUTRAN = 1 s


Cell Reselection with Default Value (Equal Priority)

R_s=Qmeas,s + Qhyst

R_n=Qmeas,n - CellQoffset

TR

ES

EL

EU

TR

AN


Time Domain

RSRP

R_n

R_s

Note: Please see on the Full Screen Mode

Qhyst = 4 dB

CellQoffset = 0 dB

TRESELEUTRAN = 1 s

Conclusion : With default value, with Serving cell RSRP quite strong,

UE can do cell reselection after elapsed from Timer

RSRP-90

-92

-94

-96

-98

-100

-102

-104

-106


Paging

The purpose of paging is to transmit paging information to a UE in idle mode or to inform all

UEs in the EMM-REGISTERED state about a system information change. A paging procedure

can be initiated by either an MME or an eNodeB.

When an MME initiates a paging procedure, the paging message contains a tracking area list

(TAL) for the concerned UE. In all the cells within the TAs on the list, the eNodeBs transmit

the paging message over the paging control channel (PCCH) to page the UE. To increase the

probability that the UE successfully receives the message, the eNodeBs send the paging message

over the radio interface a number of times specified by the PCCHCFG.PagingSentNum

parameter. The paging message contains the domain information and UE identity. The domain

information indicates the origin of paging, and the UE identity may be the S-temporary mobile

subscriber identity (S-TMSI) or international mobile subscriber identity (IMSI) of the UE.

When system information changes, the eNodeB transmits a paging message to notify all UEs in

the EMM-REGISTERED state in the cell and transmits the updated system information in the

next modification period. To ensure that all of these UEs receive the system information, the

eNodeB transmits the paging message on all possible occasions in discontinuous reception

(DRX) cycles.

Page 43


Paging One TAL = One TAC

One TAL is same with one TAC, with this design when the

UE in idle condition then move to another TAC it will be generate TAU to report MME where is last position for this

UE. When there is downlink packet data need to be

deliver for that UE, MME can easily to find latest position.

TAU Procedure

The tracking area update (TAU) procedure is triggered if one of the follow ing conditions is met:

The UE detects that the current TA does not exist in the TA list on the UE-

registered netw ork.

It is a periodic TAU.

The TAU procedure is triggered during a handover procedure.

On an EPS netw ork, the basic unit of location management is TA List. A TA List consists of one or multiple TAs. A TA list prevents a UE from initiating the TAU

procedure frequently. In USN1.1, a TA is regarded as a TA List by default.

S-GWInternet MME

TAC 1

TAC 2

TAC 3

TAC 4

TAUTAU


TAL 1

Paging One TAL = Multiple TAC

One TAL contains multiple TAC, with this design when UE

in idle condition move to different TAC under one TAL there is no TAU. When MME want to deliver downlink

packet data for that UE MME will send to latest TAC

where the UE located. If the UE is unreachable MME will try to paging another TAC under one TAL until found. This

design will take a time compare with the previous design.

S-GWInternet MME

TAC 1

TAC 2

TAC 3

TAC 4

TAL 2

TAC 5

TAC 6

TAC 7

TAC 8

Under One TAL

no need TAU

UE move to

new TAL need

TAU

Last TAC is 8

but UE move to

TAC 7, MME

w ill try paging

another TAC under TAL2


LTE Scheduling


List Scheduling on LTE HUAWEI

Page 47


Priority of DL Scheduling

Page 48


Control Plane DL Scheduling

During scheduling in each subframe, control-plane messages are preferentially scheduled before user-plane data. Control-plane

information consists of common control information and dedicated control information.

Common Control Information

Common control information includes broadcast messages such as SIB1 and SIB2, and paging

messages. SIB is short for system information block. Scheduling common control information

uses QPSK and low coding rates for reliable transmission.

3GPP specifications define three downlink allocation modes:

l Resource allocation of type 0



Resource allocation of type 2 is used to allocate resources to common control information. In

resource allocations of type 2, the allocations are classified into distributed virtual resource block

(DVRB) allocations and localized virtual resource block (LVRB) allocations.

The following describes DVRB allocations and LVRB allocations:

l DVRB allocation applies to the non-contiguous allocation of resource blocks and increases

the coverage of common control information. However, the system resources occupied by

common control information increases, resulting in a decrease in the UE throughput.

l LVRB allocation applies to the contiguous allocation of resource blocks and decreases the

amount of system resources occupied by common control information, which increases the

UE throughput. However, the coverage of common control information decreases.

LVRB allocations are currently used.

Dedicated Control Information

Dedicated control information includes random access (RA) response and the information

carried on signaling radio bearer (SRB) 0, SRB1, and SRB2.

Page 49


HARQ Retransmission

HARQ retransmissions cannot be performed for a UE in any of the following

scenarios:

l The UE is in a measurement gap or enters a measurement gap when it

sends an HARQACK.

l The UE enters sleep time in DRX and the HARQ operating status is

discontinuous

transmission (DTX).

l The UE is not synchronized with the eNodeB or a radio link failure (RLF)

occurs.

HARQ retransmissions are scheduled after control-plane messages. The

scheduling priorities of different HARQ retransmissions are determined by

the wait time. A longer wait time indicates

Page 50


SPS Scheduling

As the importance of supporting

voice in LTE networks (VoLTE) increases, concerns arise regarding the number of

simultaneous voice calls that can be handled. One of the primary

constraints is the amount of capacity on the Physical Downlink Control Channel (PDCCH). As a

quick review, the PDCCH carries all allocation information for both

the downlink and uplink shared channels, PDSCH and PUSCH respectively. Each allocation is

carried as Downlink Control Information (DCI) and the size of

the DCI depends upon several factors including whether it is for uplink or downlink allocation.

Page 51

Since the PDCCH is limited size

(generally, 3 OFDM symbol times), there is a limit as to how many DCIs can be carried in a

subframe (1 ms). This can in-turn limit the number of UEs which can

receive an allocation for that subframe when using dynamic scheduling (a 1:1 PDCCH-to-

PxSCH method.


SPS Scheduling Contd

In order to support more

allocations, without increasing the size of the PDCCH, we can use semi-persistent scheduling (SPS).

With SPS, the UE is pre-configured by the eNB with an

SPS-RNTI (allocation ID) and a periodicity. Once pre-configured, if the UE were to receive an

allocation (DL / UL) using the SPS-RNTI (instead of the typical

C-RNTI), then this one allocation would repeat according to the pre-configured periodicity.

Page 52


SPS Scheduling Contd

During SPS, certain things remain

fixed for each allocation : RB assignments, Modulation and Coding Scheme, etc. Because of

this, if the radio link conditions change, a new allocation will have

to be sent (PDCCH). Also, any incremental redundancy (HARQ subsequent transmissions) will be

separately scheduled using dynamic scheduling. Also, to

avoid wasting resources when a data transfer is completed, there are several mechanisms for

deactivating SPS (explicit, inactivity timer, etc.).

So, with SPS which is well suited to periodic communication like

voice, we can support many more allocations with the same PDCCH

resource. This can allow more simultaneous VoLTE calls.

Page 53


Resource Allocation on LTE

Reading various LTE specification, you will see many terms

which seems to be related to resource allocation but looks

very confusing. At least you have to clearly understand the

following units.

i) Resource Element(RE) : The smallest unit made up of 1

symbol x 1 subcarrier.

ii) Resource Element Group (REG) : a group of 4

consecutive resource elements. (resource elements for

reference signal is not included in REG)

iii) Control Channel Element (CCE) : a group of 9

consective REG

iv) Aggregation Level - a group of 'L' CCEs. (L can be

1,2,4,8)

v) RB (Resource Block) : I think everybody would know

what this is. This is a unit of 84 resource elements which is

12 subcarrier by 7 symbols (This is with normal Cylic Prefix

which is used in most of the LTE deployment. If it is with

Extended Cyclic Prefix, the number of symbols within a

subframe become 6 and the number of resource elements

in a single RB become 72).

vi) RBG (Resource Block Group) : This is a unit comprised

of multiple RBs. How many RBs within one RBG differs

depending on the system bandwidth.

Page 54


PDCCH Allocation on LTE

Page 55


LTE SON Feature


MRO

As mobile telecommunications technologies advance, networks continue to grow and

incorporate multiple radio access technologies (RATs), resulting in complicated

network

maintenance. To simplify maintenance, an LTE system must support self-organizing

network

(SON) technology. MRO is used for self-optimization in an SON.

MRO collects handover performance statistics for different scenarios, identifies

abnormal

handover scenarios, and optimizes the mobility-related parameter settings. MRO

helps to reduce

the number of handover failures and service drops caused by premature and

delayed handovers,

handovers to wrong cells, or ping-pong handovers to achieve better resource

utilization and

improve user experience.

In this document, the triggering quantity and reporting quantity used in handover

measurements

for MRO are based on reference signal received power (RSRP).

Page 57


MRO Contd

Page 58

The eNodeB identifies

premature handovers,

delayed handovers,

handovers to wrong

cells, and

ping-pong handovers,

and counts the number

of each type of abnormal

handovers.


MIMO

MIMO is developed to provide doubled and more spectral efficiency. As an extension of singleinput

single-output (SISO), MIMO uses multiple antennas at the transmitter and/or receiver in

combination with some signal processing techniques. Generally speaking, single-input multipleoutput

(SIMO), multiple-input single-output (MISO), and beamforming also belong to the

MIMO category.

Page 59


MIMO Contd

Page 60


Adaptive ICIC: Improve 30% Cell Edge Throughput

Adaptive ICIC switch on / off

Support cell edge frequency

reuse (1, 1/3, 1/6).

Frequency: reuse=1Frequency: reuse=3

Cell Edge

Interference

High

Cell edge interference lead

to low throughput

Unique cell edge frequency reuse 6 in telecom

industry

Adaptive ICIC:

Cell Edge

Throughput

Low Cell Edge Interference

Low

Cell Edge

Throughput

30%improved

eCoordinator

ICIC


ICIC RSRP Comparison

CCU Power Reduction with ICIC


ICIC Contd

Page 63

CEU (-1.77 dB) CCU (-6 dB)

Mod1

Mod2

Mod3

From the graph we can see on

ICIC there is power control on cell

edge more have high transmit

power than cell center to

differentiate between cell edge into 3 frequency. This theory proven

from the previous slide.


ICIC SINR Comparison

Afternoon 16:00 (Default) Afternoon 16:00 (Mod3 ON) Afternoon 16:00 (ICIC)


ICIC SINR Comparison

ICIC is a technology that collaborates with power control and media access control (MAC)

scheduling technologies to mitigate inter-cell interference. ICIC divides the entire system

band into three frequency bands and uses different frequency bands at the edge of

neighboring cells. CEUs, which cause high interference or may be sensitive to interference,

are preferentially scheduled in the cell edge bands to mitigate inter-cell interference. The

interference mitigation enhances the network coverage and improves the CEU throughput.

There are significant

improvement of SINR

>0dB when static ICIC

implemented on the

cell where the DL

PRB Utilization above

70%, which is good to

mitigate poor SINR

issue during busy

hour

8.06 % improvement


ANR Classification

Based on neighbor relations, ANR is classified into intra-RAT ANR and

inter-RAT ANR.

Based on the methods of measuring neighboring cells, ANR is classified

into event-triggered ANR and fast ANR (also known as periodic ANR).


ANR Feature Benefit and influence

Benefit

- ANR is a self-optimization function. It automatically maintains the integrity and

effectiveness of neighbor cell lists (NCLs) and neighbor relation tables (NRTs) to

increase handover success rates and improve network performance. In addition, ANR

does not require manual intervention, which reduces the costs of network planning and

optimization.

- Event ANR

- Find the missing neighbor cells when handover measurement is reported, handover success rate

and call drop rate can be improved.

- Fast ANR

- Choose some UE to measure neighbor cells and report periodically, the neighbor cell relations can

be convergent more faster.


ANR Feature Benefit and influence

Influence

- Event ANR

- CGI report process will introduces extra delays in handovers of the UEs that meet the handover

conditions.

- Fast ANR

- In fast ANR processes, UE will report PCI periodically and read CGI when the neighbor cell is

unknown.

- In intra-frequency scene, periodical PCI reporting does not impact system performance, whereas

CGI reading interrupts UE services.

- In inter-frequency and inter-RAT scene, periodical PCI reporting impacts UE throughput, and CGI

reading interrupts UE services.


Relation between ANR and others Intra-RAT ANR

- Intra-RAT ANR needs UE to support Long DRX cycle and ANR-related

measurement. If ANR measurements need to be performed, a temporary dedicated

DRX cycle needs to be configured for the UE. During this cycle, the UE obtains the

CGIs of neighboring cells in dormancy periods.

- Intra-RAT ANR has an impact on Feature PCI Collision Detection & Self-

Optimization. When neighboring cell information changes because of intra-RAT

ANR, PCI conflict detection is triggered.

Inter-RAT ANR

- Inter-RAT ANR needs UE to support Long DRX cycle and ANR-related

measurement. If ANR measurements need to be performed, a temporary dedicated

DRX cycle needs to be configured for the UE.

Relation between ANR and others


ANR Contd (LTE Identifier)

Page 70

ECGI : E-Utran Cell Global Identifier


End of Section

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module 5-lte optimization guideline

Technology