Coverage Enhancement

8/10/2019 Coverage Enhancement

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Coverage Enhancement

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1 Nokia Siemens Networks RN20108EN14GLN0

BSSPAR1: Chapter 8Coverage Enhancement Features


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Legal Notice

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Module Objectives

Describe Extended Cell Range for CS calls

Explain parameters controlling handovers in a Extended Cell Explain the Long Reach Timeslot for Flexi BTS

Explain the 105km Super Extended cell and related parameters

Give a brief introduction to Smart Radio Concept (SRC) feature


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Extended Cell Range

One BCCH, Two TRX solution to extend cell radius to 70km

Normal and Extended area served with different TRX

BTS Type supported

Ultra CX4.1 (with EDGE capable TRX)

Flexi EP2.0

Talk Family DF7.0

Not supported by Metrosite

Activation based on TRX licence (Flexi, Ultra) or PRFILE (Talk)


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Normal region (frequency f1)

N-TRX (Parameter eTrxInd (ETRX) = N)

Extended region (frequency f2 except timeslot 0)

E-TRX (Parameter eTrxInd (ETRX) = E)

E-TRX

(Delayed receiver)

0 1 2 3 4 5 6 7

N-TRX

0 1 2 3 4 5 6 7

f1 f1 f1 f1 f1 f1 f1 f1

BCCH/

SDCCH

Not

UsedTCH TCH TCH TCH TCH TCH

TCH TCH TCH TCH TCH TCHE-RACH SDCCH

f1 f2 f2 f2 f2 f2 f2 f2

Extended cell size

Parameter radiusExtension (EXT)

Value = 1..67km radius extension of extended cell

Value = 0 ordinary cell

Extended Cell Range (Implementation)

BB Hopping cannot be used

RF hopping cannot be used onE-TRXs

One BCCH, Two TRX solution

Receiver timing delayed onETRX

Transmitter timing same onNTRX and ETRX


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Call Setup

RACH received on N-TRX IMM ASS sent on N-TRX SDCCH on N-TRX

RACH received on E-TRX IMM ASS sent on N-TRX SDCCH on E-TRX

Overlap area: RACH is recived on N-TRX and E-TRX. BSC filters the later one out


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Cell Selection

MS can camp on BCCH (NTRX) independent of the distance to the BTSRACH from MS detected on RACH or E-RACH depending on the distance to the BTS

Failure of RACH burst Wrong cell selectedReselection on the basis of the path loss criterion C1

Handover to due Distance (Normal area Extended area)

maxMSDistanceHOThreshold (MAX) 0..63 TA => MAX; handover triggered t o extended cell

minMSDistanceHOThreshold (MIN) 0..63 TA => MIN; handover triggered to normal cell

Adjacent Cell Parameter

hoTargetArea (HOTA) indicates type of target cell (normal orextended) ;indicates type of transceiver from which the BSC tries to allocate a channel (normal orextended)

0 Normal cell1 - Allocate from N-TRX

2 Allocate from E-TRX3 Allocate from TRX of the same type as source BTS

Extended Cell(Cell Selection, Handover)

Inter-BSC HO: Only values 0, 2 are allowed for HOTA.

External HO are made only towards Extended area ifLong Reach TSL (for Flexi) is NOT in use


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The Double BCCH Allocation List (Double BA List) may be needed in the extended cell

range solution because otherwise some legacy MSs do not work properly

The intra-cell handover between an N-TRX and an E-TRX is performed by using a

HANDOVER COMMAND message.

Using the Handover Command requires that the BCCH frequency of the serving cell is

included in the BCCH allocation list.

This can be achieved by using the Double BA List.

Extended CellUse of Double BA list


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Long Reach TimeslotFlexi BTS (EP2.0)

Currently BSC allocates external handovers only towards extended area ofan extended cell higher HO failures

Used to determine if the MS is located in normal or extended area (of thetargeted cell) in case of incoming external HO

Use of LRTCH BTS measures TA by scanning both LRTCH for the handover access burst BTS sends the ACCESS DELAY information to BSC

ACCESS DELAY < maxMSDistanceHOThreshold MAX: Normal cell area ACCESS DELAY >= maxMSDistanceHOThreshold MAX : Extended cell area

Intra-cell HO from LRTCH to TCH of N-TRX or TCH of E-TRX to free up LRTCH

Transmission on first LRTCHonly Reception on both LRTCH


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Long Reach TimeslotFlexi BTS (EP2.0)

TA value sent by BTS to MS cannot be greater than 63 BTS must send anadjusted value for TA if the MS is in extended area

If TA > 1.8 * EXT

TA (adj) = TA (meas) 1.8*EXT TA (adj) = TA (meas)

UL is synchronized to E-TRX UL is synchronized to N-TRX


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105km Super Extended CellIntroduction

Radius extension upto 105km for Flexi BTS (EP2.0 CD1)

BCCH serves all three cell areas

DL of E-RACH tsl not used

E-RACH of STRX overlaps with tsl 0 and 1 of BCCH (just like E-RACH ofETRX)

SDCCH defined on S-TRX

Normal and Super Extended

areas do not overlap

TA of each area measured

separately from 063


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105km Super Extended CellHandover between areas

EXTMAX

N-area: 35 km

E-area: 35 kmS-area: 35 km

SEXT SMAX

Overlap area (N/E) Overlap area (E/S)

BTS

MINSMIN

1.

2.

3.4.

1. Mobile is moving in Normal area (away from BTS), TA MAX => handover to Extended area triggers

2. Mobile is moving in Extended area (away from BTS), TA SMAX => handover to Super extended area triggers

3. Mobile is moving in Super extended area (towards BTS), TA SMIN => handover to Extended area triggers

4. Mobile is moving in Extended area (towards BTS), TA MIN => handover to Normal area triggers

TRX Level

E-TRX Type = S

BTS LevelSuper Radius Extension (SEXT)Location of inner edge of superextended area from the BTSRange: 0, 36-70

Handover ControlMS distance HOthreshold super ext cell min (SMIN)Range: 063

MS distance HOthreshold super ext cell max (SMAX)Range: 063

External handovers

Performed thru LRTCH if it is in use If not in use, HO to super extendedarea


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SRC consists of : Downlink link enhancing feature

Intelligent Downlink Diversity (IDD) Uplink enhancing features

4-way UL Diversity (4UD) Interference Rejection Combining (IRC) High gain MHA

Up and downlink features can also be implementedseparately (except for 4UD, which is used with IDD)

BTS Support: Ultrasite CX6.0, FlexiEDGE EP2.0 TRX Support: EDGE-capable TRX and EDGE

baseband units required

SRC Concept


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Improves the mobiles receiver performance by modifying the radio

channel BTS downlink performance is boosted up to 3-5 dBAll timeslots are transmitted through 2 transceivers and 2 antennas

2nd TRX transmission is delayed and phase turnedAlso BCCH carrier is sent through 2 transmitters Phase hopping is used to change phasing between adjacent bursts (todecrease correlation between a main and auxiliary transmitter) To the BSC, the main and auxiliary TRX appear as one logical TRX Mobile receives both signals as standard multipath

IDD ConceptDelay Diversity (DD) with Phase Hopping


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EDGE

Transceiver

Combined

Uplink

signal

EDGE

Transceiver

Baseband

Units Downlink

signal

RX + TX

MHAMHA

DDU

RX div.

RX div.

RX div.+ TX aux

Masthead Amplifier compensatesfeeder loss and matches front end ofthe BTS receiver optimizing sensitivity

Very efficient Interference RejectionCombining is processed for receivedsignals giving ultimate gain for diversityreception. IRC minimizes the effect ofinterfering signals in the BTS receiver.

4-way UL Diversity


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The noise between two branches are somewhat correlated, so the

best way of combining is Interference Rejection Combining (IRC). This

takes into account the correlation between interference branches andremoves ultimately the interference from the received signal.

Uplink receiver diversity can be either 2- or 4-way diversity.

In 2-way diversity the receiver combines signals from two antennas

by using Interference Rejection Combining (IRC).

4-way diversity is based on MRC combination of two 2-way IRC

diversity branches.

The signals from four antennas are fed into two separate TRX. Two

pair-wise signals are combined by IRC in respective TRX and then the

signal from the auxiliary TRX is fed into the main TRX where signals

are combined using Maximum Ratio Combining

4-way uplink diversity using IRC

followed by MRC.

2-Way/4-Way UL Receiver Diversity(IRC/MRC)


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SRC, no MHA

SRC+MHA

combiner by-pass

SRC with Mast Head Amplifier (MHA)

SRC+MHA

SRC, no MHA

combiner by-pass, no MHA

Effective cell range:Bypass,No MHA

SRC,no MHA

SRC+ MHA

DLUL

DLUL

DL UL

combiner by-passcombiner by-pass + MHADL

UL

Bypass+MHA

Balanced link defines the cell range, not only BTS TX power


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Configuring IDD in the BSC

Main and auxiliary TRXs connected to different antenna

TRX is created/added to IDD configuration during TRX commissioning

Usage of IDD and mode of IDD TRX (main/auxiliary)

4UD is defined in the BSC with the diversityUsed (RDIV) parameter:RDIV=Y (4-way RX diversity is used).

If IDD is used only for boosting the BCCH carrier, the IDD TRX has to bedefined in the BSC as preferred BCCH TRX


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STIRC is an enhancement to Interference Rejection Combining (IRC) that is implemented inNSN Flexi EDGE, EDGE UltraSite, and EDGE MetroSite BTSs

STIRC is compatible with Smart Radio Concept for EDGE (SRC). All antenna configurationsare supported. However, 4-way uplink diversity configurations provide the best performance.

Link level simulations show interference rejection performance of GMSK channel under typicalurban (TU) conditions improving on average 4 - 10 dB gain compared to IRC (for 2-way uplinkdiversity (2UD)) - The actual gain is network and configuration dependent

STIRC can be enabled per sector (BTS object)

Space Time Interference RejectionCombining (STIRC)


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In a multiple-antenna receiver, there is a strong correlation in the interference betweendifferent branches (normal and diversity) and samples for each symbol period. Usually, the

interference correlation is different from the correlation of the desired signal.

IRC is a set of diversity combining, digital signal processing methods that removesinterference by taking these cross correlations into account.

These methods can be considered as whitening the interference (there is no correlation)between the individual branches and samples of each symbol which, if done perfectly, optimizesthe performance of the receiver, in particular the bit (0/1) detection process.

STIRC works best when there is a single dominant interferer and it is best suited for urbanareas

Whitening

Whitening

Interference RejectionCombining (IRC)

Space Time InterferenceCombining STIRC

Whitening,

jointlyestimated

STIRC & IRC


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STIRC feature control

STIRCSTIRC is

disabled

(N) (0)

Defines whether the STIRC feature is used

in the BTS.

Valid only for Nokia UltraSite, Nokia

MetroSite and Nokia Flexi EDGE Site types.

STIRC is disabled

(N) (0), STIRC is

enabled (Y) (1)

stircEnabledBTS

BSC - MML

Name

Default

value

DescriptionRange And StepAbbreviated

Name

MO

Class

Licence based feature: Capacity licence based on number ofSTIRC enabled TRXs in the BSC

STIRC activation on BTS level

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Coverage Enhancement