nokia cell deployment

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1 ©NOKIA WCDMA_overview.PPT/ 5.4.2002 Kari Heiska, TLI361-WCDMA radioverkkosuunnittelu - luentosarja Jyvaskylän yliopistossa(Reproduced by permission of John Wiley & Sons Limited)

Cell Deployment in WCDMAKari Heiska 5.4.2002


Contents

• Roll-out• Greenfield operator case• Operator running the GSM system

• Hierarchical Cell Structures (HCS)• Network Operation• Case Study

• Conclusions




Roll-Out• =Process in order to generate an operations network

• Provided services• Evolution of the services and the network

• Usage of Carriers• Usage of hierarchical Cell Structures• Provisioning of Indoor Coverage and Services

• Indoor Coverage and Services

• The extensions should be planned to have as small changes to thecurrent networkstructure as possible

• Roll-out for the Greenfield operator

Constructionwork

Packet Core

NW planning

Commissioning

TransmissionrequirementsTraffic and Service

Requirements

RNP Site Acquisition Dimensioning

NW parameters

Test & Performance

Monitoring & Reporting

• Roll-out for the GSM operator• GSM sites ready• Location of hot-spots known• IF-HO can be used for the traffic balancing• WCDMA only for the city centers


HCS in WCDMA Networks

• Hierarchical cell Structures means the usage of macro, micro andpiconetwork layers

• It can also mean that the mobile is able to connect any of theselayersat the same geographical location

• In principle one carrier =one network layer

• The deployment of HCS is determined by the amount of WCDMAcarriers. With 3 carriers it is possible to build a full HCS

• With 4 carriers more flexibility can be achieved. For example 2frequencies for macro, 1 for micro and 1 for pico

• The handover between carriers with IF-HO




Case study

• Npsw simulations have been performed in order to examine the frequency re-use inmicro-macro network

• Micro layer: 31 cells (sectors)

• Macro layer: 18 cells (six 3-sector sites)

• Independent planning of micro and macro layer

• Both networks provide continuous coverage (=mature development phase)

• Macro layer can understood to be consisted of umbrella cells which serve high speedMS as well as fills the coverage holes of micro layer

• The propagation data for micro and macro has been computed with 3D Ray-Tracingprogram

• In micro/macro simulations all the mobiles were initially connected to micro layer(f1) and if not heard moved to macro layer (IF-HO) if macros CPICH Ec/I0 wassufficient

• The performance of the WCDMA network where macro was reused in micro and viceversa was then compared to the reference case with macro and micro in separatelayers


Case study

• Continuous macro f2

• Continuous micro f1

f2

f1 f1 f1 f1

f1,f2

f1 f1 f1 f1

f2

f1,f2 f1,f2 f1,f2 f1,f2

f2

f1 f1 f1 f1

• Continuous macro f1, f2

• Continuous micro f1


• Continuous micro f1, f2


• Continuous micro f1 andselected cells for f2

Hierarchical Cell Structures Used in t he Study




Case study - micro and macrocell networks in

Helsinki city center

31 microcells

18 (=six 3-sector) macrocells

Micro and macrolayers planned

independently ofeach other

Mobiles initiallyconnected to microf1, if it can be heard


Macro Micro

BS TX Max Power 43 dBm 37 dBm

TX max power per link 40 dBm 34 dBm

TX min power per link 15 dBm 9 dBm

CPICH power 30 dBm 24 dBm

Other common channel powers 30 dBm 24 dBm

CPICHtoRefRabOffset 5.5 dB 5.5 dB

Cable losses 2 dB 2 dB

MHA gain 0 dB 0 dB

Channel Two equal taps Two equal taps

SHO window 3 dB 3 dB

Max load own 0.6 0.8

Max total load 0.6 0.8

BS antenna type and gain 65 deg, 16 dBi 60 deg, 12 dBi

Average antenna height 32 m 10 m

BS noise figure 5 dB 5 dB

Base station parametersMax power limit

Link power limit

Uplink load limit

Pilot power(coverage) limit

No hard blocking, i.e. code limit considered




Parameters for mobilesMax TX power 21 dBm

Min TX power -50 dBm

Service in use (UL, DL) 12.2 kbit/s

Mobile speed 3 km/h

MS noise figure 8 dB

Other simulation parametersNumber of allowed IFHOs 2

UL load reduction Remove mobiles randomly

BS TX power reduction Remove mobiles randomly

Hard blocking (code limit) Not used

Number of snapshots in averaging 3

Max power limit


Carrier reuse cases

Microcell Macrocell (a) Micro f1, macro f2 (reference case)

Maximum transmission power 37 dBm 43 dBm

CPICH power 24 dBm 30 dBm

Power for other common channels 24 dBm 30 dBm

(b) Micro f1, macro f1+f2

Maximum transmission power 37 dBm 40 dBm (per carrier)

CPICH power 24 dBm 27 dBm (per carrier)Power for other common chann els 2 4 dBm 27 d Bm (per carri er )

(c) Micro f1+f2, macro f2

Maximum tr ansmission power 34 dBm (per carrier ) 43 dBm

CPICH power 24 dBm (per carrier) 30 dBm

Power for other common channels 21 dBm (per carrier) 30 dBm

(d) Micro f1+f2 on selected cells, macro f2

Maximum tr ansmission power 37 dBm (per carrier ) 43 dBm

CPICH power 24 dBm (per carrier) 30 dBm

Power for other common channels 24 dBm (per carrier) 30 dBm

CPICH powerdifference 3 dB,

BS power splitted


BS power splitted


LPA added




Case study: Results

• 110 users per micro sector with over 95% coverage probability

• Re-using micro with macro (Micro f1, Macro f1+f2)• Does not bring any capacity gain• The high interference from macro MSs to micro BSs on frequency f1 The micro

capacity is 50%-65% of the users in the reference case• The uplink loading in microcells reaches to its maximum because of macro cell

users• The maximum Tx power is reached in many macrocells, as well• Increased Soft Handover Overhead (50%-70% in macros)

• Re-using macro with micro (Micro f1+f2, Macro f2)• 10% more capacity than in the reference case

• When sharing the micro cell increase the outage due to DL power in microcells• No interference from macro to micro. The mobiles are first at micro f1 and then

handed over to macro f2 or micro f2, whichever is stronger (pilot power). Now theloading of f2 is lower than the loading of f1 and therefore the interference is alsolower,


Case study: Results

• Re-using macro with micro (Micro f1+f2 (selected cells), Macro f2)• In the previous solution the capacity of micro f2 was not utilized in maximum• The common channel power of half-loaded microcells will, however, increase the

total DL interference• Therefore it is maybe better to utilize micro f2 only in those case when needed.• The second carrier were allocated only for those cells which would need it. Those

were the cells which were relatively far away from the macro cells




Service probability

~20% capacityincrease with macrocarrier on selected

microcells

No improvements byreusing micro carrier

on macrocells


Reasons for not serving mobiles

Power split between micro carriersLPA added when reusing

macrocarrier on microcells

Macrocelllink power




Number of served users

Case a – micro f1, macro f2Case b – micro f1, macro f1+f2,

CPICH power difference 3 dBCase c– micro f1+f2, macro f2,CPICH power difference 6 dB


Selecting microcells for another carrierCase (d)

Only some microcellsbenefit from f2, andcollect traffic with it

Problem with microcell12: high loading withfew users in cell 12




Dominance areas based on highest pilot in f2

macro carrier f2 reused on all microcells, pilot power difference 6 dB

7 and 12 (arrows):diminished

dominance areasdue to nearbymacrocells

Circulatedmicrocells can

maintainreasonable

dominance areas(cf. previous slide)


Conclusions

• Best capacity improvements by reusing macro carrier on selected microcells, which are (a)highly loaded and (b) far enough from macrocells

• if f2 in microcells cannot collect traffic, it generates only DLinterference, as it still has topower for CPICH and other common channels (may lead to pilot pollution)

• ~20% of microcells in this study were suitable for another reused carrier• capacity increase 15-20% (at 95% service probability network operating point)

• If macro carrier is reused on microcells, it's worthwhile to double the BS TX power• microcells limited by BS TX power rather than uplink interference• adding LPA more expensive than power sharing between carriers, but in that way the

microcell capacity can be best exploited• Micro carrier reuse on macrocells does not bring about any capacity improvements

• good capacity of microlayer is wasted in high interference levels and soft handoveroverheads

• Microcells close to macrocells cannot reuse macrocarrier• higher macro pilot power disables it• if microcell is highly loaded, it is better to decrease the micro pilot power if adequate pilot

coverage can still be maintaned• smaller dominance area, less users

nokia cell deployment

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