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Etisalat Academy Anand Alexander of 25

WCDMA BASE STATION

PLANNING

Anand Alexander

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By the end of this session, the participants will be able to:

• Get familiar with the principles for antenna selection and installation

• Identify the causes of pilot pollution and identify related solutions

• Describe how multiple systems are co-sited

Objectives

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General Process for SiteSelection

Step 1: The network planning engineer generates a list of

ideal sites

Step 2: The survey engineer makes selection and survey

according to the planned sitesStep 3: For a complex area, make a propagation test to

check whether the coverage is OK

Step 4: After the site is selected, contact the owner or

landowner to check whether the site can be purchased or

leased

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Purpose of Site Selection

• Selecting a site that can cover the target area and has the lowest

interference to others

– The selected site should be possibly closest to the traffic hotspot

– The antenna height depends on the type of the area where the

site is located

– The key point is how to control the interference

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How to Evaluate a CandidateSite

WirelessWireless

environmentenvironment

Planning resultPlanning result

Power supplyPower supply

Engineering feasibilityEngineering feasibility

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Site Survey Flow

Wireless

network plan

Site list

2G site? New site (prefix:

NewSite)?

Output SearchRings

Obtaincandidate sites

Site survey

Site

conditionsdetermined?

Site surveyreport

Noise testNoise test

report

Site

requirement

met?

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Antenna Feeder System

Jumper

Grounding clip

Feeder

Grounding clip

Grounding clip

Jumper

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TMA

Triplex TMA

TMA feed

bias tee

Transmitter filter

Receiver

filter

Bypass

LNAReceiver

filter

Antenna

DC

Note B

• In general, the TMA and the antenna are connected through one

1/2“ jumper of 2m-3m long

• A TMA improves the sensitivity of the system and increases the

upstream coverage of the system.

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Feeder

• Common feeder types:

– 1/2", 7/8", 5/4“

• Principles for feeder selection

– If the feeder is longer than 50m, a 5/4“ feeder is required. If the feeder is

shorter than 50m, a 7/8” feeder is required. A 1/2“ feeder is used as the jumper between the antenna and feeder or the one between the feeder

and the BS top

• Loss of 2GHz feeder

– Feeder type Manufacturer Loss (100m)

– LDF5-50A (7/8") ANDREW 6.46 dB – LDF6-50 (5/4") ANDREW 4.77 dB

– FSJ4-50B (1/2") 17.7 dB

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Antenna Type Selection

• Antenna type selection is important to

the network quality

• According to the terrain or trafficdistribution, the antenna environment

falls into the following types:

– Urban area, suburb, rural area, road,

indoor, and so on

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Antenna Selection for UrbanArea

• Directional antenna

– ±45º dual polarization

– Horizontal beam width: 65º

– Gain: 15 dBi – Preset 6º electrical tilt adjustable electrical tilt

+ 0º –15º mechanical tilt

– Upper side-lobe suppression + null filling

– Front-to-back ratio: ≥ 25dB

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Antenna Selection for RuralArea

• Environment characteristics inrural area

– Sparse BS location

– Low traffic

– Wide coverage required


– Vertical polarization – Horizontal beam width: 90º

– Gain: 18 dBi

– No preset tilt

• Omni-antenna

– Vertical polarization

– Gain: 11 dBi

– No preset tilt

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Antenna Selection for Suburb

• In selecting an antenna for a suburb, thesuggestions on the antenna selection for urban area or rural area can bereferenced

• An omni antenna is not recommended, in

order to facilitate smooth upgrade in thefuture

• In a suburb, if the antenna uses a tiltangle, the tilt angle should be small

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Antenna Selection for Road


– Horizontal beam width: 30º; gain: 21 dBi

– Vertical polarization; no preset tilt

• "8"-shaped antenna

– Bidirectional horizontal beam width: 70º; gain: 14 dBi


• Heart-shaped antenna

– Horizontal beam width: 210º; gain: 12 dBi


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Selection of an Indoor Antenna

• Omni-antenna

– Vertical polarization; gain: 2 dBi

– Horizontal beam width: 360º; vertical beam width: 90º

• Directional plate antenna

– Vertical polarization; gain: 7 dBi


• Log periodic antenna (a kind of wideband antenna)

– Vertical polarization; gain: 11.5 dBi


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Principles for Antenna HeightDesign

• For a flat urban area, the effective height of an antenna is usually

about 25m

• For a suburb or rural area, the height of the antenna can be about

40m

• A too high antenna may lower the coverage level beside the antenna

(a blind zone under the tower), which is more severe for an omni-

antenna

• A too high antenna may result in cross coverage, increase the

interference, and affect the network performance

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Principles for AntennaAzimuth Design

• The central lobe of the antenna should face the high-traffic area to improve

the signal strength and call quality

• For the urban area, the overlapping coverage ratio of the adjacent cells

should not exceed 10%

• For the suburb or rural area, the separation angle between the antenna

directions of the adjacent cells should be not lower than 90º

• For the high-density urban area, the central lobe of the antenna should not

face a straight street

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Principles for Antenna TiltDesign

• The antenna tilt technology can effectively control the coverage and

reduce the intra-system interference

• The antenna tilt angle should be determined according to the situation.

It should reduce the interference between the cells with the same

frequency and meet the coverage requirement

• In designing the antenna tilt angle, factors such as transmit power of

BS, antenna height, cell coverage, and wireless propagation

environment should be considered

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Requirement on InstallingSpace Diversity

• In case of space diversity, the distance between two receive antennas

should be 12 – 18λ, 1λ= 0.15m (2GHz)

• The effect of the vertical diversity is the same as that of the horizontal

diversity only when the vertical diversity distance is 5 –6 times the

horizontal diversity distance

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PILOT POLLUTION

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Concept of Pilot Pollution

• Concept of pilot pollution

– Pilot pollution means that there are too

many strong pilots within the coverage,

but none of the pilots is dominant

• Criteria of pilot pollution – There are more than 3 pilots with

Ec > -95 dBm

– The level difference between the

strongest pilot and the fourth strongest

pilot is < 5 dB

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Effect of Pilot Pollution

• Pilot pollution is specific to the CDMA system CDMA and greatly

affects the network performance

• Effect of pilot pollution

– High BLER

– Low system capacity – High call drop rate due to frequent handover

– Low access success rate due to no dominant cell

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Causes of Pilot Pollution

• The causes of the pilot pollution includes:

– Unreasonable cell layout

– Too high site or antenna

– Unreasonable azimuth or tilt angle of an antenna

– Effect of the back lobe of an antenna

– Effect of the ambient environment of the coverage

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Ways to Reduce PilotPollution

• An area with pilot Pollution can be predicted in the planning

simulation

– Optimize the planned scheme to avoid the pilot Pollution

• Optimal solution – excellent system design

– Proper site – Proper azimuth and tilt angle of antennas

– Proper transmit power and power ratio of sites

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2G/3G CO-SITING

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2G/3G Co-located Site

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Interference from Other System

1880~1920MHz,

2010~2025 MHz

TDD mode

TD-SCDMA

2110 ~ 2170 MHz

1920 ~ 1980 MHz

WCDMA

935 ~ 960 MHz

890 ~ 915 MHz

GSM 900

1900 MHz ~

1915 MHz

TDD mode

PDC (PHS)

1805 ~ 1880 MHzDownlink

1710 ~ 1785 MHzUplink

GSM (DCS) 1800

1880~1920MHz,

2010~2025 MHz

TDD mode

TD-SCDMA

2110 ~ 2170 MHz

1920 ~ 1980 MHz

WCDMA

935 ~ 960 MHz

890 ~ 915 MHz

GSM 900

1900 MHz ~

1915 MHz

TDD mode

PDC (PHS)

1805 ~ 1880 MHzDownlink

1710 ~ 1785 MHzUplink

GSM (DCS) 1800

GSM 900 DCS1800 Tx PDC (PHS) WCDMATD-SCDMA

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Interference from Other System

•GSM1800 BTS can

have up to – 80 dBm/

0.4 MHz spurious

emissions at the

antenna connector

•Thermal noise floor for WCDMA = -108

dBm

=> 28 dB [-108 dBm -

(-80 dBm) ] isolation

needed between

GSM1800 and

WCDMA

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Harmonic Distortion

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M Distortion from GSM1800DL to WCDMA UL

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2G/3G Isolation Methods

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Planning Rules in Co-Siting

Isolation requirement: 50 dB

GSM-WCDMA co-sitingis possible if antenna isolation requirement is

fulfilled

• By proper antenna placement

• Minimum Horizontal distance (~0.3 m)

• Minimum Vertical distance (0.25 m)

Di-or triplexeris needed in case feeder and antenna is shared between

different systemsTighter filtering is needed in Antenna line of Non-compliant GSM BTS

to avoid the TX power interference to WCDMA Rx

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Co-transmission

BTS

NodeB

E1/SDH(Abis)

Nx64kbps

BTS

NodeBE1/SDH(Iub)

E1

BTS

NodeBE1/SDH(Iub)

E1

• At the early stage of WCDMA construction, GSM provides E1/SDHtransmission resources for the WCDMA

• At the mature stage of the WCDMA, the required capacity of the

WCDMA system is high, and WCDMA can provide transmission

channels for the GSM

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Co-located AuxiliaryEquipment

• Equipment room – The NodeB is configured with only one cabinet, so only a little

space is required

– The NodeB is heavy, so the bearing capacity of the equipment

room should be considered

• Power supply system

– The 3G BS can use the legacy DC power and storage batteries in

the equipment room

• Grounding system

– The grounding requirement of the 3G BS is similar to that of the

BS of any other wireless system

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Co-located AuxiliaryEquipment

• Cable rack

– The legacy indoor and outdoor cable racks are recommended. If

necessary, cable racks can be added

• Air conditioner

– The NodeB causes much heat, so it is necessary to reconsider the capability of the air conditioners in case of co-located

equipment room

• Co-located feeder window

– In general, there are several holes in the feeder window in the

equipment room. They can be shared by two sets of systems withgeneral capacity configuration

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Question and Answers

Discussion

chapter_6 s

Documents

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