04 OWJ100103 WCDMA Base Station System Planning (With Comment) ISSUE 1

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WCDMA BaseStation SystemPlanning


Objectives� Upon completion of this course, you will be able to:

� Familiarize the principles for BS site selection

� Familiarize the principles for antenna selection and installation

� Know the causes of pilot pollution and the related solutions

� Know the notes for the co-existence of multiple systems


Contents1. Site Selection

2. Antenna Feeder System Design

3. Pilot Pollution

4. Multi-system Coexistence Planning



1.1 Principles for Site Selection

1.2 Site Evaluation

1.3 Site Survey


General Process for Site Selection� 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 sites

� Step 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


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


Principles for Site Selection� The sites should be laid out according to the mesh, with the

allowed deviation not larger than 1/4 of the BS radius

� The legacy sites are preferred if the BS layout is not

affected

� The position of a new site should be a place with convenient

traffic and power supply

� At the early stage of the network construction, the most

important areas should be provided with good coverage


Principles for Site Selection� When the site is in a mountainous area, near lake, sea, or

building with glass wall, the effect of signal reflection should

be considered

� When the site is in urban, we can use the height difference

of buildings to form network hierarchy


Principles for Site Selection� In general, a site should not be built on a high mountain

beside a city or in a suburb

� The site should not be built beside a broadcasting station,

radar station, or other interference source

� The site should be far away from a hurst in order to avoid

fast fading of signal

� The coverage edge of the site should not be within the high

traffic density area


Site Selection in High-densityUrban Area� The antenna should be lower than the average height of

buildings in the area

� The antenna should not be blocked by any nearby building

� The antenna should be installed at the edge of the building


Site Selection in Urban Area� The antenna should be slightly higher than the average

building in the area

� Line-of-sight links may exist in the most portion of the area

covered by the BS


Site Selection in Suburb� The antenna should be 5m–10m higher than the average


� Line-of-sight links should be available in the most portion of

the area covered by the BS

� Only some line-of-sight links cross the cell border


Site Selection in Rural Area or onRoad� The antenna should be 10m-20m higher than the average


� Good line-of-sight links are available in each direction

� If the site is close to a town, the azimuth and tilt angle of the

antenna should be adjusted for controlling the interference




1.2 Site Evaluation

1.3 Site Survey


How to Evaluate a Candidate Site

WirelessWirelessenvironmentenvironment

TransmissionTransmissionresourcesresources

Planning resultPlanning result

Power supplyPower supply

Engineering feasibilityEngineering feasibility


Wireless Environment

Does thecandidate site well

cover the targetarea?

Is there any RFinterference onthe candidate

site?

Is there any apparentbarrier found in thephotos or the map?

� The RF engineer should check the following on each

candidate site and the nearby sites:


Transmission Resources

Is the optical fiberor E1 transmission

available? Is any line-of-sight link to the

microwavenode available?

� The selection of a candidate site is often affected by the

transmission planning:


Engineering Feasibility� The new site should facilitate the use of vehicle and lifting

equipment

� Requirements on the building

� A safe and convenient passage

� The moving of the equipment to the site room through a lift or a

goods elevator in the building should be easy


Power Supply� Proper power supply should be available at the site

� The total power consumption of the main equipment and

auxiliary equipment should be considered




1.2 Site Evaluation

1.3 Site Survey


Meaning of Site Survey� The results of the site survey may affect the quality and

smooth construction of the whole project

� The reasonableness of the site is related to not only the

coverage of the site but also the coverage of the peripheral

sites

� Objectives:

� Providing a detailed construction scheme for the network

deployment to guide equipment preparation, engineering

construction, installation and commissioning


Tasks of Site Survey� The survey engineer makes a detailed survey according to

the plan made at the site selection stage

� Survey items

� BS location

� Equipment room construction

� Antenna selection

� Equipment installation location

� After completing the survey, the survey engineer submits a

survey report


Site Survey FlowWireless

network plan

Site list

2G site? New site (prefix:NewSite)?

Output SearchRings

Obtaincandidate sites

Site surveySite

conditionsdetermined?

Site surveyreport

Noise testNoise test

reportSite

requirementmet?


Preparation: gathering information

� Familiarize the project profile, and collect

project data, including:

� Engineering document

� Local map

� BS survey table

� Contracted configuration list

� Contract feedback table

� Information about the legacy network


Preparation: tools required� Before the site survey, make sure that

the following tools are available:

� GPS receiver

� Digital camera

� Compass

� Telescope

� Laser range finder

� Laptop

� Tape measure

� Map


Detailed Survey

� Measuring the longitude, latitude, and height of the site

� Use the GPS receiver to measure the longitude andlatitude of the site

� Use the laser range finder to measure the relative heightand altitude of the site

� If no laser range finder is available, use a GPS receiverto measure the height through air pressure (the errordepends on the weather), or estimate the height


Detailed Survey

� Gathering information about the antenna installationplatform

� Draw the schematic diagram of the antenna installationplatform, and mark the installation location of all theequipment on the platform

� After the antenna installation location is determined, markthe related information (antenna installation location,installation mode, pole length, and so on) on the schematicdiagram


Detailed Survey� Measuring the propagation environment

� Write down the height of the barrier in each direction and the

distance between the barrier and the site

� Check whether some antennas of any other communication

equipment exist nearby the site

� If any, write down the location (direction and distance), band,

transmit power, height, azimuth, tilt angle of the antenna


Summary� This chapter covers the following:

� The process for site selection and principles for site selection

� The preparations and process for site survey




3. Pilot Pollution



Antenna Feeder System

Jumper

Grounding clip

Feeder

Grounding clip

Grounding clip

Jumper


TMA� TMA (Tower Mounted Amplifier) is installed on a tower. It is close to the

antenna. In general, the TMA and the antenna are connected through one1/2“ jumper of 2m-3m long

� A TMA improves the sensitivity of the system and increases the upstreamcoverage of the system. It also lowers the transmit power of an MS, reducesthe interference noise inside the system, and improves the call quality

Triplex TMA

TMA feedbias tee

Transmitter filter

Receiverfilter

Bypass

LNA Receiverfilter

Antenna

DC

Note B


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 isused as the jumper between the antenna and feeder or the onebetween 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


Classification of Antennas� By radiation direction

� Directional antenna and omni-antenna

� By appearance

� Plate antenna, mushroom antenna, whip antenna

� By polarization mode

� Single polarization antenna and by-polarization antenna


Antenna Type Selection� Antenna type selection is important

to the network quality

� According to the terrain or trafficdistribution, the antennaenvironment falls into the followingtypes:� Urban area, suburb, rural area, road,

indoor, and so on Urban areaUrban area IndoorIndoor

SuburbSuburb

RoadRoad Rural areaRural area


Antenna Selection for Urban Area

� Directional antenna� ±45º dual polarization� Horizontal beam width: 65º

� Gain: 15 dBi

� Preset 6º electrical tilt or 0º– 0º adjustableelectrical tilt + 0º–15º adjustable mechanical tilt

� Upper side-lobe suppression + null filling

� Front-to-back ratio: ≥ 25dB


Antenna Selection for Rural Area� Environment characteristics in rural area

� Sparse BS location� Low traffic� Wide coverage required

� Directional antenna� Vertical polarization� Horizontal beam width: 90º� Gain: 18 dBi� No preset tilt

� Omni-antenna� Vertical polarization� Gain: 11 dBi� No preset tilt


Antenna Selection for Suburb

� In selecting an antenna for a suburb, the suggestions onthe antenna selection for urban area or rural area can bereferenced

� An omni antenna is not recommended, in order to facilitatesmooth upgrade in the future

� In a suburb, if the antenna uses a tilt angle, the tilt angleshould be small


Antenna Selection for Road

� Directional antenna� 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



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



Principles for Antenna Height Design

� For a flat urban area, the effective height of an antenna isusually about 25m

� For a suburb or rural area, the height of the antenna canbe about 40m

� A too high antenna may lower the coverage level besidethe antenna (a blind zone under the tower), which is moresevere for an omni-antenna

� A too high antenna may result in cross coverage, increasethe interference, and affect the network performance


Principles for Antenna Azimuth 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 theadjacent cells should not exceed 10%

� For the suburb or rural area, the separation anglebetween the antenna directions of the adjacent cellsshould be not lower than 90º

� For the high-density urban area, the central lobe of theantenna should not face a straight street


Principles for Antenna Tilt Design

� The antenna tilt technology can effectively control thecoverage and reduce the intra-system interference

� The antenna tilt angle should be determined according tothe situation. It should reduce the interference between thecells with the same frequency and meet the coveragerequirement

� In designing the antenna tilt angle, factors such as transmitpower of BS, antenna height, cell coverage, and wirelesspropagation environment should be considered


Implementation of Antenna Tilt� The antenna tilt beam can employ the fixed electrical tilt, mechanical

tilt, or both� The fixed electrical tilt angle is related to the antenna type

� The mechanical tilt angle is adjustable and usually does not exceed 15º

� Electrical tilt and mechanical tilt generate different surface radiation. Ifthe tilt angle is small, the difference is not distinct. If the tilt angle islarge, the difference is distinct

fixed electrical tilt mechanical tilt


Antenna Installation Environment� The installation environment includes the ambient environment of the

antenna and that of the BS� For the ambient environment of the antenna, the antenna isolation and the effect

of the tower and rooftop on the antenna should be considered

� For the ambient environment of the BS, the effect of the high buildings within the500m on the wireless signal propagation should be considered

-60 relative toantenna azimuth

-60 relative toantenna azimuth

+60

+60 relative toantenna azimuth

> 30

<=30 Antenna azimuth

Antenna azimuth

WallWall


Antenna Installation Environment� Note: An antenna should be kept away from barriers, otherwise,

a large shadow area may appear� For example, if the antenna is installed on a rooftop, it should be

installed at the edge of the rooftop, otherwise the wireless signal maybe blocked by the rooftop

2mmore than 10m

1m2m~10m

0.5m0m~2m

h

the distance betweenthe bottom of antenna

and flat

D

the distance betweenantenna and the edge of

the building


Requirement on Installing SpaceDiversity

� In case of space diversity, the distance between two receiveantennas should be 12 – 18λ, (1λ= 0.15m (2GHz))

� The effect of the vertical diversity is the same as that of thehorizontal diversity only when the vertical diversity distanceis 5–6 times the horizontal diversity distance

space diversity distance(2--3m for wcdma)

actual installed distance

Note:



� The principles for designing antenna height, tilt, azimuth indifference situation




3. Pilot Pollution



Concept of Pilot Pollution

� Concept of pilot pollution� Pilot pollution means that there are

too many strong pilots within thecoverage, but none of the pilots isdominant

� Criteria of pilot pollution� There are more than 3 pilots with Ec

> -95 dBm

� The level difference between thestrongest pilot and the fourthstrongest pilot is < 5 dB


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


Detection of Pilot Pollution

Area with pilotArea with pilotpollutionpollution

Good

Not GoodPilot pollutionPilot pollution


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


Unreasonable cell layout

� The distances among the Site A, B and C are not balanced, and the location

relation between the Sites is distinctly different from an equilateral triangle

Site A

Site C

Site B


Too high site or antenna

� The antennas of A and C are too high, so it is hard to control overshooting

Pilot pollutionPilot pollution


Unreasonable azimuth of anantenna

� The antenna azimuth of the sector with scramble of 100 is unreasonable


Unreasonable tilt angle of anantenna

� The too small antenna tilt angle results in overshooting


Effect of the back lobe of an antenna

� Front-to-back ratio of the antenna does not meet the requirement,

so the signal of the back lobe leaks


The Ways to Reduce Pilot Pollution� 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



� Concept, criteria, causes, and the ways to reduce pilot pollution




3. Pilot Pollution



2G/3G Co-located Site

Siteroom

3G

SiteCo-

feederCo-

transmission

Battery

PowerAir

conditioner

2G

Site


2G/3G Co-located Site� The GSM and CDMA site resources in the legacy system

should be fully referenced and used in the 3G network

� Site co-location helps to reduce the number of sites and make

full use of resources such as equipment, tower, and rooftop,

thus reducing site cost and improving the deployment

efficiency of 3G network

� Site co-location minimizes the inter-system interference and

makes the interference controllable


Contents4. Multi-system Coexistence

4.1 Co-located Tower, Antenna Pole

4.2 Co-feeder

4.3 Others


Co-located Tower, Antenna Pole

� If the WCDMA and GSM900/DCS1800 share the

tower, antenna, or rooftop, the major problem lies

in the inter-system interference

� Spurious radiation

� Inter-modulation

� Receiver block

� Other EMC problems


Interference between WCDMA andothers

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


Isolation requirement and solutions

d>0.2m

d>2m

65dB

GSM (DCS) 1800

41dB

TD-SCDMAPDC (PHS)

89dB36dBWCDMA

GSM 900




4.2 Co-feeder

4.3 Others


Co-feeder� Advantages of co-feeder

� The legacy feeder is used, simplified the construction andreduces the cost

� If the antenna isolation does not meet the requirement, co-feeder + multiplexer can be used

duplexerduplexerfilterfilter


Co-feeder� Disadvantages of co-feeder

� The multiplexing filters of the new system are connected with

those of the legacy system, which will affects the legacy

network

� It is impossible to implement inter-system isolation through

antenna isolation. If the requirement on the inter-system

isolation is high, additional filters are needed between the

multiplexing filter and the BS


Co-feeder

Isolation < 50dB

WCDMAGSM

TMA

GSM WCDMA

Duplex filter

Co-located feeder

Duplex filter

Isolation >50dB

WCDMAGSM

GSM WCDMA

TMA

Duplex filter

Co-located feeder

Filter (A)

Duplex filter




4.2 Co-feeder

4.3 Others


Co-transmission: Fractional ATM

BTS

NodeB

E1/SDH(Abis)

Nx64kbps

� At the early stage of WCDMA construction, GSM providesE1/SDH transmission resources for the WCDMA


Co-transmission: CES

BTS

NodeBE1/SDH(Iub)

E1

� At the mature stage of the WCDMA construction, the

required capacity of the WCDMA system is high, and

WCDMA can provide transmission channels for the GSM


Co-located Auxiliary Equipment� Equipment room

� The NodeB is configured with only one cabinet, so only a littlespace is required

� The NodeB is heavy, so the bearing capacity of the equipmentroom should be considered

� Power supply system

� The 3G BS can use the legacy DC power and storage batteriesin the equipment room

� Grounding system

� The grounding requirement of the 3G BS is similar to that ofthe BS of any other wireless system


Co-located Auxiliary Equipment� Cable rack

� The legacy indoor and outdoor cable racks (troughs) are

recommended. If necessary, cable racks (troughs) 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 12 holes in the feeder window in the equipment

room. They can be shared by two sets of systems with general

capacity configuration



� the notes for coexistence of multiple systems, including majorinterference, isolation requirement, co-located site, and so on

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04 OWJ100103 WCDMA Base Station System Planning (With Comment) ISSUE 1

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