BTS Layout and Site Selection ISSUE1.0_3.ppt

8/14/2019 BTS Layout and Site Selection ISSUE1.0_3.ppt

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Thank You

BTS Layout and Site SelectionISSUE1.0

Wireless Product Course Development Room


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Study Objective

Learn the contents of BTS

survey, work procedures andrelevant documentations

After the study of this course,you should

Master the conception of siteselection, principle of site selection

and factors affecting network coverage

Method of antenna and feeder selection

Master all related documentation with

site survey


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Chapter 1 Survey

Section 1 Brief Introduction

to Services


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BTS Survey Location

BTS survey is an important

step in the network planning


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The determination of the preliminary BTS layout is the

first job of BTS survey.

The BTS layout includes:

a. Estimate the number of BTSs required according to the capacity

prediction, traffic distribution and coverage requirements

b. Determine the theoretical BTS location

c. Assign values to relevant parameters of BTS (network hierarchy,

transmit power, antenna feeder system, antenna type, antenna height,

antenna angle, antenna downtilt, etc.)

To be vivid, set up a good coverage radio environment

Ideal BTS Layout


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Site Selection

Select an ideal site and confirm it.

Once the site is finalized, a detailed BTS

survey plan should be prepared.


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The BTS survey is an environmental survey of BTS after

the BTS layout is finalized, including light measurement,

spectrum measurement and site survey.

Sight measurement

Building environment and natural environment around BTS

Spectrum measurement

Electromagnetic background environment

Site survey

Installation condition of antenna and equipment

Power supply and transmission supply

Detailed Survey


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Chapter 2 Survey preparations

Section 1 Preparations


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Get familiar with the engineering survey and

collect data related to the project, including

Engineering document

Background information

Current network status

Local map

Contracted configuration list

BTS survey table in latest network planning

Project Documentation


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Prepare tools and confirm the tools are workablebefore setting about the survey.

Digital camera

GPS satellite receiver Compass

Tape

Telescope

Portable computer

YBT250

Tool Preparation


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Coordination meeting for survey preparationBefore a formal survey, call all relevant personnel together to

hold a coordination meeting for the survey preparations, mainly

including

Electromagnetic background, an electromagnetic

background test if necessary

Finalization of surveyors and cooperators

Vehicle and equipment preparations

Preparation of survey plan and finalization of survey route

Preliminary solution for transmission and power supply

Coordination Meeting for Survey Preparations


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Question

There are too many sites to be

surveyed, so what preparations can

accomplish the survey with a high

quality and a high efficiency?


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Part 1 content

Chapter 1 Survey concept

Chapter 2 survey preparation

Chapter 2 BTS Layout and Site Selection


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Section 1 Coverage

Planning

Section 2 Cell Layout and

Site Selection


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Factors Affecting Coverage

Customer requirements

QoS (quality of service) index and coverage area Equipment

Output power, receiver sensitivity, loss and gain of relevant

parts

EnvironmentThe radio wave will have different propagation characteristics in

different environments

Technical system

Soft handoff gain and system load (for CDMA and WCDMA),diversity receiving

Service

Service type, information rate


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Section 1 Coverage

Planning

Section 2 Cell Layout and

Site Selection



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Start the site selection after the preparations are all

done and the coverage requirement is obtained.During the site selection, the following information

should be considered:

Original network status

Population distribution and local customs

City structure and town distribution

Major streets and traffic volume

Natural environment, such as mountain, lake,

river and coastline

Long-term development trend

Conception of Site Selection


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Principle of BTS site selection

Population distribution

Traffic distribution

Subscriber tendencyEnvironment around BTS

Signal propagation quality

Select areas where traffic ishigh and subscribers are

densely populated

Be careful not to select high

mountains, radar, radio station,

forest, or power plant

Conception of Site Selection


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Weak Signal Area and Blind Area

The distance between BTSs is too large

The system load is too heavy

Obstructions

Poor indoor coverage

Effects of Unreasonable Cell Layout on

Network Performance

Effects of Unreasonable Cell Layout on Network


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Too large overlap coverage area

If there are too many BTSs, the distance between BTSs will be

short and the forward power distribution will be inappropriate.

A improper control of the cell coverage will result in a large overlap

area between BTSs, and eventually

a high soft handoff ratio

pilot pollution

FER increase, or even call drop


Performance



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Cross-cell Coverage

1. When the BTS is set up on a mountain or extremely high

building in an urban or suburb area, the cross-cell coverage

may occur if it is not well controlled.2. When the site and the direction of the main beam of the

antenna feeder are finalized, cross-cell coverage may occur

too, if the cell direction is consistent with that of ground

objects (such as street and rivers) that have a waveguide

effect.


Performance


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d. The new BTS should be built where the traffic is convenient, mains supply is available,

environment is safe and less fertile land is occupied.

e. Avoid building any BTS near high power radio-transmitting station, radar station or other

interference source.

f. The new BTS should be built far away from forests so as to avoid the rapid fading of

receiving signals.

g. Pay attention to signal reflex and time dispersion in the environment such as mountainous

area, lake with steepy banks/dense lakes , hilly city and high metallic building.

h. For the site selection in urban building clusters, make the best of the heights of buildings

to realize the partition of network hierarchy.

i. The site selection should guarantee a good coverage in the major service areas at the first

stage of network construction when there are fewer BTSs.

j. Prevent the main beam of the antenna from radiating towards streets, rivers and other

ground objects so as to avoid the pilot pollution or isolated island effect resulting from the

waveguide effect.

Principle of Site Selection


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Question

How to select a good BTS site and how

to lay out the BTS so as to guarantee

the future network quality?


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Part 2 content

Chapter 1 antenna system

Chapter 2 feeder system

Chapter 3 how to make real site survey


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Section 1 overview

Section 2 Antenna selection

Section 3 Antenna angle

Section 4 Antenna height

Section 5 Antenna down tilt

Section 6 Antenna diversity

Section 7 Antenna installation

Section 8 Antenna isolation

Chapter 1 Antenna System


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Antenna

In the mobile communication system, the directional antenna with

a horizontal beam width of 90 and 65 and the omnidirectional

antenna are generally selected depending on the shape of

service area, service area and the number of channels.

Where the microcell is used for indoors coverage and tunnelcoverage, the spaced antenna and leaky cable can be selected.

In the densely-populated area in a city, the 65 antenna is mostly

used to reduce the interference on neighboring cells.

In the suburb area where subscribers are less dense, generally,

the 90 directional antenna or the omnidirectional antenna is

selected.

The brands of antenna available now include Kathrein, Allgon,

XianHaitian, Andrew etc.

Antenna


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Performance Index of Antenna

The performance indices of antenna diversify, but the most important

indices in the network planning mainly include the following:

Frequency Range

Gain

Polarization

Horizontal/Vertical half-power beam width)

Downtilt

Performance Index of Antenna

S d A t


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Spaced Antenna System

As the mobile communication network develops, subscribersare putting forward higher and higher demand on the mobile

communication network. To realize the high quality coverage

in special areas such as large building indoor,

highway/railway tunnel, and subway brings the demand on

spaced antenna system.

The spaced antenna system includes leaky cable, coaxial

feeder spaced antenna and optical fiber feeder spaced

antenna.

Spaced Antenna

A t S l ti


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Antenna Selection

The antenna is a very important part that determines the

network quality.

According to the coverage, service quality, traffic distribution

and terrain features in the BTS service area, select the antenna

in consideration of the coverage and interference of the entire

network.

The application environment of antenna can be classified into

the following types according to the terrain features or traffic

distribution:

Urban area, suburb area, rural area, highway,

mountainous area, offing, tunnel and indoor.

Antenna Selection

A t S l ti


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BTS antenna in urban area

a. Usually a horizontal half-power angle of 60 ~ 65.

b. Usually a moderate gain of 15dBi or so.

c. A downtilt of 3 ~ 6.

d. Dual polarization

BTS antenna in urban area

a. A horizontal half-power angle of 65 or 90 depending on the

practical situation.

b. A moderate and high gain of 15 ~ 18dBi.

c. A preset downtilt if necessary

d. Dual polarization or vertical polarization

Antenna Selection

A t S l ti


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BTS antenna in rural area

a. A 90 or 120 directional antenna or omnidirectional antenna can beselected depending on the practical situation and requirements.

b. The gain of the directional antenna is usually high (16 ~ 18dBi).

c. Usually the antenna with a preset downtilt is not selected, and the zero-filled

antenna is preferred for a high BTS.

d. Vertical polarization is recommended.

BTS antenna near highway

a. Usually a directional antenna with a narrow beam and a high gain is

selected, or an 8-shaped antenna, omnidirectional or anamorphic

omnidirectional antenna can be selected depending on the practical

situation.

b. The coverage distance of highway BTS is required to be long, so the

antenna with a preset downtilt is usually not selected.

c. Vertical polarization antenna is recommended.

d. The front-to-rear ratio should not be too large.

Antenna Selection

A t H i ht


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Design Principle of Antenna Height

The height of antennas may differ in different cells in the same BTS,

depending on the installation space in a direction or the cell planning

requirements.

The effective antenna height is usually 25m or so in a flat urban area.

The antenna height can be properly lengthened for a BTS in a

suburb county, usually 40m or so.

Too high an antenna will reduce the coverage level near the antenna

(blind area under tower), and this phenomenon is especially

obvious for an omnidirectional antenna. Too high an antenna will cause the serious cross-cell coverage,

which affects the network quality.

Antenna Height

A t A l


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Design Principle of Antenna Angle

The antenna angle should be designed in consideration of the entire network. Oncondition that the coverage requirement is met, the azimuth angle of three sectors of

each BTS in the urban area should be consistent and only need partial trimming. The

azimuth angle of antenna can be adjusted according to the major coverage objects at

the junction of urban and suburb, along the arterial traffic and in suburb isolated island.

The main beam of antenna should point to the dense traffic area, which can intensifythe signal strength in this area and improve the call quality.

The deviation of the main beam of antenna from the co-frequency cell can effectively

control interference.

The cross coverage depth of antennas between sectors in the urban area should not

exceed 10%.

The cross coverage depth between neighbor cells in suburb area and towns should

not be too high. The included angle between the antennas in neighbor sectors in the

same BTS should be greater than 90.

To avoid cross-cell coverage, the main beam of antenna should not direct to

straight streets in a densely-populated urban area.

Antenna Angle

D tilt


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Design Principle of Antenna Downtilt

The beam tilt of antenna is the basic technology of improving the

frequency reuse capability.

The antenna downtilt technology can effectively control coverage

area and reduce the system interference.

The antenna downtilt must be determined in such a way

according to the specific situation that it can not only reduce the

interference between co-frequency cells, but also meet the

coverage requirement.

The antenna downtilt should be designed in consideration of

factors, such as BTS transmit power, antenna height, cell coverage

area and radio propagation environment.

Downtilt

Beam Tilt


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The beam tilt of antenna can be obtained electrically or mechanically. The

beam tilt in the electrical way is related to the selected antenna, and

usually is fixed. The beam tilt in the mechanical way is adjustable, but is

subject to installation accessories and propagation characteristics of radio

signals, and usually does not exceed 15.

The beam tilt in the electrical and mechanical ways will generate different

surface radiations. The difference is little when the beam tilt is not large,

but it will become significant as the beam tilt increases:

Beam Tilt

Space Diversity Distance


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c. Meet the requirement of space diversity gain distance:

In the case of space diversity, the distance between two receiver antennasshould be 12 ~18.

The higher the antenna is installed, the longer the horizontal distance

between diversity antennas is. Generally, the horizontal distance between

diversity antennas is 0.11 times as long as the effective antenna height.

To achieve the same diversity effect, the vertical diversity distance must be 5

~ 6 times as long as that in the case of the horizontal diversity antenna.

To reduce the mutual influence of two antennas, the distance between

horizontal diversity antennas should be greater than 3m in the case of any

effective antenna height.

Space Diversity Distance

Installation Environment


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Pay attention to the following during installation:

a. Installation environment

The installation environment includes environment around

the antenna and that around BTS. For the environment

around antenna, the isolation between antennas and the

effects of tower and building on the antenna should be

considered. For the environment around BTS, the effects of

high buildings within the distance of 500m on the radio signal

propagation should be mainly considered.




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During the installation of BTS antenna, please see whether a

large shaded area will form in the coverage. Obstructions

should be avoided. For example, the barrier of the building

top to the radio signals should be avoided and the antenna

should be installed as near the edge of building top as

possible when the antenna is installed.



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Sufficient space should be provided around an omni-

directional antenna and there should be enoughspace to the top of the building

when an antenna is installed at the top of a building,

assume that the vertical beam width of the antenna is

and the distance from the edge of the building to

the antenna is d, then the height between the antenna

and the top of the building is: h=dtan (/2)


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H

n

h

d

building

Distance from the antenna to the

edge of the building D (m) Distance from the bottom of the antenna tothe top of the building H (m)

0 to 1 0.5

1 to 10 2

10 to 30 3

> 30 3.5

Antenna Isolation


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b. Antenna isolation

The receiver and transmitter of the BTS should be isolated to

some extent.

The isolation between antennas is the signal attenuation from

one antenna port to another antenna port in the practicalinstallation.

CDMA system: The isolation between two transmitter antennas,

and between the receiver antenna and transmitter antenna

should be 30dB at least.

Vertical layout of antenna: Lv=28+40log(k/)(dB)

Horizontal layout of antenna: Lv=22+20log(d/)-(G1+G2)-

(S1+S2)(dB)

Antenna Isolation

Isolation for Shared BTS


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CDMA and GSM share BTS

Save construction cost

Shorten construction period

Isolation between systems in the case of

construction of shared BTS

Spurious interference requirement

Isolation for Shared BTS

Isolation Requirement


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UP LINK

825 835 870 880MHZ

CDMA--GSMinterference

Frequency bands avai lable to CDMA 1X sys tem

=Isolation between two antennas:57dB

DOWN LINK

UP LINK DOWN LINK

UP LINK DOWN LINK

Frequency b ands avai labl

to Chin a Mobi le GSM

891.4

909

936.4

954

909MHZ 954MHZ

915MHZ 960MHZ

Frequency bands

available to Ch ina

Unicom GSM

Spurious interference index stipulated in the protocol: -

13dbm/100khz

Attenuation at 890MHZ: 56dB

Attenuation at 909MHZ: 80dB




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D=5.3m

Distance between

CDMA-GSM

horizontal antennas




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Distance between

CDMA-GSMvertical antennas


D=

0.3m



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Section 1 CDU

Section 2 Feeder


Combining and Distribution Unit


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Combining and Distribution Unit

Introduction to Antenna Feeder System

The antenna feeder system consists of combining &

distribution unit, feeder, tower top amplifier and antenna.

Combining and distribution unit

Functions:

It mainly performs the transmit-receive duplex, combining

and filtering of transmitting signals, filtering of receiving

signals, amplification and division of low noise, provides a

feed circuit for the tower top amplifier, and realizes that

multiple transmitting signals and receiving signals share

one set of antenna.

Feeder


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Feeder

Common feeder types:

1/2,7/8and 5/4

Principle of feeder selection:

450MHz, usually the 7/8feeder, instead of 5/4is adopted.

800MHz, the 5/4feeder is adopted if the length is more than 80m.

1900MHz, the 5/4feeder is adopted if the length is more than 50m. The curvature of feeder should not be too large, and the external

conductor should be well grounded.

Feeder loss: 450M: about 3dB/100m for 7/8feeder and 2dB/100m for 5/4feeder.

800M: about 5dB/100m for 7/8feeder and 3dB/100m for 5/4feeder.

1900M: about 6dB/100m for 7/8feeder and 4dB/100m for 5/4feeder.

Feeder

Chapter 3 how to do real site survey


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Section 1 preparations and

steps

Section 2 how to use a GPS

Section 3 how to use a campus

Section 4 decide the shelter

and tower location

Section 5 how to take a photos

Chapter 3 how to do real site survey


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Preparation and steps

Preparations

Get all info. About the job

Contact the related engineers

Prepare related documents

Prepare the tools

Steps

Coordination meeting

Precaution in the survey

Survey end meeting

Survey report archiving

Modify survey data

How to use a GPS


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The steps of using a GPS ( simple way ) if I am on the site

Check all the hardware and accessories

You have to be on roof top

Power on

Waite till acquisition (3 received signal at least )

Take the reading (the location information )

X: longitude

Y: latitude

If we going to the site place

Arrange the car

Take your equipments

GPS with its accessories

Laptop with Maps

Connect your equipments

How to use a GPS cont


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Connect your equipments

power on all the equipments

Open the Maps using GPS software

Enter the wanted Location coordinates

Take the path to location.

After arriving, apply site selection rules to decide the

appropriate place for the site.

How to choose the shelter and tower


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location First you have to know the shelter

size and dimensions

And you have to know the tower

height

Put the tower as far as from any

obstacles

As near as possible from the shelter

Has enough space for cable trays

Choose the suitable location for the

shelter where

Easy to access (for implementationand maintenance)

near as possible from the tower to

reduce feeder length

Safety and security

How to take the photos using Digital camera


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Prepare the digital camera

Ensure its battery

Then take a good position on the site

(preferred to be on the highest position

on the site)

Start to take a photos

Shelter location photo

Tower location photo

Then take 12 photos each one is differentfrom the other by 30 degree to show all

surrounding area of the site.

Finally save all the photos in your laptop

Part3 content


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Chapter 1 site survey report

Chapter 2 engineering parameter table


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Engineering Parameter Table


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g g

Engineering parameter table

This table include many information like longitude ,

latitude and height so on

\CDMA2000 Engineering parameter summary table-

20040804-B-1.6.xls
http://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xlshttp://localhost/var/www/apps/conversion/tmp/scratch_3/CDMA2000%20Engineering%20parameter%20summary%20table-20040804-B-1.6.xls


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BTS Layout and Site Selection ISSUE1.0_3.ppt

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