Site Survey and Layout of BTS Issue.ppt

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Site Survey and Layout of BTS

ISSUE 1.5

Wireless Case & Training Department

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Foreword

The survey and layout of BTS is the basis of construction for radio mobile network. It has the following functions:

Showing the system design of the network planning Determining the structure of future network Determining the quality of network operation

Thus, the proper survey and layout of BTS can ensure the installation, maintenance, and network planning.


Purpose

•Service flow of BTS survey

•Selection of site address

•Design of antenna

After learning this course, you should be

familiar with:


Contents

Chapter 1 Service Description

Chapter 2 Preparation

Chapter 3 Site Selection

Chapter 4 Antenna Design

Chapter 5 Survey Document


Service Description

Survey task

Optical test

− Surrounding architecture environment and

nature environment

Spectrum measurement

− Electromagnetic environment

Site check

− Installation condition of antenna and

equipment

− Power supply and transmission supply

Survey purpose

Collect the site information required by the networking planning and

environment description. Check whether the site meets the requirements of

construction.


Service Description

According to width of band, determine frequency multiplex mode

According to capacity forecast, traffic distribution, and coverage

requirement, estimate the required quantity of BTSs.

Confirm the position of BTS in theory.

Perform BTS survey

Design parameters of cell

Network hierarchy structure, transmit power, antenna system,

including the type, height, direction, and down tilt of antenna

Position of BTS survey in the network planning


Radio network estimation report

Site information

Whether there is a site

Obtaining spare sites

Site survey Whether

conforming site condition

Survey report

Whether meeting requirements of

site

Obtaining site; selecting radius

Electromagnetic environment test

Yes

No

Yes

NoYes

No

Service Flow


Contents







Be familiar with the engineering and collect the materials that is

related to the project :

Engineering document

Background material

Network status

Map

Configuration list

Preparation


Prepare the following tools that are

available:

Digital camera

GPS satellite receiver

Compass

Ruler

Laptop

Preparation


Preparation

Survey preparation coordination meeting

Before survey, call in all the relative personnel to hold the survey preparation

coordination meeting. The main contents of this meeting are listed as follows:

Testing electromagnetic background

Arranging survey and coordination personnel

Preparing vehicle and equipment

Making survey plan and confirming survey route

Offering the primary schemes of transmission

and power


Contents







Site Selection

After completing preparation and knowing about the coverage requirements, start to

select site.

When confirming the site, consider the following information:

Original network condition

Population distribution and local custom

City structure and town distribution

Main streets and traffic flow

Mountainous region, lake, river, and coastline

Long-term development trend


Principles of Selecting Site

Choosing sites in the

heavy-traffic region and

concentrated subscriber

region

Population distribution

Traffic distribution

Subscriber flow direction

Principle Principle

Surrounding environment

Signal propagation quality

Trying not to choose sites near

mountain, radar, broadcasting

station, forest, and electrical

factory


The specific principles are described as follows:

Construct BTS on the ideal position of a cell. The offset sho

uld not exceed the ¼ of coverage radius.

Under the condition of the BTS layout is not affected, choo

se the existing equipment to reduce the construction cost a

nd period as possible .

To control the coverage range, reduce the difficulty of engin

eering construction, and be convenient for maintenance, do

not choose the sites on the mountain that is on the border o

f the city or suburb.

(the relative altitude to the city: beyond 100m ～ 300m)

Principles of Selecting Site


Principles of Selecting Sites

Construct the BTS at a place where transport is fluent, supply of

mains is available, environment is safe, and there is a few filed.

Do not construct the BTS near the high-power radio transmit

station, radar station, and other interference sources.

Construct BTS at a place that is far away from the forest to avoid

the fast fading of received signal.

Consider the signal reflection and time dispersion when

constructing the sites in the mountainous area, precipitous shore,

dense lake area, highland city, and the environment with high

metal building.

When choosing site in the complex, realize the division of network

structure according to the height of building.

At the early stage of constructing network, because of a few of

BTSs, ensure good coverage in important areas.


Contents







Selecting Antenna Selecting Antenna

Selecting Antenna

The selection for antenna is an important part of determining the network

quality.

According to the requirements of coverage and service quality, traffic

distribution, landform, coverage in the entire network, and interference, to

select the antenna.

According to landform or traffic distribution, the environment of using

antenna can be categorized into:

City, suburb, countryside, highway, mountainous area, offing, tunnel,

and indoor environment


Principles of Selecting Antenna

Selecting Antenna for the BTS in the city

Choose the directional antenna with 60° ～ 65° half power angle.

Choose the antenna with about 15dBi gain.

Choose the antenna with 3° ～ 6°tilt angle.

Choose dual polarization antenna.



Selecting antenna for the BTS in the suburb

According to actual conditions, choose the directional antenna with

65°or 90° half power angle.

Choose 15 ～ 18dBi middling or high gain antenna.

According to actual conditions, determine whether the tilt angle sho

uld be used.

Dual polarization antenna and vertical polarization antenna are bot

h available.



Selecting antenna for the BTS in the countryside

According to actual conditions, choose 90°or 120° directional ant

enna or omni-directional antenna.

Choose directional antenna with 16 ～ 18dBi gain.

Do not choose presetting tilt antenna. Choose null filling antenna

for the high BTS.

The vertical polarization antenna is recommended.



Selecting antenna for the BTS on the

highway

In general, choose narrow-beam and high-gain directional antenna. According to actual conditions, you also can choose 8-shaped antenna or omni-directional antenna.

Because the BTS on the highway must cover a long distance, do not choose the presetting tilt antenna.

The vertical polarization antenna is recommended.

The front-to-back ratio of the directional antenna should not too great.


Principles of Selecting AntennaPrinciples of Selecting Antenna

Selecting antenna for the BTS in the tunnel

Tunnel shorter than 2 km

Install the 10dB-12dB Yagi antenna/log-periodic

antenna/flat antenna in the jaws of tunnel to cover

a road that is less than 2km.

Tunnel longer than 2 km

Use leaky feeder, coaxial cable, and fiber

distribution system.


Principles of Selecting AntennaPrinciples of Selecting Antenna

Selecting Indoor Antenna

Omni-directional antenna

Vertical polarization, 2dBi gain, cap-shaped or cup-shaped, small

size, convenient for installation, graceful

Directional antenna

Vertical polarization, 90°half power angle

7dBi gain


Antenna Height

Due to the installation space or cell planning, the heights of antenn

as that are in different cells of a BTS can be different.

For the BTS in the city, the height of antenna is about 25m.

For the BTS in the suburb, the height of antenna is about 40m.

If an antenna, particularly the omni-directional antenna, is too high,

the coverage level of the place that nears to the antenna may be lo

wered, that is, no signal under the power.

In addition, the too high antenna may lead to cross coverage and i

ntra-frequency/neighboring-frequency interferences that affect the

network quality.

Principles of Design for Antenna Height Principles of Design for Antenna Height


Principles of Design for Antenna Azimuth Angle Principles of Design for Antenna Azimuth Angle

Azimuth Angle

Based on signal coverage, ensure that the azimuth angles of three sectors are the

same. Adjust the azimuth angles of antennas according to important coverage obje

cts on the border of city and suburb, in the traffic artery and isolated site of suburb.

To enhance the signal strength and improve call quality, adjust the major lobe of an

tenna to face to the heavy-traffic areas.

To control interference, adjust the major lobe of antenna to be apart from intra-freq

uency cells.

The cross coverage areas of neighboring cells in the city should not exceed 10%.

The cross coverage areas of neighboring cells in the suburb and village should be

not too large. The azimuth angle of neighboring cells should not less than 90°.

To avoid cross coverage, do not make the major lobe of antenna face to the

straight streets in the crowded areas.


Principles of Design for Tilt Angle Principles of Design for Tilt Angle

Tilt Angle

The beam tilt is a basic technology for improving Frequency Reuse capa

bility.

The antenna tilt technology is used to control coverage scope and reduc

e the interferences in the system.

To reduce the interferences from co-channel cells and meet the coverag

e requirements, set the tilt angles based on specific conditions.

The design for tilt angle should be based on transmitter power, antenna

height, cell coverage, and radio environment.


Tilt Angle The antenna tilt is categorized into electrical mode and mechanical mode. T

he angle of the electrical tilt is relative to the model of antenna. The angle of

the mechanical tilt is adjustable, but it is limited by installation accessory an

d signal transportation. Often the angle should not exceed 15°.

The electrical tilt and mechanical tilt have surface radiations that differ with t

he increases of angles.


Installing Antenna A. Installation Environment

The installation environment contains the ambient of antenna

and that of BTS.

For the ambient of antenna, check the isolation between

antennas and impacts of tower and roof on antennas.

For the ambient of BTS, check whether the high buildings that

are 500m away have impacts on signal transportation.


2〉 10

12～ 10

0.50～ 2GSM1800M

3.5〉 30

310～ 30

21～ 10

0.50～ 1

GSM900M

h（ m）D（ m）FREQ

Installing Antenna

When installing antenna, consider whether the ambient affects the

coverage cell. Keep the antenna away from barriers. If you need to

install antenna on the roof, try to install it on the edge.


Installing Antenna

B. Antenna Isolation

The receiver and transmitter must have a certain isolation.

Isolation between antennas: Attenuation of signal from a anten

na port to another

GSM system: The isolation between two transmitter antennas

and the isolation between the transmitter antenna and the rec

eiver antenna should be not fewer than 30dB.

− Antenna vertical layout: Lv=28+40log(k/λ)(dB)

− Antenna horizontal layout: Lv=22+20log(d/λ)-(G1+G2)-(S1

+S2)(dB)


C. Requirements for Space of Diversity

When you perform space diversity, the distance between two receiver antennas

should be 12λ to 18λ.

When an antenna is installed highly, the horizontal space of the diversity

antenna should be large. Usually the space of diversity antenna is 0.11 times of

the height of the antenna.

To achieve the same effort, the vertical diversity space should be five to six

times of the horizontal diversity space.

To reduce the mutual effects of two antennas, the horizontal diversity space

should be more than 3m.

Installing Antenna


Contents







Survey report Survey report

Survey Document

The standard survey report provides service for the subsequent network planning and network optimization. It is the guarantee of engineering quality and the basis of planning for network capacity.

The survey report consists of survey table and memo.

The survey table records the longitude and latitude of a BTS, antenna design, and ambient.

Shoot the picture of BTS coverage area in the direction of north. Get eight pictures every 45°.


Illustration of Survey Document

Survey Table

Engineering Parameter Table


Surrounding of BTS

Installation platform

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Site Survey and Layout of BTS Issue.ppt

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