Copy Rights © LEGEND Co. 2010 - E-Learning/An-Najah...

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Copy Rights © LEGEND Co. 2010


11/08/2014

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Introduction

RF people work in either

RF Planning RF Optimization

Responsibilities

Nominal Plan Design

Sites Survey

Validation from field

Set RF design (Structure, Azimuth,

Height, Tilt, Cables type)

Frequency Plan

Sites Acceptance

They have to provide the coverage either

outdoor or indoor.

Responsibilities

Maintain the Network‘s Accessibility KPIs

Maintain the Network’s Retain ability KPIs

Maintain the Network’s Service Integrity KPIs

Study and Apply new features

Try to think of innovative solutions to

maximize the Network capacity

They have to maintain the performance of

the Network as good as possible.


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Course Outlines

Planning Process and Procedures.

Dimensioning Process.

Site Tuning.

Technical Site Survey.

Neighbors and Frequency Planning.


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GSM System Survey Revision

GSM stands for “ Global System for Mobile Communication”

Second Generation for Mobile System.

Digital System.

Efficient Use of the Spectrum.

Speech privacy and security.

Better resistance to interference (Introducing the frequency Hopping)

Efficient use of the power battery (Introducing the power control)

GSM Networks are called “PLMN: Public Land Mobile Networks” i.e. the

Radio Sites are located on land, not using satellites.

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• GSM System can work in different bands as follows:

– DCS: Digital Cellular System PCS: Personal Communication Services.

• But what do we mean by frequency Band?

• What is the DL and UL?

• Why DL is higher than UL band?

Frequency Band-Down Link Frequency Band-Up Link

GSM 800 869 894 MHz 824 849 MHz

E-GSM (Extended GSM) 925 935 MHz 880 890 MHz

P-GSM 900 935 960 MHz 890 915 MHz

GSM 1800 (DCS) 1805 1880 MHz 1710 1785 MHz

GSM 1900 (PCS) 1930 1990 MHz 1850 1910 MHz



• Frequency Band

– The range of frequencies which the operator is allowed to use for transmission

and reception.

• Down Link and Up link bands

– DL band is the range of frequencies used by the Base station when

transmitting to the MS while the UL band is the range of frequencies used by

the Mobile station when transmitting to the Base Station.

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• Why DL band is higher than the UL band?

– As freq then attenuation with air

– Since Power BaseStation > Power MobileStation then it is wise to configure the higher

frequencies that will be attenuated fast to the side that is using higher power.



• Access Techniques What do we mean by Access techniques?

These are the Techniques through which many MSs can access the shared media

which is the air interface.

i. FDMA ( Frequency Division Multiple Access)

Each MS is assigned a dedicated frequency through which he can talk.

ii. TDMA (Time Division Multiple Access)

All MSs are using the same frequency but each of them will be utilizing

it only over a certain period of time called Time Slot (TS)

In GSM System we’re using TDMA over FDMA where the frequency band

is divided into no. of frequencies each of which is shared among no. of

MSs, where each MS will be assigned a certain TS on certain

frequency.

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• For P-GSM (GSM 900)

– UL Band 890MHz 915MHz, DL Band 935MHz 960MHz

– Each Band is 25 MHz

– Guard Band between DL and UL is 20 MHz

– Duplex Distance = 45 MHz

– Carrier separation = 200 KHz

– No. of frequencies = 124

GSM 900 Frequency Allocation

F (MHz)915890

Uplink1 2 3 4 121 122 123 124

F (MHz)

Downlink

960935

1 2 3 4 121 122 123 124

890.2

890.4

890.6

935.2

935.4

935.6

200 KHz

1

1

121

121

Downlink 935 – 960 MHz

Uplink 890 – 915 MHz



• For the all GSM Bands

System P-GSM 900 E-GSM 900GSM(DCS)

1800

GSM(PCS)

1900

Uplink (MS BS)

Downlink(BS MS)890 – 915 MHz

935 – 960 MHz

880 – 915 MHz

925 - 960 MHz

1710 – 1785 MHz

1805 - 1880 MHz

1850 – 1910 MHz

1930 - 1990 MHz

Wavelength 33 cm 33 cm 17 cm 16 cm

Bandwidth 25 MHz 35 MHz 75 MHz 60 MHz

Duplex distance 45 MHz 45 MHz 95 MHz 80 MHz

Carrier separation 200 kHz 200 kHz 200 kHz 200 kHz

No. of carriers 124 174 374 299

Channel rate 270.8 kbps 270.8 kbps 270.8 kbps 270.8 kbps

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• GSM Network Architecture



• Core Network (NSS: Network Switching System)

MSC (Mobile Switching Center)

Routing/Switching of calls between 2 end users within the GSM Network.

Charging & Billing.

Service Provision.

Access to PSTN (Public Switched Telephone Network)

Act as a Gateway for other networks

Controls no. of BSCs connected to it.

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HLR (Home Location Register)

Centralized Network data base stores and manages all mobile subscriptions.

Example: IMSI, MSISDN, MSRN, Services subscribed/restricted for that user.

VLR (Visitor Location Register)

It is co-located with the MSC.

Stored in it a copy of the user’s profile on temporary basis.

AUC (Authentication Center)

Provides the HLR with the authentication parameters and ciphering Keys used

by the MSC/VLR to authenticate center user. (Triplets: RAND, SRES, Kc)

EIR (Equipment Identification Register)

Used to authenticate the user equipment through the IMEI.

IMEI = International Mobile Equipment Identification



• BSS (Base Station System) BSC (Base Station Controller)

It controls the air interface, it takes the decisions based on the reports came

from the MS and BTS.

Channel Allocation.

Controls the Handover Process.

Dynamic Power Control.

Frequency Hopping.

BTS (Base Transceiver Station)

It is the Hardware equipment needed to provide the radio coverage.

Speech Coding/Channel Coding/Interleaving/Ciphering/Burst

formatting/Modulation all these are done within the BTS (RBS=Radio Base

Station)

Equipment: Cabinet, jumpers, feeders, combiners, antennas.

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• MS (Mobile Station) Mobile Equipment

Transmit the radio waves.

Speech coding and decoding.

Call control.

Performance measurement of radio link.

SIM card (Subscriber Identification Module)

Stores user addresses (IMSI, MSISDN, TMSI).

Stores authentication key Ki, authentication algorithm A3 and ciphering

algorithm A8&A5

Stores the subscribed services.



• Over the Air Interface Frequency Band is divided into no. of frequencies.

Each frequency is divided into 8 Time slots (TS)

Each user will be assigned 1 TS.

One time slot =156.25 bits

1 Bit duration=3.69 µsec

Time slot duration =156.25x3.69 µsec= 0.577 msec

1 Frame = 8 TSs

Frame duration=0.577x8= 4.615 msec

Bit rate on the air interface is 270 Kbps, but for each user it is 33.8 Kbps

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• Physical Channels vs. Logical Channels

Physical channel: Time slot is called the physical channel.

Logical channel: It is the content that will be sent over the physical channel.



• Logical Channels

Logical Channels

Control ChannelsTraffic Channels

Half Rate Full Rate

Synchronization Channel

Broadcast Control Channel

Frequency Correction Control Channel

Standalone Dedicated Control Channel

Slow Associated Control Channel

Fast Associated Control Channel

Cell Broadcast Control Channel

Broadcast Dedicated

Random Access Channel

Access Grant Channel

Common

Paging Channel

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• Traffic Channels

Full Rate Channels (FR)

Carries user’s speech traffic or user data DL and UL.

Each user is assigned 1 TS.

Transmission rate is 13 Kbit/s.

Half Rate Channels (HR)

Carries user’s speech traffic or user data DL and UL.

2 users will share 1 TS (physical channel), each of them will be utilizing it

each frame.

Transmission rate is 6.5 Kbit/s

Logical Channels


Half Rate Full Rate








Broadcast Dedicated



Common

Paging Channel



• Control Channels

These are used to carry signaling or synchronization data, they’re divided into

three types:

Broad Cast Channels (BCH)

Common Control Channels (CCCH)

Dedicated Control Channels (DCCH)

Logical Channels


Half Rate Full Rate








Broadcast Dedicated



Common

Paging Channel

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• BCH (Broad Cast Control Channels)

i. Frequency Correction Channel (FCCH)

Pure signal is transmitted to help the MS to lock on the frequency of the BTS

and synchronize to its frequency. (DL channel)

ii. Synchronization Channel (SCH)

Carries the TDMA frame number.

BSIC (Base Station Identification Code) of the cell. (DL Channel)

iii. BCCH (Broad Cast Control Channel)

LAI (Location Area Identity)

Cell parameters (used power, Idle mode parameters,…..etc)

List of BCCH carries of the neighbor cells. (DL Channel)

Logical Channels


Half Rate Full Rate








Broadcast Dedicated



Common

Paging Channel



• CCCH (Common Control Channels)

i. Paging Channel (PCH)

Used to inform the MS of an incoming call or sms, where the MS’s IMSI/TMSI

will be sent over it. (DL channel)

ii. Random Access Channel (RACH)

Used by the MS to ask for an SDCCH to respond to the request send on the

paging channel /initiate a call/location update/IMSI attach-detach. (UL

Channel)

iii. AGCH (Access Grant Channel)

Used by the network to assign an SDCCH sub-channel for the MS. (DL

channel)

Logical Channels


Half Rate Full Rate








Broadcast Dedicated



Common

Paging Channel

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• DCCH (Dedicated Control Channels)

i. Standalone Dedicated Control Channel (SDCCH)

Used for signaling purposes: call setup, location update, IMSI attach-detach.

Used to send/receive SMSs in idle mode. (DL/UL channel).

ii. Slow Associated Control Channel (SACCH)

Always allocated in conjunction with traffic channel/SDCCH channel to

transmit measurement reports.

DL measurement reports will include commands from the network to the MS

to adjust its power level and info about the Time Advance.

UL measurement reports will include information about the MS own power,

received SS & Quality from serving cell and SS from neighbor cells.

Used to send SMSs in active mode

(DL/UL channel).Logical Channels


Half Rate Full Rate








Broadcast Dedicated



Common

Paging Channel



iii. Fast Associated Control Channel (FACCH)

Used to send necessary Handover information . (DL/UL channel)

iv. Cell Broad Cast Channel (CBCH)

It is sent point to multi point i.e. from the cell to the mobiles attached to it, this

channel may carry information about the traffic, weather reports,…etc. (DL

channel)

Logical Channels


Half Rate Full Rate








Broadcast Dedicated



Common

Paging Channel

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• Mapping of Logical Channels on the Physical channels

Mapping on TS0/BCCH carrier (DL)

51 consecutive control frames = 1 Control multi frame




Mapping on TS0/BCCH carrier (UL)

TS0 in UL is reserved for the RACH, for the MS to access the system.

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Mapping on TS1/BCCH carrier (DL)




Mapping on TS1/BCCH carrier (UL)

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Mapping on TS2/BCCH carrier (DL/UL) if it will be used by certain MS in active

mode

26 consecutive Traffic frames = 1 Traffic multi frame



• TDMA Multi Frames Structure Traffic Multi Frames

Traffic Multi Frame = 26 consecutive traffic frames (4.61msec x 26 =120msec)

Control Multi Frames

Control Multi Frame = 51 consecutive Control frames (4.61msec x 51

=235msec)

Super Frame

51 consecutive Traffic Multi Frames or 26 consecutive Control Multi Frames

Super Frame = 6.12 seconds

Hyper Frame

2048 consecutive super Frames

Hyper Frame = 3 hours and 29 minutes nearly.

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Cell Planning Process

• Cell Planning Process

Cell Planning can be described briefly as all the activities involved in

determining the number of sites that shall be used, type of equipments and

their configuration in order to ensure continuous coverage and good quality.

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• Traffic and Coverage Analysis

The cell planning process starts with a traffic and coverage analysis. The

analysis should produce information about the geographical area and the

expected capacity needed.

The types of data collected are:

Cost, Coverage, Traffic demand and its distribution, GoS, Available Frequencies.

The traffic distribution can be estimated based on:

Population distribution, car usage distribution, income level distribution,

Telephone usage.



• Nominal Cell Plan

After compilation of the data received from the traffic and coverage analysis, a

coverage and capacity dimensioning will be done to produce the nominal cell

plan.

The Nominal Cell Plan is a graphical representation of the network which

simply looks like a cell pattern on a map.

• Sites Surveys

The sites where the radio equipment will be placed are visited, it is necessary

to assess the real environment to determine whether it is a suitable location or

not.

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• System Design

After the surveys from field are performed the design for each site is done

including: Site Structure, Height, Azimuth, Tilts, Types of Cabinets, Antennas

and Feeders.

• Implementation

This includes sites installation, commissioning testing the hardware and drive

testing to ensure that the sites are behaving well.



• System Tuning

After the system has been installed it is continuously monitored and evaluated

to determine how well it meets the demand. This is called System Tuning and

it involves:

• Checking that the final plan has been successfully implemented.

• Evaluating the customer complaints.

• Checking the network performance and parameters settings.

The system needs constant retuning due to the fact that the traffic and the

number of subscribers continuously increase.

The network may reach the point where it must be expanded so that it can

manage the increasing load and new traffic and now the coverage and traffic

analysis is performed and the cell planning cycle is repeated.

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RF Sites and Hardware Equipments

• Site Types and Hardware Equipment

We have many types for RF sites having different structures and design.

The choice of the RF site used will be during the validation phase, where the

planner will be responsible to choose the proper site type and structure based

on his target for coverage.



• Site Types

Micro Site

Site Types

Street LevelIndoor

Macro Site

COW Green FieldRoof Top

MonopolePolesStup tower Tower

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• Site Types

Macro Sites

– Macro Sites are those which utilize cabinets that generates high power

(~47dBm = 50W) and used to provide outdoor and indoor coverage over

relatively medium and large distances in cities and on roads.

Micro Site

Site Types

Street LevelIndoor

Macro Site





• Site Types

Macro Sites

Roof Top Sites: The antennas are placed on the roof of the buildings, used in

urban and dense urban clutters ex: Inside the cities.

Stub Tower Poles

Micro Site

Site Types

Street LevelIndoor

Macro Site



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• Site Types

Macro Sites

COW Sites: COW stands for a “ Cell On Wheel”, these are temporary sites

used in events to maximize the capacity ex: exhibitions/Stadiums.

Micro Site

Site Types

Street LevelIndoor

Macro Site


MonopolePolesStuptower Tower



• Site Types

Macro Sites

Green Field Sites: These sites are standalone sites used mainly on roads

and high ways to provide coverage for long distances.

Green Field Tower Monopole Palm Trees

Micro Site

Site Types

Street LevelIndoor

Macro Site



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• Site Types

Micro Sites

– Micro Sites are those which utilize cabinets that generate low power (~ 34

dBm = 2W) used in outdoor streets for capacity issues in the hot spot areas

(ex: Abdel Aziz St.) and used in Indoor buildings for both coverage and

capacity issues (Malls, Hotels)

Street Level-Micro Outdoor Micro Indoor

Micro Site

Site Types

Street LevelIndoor

Macro Site





• Hardware Equipments– The Hardware Equipments of the RF sites are those used to provide the radio

coverage over the air interface and can be seen as below:

• BTS Cabinet ( Including DTRUs, Duplexers and Combiners)

• Feeders, Jumpers and Connectors

• Diplexers (In some cases)

• TMA

• BTS Antenna

• Repeaters

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• Hardware Equipments

BTS (Cabinet)

“Outdoor Cabinet”

– This type of cabinets is used with Macro sites, it has built-in air conditions, it

doesn’t need shelters and able to resist the different environmental conditions.

Typical Macro Outdoor CabinetFrequency Band P-GSM 900, E-GSM 900, GSM 1800

Tx 935-960MHz, 925-960MHz, 1805-1880MHz

Rx 890-915MHz, 880-915MHz, 1710-1785MHz

Number of Transceivers 12

Dimension (WxDxH) 650x888x1380 mm

Weight 270 Kg

Output Power

Combined, Uncombined)

900MHz: 42.5/46 dBm

1800MHz: 42.0/45.5 dBm

Receiver Sensitivity −110.5 dBmCabinet

DW

H




BTS (Cabinet)

“Indoor Cabinet”

− This type of cabinets is used with Macro sites,

external air conditions should be used,

it needs a shelter to prevent the equipment from

the different environmental conditions (rain, heat,…)

Typical Macro Indoor CabinetFrequency Band P-GSM 900, E-GSM 900, GSM 1800

Tx 935-960MHz, 925-960MHz, 1805-1880MHz

Rx 890-915MHz, 880-915MHz, 1710-1785MHz



Weight 150 Kg

Output Power


900MHz: 42.5/46 dBm

1800MHz: 42.0/45.5 dBm

Receiver Sensitivity −110 .5dBm

Shelter

Cabinet

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BTS (Cabinet)

− This type of cabinets is used with Micro sites.

Typical Micro CabinetFrequency Band P-GSM 900, E-GSM 900, GSM 1800

Tx 935-960MHz, 925-960MHz, 1805-1880MHz

Rx 890-915MHz, 880-915MHz, 1710-1785MHz



Weight 41 Kg

Output Power


900MHz: 34/32 dBm

1800MHz: 33.5/31.5 dBm

Receiver Sensitivity −109 dBm




Duplexer

− Duplexers are devices make us able to transmit and receive on the same

cable.

− External Duplexers have typical losses = 0.5 dBs

− DTRUs have internal Duplexers that have nearly zero losses.

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DTRU (Dual Transceiver Unit)

− It is the hardware unit on which the frequencies are configured.

− If the internal combiner is used then this will result in 3dB losses in the output

signal.

Duplexer

TX1

RX1

TX1/RX1

RXD1

RXD2

TX2

RX2 TX2/RX2

Hybrid

Combiner Combined

Mode

TX1/RX1

TX2/RX2

Un Combined

Mode

Duplexer




Combiner

− The internal combiner in the DTRU is used to combine two signals from the

same band to be transmitted on the same cable.

− The combiner is a broadband one that doesn’t need tuning.

− The combining stage will result in 3 dB loss in the output signal.

− If we need to make expansion ( connect 2 DTRUs = 4 frequencies to be

connected to the same antenna) then the combiner should be used.

DuplexerTX3RX3 TX1/RX1

RXD1

RXD2TX4RX4 TX2/RX2

Duplexer

DuplexerTX1RX1 TX1/RX1

RXD1

RXD2TX2RX2 TX2/RX2

DTRU1

DTRU2

Duplexer

Hybrid

Combiner

Hybrid

Combiner

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Feeders, Jumpers and Connectors

− Feeders, jumpers and connectors are responsible

to carry the electrical signal from the BTS to the antenna.

− Jumpers are flexible and used as a connection between Feeder-BTS

and Feeder-Antenna.

− Typically, Jumper losses=0.5dB while connector losses=0.1dB

− Feeder losses will differ based on the feeder’s diameter as below.

BTSjumper jumper

Feeder

Feeder Type 800/900 (dB/100m) 1800/1900 (dB/100m)LCF 1/2" 7.0/7.2 10.5

LCF 7/8" 4 6.5

LCF 1-1/4" 3.3 5.3

LCF 1-5/8" 2.6 4.2




Diplexers

− Diplexers are used to combine two signals from different bands.

− Typically, Diplexer losses=0.3dB

− Typically with 4 port antennas, the output from the 1800-DTRU is mixed with

the output from the 3G cabinet via the diplexers.

3G Cabinet

DTRU-900

DTRU-1800

2G Cabinet

Diplexer

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TMA (Tower Mounted Amplifier)

− The TMA is installed direct after the BTS antenna.

− It is used to enhance the uplink signal received by the antenna before being

deteriorated through the feeders.

− The use of TMAs is important due to the fact that the output signal from the

MSs are transmitting in the uplink with low power.

− With TMAs the received signal will be amplified so even when it is attenuated

through the cables it will reach the BTS with acceptable level.

− In the downlink, the TMA will add 0.3 dB losses, while in the uplink it will add

gain nearly = 24 dB.




Antenna

− It is the device used to convert the electrical signal from the cables to an

electromagnetic radiations propagating on the air interface.

− Isotropic Antenna: Is a theoretical/reference model for an antenna propagating

equally in all directions.

− Omni Antennas: Propagates equally in one plan.

− Directive Antennas: Propagates in certain direction.

Isotropic Antenna Omni Antenna Directive Antenna

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Antenna

− Antenna Gain:

• Since Antennas are passive elements, then the only way to have gain in

any direction is to increase the directivity by concentrating the radiations

in the desired direction.

• Now the Antenna gain can be defined as the ratio between the power of

the max direction of the antenna to the power obtained by an isotropic

antenna in the same direction.

• Gain for Typical directive antennas = 18 dBi and for Omni antennas = 11

dBi




Antenna

− Beam Width:

• Defined as the angel between the max direction to the direction where the

power is reduced to the half in the max direction.

Horizontal Beam

width =65

3dB

Direction of

the max

power

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Antenna

− Beam Width:

• The standard antenna has a horizontal beam width of 65deg, this means

that the gain at 32.5deg is 3 dB less than the maximum gain ( i.e. half the

power)

• Typically the vertical beam width is 7 degrees.




Antenna

− Tilting:

• Normally when the antenna is correctly mounted, then the vertical beam

of the antenna is pointing towards the horizon.

• Lowering the beam below the horizon is known as “Down tilt”, and when

the beam is directed above the horizon then it is called “Up tilt”

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Antenna

− Tilting:

• According to how the tilt is implemented; we have two types: Mechanical

tilting and Electrical tilting.

• Mechanical tilting: the physical body of the antenna is tilted, which cause

tilting in the main beam.

• Electrical titling: we change the phase of the current fed the internal

dipoles which will result in tilting the main beam.




Antenna

− Tilting:

• With mechanical down tilting the main beam will be down tilted which is

useful but this will result in up tilting the back lobe which may interfere on

another cells.

• With antennas support mechanical tilting only, we won’t be able to have

different tilting for different bands if needed.

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Antenna

− Diversity:

• Defined as the redundancy in receiving or transmitting the signal.

• The purpose is to overcome the attenuation and fading that may

encounter the signal while propagating in air.

• Typically the antenna diversity results in a 3.5 dB gain.

• We have two types of diversity: Space Diversity and Polarization Diversity.




Antenna

− Diversity:

• With Space diversity we’ll use 2 antennas that should have separation =

12-18λ

(λ=0.33m for GSM900 and λ=0.17m for GSM1800) in order to obtain the

desired gain.

Space

Diversity

SS

Time

1 2 1 2

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Antenna

− Diversity:

• With Polarization diversity, the antenna will be manufactured with internal

arrays have dual polarizations, either Horizontal & Vertical or +45/-45

Dual Polarized

Antenna




Antenna

− Diversity:

• The polarization is the direction of oscillation of the electric field with

respect to ground.

• Vertically polarized antennas: Transmit electromagnetic waves where the

electric field component oscillate in direction perpendicular to the ground.

• Horizontal polarized antennas: Transmit electromagnetic waves where the

electric field component oscillate in direction parallel to the ground.

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Antenna Diversity:




Repeaters

− A repeater can cover areas that otherwise would have been blocked by

obstacles.

− Fields of application are roads in hilly terrain, tunnels or other obstructed low

capacity areas.

− The signal is typically amplified by 50-80 dB.

Road

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Repeaters

− Repeaters can also been used for indoor applications, like offices and

undergrounds.


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Sites Surveys and Validation

The cell planning process results in a cell plan with nominal site positions.

If the operator has access to existing locations (ex: deal with TE, Police,..etc)

then it is necessary to adapt the cell plan according to these locations.

The proposed network design shows only approximate site locations but the

exact site position depends on the possibilities of constructing a site on the

suggested location.

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Non technical issues may contribute in preferring one location than the other

provided that both of them verify the radio requirements:

Obtaining the permits from the different authorities like civil aviation and

military authorities.

Lease contract should be agreed upon with the owner of the site.

Access roads: the site must be accessible for material transport and

installation.

Space requirements for the shelter and passes for the feeders.

Space to construct the antenna supports.

AC power Source.



Technical RF requirements based on which we select the best candidate:

Distance from the nominal.

Strategic location to fulfill coverage objects.

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Technical requirements based on which we select the best candidate:

• Distance from the nominal:

The initial study of a cell system often results in a theoretical cell pattern

with nominal positions for the site locations.

The existing buildings must then be adapted in such a way that the real

positions are established and replace the nominal positions.

For each nominal point the RF planner will choose a search area such

that the nominal shouldn’t be moved out of it.

Search Area, ex: 50m

Nominal Cell Location




• Strategic location to fulfill coverage objects:

Clear of present and upcoming obstructions.

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The proper designed height can be achieved with the used tower

structure.

Typically the common structures are Poles: 6/9m poles, Stub towers:

9/12/15/18/21m Green Field Towers: 30/40/60 m

If the required antenna’s height as per the design is 35m and the

building’s height is 25m then the proper structure is 12m stub tower.

12 m

25 m





The proper tilting as per the design and simulation can be implemented

without shadowing on the roof.

D=Cell Range

H

β= tilt angle

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Ex: If H=35m and we need theoretical Cell range=500 m what will be the

proper tilting?

Tilt angle β = 90 – α = 90 – ( tan-1 (D/H)) = 90 – ( tan-1 (500/35)) = 90 – 86

= 4 degrees, then the proper tilting = 4 degrees

D=Cell Range

H

β= tilt angle

α





It is better to install the antennas on the edges of the roof.

When the antenna is placed at the mid of the roof then we have to

calculate the minimum height of the antenna in order to not have any

shadowing on the roof edge.

D=Cell Range

H

β= tilt angle

σV/2h

d

Half the vertical

beam width

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If the distance to the roof d = 50m and we’re going to apply tilt = 4

degrees, then we want to calculate the minimum tower height to not have

shadowing on the roof.

σ=90 - (β +V/2) = 90 – (4+3.5) = 90 - 7.5 = 82.5 degrees

Tan σ = ( d/h), then Tan (82.5) = (50/h) = 7.5

then h = 50/7.5 = 6.7meters (min. tower height to not have shadowing with 4

deg down tilt)

D=Cell Range

H

β= tilt angle

σV/2h

d

Half the vertical

beam width



Some Planning Tips The First Fresnel zone: The area around the visual line-of-sight that radio

waves spread out into after they leave the antenna. This area must be

clear or else signal strength will weaken.

Double Structure sites.

Roads coverage.

Obstacles like Bill Boards.

Terrain difference.

Sites near water.

Tunnels coverage.

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Coverage Dimensioning

The sensitivity of the BTS and MS is defined as the minimum required

received input level in order to decode the signal correctly.

However, when planning a system it is not sufficient to use this sensitivity level

as a planning criterion.

Various margins must be added to compensate for the degradation in the

signal level during its propagation in air.

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These margins will include:

Rayleigh Fading Margin (Fast Fading Margin) RFmargin

Interference Margin IFmargin

Body Loss Margin BL

Outdoor Log Normal Fading Margin LNFmarg(o)

Outdoor + Indoor Log Normal Fading Margin LNFmarg(o+i)

Car Penetration Loss CPL

Mean Building Penetration Loss BPLmean

Now the design level can be calculated as follows:

SSdesign = MSsens + RFmargin + IFmargin + BLmargin + LNFmarg(o) (MS Outdoor)

SSdesign = MSsens + RFmargin + IFmargin + BLmargin + LNFmarg(o) + CPL (MS in Car)

SSdesign = MSsens + RFmargin + IFmargin + BLmargin + LNFmarg(o+i) + BPLmean (MS Indoor)



Rayleigh Fading Margin (Fast Fading Margin):

Due to multipath reflection from the surrounding buildings some fading

dips may occur.

Based on measurements a Rayleigh Fading Margin of 3dB is adequate

i.e. RFmargin = 3dB

Interference Margin:

Since the frequencies are reused, then the received carrier power must be

large enough in order to compensate for the interference from

surroundings.

The interference margin depends on the frequency reuse, traffic load and

the desired percentage of area coverage. Based on measurements in

normal system an Interference Margin of 2dB is adequate i.e. IFmargin =

2dB

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Body Loss:

Since the human’s body absorbs some of the energy, then a body loss

margin is used to compensate for this power dissipation

The recommended Body Loss by the GSM standards is:

BL = 5dB (800/900 MHz Band) , BL = 3dB (1800/1900 MHz Band)

Car Penetration Loss:

When the MS is situated in a car without an external antenna (which is the

typical case) an extra margin should be added to cope with the

penetration loss of the car body.

The recommended Body Loss by the standard is: CPL = 6dB



Log Normal Fading (Slow Fading):

The signal strength fluctuates around a mean value while the MS is

moving.

This type of fading is due to the terrain structure and the obstacles like

hills and trees in the path between the BTS and MS.

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The log normal fading LNFmarg will differ based on the environment and

the coverage area.

LNFmarg will be calculated from a graph relates environment (Standard

Deviation:σLNF ) with the coverage percentage needed.

N.B: (σLNF marg(o+i) )2 = (σLNF marg(o))

2 +(σLNF marg(i) ) 2

These values were

obtained from field

measurements




• LNFmarg will be calculated from a graph relates environment (σLNF ) with

the coverage.

Example:

For an Urban area Outdoor,

then σLNF =8 dB and with

98% coverage, then we can get

from the graph LNFmarg(o) = 8 dB

σLNF

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Example:

Get SSdesign for a MS-Outdoor in different

clutters with different required percentage

of coverage.

SSdesign = MSsens + RFmargin + IFmargin + BLmargin + LNFmarg(o) (MS Outdoor)

Then SSdesign = -104 + 3 + 2 + 5 + LNFmarg(o) = -94 dBm + LNFmarg(o) (MS Outdoor)



Example:

then we can calculate SSdesign for

MS-Outdoor in different clutters as follows:

SSdesign = -94 dBm + LNFmarg(o)

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Example:

Get SSdesign for a MS-In Car in different


of coverage.

SSdesign = MSsens + RFmargin + IFmargin + BLmargin + CPL+ LNFmarg(o) (MS in Car)

Then SSdesign = -104 + 3 + 2 + 5+ 6 + LNFmarg(o) = -88 dBm + LNFmarg(o) (MS in Car)



Example:

Get SSdesign for a MS-Indoor in different


of coverage.

SSdesign = MSsens + RFmargin + IFmargin + BLmargin + BPL+ LNFmarg(o+i) (MS Indoor)

Then SSdesign = -104+3+2+5+BPL+LNFmarg(o+i) = -94 dBm + BPL+ LNFmarg(o+i)

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Example:

then we can calculate SSdesign for

MS-Indoor in different clutters as follows:

Then SSdesign= -94 dBm + BPL+ LNFmarg(o+i)



Down Link Budget

• Now, we’re going to calculate the cell radius where the PinMS will be the

SSdesign which was computed previously based on the clutter type and

coverage percentage.

Pout BTS : Output power from the Base Station Cabinet

Lf BTS : Losses in Feeders, Jumpers and connectors

Ga BTS : BTS antenna gain Gd BTS : BTS antenna diversity gain

Lp : Path Loss Pin MS : Input power at the MS Station

Pout BTS PinMS =SSdesign

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Down Link Budget

Example:

for Urban clutter with required outdoor coverage= 95% (GSM900-Band) then

Pin MS = SSdesign= -89.1 dBm and given that: Pout BTS = 46 dBm, Lf BTS = 2.6 dB

Ga BTS = 18 dBi Gd BTS = 3.5 dB , then we can calculate the path loss as follows:

Lp = (Pout BTS - Lf BTS + Ga BTS + Gd BTS ) - Pin MS

Lp = 46-2.6+18+3.5-(-89.1)= 154 dB

Then the maximum allowed path loss is Lp is 154 dB and through which we are going to

calculate the cell range “d”

N.B:

d= Cell Range

Inter Site-distance =1.5d

Area ≈ 1.9 d2

d

d



Path Loss Lp

I. Free Space Model:

Theoretical Model not commonly used, it assumed Line Of Sight (LOS)

direct ray between the Transmitter and Receiver.

The Path Loss will be calculated as follows:

Lp = 32.44 + 20 log f (MHz) + 20 log d (Km), where f: frequency and

d:cell range

II. Two Path Model:

Assumes two paths: direct path and a ground reflected path.

It suits the road sites.

Lp = 20 log HBS + 20 log HMS +40 log d (Km) where d:cell range

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Path Loss Lp

III.Multi Path Propagation Model:

As stated before, the signal travelling in air will follow different paths

due to reflections from the surroundings where each individual path

affects the signal causing attenuation, delay and phase shift.

The received signals is therefore a result of direct rays, reflected rays

and shadowing or any combination of these signals.

Experimental measurements in different places led to the conclusion

that there is a necessity to make different models for different urban

environments having different civil structures: dense urban, urban,

suburban and rural.



Path Loss Lp

III.Multi Path Propagation Model: (A) Hata Okumura Model

Lp = A – 13.82 log HBS + (44.9-6.55 log HBS ) log d(km) – a (HMS )

HBS = Base Station antenna height

HMS = Mobile Station antenna height

d= Cell Range in Km

a(HMS)= 3.2(log 11.75HMS)2-4.97

Clutter Type Frequency Value of A

Dense Urban and Urban Areas

800 146.2

900 146.8

1800 153.8

1900 154.3

Sub Urban Areas

800 136.4

900 136.9

1800 146.2

1900 146.9

Rural Areas

800 127.1

900 127.5

1800 134.1

1900 134.6

Open Areas

800 117.9

900 118.3

1800 124.3

1900 124.8

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Path Loss Lp

III.Multi Path Propagation Model: (A) Hata Okumura Model

In our previous example for Urban clutter ( GSM 900MHz- band),

Lp=154 dB

Assuming HBS=35m and HMS=1.5m

Lp = A – 13.82 log HBS + (44.9-6.55 log HBS ) log d(km) – a (HMS )

Lp = 146.8 – 13.82 log 35 + (44.9-6.55 log 35 ) log d(km) – [ 3.2(log

11.75*1.5)2-4.97]

Lp = 146.8 – 21.34 + 34.786 log d(km) + ( 0.001)

Then log d(km) = 0.76 then d = 6.6 km

Hata Okumura’s mode doesn’t give accurate values with Dense Urban

and Urban areas when the typical cell radius is less than 1 km, so it is

used with rural and open areas only.



Path Loss Lp

III.Multi Path Propagation Model: (B) Walfish-Ikegami Model

Lp = K +38 log d + 18 log (HBS -17)

HBS = Base Station antenna height

d= Cell Range in Km

Concerning our previous example, in Urban clutter (GSM 900-Band), Lp=154 dB

Assuming HBS =35m, then

Lp = 143.2 + 38 log d + 18 log (35-17) = 154

Log d = - 0.3 then d = 0.5 Km = 500 m

Walfish-Ikegami Model is more suitable for estimating the cell range in

Dense Urban and Urban clutters.

Clutter Type Frequency Value of K

Dense Urban, Urban and Sub

Urban Areas

800 142.4

900 143.2

1800 153.2

1900 154.1

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Up Link Budget

• Now, we’re going to calculate the cell radius where the PinBTS will be

PinBTS = BTSsensitivity + RFmargin + IFmargin + BLmargin + LNFmarg(o)

Pout MS : Output power from the Mobile Station.

Lf BTS : Losses in Feeders, Jumpers and connectors

Ga BTS : BTS antenna gain Gd BTS : BTS antenna diversity gain

Lp : Path Loss Pin BTS : Input power at the Base Station

GTMA-UL : TMA UL gain

Pin BTS PoutMS

TMA

GTMA-UL



Up Link Budget

Example:

Given that: Pout MS = 33 dBm, Lf BTS = 2.6 dB, G TMA-UL = 4 dB ,

BTSsensitivity = -110 dBm, Ga BTS = 18 dBi Gd BTS = 3.5 dB , then we can calculate the

path loss as follows:

Lp = (Pout MS + G TMA-UL - Lf BTS + Ga BTS + Gd BTS ) – PinBTS

PinBTS = BTSsensitivity + RFmargin + IFmargin + BLmargin + LNFmarg(o)

= -110+3+2+5+4.9=-95.1

Lp = 33 + 4 – 2.6 + 18 + 3.5 – (-95.1) = 151 dB

Based on Walfish-Ikegami, we can calculate the maximum cell range on the

path loss calculated in the UL

Assuming HBS =35m, then

Lp = 143.2 + 38 log d + 18 log (35-17) = 151 dB

Log d = - 0.38 then d ~ 0.42 Km = 420 m

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Now

from downlink budget calculations dDL = 500m

while

from the uplink budget calculations dUL = 420m,

then we’re going to design on the lower value.



Power Balance

Now in order to guarantee that there is a power balance between the DL and the UL paths, we’ve to recalculate the BTS output power that will achieve this balance.

Lp = (Pout BTS - Lf BTS + Ga BTS + Gd BTS ) - Pin MS

Lp = Pout BTS - 2.6+18+3.5-(-89.1) = Pout BTS + 108 = 151 dB

Pout BTS = 43 dBm and this is the BTS o/p power for power balance.

DL Coverage

UL Coverage

If the DL and UL coverage are not balanced as in

figure, then in the shaded area in between, the MSs

will receive a good DL signal but their UL signal won’t

reach the BTS.

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Capacity Dimensioning

The Capacity in cellular system depends on:

The number of channels available.

The Grade Of Service (GOS) the subscribers are encountering in the

system

Traffic Theory attempts to obtain useful estimates, for example the number of

channels needed in a cell these estimates will depend on the selected system

and the assumed or real behavior of the subscribers.

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Traffic? Traffic refers to the usage of channels and is usually thought of as

the holding time per time unit.

Traffic: is measured in Erlangs (Er), a traffic of 1 Er means that this channel

was busy for 1 complete hour.

Traffic (Er) =

How much traffic can one cell carry?

This will depend on:

Number of traffic channels available.

Amount of congestion which is the GOS

Number of calls/hr X Average call holding time (Sec)

3600



Erlang-B table: is used to calculate how much traffic a cell can bear given

certain no. of Traffic Channels and certain GOS.

The Erlang-B table: was formed based on certain assumptions:

Poisson distribution (random) traffic

Blocked calls leave the call.

Example:

With a cell configured with 4 frequencies, then the number of available TCH

channels = 4*8 – 2 =30 TCHs, with GOS=2% then using Erlang-B we can

calculate the maximum traffic on this cell = 21.932 Er

If the average traffic/user = 30 mEr (i.e. average call/user = 108 seconds= 1.8

minutes) then at peak (busy) hour this cell can support 21.932/30m = 730 users

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Erlang B-Table

N.B:

The numerical

headings indicate

blocking probability %



Example:

If we have input from the marketing team that in a certain city each 100meters we’ll have

in the busy hour 150 users each will talk for 108 seconds = 1.8 minutes (i.e. each

user generates 30mE), calculate the cell range if each cell will be configured with 4

frequencies.

Solution:

For each cell, no. of TCHs = 4*8 – 2 =30 TCHs, with GOS=2% then using “Erlang-B

Table” we can find that each cell can bear up to 21.932 Er

But each user generates 30mE, then this cell can serve (21.9/30e-3) = 732

subscriber.

According to the user’s distribution, then each 100 m we have 150 subscriber, then

for each cell the 732 subscriber will be distributed on 100*(732/150) = 487 meters.

Distance

(meters)10

0

20

0

30

0

40

0

50

0

4.

5E

r

4.

5E

r

4.

5E

r

4.

5E

r

4.

5E

r0

d= 487m

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Channel Utilization (Trunking Efficiency)

One of the factors that should be taken into consideration in dimensioning,

and it shows how efficient the resources are utilized.

It is calculated as ηT = 100* (Traffic (Er) / No. of channels )

If we have an area generates a traffic of 20 Erlang, so under GOS=2% is

it better to use 1 cell or to split the traffic between 2 cell each of which to

carry 10 Er ?

• It is apparent from the above that using 1 cell will be more efficient than

splitting the traffic between 2 cells.

• For 1 cell to carry 20 Erlang with GOS=2%,

then no. of TCHs needed = 28, then we

should have at least 4 frequencies.

• 4 freq = 30 available TCHs

• Now Trunking efficiency

ηT = 100* (20/ 30) = 66.67%

• For 2 cells each to carry 10 Erlang with

GOS=2%, then no. of TCHs needed/cell = 17 ,

then we should have at least 3 frequencies.

• 3 freq/cell = 22 available TCHs/ cell, i.e. both

cells will have now 44 available TCHs

• Now Trunking efficiency

ηT = 100* (20/ 44) = 45.5 %



SDCCH Dimensioning

The load on the SDCCH channel is affected by:

Mobility Management procedures, that is, Normal Location Updating,

Periodic Registration and IMSI attach/detach.

Connection Management procedures, that is, Call set-up, SMSs.

The Typical GOS of SDCCH channel will depend either combined or non-

combined modes are used:

Non-Combined: GOS = 0.5% ( SDCCH/8)

Combined: GOS = 1% (SDCCH/4)

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SDCCH Dimensioning

Two models are used to estimate the SDCCH load

BAS1 Model: Typical model for SDCCH load estimations in average

network.

ERA5 Model: More aggressive model may be used when the subscribers

behavior in the network is not known.

The SDCCH load estimations, three types of cells are considered:

Border Cell (BC): Cell lies on a location area border and will be subjected

to heavy location updating.

Inner Cell (IC): Cell lies in the core of the location area and will never

subjected to location updating.

Average Cell (AC): Cell having average no. of location updating.



SDCCH Dimensioning

The SDCCH load estimations based on the two models can be seen as

below:

The 1st model:

BAS1 ModelEvent Average Cell Inner Cell Border Cell

Location Updating 0.5 0 1.5 mE/subscriber

IMSI Attach/detach 0.4 0.4 0.4 mE/subscriber

Periodic Registration 0.2 0.2 0.2 mE/subscriber

Call set-up 0.8 0.8 0.8 mE/subscriber

SMS 0.3 0.3 0.3 mE/subscriber

Total 2.2 1.7 3.2 mE/subscriber

20% Traffic Margin added 2.6 2 3.8 mE/subscriber

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SDCCH Dimensioning

The SDCCH load estimations based on the two models can be seen as

below:

The 2nd model:

ERA5 ModelEvent Average Cell Inner Cell Border Cell

Location Updating 1 0 3 mE/subscriber

IMSI Attach/detach 1.8 1.8 1.8 mE/subscriber

Periodic Registration 0.5 0.5 0.5 mE/subscriber

Call set-up 0.9 0.9 0.9 mE/subscriber

SMS 1.7 1.7 1.7 mE/subscriber

Total 5.9 4.9 7.9 mE/subscriber

20% Traffic Margin added 7.1 5.9 9.5 mE/subscriber


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Frequency Planning

A Cellular system is based upon reuse of the same set of carriers

(frequencies).

The same set of frequencies will be reused every cluster, where the cluster is

formed of defined no. of cells.

When applying certain frequency plan strategy, some issues should be taken

into consideration like: Available frequency spectrum, Subscribers distribution,

required Carrier to Interference ratio (C/I) and Carrier to Adjacent ratio (C/A).

It is recommended to keep C/I > 12 dB, while maintaining C/A > -3 dB

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Frequency Planning

Frequency Assignment Strategies

(I) Fixed Frequency Groups

(A)

4/12 Reuse

Pattern

(B)

3/9 Reuse

Pattern

(II) Multiple Reuse Pattern


Frequency Planning



It is the traditional way of assigning frequencies, it is accomplished by dividing

the frequency spectrum into groups each of which has the same no. of

frequencies and each cell will be assigned a certain group.

The advantage with this method is that once the BCCH plan is finished, all

other frequencies will be mapped in the same way.

The disadvantage is that it is not spectrum efficient and doesn’t make use of

the fact that not all cells have the same number of TRUs.

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Frequency Planning



(I-A) 4/12 Reuse Pattern

The Cluster will be formed of 4 Sites =12

cells on which the frequency spectrum

will be divided.

The cluster will be then repeated

every where all over the network.


Frequency Planning




Using this pattern then:

D= 3.46 R

– D= Reuse distance

– R= hexagon radius

C/I = 10log(D/R) 4 = 21.58 dB

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Frequency Planning




Example:

If the frequency spectrum is made up of 36 freq, then

what’ll be the distribution of these frequencies/cluster?

Strategy#1: Block Distribution

The frequency band will be divided into blocks

formed of consecutive frequencies, block for the

BCCH frequencies and block for the TCH frequencies.

Then we’ll form 12 groups each group will be

assigned to a cell within the cluster

( 1 BCCH freq. + 2 TCHs frequencies)

BCCH Block TCH Block 1 TCH Block 2

f1 f2 f3 f4 f5 f6 f7 f8 f9 f10f11f12f13f14f15f16f17f18f19f20f21f22f23f24f25f26f27f28f29f30f31f32f33f34f35f36


Frequency Planning





Cell A1: Group1 = f1(BCCH), f13(TCH1), f25(TCH2)

Cell B1: Group2 = f2(BCCH), f14(TCH1), f26(TCH2)

Cell C1: Group3 = f3(BCCH), f15(TCH1), f27(TCH2)

Cell D3: Group12 = f12(BCCH), f24(TCH1), f36(TCH2)

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12

f13 f14 f15 f16 f17 f18 f19 f20 f21 f22 f23 f24

f25 f26 f27 f28 f29 f30 f31 f32 f33 f34 f35 f36

Frequencies from the BCCH Block

Frequencies from TCH Block 1


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Frequency Planning




Strategy#2: Scattered Distribution

The frequencies assigned for both BCCH and TCH

bands will be chosen in a scattered manner and not as

block.



( 1 BCCH freq. + 2 TCHs frequencies)BCCH Frequencies

TCH Frequencies 1

TCH Frequencies 2


f1 f4 f7 f10f13f16f19f22f25f28f31f34f35 f2 f5 f8 f11f14f17f20f23f26f29f32f33f36 f3 f6 f9 f12f15f18f21f24f27f30

BCCH Frequencies TCH Frequencies 1 TCH Frequencies 2


Frequency Planning





Cell A1: Group1 = f1(BCCH), f35(TCH1), f33(TCH2)

Cell B1: Group2 = f4(BCCH), f2(TCH1), f36(TCH2)

Cell C1: Group3 = f7(BCCH), f5(TCH1), f3(TCH2)

Cell D3: Group12 = f34(BCCH), f32(TCH1), f30(TCH2)

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

f1 f4 f7 f10 f13 f16 f19 f22 f25 f28 f31 f34

f35 f2 f5 f8 f11 f14 f17 f20 f23 f26 f29 f32

f33 f36 f3 f6 f9 f12 f15 f18 f21 f24 f27 f30

BCCH Frequencies

TCH Frequencies 1

TCH Frequencies 2

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Frequency Planning




For this example whatever the strategy used either

Blocked or scattered, the no. of frequencies/cell = 3.

We can calculate the trunking efficiency as below:

No. of TCHs/Cell = (3*8 – 2 )= 22 Traffic channels,

with GOS=2% then Traffic = 14.9 Er

ηT = 100* (14.9/ 22) = 66.72%


Frequency Planning



(I-B) 3/9 Reuse Pattern

The Cluster will be formed of 3 Sites = 9 cells

on which the frequency spectrum will be divided.

The cluster will be then repeated every where

all over the network.

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Frequency Planning




Using this pattern then:

D= 3R

– D= Reuse distance

– R= hexagon radius

C/I = 10log(D/R) 4 = 19.1 dB


Frequency Planning




Example:

If the frequency spectrum is made up of 36 freq,

then what’ll be the distribution of these frequencies/Cluster?


The frequency band will be divided into blocks

formed of consecutive frequencies, block for the BCCH

frequencies and block for the TCH frequencies.



( 1 BCCH freq. + 3 TCHs frequencies)



TCH Block 3

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Frequency Planning





Cell A1: Group1 = f1(BCCH), f10TCH1), f19(TCH2), f28(TCH3)

Cell B1: Group2 = f2 (BCCH), f11(TCH1), f20(TCH2), f29(TCH3)

Cell C1: Group3 = f3(BCCH), f12(TCH1), f21(TCH2), f30(TCH3)

Cell C3: Group9 = f9 (BCCH), f18(TCH1), f27(TCH2), f36(TCH3)

A1 B1 C1 A2 B2 C2 A3 B3 C3

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18

19 20 21 22 23 24 25 26 27

28 29 30 31 32 33 34 35 36

Frequencies from the BCCH Block





Frequency Planning





The frequencies assigned for both BCCH and TCH bands

will be chosen in a scattered manner and not as block.

Then we’ll form 9 groups each group will be assigned to a

cell within the cluster ( 1 BCCH freq. + 3 TCHs frequencies)


BCCH Frequencies

TCH Frequencies 1

TCH Frequencies 2

TCH Frequencies 3

f1 f5 f9 f13f17f21f25f29f33f34 f2 f6 f10f14f18f22f26f30f31f35 f3 f7 f11f15f19f23f27f28f32f36 f4 f8 f12f16f20f24

TCH Block 3


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Frequency Planning





Cell A1: Group1 = f1(BCCH), f34(TCH1), f31(TCH2), f28(TCH3)

Cell B1: Group2 = f5(BCCH), f2(TCH1), f35(TCH2), f32(TCH3)



A1 B1 C1 A2 B2 C2 A3 B3 C3

f1 f5 f9 f13 f17 f21 f25 f29 f33

f34 f2 f6 f10 f14 f18 f22 f26 f30

f31 f35 f3 f7 f11 f15 f19 f23 f27

f28 f32 f36 f4 f8 f12 f16 f20 f24

BCCH Frequencies

TCH Frequencies 1

TCH Frequencies 2

TCH Frequencies 3


Frequency Planning




For this example whatever the strategy used either

Blocked or scattered, the no. of frequencies/cell = 4.

We can calculate the trunking efficiency as below:

No. of TCHs/Cell = (4*8 – 2 )= 30 Traffic channels,

with GOS=2% then Traffic = 21.93 Er

ηT = 100* (21.93/ 30) = 73.1%

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Frequency Planning



It is more spectrum efficient than fixed frequency groups for non-uniform

configurations.

The frequency assignment is done according to layered frequency planning

where each band is individually planned.

That is due to the fact that the load on each cell differs according to the

serving area.


Frequency Planning



Assume a frequency bandwidth of 7.2MHz (36 frequency) and configuration

with maximum 4 frequencies per cell is allowed.

The frequencies are then divided into four bands, one band for the BCCH

frequencies and three bands for the TCH frequencies as below:

12 BCCH FrequenciesBCCH Frequencies

f1 f3 f5 f7 f9 f11 f13 f15 f17 f19 f21 f23

10 TCH Frequencies in the 1st TCH band

TCH Frequencies 2

f22 f24 f26 f28 f30 f32 f34 f368 TCH Frequencies in the 2nd TCH band

TCH Frequencies 3

f25 f27 f29 f31 f33 f356 TCH Frequencies in the 3rd TCH band

TCH Frequencies 1

f2 f4 f6 f8 f10 f12 f14 f16 f18 f20

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Frequency Planning



Assume that cell A is serving in an area where high traffic is expected, while

cell B is serving in a normal traffic area.

The frequency allocation for both cells may be as below:

Cell A: f1 (BCCH), f6 (1st TCH Band), f22 (2nd TCH Band), f25 (3rd TCH Band)

Cell B: f3 (BCCH), f8 (1st TCH Band)

It can be seen that cells won’t experience the same frequency reuse pattern

as each of which is configured with different no. of TRXs.

A

CB


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