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IQBri Telecomurge your potential

RF Planning

Module 4

1

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Contents

2

What is planning

Steps For Planning

Network Requirement

Nominal Cell Plan

Capacity planning

Dimensioning Frequency Planning

Interference and its types

Frequency Hopping

Combinations of Control Channels

RF Survey

Detailed network design

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RF Planning

3

What is planning ?

• Planning of radio frequency network.

• Deciding number and location of BTS/BSC.

• Deciding the Radio Parameters.

• Transmission link for backhaul connectivity.

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RF Planning

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Steps for Planning

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RF Planning

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Geographical

• Distribution of traffic demand can be calculated

by using demographic data such as:

• Population distribution

• Income level distribution

• Telephone usage statistics

• Other factors such as subscription charges, call

charges, and price of mobile stations

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RF Planning

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Objectives of RF Planning

• Adequate coverage

• Traffic handling capacity

• Quality of Service (QOS)

• Network growth accommodation

• Cost effective design

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Components of RF Planning

RF Planning

• Capacity planning

• Coverage planning

• Parameter planning

• Equipment planning

• Optimization

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Initial Cell Planning

• Objective: Creating a Nominal Cell Plan

• Calculating number of sites and

distribution required to meet coveragerequirement.

• Assessment of available site locations.

• Locating the nominal sites.

• Making coverage predictions.

RF Planning

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• Obtain Digitised Terrain Maps (DTM’s)

• Prepare link budgets

• Make use of a Planning Tool

• Get Coverage Plots

Detailed Cell Planning

RF Planning

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RF Planning

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Calculating Number of Sites - Capacity

• Traffic offered from each configuration- Required input data:

• Traffic per subscriber : e.g. 25 mE/sub.• GoS (Grade of Service) e.g. 2% at air interface.• number of TCHs available for each carrierconfiguration, for example:

-7 TCHs for 1 carrier configuration-14 TCHs for 2 carrier configuration-22 TCHs for 3 carrier configuration

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RF Planning

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Excerpts from Erlang B Table

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Capacity Considerations - I

1

1With 2 % GoS

21 1

2.94 E

2.94E/25mE=120 Subs8

8 Access Channels

1 --Signaling

7- Voice

120 Subs/Sector 3 = 360 Subscribers

RF Planning

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Capacity Considerations - II

1 2 4

1 1 2 2 4 4

8 Access Channels 16 Access Chls 32 Access Chls1--Signaling 2—Signaling 3--Signaling

7- Voice 14- Voice 29- Voice

120 3 = 360 Subs 330 3 = 1000Subs

840 3 = 2520 Subs

RF Planning

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RF Planning

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Frequency Planning Principle

• The frequency spacing between the BCCH and TCH must be

greater than 400 KHz within a cell.

• The frequency spacing between the TCHs must be greater

than 400 KHz within a cell.

• The adjacent base stations cannot use the same frequency.

• The adjacent areas are not allowed to share the BCCH and

the BSIC.

• Must apply the 4 x 3 frequency reuse pattern to the BCCH

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RF Planning

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RF Planning

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• However, the drawbacks of this frequency reuse pattern are

that the frequency reuse ratio is low and the capacity

expansion needs a great amount of the frequency resources.

Therefore, this reuse pattern is not used in the areas where

the network capacity needs to be constantly expanded.

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RF Planning

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Nominal cell plan

• Graphical representation of

the network

• Looks like a cell pattern on

a map.

• Coverage and interference

predictions is also done

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RF Planning

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Nominal cell plan

• Capacity related

• Spectrum available.

• Subscriber growth forecast

• Traffic density map (Traffic per subs)

• Coverage related

• Coverage regions

• Area type’s information

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RF Planning

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Capacity calculation

• The capacity of a given network is measured in terms of the subscribers orthe traffic load that it can handle. The former requires knowledge ofsubscriber calling habits (average traffic per subscriber) while the latter ismore general. In general trend average traffic per user is taken near

30mErl. The steps for calculating the network capacity are• Erlang B table

• To calculate the capacity of the given cell using blocking probability (that istaken as 2%) and the number of carriers we need the well-known Erlang Btable or formulas and the number of traffic channels. The result we get isthe traffic capacity in Erlangs, which can easily be transferred into the

number of subscribers.• Erlangs = no of calls attempted in busy hour * average duration in seconds

/ 3600

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RF Planning

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Site Survey

• Important topics to consider during evaluation:

- Coverage objectives (site locations)

- Antenna Mounting (obstructions, etc)

- Feeder Length (feeder cable loss)- Equipment room (size and location)

- Cable ducts / Antenna masts (construction)

- Transmission Links (Microwave, fixed line)

- Construction Cost (alternative solutions)

- Relationship to other sites (handover, etc)

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IQBri Telecom 25

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