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Mobile Computing COE 446

Network PlanningTarek Sheltami

KFUPMCCSECOE

http://faculty.kfupm.edu.sa/coe/tarek/coe446.htm

Principles of Wireless NetworksK. Pahlavan and P. Krishnamurth

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Outline Signal to interference ratio calculation Capacity expansion techniques

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Signal-to-Interference Ratio Calculation

The objective in a cellular radio system is to allocate the channels to cell within a cluster so that the distance between cochannels or adjacent channels is as large as possible

For urban land mobile ratio, the distance is power gradient is roughly 4

The received signal strength falls as the fourth power distance

This further improves Sr

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Signal-to-Interference Ratio Calculation..

If there are Js interfering BS surrounding a given BS then:

Where d0: the distance of MT from a given BS and dn is the distance from the nth BS

s

0r J

nn 1

dS

d

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Sr as a function of frequency reuse factor, N

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Signal-to-Interference Ratio Calculation..

Assuming that received signal falls as the fourth of the distance from land mobile radio, the path loss model will be:Pr(d) dB = Pt(dB) – (40 log d + 10 log K)

The factor 10 log K usually corresponds to the path loss at the first meter or kilometer, d is the distance

This model is appropriate for first cut approximations in system design

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Capacity Expansion Techniques There are four methods:1. Obtain additional spectrum to new MTs

Very simple, but expensive2. Expand the capacity of a cellular network to change the

cellular architecture: This includes cell splitting, cell sectoring using

directional antennas (Lee microcell zone technique) and using multiple reuse factors

These techniques do not need additional spectrum or any major changes in wireless modem or access techniques

One of the most practical and less expensive solutions to expand the network capacity

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Capacity Expansion Techniques..3. Change the frequency allocation methodology:

Non uniform distribution of the frequency bands among different cells according to their traffic need

Traffic load of each cell is dynamically changed by the geography of the service area with time depending of the traffic load

These techniques do not need any change in MTs or physical architecture of the system

4. Expand the network capacity by changing modem and access technology: The most effective method

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Capacity Expansion Techniques.. Cell industry started with analog FM

modulation then TDMA and it is going to CDMA air interface using digital modems

Digital technology increases the network capacity and also provides a fertile environment for integration of voice and data services

This migration requires the user to purchase new MT and provider to install new components in the infrastructure