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April 24, 2023 1
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