Cellular Network Plaaning
Cellular Network Planning and Optimization
Part II: Fading
Jyri Hämäläinen,
Communications and Networking Department,
TKK, 17.1.2007
Outline
Modeling approaches
Path loss models
Shadow fading
Fast fading
2
Modeling approaches
3
Fading seen by moving terminal
Fast fading
Power
Modeling approach:
+20 dB
1. Distance between
TX and RX => path loss
2. Shadowing by large obstacles => shadow fading
3. Multi-path effects
=> fast fading - 20 dB
Path loss
Lognormal fading Path loss
Time
4
Path Loss
Path loss is distance dependent mean attenuation of the signal.
Once the allowed path loss of a certain system is known we can solve the maximum distance between transmitter and receiver and compute the relative coverage area.
Suitable path loss model depends on the environments (macro-cell, micro-cell, indoor)
Outdoor to outdoor models
Outdoor to indoor models
Indoor models
5
Shadow Fading
Shadow fading is used to model variations in path loss due to large obstacles like buildings, terrain conditions, trees.
Shadow fading is also called as log-normal fading since it is modeled using log-normal distribution In cell dimensioning/link budget shadow fading is taken into account through a certain margin
(=shadow fading margin)
6
Path loss + shadow fading
Signal strength in dB’s
Log-normal distribution
Path loss
Standard deviation e.g. +/-8 dB
Distance between TX and RX in logarithmic scale
7
Fast Fading
Fast fading is also called as multi-path fading since it is mainly caused by multi-path reflections of a transmitted waves by local scatterers such as human build structures or natural obstacles
Fast fading occurs since MS and/or scatterers nearby MS are moving
Signal strength in the receiver may change even tens of decibels within a very short time frame
Signal coherence distance = separation between locations where fast fading correlation is negligible. Signal
Part II: Fading
Jyri Hämäläinen,
Communications and Networking Department,
TKK, 17.1.2007
Outline
Modeling approaches
Path loss models
Shadow fading
Fast fading
2
Modeling approaches
3
Fading seen by moving terminal
Fast fading
Power
Modeling approach:
+20 dB
1. Distance between
TX and RX => path loss
2. Shadowing by large obstacles => shadow fading
3. Multi-path effects
=> fast fading - 20 dB
Path loss
Lognormal fading Path loss
Time
4
Path Loss
Path loss is distance dependent mean attenuation of the signal.
Once the allowed path loss of a certain system is known we can solve the maximum distance between transmitter and receiver and compute the relative coverage area.
Suitable path loss model depends on the environments (macro-cell, micro-cell, indoor)
Outdoor to outdoor models
Outdoor to indoor models
Indoor models
5
Shadow Fading
Shadow fading is used to model variations in path loss due to large obstacles like buildings, terrain conditions, trees.
Shadow fading is also called as log-normal fading since it is modeled using log-normal distribution In cell dimensioning/link budget shadow fading is taken into account through a certain margin
(=shadow fading margin)
6
Path loss + shadow fading
Signal strength in dB’s
Log-normal distribution
Path loss
Standard deviation e.g. +/-8 dB
Distance between TX and RX in logarithmic scale
7
Fast Fading
Fast fading is also called as multi-path fading since it is mainly caused by multi-path reflections of a transmitted waves by local scatterers such as human build structures or natural obstacles
Fast fading occurs since MS and/or scatterers nearby MS are moving
Signal strength in the receiver may change even tens of decibels within a very short time frame
Signal coherence distance = separation between locations where fast fading correlation is negligible. Signal