On Stochastic Modeling and Analysis of
Femtocell Networks
Wireless Communications Research Seminar 2012, February 16th
Carlos Lima
LOCON - Local connectivity and cross layer design for future broadband mobile systems
Introduction (1/2)
Putting into context…
• Short-range communications provide better link quality and higher spectral efficiency [1, 2]
• Unplanned deployment and uncoordinated operation cause harsh Co-Channel Interference (CCI) [3]
• Self-configuration and (re)organization of femtocells
[1] H. Claussen, L. Ho, and L. Samuel, “An overview of the femtocell concept,” Bell Labs
Tech. Journal, vol. 13, no. 1, pp. 221–245, 2008.
[2] V. Chandrasekhar, J. G. Andrews, and A. Gatherer, “Femtocell networks: a survey,”
IEEE Commun. Mag., vol. 46, no. 9, pp. 59–67, Sep. 2008.
[3] D. Lopez-Perez, A. Valcarce, G. de la Roche, and J. Zhang, “OFDMA femtocells: A
roadmap on interference avoidance,” IEEE Commun. Mag., vol. 47, no. 9, pp. 41–48,
Jun. 2009.
Introduction (2/2)
Putting into context…
• Practical deployment scenarios
• Network dynamics and channel variations
• Characterize the received signal and CCI
distribution
• Analytical framework based on Stochastic
Geometry (SG) and Higher-Order
Statistics (HOS)
Stochastic Framework (1/4)
Stochastic Geometry: Key words [1]
• Poisson process with constant intensity
• Slivnyak’s Theorem and Palm probability
• Campbell Theorem
• Marking Theorem
[1] D. Stoyan, W. S. Kendall, and J. Mecke, Stochastic Geometry and Its
Applications, 2nd ed. Wiley-Blackwell, 1995
Stochastic Framework (2/4)
Higher Order Statistics
• Cumulants concept
• Properties (additivity)
Stochastic Framework (3/4)
Approximations
• There’s no general closed-form expression for the PDF of the sum of log-normal RVs
• Positively skewed
• Case study: LN, SLN Approximations
• Are there any other alternatives?
Stochastic Framework (4/4)
Performance Evaluation
• SIR interference limited scenarios
• Outage probability
• Average spectral efficiency
Case Study: CM (1/10)
System Model
• Path loss attenuation with large- and
small-scale fading
• Shadowed fading channel [1]
• MPP
[1] M.-J. Ho and G. L. Stuber,
“Capacity and power control for
CDMA microcells,” ACM Journal
on Wireless Networks, vol. 1, no.
3, pp. 355–363, Oct. 1995.
F B S 1
F B S 2
F B S 3
F B S 4
F U 1
F U 2
F U 3
F U 4
M B S
M U
t ag
ged
l i nk
Case Study: CM (2/10)
Solution Description
Detecting
Non-detecting
Tagged receiver
Case Study: CM (3/10)
Solution Description
• Detection event
• Coordination
regions
Case Study: CM (4/10)
Uncoordinated Scenarios
• Full Interference activity
Case Study: CM (5/10)
Uncoordinated Scenarios
• Full Interference + PC Transmit power
Case Study: CM (6/10)
Coordinated Scenarios
• PC with discrete power levels Detecting femtos
Case Study: CM (7/10)
Coordinated Scenarios
• Dynamic Exclusion Regions (DER)
Exclusion region
Case Study: CM (8/10)
Coordinated Scenarios
• DER + PC Exclusion region
Power control
Case Study: CM (9/10)
Approximation
m=16 m=2
Case Study: CM (10/10)
Numerical Results
What’s next?
• Large DAS Vs. Massive MIMO
• Traffic effect
• Area spectral efficiency
• Cluster process
