Self-Organizing Coalitions for Conflict Evaluation
and Resolution in Femtocells
Luis G. U. Garcia, Aalborg University
Gustavo W. O. da Costa, Aalborg University
Andrea F. Cattoni, Aalborg University
Klaus I. Pedersen, Nokia Siemens Networks
Preben E. Mogensen, Aalborg University, Nokia Siemens Networks
Outline
Problem and solution overview
Supporting concepts
Coalition formation rules
Simulation scenario and results
Conclusions
Frequency planning / spectrum usage in cellular
networks
Past
Large macrocells
with sparse
planned reuse
Current
Small macrocells
with tight
planned reuse (1)
Future
Heterogeneous
networks including
uncoordinated
femtocell deployment
Problem:
• Massive number of femtocells  planning and optimization is too costly.
• High interference possible due to dense deployment and random HeNB
and UE locations.
Proposed Solution: Dynamic spectrum sharing using carrier aggregation.
Proposed framework
Low load – First-come, First served
High load – Self-Organizing Coalitions for Conflict Evaluation and
Resolution (SOCCER)
SOCCER in a nutshell
•
•
•
•
•
•
Distributed dynamic method for spectrum sharing amongst
femtocells  no need for planning. Self-optimizing.
Measurements determine incoming and outgoing SINR (BIM)
Evaluation of system capacity for different options (reuse/orthogonal
allocation).
Six simple rules for formation of coalitions and redistribution of
resources (component carriers) on efficient and fair way.
Enabler: low capacity HeNB to HeNB communication link, as
typically assumed for ACCS.
Avoid reconfiguration storms: everything solved locally.
Outline
Problem and solution overview
Supporting concepts
Coalition formation rules
Simulation scenario and results
Conclusions
Evaluation of coalitions
Pair wise evaluation, based on sum system capacity
SINR
Cell A
Orthogonal
is better
Reuse is
better
SINR
Cell B
Strong interference bonding condition
Ccoalition ( A)  Ccoalition ( B)  Creuse1( A)  Creuse1( B)
Strong Interference Bonding Graph
Clique 2
Maximal
Clique-3
Maximal clique sizes define the optimal local frequency reuse!
Outline
Problem and solution overview
Supporting concepts
Coalition formation rules
Simulation scenario and results
Conclusions
Coalition formation rules
A coalition is a bilateral mutual agreement of having an
orthogonal allocation.
New coalitions are formed when HeNB needs more
spectrum.
Optimized method for maximal cliques up to size 3  only 6
simple formation rules.
CFR
CFA
Coalition formation
Outline
Problem and solution overview
Supporting concepts
Coalition formation rules
Simulation scenario and results
Conclusions
Dual stripe, 6 floors, 40 apartments per floor *
Simulated scenario
25% and 75% deployment ratio
* 3GPP RAN 4, “Simulation assumptions and parameters for FDD HeNB
RF requirements,” Tech. Rep. R4-092042, May 2009.
What is the maximal clique distribution on this
scenario?
25% deployment
ratio
75% deployment
ratio
Normalized Throughput at 25% deployment ratio
Normalized Throughput at 75% deployment ratio
Outline
Problem and solution overview
Supporting concepts
Coalition formation rules
Simulation scenario and results
Conclusions
Conclusions
Femtocell deployment should rely on self-organizing
spectrum allocation
Proposal
• At low traffic load  simple threshold based selection.
• At high traffic load  interference management using coalitions
(SOCCER).
SOCCER has a lot of potential to become practical
• Simple
• Very effective method
• Based on standardized measurements
Applicable to LTE-Advanced as well as other systems