Collaborative Spectrum Management for Reliability and Scalability

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Collaborative Spectrum Management for
Reliability and Scalability

• Heather Zheng
• Dept. of Computer Science
• University of California, Santa Barbara

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The Critical Need for Dynamic Spectrum Management

• Explosion of wireless networks and devices
• Static spectrum assignments are inefficient
• Under-utilization over-allocation
• Artificial spectrum scarcity
• Solution Migrate from long-term static spectrum
  assignment to dynamic spectrum access

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Challenges Facing DSA

• Dynamic, Heterogeneous Spectrum Demand

• Dynamic, Heterogeneous Spectrum Availability

Large number of nodes
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Requirements for DSA

• Scalability and speed
• Support a large number of nodes
• Adapt to time-varying demands
• Efficiency Fairness
• Maximize spectrum utilization
• Avoid conflict
• Reliability
• Provide QoS
• Minimize outages

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A Few Observations
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Collaborative Spectrum Allocation
Goal Allocate spectrum to maximize system
utility Assumption 100 willingness to
collaborate
Node Collaboration

• Action Iterative Explicit Coordination
• Self-organize into coordination groups
• Negotiate to allocate spectrum in each group
• Iteratively set up groups to improve utility
• Fast convergence coordination stops when no
  local improvement can improve utility

Cao Zheng, SECON 2005, Crowncom07, JSAC08,
MONET08
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Analytical Properties
Fast Convergence The system converges after at
most O(N2) local adjustments, N network size
Node Collaboration
Cao Zheng, SECON 2005
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Tightness of Poverty Line
Percentage of Instances
A(n)/PL(n)
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Bandwidth-Aware Poverty Line

• Each channel i has a weight of Bi(n)
• Each nodes spectrum allocation
• A(n) ? ai(n)Bi(n)
• Extended poverty line
• A(n) gt PL(n)

Cao Zheng, Crowncom07
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Traffic-Aware Poverty Line

• Each infrastructure node n supports tn users
• Maximize end-user fairness
• Each infrastructure nodes spectrum has a lower
  bound

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Making it Work in Practice Distributed
Coordination Protocol

• Poverty line is an integrated knowledge about
  spectrum sharing
• Use it to initiate coordination
• Enable multiple parallel coordination events
• Minimize adaptation delay

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Simulations Coordination Delay
of Local coordination scales linearly with the
of APs
Adaptation delay flattens out because of
parallelism.
1Mbps Wireless Backhaul running CSMA/CA among APs
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Rule Regulated Spectrum Allocation
Goal Allocate spectrum to maximize system
utility Assumption comply to rules, no
handshaking
Implicit Coordination

• Action Iterative Independent adjustments
• Nodes observe spectrum usage in proximity
• Independently adjust self spectrum usage
• Regulated by predefined rules

The same analytical Poverty Line Bounds and O(N2)
complexity
Zheng Cao, DySPAN 2005 JSAC 2008
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Required Hardware Functionality

• Conflict Detection
• Explicit coordination ? A control path among
  conflicting peers
• Implicit coordination ? Sophisticated
  environmental sensing module
• Non-contiguous spectrum usage
• Behavior enforcement

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From Adaptation to Reliability
See Lili Caos Poster Tomorrow
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Lessons Learned

• Much of large-scale distributed wireless systems
  depend on mutual cooperation
• To build robust systems that can be deployed in
  real life, we need to be flexible in our design
  to allow for flexible levels of cooperation
• Hybrid architecture helps to provide reliability
• Controlled regulation at a coarse time-scale
• Individual adaptation at a fine time-scale
• Interference makes it very challenging
• Current Simplification via conflict graph
• Future Addressing physical interference
  constraints