Selfish Misbehavior in Wireless Networks Nitin Vaidya University of Illinois at Urbana-Champaign www.crhc.uiuc.edu/wireless

Increasing Wireless Deployment in Unlicensed Bands Hot-spots Community wireless networks Home networks Sensors …

Users Must Trust the Network “Wired-equivalent” privacy mechanisms Going beyond privacy … Users must be able to rely on “ fair ” competition

} } Unlicensed Bands The New Wild Wild West ? Increasing demand Limited resources Few rules ! Increasingly programmable devices } Incentive for misbehavior } Tools for misbehavior

Impact of Selfish Misbehavior Benefits misbehaving users, at the cost of others Reduces trustworthiness of the network Analogy : Speeding on the highways

Examples of Misbehavior Misbehavior can occur at all layers of the protocol stack

Example: Physical Layer Using unnecessarily high transmit power

Example: Medium Access Control Layer 802.11 a wait-before-you-talk protocol By waiting less than recommended, misbehaving users benefit

Example: Network Layer In mesh networks, misbehaving users may use their links only when convenient to self

Selfish Misbehavior Not unique to wireless networks But … TCP misbehaviors identified in the past But … Wireless brings new challenges Misbehavior more likely in wireless networks due to limited resources

Fundamental Challenges Wireless channel varies over space & time Impossible to detect misbehavior with 100% accuracy How to do “well enough” ? What are the limits on accuracy ?

Fundamental Challenges Misbehavior cannot always be handled at the layer at which it occurs Cross-layer detection & response

Fundamental Challenges Different protocols must co-exist on same slice of wireless spectrum Different protocols don’t necessarily know each other

Research Agenda A Civil Wireless Society Protocol mechanisms to Deter, Detect and Penalize misbehaviors, and Encourage Cooperation Layer-based classification of misbehaviors Determine fundamental limits

Thanks! www.crhc.uiuc.edu/wireless