176 research outputs found
Random Access Game and Medium Access Control Design
Motivated partially by a control-theoretic viewpoint, we propose a game-theoretic model, called random access game, for contention control. We characterize Nash equilibria of random access games, study their dynamics, and propose distributed algorithms (strategy evolutions) to achieve Nash equilibria. This provides a general analytical framework that is capable of modeling a large class of system-wide quality-of-service (QoS) models via the specification of per-node utility functions, in which system-wide fairness or service differentiation can be achieved in a distributed manner as long as each node executes a contention resolution algorithm that is designed to achieve the Nash equilibrium. We thus propose a novel medium access method derived from carrier sense multiple access/collision avoidance (CSMA/CA) according to distributed strategy update mechanism achieving the Nash equilibrium of random access game. We present a concrete medium access method that adapts to a continuous contention measure called conditional collision probability, stabilizes the network into a steady state that achieves optimal throughput with targeted fairness (or service differentiation), and can decouple contention control from handling failed transmissions. In addition to guiding medium access control design, the random access game model also provides an analytical framework to understand equilibrium and dynamic properties of different medium access protocols
MAC design for WiFi infrastructure networks: a game-theoretic approach
In WiFi networks, mobile nodes compete for accessing a shared channel by
means of a random access protocol called Distributed Coordination Function
(DCF). Although this protocol is in principle fair, since all the stations have
the same probability to transmit on the channel, it has been shown that unfair
behaviors may emerge in actual networking scenarios because of non-standard
configurations of the nodes. Due to the proliferation of open source drivers
and programmable cards, enabling an easy customization of the channel access
policies, we propose a game-theoretic analysis of random access schemes.
Assuming that each node is rational and implements a best response strategy, we
show that efficient equilibria conditions can be reached when stations are
interested in both uploading and downloading traffic. More interesting, these
equilibria are reached when all the stations play the same strategy, thus
guaranteeing a fair resource sharing. When stations are interested in upload
traffic only, we also propose a mechanism design, based on an artificial
dropping of layer-2 acknowledgments, to force desired equilibria. Finally, we
propose and evaluate some simple DCF extensions for practically implementing
our theoretical findings.Comment: under review on IEEE Transaction on wireless communication
Real-Time Misbehavior Detection in IEEE 802.11e Based WLANs
The Enhanced Distributed Channel Access (EDCA) specification in the IEEE
802.11e standard supports heterogeneous backoff parameters and arbitration
inter-frame space (AIFS), which makes a selfish node easy to manipulate these
parameters and misbehave. In this case, the network-wide fairness cannot be
achieved any longer. Many existing misbehavior detectors, primarily designed
for legacy IEEE 802.11 networks, become inapplicable in such a heterogeneous
network configuration. In this paper, we propose a novel real-time hybrid-share
(HS) misbehavior detector for IEEE 802.11e based wireless local area networks
(WLANs). The detector keeps updating its state based on every successful
transmission and makes detection decisions by comparing its state with a
threshold. We develop mathematical analysis of the detector performance in
terms of both false positive rate and average detection rate. Numerical results
show that the proposed detector can effectively detect both contention window
based and AIFS based misbehavior with only a short detection window.Comment: Accepted to IEEE Globecom 201
A Game Theory based Contention Window Adjustment for IEEE 802.11 under Heavy Load
The 802.11 families are considered as the most applicable set of standards for Wireless Local Area Networks (WLANs) where nodes make access to the wireless media using random access techniques. In such networks, each node adjusts its contention window to the minimum size irrespective of the number of competing nodes, so in saturated mode and excessive number of nodes available, the network performance is reduced due to severe collision probability. A cooperative game is being proposed to adjust the users’ contention windows in improving the network throughput, delay and packet drop ratio under heavy traffic load circumstances. The system’s performance evaluated by simulations indicate some superiorities of the proposed method over 802.11-DCF (Distribute Coordinate Function)
Protecting 802.11-Based Wireless Networks From SCTS and JACK Attacks
The convenience of IEEE 802.11-based wireless access networks has led to widespread deployment. However, these applications are predicated on the assumption of availability and confidentiality. Error-prone wireless networks afford an attacker considerable flexibility to exploit the vulnerabilities of 802.11-based mechanism. Two of most famous misbehaviors are selfish and malicious attacks. In this thesis we investigate two attacks: Spurious CTS attack (SCTS) and Jamming ACK attack (JACK). In the SCTS, malicious nodes may send periodic Spurious CTS packets to force other nodes to update their NAV values and prevent them from using the channel. In the JACK, an attacker ruins legitimate ACK packets for the intention of disrupting the traffic flow and draining the battery energy of victim nodes quickly. Correspondingly, we propose solutions: termed Carrier Sensing based Discarding (CSD), and Extended Network Allocation Vector (ENAV) scheme. We further demonstrate the performance of our proposed schemes through analysis and NS2 simulations
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