Cognitive Radio Network (CRN) is one of the prominent communication technologies that is touted to drive the next generations of digital communications. In this paper, we address the vulnerabilities in such networks and analyze a common form of the Denial-of-Service attack, i.e., collaborative jamming. In particular, we model and analyze the channel availability when different jamming and defending schemes are employed by the attackers and legitimate users. Cooperative defense strategy is proposed to exploit the temporal and spatial diversity for the legitimate secondary users. Illustrative results show how to improve the resiliency in CRN against jamming attacks.

In a distributed wireless system, multiple network nodes behave cooperatively towards a common goal. An important challenge in such a scenario is to attain mutual cooperation. This paper provides a non-cooperative game theoretic solution to enforce cooperation in wireless networks in the presence of channel noise. We focus on one-hop information exchange and model the packet forwarding process as a hidden action game with imperfect private monitoring. We propose a state machine based strategy to reach Nash Equilibrium. The equilibrium is proved to be a sequential one with carefully designed system parameters. Furthermore, we extend our discussion to a general wireless network scenario by considering how cooperation can prevail over collusion using evolutionary game theory. The simulation results are provided to back our analysis. In particular, network throughput performance is measured with respect to parameters like channel loss probability, route hop count, and mobility. Results suggest that the performance due to our proposed strategy is in close agreement with that of unconditionally cooperative nodes. Simulation results also reveal how the convergence of cooperation enforcement is affected by initial population share and channel unreliability.

Identification and isolation of attackers in a distributed system is a challenging problem. This problem is even more aggravated in a wireless network because the unreliable channel makes the actions of the users (nodes) hidden from each other. Therefore, legitimate users can only construct a belief about a potential attacker through monitoring and observation. In this paper, we use game theory to study the interactions between regular and attacker nodes in a wireless network. We model the attacker node detection process as a Bayesian game with imperfect information and show that a mixed strategy perfect Bayesian Nash Equilibrium is attainable. Further, we show how an attacker node can construct a nested belief system to predict the belief held by a regular node. By employing the nested belief system, a Markov Perfect Bayes-Nash Equilibrium is reached and the equilibrium postpones the detection of the attacker node. Simulation results and their discussions are provided to illustrate the properties of the derived equilibria.

An underlying assumption of multi-hop data communication in ad hoc networks is that the nodes forward each others' packets. An important challenge in such scenario is to attain mutual cooperation. This paper provides a game theoretic solution to enforce cooperation in ad hoc network in the presence of channel noise. We focus on the packet forwarding process and model it as a hidden action game with imperfect private monitoring. We propose a state machine based strategy to reach Nash Equilibrium. The equilibrium is proved to be a sequential equilibrium with carefully designed system parameters. Furthermore, we extend our discussion to a general ad hoc network scenario by refining the strategy profiles to handle multi-hop packet forwarding. The simulation results illustrate the efficiency of the proposed forwarding strategies. In addition, network throughput performance is measured with respect to parameters like channel loss probability, route hop count and mobility. Results suggest that the performance due to our proposed strategy is in close agreement with that of unconditionally cooperative nodes.

An inherent assumption for packet forwarding in ad hoc networks is that the nodes will cooperate i.e., nodes can rely in each other. Thus, it is extremely important that cooperation is induced and achieved in the network. In this paper, we use game theory to analyze the necessary and sufficient conditions to enforce cooperation enforced, especially when a node cannot perfectly monitor other nodespsila behaviors. We analyze a credit exchange method under a general unreliable channel and show that the packet forwarding probability can be adjusted through proper design of incentives, which in turn can be used to attain the desired Nash Equilibrium. We extend our discussion to repeated games and take several well-known strategy profiles and derive the conditions under which the cooperation can lead to a subgame perfect Nash equilibrium. In particular, we show how the unreliable channel can affect the conditions and how a reputation based strategy leads to subgame perfection even under imperfect monitoring. We further investigate collusion resistance and cooperation coalition formation using evolutionary game theory. Mathematical proofs show the existence of an upper bound on the population share of the non-cooperative nodes for an evolutionarily non-stable strategy that enforces full cooperation. This bound is shown to depend on the nodespsila belief on the continuity of the game.

An interesting feature of the 3G cellular networks is their ability to support multiple data rates. Though the performance of TCP over wireless networks has been well studied, there is still no clear understanding on the expected throughput of TCP over multi-rate cellular systems. In this work, we consider a multi-rate system like High Data Rate (HDR) and represent the state space using a Markov chain. We calculate the state transition probabilities assuming transitions are possible between adjacent states only. We calculate the expected data rate conditioned to the initial state both analytically and through simulations. We use an M/G/l queuing model to capture the delay and TCP throughput for each of the initial states. We also illustrate how TCP throughput is affected by parameters like velocity, bit error rate, window size, TCP loss rate, and the underlying radio link protocol.

A vehicular ad hoc network (VANET) is a high mobility wireless ad hoc network that is targeted to support vehicular safety, traffic monitoring, and other commercial applications. Routing in large scale VANET is an important issue, because road complexity and traffic variety may bring many potential problems that existing routing protocol can not address. In this paper, we introduce a two-phase routing protocol (TOPO) that incorporates map information in routing. The proposed protocol defines an overlay graph with roads of high vehicular density and forwards packet along the pre-calculated path in the overlay. We argue that the proposed TOPO can serve as a framework integrating existing VANET routing protocols. In particular, we adopt modified AODV and GPSR in the access (residential area) to send packets to overlay, while greedy forwarding is used in overlay. We also consider the data diversity in VANETs and design TOPO as an ITS friendly protocol. To validate our design philosophy and the routing protocol, we use real world road layouts in Orlando, and generate vehicular mobility traces following some mobility models. We feed the traces to network simulator and study the routing behavior. Simulation results show the performance and effectiveness of our proposed routing protocols for large scale VANET scenarios.

Live video streaming over vehicular ad hoc networks (VANET) is an attractive feature to many applications, such as emergency live video transmission, road-side video advertisement broadcasting and inter-vehicle video conversation. Though vehicles have ample bandwidth, computation and storage capacity to support data intensive communication, the high mobility may cause persistent network partition. The performance of video streaming suffers from the delay and packet loss incurred by the long time disconnection. Although many solutions have been proposed to handle the high mobility problem, few of them addressed the problem in the context of video transmission. In this paper, we focus on video streaming between vehicles in highway, where the traffic density is adequate to mitigate frequent link disconnections and persistent network partitions. We study the performance of video streaming under different data forwarding and buffer management schemes. Real video data and the dedicated short range communications (DSRC) are used in the simulation study to better match the reality. The result of this paper gives insight for the design of the future inter-vehicle video streaming system.

In this paper, we focus on the problem of routing in resource rationed ad hoc networks. We exemplify the concept of resource rationing in a military scenario where the allocated resources are rationed to prolong the mission. By modeling the network as a directed weighted graph, we propose an economic approach to address the routing issue, namely HR3. Our approach begins with a hierarchical bidding process, through which nodes in the network bid for virtual currency. The winning bids use the granted virtual currency to pay the intermediate nodes for packet forwarding. After successful delivery, nodes get rewards. We study the truthfulness of HR3with rational nodes and propose security extension to identify and isolate the malicious nodes. Through simulations on ns-2, HR3shows performance gains in data throughput and energy consumption.

In this paper, we study the performance of a routing algorithm in a CDMA-based sensor network with respect to three energy metrics. These commonly used metrics are expected lifetime, multiple access interference, and queue length - all of which provide insight into how energy is depleted when nodes participate in packet forwarding. We formalize these metrics and show how the delay, throughput, and node life time are affected when routing is performed with a specific objective. Through ns-2 based simulation experiments, we show the tradeoffs between network performance and the different routing strategies adopted. These strategies can also be combined in order to achieve a desired system performance