Coalition Formation Game for Cooperative Cognitive Radio Using Gibbs Sampling

This paper considers a cognitive radio network in which each secondary user selects a primary user to assist in order to get a chance of accessing the primary user channel. Thus, each group of secondary users assisting the same primary user forms a coaltion. Within each coalition, sequential relaying is employed, and a relay ordering algorithm is used to make use of the relays in an efficient manner. It is required then to find the optimal sets of secondary users assisting each primary user such that the sum of their rates is maximized. The problem is formulated as a coalition formation game, and a Gibbs Sampling based algorithm is used to find the optimal coalition structure.Comment: 7 pages, 2 figure

The Social Medium Selection Game

We consider in this paper competition of content creators in routing their content through various media. The routing decisions may correspond to the selection of a social network (e.g. twitter versus facebook or linkedin) or of a group within a given social network. The utility for a player to send its content to some medium is given as the difference between the dissemination utility at this medium and some transmission cost. We model this game as a congestion game and compute the pure potential of the game. In contrast to the continuous case, we show that there may be various equilibria. We show that the potential is M-concave which allows us to characterize the equilibria and to propose an algorithm for computing it. We then give a learning mechanism which allow us to give an efficient algorithm to determine an equilibrium. We finally determine the asymptotic form of the equilibrium and discuss the implications on the social medium selection problem

Cognitive Hierarchy Theory for Distributed Resource Allocation in the Internet of Things

In this paper, the problem of distributed resource allocation is studied for an Internet of Things (IoT) system, composed of a heterogeneous group of nodes compromising both machine-type devices (MTDs) and human-type devices (HTDs). The problem is formulated as a noncooperative game between the heterogeneous IoT devices that seek to find the optimal time allocation so as to meet their quality-of-service (QoS) requirements in terms of energy, rate and latency. Since the strategy space of each device is dependent on the actions of the other devices, the generalized Nash equilibrium (GNE) solution is first characterized, and the conditions for uniqueness of the GNE are derived. Then, to explicitly capture the heterogeneity of the devices, in terms of resource constraints and QoS needs, a novel and more realistic game-theoretic approach, based on the behavioral framework of cognitive hierarchy (CH) theory, is proposed. This approach is then shown to enable the IoT devices to reach a CH equilibrium (CHE) concept that takes into account the various levels of rationality corresponding to the heterogeneous computational capabilities and the information accessible for each one of the MTDs and HTDs. Simulation results show that the proposed CHE solution keeps the percentage of devices with satisfied QoS constraints above 96% for IoT networks containing up to 10,000 devices without considerably degrading the overall system performance.Comment: To appear in IEEE Transactions on Wireless Communications, 201

Energy and security aspects of wireless networks: Performance and tradeoffs

Energy and security are becoming increasingly important in the design of future wireless communication systems. This thesis focuses on these two main aspects of wireless networks and studies their tradeoffs with other performance metrics such as throughput and delay. The first part of the thesis deals with the energy aspect of wireless networks in which we present several novel joint-physical network layer techniques and either evaluate their energy efficiency or study the energy/delay/throughput tradeoffs. First, we study the energy/delay tradeoffs for the problem of reliable packet transmission over a wireless time-varying fading link and also investigate the effect of having Channel State Information on the resulting tradeoff . Then, we extend the model to a single-hop multicast time varying wireless network. We address energy/delay/throughput tradeoffs by considering the problem of streaming a real time file with a fixed delay and energy constraints where the objective is to maximize the number of packets received by the destinations. Again, the effect of having Channel State Information is studied. Also, the effect of using Random Network Coding as a transmission scheme is studied and compared to traditional transmission schemes such as simple ARQ. Next, we consider the effect of cooperation on the energy efficiency of wireless transmissions in which we propose several joint physical-network layer cooperation techniques. Also, the effect of Random Network Coding is investigated in the context of cooperation in which Random Network Coding based cooperation techniques are investigated and compared to cooperation techniques that rely on simple ARQ solely or combined with superposition Alamouti space-time codes. We then consider the particular case of cellular systems in which we design rate allocation technique that minimizes the consumption energy in a Macro cell. This technique takes into account sleep mode configuration of current base stations. In the second part of the thesis, we focus on security and in particular on privacy. We also study the tradeoff between securing wireless transmissions and the energy/delay overhead due to security by considering the problem of information exchange among adjacent wireless node in the presence of an eavesdropper. The nodes are required to exchange their information while keeping it secret from the eavesdropper. The nodes can choose to transmit either through public channel or though more costly private channels. We express the cost of using the private channels in terms of the extra energy or delay required to transmit through the private channel. We then minimize the security cost subject to a target security level. Also this part presents a deterministic Network Coding based transmission scheme and investigates its effect on the achieved performance. Last, we introduce the problem of minimum energy scheduling of a group of base stations and compare this problem to the standard minimum length scheduling problem. We also discuss the complications and the challenges associated with solving the minimum energy scheduling problem