Browsing by Subject "Network formation"
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Item Open Access Equilibrium refinements for the network formation game(Springer, 2019-01) İlkılıç, Rahmi; İkizler, HüseyinThis paper examines a normal form game of network formation due to Myerson (Game theory: analysis of conflict, Harvard University Press, Cambridge, 1991). All players simultaneously announce the links they wish to form. A link is created if and only if there is mutual consent for its formation. The empty network is always a Nash equilibrium of this game. We define a refinement of Nash equilibria that we call trial perfect. We show that the set of networks which can be supported by a pure strategy trial perfect equilibrium coincides with the set of pairwise-Nash equilibrium networks, for games with link-responsive payoff functions.Item Open Access Essays on network theory and applications(Bilkent University, 2019-01) ikizler, HüseyinThis thesis consists of three essays centering on network theory. In the first essay, we use a network model to show how homophily, conjoined with conformity, may shape political divisions along ethnic lines in multi-ethnic societies. We find that the decisive factor is not simply the degree of homophily but the presence of monotone agents, who are only connected with their own types. When there is no monotone agent, even if the level of homophily is unbounded, ethnic divisions can be avoided. The presence of a few monotone agents necessarily divides a sparsely integrated society along ethnic lines. The second essay examines both theoretically and empirically (strong) Nash equilibrium of the free labor mobility network formation game. First, we design a network formation game in which each country's action is a choice of a mobility network between a subset of countries. The utility of each country is determined by a country specific threshold level of absorption ratio and net labor ows. We theoretically characterize all stable and optimal mobility networks under speci fic assumptions. In our empirical analysis, we focus on EU and EFTA member countries. We observe that some specific countries incur the maximum loss in the grand mobility network according to our model. These countries turnout to be the ones in which reintroduction of quotas on migration is approved via referendum. In the third essay, we examine a normal form game of network formation due to Myerson (1991). All players simultaneously announce the links they wish to form. A link is created if and only if there is mutual consent for its formation. The empty network is always a Nash equilibrium of this game. We define a refinement of Nash equilibria that we call trial perfect. We show that the set of networks which can be supported by a pure strategy trial perfect equilibrium coincides with the set of pairwise-Nash equilibrium networks, for games with link-responsive payoff functions.Item Open Access Multiagent systems: learning, strategic behavior, cooperation, and network formation(Elsevier, 2018) Tekin, Cem; Zhang, S.; Xu, J.; Schaar, M. van der; Djurić, P. M.; Richard., C.Many applications ranging from crowdsourcing to recommender systems involve informationally decentralized agents repeatedly interacting with each other in order to reach their goals. These networked agents base their decisions on incomplete information, which they gather through interactions with their neighbors or through cooperation, which is often costly. This chapter presents a discussion on decentralized learning algorithms that enable the agents to achieve their goals through repeated interaction. First, we discuss cooperative online learning algorithms that help the agents to discover beneficial connections with each other and exploit these connections to maximize the reward. For this case, we explain the relation between the learning speed, network topology, and cooperation cost. Then, we focus on how informationally decentralized agents form cooperation networks through learning. We explain how learning features prominently in many real-world interactions, and greatly affects the evolution of social networks. Links that otherwise would not have formed may now appear, and a much greater variety of network configurations can be reached. We show that the impact of learning on efficiency and social welfare could be both positive or negative. We also demonstrate the use of the aforementioned methods in popularity prediction, recommender systems, expert selection, and multimedia content aggregation.Item Open Access PSAR: Power-source-aware routing in ZigBee networks(2012) Tekkalmaz, M.; Korpeoglu I.ZigBee is a recent wireless networking technology built on IEEE 802.15.4 standard and designed especially for low-data rate and low-duty cycle applications such as home and building automation and sensor networks. One of the primary goals of ZigBee is low power consumption and therefore long-living networks. Despite this goal, current network formation and routing protocols described in the ZigBee specification do not fully address power consumption issues. In this work, we propose a distributed routing algorithm to reduce power consumption of battery-powered devices by routing the communication through mains-powered devices whenever possible and consequently increasing the overall network lifetime. The proposed algorithm works on tree topologies supported by ZigBee and requires only minor modifications to the current specification. Our ns-2 simulation results showed that the algorithm is able to reduce the power consumption of battery-powered devices significantly with minimal communication overhead. © Springer Science+Business Media, LLC 2012.