Browsing by Author "Poor, H. Vincent"
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Item A Cooperative Bayesian Nonparametric Framework for Primary User Activity Monitoring in Cognitive Radio Networks(IEEE Journal on Selected Areas in Communications, 2/2/2012) Saad, Walid; Han, Zhu; Poor, H. Vincent; Ba?ar, Tamer; Song, Jin BinThis paper introduces a novel approach that enables a number of cognitive radio devices that are observing the availability pattern of a number of primary users (PUs), to cooperate and use Bayesian nonparametric techniques to estimate the distributions of the PUs' activity pattern. To address this problem, a coalitional game is formulated between the cognitive devices and an algorithm for cooperative coalition formation is proposed. It is shown that the proposed coalition formation algorithm allows the cognitive nodes that are experiencing a similar behavior from some PUs to self-organize into disjoint, independent coalitions. Inside each coalition, the cooperative cognitive nodes use Bayesian nonparametric techniques so as to improve the accuracy of the estimated PUs' activity distributions. Simulation results show that the proposed algorithm significantly improves the estimates of the PUs' activity patterns.Item A Game-Theoretic Approach to Energy Trading in the Smart Grid(IEEE Transactions on Smart Grid, 4/15/2014) Wang, Yunpeng; Saad, Walid; Han, Zhu; Poor, H. Vincent; Ba?ar, TamerElectric storage units constitute a key element in the emerging smart grid system. In this paper, the interactions and energy trading decisions of a number of geographically distributed storage units are studied using a novel framework based on game theory. In particular, a noncooperative game is formulated between storage units, such as plug-in hybrid electric vehicles, or an array of batteries that are trading their stored energy. Here, each storage unit's owner can decide on the maximum amount of energy to sell in a local market so as to maximize a utility that reflects the tradeoff between the revenues from energy trading and the accompanying costs. Then in this energy exchange market between the storage units and the smart grid elements, the price at which energy is traded is determined via an auction mechanism. The game is shown to admit at least one Nash equilibrium and a novel algorithm that is guaranteed to reach such an equilibrium point is proposed. Simulation results show that the proposed approach yields significant performance improvements, in terms of the average utility per storage unit, reaching up to 130.2% compared to a conventional greedy approach.Item Asymptotic Analysis of Large Cooperative Relay Networks Using Random Matrix Theory(EURASIP Journal on Advances in Signal Processing, 3/5/2008) Li, Husheng; Han, Zhu; Poor, H. VincentCooperative transmission is an emerging communication technology that takes advantage of the broadcast nature of wireless channels. In cooperative transmission, the use of relays can create a virtual antenna array so that multiple-input/multiple-output (MIMO) techniques can be employed. Most existing work in this area has focused on the situation in which there are a small number of sources and relays and a destination. In this paper, cooperative relay networks with large numbers of nodes are analyzed, and in particular the asymptotic performance improvement of cooperative transmission over direction transmission and relay transmission is analyzed using random matrix theory. The key idea is to investigate the eigenvalue distributions related to channel capacity and to analyze the moments of this distribution in large wireless networks. A performance upper bound is derived, the performance in the low signal-to-noise-ratio regime is analyzed, and two approximations are obtained for high and low relay-to-destination link qualities, respectively. Finally, simulations are provided to validate the accuracy of the analytical results. The analysis in this paper provides important tools for the understanding and the design of large cooperative wireless networks.Item Coalitional Games in Partition Form for Joint Spectrum Sensing and Access in Cognitive Radio Networks(IEEE Journal of Selected Topics in Signal Processing, 10/10/2011) Saad, Walid; Han, Zhu; Zheng, Rong; Hjorungnes, Are; Ba?ar, Tamer; Poor, H. VincentUnlicensed secondary users (SUs) in cognitive radio networks are subject to an inherent tradeoff between spectrum sensing and spectrum access. Although each SU has an incentive to sense the primary user (PU) channels for locating spectrum holes, this exploration of the spectrum can come at the expense of a shorter transmission time, and, hence, a possibly smaller capacity for data transmission. This paper investigates the impact of this tradeoff on the cooperative strategies of a network of SUs that seek to cooperate in order to improve their view of the spectrum (sensing), reduce the possibility of interference among each other, and improve their transmission capacity (access). The problem is modeled as a coalitional game in partition form and an algorithm for coalition formation is proposed. Using the proposed algorithm, the SUs can make individual distributed decisions to join or leave a coalition while maximizing their utilities which capture the average time spent for sensing as well as the capacity achieved while accessing the spectrum. It is shown that, by using the proposed algorithm, the SUs can self-organize into a network partition composed of disjoint coalitions, with the members of each coalition cooperating to jointly optimize their sensing and access performance. Simulation results show the performance improvement that the proposed algorithm yields with respect to the noncooperative case. The results also show how the algorithm allows the SUs to self-adapt to changes in the environment such as changes in the traffic of the PUs, or slow mobility.Item Game Theoretic Approaches to Massive Data Processing in Wireless Networks(IEEE Wireless Communications, 2/28/2018) Zheng, Zijie; Song, Lingyang; Han, Zhu; Li, Geoffrey Ye; Poor, H. VincentWireless communication networks are becoming highly virtualized with two-layer hierarchies, in which controllers at the upper layer with tasks to achieve can ask a large number of agents at the lower layer to help realize computation, storage, and transmission functions. Through offloading data processing to the agents, the controllers can accomplish otherwise prohibitive big data processing. Incentive mechanisms are needed for the agents to perform the controllers' tasks in order to satisfy the corresponding objectives of controllers and agents. In this article, a hierarchical game framework with fast convergence and scalability is proposed to meet the demand for real-time processing for such situations. Possible future research directions in this emerging area are also discussed.Item High performance cooperative transmission protocols based on multiuser detection and network coding(IEEE Transactions on Wireless Communications, 1/26/2008) Han, Zhu; Zhang, Xin; Poor, H. VincentCooperative transmission is an emerging communication technique that takes advantage of the broadcast nature of wireless channels. However, due to low spectral efficiency and the requirement of orthogonal channels, its potential for use in future wireless networks is limited. In this paper, by making use of multiuser detection (MUD) and network coding, cooperative transmission protocols with high spectral efficiency, diversity order, and coding gain are developed. Compared with the traditional cooperative transmission protocols with singleuser detection, in which the diversity gain is only for one source user, the proposed MUD cooperative transmission protocols have the merit that the improvement of one user's link can also benefit the other users. In addition, using MUD at the relay provides an environment in which network coding can be employed. The coding gain and high diversity order can be obtained by fully utilizing the link between the relay and the destination. From the analysis and simulation results, it is seen that the proposed protocols achieve higher diversity gain, better asymptotic efficiency, and lower bit error rate, compared to traditional MUD schemes and to existing cooperative transmission protocols. From the simulation results, the performance of the proposed scheme is near optimal as the performance gap is 0.12dB for average bit error rate (BER) 10-6 and 1.04dB for average BER 10-3, compared to two performance upper bounds.Item Lifetime improvement in wireless sensor networks via collaborative beamforming and cooperative transmission(IET Microwaves, Antennas and Propagation, 12/18/2007) Han, Zhu; Poor, H. VincentCollaborative beamforming (CB) and cooperative transmission (CT) have recently emerged as communication techniques that can make effective use of collaborative/cooperative nodes to create a virtual multiple-input/multiple-output system. Extending the lifetime of networks composed of battery-operated nodes is a key issue in the design and operation of wireless sensor networks. The effects on network lifetime of allowing closely located nodes to use CB/CT to reduce the load or even to avoid packet-forwarding requests to nodes that have critical battery life are considered. First, the effectiveness of CB/CT in improving the signal strength at a faraway destination using energy in nearby nodes is studied. Then, the performance improvement obtained by this technique is analysed for a special 2D disc case. Further, for general networks in which information-generation rates are fixed, a new routing problem is formulated as a linear- programming problem, whereas for other general networks, the cost for routing is dynamically adjusted according to the amount of energy remaining and the effectiveness of CB/CT. From the analysis and the simulation results, it is seen that the proposed method can reduce the payloads of energy-depleting nodes by about 90% in the special case network considered and improve the lifetimes of general networks by about 10%, compared with existing techniquesItem Perfect Output Feedback in the Two-User Decentralized Interference Channel(IEEE Transactions on Information Theory, 8/12/2015) Perlaza, Samir M.; Tandon, Ravi; Poor, H. Vincent; Han, ZhuIn this paper, the ?-Nash equilibrium (?-NE) region of the two-user Gaussian interference channel (IC) with perfect output feedback is approximated to within 1 bit/s/Hz and ? arbitrarily close to 1 bit/s/Hz. The relevance of the ?-NE region is that it provides the set of rate pairs that are achievable and stable in the IC when both transmitter-receiver pairs autonomously tune their own transmit-receive configurations seeking an ?-optimal individual transmission rate. Therefore, any rate tuple outside the ?-NE region is not stable as there always exists one link able to increase by at least ? bits/s/Hz its own transmission rate by updating its own transmit-receive configuration. The main insights that arise from this paper are as follows. First, the ?-NE region achieved with feedback is larger than or equal to the ?-NE region without feedback. More importantly, for each rate pair achievable at an ?-NE without feedback, there exists at least one rate pair achievable at an ?-NE with feedback that is weakly Pareto superior. Second, there always exists an ?-NE transmit-receive configuration that achieves a rate pair that is at most 1 bit/s/Hz per user away from the outer bound of the capacity region.