Browsing by Author "Lu, Xiao"
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Item Applications of Repeated Games in Wireless Networks: A Survey(IEEE Communications Surveys & Tutorials, 6/16/2015) Hoang, Dinh Thai; Lu, Xiao; Niyato, Dusit; Wang, Ping; Kim, Dong In; Han, ZhuA repeated game is an effective tool to model interactions and conflicts for players aiming to achieve their objectives in a long-term basis. Contrary to static noncooperative games that model interactions among players in only one period, in repeated games, interactions of players repeat for multiple periods. Thus, the players become aware of other players' past behaviors and their future benefits, so as to adapt their strategies accordingly. In wireless networks, conflicts among wireless nodes can lead to selfish behaviors, resulting in poor network performances and detrimental individual payoffs. In this paper, we survey applications of repeated games in different wireless networks. The main goal is to demonstrate the use of repeated games in encouraging wireless nodes into cooperations, thereby improving network performances and avoiding network disruption due to selfish behaviors. Furthermore, various problems in wireless networks and variations of repeated game models together with the corresponding solutions are discussed in this survey. Finally, we outline some open issues and future research directions.Item Wireless charger networking for mobile devices: fundamentals, standards, and applications(IEEE Wireless Communications, 4/29/2015) Lu, Xiao; Niyato, Dusit; Wang, Ping; Kim, Dong In; Han, ZhuWireless charging is a technique of transmitting power through an air gap to an electrical device for the purpose of energy replenishment. Recently, wireless charging technology has significantly advanced in terms of efficiency and functionality. This article first presents an overview and fundamentals of wireless charging. We then provide the review of standards, that is, Qi and the Alliance for Wireless Power, and highlight their communication protocols. Next, we propose a novel concept of wireless charger networking that allows chargers to be connected to facilitate information collection and control. We demonstrate the application of the wireless charger network in user-charger assignment, which clearly shows the benefit in terms of reduced costs for users to identify the best chargers to replenish energy for their mobile devices.Item Wireless Networks With RF Energy Harvesting: A Contemporary Survey(IEEE Communications Surveys & Tutorials, 11/10/2014) Lu, Xiao; Wang, Ping; Niyato, Dusit; Kim, Dong In; Han, ZhuRadio frequency (RF) energy transfer and harvesting techniques have recently become alternative methods to power the next-generation wireless networks. As this emerging technology enables proactive energy replenishment of wireless devices, it is advantageous in supporting applications with quality-of-service requirements. In this paper, we present a comprehensive literature review on the research progresses in wireless networks with RF energy harvesting capability, which is referred to as RF energy harvesting networks (RF-EHNs). First, we present an overview of the RF-EHNs including system architecture, RF energy harvesting techniques, and existing applications. Then, we present the background in circuit design as well as the state-of-the-art circuitry implementations and review the communication protocols specially designed for RF-EHNs. We also explore various key design issues in the development of RF-EHNs according to the network types, i.e., single-hop networks, multiantenna networks, relay networks, and cognitive radio networks. Finally, we envision some open research directions.Item Wireless-Powered Device-to-Device Communications With Ambient Backscattering: Performance Modeling and Analysis(IEEE Transactions on Wireless Communications, 12/8/2017) Lu, Xiao; Jiang, Hai; Niyato, Dusit; Kim, Dong In; Han, ZhuThe recent advanced wireless energy harvesting technology has enabled wireless-powered communications to accommodate wireless data services in a self-sustainable manner. However, wireless-powered communications rely on active RF signals to communicate and result in high power consumption. On the other hand, ambient backscatter technology that passively reflects existing RF signal sources in the air to communicate has the potential to facilitate an implementation with ultra-low power consumption. In this paper, we introduce a hybrid device-to-device (D2D) communication paradigm by integrating ambient backscattering with wireless-powered communications. The hybrid D2D communications are self-sustainable, as no dedicated external power supply is required. However, since the radio signals for energy harvesting and for backscattering come from the ambient, the performance of the hybrid D2D communications depends largely on environment factors, e.g., distribution, spatial density, and transmission load of ambient energy sources. Therefore, we design two mode selection protocols for the hybrid D2D transmitter, allowing a more flexible adaptation to the environment. We then introduce analytical models to characterize the impacts of the considered environment factors on the hybrid D2D communication performance. Together with extensive simulations, our analysis shows that the communication performance benefits from larger repulsion, transmission load, and density of ambient energy sources. Furthermore, we investigate how different mode selection mechanisms affect the communication performance.