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Search Results: 1 - 10 of 178461 matches for " Xiang-Yang Li "
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Efficient Construction of Dominating Set in Wireless Networks
Xiaohua Xu,Xiang-Yang Li
Computer Science , 2012,
Abstract: Considering a communication topology of a wireless network modeled by a graph where an edge exists between two nodes if they are within each other's communication range. A subset $U$ of nodes is a dominating set if each node is either in $U$ or adjacent to some node in $U$. Assume each node has a disparate communication range and is associated with a positive weight, we present a randomized algorithm to find a min-weight dominating set. Considering any orientation of the graph where an arc $\overrightarrow{uv}$ exists if the node $v$ lies in $u$'s communication range. A subset $U$ of nodes is a strongly dominating set if every node except $U$ has both in-neighbor(s) and out-neighbor(s) in $U$. We present a polynomial-time algorithm to find a strongly dominating set of size at most $(2+\epsilon)$ times of the optimum. We also investigate another related problem called $K$-Coverage. Given are a set ${\cal D}$ of disks with positive weight and a set ${\cal P}$ of nodes. Assume all input nodes lie below a horizontal line $l$ and all input disks lie above this line $l$ in the plane. The objective is to find a min-weight subset ${\cal D}'\subseteq {\cal D}$ of disks such that each node is covered at least $K$ disks in ${\cal D}'$. We propose a novel two-approximation algorithm for this problem.
Search Me If You Can: Privacy-preserving Location Query Service
Xiang-Yang Li,Taeho Jung
Computer Science , 2012, DOI: 10.1109/INFCOM.2013.6567085
Abstract: Location-Based Service (LBS) becomes increasingly popular with the dramatic growth of smartphones and social network services (SNS), and its context-rich functionalities attract considerable users. Many LBS providers use users' location information to offer them convenience and useful functions. However, the LBS could greatly breach personal privacy because location itself contains much information. Hence, preserving location privacy while achieving utility from it is still an challenging question now. This paper tackles this non-trivial challenge by designing a suite of novel fine-grained Privacy-preserving Location Query Protocol (PLQP). Our protocol allows different levels of location query on encrypted location information for different users, and it is efficient enough to be applied in mobile platforms.
Enabling Privacy-preserving Auctions in Big Data
Taeho Jung,Xiang-Yang Li
Computer Science , 2013, DOI: 10.1109/INFCOMW.2015.7179380
Abstract: We study how to enable auctions in the big data context to solve many upcoming data-based decision problems in the near future. We consider the characteristics of the big data including, but not limited to, velocity, volume, variety, and veracity, and we believe any auction mechanism design in the future should take the following factors into consideration: 1) generality (variety); 2) efficiency and scalability (velocity and volume); 3) truthfulness and verifiability (veracity). In this paper, we propose a privacy-preserving construction for auction mechanism design in the big data, which prevents adversaries from learning unnecessary information except those implied in the valid output of the auction. More specifically, we considered one of the most general form of the auction (to deal with the variety), and greatly improved the the efficiency and scalability by approximating the NP-hard problems and avoiding the design based on garbled circuits (to deal with velocity and volume), and finally prevented stakeholders from lying to each other for their own benefit (to deal with the veracity). We achieve these by introducing a novel privacy-preserving winner determination algorithm and a novel payment mechanism. Additionally, we further employ a blind signature scheme as a building block to let bidders verify the authenticity of their payment reported by the auctioneer. The comparison with peer work shows that we improve the asymptotic performance of peer works' overhead from the exponential growth to a linear growth and from linear growth to a logarithmic growth, which greatly improves the scalability.
Network Agile Preference-Based Prefetching for Mobile Devices
JunZe Han,Xiang-Yang Li
Computer Science , 2012,
Abstract: For mobile devices, communication via cellular networks consumes more energy, and has a lower data rate than WiFi networks, and suffers an expensive limited data plan. However the WiFi network coverage range and density are smaller than those of the cellular networks. In this work, we present a behavior-aware and preference-based approach to prefetch news webpages that a user will be interested in and access, by exploiting the WiFi network connections to reduce the energy and monetary cost. In our solution, we first design an efficient preference learning algorithm based on keywords and URLs visited, which will keep track of the user's changing interests. By predicting the appearance and durations of the WiFi network connections, our prefetch approach then optimizes when to prefetch what webpages to maximize the user experience while lowing the prefetch cost. Our prefetch approach exploits the idle period of WiFi connections to reduce the tail-energy consumption. We implement our approach in iPhone. Our extensive evaluations show that our system achieves about 60% hit ratio, saves about 50% cellular data usage, and reduces the energy cost by 9%.
Message in a Sealed Bottle: Privacy Preserving Friending in Social Networks
Lan Zhang,Xiang-Yang Li
Computer Science , 2012,
Abstract: Many proximity-based mobile social networks are developed to facilitate connections between any two people, or to help a user to find people with matched profile within a certain distance. A challenging task in these applications is to protect the privacy the participants' profiles and personal interests. In this paper, we design novel mechanisms, when given a preference-profile submitted by a user, that search a person with matching-profile in decentralized multi-hop mobile social networks. Our mechanisms are privacy-preserving: no participants' profile and the submitted preference-profile are exposed. Our mechanisms establish a secure communication channel between the initiator and matching users at the time when the matching user is found. Our rigorous analysis shows that our mechanism is secure, privacy-preserving, verifiable, and efficient both in communication and computation. Extensive evaluations using real social network data, and actual system implementation on smart phones show that our mechanisms are significantly more efficient then existing solutions.
Mobile Sensing and Actuating with Ubiquitous Computing
Mo Li,Yunhao Liu,Xiang-Yang Li
International Journal of Distributed Sensor Networks , 2012, DOI: 10.1155/2012/296396
Photoluminescence and Characterization of ZnO/Zn2SnO4 Nanocables
ZHOU Ru-Li, KONG Xiang-Yang
无机材料学报 , 2011, DOI: 10.3724/sp.j.1077.2011.00597
Abstract: ZnO and Zn2SnO4 are excellent functional semiconducting materials with wide direct band gap, high electron mobility and photocatalytic activity. High―density single―crystalline ZnO/Zn2SnO4 nanocables were successfully synthesized by using a simple thermal co―evaporation from a mixture source of ZnO and SnO2 powders. The products in general contain various geometries of wires, with an average diameter of 50―100 nm. These nanowires are consisted of ZnO core and Zn2SnO4 sheath with ultra―length, up to several hundred microns. The images of transmission electron microscope (TEM) show that the ZnO core of the nanocable grows along the direction of <0001>. The interface between ZnO and Zn2SnO4 performs lattice coherent. The photoluminescence (PL) spectra recorded from the nanocables at room temperature show only a strong peak corresponding to UV band emission of ZnO at about 380.58 nm, which indicates that the sheath of Zn2SnO4 prohibits the oxygen deficiency in the surface of nanocables. ZnO/Zn2SnO4 nanocables can effectively suppress the recombination of the photogenerated electrons and holes, which is promising as anode for dye―sensitized solar cells.
Design, Implementation, and Evaluation of Wireless Sensor Network Systems
Liu Jiangchuan,Cao Jiannong,Li Xiang-Yang,Sun Limin
EURASIP Journal on Wireless Communications and Networking , 2010,
Design, Implementation, and Evaluation of Wireless Sensor Network Systems
Jiangchuan Liu,Jiannong Cao,Xiang-Yang Li,Limin Sun
EURASIP Journal on Wireless Communications and Networking , 2010, DOI: 10.1155/2010/439890
Real-time Data Collection Scheduling in Multi-hop Wireless Sensor Networks
Xiaohua Xu,Xiang-Yang Li,Min Song
Computer Science , 2012,
Abstract: We study real time periodic query scheduling for data collection in multihop Wireless Sensor Networks (WSNs). Given a set of heterogenous data collection queries in WSNs, each query requires the data from the source sensor nodes to be collected to the control center within a certain end-to-end delay. We first propose almost-tight necessary conditions for a set of different queries to be schedulable by a WSN. We then develop a family of efficient and effective data collection algorithms that can meet the real-time requirement under resource constraints by addressing three tightly coupled tasks: (1) routing tree construction for data collection, (2) link activity scheduling, and (3) packet-level scheduling. Our theoretical analysis for the schedulability of these algorithms show that they can achieve a constant fraction of the maximum schedulable load. For the case of overloaded networks where not all queries can be possibly satisfied, we propose an efficient approximation algorithm to select queries to maximize the total weight of selected schedulable queries. The simulations corroborate our theoretical analysis.
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