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Zhang S.,Central South University | Liu X.,Hunan University | Wang J.,Central South University | Wang J.,Hunan Engineering Center for Currency Recognition and Self Service | And 3 more authors.
Information Sciences | Year: 2015

Radio Frequency Identification (RFID) has attracted much research attention in recent years. RFID can support automatic information tracing and management during the management process in many fields. A typical field that uses RFID is modern warehouse management, where products are attached with tags and the inventory of products is managed by retrieving tag IDs. Many practical applications require searching a group of tags to determine whether they are in the system or not. The existing studies on tag searching mainly focused on improving the time efficiency but paid little attention to energy efficiency which is extremely important for active tags powered by built-in batteries. To fill in this gap, this paper investigates the tag searching problem from the energy efficiency perspective. We first propose an Energy-efficient tag Searching protocol in Multiple reader RFID systems, namely ESiM, which pushes per tag energy consumption to the limit as each tag needs to exchange only one bit data with the reader. We then develop a time efficiency enhanced version of ESiM, namely TESiM, which can dramatically reduce the execution time while only slightly increasing the transmission overhead. Extensive simulation experiments reveal that, compared to state-of-the-art solution in the current literature, TESiM reduces per tag energy consumption by more than one order of magnitude subject to comparable execution time. In most considered scenarios, TESiM even reduces the execution time by more than 50%. © 2015 Elsevier Inc. All rights reserved.

Chen L.,Central South University | Wang J.,Central South University | Wang J.,Hunan Engineering Center for Currency Recognition and Self Service | Peng X.,Central South University | Kui X.,Central South University
International Journal of Distributed Sensor Networks | Year: 2015

Recent studies reveal that great benefit can be achieved by employing mobile collectors to gather data in wireless sensor networks. Since the mobile collector can traverse the transmission range of each sensor, the energy of nodes may be saved near maximally. However, for directly receiving data packet from every node, the length of mobile collector route should be very long. Hence it may significantly increase the data gathering latency. To solve this problem, several algorithms have been proposed. One of them called BRH-MDG found that data gathering latency can be effectively shortened by performing proper local aggregation via multihop transmissions and then uploading the aggregated data to the mobile collector. But, the BRH-MDG algorithm did not carefully analyze and optimize the energy consumption of the entire network. In this paper, we propose a mathematical model for the energy consumption of the LNs and present a new algorithm called EEBRHM. The simulation results show that under the premise of bounded relay hop, compared with BRH-MDG, EEBRHM can prolong the networks lifetime by 730%. © 2015 Ling Chen et al.

An Y.,Central South University | An Y.,Hunan Engineering Center for Currency Recognition and Self Service | Luo X.,Central South University | Liu Y.,Central South University | And 5 more authors.
Concurrency Computation | Year: 2015

Summary Message replication is often used to improve the delivery ratio in delay-tolerant networks because of the short-lived wireless connectivity environment. However, packet replication may easily incur large resource consumption and finally result in network congestion. This paper proposes a probabilistic packet acceptance and drop algorithm (PAD), which adaptively controls congestion for delay-tolerant networks. In PAD algorithm, the queue length and the input/output rate are combined to detect congestion. Based on the congestion state, each node determines the probability of accepting or dropping packets to obtain a good trade-off between high delivery ratio and low overhead. Furthermore, based on the birth-death model, we construct the continuous-time Markov chain to analyze the delivery ratio of a packet. Theory analysis and simulation results show that PAD increases the delivery ratio by more than 130% with least overhead. Meanwhile, it also achieves the shortest average end-to-end delay when the buffer of a node is severely limited. © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Feng Q.,Central South University | Feng Q.,Hunan Engineering Center for Currency Recognition and Self Service | Zhou Q.,Central South University | Zhou Q.,Hunan Engineering Center for Currency Recognition and Self Service | And 2 more authors.
Journal of Combinatorial Optimization | Year: 2015

Co-path Set problem is of important applications in mapping unique DNA sequences onto chromosomes and whole genomes. Given a graph G, the parameterized version of Co-path Set problem is to find a subset F of edges with size at most k such that each connected component in (Formula presented.) is a path. In this paper, we give a kernel of size 6k and a randomized algorithm of running time (Formula presented.) for the Parameterized Co-path Set problem. The randomized methods developed in the paper are of great promising to be applied to other branch-based algorithms. © 2015 Springer Science+Business Media New York

You J.,Central South University | You J.,Hunan Engineering Center for Currency Recognition and Self Service | Wang J.,Central South University | Wang J.,Hunan Engineering Center for Currency Recognition and Self Service | And 4 more authors.
Theoretical Computer Science | Year: 2015

Two restricted versions of the Subforest Isomorphism problem, the Covering a Tree by a Set of Stars (CTSS) and the Covering a Tree by a Set of Paths (CTSP) problems, are studied. Both problems are NP-complete. The problems are closely related to a number of well-studied problems, including the problems Subgraph Isomorphism, Tree Editing, and Graph Packing. It is shown that the problems CTSS and CTSP are fixed-parameter tractable. Thorough development of parameterized algorithms and kernelization algorithms for these problems are presented. © 2015 Elsevier B.V.

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