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Tsinghua Science and Technology

Issue 5 • Date Oct. 2012

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Displaying Results 1 - 14 of 14
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • Contents

    Page(s): 1
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    Freely Available from IEEE
  • Guest editorial: Special issue on wireless computing and networking

    Page(s): 485 - 486
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    Freely Available from IEEE
  • Data collection capacity of random-deployed wireless sensor networks under physical models

    Page(s): 487 - 498
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    Data collection is one of the most important functions provided by wireless sensor networks. In this paper, we study the theoretical limitations of data collection in terms of capacity for a wireless sensor network where n sensors are randomly deployed. We first consider data collection under physical model. We show that the capacity of data collection is in order of Θ(W) where W is the fixed data-rate on individual links. Particularly, we give a simple collection method based on interference blocks and theoretically prove that the method can achieve the optimal capacity in order. If each sensor can aggregate its receiving packets into a single packet to send, the capacity of data collection increases to $Theta left({n over log , n} W right)$. We then derive a lower bound and an upper bound of data collection capacity under generalized physical model where the data rate depends on the signal to interference plus noise ratio. View full abstract»

    Open Access
  • Area query processing based on gray code in wireless sensor networks

    Page(s): 499 - 511
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (687 KB)  

    Area query processing is significant for various applications of wireless sensor networks since it can request information of particular areas in the monitored environment. Existing query processing techniques cannot solve area queries. Intuitively centralized processing on Base Station can accomplish area queries via collecting information from all sensor nodes. However, this method is not suitable for wireless sensor networks with limited energy since a large amount of energy is wasted for reporting useless data. This motivates us to propose an energy-efficient in-network area query processing scheme. In our scheme, the monitored area is partitioned into grids, and a unique gray code number is used to represent a Grid ID (GID), which is also an effective way to describe an area. Furthermore, a reporting tree is constructed to process area merging and data aggregations. Based on the properties of GIDs, subareas can be merged easily and useless data can be discarded as early as possible to reduce energy consumption. For energy-efficiently answering continuous queries, we also design an incremental update method to continuously generate query results. In essence, all of these strategies are pivots to conserve energy consumption. With a thorough simulation study, it is shown that our scheme is effective and energy-efficient. View full abstract»

    Open Access
  • Distributed aggregation algorithms for mobile sensor networks with group mobility model

    Page(s): 512 - 520
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (523 KB)  

    In many applications of mobile sensor networks, such as water flow monitoring and disaster rescue, the nodes in the network can move together or separate temporarily. The dynamic network topology makes traditional spanning-tree-based aggregation algorithms invalid in mobile sensor networks. In this paper, we first present a distributed clustering algorithm which divides mobile sensor nodes into several groups, and then propose two distributed aggregation algorithms, Distance-AGG (Aggregation based on Distance), and Probability-AGG (Aggregation based on Probability). Both of these two algorithms conduct an aggregation query in three phases: query dissemination, intra-group aggregation, and inter-group aggregation. These two algorithms are efficient especially in mobile networks. We evaluate the performance of the proposed algorithms in terms of aggregation accuracy, energy efficiency, and query delay through ns-2 simulations. The results show that Distance-AGG and Probability-AGG can obtain higher accuracy with lower transmission and query delay than the existing aggregation algorithms. View full abstract»

    Open Access
  • A designated query protocol for serverless mobile RFID systems with reader and tag privacy

    Page(s): 521 - 536
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    Recently, a new type of Radio Frequency IDentification (RFID) system with mobile readers is introduced. In such a system, it is more desirable for mobile readers to identify tags without a back-end server, and thus it is frequently referred as a serverless mobile RFID system. In this paper, we formalize a serverless mobile RFID system model and propose a new encryption-based system that preserves the privacy of both tags and readers in the model. In addition, we define a new adversary model for the system model and show the security of the proposed system. Throughout comparisons between ours and the other alternatives, we show that our proposed system provides a stronger reader privacy and robustness against a reader forgery attack than the competitors. View full abstract»

    Open Access
  • Design and analysis of Prioritized Medium Access Control protocol for backbone routers in wireless mesh networks

    Page(s): 537 - 552
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    A Prioritized Medium Access Control (P-MAC) protocol is proposed for wireless routers of mesh networks with quality-of-service provisioning. The simple yet effective design of P-MAC offers strict service differentiation for prioritized packets. A Markov model is developed to yield important performance matrices including the packet blocking probability due to queue overflow and the packet reneging probability due to delay bound. It is further proved that the service time of P-MAC approximates exponential distribution, and can be effectively estimated. The analytic models with preemptive and non-preemptive schemes, validated via simulations, show that P-MAC can effectively support traffic differentiation and achieve very low packet dropping (both reneging and blocking) probabilities when the traffic load is below the channel capacity. When the network is overloaded, P-MAC can still maintain extremely stable and high channel throughput. Moreover, it is demonstrated that P-MAC performs superior in multihop networks, further proving the advantages of the proposed protocol. View full abstract»

    Open Access
  • A distributed design for minimum 2-Connected m-Dominating Set in bidirectional wireless ad-hoc networks

    Page(s): 553 - 566
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (725 KB)  

    Wireless ad-hoc network is widely used in many fields for its convenience and outstanding suitability. Because of the inherent lack of infrastructure and the nature of wireless channels, people select the k-Connected m-Dominating Set ((k, m)-CDS) in a network as a fault-tolerant virtual backbone to help the routing process, which will save the energy of non-dominators and improve the network performance significantly. Considering the economic cost and efficiency, we choose (2, m)-CDS as the object of this paper, which is helpful enough in practical applications and has a smaller size. We firstly study the existing algorithms for (k, m)-CDS and figure out the problems of these designs. Then we propose a new distributed algorithm named Dominating Set Based Algorithm (DSBA) with three sub-routines: Dominating Set Algorithm (DSA), Connection Algorithm (CA), and Connectivity Expansion Algorithm (CEA). Instead of commonly used Maximal Independent Set (MIS), we pick dominating set directly from the given graph, and then connect them by a two-step ring based connecting strategy to satisfy the 2-connectivity. We also provide the correctness and complexity analysis of DSBA. At last, we compare DSBA with the last construction Distributed Deterministic Algorithm (DDA) by several numerical experiments. The simulation results show that DSBA improves over 30 percent of the performance of DDA, proving that DSBA is more practical for real-world applications. View full abstract»

    Open Access
  • Online learning approaches in maximizing weighted throughput in an unreliable channel

    Page(s): 567 - 574
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    We design online algorithms to schedule unit-length packets with values and deadlines through an unreliable communication channel. In this model, time is discrete. Packets arrive over time; each packet has a non-negative value and an integer deadline. In each time step, at most one packet can be sent. The ratio of successfully delivering a packet depends on the channel's quality of reliability. The objective is to maximize the total value gained by delivering packets no later than their respective deadlines. In this paper, we conduct theoretical and empirical studies of online learning approaches for this model and a few of its variants. These online learning algorithms are analyzed in terms of external regret. We conclude that no online learning algorithms have constant regrets. Our online learning algorithms outperform online competitive algorithms in terms of algorithmic simplicity and running complexity. In general, these online learning algorithms work no worse than the best known competitive online algorithm for maximizing weighted throughput in practice. View full abstract»

    Open Access
  • Interference-aware probabilistic routing for wireless sensor networks

    Page(s): 575 - 585
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    Wireless communications are prone to the interference, so the data transmission among the nodes in wireless sensor networks deployed in complex environments has the obvious uncertainty. This paper adopts probability theory to extend the existed interference model, and gives an interference analysis model and implements it through the cross-layer method. In addition, the isotonic property of the interference-aware routing metric is proved. Then, a probabilistic routing algorithm is proposed and its correctness and time-space complexity are analyzed. Simulation results show that the proposed algorithm can achieve better packet delivery ratio, throughput, jitter and average delay in dense deployment under the different loads at the expense of the comparable average length of paths compared with the Adhoc On-Demand Distance Vector (AODV) algorithm. View full abstract»

    Open Access
  • A switch agent for wireless sensor nodes with dual interfaces: Implementation and evaluation

    Page(s): 586 - 598
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1031 KB)  

    Data generation in wireless sensor networks could be bursty as it is dictated by the presence or absence of events of interest that generate these data. While conventional sensor nodes possessed only one radio interface, next generation sensor nodes are expected to have two (possibly more) radio interfaces, each with different ranges, capacities, and power consumptions. Equipping sensor nodes with dual radios has its own benefits and can be quite useful in handling bursty traffic while at the same time satisfying the application's delivery requirements. In this paper, we propose an adaptive interface switch agent that intelligently selects the interface to be used for data transmission at a sensor node based on the data burst length or end-to-end delay while taking into consideration power consumption and throughput. The proposed work generalizes earlier works in this area to enable both the source nodes and intermediate data forwarding nodes to initiate the activation of high power radios so that they can be utilized to a higher degree for converge-cast communication. We have performed extensive simulations with sensor nodes containing both IEEE 802.15.4 and IEEE 802.11 compatible radios. Our simulation results indicate that the switch agent yields throughput, delay, and packet delivery ratio comparable to the higher bandwidth interface alone, without incurring much energy wastage. View full abstract»

    Open Access
  • CoP: An ultra-lightweight secure network coding scheme via last forwarder's proof

    Page(s): 599 - 605
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    Network coding can improve network efficiency by extending copy-and-forward paradigm to code-and-forward paradigm. It thus imposes a security problem called pollution attack that some network coding or forwarding nodes may intentionally fabricate, modify, forge, or drop packets. Recently, many authentication methods are proposed to guarantee the correctness of encoding and forwarding results via the verification from receivers. Those methods include homomorphic hashing, homomorphic message authentication code, and homomorphic signature. However, those schemes result in expensive computation overhead due to the homomorphic cryptographic primitives, so that those methods will not be able to work in most applications that confront resource constraints. In this paper, we propose an ultra-lightweight checking protocol to guarantee the secure network coding without any homomorphic cryptographic primitives. The extensive analysis proofs that it has following advantages: the least security assumption for intermediate nodes, the least cryptographic primitive requirement, ultra-lightweight computation, flexible message length with probably proof, and minimal rounds in terms of message exchanging. View full abstract»

    Open Access
  • Call for papers

    Page(s): 606
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    Freely Available from IEEE

Aims & Scope

Tsinghua Science and Technology (Tsinghua Sci Technol) aims to highlight scientific achievements in computer science, electronic engineering, and other IT fields. Contributions all over the world are welcome.

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