Ngoc Duy Pham

Sungkyunkwan University, Sŏul, Seoul, South Korea

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Publications (6)1.11 Total impact

  • Ngoc Duy Pham · Trong Duc Le · KwangJin Park · Hyunseung Choo
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    ABSTRACT: The development of large-scale wireless sensor networks engenders many challenging problems. Examples of such problems include how to dynamically organize the sensor nodes into clusters and how to compress and route the sensing information to a remote base station. Sensed data in sensor systems reflect the spatial and temporal correlations of physical attributes existing intrinsically in the environment. Noteworthy efficient clustering schemes and data compressing techniques proposed recently leverage the spatiotemporal correlation. These include the framework of Liu et al. and schemes introduced by Gedik et al. However, the previous clustering schemes are based on an impractical assumption of a single-hop network architecture and their cluster construction communication cost is relatively expensive. On the other hand, the computational overhead of recent compressing techniques (e.g. the work of Liu et al. and Douglas et al.) is quite significant; therefore, it is hard for sensor nodes with limited processing capability to perform these techniques. With such motivation, we propose a novel and one-round distributed clustering scheme based on spatial correlation between sensor nodes, and propose a novel light-weight compressing algorithm to effectively save the energy at each transmission from sensors to the base station based on temporal correlation of the sensed data. Besides, the aim of the proposed clustering scheme is not only to group the nodes with the highest similarity in observations into the same cluster, but also to construct and maintain a dynamic backbone for efficient data collection in the networks (with the consideration of sink mobility). Computer simulation shows that the proposed schemes significantly reduce the overall number of communications in the cluster construction phase and the energy consumed in each transmission, while maintaining a low variance between the readings of sensor nodes in the same clusters and high reliability of the compressed data. Copyright © 2010 John Wiley & Sons, Ltd.
    No preview · Article · Nov 2010 · International Journal of Communication Systems
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    Ngoc Duy Pham · Hyunseung Choo
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    ABSTRACT: Flooding is a fundamental, critical, and indispensable operation for supporting various applications and protocols in wireless ad hoc networks. The traditional flooding scheme generates excessive redundant packet retransmissions, however, causing contention and packet collisions, and ultimately wasting precious limited bandwidth and energy. Recently, some flooding schemes have been studied to avoid those problems, but these algorithms either perform well in redundant transmissions or require that the node maintain information about neighbors more than one hop away. One of the most efficient approaches is found in the work of Liu et al., which uses only 1-hop neighbor information. The advantage of this scheme is that it achieves local optimality in terms of the number of retransmitting nodes, although it still produces many redundant transmissions. In this paper, we propose an efficient flooding protocol that minimizes flooding traffic by leveraging location information of 1-hop neighbor nodes. Our scheme is receiver-based, which means that each receiver of a flooding message determines whether it should forward the message based on the given retransmission rule. Simulation results show that our scheme is highly efficient. It is able to reduce the number of forward nodes almost to that of the lower bound but maintains a high delivery ratio.
    Preview · Conference Paper · Jan 2009
  • Inyoung Shin · Ngoc Duy Pham · Hyunseung Choo
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    ABSTRACT: In wireless sensor networks, an important issue often faced in geographic routing is the “local minimum phenomenon.” To mitigate the local minimum issue, when the routing process becomes stuck at hole boundary nodes, the existing perimeter routing tends to route data packets along the boundaries of the holes. However, this may enlarge the hole, causing the “first hole diffusion” problem. On the other hand, the existing hole detour scheme based on the virtual ellipse forwards data packets to outside the virtual ellipse. This may generate other holes around the existing hole - the “second hole diffusion” problem. Therefore, we propose a novel virtual convex polygon based hole boundary detection and time delay based hole detour scheme. The proposed scheme solves first and second hole diffusion problems. Comprehensive simulation results show that the proposed scheme provides approximately 22% and 16% improvements in terms of the packet delivery ratio and the network lifetime, respectively.
    No preview · Conference Paper · Jan 2009
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    Trong Duc Le · Ngoc Duy Pham · Hyunseung Choo
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    ABSTRACT: In the development of various large-scale sensor systems, a particularly challenging problem is how to dynamically organize the sensor nodes into clusters and route the sensing information to a remote base station. By leveraging the spatial correlation, there have been some noteworthy clustering schemes proposed recently, such as EEDC and ASAP. However, they are based on an impractical assumption of single-hop network architecture, and the cluster construction communication cost is relatively high. With such motivation, we introduce a novel distributed clustering scheme to group the sensor nodes that have the highest similarity in observations into the same cluster and also construct a dynamic backbone of efficient data collection in wireless sensor networks. Accordingly, with a given spatial accuracy requirement, only part of the sensor nodes in each cluster should be required to work for sampling and data transmitting in order to save energy. Comprehensive computer simulations show that the proposed scheme significantly reduces the overall number of communications in the cluster construction phase, whilst maintaining the small variance between the readings of sensor nodes in the same clusters.
    Preview · Conference Paper · Sep 2008
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    Ngoc Duy Pham · Trong Duc Le · Hyunseung Choo
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    ABSTRACT: Continuous data collection applications in wireless sensor networks require sensor nodes to continuously sample the surrounding physical phenomenon and then return the data to a processing center. Battery-operated sensors have to avoid heavy use of their wireless radio by compressing the time series sensed data instead of transmitting it in raw form. One of the most commonly used compacting methods is piecewise linear approximation. Previously, Liu et al. proposed a greedy PLAMLiS algorithm to approximate the time series into a number of line segments running in Theta(n<sup>2</sup>logn) time, however this is not appropriate for processing in the sensors. Therefore, based on our study we propose an alternative algorithm which obtains the same result but needs a shorter running time. Based on theoretical analysis and comprehensive simulations, it is shown that the new proposed algorithm has a competitive computational cost of Theta(nlogn) as well as reducing the number of line segments and so it can decrease the overall radio transmission load in order to save energy of the sensor nodes.
    Preview · Conference Paper · Aug 2008
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    Ngoc Duy Pham · Hyunseung Choo
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    ABSTRACT: A mobile ad-hoc network is a self-configuring network of user devices that are connected by wireless links in infrastructure-less situation. These kinds of networks have many challenges such as unreliable links, lack of scalability, limited resources, etc. and energy consumption is a major issue in designing network protocols because of battery constraints. In on-demand multi-hop routing protocols e.g. AODV and DSR, the route discovery process uses expanding ring search heuristic algorithm for reducing broadcast overhead and saving energy consumption. However, based on our observation we see that there are still some redundant broadcasts of this process that causes overhead, wasted energy, and increased collisions in the network. Here we propose a method which solves the redundant broadcasts of route discovery based on expanding ring search. The performance evaluation results show that by applying the proposed scheme, we can reduce the overhead of expanding ring search based route discovery up to about 20%, and therefore the total energy consumption of AODV is decreased by 15%.
    Preview · Conference Paper · Jun 2008

Publication Stats

55 Citations
1.11 Total Impact Points

Institutions

  • 2008-2010
    • Sungkyunkwan University
      • Department of Electronic, Electrical and Computer Engineering
      Sŏul, Seoul, South Korea