http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
클라우드컴퓨팅에서 메시지패싱방식 응용프로그램의 효율적인 체크포인트 알고리즘
( Duc Tai Le ),( Manh Thuong Quan Dao ),( Minjoon Ahn ),( Huynseung Choo ) 한국정보처리학회 2011 한국정보처리학회 학술대회논문집 Vol.18 No.1
In this work, we study the checkpoint/restart problem for message-passing parallel applications running on cloud computing environment. This is a new direction which arises from the trend of enabling the applications to run on the cloud computing environment. The main objective is to propose an efficient checkpoint algorithm for message-passing parallel applications considering communications with external systems. We further implement the novel algorithm by modifying gSOAP and OpenMPI (the open source libraries) which support service calls and checkpoint message-passing parallel programs, especially. The simulation showed that additional costs to the executing and checkpointing application of the algorithm are negligible. Ultimately, the algorithm supports efficiently the checkpoint/restart service for message-passing parallel applications, that send requests to external services.
Distributed Construction of Connected Cover Graph in Wireless Sensor Networks
( Duc Tai Le ),( Thang Le Duc ),( Boram Hwang ),( Hyunseung Choo ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.1
In this paper, we consider the problem of scheduling sensor activity to prolong the network lifetime while guaranteeing both discrete target coverage and connectivity among all the active sensors and the sink, called connected target coverage (CTC) problem. We proposed a distributed scheme called Distributed Lifetime- Maximizing Scheme (DLMS) to solve the CTC problem. Our proposed scheme significantly reduces the cost of the construction of the connected cover graphs in comparison with the some conventional schemes. In addition, the energy consumption is more balanced so that the network lifetime will be increased. Our simulation results show that DLMS scheme performs much better than the conventional schemes in terms of the network lifetime.
Le, Duc-Tai,Im, Giyeol,Le Duc, Thang,Zalyubovskiy, Vyacheslav V.,Kim, Dongsoo S.,Choo, Hyunseung WILEY INTERSCIENCE 2018 WIRELESS COMMUNICATIONS AND MOBILE COMPUTING Vol.2018 No.-
<P>Minimum latency scheduling has arisen as one of the most crucial problems for broadcasting in duty-cycled Wireless Sensor Networks (WSNs). Typical solutions for the broadcast scheduling iteratively search for nodes able to transmit a message simultaneously. Other nodes are prevented from transmissions to ensure that there is no collision in a network. Such collision-preventions result in extra delays for a broadcast and may increase overall latency if the delays occur along critical paths of the network. To facilitate the broadcast latency minimization, we propose a novel approach, critical-path aware scheduling (CAS), which schedules transmissions with a preference of nodes in critical paths of a duty-cycled WSN. This paper presents two schemes employing CAS which produce collision-free and collision-tolerant broadcast schedules, respectively. The collision-free CAS scheme guarantees an approximation ratio of <TEX>$ (\Updelta -\mathrm{1})T$</TEX> in terms of latency, where <TEX>$ \Updelta $</TEX> denotes the maximum node degree in a network. By allowing collision at noncritical nodes, the collision-tolerant CAS scheme reduces up to 10.2 percent broadcast latency compared with the collision-free ones while requiring additional transmissions for the noncritical nodes experiencing collisions. Simulation results show that broadcast latencies of the two proposed schemes are significantly shorter than those of the existing methods.</P>
무선센서네트워크에서 데이터 병합 트리를 위한 자기치유 방법
( Duc Tai Le ),( Thang Le Duc ),염상길 ( Sanggil Yeom ),( Vyacheslav V. Zalyubovskiy ),추현승 ( Hyunseung Choo ) 한국정보처리학회 2015 한국정보처리학회 학술대회논문집 Vol.22 No.1
Data aggregation is a fundamental problem in wireless sensor networks that has attracted great attention in recent years. On constructing a robust algorithm for minimizing data aggregation delay in wireless sensor networks, we consider limited transmission range sensors and approximate the minimum-delay data aggregation tree which can only be built in networks of unlimited transmission range sensors. The paper proposes an adaptive method that can be applied to maintain the network structure in case of a sensor node fails. The data aggregation tree built by the proposed scheme is therefore self-healing and robust. Intensive simulations are carried out and the results show that the scheme could adapt well to network topology changes compared with other approaches.
Collision-tolerant broadcast scheduling in duty-cycled wireless sensor networks
Le, Duc Tai,Le Duc, Thang,Zalyubovskiy, Vyacheslav V.,Kim, Dongsoo S.,Choo, Hyunseung Academic Press 2017 Journal of parallel and distributed computing Vol.100 No.-
<P><B>Abstract</B></P> <P>The minimum-latency broadcast problem in duty-cycled wireless sensor networks has received significant attention over the last few years. A common approach for the problem is to assign collision-free transmitting times to forwarding nodes for disseminating a message from one source node to all other nodes according to their given duty-cycle schedules and transmission ranges. However, preventing collision for all transmissions may increase latency in the broadcast schedules. This paper proposes a novel strategy of Collision-Tolerant Scheduling (CTS) that offers an opportunity to reduce broadcast latency by allowing collisions at non-critical nodes to speed up the broadcast process for critical ones. The completion of broadcast scheduling, i.e. all nodes receive a broadcast message, is ensured by additionally transmitting the message to non-critical nodes experiencing collision. We employ the scheduling strategy in two proposed broadcast schemes: Degree-based CTS (DCTS) and MIS-based CTS (MCTS), which select forwarding nodes based on the node degree and maximal independent set information, respectively. The results of both theoretical analysis and simulation reveal the remarkable advantages of CTS in minimizing broadcast latency in duty-cycled WSNs. DCTS and MCTS guarantee approximation ratios of ( Δ − 1 ) T and 12 T in terms of broadcast latency, where Δ and T denote the maximum node degree and the number of time slots in a working period, respectively. The two schemes reduce to at least 94 percent of the broadcast latency compared with existing schemes, while slightly increasing the number of transmissions due to the additional transmissions. Thanks to the latency reduction, the proposed schemes require 93 percent less energy than existing ones.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel scheduling strategy for broadcast latency minimization in duty-cycled WSNs. </LI> <LI> Allowing collisions at non-critical nodes to speed up the broadcast process. </LI> <LI> The completion of broadcast scheduling is ensured by additional transmissions. </LI> <LI> Achieving significant improvement in both theoretical and simulation results. </LI> </UL> </P>
( Thang Le Duc ),( Duc Tai Le ),( Hyunseung Choo ) 한국정보처리학회 2014 한국정보처리학회 학술대회논문집 Vol.21 No.2
Handover is constantly a challenging issue in wireless networks. Most of the existing solutions are host-based, which are implemented on the wireless terminals and leave the decision making to the terminals. This paper studies the problem of network-based handover in the wireless networks with the constraints of low latency as well as low computational time. To address this problem, we employ the software-defined network (SDN) architecture to facilitate handover. According to the operational model of the SDN, we define a workflow for all involved network entities, and then design a framework implementing the workflow as a complete handover system. The proposed framework aims to establish a channel conveying the mobility-related information of devices and the context information of their vicinity from the switches/access routers to the controllers. Based on collected information, the controller can optimally execute the handover.