• Journal of information and communication convergence engineering
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• 제12권3호
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• pp.135-139
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• 2014

Opportunistic routing was originally introduced in various multihop network environments to reduce the number of hops in such a way that, among the relays that decode the transmitted packet for the current hop, the one that is closest to the destination becomes the transmitter for the next hop. Unlike the conventional opportunistic routing case where there is a single active S-D pair, for an ad hoc network in the presence of fading, we investigate the performance of parallel opportunistic multihop routing that is simultaneously performed by many source-destination (S-D) pairs to maximize the opportunistic gain, thereby enabling us to obtain a logarithmic gain. We first analyze a cut-set upper bound on the throughput scaling law of the network. Second, computer simulations are performed to verify the performance of the existing opportunistic routing for finite network conditions and to show trends consistent with the analytical predictions in the scaling law. More specifically, we evaluate both power and delay with respect to the number of active S-D pairs and then, numerically show a net improvement in terms of the power-delay trade-off over the conventional multihop routing that does not consider the randomness of fading.

• Journal of information and communication convergence engineering
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• 제1권3호
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• pp.123-128
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• 2003

This paper has addressed the implementation of the single rate Rate Adaptive Shaper(srRAS) described in RFC2963. This shaper has been proposed to use at the ingress of differentiated services networks providing Assured Forwarding Per Hop Behavior (AFPHB). srRAS is typically used in conjunction with single rate Three Color Marker(srTCM) described in RFC2697. srRAS itself is the tail-drop FIFO that is drained at a variable rate, and srTCM is the marker with metering function. G-srRAS is the same as srRAS except that RAS receives the green token state information from the downstream srTCM to avoid delaying a packet in RAS although there are sufficient tokens available to color the packet green. In this paper, we have addressed the algorithm and the architecture of srRAS, and the scheme to implement srRAS using VHDL(Very high-speed integrated circuit Hardware Description Language) and its related tools.

• 대한전자공학회논문지TC
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• 제42권12호
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• pp.141-148
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• 2005

본 논문은 RFC2697에서 제안된 srTCM (single rate Three Color Marker)의 설계에 관한 것이다. srTCM은 AFPHB(Assured Forwarding Per Hop Behavior)를 제공하는 DS (Differentiated Service) 네트워크의 Ingress에서 사용되도록 제안되었다. srTCM은 metering 기능을 가진 marker이며, 토큰 갱신기능과 marking 기능으로 구성된다. 토큰 갱신 기능은 듀얼 토큰버킷을 사용하며, marking 기능은 토큰 값을 입력 패킷의 길이와 비교하여, 그 결과를 IP QoS 필드 (ToS 필드)에 마킹한다. 본 논문에서는 이와 같은 srTCM를 VHDL과 FPGA를 이용하여 설계하여 하나의 chip으로 구현하였다.

• 한국콘텐츠학회논문지
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• 제21권8호
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• pp.10-19
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• 2021

차량 간의 콘텐츠 공유를 위해서 Content-Centric Vehicular Network (CCVN)에 관한 연구가 진행되었다. CCNV에서 단일 홉 또는 다중 홉 기반의 기본의 콘텐츠 탐색 및 전달 기법들은 낮은 콘텐츠 탐색 확률과 높은 네트워크 트래픽 오버헤드를 가진다. 본 논문은 콘텐츠 탐색 확률을 높이고 네트워크 트래픽을 줄이기 위해 RSU를 활용한 콘텐츠 탐색 및 전송 기법을 제안한다. 제안 기법에서 RSU는 통신 범위 내에 속한 차량들의 이동성 정보를 이용하여 일정시간 간격으로 커뮤니케이션 트리를 구성한다. 커뮤니케이션 트리가 구성된 이후, RSU는 콘텐츠 요청 차량의 요청에 따라 후보 차량들 중에 최소 비용으로 콘텐츠를 제공할 수 있는 차량을 최적의 콘텐츠 제공 차량으로 선택한다. 선택된 콘텐츠 제공 차량은 구성된 커뮤니케이션 트리를 통해 콘텐츠 요청 차량에게 콘텐츠를 전송한다. 시뮬레이션 결과에서는 제안 기법이 기존 기법들보다 더 나은 성능을 보여준다.

• 정보처리학회논문지C
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• 제14C권7호
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• pp.583-588
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• 2007

이동 애드 혹 네트워크는 기반 망의 도움 없이 모바일 노드의 자유로운 참여와 이탈에 의해 임시적인 네트워크를 구성하기 용이하다. 이러한 모바일 노드는 한정된 에너지에 의존한다. 그래서 무선 애드 혹 네트워크에서 에너지와 관련된 문제들이 중요한 연구과제로 다루어진다. 모바일 노드의 에너지 소비를 줄이기 위해 IEEE 802.11 PSM를 적용한 다중 홉 애드 혹 네트워크 모델에 대해서 최근 많은 연구가 이루어졌다. IEEE 802.11 PSM은 단일 홉 애드 혹을 가정하고 제안되었다. IEEE 802.11 PSM을 다중 홉 애드 혹 네트워크에 적용을 하게 될 경우 경로설정 메시지를 받지 못한 모바일 노드에 의해 우회하는 경로가 발생하게 된다. 우회하는 경로는 전송지연뿐만 아니라 모바일 노드의 에너지 소비를 증가시키게 된다. 본 논문에서는 경로 설정 메시지를 전송받지 못한 모바일 노드에 의해 발생하는 우회하는 경로를 최적의 경로로 재설정하는 알고리즘을 제안하였다. 모바일 노드는 자신의 송수신 범위에 있는 노드들의 데이터를 엿들을 수 있다. 무선 매체는 동일한 대역을 사용하는 모든 모바일 노드에 의해 공유되어진다. 이러한 매체의 특성을 이용하여 모든 모바일 노드들은 우회경로를 감시하고 우회경로가 발생하였을 경우 자신의 라우팅 테이블의 정보를 수정하거나 이웃한 모바일 노드에게 라우팅 업데이트 요청 메시지를 보내어 최적의 경로로 재설정하게 된다. 우회경로를 최적의 경로로 재설정함으로써 전송지연과 불필요한 에너지 소비를 줄일 수 있었다. 시뮬레이션을 통해 제안 알고리즘을 수행하기위한 오버헤드는 무시할 수 있을 정도로 작다는 것을 알 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권5호
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• pp.1540-1560
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• 2022

Latest technological innovation in the development of compact lower power radios has led to the explosion of Internet of Things. With Wi-Fi, Zigbee and other physical layer protocols offering short coverage area there was a need for a RF protocol that had a larger coverage area with low power consumption. LoRa offers Long Range with lower power consumption. LoRa offers point to point and point to multipoint connections. with Single hop communication in place the need for routing protocols are eliminated. LoRa Wide Area Network stack can accommodate thousands of nodes under a single LoRa gateway with a single hop communication between the end nodes and LoRaWAN gateway. This paper takes an experimental approach to analyze the basic physical layer parameters of LoRa and the practical coverage offered by a LoRaWAN under highly dense urban conditions with variable topography. The insights gained from the practical deployment of the LoRaWAN network, and the subsequent performance analysis is used to design a novel public utility monitoring platform. The second half of the papers is designing a robust platform to integrate both existing wired sensor water meters, current and future generation wireless water meters. The Common Automated Metering Platform is designed to integrate both wired sensors and wireless (LoRaWAN and Wi-Fi) supported water meters. This integrated platform reduces the number of nodes under each LoRaWAN gateway and thus improves the scalability of the network. This architecture is currently designed to accommodate one utility application but can be modified to integrate multi-utility applications.

• Journal of Communications and Networks
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• 제12권2호
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• pp.103-113
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• 2010

In this paper, a tradeoff between the total energy consumption-per-bit and the end-to-end rate under spatial reuse in wireless multi-hop network is developed and analyzed. The end-to-end rate of the network is the number of information bits transmitted (end-to-end) per channel use by any node in the network that is forwarding the data. In order to increase the bandwidth efficiency, spatial reuse is considered whereby simultaneous relay transmissions are allowed provided there is a minimum separation between such transmitters. The total energy consumption-per-bit includes the energy transmitted and the energy consumed by the receiver to process (demodulate and decoder) the received signal. The total energy consumption-per-bit is normalized by the distance between a source-destination pair in order to be consistent with a direct (single-hop) communication network. Lower bounds on this energy-bandwidth tradeoff are analyzed using convex optimization methods. For a given location of relays, it is shown that the total energy consumption-per-bit is minimized by optimally selecting the end-to-end rate. It is also demonstrated that spatial reuse can improve the bandwidth efficiency for a given total energy consumption-per-bit. However, at the rate that minimizes the total energy consumption-per-bit, spatial reuse does not provide lower energy consumption-per-bit compared to the case without spatial reuse. This is because spatial reuse requires more receiver energy consumption at a given end-to-end rate. Such degraded energy efficiency can be compensated by varying the minimum separation of hops between simultaneous transmitters. In the case of equi-spaced relays, analytical results for the energy-bandwidth tradeoff are provided and it is shown that the minimum energy consumption-per-bit decreases linearly with the end-to-end distance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권1호
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• pp.178-202
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• 2012

In this paper, we first survey cross-layer architectures for Wireless Sensor Networks (WSNs) and Wireless Multimedia Sensor Networks (WMSNs). Afterwards, we propose a novel cross-layer architecture for QoS provisioning in clustered and multi-hop based WMSNs. The proposed architecture provides support for multiple network-based applications on a single sensor node. For supporting multiple applications on a single node, an area in memory is reserved where each application can store its network protocols settings. Furthermore, the proposed cross-layer architecture supports heterogeneous flows by classifying WMSN traffic into six traffic classes. The architecture incorporates a service differentiation module for QoS provisioning in WMSNs. The service differentiation module defines the forwarding behavior corresponding to each traffic class. The forwarding behavior is primarily determined by the priority of the traffic class, moreover the service differentiation module allocates bandwidth to each traffic class with goals to maximize network utilization and avoid starvation of low priority flows. The proposal incorporates the congestion detection and control algorithm. Upon detection of congestion, the congested node makes an estimate of the data rate that should be used by the node itself and its one-hop away upstream nodes. While estimating the data rate, the congested node considers the characteristics of different traffic classes along with their total bandwidth usage. The architecture uses a shared database to enable cross-layer interactions. Application's network protocol settings and the interaction with the shared database is done through a cross-layer optimization middleware.

• 한국통신학회논문지
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• 제37권5A호
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• pp.325-338
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• 2012

본 논문에서는 무선 인지(Cognitive Radio, CR) 기반의 다중 홉 릴레이 전송 환경에서 링크별 가용 주파수 자원을 할당하는 문제를 다룬다. 경로 탐색, 채널 센싱 및 판단, 자원 할당의 3단계 시나리오를 제시하고 컬러 다중 그래프 모델과 시분할 된 프레임 구조를 토대로 서비스 받는 사용자의 수를 최대화하는 최적화 문제로 수학적 모델링을 한다. 이에 대한 해법으로 단말 선택, 릴레이 및 경로 선택 그리고 각 홉별 주파수 자원 선택의 3단계로 구성되는 부 최적화된 종합적 자원관리 방안을 제시한다. 모의실험에서는 홉-별 시분할 된 프레임 구조를 가지는 셀룰러 기반 2차 시스템을 고려하였으며, 다중 홉 통신과 단일 홉 통신 간의 성능을 비교를 통해 무선인지 시스템에서 다중 홉 통신의 필요성을 보였다. 또한 다중 홉 통신 가운데 가장 우수한 홉 수와 그 환경에 대해 살펴보았다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권2호
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• pp.670-683
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• 2016

Network coding, as a new technique to improve the throughput, is studied combined with multi-relay model in this paper to address the challenges of long distance and power limit in deep space communication. First, an amplify-and-forward relaying approach based on analog network coding (AFNC) is proposed in multi-relay network to improve the capacity for deep space communication system, where multiple relays are introduced to overcome the long distance link loss. The design of amplification coefficients is mathematically formulated as the optimization problem of maximizing SNR under sum-power constraint over relays. Then for a dual-hop relay network with a single source, the optimal amplification coefficients are derived when the multiple relays introduce non-coherent noise. Through theoretic analysis and simulation, it is shown that our approach can achieve the maximum transmission rate and perform better over single link transmission for deep space communication.