• 한국정보통신학회논문지
• /
• 제26권2호
• /
• pp.239-250
• /
• 2022

LoRa는 네트워크에 대부모 트리 구조와 처프 확산 스펙트럼을 도입한 물리 계층 기술로 높은 신뢰도의 장거리 통신을 제공한다. LoRa의 트리 네트워크에서 자식 노드는 단일 부모가 아닌 여러 노드에게 동시에 메시지를 전송할 수 있기 때문에 동일 부하가 네트워크에 가해진다면 패킷 전달률은 게이트웨이의 수의 증가에 따라 증가한다. 하지만 알로하류의 원시적 매체 접근 제어의 한계 때문에 이러한 트리 환경에서도 부하의 증가에 따라 네트워크의 이용률은 하락한다. 본 논문에서는 동일 주파수를 동일 시간대, 동일 지역에서 사용하는 공간 분할 다중 접근 방식을 제안한다. 본 기법은 수집된 신호 세기의 분포로부터 송신 전력을 도출하여 같은 시간, 다른 게이트웨이에서 각기 다른 패킷이 수신되도록 제어한다. 즉, 포획 효과를 의도적으로 활용하여 저전력 광역 네트워크의 노드 수용력을 향상시킨다.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2008년도 추계학술대회 논문집
• /
• pp.229-234
• /
• 2008

The new millennium has started with several innovations driven by fast evolution of the technologies in energy sector. A strong impulse towards the diffusion of new economical efficient technologies regulatory incentives related to energy production from renewable source and a small scale building trigeneration and to promotion of more sustainable environmental-friendly generation solutions, the evolution of electricity markets, more and more binding local emission constraints, and the need for improving the security of supply to reduce the energy system vulnerability. The 24 percentage energy quantify of total energy consumption consumes in commercial buildings and residential houses and the 30% portion of total $CO_2$ emissions covers also in the commercial buildings and residential houses sector. To cope with efficiently this energy sinuation in building sector, Building microgrid or building tooling, heating & power(BCHP) system has been interested in recent day due to meeting thermal and electric energy requirements efficiently and with appropriate energy quality. A multi agent system is a collective of intelligent agents that communicate with each other and work cooperatively to achieve common goals. Also, it is to medicate and coordinate communication between Control Areas and Security Coordinators for teal-time control of the BCHP system and the power pid. In this new circumstance, it is very important to integrate the power and energy delivery system and the information system(communication, networks, and intelligent equipment) that controls it. Therefore, development of smart control modules with open communication protocol and seamlessly interchange the data and information between control network and data network including extranet and intranet give a great meanings. We designed and developed the TCP/IP-CAN IED agent modules and ModBus./LonTalk/(TCP/IP) IED agent ones to configure the multi-agent system based smart energy network of commercial buildings and also intelligent algorithms for inverter fault diagnostics which ran be operated in control level or agent level network.

• International Journal of Computer Science & Network Security
• /
• 제22권10호
• /
• pp.191-200
• /
• 2022

Constrained Application Protocol (CoAP) is a standardized protocol by the Internet Engineering Task Force (IETF) for the Internet of things (IoT). IoT devices have limited computation power, memory, and connectivity capabilities. One of the significant problems in IoT networks is congestion control. The CoAP standard has an exponential backoff congestion control mechanism, which may not be adequate for all IoT applications. Each IoT application would have different characteristics, requiring a novel algorithm to handle congestion in the IoT network. Unnecessary retransmissions, and packet collisions, caused due to lossy links and higher packet error rates, lead to congestion in the IoT network. This paper presents an adaptive congestion control protocol for CoAP, Adaptive Congestion Control with a Backoff algorithm (ACCB). AACB is an extension to our earlier protocol AdCoCoA. The proposed algorithm estimates RTT, RTTVAR, and RTO using dynamic factors instead of fixed values. Also, the backoff mechanism has dynamic factors to estimate the RTO value on retransmissions. This dynamic adaptation helps to improve CoAP performance and reduce retransmissions. The results show ACCB has significantly higher goodput (49.5%, 436.5%, 312.7%), packet delivery ratio (10.1%, 56%, 23.3%), and transmission rate (37.7%, 265%, 175.3%); compare to CoAP, CoCoA+ and AdCoCoA respectively in linear scenario. The results show ACCB has significantly higher goodput (60.5%, 482%,202.1%), packet delivery ratio (7.6%, 60.6%, 26%), and transmission rate (40.9%, 284%, 146.45%); compare to CoAP, CoCoA+ and AdCoCoA respectively in random walk scenario. ACCB has similar retransmission index compare to CoAp, CoCoA+ and AdCoCoA respectively in both the scenarios.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권4호
• /
• pp.2002-2019
• /
• 2017

RPL routing protocol for low-power and lossy networks is an Internet Engineering Task Force (IETF) recommended IPv6 based protocol for routing over Low power Lossy Networks (LLNs). RPL is proposed for networks with characteristics like small packet size, low bandwidth, low data rate, lossy wireless links and low power. RPL is a proactive routing protocol that creates a Directed Acyclic Graph (DAG) of the network topology. RPL is increasingly used for Internet of Things (IoT) which comprises of heterogeneous networks and applications. RPL proposes a single path routing strategy. The forwarding technique of RPL does not support multiple paths between source and destination. Multipath routing is an important strategy used in both sensor and ad-hoc network for performance enhancement. Multipath routing is also used to achieve multi-fold objectives including higher reliability, increase in throughput, fault tolerance, congestion mitigation and hole avoidance. In this paper, M-RPL (Multi-path extension of RPL) is proposed, which aims to provide temporary multiple paths during congestion over a single routing path. Congestion is primarily detected using buffer size and packet delivery ratio at forwarding nodes. Congestion is mitigated by creating partially disjoint multiple paths and by avoiding forwarding of packets through the congested node. Detailed simulation analysis of M-RPL against RPL in both grid and random topologies shows that M-RPL successfully mitigates congestion and it enhances overall network throughput.

• 한국전자통신학회논문지
• /
• 제14권5호
• /
• pp.927-934
• /
• 2019

최근 모바일 기기는 사용자 요구에 따라 다양한 기능이 있는 소형 컴퓨터의 형태로 발전하였다. 모바일 기기의 다양한 기능을 구현하기 위해 실장되는 AP(: Application processor)와 무선통신용 모뎀 및 고성능 카메라 외 다양한 인터페이스를 위한 IC 들의 안정적인 동작을 위해서는 전원 공급 네트워크 설계에 주의가 필요하다. 본 논문에서는 실장 밀도 제한으로 인해 배선형으로 설계해야하는 모바일 기기의 전원 공급 네트워크의 안정성 확보를 위해 드라이버 IC 칩에서 요구하는 목표 임피던스를 만족하도록 디커플링 캐패시터의 위치, 용량, 개수 등의 설계 파라메터를 최적화하는 방법에 대해 분석하고 시뮬레이션을 통해 검증하였다. 본 논문을 통해 제안된 배선형 전원 공급 네트워크 설계 방법은 모바일 어플리케이션 외 고속신호 전송선로가 포함되는 다양한 응용분야에 확대 적용될 수 있을 것으로 판단된다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제17권8호
• /
• pp.2140-2156
• /
• 2023

The Wireless Sensor Network (WSN), is constructed out of teeny-tiny sensor nodes that are very low-cost, have a low impact on the environment in terms of the amount of power they consume, and are able to successfully transmit data to the base station. The primary challenges that are presented by WSN are those that are posed by the distance between nodes, the amount of energy that is consumed, and the delay in time. The sensor node's source of power supply is a battery, and this particular battery is not capable of being recharged. In this scenario, the amount of energy that is consumed rises in direct proportion to the distance that separates the nodes. Here, we present a Hybrid Firefly Glow-Worm Swarm Optimization (HF-GSO) guided routing strategy for preserving WSNs' low power footprint. An efficient fitness function based on firefly optimization is used to select the Cluster Head (CH) in this procedure. It aids in minimising power consumption and the occurrence of dead sensor nodes. After a cluster head (CH) has been chosen, the Glow-Worm Swarm Optimization (GSO) algorithm is used to figure out the best path for sending data to the sink node. Power consumption, throughput, packet delivery ratio, and network lifetime are just some of the metrics measured and compared between the proposed method and methods that are conceptually similar to those already in use. Simulation results showed that the proposed method significantly reduced energy consumption compared to the state-of-the-art methods, while simultaneously increasing the number of functioning sensor nodes by 2.4%. Proposed method produces superior outcomes compared to alternative optimization-based methods.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권3호
• /
• pp.1481-1501
• /
• 2019

In opportunistic network, the behavior of a node is autonomous and has social attributes such as selfishness.If a node wants to forward information to another node, it is bound to be limited by the node's own resources such as cache, power, and energy.Therefore, in the process of communication, some nodes do not help to forward information of other nodes because of their selfish behavior. This will lead to the inability to complete cooperation, greatly reduce the success rate of message transmission, increase network delay, and affect the overall network performance. This article proposes a hybrid incentive mechanism (Mim) based on the Reputation mechanism and the Credit mechanism.The selfishness model, energy model (The energy in the article exists in the form of electricity) and transaction model constitute our Mim mechanism. The Mim classifies the selfishness of nodes and constantly pay attention to changes in node energy, and manage the wealth of both sides of the node by introducing the Central Money Management Center. By calculating the selfishness of the node, the currency trading model is used to differentiate pricing of the node's services. Simulation results show that by using the Mim, the information delivery rate in the network and the fairness of node transactions are improved. At the same time, it also greatly increases the average life of the network.

• 한국전기전자재료학회논문지
• /
• 제19권11호
• /
• pp.1055-1060
• /
• 2006

High temperature superconducting(HTS) power cable is expected to be used for power transmission lines supplying electric power for densely populated cities in the near future. Since HTS power cable is capable of the high current density delivery with low power loss, the cable size can be compact comparing with the conventional cable whose capacity is same. In this paper, the authors propose the real time simulation method which puts a teal HTS wire into the simulated 22.9 kV utility grid system using Real Time Digital Simulator (RTDS). For the simulation analysis, test sample of HTS wire was actually manufactured. And the transient phenomenon of the HTS wire was analyzed in the simulated utility power grid. This simulation method is the world first trial in order to obtain much better data for installation of HTS power device into utility network.

• 인터넷정보학회논문지
• /
• 제15권4호
• /
• pp.1-8
• /
• 2014

무선 인체 센서 네트워크 시스템은 기존의 센서 네트워크 시스템과는 달리 장치가 소형이고 배터리 용량이 매우 제약적이다. 그리고 링크 채널의 특성, 센서 노드를 장착한 사람의 움직임, 부착된 센서 노드의 위치, 전송 전력을 조절하는 알고리즘 등에 따라 다양한 채널 환경이 형성될 수 있다. 따라서 이와 같은 제약사항 및 환경을 극복하고 센서 노드의 에너지를 효율적으로 관리하기위해 본 논문에서는 사람의 움직임과 센서 노드의 위치, 전송 전력 조절 알고리즘을 종합적으로 고려한 상태에서 최적의 전송 전력세기 값을 찾기 위한 실험을 수행한다. 그리고 실험의 결과를 바탕으로 에너지 소모와 패킷 전송률 측면에서 분석을 실시한다. 이를 통해 본 논문은 무선 인체 센서 네트워크 시스템에 적합한 수신 신호 세기 값과 그 값에 접근하기 위해 허용할 수 있는 수신 신호 세기의 범위 설정에 따른 효율성을 비교 평가한다.

• Management Science and Financial Engineering
• /
• 제20권2호
• /
• pp.7-12
• /
• 2014

Content Delivery Network (CDN) has evolved to overcome a network bottleneck and improve user perceived Quality of Service (QoS). A CDN replicates contents from the origin server to replica servers to reduce the overload of the origin server. CDN providers would try to achieve an acceptable performance at the least cost including the storage space or processing power. In this paper, we introduce a new optimization model for the CDN design problem considering the user perceived QoS and single path (non-bifurcated) routing constraints and analyze the computational complexity for some special cases.