• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.2
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• pp.49-56
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• 2011

One of the most important VANET applications is providing active safety by broadcasting emergency messages. In order to prevent broadcast storm of flooding-based broadcasting scheme in which any node receiving message will rebroadcast, the existing protocols use the different methods to limit the number of relay nodes. Nevertheless, the existing protocols have low delivery ratio with high traffic density and cause message overhead. Currently, the dramatic increase in the number of vehicles equipped with Global Positioning System (GPS) and onboard radar created new application scenarios that were not feasible before. Consequently, we proposed a broadcasting protocol that selects relay node by using GPS-based position information and detecting neighboring vehicles with the help of onboard radar to. Simulation results show that our proposed protocol has better performance than the existing schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4844-4864
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• 2017

Interference-aware routing protocol design for underwater wireless sensor networks (UWSNs) is one of the key strategies in reducing packet loss in the highly hostile underwater environment. The reduced interference causes efficient utilization of the limited battery power of the sensor nodes that, in consequence, prolongs the entire network lifetime. In this paper, we propose an energy-efficient interference-aware routing (EEIAR) protocol for UWSNs. A sender node selects the best relay node in its neighborhood with the lowest depth and the least number of neighbors. Combination of the two routing metrics ensures that data packets are forwarded along the least interference paths to reach the final destination. The proposed work is unique in that it does not require the full dimensional localization information of sensor nodes and the network total depth is segmented to identify source, relay and neighbor nodes. Simulation results reveal better performance of the scheme than the counterparts DBR and EEDBR techniques in terms of energy efficiency, packet delivery ratio and end-to-end delay.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.788-794
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• 2007

The policy of US DoD is moving towards implementation of Network Centric Warfare(NCW) concepts. NCW is commonly described as the integration and synchronization of four key interdependent elements such as command and control, sensor system, engagement systems and the network. Therefore the military policy of Korea military is needed to access and examine the policy of NCW communication environment and crypto communication, which is able to apply it. In this case study, We are reviewed the security framework of the concept of network centric warfare in the centering around the US. It is introduced the core technology in the network centric warfare, and it is reviewed the security framework such as, the requirements of security, the characteristics security of global information grid, joint tactical radion system, net centric enterprise services, transformational communication satellite, in the basis of core technology, and analysis the effect of crypto communication relay between command node and surbornate node in NCW environment. This report support the assistance, which is considered the elements of surrounding effects in the varied crypto communication research area of NCW.

• Journal of Advanced Information Technology and Convergence
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• v.9 no.1
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• pp.25-37
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• 2019

Power-line communication (PLC) has influenced smart grid development. In addition, PLC has also been instrumental in current research on internet-of-things (IoT). Due to the implementation of PLC in smart grid and IoT environments, strides have been made in PLC and its combination with the wireless system to form a hybrid communication system. Also, PLC has evolved from a single-input-single-output (SISO) configuration to multiple-input-multiple-output (MIMO) configuration system, and from a point-to-point communication system to cooperative communication systems. In this work, we extend a MIMO wireless two-way amplify-and-forward (AF) cooperative communication system to a hybrid PLC and wireless (PLC/W) system configuration. We then maximize the weighted sum-rate for the hybrid PLC/W by optimizing the precoders at each node within the hybrid PLC/W system. The sum-rate problem was found to be non-convex, therefore, an iterative algorithm is used to find the optimal precoders that locally maximize the system sum-rate. For our simulation results, we compare our proposed hybrid PLC/W configuration to a PLC only and wireless only configuration at each node. Due to an improvement in system diversity, the hybrid PLC/W configuration outperformed the PLC only and wireless only system configurations in all simulation results presented in this paper.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.6
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• pp.173-180
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• 2021

Non Orthogonal Multiple Access (NOMA) is a technology to guarantee the explosively increased Quality of Service(QoS) of users in 5G networks. NOMA can remove the frequent orthogonality in Orthogonal Multiple Access (OMA) while allocating the power differentially to classify user signals. NOMA can guarantee higher communication speed than OMA. However, the NOMA has one disadvantage; it consumes a more energy power when the distance increases. To solve this problem, relay nodes are employed to implement the cooperative NOMA control idea. In a cooperative NOMA network, relay node participations for cooperative communications are essential. In this paper, a new bandwidth allocation scheme is proposed for cooperative NOMA platform. By employing the idea of Vickrey-Clarke-Groves (VCG) mechanism, the proposed scheme can effectively prevent selfishly actions of relay nodes in the cooperative NOMA network. Especially, base stations can pay incentives to relay nodes as much as the contributes of relay nodes. Therefore, the proposed scheme can control the selfish behavior of relay nodes to improve the overall system performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.774-784
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• 2009

A wireless sensor network consisting of a large number of nodes with limited battery power should minimize energy consumption at each node to prolong the network lifetime. To improve the sensitivity of wireless sensor networks, an efficient scheduling algorithm and energy management technology for minimizing the energy consumption at each node is desired. ill this paper, we propose energy-aware routing mechanism for maximum lifetime and to optimize the solution quality for sensor network maintenance and to relay node from its adjacent cluster heads according to the node"s residual energy and its distance to the base station. Proposed protocol may minimize the energy consumption at each node, thus prolong the lifetime of the system regardless of where the sink is located outside or inside the cluster. Simulation results of proposed scheme show that our mechanism balances the energy consumption well among all sensor nodes and achieves an obvious improvement on the network lifetime. To verify propriety using NS-2, proposed scheme constructs sensor networks adapt to current model and evaluate consumption of total energy, energy consumption of cluster head, average energy dissipation over varying network areas with HEED and LEACH-C.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.634-639
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• 2008

In mobile communication networks, the main power consumption is due to the actual transmissions power. Therefore, power efficiency network structures have gained considerable importance in mobile multi-hop systems and networks in recent years. In this paper, the performance of mobile multi-hop wireless system with M-QAM signal and forward error control (FEC) technique are analyzed The FEC technique uses extra processing power related to encoding and decoding, it is need complex functions to be built into the communication node. The probability of receiving a correct bit and codeword for relaying a data frame over h hop relay station to the final station is evaluated as a function of channel parameter and number of hops, and the distance between the different station.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.137-140
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• 2011

최근 활발하게 연구되고 있는 4G 이동 통신 시스템의 하나인 LTE-Advanced 시스템에서 릴레이 기법은 주요 기술로써 고려되고 있다. 릴레이 기법을 도입함으로써 LTE-Advanced 시스템은 셀 가장자리 유저들에게 좋은 성능의 서비스를 제공할 수 있을 뿐 아니라 셀 커버리지를 늘릴 수 있을 것으로 기대된다. 하지만 LTE-Advanced 시스템에 릴레이 기술을 도입하는 구체적인 기법은 아직 연구되지 못하고 있다. 이러한 상황에서 우리는 기존의 직교 할당 방식과 중첩 할당 방식을 이용하여 릴레이 기법을 도입시 새로운 자원 할당 방법을 제안할 것이다. 제안 기법의 기본 아이디어는 서비스 지역에 진입한 단말이 채널 정보를 이용하여 eNB(eNodeB)로 접속할지 RS(Relay Station)로 접속할지를 결정한다. 기존의 직교 할당 방식과 중첩 할당 방식을 그대로 적용하는 경우와 비교하여 우리가 새로 제안하는 자원 할당 기법은 전송률 뿐만 아니라 공정성 측면에서도 우수한 성능을 나타낸다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.580-581
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• 2018

In order to reduce end-to-end delay in EH-WSN (energy harvestin wireless sensor netowk), medium access control protocols using multi-hop routing technique have been studied. In a real environment, there are many situations where it is difficult to harvest enough energy than the energy consumed. Therefore, it is required to design a MAC protocol that allows nodes to reliably relay data without exhausting power in multi-hop transmission. In this paper, we propose a power-efficient MAC protocol that can select the relay node according to the residual power and the energy collection rate to increase network lifetime.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.136-143
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• 2010

In this paper, we investigate decode-and-forward (DF) relaying systems with a direct link between the source and the destination node. The objective of this paper is to determine the better relaying strategy between 3-hop DF relaying and dual-hop DF relaying with the best relay selection. Assuming Rayleigh fading channels, we present closed-form outage probability of the 3-hop relaying and the dual-hop relaying, respectively, and compare the performances by numerical investigation. Numerical results show that if the channel is poor, the outage performance of the 3-hop relaying is better than the dual-hop relaying.