• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.211-217
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• 2017

In this paper, we propose a bidirectional full duplex MAC (Medium Access Control) protocol for underwater acoustic networks. An underwater sensor node can set a back-off timer according to the priority of transmission. When the back-off timer expires, the underwater sensor node acquires a transmission opportunity. If a source node wants to send data to a destination node, it broadcasts RTS (Request-To-Send) including ID of the destination node to neighbor nodes. The destination node receiving RTS sends CTS (Clear-To-Send) to the source node to inform the bidirectional full duplex communication. After the source node receives CTS, the source node and the destination node can send the data to each other. In the underwater environment, the existing MAC protocol may take a lot of time for successful transmission of data due to long underwater propagation delay. On the other hand, the proposed bidirectional full duplex MAC protocol improves the throughput by shortening the time for successful transmission of data. In this paper, we analyze the throughput of the proposed bidirectional full duplex MAC protocol. In addition, we show that the proposed bidirectional full duplex MAC protocol has better performance in the presence of the long underwater propagation delay compared with existing MAC protocols for underwater environments.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.1
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• pp.1-6
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• 2017

Recent researches on radio frequency energy harvesting networks(RF-EHNs) with limited energy resource like battery have been focusing on the development of a new scheme that can effectively extend the whole lifetime of a network to semipermanent. In order for considerable increase both in the amount of energy obtained from radio frequency energy harvesting and its charging effectiveness, it is very important to design a network that supports energy harvesting and data transfer simultaneously with the full consideration of various characteristics affecting the performance of a RF-EHN. In this paper, we proposes an interference-based charging aware routing protocol(ICARP) that utilizes interference information and charging time to maximize the amount of energy harvesting and to minimize the end-to-end delay from a source to the given destination node. To accomplish the research objectives, this paper gives a design of ICARP adopting new network metrics such as interference information and charging time to minimize end-to-end delay in energy harvesting wireless networks. The proposed method enables a RF-EHN to reduce the number of packet losses and retransmissions significantly for better energy consumption. Finally, simulation results show that the network performance in the aspects of packet transmission rate and end-to-end delay has enhanced with the comparison of existing routing protocols.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.179-187
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• 2014

The underlay protocol is a cognitive radio method in which secondary or cognitive users use the same frequency without affecting the quality of service (QoS) for the primary users. In addition, because of the broadcast characteristics of the wireless environment, some nodes, which are called eavesdropper nodes, want to illegally receive information that is intended for other communication links. Hence, Physical Layer Security is applied considering the achievable secrecy rate (ASR) to prevent this from happening. In this paper, a performance analysis of the amplify-and-forward scheme under an interference constraint and Physical Layer Security is investigated in the cooperative communication mode. In this model, the relays use an amplify-and- forward method to help transmit signals from a source to a destination. The best relay is chosen using an opportunistic relay selection method, which is based on the end-to-end ASR. The system performance is evaluated in terms of the outage probability of the ASR. The lower and upper bounds of this probability, based on the global statistical channel state information (CSI), are derived in closed form. Our simulation results show that the system performance improves when the distances from the relays to the eavesdropper are larger than the distances from the relays to the destination, and the cognitive network is far enough from the primary user.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.96-107
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• 2015

VANET technologies provide real-time traffic information for mitigating traffic jam and preventing traffic accidents, as well as in-vehicle infotainment service through Telematics/Intelligent Transportation System (ITS). Due to the rapid increasement of various requirements, the vehicle communication with a limited resource and the fixed frame architecture of the conventional techniques is limited to provide an efficient communication service. Therefore, a new flexible operation depending on the surrounding situation information is required that needs an adaptive design of the network architecture and protocol for efficiently predicting, distributing and sharing the context-aware information. In this paper, Vehicle-to-Infrastructure (V2I) based on communication between vehicle and a Road Side Units (RSU) and Vehicle-to-Vehicle (V2V) based on communication between vehicles are effectively combined in a new MAC architecture and V2I and V2V vehicles collaborate in management. As a result, many vehicles and RSU can use more efficiently the resource and send data rapidly. The simulation results show that the proposed method can achieve high resource utilization in accordance. Also we can find out the optimal transmission relay time and 2nd relay vehicle selection probability value to spread out V2V/V2I collaborative schedule message rapidly.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.114-121
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• 1998

This paper proposed a collision avoidance scheme to improve the network performance and priority control scheme to support real-time ATM applications in CIF(Cells in Frames), which carries ATM cells over existing Ethernet interfaces. The proposed scheme has optimized for the two nodes Ethernet, that is a typical CIF network, and doesn't require any hardware modification of existing Ethernet interface card. The collision avoidance scheme gives fair access opprtunities with minimized contention to the nodes by assigning different inter-frame gap to each element of CIF network. The priority control scheme guarantees preemptive transmission of real-time frames to the medium by exchanging queuing status information between two nodes. Therefore in this paper it is shown that CIF network which has both the collision avoidance scheme of MAC layer and the priority control scheme of CIF layer has a improved network performance and supports real-time ATM applications efficiently.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.215-220
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• 2012

Recently, one of the research topics is wireless Ad-Hoc network minimizing power consumption because of limited power. We propose optimal power allocation scheme of each transmit node and derive performance analysis of system that recently designed Double opportunistic relay system which fixed branch receiver to use more than efficient power consumption. Optimal power location scheme is shown that outage probability has always better performance than equal power allocation. Furthermore, we are known that outage probability is minimized by increasing average transmit relays to obtain the diversity gain when average channel power gain is less.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.4
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• pp.45-50
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• 2014

In this paper, we proposed a method using the user mobile device to overcome the interference constraint without building a cooperative communication system. In addition, in order to mitigate interference, we apply the user mobile device selection method, and then exploit power allocation scheme in the user mobile device. The proposed protocol is analyzed in the Rayleigh fading environment, and the performance system is evaluated in terms of the bit error rate and the outage probability. The simulation results showed that when the proposed transmission algorithm is applied, the interference can be mitigated. Further, network overload problems can be solved in the weak channel interference. Therefore, we can increase the network capacity without additional relay.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.83-87
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• 2009

The MAC protocol of HiperLAN/2 is based on TDMA/TDD. Mobile terminal acquires a data transmission opportunity as successfulness in channel competition through RCH (Random CHannel) phase. Therefore, AP (Access Point) be able to dynamically assign optimum RCH at next frame according to the number of success and collision. In this paper, we suggest scheme that fluctuate RCH (Random CHannel) number as fixed value considering success and collision for improvement of performance in HiperLAN/2. To prove efficiency of proposed scheme, a lots of simulations are conducted and analyzed in view of throughput and access delay.

• 정보화사회
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• s.185
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• pp.14-14
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• 2007

세계는 1990년대 중반 '정보화 혁명'에 이어 2000년대 중반 이후에는 '디지털 융합 혁명'이라는 새로운 물결에 직면해 있다. 디지털기술의 발전과 전송망의 광대역화에 따라 전통적으로 서로 다른 영역이었던 통신과 방송이 네트워크, 서비스, 단말기, 콘텐츠 차원에서 경계가 허물어지는 통신.방송 융합현상이 가속화되고 있다. 이에 따라 IPTV, DMB, 웹캐스팅, 데이터방송 등 기존의 통신과 방송의 속성을 모두 가진 서비스가 우리들의 실생활에 속속 등장하고 있다. 이러한 융합현상은 이용자에게는 새로운 융합서비스 이용을 통한 편익 증진뿐만 아니라 통신.방송 전반의 산업구조까지 근본적으로 변화시키고 국가 경쟁력을 높일 수 있는 좋은 기회가 될 것으로 보고 있다. 이미 세계 주요국은 IPTV서비스를 도입하고 있으나, 세계 최고의 정보통신 인프라를 보유하고 있는 우리나라는 안타깝게도 법제도 정비의 지연으로 아직 도입을 못하고 있다. 우리나라는 IPTV 도입뿐만 아니라, 디지털방송 활성화, 디지털콘텐츠 육성 등 풀어나가야 할 현안들이 산적해 있다. 또한 방송과 통신 전반에 걸쳐 정책과 규제체계를 융합환경에 맞추어 새롭게 설계해야 하는 과제도 있다. 이러한 과제를 순조롭게 해결하기 위해서는 우선적으로 정책과 규제기구를 융합환경에 맞게 개편하는 것이 시급하다. 이번호에서는 방송통신 융합의 주요 이슈 가운데 가장 시급하게 해결해야할 방송.통신 기구개편과 대표적인 방송통신융합서비스인 IPTV서비스 도입정책방안 그리고 방송통신융합법에 대해 전문가들의 특별기고를 통해 살펴보는 자리를 마련한다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.600-605
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• 2006

센서 네트워크는 데이터를 수집하는 싱크 주변에 있는 센서 노드가 극심한 에너지 소비를 보이는 문제가 있다. 이러한 싱크 주변 센서 노드의 에너지 소비 분산을 위해 모바일 싱크를 사용한 데이터 수집방법에 대한 연구가 최근 활발히 진행되고 있다. 모바일 싱크를 사용하여 데이터를 수집하기 위해서는 각 센서 노드별 데이터 수신 순서를 스케줄링하여 각 센서 노드에게 균등한 데이터 전송 기회를 부여하는 것이 중요하다. 본 논문에서는 싱글 홉 센서 네트워크에서 모바일 싱크를 이용한 균등한 데이터 수집을 위한 데이터 가중치 기반 스케줄링기법인 DWEDF를 제안한다. 또한 시뮬레이션을 통해 여러 다른 스케줄링 기법들에 비해 약 1.5배에서 3배가량 높은 성능을 보임으로써 그 효율성을 검증하였다.