• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.12
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• pp.2813-2819
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• 2015

In this paper, we investigate the physical layer network coding (PNC) technique in a two-way relay channel (TWRC) where two source nodes send and receive data with each other via a relay node. In particular, we consider the communication scenario where packet length from the two sources is different from each other. We analyze the bit error rate (BER) of the received packet at the relay node according to degree of overlapping between two packets. The BER of the short packet remains unchanged regardless of the degree of overlapping since the entire packet is overlapped with the longer packet, while the BER of the longer packet becomes improved as the degree of overlapping decreases. Thus, we need a novel transmission scheme to enhance BER performance of the PNC technique in TWRC environments since the overall BER performance of the PNC technique at the relay node depends on the worse BER between two ovelapping packets' BERs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2131-2139
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• 2014

In this paper, a binary-coded physical-layer network coding (PNC) is considered when high-order modulation techniques are used at source nodes in wireless communication environments. In the conventional PNC schemes, tight power control and phase compensation are required at a relay node. However, they may not be feasible in practical wireless communication environments. Thus, we do not assume the pre-equalization in this paper, and we only utilize the channel state information at receiver (CSIR). We propose a signal detection method for the binary-coded PNC with high-order modulation, such as QPSK and 16QAM, at the source nodes, while the conventional scheme only consider the BPSK at source nodes. We also analyze the bit-error performance of the proposed technique in both uncoded and coded cases.

• Journal of Advanced Navigation Technology
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• v.11 no.4
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• pp.461-472
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• 2007

In Ubiquitous Sensor Network (USN), the sensor nodes are required to consume their energy evenly to prolong the lifetime of the entire sensor network because of the limited energy of the sensor node. AODV which is applied to USN as routing protocol selects route according to only the shortest distance of the minimum hop count but regardless of the remaining battery power for each node. Thus it comes to ill-balanced power consumption seriously. In this paper, a scheme that controls packet relay quantity of each sensor node adaptively to prevent traffic overhead at a certain node and to increase the entire network lifetime is proposed. As it is analyzed by simulations, the proposed scheme enhances USN lifetime by balancing each sensor node's packet relay quantity.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.4
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• pp.163-168
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• 2010

In this paper, we propose novel two-way relaying scheme in which number of two users transmit the signal to number of two destination. The scheme is difference with conventional multi-hop two-way relay scheme in which number of two users exchange the each signal. In the conventional scheme, each user have to perform back-propagating self-interference method to remove the own signal from received signal. It occurred to increase the complexity for signal processing at the user. To overcome the problem, we apply the Pre-cancellation which can reduce the process of back-propagating self-interference to our proposal network Simulation result show that proposal scheme outperform the convention multi-hop two-way relay scheme. Also we analysis the trad-off between performance and complexity accordance with using Pre-cancellation method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.99-101
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• 2014

불안정한 네트워크 환경 문제를 해결하기 위해 제안된 Delay Tolerant Network(DTN)에서는 안정적인 통신을 위해 저장 및 전달(store-carry-forward) 방식의 라우팅 프로토콜을 사용한다. 이중 노드의 속성 정보를 이용하여 추후 네트워크 상황을 예측하고 라우팅을 하는 예측 기반 라우팅 프로토콜은 GPS와 같은 위치 서비스의 발전으로 인해 DTN에 효과적으로 적용 될 수 있다. 이러한 예측 기반 라우팅 프로토콜에서는 중계 노드의 효율성이 네트워크의 상황에 따라 달라지기 때문에 위치 서비스를 통해 받는 노드의 속성 정보를 분석하는 연구가 제시되어야 한다. 본 논문은 노드의 속성 정보를 네트워크의 환경 정보에 따라 분석하여 효율적인 중계 노드를 선택하는 알고리즘을 제안한다. 제안하는 알고리즘은 노드의 속도, 방향, 위치 등의 속성 정보를 네트워크의 정보에 따라 가중치를 두어 다양한 네트워크 환경에서 더 효율적인 노드를 선택할 수 있도록 한다. 본 논문은 제안하는 알고리즘을 사용한 라우팅 프로토콜이 기존 라우팅 프로토콜에 비해 전송률, 지연시간, 오버헤드 측면에서 향상됨을 검증한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.571-573
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• 2018

Wireless sensor networks have unbalanced energy consumption due to the convergence structure in which data is concentrated to sink nodes. To solve this problem, in the previous research, the relay node was placed between the source node and the sink node to merge the data before being concentrated to the sink node. However, selecting a relay node that does not consider the link quality causes packet loss according to the link quality of the reconfigured routing path. Therefore, in this paper, we propose a link cost calculation method for data reliability in routing path reconfiguration for relay node selection. We propose a link cost estimation formula considering the number of hops and RSSI as the routing metric value and select the RSSI threshold value through the packet transmission experiment between the sensor modules.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1877_1878
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• 2009

본 논문에서는 간섭 제어 토폴로지 정보를 이용한 전송 전력 제어로 간섭을 최소화할 수 있는 교차형 계층 라우팅 기법을 제안한다. 제안된 프로토콜은 간섭 제어모델을 MAC 계층과 라우팅 계층들의 모듈에 통합한다. 그 모델은 송 수신 기반의 간섭모델로 데이터 송신과 수신에 관련된 간섭 정보를 통합된 MAC 계층과 라우팅 계층에서 중계 노드 선정 및 채널 경쟁을 위한 측정기준으로 활용된다. 또한 다양한 성능인자로 간섭을 회피할 수 있는 중계 노드 선정 전략은 종단간 전송 지연시간을 줄이며 각 수신노드 기반으로 예정되지 않은 노드의 라디오 모듈을 비활성 상태로 전환하도록 하여 에너지 소비를 줄이도록 설계된다.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06d
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• pp.297-300
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• 2010

비디오 데이터는 인코딩 단계의 특성상 패킷 드롭과 네트워크 딜레이에 무척 민감하다. 그렇기 때문에 레이트 컨트롤을 통해 대역폭이 변화하는 네트워크 환경에 대응 하고자 하는 연구가 진행 되어왔다. 하지만 컨텐츠 중심의 네트워크 환경에서는 소스 노드 뿐만 아니라 중계 노드들 또한 데이터를 전송함으로써 레이트 컨트롤을 위해 소스 노드에 접근 하는 것은 컨텐츠 중심의 네트워크의 장점을 상쇄 시킨다. 이 문제를 해결 하기 위해 계층별 비디오 컨텐츠 정보를 활용한 중계 노드 에서의 패킷 스케줄링 모델을 제안한다. 이로써 컨텐츠 중심의 네트워크에서의 사용자 네트워크 환경에 적응적으로 동작하는 효율적인 비디오 스트리밍이 가능하다.

• Journal of the Institute of Convergence Signal Processing
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• v.15 no.4
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• pp.155-161
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• 2014

In this paper, a cluster-based routing protocol in distributed sensor network is proposed, which enable the balanced energy consumption in the sensor nodes densely deployed in the sensor fields. This routing protocol is implemented based on clusters with hierarchical scheme. The clusters are formed by the closely located sensor nodes. A cluster node with maximum residual energy in the cluster, can be selected as cluster head node. In routing, one of the nodes in the intersection area between two clusters is selected as a relay-node and this method can extend the lifetime of all the sensor nodes in view of the balanced consumption of communication energy.

• The KIPS Transactions:PartC
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• v.15C no.5
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• pp.391-398
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• 2008

To provide IPTV service over mobile networks, the mechanism that reduce packet loss and interrupt of multimedia service during the handover should be supported. Especially, buffering based mechanism is preferable for supporting IPTV services in the way of preserving streaming service using stored data and recovering non-received data after handover. But previous research doesn't consider the buffer allocation for applying various environments which can change handover time or end to end delay of relay node. This paper propose DBAHAJ mechanism that optimize buffer size of mobile nodes and relay node for supporting seamless IPTV service over mobile environments. Mobile node determines buffer size by checking handover time and maximum difference of sequence to keep playing video data. And multicast agent recovers packet loss during the handover by sending buffered data. By these two procedure, node supports seamless IPTV service on mobile networks. We confirm performance of this mechanism on NS-2 simulator.