• 한국산학기술학회논문지
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• 제11권5호
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• pp.1646-1652
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• 2010

무선 센서 네트워크에서의 통신은 여러 계층으로 나뉘어 각 계층별 역할을 수행하므로 무선통신이 가능할 수 있다. 센서 네트워크에서의 통신계층 중 하나인 MAC(Medium Access Control)계층은 데이터의 에러, 흐름을 제어하고 자원을 관리하기 위해서 사용되며 MAC Protocol을 사용하여 센서 노드간의 통신을 보장한다. 본 논문에서는 에너지 효율성 측면을 강조한 S-MAC. T-MAC 프로토콜의 문제점을 알아보고 SYNC 패킷에 RTS 패킷이 추가된 기법을 이용하여 컨트롤 패킷 전송 시간동안 꼭 필요한 노드만 컨트롤 패킷을 송수신하고, 나머지 노드들은 Sleep 함으로써, 모든 노드가 깨어있는 시간을 효율적으로 줄여 에너지 효율성을 강조하였다. SYNC+RTS 패킷을 보내고 패킷을 받는 노드는 순간 자신이 이번 주기 동안 깨어 있을 필요가 없음을 알고 바로 Sleep모드로 들어가서 기존의 MAC프로토콜보다 에너지가 효율적임을 수학적으로 증명하고 MATLAB으로 시뮬레이션 하였다.

• Journal of Communications and Networks
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• 제10권2호
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• pp.148-155
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• 2008

In wireless data communication systems, retransmission of an erroneous packet is inevitable due to the harsh communication environment. In this paper, an efficient retransmission scheme using cooperation from neighboring nodes is investigated. In the cooperative retransmission scheme, an erroneous packet is transmitted to the destination by cooperative nodes which have favorable channels. This cooperative retransmission scheme requires no a priori information of neighboring nodes and has no limitation on the number of cooperating nodes. Distributed beamforming is used to accommodate multiple cooperating nodes. Phase and frequency offsets of cooperating signals are extracted from the NACK message and used to co-phase retransmitted data packets. The outage probability of the cooperative retransmission scheme is analyzed for the case of perfect synchronization and when the offsets are estimated. To reduce the impact of the residual phase and frequency offsets in cooperating signals, a low-rate feedback scheme is also investigated. It is shown that improved outage probability and reduced packet error rate (PER) performance can be achieved even for long data packets. The proposed cooperative retransmission scheme is found to outperform simple retransmission by the source as well as decode-and-forward cooperation.

• Journal of information and communication convergence engineering
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• 제4권2호
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• pp.71-74
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• 2006

A basic access method about IEEE 802.11 MAC layer protocol using IEEE 802.11 wireless LANs is the DCF thatis based on the CSMA/CA. But, cause of IEEE 802.11 MAC layer uses original backoff algorithm (exponential backoff method), when collision occurred, the size of contention windows increases the double size Also, a time of packet transmission delay increases and efficienty is decreased by original backoff scheme. In this paper, we have analyzed TCP packet transmission time of IEEE 802.11 MAC DCF protocol for wireless LANs a proposed enhanced backoff algorithm. It is considered the transmission time of transmission control protocol (TCP) packet on the orthogonal frequency division multiplexing (OFDM) in additive white gaussian noise (A WGN) and Rician fading channel. From the results, a proposed enhanced backoff algorithm produces a better performance improvement than an original backoff in wireless LAN environment. Also, in OFDM/quadrature phase shift keying channel (QPSK), we can achieve that the transmission time in wireless channel decreases as the TCP packet size increases and based on the data collected, we can infer the correlation between packet size and the transmission time, allowing for an inference of the optimal packet size in the TCP layer.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.2946-2962
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• 2017

An improved energy-efficient compressed network coding method is proposed for the data communication in the wireless sensor networks (WSNs). In the method, the compressed sensing and network coding are jointly used to improve the energy efficiency, and the two-hop neighbor information is employed to choose the next hop to further reduce the number of the transmissions. Moreover, a new packet format is designed to facilitate the intermediate node selection. To theoretically verify the efficiency of the proposed method, the expressions for the number of the transmissions and receptions are derived. Simulation results show that, the proposed method has higher energy efficiency compared with the available schemes, and it only requires a few packets to reconstruct measurements with reasonable quality.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1298-1310
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• 2019

Network coding (NC) is a promising technology that can improve available bandwidth and packet throughput in wireless sensor networks (WSNs). Sliding window is an improved technology of NC, which is a supplement of TCP/IP technology and can improve data throughput and network lifetime on WSNs. This paper proposes a network coding-based maximum lifetime algorithm for sliding window in WSNs (NC-MLSW) which improves the throughput and network lifetime in WSN. The packets on the source node are sent on the WSNs. The intermediate node encodes the received original packet and forwards the newly encoded packet to the next node. Finally, the destination node decodes the received encoded data packet and recovers the original packet. The performance of the NC-MLSW algorithm is studied using NS2 simulation software and the network packet throughput, network lifetime and data packet loss rate were evaluated. The simulations experiment results show that the NC-MLSW algorithm can obviously improve the network packet throughput and network lifetime.

• 한국항행학회논문지
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• 제6권1호
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• pp.69-76
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• 2002

이동 단말기에 의한 데이터 통신 서비스가 증가함에 따라, 높은 에러율과 이동성을 가진 무선 환경에서 사용자의 요구에 의한 인터넷 컨텐츠의 접속이 효율적으로 이루어지기 위해 WAP 이라는 프로토콜이 제안되었다. 그러나, 현재 WAP의 전송 속도가 제한되어 있기 때문에, 데이터를 송수신하는 데는 많은 시간이 소요된다. 본 논문은 WTP-SAR(Wireless Transaction Protocol-Segment And Re-assembly) 알고리즘을 사용하여 WAP 패킷의 전송 시간을 분석하였다. 이러한 WAP의 전송 능력을 향상시키기 위한 한 방법으로 WTP에서 SAR 기능을 사용하여 상위 계층에서 내려온 전체 메시지를 분할하고, RLP(Radio Link Protocol) 타임 슬롯에서 패킷을 전송한다. 그리고 차세대 시스템을 위한 무선 CDMA 망에서 다양한 RLP 계층의 크기를 고려한 WAP 패킷의 전송 시간을 분석한다. 결과로부터 WAP 패킷의 전송 시간과 이에 따른 효율적인 WAP 패킷의 크기를 얻을 수 있었다.

• 전기학회논문지
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• 제57권11호
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• pp.2124-2126
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• 2008

In the wireless communication systems, the demand of multimedia services is also increased. Unlike typical data packets, realtime service such as VoIP packets have delay bound and low loss rate requirement. In this paper we propose a new scheduling algorithm that be able to allocate resources to the different kinds of services such as VoIP and data packet. The proposed algorithm considers both time delay and channel condition toe determine the priority. Simulation results show that the proposed algorithm works more efficiently than the conventional algorithms.

• 센서학회지
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• 제19권4호
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• pp.297-305
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• 2010

A home healthcare system based wireless sensor network, which can continuously monitor and manage the elderly's electrocardiogram(ECG) signal at any space at home without space limit is proposed. The communication coverage of wireless network is expended by multi-hop wireless sensor network. In order to send the elderly's ECG data wirelessly, a small size ECG sensor node was designed to forward the ECG data over multi-hop relay network. The packet acquired by mobile ECG node is transmitted through wireless intermediate nodes to base station for analyzing the packet reception rate. Modified minimum cost forwarding(MMCF) protocol and flooding protocol are designed and implemented to check the transmission efficiency of a packet in a wireless sensor network. The developed MMCF protocol shows an advantage of high reception rate by reduced network traffic.

• 한국인터넷방송통신학회논문지
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• 제13권1호
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• pp.109-114
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• 2013

수중 무선 센서 네트워크에서 센싱 데이터는 수온과 염도 등 평균 계산 등을 사용하여 병합이 가능한 경우가 많다. 데이터 병합은 수중 무선 센서 네트워크에서 패킷의 수를 줄이고 에너지를 절약하는 데 큰 도움이 된다. 하지만 데이터 병합으로 인해 지연이 발생할 수 있고, 불필요하게 긴 경로나 싱크 방향이 아닌 경로를 통해 패킷이 전달되는 단점이 있다. 본 논문에서는 이런 문제를 완화할 수 있는 데이터 병합 기반의 새로운 경로 결정 알고리즘을 제안한다. 제안 논문은 간섭 없이 지연을 줄이고 싱크 방향이 아닌 경로를 제거하여 에너지 효율성을 최대화 한다. 실험 결과를 통해 제안 알고리즘이 에너지 효율과 패킷 지연 면에 있어 우수함을 알 수 있다.

• Journal of information and communication convergence engineering
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• 제8권2호
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• pp.168-172
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• 2010

The Network-based handover still has problems such as the transmission delays and the packet losses in the case of macro mobility, though technological advances have been made in the wireless and mobile communication. For end-to-end handover, the link bandwidth has been reduced in the wireless network due to its burst errors and congestion control. To overcome such problems, we propose a new scheme of the macro handover according to the protocol layer. The proposed macro handover is implemented on the network layer to partially substitute wired signaling for wireless signaling, to flexibly employ buffers, and on the transport layer to postpone its retransmission time. We have performed extensive simulation using ns-2 and the result shows that our proposed scheme outperforms the other existing schemes in terms of transmission delay, packet loss, and data transfer rate during the handovers.