• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.283-285
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• 2006

무선 센서 네트워크를 구성하는 센서 노드는 한번 배치되면 사람의 간섭 없이 오랜 기간 동안 동작하는 데 실행중인 소프트웨어를 수정 또는 추가를 할 필요가 있다. 그러나 센서 노드를 회수하기 어려운 경우가 있기 때문에 원격 코드 업데이트 기법이 필요하게 되고, 이를 위한 신뢰성 있는 코드 전송 프로토콜에 대한 연구가 활발하게 진행되고 있다. 하지만 신뢰성만을 고려한 코드 전송 프로토콜은 코드를 안정적으로 전송하기만을 고려하기 때문에 코드를 신속하게 전송한다는 관점에 대한 고려가 부족하다는 한계를 갖는다. 그 결과 긴 코드 전송시간에 의해 불필요한 에너지 소모를 발생함으로써 센서노드의 에너지 효율을 저하시키게 된다. 본 논문에서는 기존의 코드 전송 프로토콜들이 가지는 한계를 극복하는 FCPP(Fast code propagation protocol)을 제안하였다. FCPP는 신뢰성 있는 전송뿐만 아니라 신속함을 고려한 접근 방법을 제시하고 있다. 새로 제안한 알고리즘은 RTT기반의 전송률 조절과 NACK 억제 기법으로 네트워크 상태를 반영한 전송률 조절과 에러복구에 의한 불필요한 전송지연을 피하도록 하여 네트워크의 사용률을 최대화하여 신속한 코드 전송을 가능하게 한다. 또한 ns-2 시뮬레이터를 이용한 실험을 통해 제안한 FCPP가 센서 네트워크의 코드 전송에서 신뢰성 및 신속함을 모두 만족시킬 수 있음을 확인하였다.

• Journal of Advanced Navigation Technology
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• v.5 no.1
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• pp.11-18
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• 2001

In this paper, we evaluated the performance of Orthogonal MC/FH-CDMA system considering the hit of frequency hopping patterns, and obtained the degree of the performance improvement by adopting TCM scheme under frequency selective Rayleigh fading channel. From the performance analysis, it is known that the error performance is improved, since delay time relative to symbol time is reduced as the number of carrier is increased. On the other hand, it is found that BER performance is improved about $5{\times}10^{-2}$ degree by adopting TCM scheme, and higher S/N is required if the QoS of voice (BER = $10^{-3}$) must be achieved.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.110-118
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• 2013

This paper describes the development of DSSS wireless communication uplink system for missile remote control. In consideration of low probability of intercept, low probability of exploitation, anti-jam, low latency, and doppler frequency offset, we used DSSS partially DBPSK. Also we used the selective diversity with two receiving antennas to mitigate multipath interference which is the dominant channel impairment and the turbo product code(TPC) for forward error correction(FEC) to improve bit error rate performance.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.2
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• pp.71-78
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• 2008

The sensor node's performance is expected to be improved and the price will be largely decreased. As USN-applied field is expanded, multiple application services are expected to be provided through one USN soon. Multiple applications be required a periodic data reporting, consecutive information monitoring, event-driven data and query-based data as the data pattern that USN is delivered. Accordingly, the mechanism which can assure QoS according to each data characteristic is required. In this paper, A proposed protocol apply the duty cycle of S-MAC protocol variably and flexible according QoS level. This method largely reduces the delay on the delay-sensitive traffic, while keeping the energy efficiency.

• The Journal of the Korea Contents Association
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• v.8 no.2
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• pp.67-73
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• 2008

Recently, due to the rapid advances of mobile communication, multimedia service can be provided by mobile devices. Cellular network tends to uses SIP as a call setup protocol in order to provide various multimedia service to consumers. Cellular network holds the characteristic of higher BER(Bit Error Rate), narrower bandwidth than the wired network. The value of SIP RTI(Retransmission Time interval) based on the wired network decreases a network efficiency and increases a call setup delay over cellular network. By using NS-2 simulator, we show new SIP RTI value adequate over cellular network. We design and implement home network by using the modified SIP that is suitable for cellular network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2465-2473
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• 2012

Recently, as one of low complexity video encoding methods, DVC (Distributed Video Coding) scheme has been actively studied. Most of DVC schemes exploit feedback channel to achieve better coding performances, however, this causes these schemes to have high decoding delay. In order to overcome these, this paper proposes a new fast DVC decoding method using parity-bit request model, which can be obtained by using bit-error rate, sent by encoder with motion vector, which is transmitted through feedback channel by decoder after generating side information. Through several simulations, it is shown that the proposed method improves greatly the decoding speed, compared to the conventional schemes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.32-37
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• 2011

Underwater communication is affected by reverberation and noise characteristics of the underwater channel and time delay takes place by multipath. Hence, Signal is distorted and a lot of error is generated in the transmitting/receiving by multipath effects, so a channel coding for error correction is required. We propose a channel coding algorithm which is possible to correct error of received signal. We compare and analyze BER(bit error rate) performance depending on the depth of each transmitter-receiver using channel coding algorithm. QPSK was used as a modulation method, and 1/2 code rate convolution coding was used as a coding rate. A convolution coding method shows increase of BER performances.

• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2042-2049
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• 1999

In contrast to traditional data communication, the multimedia communication must support variable requirements to multimedia application service. Specially, it is a critical issue that the synchronization supports a continuous and temporal relationship media playout in a distributed environment. But the continuously generated media in source can't guarantee the constant interval on playout for the destination due to the inconsistent network transmission delay and transmission error. In this paper, we introduce a intramedia synchronization mechanism for the continuous and synchronous playout of multimedia stream such as audio and video across a communication network. The proposed mechanism is based on the user defined QoS(Quality of Service) and the playout correction algorithm to guarantee the continuous media playout at the receiver.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1671-1674
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• 2005

PCI 2.2 마스터 디바이스가 타겟 디바이스로부터 데이터를 읽어 오고자 할 때 타겟 장치는 내부적으로 데이터를 준비해야 함으로 인해 PCI 버스가 데이터 전송 없이 점유되는 상황이 발생한다. 이를 위해 PCI 2.2 사양에서는 지연전송을 제안하여 전송 효율을 향상시켰지만 이 역시 타겟 디바이스가 얼마의 데이터를 미리 준비 해둘지를 알 수 없어 인해 버스 사용 및 데이터 전송 효율을 떨어뜨리는 원인을 제공한다. 본 논문에서는 먼저 이를 해결하기 위한 새로운 방법을 제안한다. 그리고 이 방법을 지원하는 PCI 타겟 컨트롤러와 로컬 디바이스를 설계하였다. 설계되어진 PCI 타겟 컨트롤러는 PCI 2.2를 전혀 모르는 사용자도 쉽게 PCI 인터페이스를 지원할 수 있도록 한 프로토콜 변환기로 사용될 수 있다. PCI 타겟 컨트롤러와 로컬 디바이스는 먼저 행위 모델로 설계하였으며 또한 이들을 검증하기 위한 테스트벤치를 설계 하였다. 이를 통해 제안되어진 방법의 성능을 측정하였으며 후에 다시 실제 하드웨어로 설계하였다. 설계되어진 하드웨어를 효과적으로 검증하기 위해 참조모델, 랜덤발생기, 비교엔진으로 구성된 랜덤 테스트 환경을 제안하였다. 이 검증 환경에서 수행된 결과를 비교함으로써 일반적인 테스트 벡터에서 발견하기 어려운 에러들을 발견할 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11B
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• pp.981-988
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• 2008

In this paper, the efficient AODV routing algorithm in MANET is proposed. Because transmission channel has a high error rate and loss in MANET, the number of hops can't be regarded as an absolute network metric. After measuring FER periodically at the data link layer using cross-layer design, the scheme that every node forwards the weight of link status in the reserved field of AODV protocol is used. In order to find the efficient route, we design AODV to be able to select an optimal route that has a good channel status by evaluating the sum of weight. The proposed AODV improves throughput, routing overhead and average end-to-end delay in comparison with the generic AODV.