• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.735-748
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• 2014

The fault-tolerance routing problem is one of the most important issues in the application of the Internet of Things, and has been attracting growing research interests. In order to maintain the communication paths from source sensors to the macronodes, we present a hybrid routing scheme and model, in which alternate paths are created once the previous routing is broken. Then, we propose an improved efficient and intelligent fault-tolerance algorithm (IEIFTA) to provide the fast routing recovery and reconstruct the network topology for path failure in the Internet of Things. In the IEIFTA, mutation direction of the particle is determined by multi-swarm evolution equation, and its diversity is improved by the immune mechanism, which can improve the ability of global search and improve the converging rate of the algorithm. The simulation results indicate that the IEIFTA-based fault-tolerance algorithm outperforms the EARQ algorithm and the SPSOA algorithm due to its ability of fast routing recovery mechanism and prolonging the lifetime of the Internet of Things.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.75-78
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• 2004

In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the channel coding and space time code in downlink over ITU-R realistic channel model. We can improve the data rate and the reliability of communications by a channel code, and we can get a diversity gain by using the space time code over fading channels. We also apply the RAKE receiver to improve a performance in multi-path fading channel environment.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.3
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• pp.59-67
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• 2009

This paper proposes a improved bitmap routing protocol, which finds the best energy efficient routing path by minimizing the network overheads and prolongs the overall network lifetime. Jung proposed a bitmap scheme for sensor networks. His scheme uses a bitmap table to represent the connection information between nodes. However, it has a problem that the table size is depends on the number of nodes in the sensor networks. The problem is very serious in the sensor node with a limited memory. Thereby, this paper proposes a improved bitmap routing protocol to solve the problem in Jung's scheme. Proposed protocol over the memory restricted sensor network could optimize the size of bitmap table by applying the deployed network property. Proposed protocol could be used in the diversity of sensor networks due to it has minimum memory overheads.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1626-1631
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• 2004

OFDM are digital modulation techniques where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of OFDM systems with various antenna structure are analyzed, where data is transmitted over multi-path Rayleigh fading channel. The performance of this technique, gauged by the average bit error rate, is analyzed for the OFDM systems dependent upon the various antenna diversities.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1493-1496
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• 2003

본 논문에서는 하이브리드 SC/MRC 다이버시티 방식을 DS/CDMA 시스템에 적용하였을 경우, 다중경로 페이딩 채널환경에서 페이딩 지수와 다이버시티의 브랜치 수가 시스템의 BER성능에 미치는 영향을 MRC 다이버시티 방식과 비교 분석하였다. 또한, 브랜치 수는 2, 3, 4인 경우를 고려하였으며, 브랜치 수에 따른 각 다이버시티 방식을 적용하였다. 실제 통신 환경이 열악한 경우 시스템의 복잡도를 줄이면서도 비슷한 성능을 얻을 수 있는 방법으로 각 브랜치 수에 수신되는 강도가 센 몇몇 신호를 가진 경로를 선택하는 하이브리드 SC/MRC 다이버시티 방식이 MRC 다이버시티방식을 대신할 수 있는 방식임을 입증하였다.

• Journal of the Korea Society of Computer and Information
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• v.3 no.3
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• pp.121-127
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• 1998

In this paper, using diversity and convolution code in the DS/CDMA system, have been the performance analized. In this modulation shceme is using QPSK. Channel to CDMA system has been approximated by Rayleight fading channel considering effect for multi-path. In this assumed that receiver is WTDL(Wide-band Tappped Delay Line) receiver, and in this condition, average error probability of DS/CDMA.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1680-1684
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• 2010

CBTC(Communication-Based Train Control) system which is based on wireless communication can provide high density operation of the train using location tracking between ground and onboard train. It can also reduces maintenance expense because it does not require the ground equipment for tracking circuit and signal flag and so on. Recently, research and interest have been done on CBTC system. The high-speed trains up to 300km/h experience multi-path fading channel which bring about the performance degradation of wireless CBTC system. In this paper, we consider MIMO (Multi-Input Multi-Output) antenna-based CBTC system for trains with Alamoutip-type space-time diversity transmission for reliable communication. Also we model a channel considering practical environment and evaluate performance improvement of proposed CBTC system.

• Journal of Korea Multimedia Society
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• v.6 no.6
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• pp.1025-1033
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• 2003

The CDN is proposed as a solution of network bottleneck problem resulting from the rapid growth of Internet user and multimedia contents on the Internet. This paper suggests MDC and path diversity between CDN Edge server and end-user, and multicast transmission among CDN servers based on CDN infrastructure. It may be a solution for reliable and fast transmission of rich multimedia contents. These research will support to solve the unreliable transmission problem of multicasting and to create the new business models in the field of web contents.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.927-933
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• 2005

Multi carrier transmissions are digital modulation techniques where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With his technique, frequency diversity can be achieved. The performance of multi carrier transmission systems with various structure are analyzed, where data is transmitted over multi-path Rayleigh fading channel. The performance of this technique, gauged by the average bit error rate, is compared dependent upon the various structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.303-309
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• 2006

By combining the space-time diversity technique and iterative turbo codes, space-time turbo codes(STTCS) are able to provide powerful error correction capability. However, the multi-path transmission and iterative decoding structure of STTCS make the decoder very complex. In this paper, we propose a low complexity decoder, which can be used to decode STTCS as well as general iterative codes such as turbo codes. The efficient implementation of the backward recursion and the log-likelihood ratio(LLR) update in the proposed algorithm improves the computational efficiency. In addition, if we approximate the calculation of the joint LLR by using the approximate ratio(AR) algorithm, the computational complexity can be reduced even further. A complexity analysis and computer simulations over the Rayleigh fading channel show that the proposed algorithm necessitates less than 40% of the additions required by the conventional Max-Log-MAP algorithm, while providing the same overall performance.