• The Journal of the Korea Contents Association
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• v.10 no.10
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• pp.19-25
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• 2010

While Snoop improves network performance by using local retransmission in case of packet loss in wireless network, it has security vulnerability to be unable to countermeasure against falsified ACKs attacks. Therefore in this paper, we suggest a modified Snoop with an extra buffer in addition to original Snoop buffer. Even though packets are exhausted in original buffer by falsified ACKs attacks, proposed Snoop can locally retransmit the packets saved in the extra buffer. The simulation by NS-2 shows that proposed Snoop countermeasure efficiently against falsified ACKs attack and builds securer Snoop protocol.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.578-585
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• 2001

IP Multicast that provides best-efforts service does not guarantee reliable delivery of multicast packets. In recent years, there are many approaches to support reliable multicast, but those are insufficient for implementing scalable and reliable multicast over Internet. We propose a Reliable Multicast Architecture(RMA) for scalable and reliable multicast. The RMA model guarantees reliability using a receiver initiated retransmission mechanism, and scalability using a feedback suppression mechanism by Multicast Router(MR). Furthermore, it utilizes underlying multicast routing information to minimize the cost of protocol modification and overheads. Our performance analyses show that RMA is much superior to previous works in the point of scalability and compatibility.

• Journal of Korea Multimedia Society
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• v.16 no.10
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• pp.1204-1213
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• 2013

With the development of digital satellite communication technology and the widespread use of smart devices, the demand for data communication in the maritime ship has increased. Recently, the communication between the maritime ship and the land is based on Inmarsat satellite service. The Inmarsat provides telephone, fax, data and telex service etc. However, since the satellite is payper-seconds billing service, the transmission of whole web contents to the maritime ship through the satellite causes high cost. In this paper, we propose web browsing system architecture that reduces the data traffic on the satellite link and retransmits the content selectively in order to solve these problems.

• Journal of Advanced Navigation Technology
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• v.15 no.3
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• pp.364-371
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• 2011

In P2P distribution mobile networks, QoS of streaming media services are under heavy influence from overheads such as congestion, latency, and interference. The problem is further complicated by the fact that the popularity of media objects changes over time. This paper proposes a new FSMS+ (Fuzzy Similarity-based Multi-level Streaming Scheme) which minimizes performance degradation of streaming services due to overhead. We then utilize fuzzy similarity-based relevance that can dynamically stream the streaming media object with minimum overhead. The simulation result showed that the proposed scheme has better performance in retransmission rate, congestion control rate and latency rate than the other existing methods of distance method, DC (disk caching) method, and prefix method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3B
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• pp.130-137
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• 2005

Wireless communication environment is changing rapidly as we use new wireless communication technology such as WiBro to access high speed Internet. As a result, reliable data transmission using TCP is also expected to increase. Since TCP assumes that it is used in wired network, TCP suffers significant performance degradation over wireless network where packet losses are related to non-congestion loss. Especially RTO imposes a great performance degradation of TCP. In this paper, we analyze the loss recovery probabilities based on previous researches, and use simulation results of our algorithm to show that it prevents performance degradation by quickly detecting and recovery losses without RTO during fast recovery.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.600-606
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• 2004

An interleaving delay diversity scheme is investigated in this paperand the applications in the multi-code WCDMA system along with antenna selection diversity is proposed. The proposed algorithm utilizes interleaving and delayed duplicated transmission mechanism to mitigate the effect of noise and fading. The interleaved signal and the original signal are both transmitted at intervals to obtain time diversity without any increase in required capacity. By adjusting the number of retransmissions of the information signal properly, the system achieve the receive diversity efficiently. For transmission power efficiency the proposed system also applies antenna selection diversity. By computer simulation, it has been shown that the proposed algorithm achieves better performance than the conventional algorithms by more than 2dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7B
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• pp.650-659
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• 2004

Domestic wireless network environment is changing rapidly while adapting to meet service requirements of users and growth of market. As a result, reliable data transmission using TCP is also expected to increase. Since TCP assumes that it is used in wired networt TCP suffers significant performance degradation over wireless network where packet losses are not always result of network congestion. Especially RTO imposes a great performance degradation of TCP. In this paper, we propose DAC$^{＋}$ and EFR in order to prevent performance degradation by quickly detecting and recovering loss without RTO during fast recovery. Compared with TCP NewReno, proposed scheme shows improvements in steady-state in terms of higher fast recovery Probability and reduced response time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9B
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• pp.813-822
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• 2003

Conventional TCPs are designed to work efficiently on wired network where any transmission errors rarely take place. However, the probability of transmission error in a wireless network is much higher than in a wired network, due to pass loss, multipath fading, and many kinds of interference. There were many researches on preventing the degradation of TCP performance in these wireless networks with bad channel condition. One of these researches is the SNOOP protocol which is link-layer solution for achieving high throughput of TCP. However, this SNOOP protocol is apt to retransmit some TCP segments unnecessarily, which could cause some increased traffic loads in a wireless network. In this paper, we propose a new algorithm to prevent the unnecessary retransmission of TCP segments and to achieve increased performance of TCP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.2
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• pp.171-181
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• 1988

In this study, a packet voice/data terminal(PVDT) that services both voice and data in the packet-switched network is implemented. The software structure of the PVDT is designed according to the OSI 7 layer architecture. The discrimination of voice and data is made in the link layer. Voice packets have priority over data packets in order to minimize the transmission delay, and are serviced by a simple protocol so that the overhead arising form the retransmission of packets may be minimized. The hardware structure of the PVDT is divided into five modules; a master control module, a speech proessing module, a speech activity detection module, a telephone interface module, and an input/output interface module. In addition to the hardware implementation, the optimal reconstruction delay of voice packets to reduce the influence of delay variance is analyzed.

• Journal of Communications and Networks
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• v.7 no.4
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• pp.489-498
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• 2005

For better performance over a noisy channel, mobile wireless networks transmit packets with forward error correction (FEC) code to recover corrupt bits without retransmission. The static determination of the FEC code size, however, degrades their performance since the evaluation of the underlying channel state is hardly accurate and even widely varied. Our measurements over a wireless sensor network, for example, show that the average bit error rate (BER) per second or per minute continuously changes from 0 up to $10^{-3}$. Under this environment, wireless networks waste their bandwidth since they can't deterministically select the appropriate size of FEC code matching to the fluctuating channel BER. This paper proposes an adaptive FEC technique called adaptive FEC code control (AFECCC), which dynamically tunes the amount of FEC code per packet based on the arrival of acknowl­edgement packets without any specific information such as signal to noise ratio (SNR) or BER from receivers. Our simulation experiments indicate that AFECCC performs better than any static FEC algorithm and some conventional dynamic hybrid FEC/ARQ algorithms when wireless channels are modeled with two-state Markov chain, chaotic map, and traces collected from real sensor networks. Finally, AFECCC implemented in sensor motes achieves better performance than any static FEC algorithm.