• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.27-35
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• 2012

In this paper, we look into a Jong Nang Channel which is the origin of digital communications and has been used in Jeju Island since AD 1234. It is one kind of communication ways which informs people of whether a house owner is in one's house or not using its own protocol. It is comprised of three timber and two stone pillars whose one side has three holes respectively. In this paper, we analyze the Jong-Nang Channel both in the light of logic and bit error probability. In addition, we compare it with a conventional binary erasure channel when some errors occur over them respectively. We also show that a capacity of NOR channel approaches Shannon limit.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.681-684
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• 2011

최근 IEEE 802.11 WLAN(Wireless Local Area Network)에서 실시간 멀티미디어 서비스가 증가하고 있다. WLAN 의 패킷 전송방식은 Unicast 또는 Broadcast 방식이 있다. Unicast 방식은 재전송을 포함하여 유실율이 적으나 사용자가 증가할수록 AP 에서 필요한 무선 자원의 크기가 증가한다. 무선 자원의 크기가 증가하면 AP 부하가 증가하여 서비스 수용에 한계가 있다. Broadcast 방식은 사용자 수에 상관 없이 무선 자원의 크기가 일정하나, 패킷 유실율이 높다. 본 논문에서는 이러한 문제점을 해결하기 위해 Broadcast 와 FEC(Forward Error Correction) Erasure Code 기반 기술을 적용하는 것을 제안한다. 방송 패킷을 이용 AP 의 부하를 줄이고, Reed Solomon Erasure Code 를 적용하여 패킷 유실 복구율을 높인다. 이러한 방법을 통하여 다수의 사용자에게 안정적인 실시간 멀티미디어 방송 서비스를 제공 할 수 있다. 제안한 방법을 검증하기 위해 Android Platform 에서 FEC 적용 유무에 따른 수신율을 측정하였다. 그 결과 유실율 30%미만인 Broadcast 환경에서 96.4% 이상의 수신율을 보였다.

• ETRI Journal
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• v.38 no.4
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• pp.612-621
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• 2016

A new time-domain decoder for Reed-Solomon (RS) codes is proposed. Because this decoder can correct both errors and erasures without computing the erasure locator, errata locator, or errata evaluator polynomials, the computational complexity can be substantially reduced. Herein, to demonstrate this benefit, complexity comparisons between the proposed decoder and the Truong-Jeng-Hung and Lin-Costello decoders are presented. These comparisons show that the proposed decoder consistently has lower computational requirements when correcting all combinations of ${\nu}$ errors and ${\mu}$ erasures than both of the related decoders under the condition of $2{\nu}+{\mu}{\leq}d_{\min}-1$, where $d_{min}$ denotes the minimum distance of the RS code. Finally, the (255, 223) and (63, 39) RS codes are used as examples for complexity comparisons under the upper bounded condition of min $2{\nu}+{\mu}=d_{\min}-1$. To decode the two RS codes, the new decoder can save about 40% additions and multiplications when min ${\mu}=d_{min}-1$ as compared with the two related decoders. Furthermore, it can also save 50% of the required inverses for min $0{\leq}{\mu}{\leq}d_{\min}-1$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9C
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• pp.877-886
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• 2005

Various frame recovery algorithms have been suggested to overcome the communication quality degradation problem due to Internet-typical impairments on Voice over IP(VoIP) communications. In this paper, we propose a new receiver-based recovery method which is able to enhance recovered speech quality with almost free computational cost and without an additional increment of delay and bandwidth consumption. Most conventional recovery algorithms try to recover the lost or erroneous speech frames by reconstructing missing coefficients or speech signal during speech decoding process. Thus they eventually need to modify the decoder software. The proposed frame recovery algorithm tries to reconstruct the missing frame itself, and does not require the computational burden of modifying the decoder. In the proposed scheme, the Vector Quantization(VQ) codebook indices of the erased frame are directly estimated by referring the pre-computed VQ Codebook Index Interpolation Tables(VCIIT) using the VQ indices from the adjacent(previous and next) frames. We applied the proposed scheme to the ITU-T G.723.1 speech coder and found that it improved reconstructed speech quality and outperforms conventional G.723.1 loss recovery algorithm. Moreover, the suggested simple scheme can be easily applicable to practical VoIP systems because it requires a very small amount of additional computational cost and memory space.

• Journal of Communications and Networks
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• v.17 no.6
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• pp.582-591
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• 2015

A massive distributed storage system is the foundation for big data operations. Access latency performance is a key metric in distributed storage systems since it greatly impacts user experience while existing codes mainly focus on improving performance such as storage overhead and repair cost. By generating parity nodes from parity nodes, in this paper we design new XOR-based erasure codes hierarchical tree structure code (HTSC) and high failure tolerant HTSC (FH HTSC) to reduce access latency in distributed storage systems. By comparing with other popular and representative codes, we show that, under the same repair cost, HTSC and FH HTSC codes can reduce access latency while maintaining favorable performance in other metrics. In particular, under the same repair cost, FH HTSC can achieve lower access latency, higher or equal failure tolerance and lower computation cost compared with the representative codes while enjoying similar storage overhead. Accordingly, FH HTSC is a superior choice for applications requiring low access latency and outstanding failure tolerance capability at the same time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2227-2234
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• 2009

DVB-SSP is a new broadcasting system for hybrid satellite communications, which supports mobile handheld systems and fixed terrestrial systems. An upper layer, including erasure Reed-Solomon error correction combined with cyclic redundancy check. However, a critical factor must be considered in upper layer decoding. If there is only one bit error in an IP packet, the entire IP packet is considered as unreliable bytes, even if it contains correct bytes. If, for example, there is one real byte error, in an IP packet of 512 bytes, 511 correct bytes are erased from the frame. Therefore, this paper proposed upper layer decoding methods; LLR-based decoding. By means of simulation we show that the performance of the proposed decoding algorithm is superior to that of the conventional one.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.3-8
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• 2012

Two-dimensional product code has been studied for correcting burst errors on the storage systems. An RS-LDPC product code consists of an RS code in horizontal direction and an LDPC code in vertical direction. First, we detect the position of burst errors by using RS code, then LDPC code corrects the errors by using the burst error positions. In storage system, long burst errors are occurred by various reason. So, we need a strong code for correcting the long burst errors. RS-LDPC product code is good for long burst errors. However, as the storage density grows the length of the burst errors will be longer. Thus, we propose an LDPC-LDPC product code, it is strong for correcting the very long burst errors. Also, the proposed LDPC-LDPC product code performs better than RS-LDPC product code when the random errors are occurred, because a row direction LDPC code performs better than row direction RS code.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9C
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• pp.848-854
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• 2009

DVB-SSP is a new broadcasting system for hybrid satellite communications, which supports mobile handhold systems and fixed terrestrial systems. An upper layer, including erasure Reed-Solomon error correction combined with cyclic redundancy check. However, a critical factor must be considered in upper layer decoding. If there is only one bit error in an IP packet, the entire IP packet is considered as unreliable bytes, even if it contains correct bytes. If, for example, there is one real byte error, in an If packet of 512 bytes, 511 correct bytes are erased from the frame. Therefore, this paper proposed upper layer decoding methods; hybrid decoding. By means of simulation we show that the performance of the proposed decoding algorithm is superior to that of the conventional one in AWGN channel and TI channel.

• Journal of Korea Multimedia Society
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• v.17 no.8
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• pp.961-967
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• 2014

Raptor codes are a class of rateless codes originally designed for binary erasure channels. This paper presents a compact set of mathematical expressions for iterative soft decoding of raptor codes. In addition, an early termination scheme is employed, and it is embedded in a single algorithm with the formula. In the proposed algorithm, the performance is enhanced by adopting iterative decoding, both in each inner and outer code and in the concatenated code itself between the inner and outer codes. At the same time, the complexity is reduced by applying an efficient early termination scheme. Simulation results show that our proposed method can achieve better performance with reduced decoding complexity compared to the conventional schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.3
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• pp.1193-1209
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• 2015

Network coding is promising to maximize network throughput and improve the resilience to random network failures in various networking systems. In this paper, the problem of providing efficient confidentiality for practical network coding system against a global eavesdropper (with full eavesdropping capabilities to the network) is considered. By exploiting a novel combination between the construction technique of systematic Maximum Distance Separable (MDS) erasure coding and traditional cryptographic approach, two efficient schemes are proposed that can achieve the maximum possible rate and minimum encryption overhead respectively on top of any communication network or underlying linear network code. Every generation is first subjected to an encoding by a particular matrix generated by two (or three) Vandermonde matrices, and then parts of coded vectors (or secret symbols) are encrypted before transmitting. The proposed schemes are characterized by tunable and measurable degrees of security and also shown to be of low overhead in computation and bandwidth.