• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.11C
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• pp.1033-1039
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• 2002

The coding scheme according to service types in AAL2 of ATM-PON is proposed in this paper. The service types and the corresponding error correcting codes are indicated by two of six reserved bits in SSTED of AAL2. Several coding schemes such as BCH and convolutional codes are considered under using the same and different kind of coding schemes. As a result, the (127,120) and (127,106) BCH codes may be the best choice for voice and data service respectively among all the possible schemes.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.87-88
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• 2007

In this paper, we propose a design of the layered coding with block turbo codes. The proposed scheme can be used efficiently for multimedia broadcasting and multicasting services by adaptive selection of a modulation and coding scheme at a receiver. This paper demonstrates various design examples of the layered coding using rate compatible block turbo codes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2372-2380
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• 2015

In this paper, we propose frequency allocation and path selection scheme in underlay cognitive radio (CR) networks using network coding. In the proposed scheme, we choose the path with consideration of network coding and interference temperature in underlay CR networks and propose an optimization problem to maximize the system throughput of secondary users (SUs). Then, we represent the proposed optimization problem as the multi-dimensional multiple-choice knapsack problem and give the theoretical upper bound for the system throughput of SUs by using linear programming. Finally, we compute the system throughput of SUs by using brute-force search (BFS) and link quality first (LQF) scheme in underlay CR networks. Simulation results show that the system throughput of SUs with BFS is higher than that with LQF in underlay CR networks with and without application of network coding, respectively.

• Journal of Communications and Networks
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• v.12 no.1
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• pp.11-18
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• 2010

Diversity-multiplexing tradeoff (DMT) is an efficient tool to measure the performance of multiple-input and multiple-output (MIMO) systems and cooperative systems. Recently, cooperative multicast system with wireless network coding stretched tremendous interesting due to that it can drastically enhance the throughput of the wireless networks. It is desirable to apply DMT to the performance analysis on the multicast system with wireless network coding. In this paper, DMT is performed at the three proposed wireless network coding protocols, i.e., non-regenerative network coding (NRNC), regenerative complex field network coding (RCNC) and regenerative Galois field network coding (RGNC). The DMT analysis shows that under the same system performance, i.e., the same diversity gain, all the three network coding protocols outperform the traditional transmission scheme without network coding in terms of multiplexing gain. Our DMT analysis also exhibits the trends of the three network coding protocols' performance when multiplexing gain is changing from the lower region to the higher region. Monte-Carlo simulations verify the prediction of DMT.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.5
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• pp.914-922
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• 1987

An image coding technique based on a segmentation, which utilizes a simplified description of regions composing an image, is investigated in this paper. The proposed coding technique consists of 3 stages: segmentation, contour coding. In this paper, emphasis was given to texture coding in order to improve a quality of an image. Split-and-merge method was employed for a segmentation. In the texture coding, a linear predictive coding(LPC), along with approximation technique based on a two-dimensional polynomial function was used to encode texture components. Depending on a size of region and a mean square error between an original and a reconstructed image, appropriate texture coding techniques were determined. A computer simulation on natural images indicates that an acceptable image quality at a compression ratio as high as 15-25 could be obtained. In comparison with a discrete cosine transform coding technique, which is the most typical coding technique in the first-generation coding, the proposed scheme leads to a better quality at compression ratio higher than 15-20.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.3
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• pp.303-310
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• 2013

Underwater acoustic communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes signal distortion and error floor. In order to improve the performance, it is necessary to employ an iterative coding scheme. Among the iterative coding scheme, turbo codes and LDPC codes are dominant channel coding schemes in recent. This paper concluded that turbo coding scheme is optimal for underwater communications system in aspect to performance, coded word length, and equalizer combining. Also, we confirmed the performance in the environment of oceanic experimentation using turbo equalizer based on distance 5Km, data rate 1Kbps.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.566-572
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• 2014

We propose a two-way multi-hop relaying scheme improving the throughput as well as enlarging the coverage for ship-to-ship communications in multi-ship marine networks. The proposed scheme reduces the time slots required for the data exchange by designing data transmission and network coding procedures in a sophisticated way based on two-phase digital network coding. Simulation results show that the proposed two-way multi-hop relaying scheme improves the throughput of the conventional one about 5/3 times.

• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.234-242
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• 2010

The demand on various broadcasting services has been greatly increasing in the area of mobile communication. In IEEE802.16e standard and mobile WiMAX, the multicast broadcast service (MBS) uses shared downlink channel for efficiently supporting a number of users. In this paper we propose a dynamic modulation and coding scheme with relay network to enhance the performance of MBS. The proposed approach employs the adaptive modulation and coding scheme for both the base station and relay station to achieve consistently high throughput. The result of computer simulation with NS-2 shows that the throughput and transmission time are significantly improved by using the proposed approach compared to the existing schemes having a fixed modulation level for the RSs.

• Journal of the Korea Society of Computer and Information
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• v.22 no.7
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• pp.101-108
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• 2017

A wireless image sensor node collecting image data for environmental monitoring or surveillance requires a large amount of energy to transmit the huge amount of video data. Even though solar energy can be used to overcome the energy constraint, since the collected energy is also limited, an efficient energy management scheme for transmitting a large amount of video data is needed. In this paper, we propose a method to reduce the number of blackout nodes and increase the amount of gathered data by selecting an appropriate video coding method according to the energy condition of the node in a solar-powered wireless video sensor network. This scheme allocates the amount of energy that can be used over time in order to seamlessly collect data regardless of night or day, and selects a high compression coding method when the allocated energy is large and a low compression coding when the quota is low. Thereby, it reduces the blackout of the relay node and increases the amount of data obtained at the sink node by allowing the data to be transmitted continuously. Also, if the energy is lower than operating normaly, the frame rate is adjusted to prevent the energy exhaustion of nodes. Simulation results show that the proposed scheme suppresses the energy exhaustion of the relay node and collects more data than other schemes.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.40-44
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• 2010

A layered coding scheme is one of the adaptive receiving techniques for unidirectional services such as multimedia broadcasting and multicasting services (MBMS), where we cannot utilize feedback information. The layered coding scheme can be used with hierarchical modulations by combining suitable code rates and modulation orders of each. In addition, it has been reported that hybrid and/or integrated satellite systems can effectively achieve transmit diversity gains by appropriate utilization of space time coding combined with turbo codes. This paper proposes a layered turbo coding schemes for hybrid and/or integrated satellite systems. We first introduce the system architecture and operational principle of the proposed scheme, and discuss the applicability.