• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.323-335
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• 1992

In this paper, an adaptive cosine transform coding scheme which incorporate human visual properties into the coding scheme is investigated. Human vision is relatively sensitive to mid-frequency band, and insensitive to very low and very high frequency band. These property was mathematically modelled with MTF(Modulation Transfer Function) through many psychovisual experiment. DCT transforms energy in spatial domain into frequency domain, so can exploit the MTF very efficiently. Another well-known visual characteristics is spatial masking effect that visibility of noise is less in regions of high activity than in regions of low activity. Proposed coding scheme imploys quantization matrix which represent the properties of these spatial frequency response of human vision, and adaptively quality of an image. To compute the activity index of an image block, simple operation is performed in spatial domain, and according to activity index. block of low activity region is more exactly quantized relatively than that of high activity region. Results showed that, at low bit rate, the subjective quality of the reconstructed images by proposed coding scheme is acceptible than that of coding scheme without HVS properties.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.999-1008
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• 2017

In this paper, we propose a pipeline network coding (PNC) scheme for efficient data transmission in wireless networks, a data authentication scheme for verifying the integrity of data, and a node authentication scheme for a virtual source. PNC is a technique that improves the overall network performance by relaying data such that the relay node performing network coding transmits to the sender instead. However, network coding is vulnerable to a pollution attack, which is an attack by a malicious attacker to inject modified data into the network. To prevent this, hash-based message authentication code (HMAC) is used. For this purpose, in order to generate a tag used for data authentication, a key must be distributed to the nodes performing authentication. We applied a hash chain to minimize the overhead of key distribution. A null vector is used as the authentication scheme for the virtual source. Finally, we analyze the safety and complexity of the proposed scheme and show he performance through simulation.

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.122-128
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• 2012

Because of the system delay caused by the number of feedback retransmission in Distributed Video Coding (DVC) scheme, it is difficult to realize practical DVC in many cases. In this paper low feedback retransmission Distributed Source Coding (DSC) scheme is proposed for practical DVC scheme based on Low-Density Parity-Check (LDPC) codes because DVC system is an specific application of DSC system. This DSC scheme is achieved by using different LDPC codes optimized in each different compression rate and using source revealing scheme. Optimized LDPC codes provide us much better decoding performance which causes the 57% reduced number of iteration. Consequently, the number of feedback retransmission is decreased by 50%.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.7
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• pp.71-79
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• 2004

Packet-type data transmission is characterized by the continuous transmission of massive data with relatively constant rate. In such transmission, the dynamic power consumed on buses is influenced by the sequence of transmitted data. A new coding scheme called Sequence-Switch Coding (SSC) is proposed in this paper. SSC reduces the number of bus transitions in the transmission of packet-type data by changing the sending order of the data. Some simple algorithms are presented, In. The simulation results show that SSC outperforms the well-known Bus-Invert Coding with these algorithms. SSC is not a specific algerian but a method to reduce the number of bus-transitions. There could be lots of algorithms for realizing SSC. The variety of SSC algorithms provides circuit designers a wide range of trade-off between performance and circuit complexity.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.1
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• pp.41-46
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• 2005

A new multiple description selective coding is proposed to overcome noisy channels. Our algorithm adopts an embedded coding scheme, in which subband coefficients are encoded one bit plane at a time using a non-adaptive arithmetic encoder. According to the importance ratio for each region, we code interest regions with more passes than background in order to reconstruct interest regions with higher quality. To overcome channel errors, we adopt multiple description scheme which adds controlled amounts of redundancy to the original data during the compression process. Proposed algorithm achieves better qualify compared with other algorithms especially in the circumstances where very low bit rate coding is required and some regions are more important than other regions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1420-1423
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• 2015

This letter considers a ship-to-ship communication system in which two ships exchange their information with the help of multiple relay ships. For the system, we propose a novel relay scheme that allows relay ships to select a method between analog network coding (ANC) and digital network coding (DNC) adaptively based on channel state information. We also provide a relay selection criterion in supporting the proposed adaptive network coding. The simulation results show that the proposed scheme outperforms the conventional scheme employing only the ANC or only the DNC.

• ETRI Journal
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• v.35 no.1
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• pp.173-176
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• 2013

Existing symmetric cryptography-based solutions against pollution attacks for network coding systems suffer various drawbacks, such as highly complicated key distribution and vulnerable security against collusion. This letter presents a novel homomorphic subspace message authentication code (MAC) scheme that can thwart pollution attacks in an efficient way. The basic idea is to exploit the combination of the symmetric cryptography and linear subspace properties of network coding. The proposed scheme can tolerate the compromise of up to r-1 intermediate nodes when r source keys are used. Compared to previous MAC solutions, less secret keys are needed for the source and only one secret key is distributed to each intermediate node.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.834-847
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• 1996

A selective coding scheme is proposed that describes a method for coding image sequences distinguishing bits between background and target region. The suggested method initially estimates global motion parameters and local motion vectors. Then segmentation is performed with a hierarchical clustering scheme and a quadtree algorithm in order to divide the processing image into the backgraound and target region. Finally image coding is done by assigning more bits to the target region and less bits to background so that the target region may be reconstructed with high quality. Simulations show that the suggested algorithm performs well especially in the circumstances where background changes and target regionis small enough compared with that of background.

• Journal of Broadcast Engineering
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• v.12 no.6
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• pp.624-629
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• 2007

While single view video coding uses the temporal prediction scheme, multi-view video coding (MVC) applies both temporal and inter-view prediction schemes. Thus, the key problem of MVC is how to reduce the inter-view redundancy efficiently, because various existing video coding schemes have already provided solutions to reduce the temporal correlation. In this paper, we propose a global disparity compensation scheme which increases the inter-view correlation and a new inter-view prediction structure based on the global disparity compensation. By experiment, we demonstrate that the proposed global disparity compensation scheme is less sensitive to change of the search range. In addition, the new Inter-view prediction structure achieved about $0.1{\sim}0.3dB$ quality improvement compared to the reference software.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.3
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• pp.129-137
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• 2007

MPEG-4 FGS is one of scalable video coding schemes specified In ISO/IEC 14496-2 Amendment 2, and particularly standardized as a scheme for providing fine granular quality and temporal scalabilities. In this paper, we propose a sign-bit reduction technique in embedded bit-plane coding to enhance the coding efficiency of MPEG-4 FGS system. The general structure of the FGS system for the proposed scheme is based on the standard MPEG-4 FGS system. The proposed FGS enhancement-layer encoder takes as input the difference between the original DCT coefficient and the decision level of the quantizer instead of the difference between the original DCT coefficient and its reconstruction level. By this approach, the sign information of the enhancement-layer DCT coefficients can be the same as that of the base-layer ones at the same frequency index in DCT domain. Thus, overhead bits required for coding a lot of sign information of the enhancement-layer DCT coefficients in embedded bit-plane coding can be removed from the generated bitstream. It is shown by simulations that the proposed FGS coding system provides better coding performance, compared to the MPEG-4 FGS system in terms of compression efficiency.