• Journal of Korea Society of Industrial Information Systems
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• v.25 no.5
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• pp.13-21
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• 2020

This paper proposes a sign reversal channel switching method in space-frequency block code for orthogonal frequency division multiplexing system. In case of sending source data on other antenna, it is necessary for the receiver to change combining method according to the channel variation. If one does not know the predefined channel switching sequence, it is not possible to decode the received data precisely. In transmit data symbols' exchanges for a channel switching, data symbols are exchanged according to a format of space-frequency block code. In this paper, we proposes a simple sign reversal method except exchanging data symbols between transmit antennas. It is shown that this method occurs another combining method for a simple encryption in the receiver.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.141-144
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• 2018

비디오 압축에서, 변환은 데이터를 공간 영역에서 주파수 영역으로 변환 함으로써 에너지 압축에서 중요한 역할을 수행한다. HEVC(High Efficiency Video Coding)에서는 DCT-II(Discrete Cosine Transform type-II)를 사용하여 잔차신호 변환을 수행한다. DCT-II는 픽셀간 상관도가 높은 신호일수록 높은 에너지 집중도를 보이지만, 픽셀간 상관도가 비교적 낮은 블록일수록 낮은 에너지 집중도를 보인다. 본 논문에서는 DST-VII(Discrete Sine Transform type-VII) 및 잔차신호 플리핑을 사용하여 다양한 변환 방법으로 영상을 부호화 및 복호화 하는 알고리즘에 대해 제안한다. 다양한 변환 방법은 부호화기에서 블록단위로 1 가지를 선택하여 비트스트림으로 선택된 방법에 대한 정보를 전송한다. 제안된 방법은 HEVC 대비 약 2.47%의 BD-rate 감소를 보인다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.4
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• pp.234-238
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• 2012

This paper proposes a multiplexed space-frequency block coding (SFBC) technique for single-carrier modulation with frequency domain equalization. Multiplexed space-frequency block coding technique for single-carrier modulation uses multiple groups of two transmitters and suppresses the interference signals of other SFBC groups at the receiver. In this paper, we reconfigure transmit signals to adapt them for multiplexed SFBC for single-carrier modulation with frequency domain equalization and receiver structures and propose a structure for transmitter and receiver, show its performance is better than the traditional algorithm by simulations.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.4
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• pp.316-320
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• 2016

This paper proposes an alternate time-switched multiplexed space-frequency block coding technique for single-carrier modulation with frequency domain equalization. The traditional multiplexed space-frequency block coding technique for single-carrier modulation uses multiple groups of two transmitters and suppresses the interference signals of other SFBC groups at the receiver. In this paper, we reconfigure transmit signals to adapt them for alternate time-switched multiplexed SFBC for single-carrier modulation with frequency domain equalization and receiver structures and propose a structure for transmitter and receiver, show that its performance is better than the traditional algorithm by simulations.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.1
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• pp.29-33
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• 2014

This paper proposes an alternate time-switched space-frequency block coding transmission technique for single-carrier modulation with frequency domain equalization. There are two antennas in the transmitter but it still has only a baseband and RF and a switch that alternates between the antennas at every symbol timing. Alternating transmit symbols result in zeros which make maximal ratio receive combining possible in the receiver. Simulation results show that it has better performance than the traditional algorithm at the expense of one additional antenna.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.1
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• pp.48-52
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• 2017

This paper proposes a hybrid algorithm of space-time block coding and space-frequency block coding using alternate time switch. The traditional alternate time-switched space-time or space-frequency block coding technique for orthogonal frequency division multiplexing system does not provide a good performance with a variety of communication environments. This hybrid algorithm has searched good performance ranges in various environments in view points of mobile speed and doppler frequency. In this paper, we investigate better performance ranges for two algorithms, suggest a hybrid algorithm for dynamically changing communication environments, propose a structure for transmitter and receiver, and show that its performance is better than the traditional algorithm by simulations.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.4
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• pp.8-15
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• 2009

Relay-assisted multi-input multi-output (MIMO) technique has become a promising candidate for next generation broadband wireless communications for high speed access. In this paper, we propose channel selective relay-based MIMO transmission system. The performance of relay-based system can be improved by using the subcarriers selectively based on the channel condition between relay and mobile station. Simulation results show that the proposed relay-based system considerably outperforms the conventional relay-based system.

• Journal of Korea Multimedia Society
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• v.14 no.5
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• pp.650-657
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• 2011

This paper proposes a novel bit allocation algorithm for H.264 scalable extension(SE) based on a human visual system (HVS) to improve the coding efficiency. The proposed algorithm is consist of two stages: visual weighting model and visual weighting-based bit allocation algorithm. In the first stage, the visual weighting for each macroblock (MB) is analyzed according to the region of interests. Then the adaptation of the visual weighting into the bit allocation routine for each quality layer is performed for improving the visual quality. In the simulation results, it is observed that the proposed scheme can improve the subjective and objective video quality in the same bit rate, compared to the previous scalable video coding in H.264.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.5
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• pp.1-9
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• 2009

Relay-assisted multiple input technique has become a promising candidate for next generation broadband wireless communications. In this paper, we propose channel selective relay-based multiple input transmission system. In the proposed system, single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA) are adopted for uplink and downlink transmissions, respectively. The performance of relay-based system can be improved by using the subcarriers selectively based on the channel condition between relay station (RS) and mobile station, or between RS and base station. Simulation results show that the proposed relay-based system considerably outperforms the conventional relay-based system.

• Journal of Broadcast Engineering
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• v.28 no.1
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• pp.100-108
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• 2023

In hybrid block-based video coding, transform coding converts spatial domain residual signals into frequency domain data and concentrates energy in a low frequency band to achieve a high compression efficiency in entropy coding. The state-of-the-art video coding standard, VVC(Versatile Video Coding), uses DCT-2(Discrete Cosine Transform type 2), DST-7(Discrete Sine Transform type 7), and DCT-8(Discrete Cosine Transform type 8) for primary transform. In this paper, considering that DCT-2, DST-7, and DCT-8 are all linear transformations, we propose an inverse transform that reduces the number of multiplications in the inverse transform by using the linearity of the linear transform. The proposed inverse transform method reduced encoding time and decoding time by an average 26%, 15% in AI and 4%, 10% in RA without the increase of bitrate compared to VTM-8.2.