• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.669-676
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• 2008

The adaptive resource optimization problem in multi-input multi-output orthogonal frequency division multiple access (MIMO-OFDMA) systems is addressed. This paper, adaptive modulation and coding(AMC) and power control algorithms is proposed with SFC(Space-Frequency Coding), which aims to maximize the system capacity based on the CQI(Channel Quality Information). Firstly, power level is decided to each sub-channels with received feedback signal to noise ratio(SNR). In the second step, sub-carriers are allocated according to modulation type. Simulation results show that the proposed algorithm achieves a better performance than conventional algorithm in terms of capacity.

• Journal of Advanced Navigation Technology
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• v.5 no.2
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• pp.158-164
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• 2001

We presented a channel model for the inter vehicle radio link including the reflection from the road surface, side road vehicle and concrete wall. Then we theoretically derived the path loss and delay profile characteristics using the Ray tracing method efficiently analyzing millimeter wave or optic wave. Finally, we shown the improvement of propagation characteristics by diversity techniques, BCH coding and convolution coding techniques. At the result, MRC diversity techniques and BCH coding can't obtained PER = $10^{-6}$ which is considered to be data service criterion. But, we knew that Packet Error Rate Characteristic can obtained PER = $10^{-6}$, which is considered to be data service criterion, when convolution coding scheme are adopted in Rician fading.

• 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.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.4
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• pp.569-574
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• 2017

In order to transmit information in a channel environment in which noise exists, a coding technique of information is required. One of the coding techniques used for error detection and correction close to the Shannon limit is Low Density Parity Code(LDPC). LDPC and decoding characteristic features by Sum-product algorithm are matched for the performance to Turbo Code, RA(Repeat Accumulate) code, in case of very long code length of LDPC surpass their performance. This paper explains LDPC coding scheme of image data and decoding scheme, implements LDPC decoder in FPGA.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.147-151
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• 2010

In this paper, we propose network-coding based two-way relay communication using adaptive modulation scheme for satisfying relay QoS(Quality of Service) according to channel environment between user and relay. Two-way relay communication is bidirectional cooperative communication that users exchange own signal with help of relay. Network-coding based two-way relay communication can achieve high throughput compared to conventional scheme through reducing time slots. we propose adaptive M-QAM modulation scheme in network-coding based two-way relay communication for satisfying QoS of relay. Simulation result shows that the proposed scheme satisfies goal QoS of system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1229-1234
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• 2010

High quality and high speed multimedia services will be required in the next generation mobile communications. To satisfy these services, powerful error correction techniques are used. ARQ(Auto Repeat Request) techniques, aspects of the throughput, and FEC(Forward Error Correct) techniques have disadvantages in terms of reliability. H-ARQ(Hybrid Auto Repeat Request) systems have been studied extensively as a solution of these disadvantages. In this paper introduce double layer coding and H-ARQ type, proposed H-ARQ system using double layer coding methods. Simulate BER performance and throughput. And we suggest that according to channel condition suitable H-ARQ type.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.381-384
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• 2009

In the Wyner-Ziv coding, compression performance highly depends on the quality of the side information since better quality of side information brings less channel noise and less parity bit. However, as decoder generates side information without any knowledge of the current Wyner-Ziv frame, it doesn't have optimal criterion to decide which block is more advantageous to generate better side information. Hence, in general, fixed block size motion estimation (ME) is performed in generating side information. By the fixed block size ME, the best coding performance cannot be attained since some blocks are better to be motion estimated in different block sizes. Therefore if there is a way to find appropriate ME block of each block, the quality of the side information might be improved. In this paper, we investigate the effects of variable block sizes of ME in generating side information.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.8
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• pp.2003-2012
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• 1996

The 16- and 32-state Trellis-coded M-ary 4-dimensional (4-D) orthogonal modulation scheme with a frequency-reuse technique have been investigated. Here, 5 coded bits form a rate 4/5 convolutional encoder provide 32 possible symbols. Then the signals are mapped by a M-ary 4-D orthogonal modulator, where each signal has equal energy and is PSK modulated. In the M-ary 4-D modulator, we have employed the vectors which is derived by the optimization technique of signal waveforms in a 4-D sphere. This technique is usedin maximizing the minimum Euclidean distance between a set of signal poits on a multidimensional sphere. By combinig trellis coding with M-ary 4-D modulation and proper set-partitioning, we have obtained a considerable impeovement in the free minimum distance of the system over an AWGN channel. The 16-state scheme obtains coding gains up to 5.5 dB over the uncoded two-independent QPSK scheme and 2.5 dB over the two-independent 2-D TCM scheme. And, the 32-state scheme obtains coding gains up to 6.4 dB over the uncoded two-independent QPSK schemeand 3.4 dB over the two-independent 2-D TCM scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12A
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• pp.975-983
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• 2011

In this paper, we investigate how the IEEE 802.16 based wireless system can adopt the network coding. To avoid the problem of overhearing, we focus on the bidirectional traffic, where each end node exchanges network coded data over a relay node. The bidirectional traffic is usually observed in Internet, where TCP makes congestion control and error recovery based on the acknowledgement from the opposite direction. Thus, enhancing the spectral efficiency of wireless Internet through the network coding is expected. Our simulation with realistic radio characteristics and TCP-like traffic shows that the network coding improves the throughput by an average of 36 percent compared to the simple relay case.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.289-295
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• 1998

The purpose of this paper is to propose an improvement method of BER for coded 16-QAM under Rayleigh fading channel. To overcome the BER degradation due to the fading under mobile communication, we apply delay modulation technique which is efficient to get both a coding gain and approximately one-half those needed by Manchester coding on bandwidth requirements. Especially, the delay modulation scheme is insensitive to the $180^{\circ}$phase ambiquity common to NRZ-L and Manchester coding schemes. From the computer simulation, BER performance of our scheme has achieved about 3.8 dB improvement of about $10^{-4}$, compared to Manchester coded 16-QAM.