• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.4
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• pp.415-425
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• 1997

Although FHSS has many advantages over conventional digital radio communication system, field application has been so far hampered due to its complicated synchronization. In this paper, a new FHSS system is proposed which one FH signal modulated with GMSK and one chip delayed FH signal than former are sent from transmitter, and this is recovered by matching process at a heterodyne correlator in receiver; thus eliminates synchronization as a whole. Through analysis and experiment, we assure that there is possibility in this. The exper- imental result from 915~929 MHz bandwidth with 31 chips is investigated in the environment of AWGN.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.1
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• pp.69-76
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• 2018

This paper studies the Turbo Codes, the concatenation of Turbo Codes and Reed-Solomon (RS) codes on Orthogonal frequency-division multiplexing (OFDM) in digital communication channel, and then analysis the performances of the new concatenated Forward Error Correct (FEC) scheme applied to an OFDM system based on the digital terrestrial video broadcasting (DVB-T) scheme. We compared the results with the standard DVB-T convolutional codes performances on Additive White Gaussian Noise (AWGN) channels. The simulation results shown that by employing turbo codes with only a few numbers of iterations, the performances of the overall system can be improved significantly. These results will be obtained by applying an appropriate interleaver technique in the concatenated FEC procedure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7C
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• pp.587-593
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• 2010

In this paper we design an irregular low-density parity-check (LDPC) code for multiple-input multiple-output (MIMO) system, using a simple extrinsic information transfer (EXIT) chart method. The MIMO systems considered are optimal maximum a posteriori probability (MAP) detector. The MIMO detector and the LDPC decoder exchange soft information and form a turbo iterative receiver. The EXIT charts are used to obtain the edge degree distribution of the irregular LDPC code which is optimized for the MIMO detector. It is shown that the performance of the designed LDPC code is better than that of conventional LDPC code which was optimized for either the Additive White Gaussian Noise (AWGN) channel or the MIMO channel.

• ETRI Journal
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• v.33 no.3
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• pp.310-319
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• 2011

In this paper, a new soft-fusion approach for multiple-receiver wireless communication systems is proposed. In the proposed approach, each individual receiver provides the central receiver with a confidence level rather than a binary decision. The confidence levels associated with the local receiver are modeled by means of soft-membership functions. The proposed approach can be applied to wireless digital communication systems, such as amplitude shift keying, frequency shift keying, phase shift keying, multi-carrier code division multiple access, and multiple inputs multiple outputs sensor networks. The performance of the proposed approach is evaluated and compared to the performance of the optimal diversity, majority voting, optimal partial decision, and selection diversity in case of binary noncoherent frequency shift keying on a Rayleigh faded additive white Gaussian noise channel. It is shown that the proposed approach achieves considerable performance improvement over optimal partial decision, majority voting, and selection diversity. It is also shown that the proposed approach achieves a performance comparable to the optimal diversity scheme.

• ETRI Journal
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• v.32 no.1
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• pp.11-21
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• 2010

A novel ultra-wideband (UWB) transceiver structure is presented to be used in wireless body area networks (WBANs). In the proposed structure, a data channel and a control channel are combined into a single transmission signal. In the signal, a modulation method mixing pulse position modulation and pulse amplitude modulation is proposed. A mathematical framework calculating the power spectrum density of the proposed pulse-based signal evaluates its coexistence with conventional radio systems. The transceiver structure is discussed, and the receiving performance is investigated in the additive white Gaussian noise channel. It is demonstrated that the proposed scheme is easier to match to the UWB emission mask than conventional UWB systems. The proposed scheme achieves the data rate requirement of WBAN; the logical control channel achieves better receiving performance than the logical data channel, which is useful for controlling and maintaining networks. The proposed scheme is also easy to implement.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.6
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• pp.1-8
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• 1994

In this paper, in order to apply the idea MDPSK to TCM, we use signal set expansion and set partition by phase differences. Through this we propose the trellis-coded MDPSK. And the Viterbi decoder containing branch metrics of the squared Euclidean distance of the Lth order phase difference as well as the first order phase difference is introduced in order to improve the bit error rate(BER) in the differential detection of the trellis-coded MDPSK. The proposed Viterbi decoder is conceptually same to the sliding multiple symbol dection method which uses the branch metric with the first and Lth order phase differences. We investigate the performance of the uncoded DQPSK and the trallis-coded D8PSK in additive white Gaussian noise (AWGN) through the Monte Carlo simulation under the two cases of using and not using the Lth order phase difference metric. The study shows that trellis-coded 8DPSK is an attractive scheme for power and bandlimited systems while also improving the BER performance when the Viterbi decoder is employed to the Lth order phase order difference metric. This performance improvement has been obtained without sacrificing the bandwidth or the power efficiency.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.6
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• pp.47-54
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• 2005

In this paper, we propose a method that search the sweet spot of antenna beam, and keep it for fast speed transmission in millimeter wave on point-to-point link. We use TDD(Time Division Duplex) as transfer method, and it transfers the control data of antenna. The proposed method is the modified genetic algorithm which selects a superior initial group through slave-processing in order to resolve the local solution of genetic algorithm. The efficiency of the proposed method is verified by means of simulations with white Gaussian noise and not on point-to-point link.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.478-481
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• 2000

In this paper, we propose a joint coding system for still images using source coding and powerful error correcting code schemes. Our system comprises an LVQ (lattice vector quantization) source coding for wavelet transformed images and turbo coding for channel coding. The parameters of the image encoder and channel encoder have been optimized for an n-D (dimension) cubic lattice (D$_{n}$, Z$_{n}$), parallel concatenation fur two simple RSC (recursive systematic convolutional code) and an interleaver. For decoding the received image in the case of the AWGN (additive white gaussian noise) channel, we used an iterative joint source-channel decoding algorithm for a SISO (soft-input soft-output) MAP (maximum a posteriori) module. The performance of transmission system has been evaluated in the PSNR, BER and iteration times. A very small degradation of the PSNR and an improvement in BER were compared to a system without joint source-channel decoding at the input of the receiver.ver.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.6
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• pp.711-717
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• 2014

Happiness has been studied in sociology and psychology as a matter of grave concern. In this paper the happiness model that a new second -order systems can be organized equivalently with a Spring-Damper-Mass are proposed. This model is organized a 2-dimensional model of identically type with Duffing equation. We added a nonlinear term to Duffing equation and also applied Gaussian white noise and period sine wave as external stimulus that is able to cause of happiness. Then we confirm that there are random motion, periodic motion and chaotic motion according to parameter variation in the new happiness model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.6
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• pp.568-580
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• 1997

In this paper we evaluate the performances of two types of 16-QAM system such as square QAM and star QAM. First we analyze the performances of QAM systems under AWGN(adaptive white Gaussian noise) and afterward analyze the performances under fading environments. The performances of QAM systems in case of using the PSAM(Pilot Symbol Assisted Modulation) are finally evaluated under fading environments. In conclusion, the Square QAM's performance is better than star QAM in AWGN. But the performances of the both QAM systems are very poor under the fading environments. QAM performance using the PSAM system is verified to be improved in that case, and the star QAM's performance is better than square QAM.