• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.543-546
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• 2005

In this paper, it was estimated the BER performance of the individual system type by applying the SFH type and the FFH type to the FH MC-DS CDMA system that combined the strong points of MC DS/CDMA and that of Frequency Hopping under the Nakagami fading channel with Multi-tone Jamming. An increase in the number of hoppings means that it can improve the BER performance by reducing the receiving burden of the FH MC DS/CDMA by achieving a frequency diversity effect. Therefore, I verified that the performances of the FH MC DS/CDMA system could be improved by increasing the number of hoppings.

• ETRI Journal
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• v.36 no.5
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• pp.799-807
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• 2014

In this paper, we design a rake-based cellular radar receiver (CRR) scheme to detect a moving target located in a multipath environment. The modules of Doppler filter banks, threshold level test, and target detection module are newly introduced into the conventional rake receiver so that it can function as a radar system. The proposed CRR tests the Doppler-shift frequency and signal-to-noise ratio of the received signal against predefined threshold levels to determine detection and then calculates target velocities and ranges. The system performance is evaluated in terms of detection probability and the maximum detection range under a Nakagami-n channel that reflects the multipath environment.

• ETRI Journal
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• v.21 no.2
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• pp.9-21
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• 1999

In this paper, to enhance the performance of ${\pi}$/4-DQPSK (${\pi}$/4-differential quadrature phase shift keying), the scheme using nonredundant multiple error correction is proposed and investigated. This scheme for the differential detection of ${\pi}$/4-DQPSK uses the signal output which is delayed for more than two time slots as the parity check bit and applies it to nonredundant multiple error correction. The proposed system was used for studying the performance of ${\pi}$/4-DQPSK with Nonredundant Error Correction (NEC) in additive white Gaussian noise (AWGN) and Nakagami fade modeled mobile communication channel, and it was observed that the performance increased as the error correction capability increased.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.457-460
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• 2000

The effect of code selection for a multicode DS/CDMA system is evaluated for a high deta rate transmission, The performance is evaluated in terms of bit error and outage probabilities. The multipath fading channel is modeled as a Nakagami-m distribution which has been known to be appropriate to model the multipath fading in urban as well as indoor channels. From simulation results, it is shown that the concatenated sequence of Walsh code and Gold sequence is most promising among many code selections. The considerations in this paper can be applied to the next-generation mobile communication systems such as IMT-2000 which requires high bit rate transmissions.

• Journal of Digital Contents Society
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• v.7 no.4
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• pp.251-256
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• 2006

In this paper, We proposed joint-modulation CDMA system for efficient streaming transmission. and, We analyzed joint-modulation CDMA system using nakagami fading model and impulsive interference model for transmission channel environment. Also, it can being compensate the performance degradation by using MRC diversity scheme and BCH coding scheme.

• Journal of Multimedia Information System
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• v.5 no.3
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• pp.155-162
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• 2018

Nowadays, the tracking technology of Quadrant Detector will become actual by new micro devices. Based on the past filed data of the reception experiment with COMETS satellite, we have studied on new device (AD8302, phase difference detector) was acquired and suspect its abilities. In 1998, we have developed a Quadrant Detector for mobile to track a weak signal from satellite on Ka band of COMETS. The Quadrant Detector is comprised of four dedicated feed components for reception under an environment of Nakagami - Rician fading, and one transmission and reception feed component. We were successful in receiving a 23 GHz beacon signal from ICE transponder of the COMETS and succeeded in tracking the satellite from a moving vehicle at speeds of approximately 10 ~ 20 Km/h on paved roads. In 2018, with new device AD8302, we have verified new QD system and performed a simulation, based on the past filed experiment. This new device shall be improving the tracking abilities from mobile body on the earth to the multimedia satellite.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1316-1319
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• 2002

In this paper, an online SNR estimator is derived for turbo coded multicode DS/SS systems in Nakagami fading channels. The multicode DS/SS approach is one of promising solutions to obtain higher-rate data transmission in DS/SS technologies. Turbo coding has paid much attention because of the significant improvements on error rate performances in various communication systems including multicode DS/SS systems. However, in the turbo decoding, channel state information, especially signal-to-noise ratio (SNR) at the correlator outputs, is desired in order to obtain such improvements. We evaluate the accuracy of the derived SNR estimation. It is shown that the bit error rate performance using our SNR estimation is close to the performance with perfect knowledge of channel state information.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.311-315
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• 2000

본 논문에서는 임펄스 잡음과 나카가미 페이딩 채널에서 블록 에러 NFSK 시스템을 제안하고, 이의 성능을 구하였다. 블록 에러 확률을 구하는데 있어서 나카가미 채널 페이딩 속도(즉, slow fading, fast fading)를 고려하여 임펄스 잡음지수의 변화에 따른 성능을 구하였다. 블록 에러의 성능을 개선시키는 방안으로 다이버시티 기법과 에러정정 부호화 기법을 적용하여 다이버시티 수(L), 에러정정능력(M), 임펄스 잡음지수(A)를 함수로 하여 성능 개선이 커지고, 저속 페이딩 (임펄스 잡음지수 A=0.1, 1에서 3dB 개선)보다 고속 페이딩에서 (임펄스 잡음지수 A=0.1, 1에서 2～4dB 개선)의 성능개선 정도가 우수하였다. MRC 다이버시티 기법은 저속 페이딩에서 부호화 기법을 적용했을 때 보다 우수한 성능을 보이고 페이딩의 영향이 클 때 성능개선이 크게 이루어짐을 알 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.727-731
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• 2001

된 논문에서는 임펄스 잡음과 다중접속간섭(MUI) 및 나카가미 페이딩 환경으로 모델링되는 FH/CDMA 시스템을 제안하고 이의 성능을 분석하였다. 결과에 의하면 FH-CDMA 시스템은 잡음이나 페이딩의 영향보다는 여러명의 사용자가 같은 시간에 같은 주파수를 사용함으로 인한 충돌과 임펄스 잡음에 의해 더 큰 영향을 받는다. 성능 개선기법으로 다이버시티 기법과 에러정정 부호화 기법을 사용함으로써 페이딩과 다중접속 간섭에 대하여 어느 정도의 개선효과를 보이지만 임펄스 잡음의 영향으로 무선 데이터 통신을 만족하는 시스템 성능을 가질수 없었다. 따라서 한번의 재전송만을 고려한 Truncated Type-II Hybrid ARQ기법을 동시에 채용함으로써 다중접속 간섭과 임펄스 잡음에 의한 전송에러를 감소시키고 고신뢰도의 무선 데이터 통신을 만족하는 시스템 성능을 보임을 알 수 있었다.

• Journal of Communications and Networks
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• v.13 no.3
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• pp.250-256
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• 2011

A two-way relaying (TWR) system is analyzed, where two source terminals with unequal numbers of antennas exchange data via an amplify-and-forward relay terminal with a single antenna. In the system considered herein, the link quality between the sources and relay can generally be asymmetric due to the nonidentical antenna configuration, power allocation, and relay location. In such a general setup, accurate bounds on the average sum rate (ASR) are derived when beamforming or orthogonal space time block coding is employed at the sources. We show that the proposed bounds are almost indistinguishable from the exact ASR under various system configurations. It is also observed that the ASR performance of the TWR system with unequal numbers of source antennas is more sensitive to the relay location than to the power allocation.