• ETRI Journal
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• v.36 no.2
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• pp.206-213
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• 2014

This paper presents a novel 90 GHz band 16-quadrature amplitude modulation (16-QAM) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 6 Gbps through six channels with a bandwidth of 3 GHz. Each channel occupies 500 MHz and delivers 1 Gbps using 16-QAM OFDM. To implement the system, a low-noise amplifier and an RF up/down conversion fourth-harmonically pumped mixer are implemented using a $0.1-{\mu}m$ gallium arsenide pseudomorphic high-electron-mobility transistor process. A polarization-division duplex architecture is used for full-duplex communication. In a digital modem, OFDM with 256-point fast Fourier transform and (255, 239) Reed-Solomon forward error correction codecs are used. The modem can compensate for a carrier-frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of $10^{-5}$ at a signal-to-noise ratio of about 19.8 dB.

• ETRI Journal
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• v.34 no.5
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• pp.649-654
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• 2012

This paper presents a novel 16-quadrature-amplitude-modulation (QAM) E-band communication system. The system can deliver 10 Gbps through eight channels with a bandwidth of 5 GHz (71-76 GHz/81-86 GHz). Each channel occupies 390 MHz and delivers 1.25 Gbps using a 16-QAM. Thus, this system can achieve a bandwidth efficiency of 3.2 bit/s/Hz. To implement the system, a driver amplifier and an RF up-/down-conversion mixer are implemented using a $0.1{\mu}m$ gallium arsenide pseudomorphic high-electron-mobility transistor (GaAs pHEMT) process. A single-IF architecture is chosen for the RF receiver. In the digital modem, 24 square root raised cosine filters and four (255, 239) Reed-Solomon forward error correction codecs are used in parallel. The modem can compensate for a carrier-frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of $10^{-5}$ at a signal-to-noise ratio of about 21.5 dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.1083-1096
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• 1997

To implement satellite B-ISDN/ATM network, it needs to gurantee reliable transport via satelite in the poor BER environment. So, it requires to use channel coding (FEC:Forward Error Correction) schemes for improvement of BER performance, but these coding effects evoke burst errors and degradation of the QoS. Therefore we have to investigate new algorithm that compensates these weaknesses. We consider convolutional coding and concatenated coding among FEC schemes as FEC for satellite transmission and choose different compensational algorithm by the error characteristics of the using type of FEC. In using concatenated coding, this paper proposes the satellite system structure for interconnection to the terrestrial network and proposes the channel coding algorithm for improvement of transmission performances. We execute performance evaluation of the proposed algorithm by computer simulation. In detail, we propose 4 types of application ATM cell to the block coding(Reed-Solomon) and propose the new 55 byte ATM cell that enforces the error correction capability of cell header by the BCH coding. Then we propose the outer interleaverand the cell unit interleaver that evoke maximum coding effect of BCH code.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.39-50
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• 2010

In this paper, we analyze and simulate the performance of a tactics mobile communication system based on ultra wide band (UWB) in multi-user interference (MUI) environments. This system adopts a double binary turbo code for forward error correction (FEC). Wireless channel is modeled a modified Saleh and Valenzuela (SV) model. We employ a space time block coding (STBC) scheme for enhancing system performance. System performance is evaluated in terms of bit error probability. From the simulation results, it is confirmed that the tactics mobile communication system based on UWB, which is encoded with the double binary turbo code, can achieve a remarkable coding gain with reasonable encoding and decoding complexity in multi-user interference environments. It is also known that the bit error probability performance of the tactics mobile communication system based on UWB can be substantially improved by increasing the number of iterations in the decoding process for a fixed cod rate. Besides, we can demonstrate that the double binary turbo coding scheme is very effective for increasing the number of simultaneous users for a given bit error probability requirement.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.400-402
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• 2005

전파(propagation) 오류가 빈번한 무선 이동 네트워크에서는 전송 성능을 향상하기 위해 FEC(Forward Error Correction) 알고리즘을 채택한다. 그러나 정적인 FEC 코드 제어 방식은 연속적으로 변화하는 전파 오류율에 알맞은 정정 코드(check code)를 적용하지 못해 성능이 저하된다. 일례로 측정한 고 오류 무선 센서 네트워크에서는 초단위 평균 BER(Bit Error Rate) 또는 분단위 평균 BER이 0에서 최대 $10^{-3}$까지 연속적으로 변화한다. 이러한 무선 환경에서 전파 오류를 $100\%$ 복구하기 위한 정정 코드를 채택하는 경우에는, 불필요한 정정 코드량은 전체 데이터에 최대 $20\%$를 차지한다. 본 논문에서는 무선 채널의 BER을 직접 측정하지 않고 패킷 전송 성공 여부에 따라 정정 코드의 량, 즉 FEC단계를 동적으로 변화하는 AFECCC (Adaptive FEC Code Control) 알고리즘을 소개한다. AFECCC는 트레이스 기반(trace-driven) 시뮬레이션에서 정적 FEC 방식에 비해 최대 $5\%$ 이상, 또한 실제 센서 네트워크에서는 정적 FEC 알고리즘에 비해 최대 $15\%$ 성능이 향상되었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10C
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• pp.605-613
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• 2011

In most digital communication systems over the noisy channel, some form of forward error correction scheme is employed for reliable communications. If one wants to recover the transmitted message without any knowledge of the error correcting codes employed, it is of utmost importance to figure out and reconstruct the error correcting codes. In this paper, we propose two algorithms of reconstructing linear cyclic codes from the corrupted received bit sequence, one for general linear binary cyclic codes and the other for Reed-Solomon codes. For two algorithms, we ran computer simulations and the performances are shown to be superior to those with the conventional LWM method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.895-900
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• 2011

To improve drawback of existing modulation method, in this paper, we propose the channel forecast method using adaptive modulation which can improve throughput of channel. This method adaptively changes modulation method to the change of channel environments. In proposed method, channel's characteristics are measured in realtime to determine code rate to the changes of demanded channel's bit error rate. If bit error rate is increased, this method reduce code rate to maintain maximum throughput. We analysis performance of proposed method by Matlab.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.11B
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• pp.1864-1871
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• 2000

본 논문에서는 차세대 무선 통신 시스템에 적용이 가능한 새로운 FEC(Forward Error Correction) 부호화 방법으로 MLC(Multi-Level Convolutional) 부호화 방식을 제안한다. 차세대 무선통신서비스는 음성, 데이터, 영상 등 많은 종류의 서비스를 함으로써 데이터의 처리속도가 빠른 시스템이 요구된다. 데이터 처리시간을 단축시키기 위한 방법으로 다중 레벨을 이용하여 부호어를 만들어 내는 방식의 부호화 시스템을 설계하였다. MLC는 부호 처리시간을 단축시킬 뿐만 아니라 다양한 알고리즘을 이용해 부호어를 만들어 낼 수 있다는 특징을 가지게 된다. 모의실험은 MLC 코드의 두 가지 방법, Modulo- operation 방식과 Galois Field-Operation 방식을 이용하여 수행하였다. 또한 모의실험을 통하여 (s=2, T=2)인 경우가 MLC 부호기의 최적 연결다항식임을 알았다.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.4
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• pp.207-215
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• 2009

In recent digital communication systems, the performance of Turbo Code used as the error correction coding method depends on the interleaver size influencing the free distance determination and iterative decoding algorithms of the turbo decoder. However, some iterations are needed to get a better performance, but these processes require large time delay. Recently, methods of reducing the number of iteration have been studied without degrading original performance. In this paper, the new method combining ME (Mean Estimate) stopping criterion with SDR (sign difference ratio) stopping criterion of previous stopping criteria is proposed, and the fact of compensating each method's missed detection is verified Faster decoding realizes that reducing the number of iterative decoding about 1~2 times by adopting our proposed method into serially concatenation of both decoder. System Environments were assumed DS-CDMA forward link system with intense MAI (multiple access interference).

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2006.05a
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• pp.143-147
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• 2006

Wireless sensor networks(WSN) technology has various applications such as surveillance and information gathering in the uncontrollable area of human. One of major issues in WSN is the research for reducing the energy consumption and reliability of data. A system with forward error correction(FEC) can provide an objective reliability while using less transmission power than a system without FEC. In this paper, we propose to use LDPC codes of various code rate(0.53, 0.81, 0.91) for FEC for WSN. Also, we considered node-to-node interference in addition to AWGN channel. The proposed system has not only high reliable data transmission at low SNR, but also reduced transmission power usage.