• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.3
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• pp.405-409
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• 2002

Recently, the FCC commissioners approved limited uses of UWB, and have promised to review the standards to explore the potential of more flexible standards and to address the operation of additional types of UWB operations and technology. In this paper we study performances of UWB communication system according to M-ary schemes with BCH code. And under the AWGN channel, we analysis and compare error probability, the number of M-ary schemes to the two methods that pulse position modulation and pulse amplitude modulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.426-433
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• 2008

In this paper, we present a method to improve the performance of the four transmit antenna quasi-orthogonal space-time block code (STBC) in the coded system. For the four transmit antenna case, the quasi-orthogonal STBC consists of two symbol groups which are orthogonal to each other, but intra group symbols are not. In uncoded system with the matched filter detection, constellation rotation can improve the performance. However, in coded systems, its gain is absorbed by the coding gain especially for lower rate code. We propose an iterative decoding method to improve the performance of quasi-orthogonal codes in coded systems. With conventional quasi-orthogonal STBC detection, the joint ML detection can be improved by iterative processing between the demapper and the decoder. Simulation results shows that the performance improvement is about 2dB at 1% frame error rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.2
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• pp.164-176
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• 1989

With reference to the Spread Spectrum techniqeu diseussed and further extended by many investigators, the Peseudo-noise Code Polarity Modulation (PNCPM) technique has proposed in this paper. By using this new technique of PNCPM, some problems pertaining to the Spread Spectrum mode has been sloved. In addition by the PNCPM mode it is proposed that data shifting can be easily demodulated every clock(frame) by measn of simple hardware implementaton for the purpose of operating of the asynchroniged detection mode. And in this paper it is shown that PNCPM mode can be easily implemented by the CCD correlator, and is applicable to the Spread Spectrum Multiple Access.

• Journal of the Korea Society of Computer and Information
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• v.11 no.5 s.43
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• pp.203-209
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• 2006

In this paper, proposed diversity algorithm that decrease fading. In the wireless channel, if fading occurs due to the multipaths the performance of the system is apparently reduced. This study applied tap-delay receiver. It applied QPSK and OQPSK modulation methods and applied the convolutional codes, where the code rate is 1/2 and 1/3 and the constraint length is 11 and the turbo code where the constraint length is 6. The diversity algorithm proposed in this paper could be compared and analyzed the average error probability of modulation method variable of fading factor to uplink and downlink channels.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.3 no.2
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• pp.61-71
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• 2004

Transorthogonal 코드를 블록 단위로 확장해서 얻은 코드 집합을 적절하게 부집합으로 나누고 부호화기의 코드집합으로 할당한다. 이러한 부초화기를 병렬로 구성하고 정보 비트에 의해 선택된 부호화기의 각 출력 코드들을 합산하여 전송하는 다중코드 transorthogonal 변조 방식이 제안되어 있다. 본 논문에서는 다중코드 transorthogonal 변조 시스템의 부호화기로부터의 각 출력 코드를 또 다른 정보 비트로 이진 위상 변조한 후 합산하여 전송하는 시스템을 제안한다. 다중코드 transorthogonal 변조 시스템에서 적용된 정 진폭 부호화 알고리즘과정 전폭 부호화에 사용된 잉여비트를 이용한 수신 에러 정정 알고리즘을 제안된 시스템에 수정 없이 적용할 수 있으며 다중코드 transorthogonal 변조 방식에 비해 대역폭 효율이 개선됨을 보인다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.34-43
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• 1994

The unequal symbol error probability of TCM(trellis coded modulation) is analyzed and applied to the derivation of bit error probability of /RS/Trellis concatenated coded-modulation system. An upper bound of the symbol error probability of TCM concatenated with RS code is obtained by exploiting the unequal symbol error probability of TCM, and it is applied to the derivation of the upper bound of the bit error probability of the RS/Trellis concatenated coded-modulation system. Our upper bounds of the concatenated codes are tighter than the earlier established other upper bounds.

• Journal of electromagnetic engineering and science
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• v.7 no.1
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• pp.1-6
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• 2007

Recently, Mc(Multi-code) modulation/demodulation(modem) technique has been explored for high speed data transmission in wireless environment. The conventional Mc modem generates some side effects such as allocating Walsh codes, which motivates to propose a novel Mc modem method with sub-code. Our proposed system should expanded the size of sub-code to provide high-rate data transmission, which also affect adversely to the performance of the system with high PAPR(Peak to Average Power Ratio). Thus, in this paper, we propose a novel pre-coded Multi-Dimensional HCOC(High Capacity Orthogonal Code) Mc modem technique to reduce the high PAPR, which enables the performance improvement. This proposed system can be easily designed by concatenating HCOC Mc modem with the generic Mc modem. The pre-coding technique that is used in this paper is CAC(Constant Amplitude Coding), that helps the system maintain the constant transmission power and reduce the maximum transmission power.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.49-56
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• 2006

In this paper, to overcome the effect of nonlinear power amplifier, CE-CPSK(Constant Envelope Continuous Phase Shift Keying)modulation method which has the constant envelope and continuous phase characteristics is proposed. The code acquisition performances of the CE-CPSK modulated system and BPSK system are analyzed. And the performance is evaluated in terms of mean acquisition time and detection probability with the output backoff of the amplifier in multiuser environment. Results performed in a channel having a high degree of AM nonlinearity(AM-to-AM conversion), have shown that the CE-CPSK signal, when passed through class C-nonlinear Amplifier, has a spectrum with greatly reduced sidelobes compared to the conventional BPSK signal. The code acquisition performance of a CE-CPSK modulation system is better than that of BPSK system with nonlinear amplified multiuser environments.

• The KIPS Transactions:PartC
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• v.12C no.6 s.102
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• pp.901-906
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• 2005

In this paper, we propose a novel MHCOC (Mapped High Capacity Orthogonal Code) SS(Spread Spectrum) technique that reduces high PAPR (Peak power to Average Power Ratio) of HCOC SS system which was proposed to support high data rate transmission, and we compare to the conventional modulation technique such as MQAM SS that can transmit the same number of symbols at the same time. Moreover, we study on adaptation of this system to satisfy QoS (Quality of Service) that services the proper data rate according to the propagation channel quality information. We perform computer simulation to verify the performance of the proposed system and analyze its availability.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.9
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• pp.366-372
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• 2003

Multilevel coded modulation (MCM) with serial concatenated convolutional code (SCCC) is proposed and the performance is analyzed in this paper. Both high coding gain and bandwidth efficiency can be obtained if SCCC is adopted as a component code at the first level of MCM. Simulation results show that the performance of MCM with Ambroze's SCCC is saturated like that of MCM with PCCC. But MCM with Benedetto's SCCC shows no performance saturation and better performance than MCM with PCCC or Ambroze's SCCC. Thus MCM with Benedetto's SCCC may be a good choice for high quality system with limited bandwidth.