• Title, Summary, Keyword: OFDM

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STF-OFDM Transmission Scheme with Frequency Diversity (주파수 다이버시티를 갖는 STF-OFDM 전송 기법)

  • 박상순;황호선;백흥기
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.2C
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    • pp.206-212
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    • 2004
  • In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. STBC(Space-Time Block Coding) has been proposed as a simple diversity scheme using two transmit antennas. Also ST-OFDM(Space-Time Block Coded OFDM) and SF-OFDM(Space-Frequency Block Coded OFDM) transmission scheme, that the STBC is applied to the OFDM, has been proposed. In this paper, we propose STF-OFDM transmission scheme that to coded in time, space and frequency domain. The STF-OFDM transmission scheme that we propose in this paper is the way to improve a performance of conventional ST-OFDM, by using frequency diversity.

Performance Comparison of the OFDM/SFH and OFDM/DS Systems in the Jamming Channel (OFDM/SFH와 OFDM/DS 시스템의 Jamming 채널에서 성능비교)

  • 박종현;김상우;유흥균;이상태
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.11
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    • pp.1149-1155
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    • 2003
  • OFDM/SFH(orthogonal frequency division multiplexing/slow frequency hopping) system is the combination of OFDM communication system with frequency hopping(FH) method and OFDM/DS(orthogonal frequency division multiplexing/direct sequence) system combines the OFDM communication system with direct sequence(DS) method in terms of PN(pseudo noise) sequence. These two systems are also can be used for anti-jamming. In this study we analyze performances of OFDM/SFH system and OFDM/DS system with the equal information rate in partial band jamming and tone jamming channel. We find BER(bit error rate) in the variation of JFR(jamming fractional ratio) and JSR(jamming to signal power ratio) of the partial band jamming. Also, BER is found in the several JSR of the single tone or multi tone jamming. OFDM/DS system shows better performance than OFDM/SFH system in partial band jamming environment. OFDM/DS system has about 2.5 ㏈ SNR(signal to noise power ratio) gains than OFDM/SFH system when JFR=4/16 and JSR=0 ㏈ to meet BER=10$\^$-3/. However, OFDM/SFH system has about 3 ㏈ SNR gains than OFDM/DS system at single tone jamming of JSR=5 ㏈. In multi tone jamming, performance of OFDM/SFH system is considerably degraded than OFDM/DS system.

Performance Comparison of OFDM Based on Fourier Transform and Wavelet OFDM Based on Wavelet Transform (웨이블릿 변환 기반의 Wavelet-OFDM 시스템과 푸리에 변환 기반의 OFDM 시스템의 성능 비교)

  • Lee, Jungu;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.3
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    • pp.184-191
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    • 2018
  • Orthogonal frequency division multiplexing(OFDM) is a multicarrier modulation(MCM) system that enables high-speed communications using multiple carriers and has advantages of power and spectral efficiency. Therefore, this study aims to complement the existing shortcomings and to design an efficient MCM system. The proposed system uses the inverse discrete wavelet transform(IDWT) operation instead of the inverse fast Fourier transform(IFFT) operation. The bit error rate(BER), spectral efficiency, and peak-to-average power ratio(PAPR) performance were compared with the conventional OFDM system through the OFDM system design based on wavelet transform. Our results showed that the conventional OFDM and Wavelet-OFDM exhibited the same BER performance, and that the Wavelet-OFDM using the discrete Meyer wavelet had the same spectral efficiency as the conventional OFDM. In addition, all systems of Wavelet-OFDM based on various wavelets confirm a PAPR performance lower than that of conventional OFDM.

Design and Performance Evaluation of Adaptive OFDM Communication System Robust to the Narrow-band Interference (협대역 간섭에 강한 적응형 OFDM 통신 시스템 설계와 성능 평가)

  • Jung Rag-Gyu;Kim Sun-Ae;Ryu Heung-Gyoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.7
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    • pp.629-637
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    • 2006
  • It is important to design the high-speed communication system in the hostile channel. Due to the frequency diversity, FD-OFDM that can be used for the high-speed communication is more robust to the noise or interference than ordinary OFDM. However, even the FD-OFDM becomes degraded in th ε strong narrow band interference channel. In this paper, we propose an AFD-OFDM system and analyze the communication performances in order to find out the more robust communication system in the hostile channel. So, the AFD-OFDM system can cover the drawback of the FD-OFDM and improve the BER performance than FD-OFDM. From the simulation results, FD-OFDM shows better performance than the ordinary OFDM. Furthermore, AFD-OFDM shows more excellent performance than FD-OFDM in the strong narrow interference channel.

Design and Performance Evaluation of an Advanced CI/OFDM System for the Reduction of PAPR and ICI (PAPR과 ICI의 동시 저감을 위한 개선형 CI/OFDM 시스템 설계와 성능 평가)

  • Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.6A
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    • pp.583-591
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    • 2008
  • OFDM (orthogonal frequency division multiplexing) has serious problem of high PAPR (peak-to-average power ratio). Recently, CI/OFDM (carrier interferometry OFDM) system has been proposed for the low PAPR. However, CI/OFDM system shows another problem of ICI because of phase offset mismatch due to the phase noise. In this paper, to simultaneously reduce the PAPR and ICI effects, we propose an A-CI/OFDM (advanced-CT/OFDM). This method improves the BER performance by use of the margin of phase offset at CI codes. Propose system to reduce the effect the phase noise, even though it shows a little bit higher PAPR than conventional CI/OFDM, so we apply the PTS among the PAPR reduction techniques to proposed system to mitigate this problem. Therefore, it improves the total BER performance because the proposed method can decrease the effect of phase noise and get the gain in PAPR reduction performance. From the simulation results, we can show the performance comparison between the conventional OFDM, CI/OFDM and A-CI/OFDM.

Comparison and Performance analysis of Wavelet OFDM system and FD-OFDM (웨이블릿 OFDM 시스템과 FD-OFDM 시스템 성능 비교 분석)

  • Lee, Junseo;Kim, Ji-Hoon;Kim, Whanwoo
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.7
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    • pp.34-42
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    • 2013
  • In this paper, we compare the performance of wavelet OFDM (Orthogonal Frequency Division Multiplexing) and FD-OFDM(Frequency diversity OFDM) system with conventional OFDM system. Wavelet OFDM system uses wavelet transform rather than Fourier transform and contains intermediate characteristics of CDM (Code Division Multiplexing) and OFDM. In wavelet OFDM system, inter-symbol interference (ISI) can be suppressed effectively and adjacent channel interference can be also minimized well. In FD-OFDM system, each parallel branch symbol is multiplied by the orthogonal sequence and distributed into all sub-carriers. Then, each sub-carrier transmits information composed of the symbol components of all parallel branches in the given frame. FD-OFDM contains the frequency diversity characteristic and, therefore, FD-OFDM can be robust to the narrowband interference. For the comparison among different systems, BER (Bit-Error Rate) performances are evaluated in the presence of narrow-band interference and a harmonic noise channel. From the evaluation results, compared to the conventional OFDM, wavelet OFDM and FD-OFDM shows better robustness against the interference and, especially, wavelet OFDM is the most robust in harmonic noise channel.

Comparison of Time and Frequency Resources of DFT-s-OFDM Systems Using the Zero-Tail and Unique Word (Zero Tail과 Unique Word를 사용하는 DFT-s-OFDM 시스템들의 시간과 주파수 자원 비교)

  • Kim, Byeongjae;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.41 no.12
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    • pp.1715-1720
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    • 2016
  • In the upcoming 5-generation mobile communication system, various techniques for improving the power efficiency and spectral efficiency have been proposed. 5G mobile communication system also have been studied a lot of multi-carrier-based modulation techniques like the 4G mobile communication system. In this paper, we analyzed the conventional system structure of the Zero-tail DFT-s-OFDM and UW (Unique Word) -DFT-s-OFDM system based on DFT-s-OFDM system in these techniques. UW and zero are added and used each system, and CP is removed. the result of quality of systems for simulation, OOB(Out of Band) power of Zero-tail DFT-s-OFDM and UW-DFT-s-OFDM use the less time resource as long as CP length, also both systems are reduced about 11dB than DFT-s-OFDM system. In these result, Zero-tail DFT-s-OFDM and UW-DFT-s-OFDM system are more effective than DFT-s-OFDM system.

Performance Comparison of SFBC/SFTC-OFDM Systems Under MB-OFDM Interference (MB-OFDM UWB 신호 간섭하에서 SFBC/SFTC-OFDM 시스템들의 성능 비교)

  • Kim, Kyung-Seok;Song, Chang-Kun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.10A
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    • pp.968-975
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    • 2006
  • Research about the mode of MIMO that can get a coding benefit at the same time with a diversity benefit using a multiple antenna at the fading channel for a high-speed data transmission have been processed actively But the analysis about the interference of UWB system comes not to consist yet. So this paper analyzed the performance of the interference of UWB system to SFBC-OFDM and SFTC-OFDM system that applied a space block code which has a space diversity characteristic to OFDM system at MIMO channel. We shelved the performance that SFTC-OFDM system is robuster than SFBC-OFDM system under MB-OFDM UWB Interference.

A Study on the ZP-OFDM System Robust to Symbol Timing Offset (심볼 타이밍 옵셋에 강건한 ZP-OFDM 시스템에 관한 연구)

  • Chung, Jae-Pil
    • Journal of Advanced Navigation Technology
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    • v.15 no.6
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    • pp.1042-1046
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    • 2011
  • In this paper, we analyze the STO (Symbol Timing Offset) problem in conventional ZP-OFDM (Zero Padding-Orthogonal Frequency Division Multiplexing) systems and propose a robust ZP-OFDM system with bi-directional overlap-add scheme to overcome the problem. The proposed ZP-OFDM system is able to preserve the orthogonality between subcarriers and reduce the interference from other ZP-OFDM symbols due to the BOA scheme, which exploits both ZP intervals of the previous and the current ZP-OFDM symbols, even though serious STOs result from inaccurate symbol timing synchronization. Simulation results verify that the proposed ZP-OFDM system is superior to the conventional ZP-OFDM system.

OFDM/OQAM-IOTA System (OFDM/OQAM-IOTA 시스템)

  • Zhou, Xiao;Heo, Joo;Chang, KyungHi
    • Journal of Advanced Navigation Technology
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    • v.8 no.2
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    • pp.120-128
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    • 2004
  • Although conventional OFDM/QAM modulation scheme using guard interval is robust to channel induced ISI (Inter-Symbol Interference) in time-domain, it is very sensitive to ICI (Inter-Carrier Interference) due to doppler effect in frequency domain. OFDM/OQAM-IOTA modulation scheme utilizes IOTA (Isotropic Orthogonal Transform Algorithm) filter that has orthogonality in time and frequency domain so that it is robust to delay spread and doppler effect. OFDM/OQAM-IOTA system can increase bandwidth effeciency since it does not use guard interval. In this paper, we show the structure of OFDM/OQAM-IOTA and perfect channel estimation scheme for OFDM/OQAM-IOTA system. We also compare OFDM/OQAM-IOTA system and OFDM/QAM system in AWGN and 1-path Rayleigh fading channel. Simulation results show that OFDM/OQAM system outperforms OFDM/QAM system.

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