• Title/Summary/Keyword: OFDM System

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Analysis of OFDM system using TSTD method based on IEEE 802.11a (IEEE 802.11a에 기반한 OFDM 시스템에서 TSTD 방식 적용에 따른 성능분석)

  • 나상중;김병기;오동진;김철성
    • Proceedings of the IEEK Conference
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    • pp.198-201
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    • 2003
  • In this paper, we analyze high-rate orthogonal frequency division multiplexing(OFDM) system using time switched time diversity(TSTD) method based on IEEE 802.11a. First, we modeled the transmitter and receiver of OFDM system based on IEEE 802.11a. Then, we applied the TSTD to OFDM system. Finally we analyzed the performance of OFDM system using TSTD method by simulation over the 5GHz realistic channel model, where channel coding and channel equalizer over multipath environment are also applied.

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A Study for Reducing the PAPR in OFDM System (OFDM 시스템에서 PAPR 감소 방안에 관한 연구)

  • Kong, Hyung-Yun;Woo, Il-Seung
    • Proceedings of the IEEK Conference
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    • pp.57-60
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    • 2000
  • In this paper, we proposed new scheme to reduce the Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) system OFDM system is highlighted for multi-media communication system, however it has large PAPR. To reduce the PAPR in OFDM system, several techniques have been proposed such as clipping, coding and so on Our proposed method is a case of block coding and proposed system be termed Sub-Coding OFDM (SC-OFDM) system We also compare the performance between conventional and our proposed OFDM system by computer simulation.

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High-rate LDPC Coded OFDM System for Image Transmission over Rayleigh Fading Channel (레일리 페이딩 채널에서 이미지 전송을 위한 고속 LDPC부호를 적용한 OFDM 시스템)

  • Choi, Sang-Min;Moon, Byung-Hyun
    • Proceedings of the KIEE Conference
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    • pp.233-235
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    • 2005
  • As a class of block codes, LDPC code with any desired code rate and code length is easily constructed. In OFDM system high data transmission is possible, In this paper, we examined the performance of four high-rate(0.75, 0.8, 0.889, 09412) LDPC coded OFDM in image transmission over Rayleigh fading channel. The high-rate of 0.9412 LDPC coded OFDM system obtained about 12dB gain over the OFDM at BER of $10^{-3}$ over Rayleigh fading channel. Also, the PSNR of code rate 0.9412 LDPC coded OFDM system at SNR=10dB is given by 18.8047dB where uncoded OFDM system gives 9.7303 dB.

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Achievable Bit Rate Comparison of Cyclic Prefixed CI/OFDM System and Single Carrier System (Cyclic Prefixed CI/OFDM 시스템과 단일반송파 시스템의 ABR 비교 분석)

  • Zheng, Hui;Hwang, Jae-Ho;Hwnag, Dae-Geun;Kim, Jae-Moung
    • Journal of Satellite, Information and Communications
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    • v.5 no.1
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    • pp.6-16
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    • 2010
  • Since OFDM system suffers from high peak-to average power ratio(PAPR) drawbacks, more energy has been converted to seek for a new substitutable system which can maintain OFDM system's inherent virtues while avoid its defects. Consequently, a new multicarrier system called as CI/OFDM system has been proposed which applied carrier interferometry(CI) code to OFDM system. Due to its low PAPR advantage and orthogonal property, it has received more and more attention. Simultaneously, an old technique called single carrier(SC) system has retaken its attractions for the same purposes. This paper analyzes two cyclic prefixed transmission schemes variants of OFDM system: 1.carrier interferometry-Orthogonal Frequency-Division Multiplexing (CI/OFDM); 2. Cyclic prefixed single carrie(CP-SC) with frequency domain equalization. We compare the achievable bit rate transmission of the two systems in terms of signal to noise ratio(SNR) by mathematical derivation. We demonstrated that CI/OFDM achieves a bit higher transmission bit rate to that of the CP-SC with frequency domain equalizer.

Performance improvement of XCP-OFDM system using cross-handed circular polarization in frequency offset environments (주파수 오프셋 환경에서의 역선회 원편파를 이용한 XCP-OFDM 시스템의 성능 개선)

  • 김병옥
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.8 no.1
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    • pp.49-56
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    • 2004
  • An OFDM system using cross-handed circular Polarization(XCP-OFDM) is newly proposed in his paper. The proposed XCP-OFDM system divides the subchannels into a right-handed circular polarization(RHP channel and a left-handed circular polarization(LHCP) channel that alternate each other. Therefore, the overlaps between subcarriers in XCP-OFDM system can be reduced to a great extend compared to the conventional OFDM system. By this reason, it can improve the orthogonality and reduce the inter-channel interference due to frequency offset. In this paper, it can be seen that the proposed XCP-OFDM system shows robust against frequency offset.

A Parallel Combinatory OFDM System with Weighted Phase Subcarriers

  • Zheng, Hui;Shrestha, Robin;Hwang, Jae-Ho;Kim, Jae-Mong
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.1
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    • pp.322-340
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    • 2012
  • Orthogonal Frequency Division Multiplexing (OFDM) is usually regarded as a spectral efficient multicarrier modulation technique, yet it suffers from a high peak-to-average power ratio (PAPR) problem. Among all the existing PAPR reduction techniques in OFDM systems, side information based PAPR reduction techniques such as partial transmit sequence (PTS) and selective mapping (SLM) schemes, have attracted the most attention. However, the transmission of side information results in somewhat spectral loss and this does not significantly improve the bit error rate (BER) performance. Parallel combinatory (PC) OFDM yields higher spectral efficiency (SE) and better BER performance on Gaussian channels,while is a little but not obvious PAPR improvement over the ordinary OFDM system. This investigation aimed to design a 'perfect' OFDM system. We introduce the side information to rotate the subcarrier phases of our novel PC-OFDM system structure, and call this new system the SIPC(Side information based Parallel Combinatory)-OFDM system. The proposed system achieves better PAPR and SE performance. In addition, considering the tradeoff of system parameters, the proposed system also has the properties of a higher BER.

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.

Linearization of OFDM signal using Predistorter (OFDM 신호의 사전 왜곡제거기를 이용한 비선형 왜곡보상)

  • 신은영;방성일
    • Proceedings of the IEEK Conference
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    • pp.339-342
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    • 2002
  • In this paper, the structure of OFDM system is studied, and causes of inter carrier interference (ICI) are analyzed. Based on analysis, this paper shows a technique to prevent a distortion due to nonlinearity of high Power amplifier. The proposed scheme is a predistorter for high power amplifier linearization in orthogonal frequency division multiplexing (OFDM) system used in wireless local area network(WLAN). This is verified by comparing BER characteristics of OFDM system, between used PD and not used PD.

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Novel Doppler effects compensation schemes based on constellation estimation of OFDM system

  • Lee, Byung-Seub
    • Journal of Satellite, Information and Communications
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    • v.12 no.2
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    • pp.79-82
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    • 2017
  • A new and effective Doppler effects compensation scheme for orthogonal frequency division multiplex(OFDM) system based on constellation estimation is presented with analytical descriptions which quantitatively clarify the mechanism of inter-carrier interference(ICI). The proposed compensation techniques, applicable both frequency and time domain with remarkable accuracy, are crucial to the future OFDM system operating on ultra high speed mobile vehicles.

An Enhanced BLAST-OFDM System With Spatial Diversity and interleaved Frequency Diversity (공간 다이버시티 및 인터리빙 주파수 다이버시티 기반 BLAST-OFDM 시스템)

  • 황현정;김낙명
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.8C
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    • pp.1040-1046
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    • 2004
  • The BLAST-OFDM system is an efficient method for high data rate multimedia transmission in futurewireless communication system. In this paper, a linear preceding mechanism and an efficient antenna-subcarrier assignment algorithm are proposed for the conventional BLAST-OFDM system, in order to utilize the full spatial diversity and the interleaved frequency diversity. By computer simulation, the proposed system has proved to achieve 4-5㏈ gain over the conventional BLAST-OFDM system.