• Title/Summary/Keyword: carrier frequency

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Phase Tracking for Orthogonal Frequency Division Multiplexing Systems (직교 주파수 분할 다중화 시스템을 위한 위상 오차 추적)

  • Jeon, Tae-Hyun
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.12 s.354
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    • pp.61-67
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    • 2006
  • This paper proposes the algorithm for tracking of the residual phase errors incurred by carrier frequency offset and sampling frequency offset in the orthogonal frequency division multiplexing (OFDM) systems which are suitable for high data rate wireless communications. In the OFDM systems the subcarriers which are orthogonal to each other are modulated by digital data and transmitted simultaneously. The carrier frequency offset causes degradation of signal to noise ratio(SNR) performance and interference between the adjacent subcarriers. The errors in the sampling timing caused by the sampling frequency difference between the transmitter and the receiver sides also cause a major performance degradation in the OFDM systems. The residual error tracking and compensation mechanism is essential in the OFDM system since the carrier and the sampling frequency offset cause the loss of orthogonality resulting in the system performance loss. This paper proposes the scheme where the channel gain and the payload data information are reflected in the residual error tracking process which results in the reduction of the estimation error and the tracking performance improvements under the frequency selective fading wireless channels.

A Basic Study on the Design of the GPS Receiver (GPS의 수신기 개발을 위한 기초연구)

  • 정세모;정규형
    • Journal of the Korean Institute of Navigation
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    • v.6 no.1
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    • pp.1-18
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    • 1982
  • In this paper, author studied on the elementary data required for the design of the receiver of Pseudo Noise (PN) phase modulation communication adopted in Global Positioning System(GPS). By computer simulation technique, the phase modulator, filters, and PN generator are designed, and also required bandwidth of R-F amplifier for carrier frequency in phase modulation system is investigated. It is verified that the optimum bandwidth is about 3 times of the PN frequency and almost independent of the carrier frequency. And the low pass filter required for demodulation of slow Boolean data is also found to be about 60 times of the data signal frequency.

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Terahertz Oscillations in p-Type Quantum-Well Oscillators

  • Cao, J.C.;Li, A.Z.
    • Journal of Korean Vacuum Science & Technology
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    • v.6 no.1
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    • pp.43-45
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    • 2002
  • We have theoretically investigated steady-state carrier transport and current self-oscillation in negative-effective-mass (NEM) p$\^$+/pp$\^$+/diodes. The current self-oscillation here is a result of the formation and traveling of electric field domains in the p base having a NEM. The dependence of self-oscillating frequency on the applied dc voltage is obtained by detailed numerical simulations. In the calculations, we have considered the scatterings by carrier-impurity, carrier-acoustic phonon, carrier-polar-phonon, and carrier-nonpolar-phonon-hole interactions . This kind of NEM oscillator allows us to reach a current oscillation with terahertz frequency, thus it may be used as a broadband source of terahertz radiation.

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The Proposal of Efficient Hit Prevention Technique according to the Frequency Hopping Pattern in Orthogonal Multi-Carrier FH/CDMA System (직교 멀티캐리어 FH/CDMA 시스템에서 주파수 도약 패턴에 따른 효율적인 충돌 방지 기법 제안)

  • 이문승
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.6 no.2
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    • pp.141-150
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    • 2002
  • In this paper, we composed orthogonal multi carrier FH/CDMA system using frequency hopping sequence. Considering hit possibilities by delayed other user's signals we searched the optimal number of user access carrier slots not to influence on performance deterioration with the variation of number of carrier slots according to the number of user access carrier slots. A]io, we evaluated the BER performance improvement due to TCM and Concatenated coding technique by computer simulation.

3-Phase Pseudo-Random Carrier Modulation Technique for the Acoustic Noise Reduction of the 3-Phase Multi-Level Inverter Based Motor (3상 멀티 레벨 인버터 구동 유도 전동기의 소음저감을 위한 3상 준 랜덤 캐리어 변조기법)

  • Park, J.K.;Kim, J.N.;Jung, Y.G.;Lim, Y.C.
    • Proceedings of the KIPE Conference
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    • 2005.07a
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    • pp.742-745
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    • 2005
  • This paper describes a simple pseudo-random carrier modulation technique for the acoustic noise reduction of the three phase multi-level inverter based motor drives. The proposed method generates a new pseudo-random carrier by randomly synthesizing a carrier with fixed frequency and a carrier with opposition phase. To confirm the validity of the proposed method, a 130v three-phase multi-level inverter was Implemented and tested. The experimental results show that the output line voltage and acoustic noise harmonics spectra of an inverter have broadening effect of harmonics, as only simple synthesis of fixed frequency carries.

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A Study on a New Carrier Recovery Algorithm for Coherent Burst-mode Communication Systems (동기식 버스트 통신시스템 적용을 위한 새로운 반송파 동기 기법에 관한 연구)

  • Park, Sung-Bok
    • Journal of the Korea Institute of Military Science and Technology
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    • v.14 no.6
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    • pp.1043-1048
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    • 2011
  • In this paper, a newsynchronization technique applied to burst-mode communication is proposed. A synchronization technique is to estimate carrier frequency and phase offsets in a noisy channel environment. A fundamental problem for estimating the parameters(carrier phase and frequency offsets) in burst-mode transmission is that the ways of pursuing estimation accuracy and transmission efficiency are always trade-off. To solve this problem, a new carrier recovery technique is proposed to improve the transmission efficiency with reliable performance especially at low S/N. In the proposed technique, the synchronization parameters are first estimated based on a data-aided feed-forward estimation scheme. Then, a phase tracker using decision-directed DPLL estimates the phase offset for the data portion of the burst data. From simulation results, it shows fast synchronization with shorter preamble maintaining reasonable BER performance at low S/N.

Performance Analysis of Multi-Carrier CDMA Trellis Coded 16 QAM System with Near/Far Effect in Frequency Selective Multipath Fading Channel (주파수 선택성 다중경로 페이딩 채널에서 Near/Far 영향을 받는 Multi-Carrier CDMA Trellis Coded 16 QAM 시스템의 성능해석)

  • 노재성;강희조;김춘길;김언곤;조성준
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.3A
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    • pp.352-361
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    • 2000
  • The performance of a multi-carrier CDMA system is analyzed considering frequency selective multipath fading and Near/Far effects. The number of multicarrier, multiuser, and arms of RAKE receiver, and the decay ratio of frequency selective multipath fading are used as a parameter for the performance analysis. More over, the distribution and the strength of multiuser interference are also considered. To evaluate the Near/Far effects in a multi-carrier CDMA system, three distribution models are assumed. In the first model, interference to carrier Ratio, I/C, ranges from -4 dB to 4dB, and at each 2 dB interval, 20 % of multiuser is assumed to be uniformly distributed. In the second one, I/C ranges from -2 dB to 2 dB, and 33.3% of multiuser is assumed to be equally dispersed at each 2dB interval. The third model is 0 dB of I/C, that is, with perfect power control, multiuser are assumed to be evenly located. In this paper, multi-carrier CDMA system adoption RAKE receiver is proposed to mitigate the frequency selective multipath fading. From the results, the third model(i.e. perfect power control) shows the best performance, and the narrower range of I/C causes the less effects to the desired signal, which reads to the better performance.

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Multiple Access Interference Cancellation for IFDMA Systems with Frequency Offsets (IFDMA 시스템에서 주파수 옵셋에 의한 다중접속간섭 제거 기법)

  • Kim, Jeong-Woo;Won, Yu-Jun;Seo, Bo-Seok
    • Journal of Satellite, Information and Communications
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    • v.6 no.1
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    • pp.32-36
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    • 2011
  • In this paper, we propose a cancellation scheme of multiple access interference (MAI), which is caused by carrier frequency offset, for the receiver of an interleaved orthogonal frequency division multiple access (IFDMA) uplink system. In the IFDMA systems, carrier frequency offsets introduce adjacent channel interference from other users' subcarriers, which results in performance degradation. In the proposed method, we compensate the carrier frequency offset in time domain and then eliminate MAI by using parallel interference cancellation in frequency domain. Simulation results show that the proposed method is effective in removing the MAI especially when the number of users are large and the MAI severely degrades the system performance.

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.

Scheduling for Virtual MIMO in Single Carrier FDMA (SC-FDMA) System

  • Kim, Jinwoo;Hwang, In Seok;Kang, Chung Gu
    • Journal of Communications and Networks
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    • v.17 no.1
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    • pp.27-33
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    • 2015
  • In this paper, we consider a joint frequency-domain scheduling and user-pairing problem for virtual MIMO in the single carrier frequency division multiple access (SC-FDMA) system, e.g., the uplink transmission for third generation partnership project-long term evolution (3GPP-LTE) standard. Due to the subcarrier adjacency constraint inherent to SC-FDMA, its complexity becomes unmanageable. We propose a greedy heuristic algorithm for PF scheduling so as to deal with the complexity issue in this joint problem. It has been shown that its performance can reach up to 90% of its upper bound.