• Title/Summary/Keyword: multipath interference

Search Result 293, Processing Time 0.027 seconds

The Comparison of Filter Performance in UFMC systems (UFMC 시스템에서 필터성능 비교)

  • Lee, Kyuseop;Choi, Ginkyu
    • The Journal of the Institute of Internet, Broadcasting and Communication
    • /
    • v.17 no.6
    • /
    • pp.89-95
    • /
    • 2017
  • UFMC is known as a candidate for the 5G wireless communication system because it is robust against ICI and better performs in asynchronous situation than OFDM. In the UFMC system, the filtering is performed for each subband so the performance of the filter is very important. The Dolph-Chebyshev filter has been used in conventional UFMC system because of its small out-of-band radiation. However it has distortion in the sub-band and skirt characteristics is not good enough. Therefore, it is necessary to study a new type of UFMC filter which reduces the distortion in the subband and has sharp skirt characteristics. In this paper we analyze the effect of filter frequency response in UFMC system and suggest the wavelet based type of filter that substitutes the Dolph-ChebyShev filter used in the conventional UFMC system. The simulation results show that wavelet filter has better BER performance in multipath fading channels than conventional filters.

A Fast ICI Suppression Algorithm with Adaptive Channel Estimation for the LTE-Advanced Uplink System (LTE-Advanced 상향 링크 시스템을 위한 적응적 채널 추정을 통한 고속 ICI 제거 방법 연구)

  • Jeong, Hae-Seong;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.22 no.1
    • /
    • pp.30-37
    • /
    • 2011
  • In this paper, we propose a fast ICI suppression algorithm with adaptive channel estimation for the LTE-Advanced uplink system. In order to effectively remove phase noise and carrier frequency offset at time varying channel, we use the comb type pilot. The purpose is to improve performance by reducing computational complexity than conventional PNFS(Phase Noise & Frequency offset Suppression) algorithm. We reduce computational complexity by decreasing overlapping computation or unnecessary computation at conventional PNFS algorithm. Also, we propose an effective channel estimation method. We estimate and compensate multipath channel through the proposed adaptive channel estimation method. The BER performance of the proposed method is better about 0.5 dB than the conventional method at the Vehicular A channel.

Digital Chaotic Communication System Based on CDSK Modulation (CDSK 방식의 디지털 카오스 통신 시스템)

  • Bok, Junyeong;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.38A no.6
    • /
    • pp.479-485
    • /
    • 2013
  • Recently, interest for wireless communication technology with improved security and low eavesdropping probability is increasing rapidly recognizing that information security is an important. Chaos signal can be used encode information efficiently due to irregular phenomena. Chaotic signal is very sensitive to the initial condition. Chaos signal is difficult to detect the signal if you do not know the initial conditions. Also, chaotic signal has robustness to multipath interference. In this paper, we evaluate the performance of correlation delay shift keying (CDSK) modulation with different chaotic map such as Tent map, Logistic map, Henon map, and Bernoulli shift map. Also, we analyze the BER performance depending on the selection of spreading factor (SF) in CDSK. Through the theoretical analyses and simulations, it is confirmed that Henon map has better BER performance than the other three chaotic maps when spreading factor is 70.

Performance Analysis of Direction Finding Systems Using EM Simulation-based Array Manifolds (EM 시뮬레이션 기반의 어레이 매니폴드를 이용한 방향 탐지 시스템 성능 분석)

  • Kim, Jae-Hwan;Cho, Chihyun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.23 no.10
    • /
    • pp.1166-1172
    • /
    • 2012
  • In this paper, by using a commercial EM simulator, we could obtain the array manifold which are phase responses of an array antenna for the incident plane wave and then verified the effectiveness of methodology after comparing with the measurement. The result shows that the array manifold can be calculated including not only the phase response of the ideal point sources but also the influences of the mutual coupling between antennas and the installed platform. Also it can exclude the interference of strong broadcasting signal and the disturbance of the multipath in the calibration process. Finally, to predict the performances of direction finding systems, a novel method using both the EM simulation-based receiving signal and the sparsely sampled array manifold with the parabolic estimation is proposed. This method can be utilized in the various fields of direction-finding since it shows the superior predictive performance even in low SNR conditions.

From WiFi to WiMAX: Efficient GPU-based Parameterized Transceiver across Different OFDM Protocols

  • Li, Rongchun;Dou, Yong;Zhou, Jie;Li, Baofeng;Xu, Jinbo
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • v.7 no.8
    • /
    • pp.1911-1932
    • /
    • 2013
  • Orthogonal frequency-division multiplexing (OFDM) has become a popular modulation scheme for wireless protocols because of its spectral efficiency and robustness against multipath interference. Although the components of various OFDM protocols are functionally similar, they remain distinct because of the characteristics of the environment. Recently, graphics processing units (GPUs) have been used to accelerate the signal processing of the physical layer (PHY) because of their great computational power, high development efficiency, and flexibility. In this paper, we describe the implementation of parameterized baseband modules using GPUs for two different OFDM protocols, namely, 802.11a and 802.16. First, we introduce various modules in the modulator/demodulator parts of the transmitter and receiver and analyze the computational complexity of each module. We then describe the integration of the GPU-based baseband modules of the two protocols using the parameterized method. GPU-based implementations are addressed to explain how to accelerate the baseband processing to archive real-time throughput. Finally, the performance results of each signal processing module are evaluated and analyzed. The experiments show that the GPU-based 802.11a and 802.16 PHY meet the real-time requirement and demonstrate good bit error ratio (BER) performance. The performance comparison indicates that our GPU-based implemented modules have better flexibility and throughput to the current ones.

Transmission performance Improvement of Wireless ATM Cell in Fading Channel (페이딩 채널에서 무선 ATM 셀전송 성능개선에 관한 연구)

  • Chung, Boo-Young;Park, Ki-Sik;Kang, Young-Heung;Cho, Sung-Joon;Lee, Jin
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.9 no.2
    • /
    • pp.179-190
    • /
    • 1998
  • One of the most important topics of recent years is that a multimedia technology such as wireless ATM has been introduced in radio systems for video, voice and data transmission. A major problem in such systems is the occurrence of errors due to multipath fading or interference. To combat this problem, forward error correction (FEC) coding is commonly used as a means of eliminating these errors. This paper has analyzed theoretically the effect of fading to design effective wireless ATM system. The BER, CLR, and CER of wireless ATM system adopting FEC coding and diversity reception techniques have been derived in fading environment. Also, simulations of BER and CLR have been carried out and compared with the above theoretical results.

  • PDF

PAPR Reduction using Pre-emphasis and Clipping in OFDM Communication System

  • 유흥균;진병일
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.13 no.3
    • /
    • pp.263-268
    • /
    • 2002
  • DFDM is a good candidate for beyond-3G high-speed wireless communication application because of the robustness to the intersymbol interference and multipath fading. However. an OFDM signal has a serious problem of the high PAPR, which results in the significant nonlinear distortion when it passes through a nonlinear high power amplifier. We propose a new PAPR reduction method using pre-emphasis and clipping. Via the proposed method, the OFDM output signal can have a low PAPR and BER improvement. Then. de-emphasis process is requisite in OFDM receiver. PAPR is reduced to about 5.7 ㏈ at the CCDF= 10$\^$-3/ when the subcarrier number is 16, QPSK modulation is used. pre-emphasis change point Is 3/9 of the peak amplitude of the IFFT output and clipping level is 11 in the IFFT output amplitude. The required SNR at BER=10$\^$-3/ the proposed system is improved by 2 dB than that of the original OFDM system.

Performance Analysis of Underwater Acoustic Communication Systems with Turbo Equalization in Korean Littoral Sea (한국 연근해 환경에서 터보 등화기를 이용한 수중음향통신 시스템 성능 분석)

  • Park, Tae-Doo;Han, Jeong-Woo;Jung, Ji-Won;Kim, Ki-Man;Lee, Sang-Kook;Chun, Seung-Yong;Son, Kweon
    • The Journal of the Acoustical Society of Korea
    • /
    • v.32 no.2
    • /
    • pp.124-130
    • /
    • 2013
  • The performance of underwater acoustic communication system is sensitive to the ISI(Inter-Symbol Interference) due to delay spread develop of multipath signal propagation. The equalizer is used to combat the ISI. In this paper, the performances of underwater acoustic communication with turbo equalizer were evaluated by real data collected in Korean littoral sea. As a result, when one iterative decoding using turbo equalizer is applied, the performance was improved 1.5 dB than the case of the non-iterative equalizer at BER $10^{-4}$. In the case of two or three iterations the performance was enhanced about 3.5 dB, but the performance wasn't improved any more in the case of more than three times.

A Parallel Equalization Algorithm with Weighted Updating by Two Error Estimation Functions (두 오차 추정 함수에 의해 가중 갱신되는 병렬 등화 알고리즘)

  • Oh, Kil-Nam
    • Journal of the Institute of Electronics Engineers of Korea TC
    • /
    • v.49 no.7
    • /
    • pp.32-38
    • /
    • 2012
  • In this paper, to eliminate intersymbol interference of the received signal due to multipath propagation, a parallel equalization algorithm using two error estimation functions is proposed. In the proposed algorithm, multilevel two-dimensional signals are considered as equivalent binary signals, then error signals are estimated using the sigmoid nonlinearity effective at the initial phase equalization and threshold nonlinearity with high steady-state performance. The two errors are scaled by a weight depending on the relative accuracy of the two error estimations, then two filters are updated differentially. As a result, the combined output of two filters was to be the optimum value, fast convergence at initial stage of equalization and low steady-state error level were achieved at the same time thanks to the combining effect of two operation modes smoothly. Usefulness of the proposed algorithm was verified and compared with the conventional method through computer simulations.

The Study of Space-Time Code using Z·F Detection Technique for Underwater Communication Environment (수중 통신 환경에서 Z·F 검출기법을 이용한 시공간 부호화 방식 연구)

  • Park, Tae-doo;Park, Gun-yeol;Jung, Ji-won;Kim, Beom Mu;Jeon, Sung Min;Lee, Seong-Ro
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • 2013.10a
    • /
    • pp.405-408
    • /
    • 2013
  • The performance of underwater acoustic(UWA) communication system is sensitive to the Inter-Symbol Interference(ISI) due to delay spread develop of multipath signal propagation. And due to limited frequency using acoustic wave, UWA is a low transmission rate. Thus, it is necessary technique of Space-time code, equalizer and channel code to improve transmission speed and eliminate ISI. In this paper, UWA communication system were analyzed by simulation using these techniques. In the result of simulation, the proposed Space-time code, Turbo code, and Zero forcing techniques is shown that improved performance than conventional UWA communication.

  • PDF