• Title/Summary/Keyword: Frequency-selective Fading Channel

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Performance Analysis of Multiband Transmission Technique in Underwater Acoustic Communication (수중 음향 통신에서 다중 밴드 전송 기법의 성능 분석)

  • Lee, Hui-Su;Baek, Chang-Uk;Do, Dae-Won;Jung, Ji-Won
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.11 no.3
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    • pp.253-258
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    • 2018
  • The multiband communication technique is effective in terms of performance and throughput efficiency because it can overcome selective frequency fading by allocating the same data to different frequency bands in the environment of rapidly changing channel transfer characteristic. In addition, the transmission distance can be further extended while overcoming various underwater channel environments. In this paper, we analyzed the performance of multiband transmission technique in underwater communication by increasing number of band using Turbo pi code with a coding rate of 1/3. Simulation results shows that the performance is improved when the number of bands is increased based on the received SNR.

Link Scheduling Method Based on CAZAC Sequence for Device-to-Device Communication (D2D 통신 시스템을 위한 CAZAC 시퀀스 기반 링크 스케줄링 기법)

  • Kang, Wipil;Hwang, Won-Jun;Choi, Hyung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.4
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    • pp.325-336
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    • 2013
  • FlashLinQ, one of the typical D2D communication systems developed by Qualcomm, considers a single-tone communication based distributed channel-aware link scheduling method to realize the link scheduling process with low control overheads. However, considering the frequency selective fading effect of practical multi-path channel, the single-tone based SIR estimation causes a critical scheduling error problem because the received single-tone signal has quite different channel gain at each sub-carrier location. In order to overcome this problem, we propose a novel link scheduling method based on CAZAC (Constant Amplitude Zero Auto-Correlation) sequence for D2D communication system. In the proposed method, each link has a unique offset value set for the generation of CAZAC sequences. CAZAC sequences with the cyclic offsets are transmitted using multiple sub-blocks in the entire bandwidth, and then each device can obtain nearly full-band SIR using a good cyclic cross-correlation property of CAZAC sequence.

Performance of Decorrelator for Multirate Multicarrier DS/CDMA System (다중전송률 다중반송파 DS/CDMA 시스템을 위한 비상관기의 성능)

  • Lee, Seok-Hyun;Lee, So-Young;Kim, Jin-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.10 no.6
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    • pp.31-37
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    • 2010
  • In this paper, a performance of a decorrelating detector for a multirate MC(multi-carrier) DS/CDMA system is analyzed and simulated in a frequency selective Rayleigh fading channel. The performance is compared with that of single rate MC-DS/CDMA system in term of bit error probability. Variable Spreading Length (VSL) is employed for MC-DS/CDMA system as multirate transmission scheme. From simulation result, it is shown that Decorrelator for multirate MC-DS/CDMA achieves high BER performance as well as that of single rate case.

Performance analysis of MC-CDMA Mobile Communication Systems with Smart Antennas (스마트 안테나를 적용한 MC-CDMA 시스템의 성능 분석)

  • 이종길
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.7 no.4
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    • pp.667-672
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    • 2003
  • Smart antennas will be used mon widely for the higher data rate and the larger number of users as the demand of wireless multimedia service is increased. Therefore, the BER performance is analyzed in this paper for DS-CDMA and MC-CDMA systems using smart antennas. A reverse link channel is simulated assuming the frequency selective Rayleigh fading. The simulation results are presented based on the characteristics of DS-CDMA and MC-CDMA systems according to the signal spectrum bandwidth and the method of adaptive beamforming. The BER performances of both systems are improved as the beam width of smart antennas is decreased. Also, it is shown that the performance of MC-CDMA system is much better than that of DS-CDMA system as the number of users is increased.

Performance of QS-CDMA Systems with a Novel Class of Sequences (새 수열을 쓴 유사동기 부호분할 다중접속 시스템의 성능)

  • Park, Seong-Il;Park, So-Ryoung;Song, Iick-Ho;Yoon, Seok-Ho;Lee, Joo-Shik
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.36S no.11
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    • pp.1-8
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    • 1999
  • In this paper, new polyphase sequences and a sequence generation method are suggested. These sequences are found to have good correlation properties. Since the suggested generation method consists only of integer sums and modular techniques, sequence generation is also easy. The performance of the sequences is investigated when used in QS-CDMA systems under frequency selective, time nonselective, slow Nakagami fading channel with additive white Gaussian noise.

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8 Antenna Polar Switching Up-Down Relay Networks

  • Li, Jun;Lee, Moon-Ho;Yan, Yier;Peng, Bu Shi;Hwang, Gun-Joon
    • Journal of electromagnetic engineering and science
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    • v.11 no.4
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    • pp.239-249
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    • 2011
  • In this paper, we propose a reliable $8{\times}8$ up-down switching polar relay code based on 3GPP LTE standard, motivated by 3GPP LTE down link, which is 30 bps/Hz for $8{\times}8$ MIMO antennas, and by Arikan's channel polarization for the frequency selective fading (FSF) channels with the generator matrix $Q_8$. In this scheme, a polar encoder and OFDM modulator are implemented sequentially at both the source node and relay nodes, the time reversion and complex conjugation operations are separately implemented at each relay node, and the successive interference cancellation (SIC) decoder, together with the cyclic prefix (CP) removal, is performed at the destination node. Use of the scheme shows that decoding at the relay without any delay is not required, which results in a lower complexity. The numerical result shows that the system coded by polar codes has better performance than currently used designs.

Orthogonal Code Sharing and Radio Resource Allocation in Multibeam Satellite Communication Systems (다중빔 위성 통신 시스템에서 빔간 직교 코드 공유 기법과 동적 무선 자원 할당)

  • Lim, Kwang-Jae;Kim, Soo-Young;Oh, Deok-Gil;Kim, Jae-Moung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.3A
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    • pp.140-150
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    • 2003
  • In this paper, we propose a novel code sharing method for downlink transmission of mobile satellite communication systems using a multibeam geosynchronous-orbit satellite. In the proposed system, spreading codes are shared among downlink beams in order to increase the system capacity. We also propose efficient radio resource and transmit power allocation schemes for the proposed system. Simplified analysis and simulation results on the system capacity show the capacity improvement by the proposed scheme. The simulation results show that the capacity of the proposed system is more than 2 times as large as that of a conventional multibeam satellite system. In the frequency-selective fading channel, the capacity improvement increases as the interference between orthogonal spreading codes decrease.

Multiuser Bit-Interleaved Coded OFDM with Limited Feedback Infonnation (제한된 궤환정보를 이용한 다중사용자 BIC-OFDM)

  • Sung, Chang-Kyung;Kim, Ji-Hoon;Lee, In-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.2A
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    • pp.107-114
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    • 2008
  • In wireless access systems, there has been much interest in enhancing the performance of orthogonal frequency division multiplexing OFDM) in a frequency selective fading channel. If the channel is static and is perfectly known to both the transmitter and the receiver, the water-filling technique with adaptive modulation is known to be optimal. However, for OFDM systems, this requires intensive traffic overheads for reporting channel side information on all subcarriers to the transmitter In this paper, we propose an adaptive modulation and coding scheme for bit-interleaved coded OFDM (BIC-OFDM) for downlink packet transmissions with reduced feedback information. To minimize the feedback information, we employ a rate adaptation method based on the OFDM symbol rather than on each subcarrier. To illustrate the performance gap between the optimal water-filling and the proposed scheme, we will compare cutoff rates for both schemes. It is shown that the loss is less than 2dB while the proposed scheme significantly reduces the feedback payloads. Also, the OFDM system in multiuser environment with subcarrier grouping is considered. It is shown that by exploiting multiuser diversity the throughput of the proposed scheme approaches the channel outage capacity as the number of users and the number of subcarrier groups increase.

Performance Evaluation of Underwater Acoustic Communication in Frequency Selective Shallow Water (주파수 선택적인 천해해역에서 수중음향통신 성능해석)

  • Park, Kyu-Chil;Park, Jihyun;Lee, Seung Wook;Jung, Jin Woo;Shin, Jungchae;Yoon, Jong Rak
    • The Journal of the Acoustical Society of Korea
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    • v.32 no.2
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    • pp.95-103
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    • 2013
  • An underwater acoustic (UWA) communication in shallow water is strongly affected by the water surface and the seabed acoustical properties. Every reflected signal to receiver experiences a time-variant scattering in sea surface roughness and a grazing-angle-dependent reflection loss in bottom. Consequently, the performance of UWA communication systems is degraded, and high-speed digital communication is disrupted. If there is a dominant signal path such as a direct path, the received signal is modeled statistically as Rice fading but if not, it is modeled as Rayleigh fading. However, it has been known to be very difficult to reproduce the statistical estimation by real experimental evaluation in the sea. To give an insight for this scattering and grazing-angle-dependent bottom reflection loss effect in UWA communication, authors conduct experiments to quantify these effects. The image is transmitted using binary frequency shift keying (BFSK) modulation. The quality of the received image is shown to be affected by water surface scattering and grazing-angle-dependent bottom reflection loss. The analysis is based on the transmitter to receiver range and the receiver depth dependent image quality and bit error rate (BER). The results show that the received image quality is highly dependent on the transmitter-receiver range and receiver depth which characterizes the channel coherence bandwidth.

A New SLM Method using Dummy Sequence Insertion far the PAPR Reduction of the OFDM Communication System (OFDM통신 시스템의 PAPR저감을 위한 Dummy Sequence를 삽입하는 새로운 SLM 기법)

  • 이재은;허근재;김상우;유흥균
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.4
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    • pp.379-386
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    • 2004
  • OFDM(orthogonal frequency division multiplexing) communications system is very attractive for the high data rate transmissionin the frequency selective fading channel. Since OFDM has high PAPR(peak-to-average power ratio), OFDM signal may be distorted by the nonlinear HPA(high power amplifier). In this paper, we propose an improved dummy sequence scheme for reducing the PAPR in OFDM communication system. This method inserts each different dummy sequence at the predefined sub-carriers fur PAPR reduction. After IFFT, the OFDM data signal with the lowest PAPR is selected to transmit. The complementary sequence is used as dummy sequence. So, it can cut down the computation time and quantity because it dose not require the peak value optimization for finding the phase rotation factor and the transmission of the side information about the rotation factor unlike the PTS method.