• Title/Summary/Keyword: Multiplexing scheme

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Collision Dispersion Based on Orthogonal Pre-Spreading in Orthogonal Code Hopping Multiplexing (OCHM 시스템에서 전확산에 의한 충돌 분산 기법)

  • Kwon, Jae-Kyun;Jung, Bang-Chul;Yun, Kyung-Su;Sung, Dan-Keun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.9A
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    • pp.679-684
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    • 2009
  • A collision dispersion scheme based on orthogonal pre-spreading is proposed to reduce the effect of collisions that occur in orthogonal code hopping multiplexing(OCHM). The OCHM scheme was previously proposed to accommodate a significantly larger number of low-activity bursty channels than the number of orthogonal codewords. The proposed scheme greatly reduces the required SNR in channel decoding. In addition, the proposed scheme can be applied to OFHM based on OFDM.

A New Polarization Diversity Scheme for Orthogonal Polarization and Frequency Division Multiplexing System

  • Ido, Jun;Okada, Minoru;Komaki, Shozo
    • Proceedings of the IEEK Conference
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    • 2000.07b
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    • pp.973-976
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    • 2000
  • This paper proposes a new polarization diversity scheme for OPFDM (Orthogonal Polarization and Frequency Division Multiplexing). OPFDM is an extension of OFDM (Orthogonal Frequency Division Multiplexing) in conjunction with polarization multiplexing in order to ensure the orthogonality amongst subcarriers. Since OPFDM uses two orthogonally polarized channels, it can easily employ the polarization diversity. In order to get the diversity gain effectively in a frequency selective fading channel, the proposed scheme combines the signals in subcarrier-by-subcarrier basis. The computer simulation results confirm that the proposed scheme is superior to conventional one in the two orthogonally polarized two-ray Rayleigh fading channels with cross-talk between the two channels.

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Improved Orthogonal Code Hopping Multiplexing Using Both Division and Hopping

  • Kwon, Jae-Kyun;Park, Su-Won;Sung, Dan-Keun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.3A
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    • pp.277-285
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    • 2008
  • We previously proposed an Orthogonal Code Hopping Multiplexing (OCHM) scheme for statistical multiplexing on a synchronous downlink. OCHM enables a large number of users to share a limited number of code channels through statistical multiplexing. We here improve the performance of OCHM by prioritizing encoded symbols according to their importance using both the conventional code division and the previously proposed code hopping multiplexing schemes. Prioritization is useful for channel coding schemes with different levels of importance for encoded symbols such as turbo-codes. Scheme performance is evaluated by simulation in terms of the required Eb/N0 for a 1% block error rate.

A Low-Complexity Frequency Offset Estimation Scheme Based on Partial Periodogram for OFDM-Based CR Systems (OFDM 기반 CR 시스템을 위한 부분 주기도표 기반의 저복잡도 주파수 옵셋 추정 기법)

  • Chong, Da-Hae;Park, Jong-In;Bae, Jin-Soo;Yoon, Seok-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.10C
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    • pp.635-640
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    • 2011
  • This paper proposes a frequency offset estimation scheme with low-complexity for orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems. The proposed scheme is applicable to any type of training symbol and has a lower complexity than the scheme in [9] by using the partial periodogram. Simulation results show that the estimation performance of the proposed scheme is almost the same as that of the scheme in [9].

A New Efficient Group-wise Spatial Multiplexing Design for Closed-Loop MIMO Systems (폐루프 다중입출력 시스템을 위한 효율적인 그룹별 공간 다중화 기법 설계)

  • Moon, Sung-Myun;Lee, Heun-Chul;Kim, Young-Tae;Lee, In-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.4A
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    • pp.322-331
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    • 2010
  • This paper introduces a new efficient design scheme for spatial multiplexing (SM) systems over closed loop multiple-input multiple-output (MIMO) wireless channels. Extending the orthogonalized spatial multiplexing (OSM) scheme which was developed recently for transmitting two data streams, we propose a new SM scheme where a larger number of data streams can be supported. To achieve this goal, we partition the data streams into several subblocks and execute the block-diagonalization process at the receiver. The proposed scheme still guarantees single-symbol maximum likelihood (ML) detection with small feedback information. Simulation results verify that the proposed scheme achieves a huge performance gain at a bit error rate (BER) of $10^{-4}$ over conventional closed-loop schemes based on minimum mean-square error (MSE) or bit error rate (BER) criterion. We also show that an additional 2.5dB gain can be obtained by optimizing the group selection with extra feedback information.

Transmit Diversity Using Windowing Scheme in OFDM System (OFDM 시스템에서 윈도윙 기법을 이용한 송신 다이버시티)

  • Kim, Yong-June;Rim, Min-Joong;Lim, Dae-Woon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.9A
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    • pp.871-877
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    • 2007
  • In this paper, we propose a new transmit diversity scheme using window functions in orthogonal frequency division multiplexing (OFDM) system. Transmit diversity of the scheme is varied with window functions and the condition of the window function to maximize transmit diversity is derived. The proposed scheme can be considered as a generalization of the diversity schemes such as cyclic delay diversity (CDD), orthogonal transmit diversity (OTD), and frequency switched transmit diversity (FSTD).

Constant Envelope Multiplexing via Constellation Tailoring Scheme for Flexible Power Allocation of GNSS Signals

  • Shin, Janghwan;Joo, Jung-Min;Lim, Deok Won;Ahn, Jae Min
    • Journal of Positioning, Navigation, and Timing
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    • v.10 no.4
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    • pp.335-340
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    • 2021
  • A constant envelope multiplexing via constellation tailoring scheme is proposed for flexible power allocation of Global Navigation Satellite System (GNSS) signals. The proposed scheme is compared with the coherent adaptive subcarrier modulation (CASM) adopted in the L1 band signals of the Global Positioning System (GPS) in terms of power difference and power loss. Analysis of the constellation optimization results on the power difference and power loss show that the proposed scheme outperforms the CASM of the GPS signals in the allowable power difference of less than 0.1 dB.

Design of New Closed-Loop Spatial Multiplexing System Using Linear Precoder (선형 선부호기를 이용한 새로운 폐루프 공간 다중화 시스템 설계)

  • Chae, Chang-Hyeon;Choi, Dae-Won;Jung, Tae-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.1A
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    • pp.44-49
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    • 2008
  • Recently, a so called orthogonal spatial multiplexing(OSM) scheme was presented which allows simple maximum likelihood decoding at the receiver with single phase feedback In this paper, by serially concatenating this scheme by a linear precoder, a new closed-loop SM scheme is proposed for two transmit arid two receive antennas. By computer simulation results, we show that the proposed scheme outperforms the conventional SM and OSM. For the proposed code, we also propose a new simple decoding algorithm which leads to a greatly reduced decoding complexity compared with the ML receiver without any loss of error performance.

Performance Analysis of Iterative Detection Scheme for the D-STTD System

  • Yoon, Gil-Sang;Lee, Jeong-Hwan;Cho, In-Sik;Seo, Chang-Woo;Ryoo, Sang-Jin;You, Cheol-Woo;Hwang, In-Tae
    • Journal of information and communication convergence engineering
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    • v.7 no.2
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    • pp.235-240
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    • 2009
  • This paper combines various detection techniques and analyzes their performances in detecting the transmission information of the D-STTD scheme that uses, in parallel, the STTD scheme known as the Alamouti code. The D-STTD scheme adopts one of the STTD schemes for transmission to acquire diverse effects and uses another form of STTD for multiplexing effects. Due to the multiplexing effect that transmits different data, it is difficult to apply D-STTD to the conventional STTD combining technique. This paper combines the D-STTD system with linear algorithm, SIC algorithm and OSIC algorithm known as multiplexing detection scheme based on MMSE scheme. And we propose the detection scheme of the D-STTD using MAP algorithm and analyze the performance of each system. The simulation results showed that the detector using iterative algorithm has better performance than Linear MMSE Detector. Especially, we can show that the detector using MAP algorithm outperforms conventional detector.

Adaptive TR Scheme for PAPR Reduction in OFDM Systems (OFDM 시스템의 PAPR 감소를 위한 적응적 TR 기법)

  • Lim, Dae-Woon;Noh, Hyung-Suk;No, Jong-Seon;Shin, Dong-Joon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.7C
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    • pp.554-561
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    • 2008
  • For the tone reservation (TR) scheme in orthogonal frequency division multiplexing (OFDM), there exists a trade-off between peak to average power ration (PAPR) reduction performance and data transmission rate. While PRT set is fixed in the conventional TR scheme, the proposed scheme adaptively select the PRT set according to the PAPR of the input OFDM symbol. It is shown that the PAPR reduction performance of the proposed scheme is better than that of the conventional scheme when the data transmission rate is the same.