• Title/Summary/Keyword: Diversity Channel

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Multi-Relay Cooperative Diversity Protocol with Improved Spectral Efficiency

  • Asaduzzaman, Asaduzzaman;Kong, Hyung-Yun
    • Journal of Communications and Networks
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    • v.13 no.3
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    • pp.240-249
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    • 2011
  • Cooperative diversity protocols have attracted a great deal of attention since they are thought to be capable of providing diversity multiplexing tradeoff among single antenna wireless devices. In the high signal-to-noise ratio (SNR) region, cooperation is rarely required; hence, the spectral efficiency of the cooperative protocol can be improved by applying a proper cooperation selection technique. In this paper, we present a simple "cooperation selection" technique based on instantaneous channel measurement to improve the spectral efficiency of cooperative protocols. We show that the same instantaneous channel measurement can also be used for relay selection. In this paper two protocols are proposed-proactive and reactive; the selection of one of these protocols depends on whether the decision of cooperation selection is made before or after the transmission of the source. These protocols can successfully select cooperation along with the best relay from a set of available M relays. If the instantaneous source-to-destination channel is strong enough to support the system requirements, then the source simply transmits to the destination as a noncooperative direct transmission; otherwise, a cooperative transmission with the help of the selected best relay is chosen by the system. Analysis and simulation results show that these protocols can achieve higher order diversity with improved spectral efficiency, i.e., a higher diversity-multiplexing tradeoff in a slow-fading environment.

Relationships between Diversity Techniques and Channel Coding Rates for SC-FDMA Systems (SC-FDMA 시스템에서의 다이버시티 기술과 채널부호화율의 관계)

  • Rim, Min-Joong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.1A
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    • pp.1-11
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    • 2009
  • In OFDMA or SC-FDMA systems one can generate time varying channels or frequency selective channels using multiple transmit antennas to achieve diversity without special space-time processing at the receivers. While low channel coding rate needs to be used for distributed-allocation SC-FDMA systems with a phase rolling technique to produce time fluctuation, relatively high channel coding rate can be used when cyclic delay diversity is used to increase frequency selectivity assuming quasi-static channel. On the other hand, for block-hopping SC-FDMA systems there is no significant difference between two diversity techniques in terms of optimal channel coding rates.

Optimal Diversity-Multiplexing Tradeoff of MIMO Multi-way Relay Channel

  • Su, Yuping;Li, Ying
    • ETRI Journal
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    • v.35 no.5
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    • pp.919-922
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    • 2013
  • A MIMO multi-way relay channel with full data exchange in which K users exchange messages with each other via the help of a single relay is considered. For the case in which each link is quasi-static Rayleigh fading and the relay is full-duplex, the fundamental diversity-multiplexing tradeoff (DMT) is investigated, and we show that a compress-and-forward relay protocol can achieve the optimal DMT.

Performance Analysis of Noncoherent Transmit Diversity System over Correlated Rayleigh Fading Channel (상관된 레일레이 페이딩 채널에서 비동기 송신 다이버시티 시스템 성능해석)

  • 여민기;한영열
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.2
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    • pp.208-216
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    • 2001
  • Signal Fading due to multipath propagation severely impairs the performance of high-speed mobile communication systems. Effective diversity scheme for fading channel is STTD (Space Time Transmitter Diversity) method. This scheme is very simple and using 2 transmit antennas and 1 receive antenna provides a diversity order of two[1],[2]. In this paper, we derive the new probability density function of the envelope of the received signal over correlated Rayleigh fading channel. Using the new pdf of the envelope we analyze the performance of noncoherent M-ary FSK, DPSK and ASKSTTD (Space Time Transmitter Diversity) a system on correlated Rayleigh fading channel.

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A Composite LMMSE Channel Estimator for Spectrum-Efficient OFDM Transmit Diversity

  • Seo, Jeong-Wook;Jeon, Won-Gi;Paik, Jong-Ho;Jo, Min-Ho;Kim, Dong-Ku
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.2 no.4
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    • pp.209-221
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    • 2008
  • In this paper, we propose a subcarrier allocation method and a composite linear minimum mean square error (LMMSE) channel estimator to increase spectrum efficiency in orthogonal frequency division multiplexing (OFDM) transmit diversity. The pilot symbols for OFDM transmit (Alamouti) diversity are exclusively allocated in two OFDM symbols in different antennas, which causes serious degradation of spectrum efficiency. To reduce the number of pilot symbols, our subcarrier allocation method uses repetition-coded data symbols, and the proposed channel estimator maintains good bit error rate (BER) performance.

A Scheme of Channel Diversity Load Balancing Consideration for Path Selection in WMNs

  • Gao, Hui;Kwag, Young-wan;Lee, Hyung-ok;Nam, Ji-seung
    • Proceedings of the Korea Information Processing Society Conference
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    • 2014.04a
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    • pp.249-251
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    • 2014
  • This paper proposes a channel diversity based load-balancing cross-layer routing scheme for Wireless Mesh Networks (WMNs). The proposed scheme deals with channel diversity phase and load balancing phase in WMNs. Channel diversity factor $metric_{ch-d}$ and load balancing factor $f_{load}$ are defined and employed cooperatively as a combined path selection policy.

Equal Gain Block Decomposition Methods for Multiuser MIMO Networks

  • Hwang, Insoo;Kang, Inseok;Hwang, Intae;You, Cheolwoo
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.15 no.3
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    • pp.1156-1173
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    • 2021
  • In this paper, we propose a new joint precoder and postcoder design strategy to support multiple streams per user in multiuser multiple-input multiple-output (MIMO) systems. We propose two step precoding strategies using equal channel gain decomposition and block diagonalization at the transmitter. With the proposed precoder, the multiuser MIMO channel can be decomposed into multiple parallel channels with equal channel gain per user. After applying receive postcoder which is generated and sent by the transmitter, we can use ML based decoder per stream to achieve full receive diversity. Achievable sum rate bound and diversity performance of the proposed algorithm are presented with feedback signaling design and quantitative complexity analysis. Simulation results show that the proposed algorithm asymptotically approaches to the sum rate capacity of the MIMO broadcast channel while maintaining full diversity order.

Performance Analysis of Angle Time Transmit Diversity in Urban Area (도심환경에서 각도-시간 송신다이버시티의 성능분석)

  • Park, Byeong-Hoon
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.60 no.4
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    • pp.200-205
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    • 2011
  • In multipath fading channel, diversity is essential to mitigate the impairments. In this paper, we have proposed the angle diversity scheme called ATTD(Angle Time Transmit Diversity) instead of Alamouti's STTD(Space Time Transmit Diversity) and have analyzed the performance of the proposed scheme when signal powers caused by the transmission to different angles are different. Based on it, we have measured the wireless vector-channel in the urban area, which has lots of high-story buildings, using the data collected from the 8 by 4 smart array antenna system that we made. According to the measured data, the received signals from different angles have different signal powers. Our performance analysis results show that the proposed scheme has better performance than the space diversity scheme when the received path signal power is at least -7dB compare to the strongest path signal power.

Turbo Equalization and Decoding with Diversity Reception on the Frequency-Selective Fading Channel (주파수 선택적 페이딩 채널에서의 다이버시티 수신 터보 등화 및 복호화)

  • 임동민
    • Proceedings of the IEEK Conference
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    • 1999.11a
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    • pp.39-42
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    • 1999
  • In this paper, a method based on the turbo principle is presented which combines diversity reception, equalization, and channel decoding, to combat the high transmission losses over the frequency-selective fading channel. The simulation results show that with the method presented, the BER performance within 0.3 ㏈ from that on the AWGN channel can be obtained over the frequency-selective fading channel in the investigated scenarios.

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