On the communication over strong atmospheric turbulence channels by adaptive modulation and coding

Department of Electrical and Computer Engineering, University of Arizona, Tucson, AZ 85721, USA.
Optics Express (Impact Factor: 3.49). 09/2009; 17(20):18250-62. DOI: 10.1364/OE.17.018250
Source: PubMed

ABSTRACT The free-space optical (FSO) communications can provide any connectivity need at high-speed. However, an optical wave propagating through the atmosphere experiences the variation in amplitude and phase due to scintillation. To enable high-speed communication over strong atmospheric turbulence channels, we propose to transmit the encoded sequence over both FSO and wireless channels, feedback channel state information of both channels by RF-feedback, and adapt powers and rates so that total channel capacity is maximized. The optimum power adaptation policy maximizing total channel capacity is derived. We show significant spectral efficiency performance improvement by employing this approach. We further show that deep fades in the order 35 dB and above can be tolerated by proposed hybrid communication scheme.

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Available from: Goran Djordjevic, Sep 29, 2015
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    • "Furthermore, in the former implementation frequent switching between the FSO and RF links, called flapping, can lead to a collapse of the communication system, and in later one retransmission of data over the insecure RF link leads to an insecure communication system. Our study therefore focuses on another implementation, parallel transmission systems, in which each link takes responsibility of carrying one portion of the data (i.e., the RF link is used for transmitting actual information and does not act only as a backup for the FSO link) [8]– [11]. In addition, towards efficient data transmission for such systems, we are also interested in link adaptations, which have recently received significant research attention. "
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    ABSTRACT: This paper presents a concept of parallel Free-Space Optics/Millimeter-Wave (FSO/MMW) systems, in which adaptive rate is employed in both FSO and MMW links. We newly propose an analytical framework based on Markov chain model for system performance analysis. System performance metrics, including throughput and reliability rate, are analytically studied under the presence of various weather conditions. Numerical results quantitatively show how the adaptive-rate FSO/MMW significantly outperform conventional ones, and how weather conditions affect on the systems performance.
    Proc. of the 21st Asia-Pacific Conference on Communications (APCC2015), Kyoto, Japan; 10/2015
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    • "In [34], a variable rate FSO system employing adaptive Turbo-based coding schemes with on-off keying (OOK) formats was investigated. In [12] [14], an adaptive transmission scheme that varied both the power and the modulation order of a FSO system with M-ary pulse amplitude modulation (MPAM) has been studied. In [10], an adaptive transmission technique employing subcarrier phase shift keying (S-PSK) intensity modulation has been proposed. "
    Optical Communication, Edited by Dr. Narottam Das, 01/2012: chapter Rate-Adaptive Free-Space Optical Links Over Atmospheric Turbulence and Misalignment Fading Channels: pages 321-340; InTech., ISBN: 978-953-51-0784-2
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    • "In [15], a variable rate FSO system employing adaptive Turbo-based coding schemes in conjunction with On-Off keying modulation was investigated, while in [16] an adaptive power scheme was suggested for reducing the average power consumption in constant rate optical satellite-to-earth links. Recently, in [17], an adaptive transmission scheme that varied both the power and the modulation order of a FSO system with pulse amplitude modulation (PAM), has been studied. "
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    ABSTRACT: We propose an adaptive transmission technique for free space optical (FSO) systems, operating in atmospheric turbu-lence and employing subcarrier phase shift keying (S-PSK) inten-sity modulation. Exploiting the constant envelope characteristics of S-PSK, the proposed technique offers efficient utilization of the FSO channel capacity by adapting the modulation order of S-PSK, according to the instantaneous state of turbulence induced fading and a pre-defined bit error rate (BER) requirement. Novel expressions for the spectral efficiency and average BER of the proposed adaptive FSO system are presented and performance investigations under various turbulence conditions, turbulence models, and target BER requirements are carried out. Numerical results indicate that significant spectral efficiency gains are offered without increasing the transmitted average optical power or sacrificing BER requirements, especially in moderate-to-strong turbulence conditions. Furthermore, the proposed variable rate transmission technique is applied to multiple input multiple output (MIMO) FSO systems, providing additional improvement in the achieved spectral efficiency as the number of the transmit and/or receive apertures increases.
    IEEE Transactions on Communications 05/2011; 59(5):1368 - 1377. · 1.99 Impact Factor
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