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


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,
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    • "The knowledge of CSIT is feasible for FSO channels given that scintillation is a slow time varying process relative to the large symbol rate. In this way, the CSI can be acquired by using the training sequence at the receiver side and feedback the CSI back to transmitter [11]. Here, it is considered that all the bits detected at the relay node are always forwarded with the new power to the destination node D regardless of these bits are detected correctly or incorrectly. "

    IEEE Photonics Technology Letters 12/2015; PP:1-1. DOI:10.1109/LPT.2015.2492622 · 2.11 Impact Factor
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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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