Faculty Publications

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Author: search.filters.author.Krishnan, P.Subject: search.filters.subject.Modulation

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    Performance Analysis of Hybrid RF/FSO System Using BPSK-SIM and DPSK-SIM Over Gamma-Gamma Turbulence Channel With Pointing Errors for Smart City Applications
    (Institute of Electrical and Electronics Engineers Inc., 2018) Krishnan, P.
    The flourishing technology in wireless communication-free space optics (FSO) offers lots of merits over radio frequency (RF) links due to its license free bandwidth, ease of installation, high security features, and viable cost for short distance communication. It's high speed data rate and immunity against electromagnetic interference makes FSO the emerging technology of today. But, FSO is not always reliable especially during atmospheric conditions, such as fog, rain, mist, and snow. Hence, in account a new technique of hybrid FSO/RF, this includes advantages of both FSO and RF technologies. Through this paper intend to perform an extensive analysis of the error and misalignment effects encountered in line of sight communication. Pointing error and turbulence effects are the main drawback parameters for our analysis. For this purpose I have taken into consideration different modulation techniques-binary phase shift keying-subcarrier intensity modulation, differential phase shift keying-subcarrier intensity modulation communication system with reference to on-off keying (OOK) modulation. The novel expressions for outage probability and BER for both FSO and RF system are derived which uses Rician channel and 16QAM modulation scheme alongside hybrid FSO/RF system for weak, moderate, and strong turbulence regimes using Meijer-G function. © 2013 IEEE.
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    Analysis of beam divergence on free space optical link using polarization shift keying technique
    (SPIE spie@spie.org, 2019) Rajeev, M.; Mathew, G.A.; Krishnan, P.
    Beam diverging is an indispensable phenomenon on the quality and bit error rate (BER) performance of the free space optical (FSO) communication system. The role of an efficacious modulation technique that mitigates the combined effect of beam diverging and atmospheric attenuation is highly relevant. The weak depolarizing property of the atmosphere advances the use of polarization shift keying (PolSK) modulation. We are subjected to investigate the quality and feasibility of the communication link, considering the impact of beam divergence on the PolSK modulation under various weather conditions. It is shown that PolSK subdues the effects of increase in beam divergence, attenuation factor, and further extends the communication range. A comparison with on off keying and PolSK-based FSO links considering the divergence angle is discussed. Moreover, BER and quality factor graphs are plotted against link distance and beam divergence using PolSK, which improves the performance analysis. © 2019 Society of Photo-Optical Instrumentation Engineers (SPIE).