151 research outputs found
Experimental and Analytical Investigations of an Optically Pre-Amplified FSO-MIMO System With Repetition Coding Over Non-Identically Distributed Correlated Channels
This paper presents theoretical and experimental bit error rate (BER) results for a freespace optical (FSO) multiple-input-multiple-output system over an arbitrarily correlated turbulence channel.
We employ an erbium-doped fiber amplifier at the receiver (Rx), which results in an improved Rx’s sensitivity
at the cost of an additional non-Gaussian amplified spontaneous emission noise. Repetition coding is used
to combat turbulence and to improve the BER performance of the FSO links. A mathematical framework
is provided for the considered FSO system over a correlated non-identically distributed Gamma-Gamma
channel; and analytical BER results are derived with and without the pre-amplifier for a comparative study.
Moreover, novel closed-form expressions for the asymptotic BER are derived; a comprehensive discussion
about the diversity order and coding gain is presented by performing asymptotic analysis at high signal-tonoise ratio (SNR). To verify the analytical results, an experimental set-up of a 2 × 1 FSO-multiple-inputsingle-output (MISO) system with pre-amplifier at the Rx is developed. It is shown analytically that, both
correlation and pre-amplification do not affect the diversity order of the system, however, both factors have
contrasting behaviour with respect to coding gain. Further, to achieve the target forward error correction
BER limit of 3.8 × 10−3
, a 2 × 1 FSO-MISO system with a pre-amplifier requires 6.5 dB lower SNR
compared with the system with no pre-amplifier. Moreover, an SNR penalty of 2.5 dB is incurred at a higher
correlation level for the developed 2×1 experimental FSO set-up, which is in agreement with the analytical
findings
On the Performance of Millimeter Wave-based RF-FSO Links with HARQ Feedback
This paper studies the performance of hybrid radio-frequency (RF) and
free-space optical (FSO) links in the cases with and without hybrid automatic
repeat request (HARQ). Considering millimeter wave (mmwave) characteristics in
the RF link and pointing errors in the FSO link, we derive closed-form
expressions for the message decoding probabilities as well as the throughput
and the outage probability of the RF-FSO setups. We also evaluate the effect of
various parameters such as power amplifiers efficiency, different transmission
techniques in the FSO link, pointing errors in the FSO link as well as
different coherence times/symbol rates of the RF and the FSO links on the
throughput and outage probability. The results show the efficiency of the
RF-FSO links in different conditions. Moreover, the HARQ can effectively
improve the outage probability/energy efficiency, and compensate the effect of
hardware impairments in RF-FSO links.Comment: Under review in PIMRC'201
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