11,073 research outputs found
Performance analysis of FSO using relays and spatial diversity under log-normal fading channel
The performance analysis of free space optical communication (FSO) system
using relays and spatial diversity at the source is studied in this paper. The
effect of atmospheric turbulence and attenuation, caused by different weather
conditions and geometric losses, has also been considered for analysis. The
exact closed-form expressions are presented for bit error rate (BER) of M-ary
quadrature amplitude modulation (M-QAM) technique for multi-hop multiple-input
single-output (MISO) FSO system under log-normal fading channel. Furthermore,
the link performance of multi-hop MISO and multi-hop single-input and
single-output (SISO) FSO systems are compared to the different systems using
on-off keying (OOK), repetition codes (RCs) and M-ary pulse amplitude
modulation (M-PAM) techniques. A significant performance enhancement in terms
of BER analysis and SNR gains is shown for multi-hop MISO and multi-hop SISO
FSO systems with M-QAM over other existing systems with different modulation
schemes. Moreover, Monte-Carlo simulations are used to validate the accuracy
and consistency of the derived analytical results. Numerical results show that
M-QAM modulated multi-hop MISO and multi-hop SISO FSO system with relays and
spatial diversity outperforms other systems while having the same spectral
efficiency of each system.Comment: 4 pages, 4 figures, 4th International Conference on Electrical Energy
Systems (ICEES), Feb. 7-9, 2018, SSNCE, Chennai, TN, INDI
On the Performance of Millimeter Wave-based RF-FSO Multi-hop and Mesh Networks
This paper studies the performance of multi-hop and mesh networks composed of
millimeter wave (MMW)-based radio frequency (RF) and free-space optical (FSO)
links. The results are obtained in cases with and without hybrid automatic
repeat request (HARQ). Taking the MMW characteristics of the RF links into
account, we derive closed-form expressions for the networks' outage probability
and ergodic achievable rates. We also evaluate the effect of various parameters
such as power amplifiers efficiency, number of antennas as well as different
coherence times of the RF and the FSO links on the system performance. Finally,
we determine the minimum number of the transmit antennas in the RF link such
that the same rate is supported in the RF- and the FSO-based hops. The results
show the efficiency of the RF-FSO setups in different conditions. Moreover,
HARQ can effectively improve the outage probability/energy efficiency, and
compensate for the effect of hardware impairments in RF-FSO networks. For
common parameter settings of the RF-FSO dual-hop networks, outage probability
of 10^{-4} and code rate of 3 nats-per-channel-use, the implementation of HARQ
with a maximum of 2 and 3 retransmissions reduces the required power, compared
to cases with open-loop communication, by 13 and 17 dB, respectively.Comment: Submitted to IEEE Transactions on Wireless Communication
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