431 research outputs found
BER ANALYSIS OF MULTIPATH PPM AND MSK CARRIER INTENSITY MODULATION
In order to improve the bit-error-rate (BER) performance of free-space optical (FSO) communication systems employing binary phase-shift keying subcarrier intensity modulation (BPSK-SIM), an innovative hybrid modulation scheme called PPM-MSK-SIM is proposed, which is based on pulse position modulation (PPM) and minimum shift keying (MSK) subcarrier intensity modulation. Subsequently, the BER performance of PPM-MSK-SIM is studied in detail for an FSO system over log-normal turbulence channels with avalanche photodiode detection. The results of the numerical simulation show that PPM-MSK-SIM has the advantages of improving the BER performance compared with BPSK-SIM and PPM. This makes PPM-MSK-SIM a favorable candidate for the modulation technique in FSO communication systems. In this paper, we investigate the bit error rate (BER) performance of FSO links with spatial diversity over lognormal atmospheric turbulence fading channels, assuming both independent and correlated channels among transmitter/receiver apertures. Our analytical derivations build upon an approximation to the sum of correlated log-normal random variables. The derived BER expressions quantify the effect of spatial diversity and possible spatial correlations in a log-normal channel
BER Performance of IM/DD FSO System with OOK using APD Receiver
In this paper, the performance of intensity-modulated with direct detection (IM/DD) free space optical (FSO) system using the on-off keying (OOK) and avalanche photodiode (APD) receiver is observed. The gamma-gamma model is used to describe the effect of atmospheric turbulence since it provides good agreement in the wide range of atmospheric conditions. In addition, the same FSO system with equal gain combining applied at the reception is analyzed. After theoretical derivation of the expression for the bit error rate (BER), the numerical integration with previously specified relative calculation error is performed. Numerical results are presented and confirmed by Monte Carlo simulations. The effects of the FSO link and receiver parameters on the BER performance are discussed. The results illustrate that the optimal APD gain in the minimum BER sense depends considerably on the link distance, atmospheric turbulence strength and receiver temperature. In addition, the value of this optimal gain is slightly different in the case of spatial diversity application compared with single channel reception
On the Performance of MIMO FSO Communications over Double Generalized Gamma Fading Channels
A major performance degrading factor in free space optical communication
(FSO) systems is atmospheric turbulence. Spatial diversity techniques provide a
promising approach to mitigate turbulence-induced fading. In this paper, we
study the error rate performance of FSO links with spatial diversity over
atmospheric turbulence channels described by the Double Generalized Gamma
distribution which is a new generic statistical model covering all turbulence
conditions. We assume intensity modulation/direct detection with on-off keying
and present the BER performance of single-input multiple-output (SIMO),
multiple-input single-output (MISO) and multiple-input multiple-output (MIMO)
FSO systems over this new channel model.Comment: 6 Pages, 4 figure, IEEE ICC conference 201
Route diversity analyses for free-space optical wireless links within turbulent scenarios
Free-Space Optical (FSO) communications link performance is highly affected when propagating through the time-spatially variable turbulent environment. In order to improve signal reception, several mitigation techniques have been proposed and analytically investigated. This paper presents experimental results for the route diversity technique evaluations for a specific case when several diversity links intersects a common turbulent area and concurrently each passing regions with different turbulence flows
MIMO free-space optical communication employing subcarrier intensity modulation in atmospheric turbulence channels
In this paper, we analyse the error performance of transmitter/receiver array free-space optical (FSO) communication system employing binary phase shift keying (BPSK) subcarrier intensity modulation (SIM) in clear but turbulent atmospheric channel. Subcarrier modulation is employed to eliminate the need for adaptive threshold detector. Direct detection is employed at the receiver and each subcarrier is subsequently demodulated coherently. The effect of irradiance fading is mitigated with an array of lasers and photodetectors. The received signals are linearly combined using the optimal maximum ratio combining (MRC), the equal gain combining (EGC) and the selection combining (SelC). The bit error rate (BER) equations are derived considering additive white Gaussian noise and log normal intensity fluctuations. This work is part of the EU COST actions and EU projects
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
- …