112 research outputs found
On the Performance of Single- and Multi-carrier Modulation Schemes for Indoor Visible Light Communication Systems
In this paper, we investigate and compare the performance of single- and
multi-carrier modulation schemes for indoor visible light communication (VLC).
Particularly, the performances of single carrier frequency domain equalization
(SCFDE), orthogonal frequency division multiplexing (OFDM) and on-off keying
(OOK) with minimum mean square error equalization (MMSE) are analyzed in order
to mitigate the effect of multipath distortion of the indoor optical channel
where nonlinearity distortion of light emitting diode (LED) transfer function
is taken into account. Our results indicate that SCFDE system, in contrast to
OFDM system, does not suffer from high peak to average power ratio (PAPR) and
can outperform OFDM and OOK systems. We further investigate the impact of LED
bias point on the performance of OFDM systems and show that biasing LED with
the optimum value can significantly enhance the performance of the system.
Bit-interleaved coded modulation (BICM) is also considered for OFDM and SCFDE
systems to further compensate signal degradation due to inter-symbol
interference (ISI) and LED nonlinearity.Comment: 6 Pages, IEEE Globecom conference 201
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
Robust Timing Synchronization for AC-OFDM Based Optical Wireless Communications
Visible light communications (VLC) have recently attracted a growing interest
and can be a potential solution to realize indoor wireless communication with
high bandwidth capacity for RF-restricted environments such as airplanes and
hospitals. Optical based orthogonal frequency division multiplexing (OFDM)
systems have been proposed in the literature to combat multipath distortion and
intersymbol interference (ISI) caused by multipath signal propagation. In this
paper, we present a robust timing synchronization scheme suitable for
asymmetrically clipped (AC) OFDM based optical intensity modulated direct
detection (IM/DD) wireless systems. Our proposed method works perfectly for
ACO-OFDM, Pulse amplitude modulated discrete multitone (PAM-DMT) and discrete
Hartley transform (DHT) based optical OFDM systems. In contrast to existing
OFDM timing synchronization methods which are either not suitable for AC OFDM
techniques due to unipolar nature of output signal or perform poorly, our
proposed method is suitable for AC OFDM schemes and outperforms all other
available techniques. Both numerical and experimental results confirm the
accuracy of the proposed method. Our technique is also computationally
efficient as it requires very few computations as compared to conventional
methods in order to achieve good accuracy.Comment: Accepted for publication in IEEE ICNS 2015, 10 Pages, 7 fig
A realistic evaluation of indoor positioning systems based on Wi-Fi fingerprinting: The 2015 EvAAL–ETRI competition
Pre-print versionThis paper presents results from comparing different Wi-Fi fingerprinting algorithms on the same private dataset. The algorithms where realized by independent teams in the frame of the off-site track of the EvAAL-ETRI Indoor Localization Competition which was part of the Sixth International Conference on Indoor Positioning and Indoor Navigation (IPIN 2015). Competitors designed and validated their algorithms against the publicly available UJIIndoorLoc database which contains a huge reference- and validation data set. All competing systems were evaluated using the mean error in positioning, with penalties, using a private test dataset. The authors believe that this is the first work in which Wi-Fi fingerprinting algorithm results delivered by several independent and competing teams are fairly compared under the same evaluation conditions. The analysis also comprises a combined approach: Results indicate that the competing systems where complementary, since an ensemble that combines three competing methods reported the overall best results.We would like to thank Francesco Potortì, Paolo Barsocchi, Michele Girolami and Kyle O’Keefe for their valuable help in organizing and spread the EVAALETRI
competition and the off-site track. We would also like to thank the TPC
members Machaj Juraj, Christos Laoudias, Antoni Pérez-Navarro and Robert
Piché for their valuable comments, suggestions and reviews.
Parts of this work were funded in the frame of the Spanish Ministry of Economy
and Competitiveness through the “Metodologiías avanzadas para el diseño,
desarrollo, evaluación e integración de algoritmos de localización en interiores”
project (Proyectos I+D Excelencia, código TIN2015-70202-P) and the “Red de
Posicionamiento y Navegación en Interiores” network (Redes de Excelencia,
código TEC2015-71426- REDT). Parts of this work were funded in the frame of the German federal Ministry of Education and Research programme "FHprofUnt2013" under contract 03FH035PB3 (Project SPIRIT).info:eu-repo/semantics/acceptedVersio
Performance evaluation of distributed-antenna communications systems using beam-hopping
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