Recently ultraviolet (UV) scattering channels have received renewed interest for non-line-of-sight (NLOS)
communication. Monte Carlo simulations and field experiments have yielded valuable results to predict channel path
loss and impulse response at relatively short ranges, critical for communication link analysis. However, as
communication range increases, the effect of turbulence becomes pronounced and inevitably induces additional
impairments to system performance. This paper suggests a turbulence modeling method for NLOS UV channels
incorporating the effects of scattering and absorption. The modeling results can be applied to study communication
We report some latest experimental results on non-line-of-sight (NLOS) ultraviolet (UV) scattering communication
channel characteristics. Those results include both channel path losses and impulse responses, critical for UV
communication system design. Path losses were measured using a UV light-emitting-diodes (LEDs) based test-bed,
while impulse responses by a UV laser based test-bed. The effects of transmitter and receiver pointing angles, separation
distance and transmit beam angle are demonstrated.
The performance of non-line-of-sight (NLOS) ultraviolet (UV) communication receiver has been analyzed under an
assumption of no inter-symbol interference (ISI) in the literature. However, ISI may become detrimental when the data
rate increases in a multiple scattering UV channel. We consider relatively high data rate and develop a performance
model with the ISI effect due to channel delay spread. Both analytical derivation and newly reported experimental
results on impulse response and path loss are introduced and incorporated. The results reveal the close connection
between bit error rate (BER) performance and data rate in different transmit/receive geometry, and the power penalty
compared with that of an ISI-free system.
Fundamental characteristics of non-directed line-of-sight links for indoor wireless optical communication systems have
been widely discussed. In this paper, we present experimental visible light channel characterization results, including
impulse response and path loss, and further predict the fundamental communication system performance trade-offs
among transmitted optical power, range, data rate and bit-error rate. These results provide guidelines to system design.
Non-line-of-sight (NLOS) ultraviolet (UV) scattering channel impulse response in the deep UV solar-blind spectrum
band is investigated. Taking into account a light source power angular distribution and applying a photon tracing
technique, Monte Carlo simulation is performed to obtain the channel impulse response and associated path loss. Some
comparisons are carried out with an existing single scattering channel model, as well as field measurements in both the
impulse response model and path loss, to demonstrate modeling accuracy. The importance of considering multiple
versus single-scattering in the analysis is shown. The results provide guidelines for study of limitations to data rate and
communication range in NLOS UV communications.
Visible light communication in conjunction with solid state lighting has become an emerging area of interest to achieve
lighting and wireless communication simultaneously in an indoor environment. It is anticipated to be a low cost
supplement to existing wireless communication technologies. Most existing work has primarily focused on a
unidirectional downlink using visible light spectra. The appropriate choice of an uplink to achieve bidirectional
communication is a big challenge. In this paper, candidate options of the uplink are compared in terms of device
performance, light safety, background interference, and path loss. In visible light communication, white light emitting
diodes as optical transmitters are also characterized in terms of impulse response and electrical spectrum. A digital preequalization
idea to increase their bandwidth is proposed. Performance of the downlink visible light communication
system is also experimentally studied in order to demonstrate the feasibility of the proposed design.
Rich atmospheric scattering in the ultraviolet (UV) enables non-line-of sight (NLOS) communications, opening a new
optical paradigm. In this paper, we incorporate an experimentally validated NLOS channel path loss model and
quantitatively predict the performance of a combination of modulation and coding techniques. Our study includes OOK,
PPM, MPPM, repetition coding and trellis coding. We consider both Poisson and Gaussian noise assumptions,
appropriate for different operating regimes, with a focus on achievable range as a critical parameter in NLOS operation.
Recent advances in ultraviolet (UV) semiconductor sources and detectors have inspired significant research activities in
short-range UV communications, particularly in non-line-of-sight (NLOS) channel conditions due to atmospheric
scattering. However, a scattering channel involves complex interactions of photons with atmospheric particles. This
paper presents a parametric channel model that greatly simplifies channel characterization. For a short range link, single
scattering may dominate in some scenarios. We model the channel impulse response with a gamma function as well as
its variants to better fit the prediction by a widely adopted analytical single scattering model. Normalized mean square
fitting error is adopted to validate our parametric model. Path losses and channel bandwidths are subsequently studied
under different geometrical link configurations.
Motivated by rapid advances in solar blind ultraviolet (UV) light emitting diodes (LEDs), filters and photomultiplier
tubes (PMTs), together with unique UV atmospheric propagation characteristics, a non-line-of-sight (NLOS) UV
communication test-bed has been recently built and utilized for extensive experimental evaluation of performance of
NLOS UV links in outdoor environments. Towards this end, key link components are first characterized and their
limitations are identified. The tradeoffs among communication range, received number of photons, and bit-error-rate are
revealed via field measurement results. Wavelength diversity is achieved by utilizing combinations of sources and
detectors centered at different wavelengths in the solar blind band. It is demonstrated that signals can be reliably
transmitted to their destinations of dozens of meters away through an NLOS channel. Although all reported results in
this paper are based on open field experiments, it is found that reflections from surrounding objects such as trees and
buildings can enhance the received signal strength, up to an order of magnitude increase in the received number of
photons in some cases, thus significantly improving link performance.