Haipeng Ding

Modeling of non-line-of-sight ultraviolet scattering channels for communication

A stochastic non-line-of-sight (NLOS) ultraviolet (UV) communication channel model is developed using a Monte Carlo simulation method based on photon tracing. The expected channel impulse response is obtained by computing photon arrival probabilities and associated propagation delay at the receiver. This method captures the multiple scattering effects of UV signal propagation in the atmosphere, and relaxes the assumptions of single scattering theory. The proposed model has a clear advantage in reliable prediction of NLOS path loss, as validated by outdoor experiments at small to medium elevation angles. A Gamma function is shown to agree well with the predicted impulse response, and this provides a simple means to determine the channel bandwidth. The developed model is employed to study the characteristics of NLOS UV scattering channels, including path loss and channel bandwidth, for a variety of scattering conditions, source wavelength, transmitter and receiver optical pointing geometries, and range.

Analytical performance study of solar blind non-line-of-sight ultraviolet short-range communication links

Motivated by recent advances in solid-state incoherent ultraviolet sources and solar blind detectors, we study communication link performance over a range of less than 1 km with a bit error rate (BER) below 10(-3) in solar blind non-line-of-sight situation. The widely adopted yet complex single scattering channel model is significantly simplified by means of a closed-form expression for tractable analysis. Path loss is given as a function of transceiver geometry as well as atmospheric scattering and attenuation and is compared with experimental data for model validation. The BER performance of a shot-noise-limited receiver under this channel model is demonstrated.

Path loss modeling and performance trade-off study for short-range non-line-of-sight ultraviolet communications.

We consider outdoor non-line-of-sight deep ultraviolet (UV) solar blind communications at ranges up to 100 m, with different transmitter and receiver geometries. We propose an empirical channel path loss model, and fit the model based on extensive measurements. We observe range-dependent power decay with a power exponent that varies from 0.4 to 2.4 with varying geometry. We compare with the single scattering model, and show that the single scattering assumption leads to a model that is not accurate for small apex angles. Our model is then used to study fundamental communication system performance trade-offs among transmitted optical power, range, link geometry, data rate, and bit error rate. Both weak and strong solar background radiation scenarios are considered to bound detection performance. These results provide guidelines to system design.

A path loss model for non-line-of-sight ultraviolet multiple scattering channels

An ultraviolet (UV) signal transmission undergoes rich scattering and strong absorption by atmospheric particulates. We develop a path loss model for a Non-Line-of-Sight (NLOS) link. The model is built upon probability theory governing random migration of photons in free space, undergoing scattering, in terms of angular direction and distance. The model analytically captures the contributions of different scattering orders. Thus it relaxes the assumptions of single scattering theory and provides more realistic results. This allows us to assess the importance of high-order scattering, such as in a thick atmosphere environment, where short range NLOS UV communication is enhanced by hazy or foggy weather. By simulation, it is shown that the model coincides with a previously developed Monte Carlo model. Additional numerical examples are presented to demonstrate the effects of link geometry and atmospheric conditions. The results indicate the inherent tradeoffs in beamwidth, pointing angles, range, absorption, and scattering and so are valuable for NLOS communication system design.

Turbulence modeling for non-line-of-sight ultraviolet scattering channels

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 performance.

Channel modelling and performance of non-line-of sight ultraviolet scattering communications

The solar-blind ultraviolet (UV) spectrum has useful properties for wireless communication and sensing. Strong atmospheric scattering in the UV spectrum enables non-line-of-sight (NLOS) communication. The authors present recent experimental and analytical results in NLOS UV channel modelling, including impulse response and path loss. The authors further study the NLOS UV link performance for short-range communication scenarios based on our theoretical modelling results. Relations between power limitation and channel bandwidth limitation are examined. Some link budget results are analysed for long-range communication links up to 5 km.

A parametric single scattering channel model for non-line-of-sight ultraviolet communications

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.

Non-line-of-sight ultraviolet communication channel characterization: modeling and validation

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.

Advanced Optical Wireless Communication Systems: Modeling and characterization of ultraviolet scattering communication channels

This thesis studies modeling of non-line-of-sight (NLOS) ultraviolet (UV) scattering channels and the corresponding communication link performance. The research focuses on the channel impulse response and path loss models based on extensive field measurements and theoretical characterization. In NLOS UV scattering environments, transmitted signals suffer from severe atmospheric attenuation and fading before arriving at a receiver, such as absorption, scattering, and turbulence. The thesis is devoted to development of analytical and experimental models to characterize NLOS UV communication channels.The author conducts comprehensive channel measurements for short communication ranges up to a few hundred meters and proposes an empirical path loss model. Meanwhile, an algorithm is developed to simulate the NLOS UV channel impulse response and path loss based on photons stochastic migration in the atmosphere. Effects of atmosphere conditions on single scattering and multiple scattering are investigated. An empirical curve-fitting model is developed to simplify the modeling work. Monte Carlo simulations provide good channel prediction for field tests in many scenarios. Then short range communication link performance is studied based on the theoretical models, and limitations by power and channel bandwidth are examined. Link budget results are also extended to long range communication links up to 5 kilometers. In this case, atmosphere turbulence becomes pronounced, and thus the intensity fluctuation at the receiver is mathematically modeled. These modeling results can provide insight into the performance tradeoffs and algorithm design for practical NLOS UV communication systems.

Correction to "Modeling of Non-Line-of-Sight Ultraviolet Scattering Channels for Communication" [Dec 09 1535-1544]

A stochastic non-line-of-sight (NLOS) ultraviolet (UV) communication channel model is developed using a Monte Carlo simulation method based on photon tracing. The expected channel impulse response is obtained by computing photon arrival probabilities and associated propagation delay at the receiver. This method captures the multiple scattering effects of UV signal propagation in the atmosphere, and relaxes the assumptions of single scattering theory. The proposed model has a clear advantage in reliable prediction of NLOS path loss, as validated by outdoor experiments at small to medium elevation angles. A Gamma function is shown to agree well with the predicted impulse response, and this provides a simple means to determine the channel bandwidth. The developed model is employed to study the characteristics of NLOS UV scattering channels, including path loss and channel bandwidth, for a variety of scattering conditions, source wavelength, transmitter and receiver optical pointing geometries, and range.