Refractivity estimations from an angle-of-arrival spectrum

This paper addresses the probability of atmospheric refractivity estimation by using field measurements at an array of radio receivers in terms of angle-of-arrival spectrum. Angle-of-arrival spectrum information is simulated by the ray optics model and refractivity is expressed in the presence of an ideal tri-linear profile. The estimation of the refractivity is organized as an optimization problem and a genetic Mgorithm is used to search for the optimal solution from various trial refractivity profiles. Theoretical analysis demonstrates the feasibility of this method to retrieve the refractivity parameters. Simulation results indicate that this approach has a fair anti-noise ability and its accuracy performance is mainly dependent on the antenna aperture size and its positions.

Angle-of-arrival fluctuations in moderate to strong turbulence

Based on the modified spectrum, the analytic expressions for the variance and normalized covariance of angleof-arrival （AOA） fluctuations are presented, which are applicable to the weak and strong regimes. The experimental data of AOA fluctuations validate the new derived expressions in weak and strong regimes. The results show that the receiving aperture D, outer scale and cell scale larger than the scattering disc S contribute significantly to the AOA fluctuations, and contributions from the small-scale turbulence are negligible. For the case of 4S/D 〈〈 1, the receiving aperture dominates low-pass filtering effects and the new displacement variances are in good agreement with the results from the old weak-fluctuation theory. For the case of 4S/D 〉〉 1, the scattering disc dominates the low-pass filtering effects and the new displacement variances depart from the results from the old weak-fluctuation theory.

Accurate Angle-of-Arrival Measurement Using Particle Swarm Optimization

As one of the major methods for location positioning, angle-of-arrival (AOA) estimation is a significant technology in radar, sonar, radio astronomy, and mobile communications. AOA measurements can be exploited to locate mobile units, enhance communication efficiency and network capacity, and support location-aided routing, dynamic network management, and many location-based services. In this paper, we propose an algorithm for AOA estimation in colored noise fields and harsh application scenarios. By modeling the unknown noise covariance as a linear combination of known weighting matrices, a maximum likelihood (ML) criterion is established, and a particle swarm optimization (PSO) paradigm is designed to optimize the cost function. Simulation results demonstrate that the paired estimator PSO-ML significantly outperforms other popular techniques and produces superior AOA estimates.

Adaptive microwave photonic angle-of-arrival estimation based on BiGRU-CNN [Invited]

An adaptive microwave photonic angle-of-arrival(AOA) estimation approach based on a convolutional neural network with a bidirectional gated recurrent unit(BiGRU-CNN) is proposed and demonstrated.Compared with the previously reported AOA estimation methods based on phase-to-power mapping,the proposed method is unnecessary to know the frequency of the signal under test(SUT) in advance.The envelope voltage correlation matrix is obtained from dual-drive Mach–Zehnder modulator(N-DDMZM,N > 2) optical interferometer arrays first,and then AOA estimations are performed on different frequency signals with the aid of BiGRU-CNN.A three-DDMZM-based experiment is carried out to assess the estimation performance of microwave signals at three different frequencies,and the mean absolute error is only 0.1545°.

On Time-of-Arrival Statistic of Gaussian Channel Model

A model of an angle-spread source, termed the “Gaussian Channel Model” is considered. The cumulative distribution function of the Time-of-Arrival of the multipath components is derived for an arbitrary angle spread. The simple approximate expressions for the Time-of-Arrival cumulative distribution function and probability density function are proposed. Numerical results obtained with the help of the derived expressions show the good coincidence with the experimental data and other known results.

A Novel Statistical AOA Model Pertinent to Indoor Geolocation

A novel statistical angle-of-arrival (AOA) model for indoor geolocation applications is presented. The modeling approach focuses on the arrivals of the multipath components with respect to the line-of-sight (LOS) path which is an important component especially when indoor geolocation applications are considered. The model is particularly important for indoor applications where AOA information could be utilized for tracking indirect paths to aid in precise ranging in harsh and dense multipath environments where LOS path might be blocked due to obstructions. The results have been obtained by a measurement calibrated ray-tracing (RT) tool.

Study on Turbulence Effects for Beam Propagation in Turbulent Atmosphere

Based on the theory for the turbulence and the Rytov method, the propagation formulas of the scintillation index and the mean square angle-of-arrival fluctuation for the beam propagation in atmospheric turbulence have been derived respectively. The propagation properties of the two turbulence effects have been investigated, and the effects of the characteristic parameters of turbulence and the beam parameters have been discussed. The results show that the variation of the two turbulence effects depends on the structure constant of the refractive index fluctuations Cn2, the inner scale of the turbulence l0, the waist width of source beam w0 and the wave length λ. Moreover, there are two parameters including Cn2 and l0 which show more significant effects in atmosphere. Consequently, a new method for determining the characteristics parameters of the turbulence by using the measurement of the scintillation index and the angle-of-arrival fluctuation has been proposed.

Closed form algorithm of double-satellite TDOA+AOA localization based on WGS-84 model

In this paper,we consider the double-satellite localization under the earth ellipsoid model of the Wideband Geodetic System(WGS-84)using the Time Difference of Arrival(TDOA)and the Angle-of-Arrival(AOA).Several closed-form solution algorithms via the pseudolinearization of the measurement equations are presented to efficiently estimate the location.These algorithms include the Weighted Least Squares(WLS),the Constrained Total Least Squares(CTLS),and the Taylor-Series Iteration(TSI).Performance comparison of the proposed methods with the Cramér-Rao Lower Bound(CRLB)in the simulation is shown to demonstrate that the proposed algorithms are feasible and have stable performance.

Toward the implementation of a universal angle-based optical indoor positioning system

There is an emerging market today for indoor positioning systems capable of working alongside global navigation satellite systems, such as the global positioning system, in indoor environments. Many systems have been proposed in the literature but all of them have fundamental flaws that hold them back from widescale implementation. We review angle-of-arrival （AOA） and angle-difference- of-arrival （ADOA） optical indoor positioning systems which have been proven to be robust, accurate, and easily implementable. We build an AOA/ADOA optical indoor positioning system out of a simple commercial high-speed camera and white light light emitting diodes （LEDs） which operate over a working area of 1 m3, and compare its performance to other indoor positioning methods. The AOA and ADOA systems achieve positioning with low errors of 1.2 and 3.7 cm, respectively.