Conference Paper

DoA Estimation Using Reconfigurable Antennas in Millimiter-Wave Frequency 5G Systems

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... Direction-of-arrival (DOA) estimation of electromagnetic (EM) signals has attracted wide attention in many communication fields, such as radar [1,2], mobile networks [3] and sonar [4]. It is clear that DOA estimation is the basic and essential part in an array signal processing system. ...
Article
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Direction-of-arrival (DOA) estimation plays an important role in array signal processing, and the Estimating Signal Parameter via Rotational Invariance Techniques (ESPRIT) algorithm is one of the typical super resolution algorithms for direction finding in an electromagnetic vector-sensor (EMVS) array; however, existing ESPRIT algorithms treat the output of the EMVS array either as a “long vector”, which will inevitably lead to loss of the orthogonality of the signal components, or a quaternion matrix, which may result in some missing information. In this paper, we propose a novel ESPRIT algorithm based on Geometric Algebra (GA-ESPRIT) to estimate 2D-DOA with double parallel uniform linear arrays. The algorithm combines GA with the principle of ESPRIT, which models the multi-dimensional signals in a holistic way, and then the direction angles can be calculated by different GA matrix operations to keep the correlations among multiple components of the EMVS. Experimental results demonstrate that the proposed GA-ESPRIT algorithm is robust to model errors and achieves less time complexity and smaller memory requirements.
Preprint
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Apart from the conventional parameters (such as signal-to-noise ratio, array geometry and size, sample size), several other factors (e.g. alignment of the antenna elements, polarization parameters) influence the performance of direction of arrival (DOA) estimating algorithms. When all the antenna elements are identically aligned, the polarization parameters do not affect the steering vectors, which is the underlying assumption of all the conventional DOA algorithms. Unfortunately, in this case, for a given set of DOA angles there exists a range of polarization parameters which could result in a very low signal-to-noise ratio (SNR) across all the antenna elements in the array. To avoid this type of catastrophic event, different antenna element needs to be aligned differently. However, this fact will make almost all commonly used DOA estimation algorithms non-operable, since the steering vectors are contaminated by the polarization parameters. To the best of our knowledge, no work in the literature addresses this issue even for a single user environment. In this paper, that line of inquiry is pursued. We consider a circular array with the minimum number of antenna elements and propose an antenna alignment scheme to ensure that at any given point no more than one element will suffer from significantly low SNR due to the contribution of polarization. A low complexity algorithm that estimates the DOA angles in a closed-form manner is developed. We treat MUSIC as the baseline algorithm and demonstrate how it can reliably operate in all possible DOA and polarization environments. Finally, a thorough performance and complexity analysis are illustrated for the above two algorithms.
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This paper focuses on direction of arrival (DoA) estimation using adaptive arrays that consist of radiation pattern reconfigurable antenna (RPRA) elements for 2D direction finding (i.e., azimuth and elevation DoA estimation). In particular, uniform circular arrays (UCAs) are explored that use RPRA elements with two different elevation radiation pattern states to achieve unambiguous estimates over all possible incident angles. Theoretical cardioid-type directional patterns are investigated to determine the pattern states that minimize overall DoA estimation error, and the performance of 3-, 4-, and 5-element RPRA UCAs is compared with baseline theoretical arrays composed of isotropic elements. The results demonstrate that RPRA UCAs with optimized cardioid patterns can achieve similar accuracy to the baseline arrays, but with fewer antennas/front-ends. For example, a 4-element RPRA UCA can achieve approximately the same root mean square error (RMSE) as a 6-element uniform spherical array composed of isotropic elements. Furthermore, unambiguous estimates can be achieved over all incident angles with electrically large UCA radii using optimized RPRA elements, which can further improve accuracy and increase bandwidth. To demonstrate the feasibility of the technique, a practical RPRA was designed at 6 GHz with a pattern that approximates the optimized cardioid, and the performance meets or exceeds the theoretical pattern performance for RMSEs less than 3°.
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In this paper, we have introduced low-profile electronically steerable parasitic array radiator (ESPAR) antenna that can successfully be used to estimate direction-of-arrival (DoA) of incoming signals in wireless sensor network (WSN) applications, in which the height of the complete antenna has to be low. The proposed antenna is over 3 times lower than high-profile ESPAR antenna designs currently available in the literature for DoA estimation, can provide 8 unique main beam directions and relies on simplified beam steering, which makes it applicable to simple and inexpensive WSN nodes. Measurements using our fabricated ESPAR antenna prototype indicate that relying solely on received signal strength (RSS) values recorded at the antenna output port it is possible to achieve accurate DoA estimation results with error levels similar to those available for high-profile ESPAR antennas relying on the similar energy-efficient simplified beam steering concept and having 12 unique main beam directions. As a consequence, the overall time required for DoA estimation using the proposed antenna can be reduced by 33%.
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In this letter, a new single-anchor indoor localization concept employing electronically steerable parasitic array radiator (ESPAR) antenna has been proposed. The new concept uses a simple fingerprinting algorithm adopted to work with directional main beam and narrow minimum radiation patterns of ESPAR antenna that scans 360 area around the base station, while the signal strength received from a mobile terminal is being recorded for each configuration. The letter describes the antenna design and necessary fingerprinting algorithm expansion and shows measurements of the proof-of-concept prototype performed within the experimental setup. Localization results obtained from indoor measurements indicate that the proposed concept can provide better results than the similar approach based on a switched-beam antenna introduced by Giorgetti et al. (IEEE Commun. Lett., vol. 13, no. 1, pp. 58-60, Jan. 2009).
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This paper provides a review of antennas applied for indoor positioning or localization systems. The desired requirements of those antennas when integrated in anchor nodes (reference nodes) are discussed, according to different localization techniques and their performance. The described antennas will be subdivided into the following sections according to the nature of measurements: received signal strength (RSS), time of flight (ToF), and direction of arrival (DoA). This paper intends to provide a useful guide for antenna designers who are interested in developing suitable antennas for indoor localization systems.
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In this letter, it has been shown how an algorithm, which employs received signal strength (RSS) values in order to estimate direction-of-arrival (DoA) of impinging signals in wireless sensor network (WSN) nodes equipped with electronically steerable parasitic array radiator (ESPAR) antennas, can easily be improved by applying an interpolation algorithm to radiation patterns recorded in the calibration phase of the DoA estimation process. The proposed method allows one to measure ESPAR antenna's radiation patterns during the initial calibration phase with much coarser, than 1°, angular resolution, while the overall DoA estimation accuracy can be kept at the similar level. Measurements using a fabricated ESPAR antenna have indicated that anechoic chamber calibration procedure of WSN nodes equipped with such antennas can be done almost 50% faster, which in consequence will reduce system deployment costs in practical WSN applications where a number of WSN nodes can easily reach hundreds.
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The knowledge of the directions of arrival (DOAs) of the signals impinging on an antenna receiver enables the use of adaptive control algorithm suitable for limiting the effects of interferences and increasing the gain towards the desired signals in order to improve the performances of wireless communication systems. In this paper, an innovative multi-resolution approach for the real-time DOA estimation of multiple signals impinging on a planar array is presented. The method is based on a support vector classifier and it exploits a multi-scaling procedure to enhance the angular resolution of the detection process in the regions of incidence of the incoming waves. The data acquired from the array sensors are iteratively processed with a support vector machine (SVM) customized to the problem at hand. The final result is the definition of a map of the probability that a signal impinges on the antenna from a fixed angular direction. Selected numerical results, concerned with both single and multiple signals, are provided to assess potentialities and current limitations of the proposed approach.
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An approach for estimating direction-of-arrival (DoA) based on power output cross-correlation and antenna pattern diversity is proposed for a reactively steerable antenna. An "estimator condition" is proposed, from which the most appropriate pattern shape is derived. Computer simulations with directive beam patterns obtained from an electronically steerable parasitic array radiator antenna model are conducted to illustrate the theory and to inspect the method performance with respect to the "estimator condition". The simulation results confirm that a good estimation can be expected when suitable directive patterns are chosen. In addition, to verify performance, experiments on estimating DoA are conducted in an anechoic chamber for several angles of arrival and different scenarios of antenna adjustable reactance values. The results show that the proposed method can provide high-precision DoA estimation.
Advances in Direction-of-Arrival Estimation
  • S Chandran