Accurate PPCC-Based DoA Estimation Using Multiple Calibration Planes for WSN Nodes Equipped with ESPAR Antennas

Abstract

In this paper, we have introduced a new directionof-arrival (DoA) estimation method, which relies on received signal strength (RSS) values measured at the output port of electronically steerable parasitic array radiator (ESPAR) antenna and uses the power pattern cross-correlation (PPCC) estimator. In the method, we have successfully incorporated measurements of ESPAR antenna's radiation patterns performed at multiple calibration planes within the PPCC estimator in a way easily implementable in wireless sensor network (WSN) nodes equipped with ESPAR antennas. Performed anechoic chamber measurements of our ESPAR antenna prototype indicate that the proposed approach provides much lower DoA estimation errors in a wide span of incoming signal elevation angles than other methods currently available in the literature, which makes the concept applicable in practical WSN deployment scenarios.

Efficient RSS-Based DoA Estimation for ESPAR Antennas Using Multiplane SDR Calibration Approach

“…By choosing the estimator providing the biggest value it was possible to increase the overall PPCC-based DoA estimation performance for arbitrary elevation angles. Because such an approach provides acceptable results only when a signal impinging the antenna comes from elevation angles between = 90° and = 50°, further extension has been proposed involving a new PPCC estimator involving multiplane calibration [7], so the number of calibration planes can easily be extended to provide acceptable accuracy level. As result presented in [7] indicate, by increasing the number of calibration planes it is possible to increase the overall DoA estimation accuracy in a wide span of elevation angles.…”

“…Because such an approach provides acceptable results only when a signal impinging the antenna comes from elevation angles between = 90° and = 50°, further extension has been proposed involving a new PPCC estimator involving multiplane calibration [7], so the number of calibration planes can easily be extended to provide acceptable accuracy level. As result presented in [7] indicate, by increasing the number of calibration planes it is possible to increase the overall DoA estimation accuracy in a wide span of elevation angles. One has to note, however, that every additional calibration plane added to the PPCC estimator increases also the associated calculation time required for DoA estimation.…”

“…For multiplane calibration approach with = 9 calibration planes set up at { 1 = 10°, 2 = 20°, … , 9 = 90°} as proposed in [7], the overall root-mean-square (RMS) error calculated from all 1224 error values equals 19.20°. This is caused mainly by considerable errors at = 15°, not visible when coarse angular step is used for testing as in [7].…”

“…For multiplane calibration approach with = 9 calibration planes set up at { 1 = 10°, 2 = 20°, … , 9 = 90°} as proposed in [7], the overall root-mean-square (RMS) error calculated from all 1224 error values equals 19.20°. This is caused mainly by considerable errors at = 15°, not visible when coarse angular step is used for testing as in [7]. By applying the proposed iterative approach, we first had set up only two calibration planes, namely { 1 = 10°, 2 = 90°}, which resulted in the total RMS error equal 59.66° and with the highest RMS error value at the vertical angle = 40°.…”

“…By inserting additional calibration plane ( 4 = 15°) the overall RMS error dropped to 1.65°, which is a value acceptable in most of DoA applications. Therefore, with the proposed multiplane SDR-based approach, it is possible to obtain efficient PPCC-based DoA estimation that provides acceptable result using only = 4 calibration planes that are now placed in more optimal manner than it was proposed in [7].…”