More Like this

1. Channel Charting: Model-Based Approaches

   Aly, Amr and (June 2023, Proc. 2023 IEEE International Conference on Communications (ICC))

   We present new ways of producing a channel chart employing model-based approaches. We estimate the angle of arrival θ and the distance between the base station and the user equipment ρ by employing our algorithms, inverse of the root sum squares of channel coefficients (ISQ) algorithm, linear regression (LR) algorithm, and the MUSIC/MUSIC (MM) algorithm. We compare these methods with the channel charting algorithms principal component analysis (PCA), Sammon’s method (SM), and autoencoder (AE) from [1]. We show that ISQ, LR, and MM outperform all three in performance. ISQ and LR have similar performance with ISQ having less complexity than LR. The performance of MM is better than ISQ and LR but it is more complex. Finally, we introduce the rotate-and-sum (RS) algorithm which has about the same performance as the MM algorithm but is less complex due to the avoidance of the eigenvector and eigenvalue analysis and a potential register transfer logic (RTL) implementation. 

   more » « less
2. Estimation of Cellular Wireless User Coordinates via Channel Charting and MUSIC

   https://doi.org/10.1109/ICNC57223.2023.10074200  

   Aly, Amr; Ayanoglu, Ender (February 2023, Proc. 2023 International Conference on Computing, Networking and Communications (ICNC))

   We present a new way of producing a channel chart for cellular wireless communications in polar coordinates. We estimate the angle of arrival θ and the distance between the base station and the user equipment ρ using the MUSIC algorithm and inverse of the root sum squares of channel coefficients (ISQ) or linear regression (LR). We compare this method with the channel charting algorithms principal component analysis (PCA), Samson’s method (SM), and autoencoder (AE). We show that ISQ and LR outperform all three in both performance and complexity. The performance of LR and ISQ are close, with ISQ having less complexity. 

   more » « less
3. Alternative Channel Charting Techniques in Cellular Wireless Communications

   https://doi.org/10.1109/IEEECONF60004.2024.10943094  

   Jiang, Yonghong; Ayanoglu, Ender (October 2024, IEEE)

   We investigate the use of conventional angle of arrival (AoA) algorithms the Bartlett’s algorithm, the Minimum Variance Distortion Response (MVDR or Capon) algorithm, and the Minimum Norm algorithm for estimating the AoA theta together with our previously introduced algorithms linear regression (LR), inverse of the root sum squares of channel coefficients (ISQ), as well as a novel use of the MUSIC algorithm for estimating the distance from the base station, rho in the context of channel charting. We carry out evaluations in terms of the visual quality of the channel charts, the dimensionality reduction performance measures trustworthiness (TW) and connectivity (CT), as well as the execution time of the algorithms. We find that although the Bartlett’s algorithm, MVDR, and Minimum Norm algorithms have sufficiently close performance to techniques we studied earlier, the Minimum Norm algorithm has significantly higher computational complexity than the other two. Previously, we found that the use of the MUSIC algorithm for estimation of both theta and rho has a very high performance. In this paper, we investigated and quantified the performance of the Bartlett algorithm in its use for estimating both and , similar to the our previously introduced technique of using MUSIC for estimating both. 

   more » « less
4. Direction Finding and Likelihood Ratio Detection for Oceanographic HF Radars

   https://doi.org/10.1175/JTECH-D-21-0110.1  

   Emery, Brian; Kirincich, Anthony; Washburn, Libe (February 2022, Journal of Atmospheric and Oceanic Technology)

   Abstract Previous work with simulations of oceanographic high-frequency (HF) radars has identified possible improvements when using maximum likelihood estimation (MLE) for direction of arrival; however, methods for determining the number of emitters (here defined as spatially distinct patches of the ocean surface) have not realized these improvements. Here we describe and evaluate the use of the likelihood ratio (LR) for emitter detection, demonstrating its application to oceanographic HF radar data. The combined detection–estimation methods MLE-LR are compared with multiple signal classification method (MUSIC) and MUSIC parameters for SeaSonde HF radars, along with a method developed for 8-channel systems known as MUSIC-Highest. Results show that the use of MLE-LR produces similar accuracy, in terms of the RMS difference and correlation coefficients squared, as previous methods. We demonstrate that improved accuracy can be obtained for both methods, at the cost of fewer velocity observations and decreased spatial coverage. For SeaSondes, accuracy improvements are obtained with less commonly used parameter sets. The MLE-LR is shown to be able to resolve simultaneous closely spaced emitters, which has the potential to improve observations obtained by HF radars operating in complex current environments. Significance Statement We identify and test a method based on the likelihood ratio (LR) for determining the number of signal sources in observations subject to direction finding with maximum likelihood estimation (MLE). Direction-finding methods are used in broad-ranging applications that include radar, sonar, and wireless communication. Previous work suggests accuracy improvements when using MLE, but suitable methods for determining the number of simultaneous signal sources are not well known. Our work shows that the LR, when combined with MLE, performs at least as well as alternative methods when applied to oceanographic high-frequency (HF) radars. In some situations, MLE and LR obtain superior resolution, where resolution is defined as the ability to distinguish closely spaced signal sources. 

   more » « less
5. Experimental Results of Novel DoA Estimation Algorithms for Compact Reconfigurable Antennas

   https://doi.org/10.1155/2017/1613638  

   Paaso, Henna; Hakkarainen, Aki; Gulati, Nikhil; Patron, Damiano; Dandekar, Kapil R.; Valkama, Mikko; Mämmelä, Aarne (January 2017, International Journal of Antennas and Propagation)

   null (Ed.)

   Reconfigurable antenna systems have gained much attention for potential use in the next generation wireless systems. However, conventional direction-of-arrival (DoA) estimation algorithms for antenna arrays cannot be used directly in reconfigurable antennas due to different design of the antennas. In this paper, we present an adjacent pattern power ratio (APPR) algorithm for two-port composite right/left-handed (CRLH) reconfigurable leaky-wave antennas (LWAs). Additionally, we compare the performances of the APPR algorithm and LWA-based MUSIC algorithms. We study how the computational complexity and the performance of the algorithms depend on number of selected radiation patterns. In addition, we evaluate the performance of the APPR and MUSIC algorithms with numerical simulations as well as with real world indoor measurements having both line-of-sight and non-line-of-sight components. Our performance evaluations show that the DoA estimates are in a considerably good agreement with the real DoAs, especially with the APPR algorithm. In summary, the APPR and MUSIC algorithms for DoA estimation along with the planar and compact LWA layout can be a valuable solution to enhance the performance of the wireless communication in the next generation systems. 

   more » « less