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A novel unified frequency diverse array (FDA) and spatial data focusing (SDF) approach is proposed to simultaneously overcome time-variance and precision constraints of conventional FDA in geocasting, i.e. spatially confined broadcasting, scenarios. This paper describes a free space FDA-based SDF (FDA-SDF) system model for 2-dimensional range-angle-based focusing, including a generalized multi-purpose baseband approach for time-invariant FDA, complemented by SDF processing for improved spatial focusing precision and reduced array size. Comprehensive analytical derivations – general for any frequency offset configuration – describe the geographical FDA-SDF properties and design rules, such as geocast delivery zone steering, location, uniqueness, and size. Simulations of the proposed scheme validate theoretical derivations and demonstrate FDA-SDF’s superior spatial precision and minimal design complexity. In particular, using novel alternating logarithmic frequency offsets, a 3-antenna FDA-SDF setup is shown to match the radial and azimuthal precision of its beamforming-based FDA counterpart using, respectively, 64 and 24 antennas., SCOPUS: ar.j, info:eu-repo/semantics/published

This thesis investigates spatial data focusing (SDF) as a means of performing wireless physical-layer geocasting, i.e. location-based multicasting or geographically-confined broadcasting. This novel approach can aid in providing location-based services and messaging to large groups of mobile devices that exist in emerging internet-of-things frameworks for smart cities, industries, healthcare, etc. providing users with information that is related or contextualized to their geographical location. It addresses and avoids privacy concerns that exist in conventional location-based services, where users are required to disclose their location. In addition, it overcomes node self-localization requirements and the challenging balance between overhead, scalability, and delivery rate that exist in network-layer geocast routing algorithms. Most importantly, it succeeds in increasing precision, reducing array size, and minimizing complexity -- the most crucial conditions in making physical-layer geocasting an attractive scheme -- compared to conventional beamforming-based power focusing approaches. Within the SDF framework, it additionally addresses two fundamental shortcomings. That is, (i) a limitation to focusing in the angular domain only or, equivalently, the inability for range-domain focusing and (ii) a severe sensitivity to multipath propagation that jeopardizes correct operation outside hypothetical free space channels. They are overcome by designing two novel SDF architectures that exploit multi-frequency transmission resources in an orthogonal frequency-division multiplexing (OFDM) and frequency diverse array (FDA) framework. Additionally, an experimental proof-of-concept SDF architecture is developed that demonstrates its practical achievability as a novel geocasting technique., Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

This paper presents the first-ever experimental validation of both spatial data focusing (SDF) and time-invariant frequency diverse array (FDA) range-angle-based focusing, in both free space and multipath environments. In particular, a hybrid FDA-based SDF (FDA-SDF) approach is considered for spatially confined broadcasting, i.e. geocasting. First, the base FDA-SDF free space system model is reviewed. Next, a novel OFDM-based FDA-SDF system model is introduced to ensure robust operation in multipath channels. The schemes are validated, respectively, in an anechoic chamber and outdoor measurement setup using software defined radios. Results confirm FDA-SDF's anticipated supreme spatial precision: a 0.9 m × 4.0° range-azimuth geocast delivery zone is generated by a 4-antenna array in free space. Additionally, they illustrate that OFDM-based FDA-SDF provides all necessary performance improvements for practical operation in outdoor multipath environments. Most notably, FDA-SDF is shown to overcome the time-variance flaw of conventional FDA., info:eu-repo/semantics/published

info:eu-repo/semantics/nonPublished

A unified frequency diverse array (FDA) and spatialdata focusing (SDF) system, or FDA-SDF, is proposed as a novelapproach to perform spatially confined broadcasting of information, i.e. geocasting. It is shown that SDF processing exploitsFDA range-angle-dependency more effectively than conventionalpower focusing implementations, resulting in improved spatialfocusing precision and reduced array size. Additionally, thetime-variance flaw in conventional FDAs is addressed and mitigated by introducing a generalized baseband FDA model. Thispaper describes the FDA-SDF system model in free space, including dedicated SDF precoding, beamsteering, and equalization,exploiting FDA multi-frequency transmission for 2-dimensionalrange-angle-based time-invariant geocasting. Simulations of theFDA-SDF system illustrate compatibility with conventional FDAfrequency offset schemes and highlight degrees of freedom forgeocast delivery zone manipulation. Finally, FDA-SDF’s superiorspatial precision is demonstrated: a 3-antenna FDA-SDF setupmatches the radial and angular precision of a conventional FDAusing, respectively, 13 and 23 antennas., info:eu-repo/semantics/published

OFDM-based spatial data focusing (OFDM-SDF) is proposed as a novel means of performing wireless physical layer geocasting, i.e. spatially confined broadcasting. It is shown that this approach overcomes beamforming and directional modulation (DM) limitations by exhibiting higher spatial precision with a reduced number of antennas and offering uncoupled range-angle-dependent focusing. This paper describes the OFDM-SDF system model for multipath channels, including multipath robust equalization, design rules for steering phases and sidelobe mitigation, analytical geocast delivery zone derivation, and optimized symbol mapping. Using density-based clustering of the spatial bit error rate distribution, a procedure for identifying a practical geocast delivery zone and evaluating its precision and connectivity is proposed. OFDM-SDF’s performance and multipath robustness are evaluated through Rice channel simulations as a function of the Rice factor. In particular, it is shown that a 2-antenna OFDM-SDF array matches the radial and angular precision of, respectively, a 6 and 12-antenna DM array in recent literature, while robustness is ensured for 5G small cell channels., SCOPUS: ar.j, info:eu-repo/semantics/published

An OFDM-based Spatial Data Focusing (OFDM-SDF) approach is proposed as an improvement over standard Time-based Spatial Data Focusing (T-SDF) as a means of wirelessly broadcasting information towards confined spatial locations, i.e. wireless geocasting. It is shown that this approach allows for 2-dimensional focusing, hence leading to far greater flexibility in terms of geocasting scenarios compared to T-SDF and beamforming, both limited to angular focusing only. This increased flexibility does not come at any trade-off costs in terms of spatial selectivity, and hence, just as T-SDF, OFDM-SDF is shown to establish a considerable increase in attainable geocasting accuracy when compared to traditional power focusing methods. This paper describes the free space OFDM-SDF system model for uniform linear antenna arrays, including beamsteering and sidelobe mitigation techniques. Based on simulations, the performance of OFDM-SDF is compared to both T-SDF, as well as classical beamforming., info:eu-repo/semantics/published

Wireless geocasting, i.e. wirelessly broadcasting information towards confined spatial locations, requires spatial focusing capabilities from base stations. By focusing both in the angular and radial domains, OFDM-based Spatial Data Focusing (OFDM-SDF) allows for 2-dimensional geocasting, providing a great increase in flexibility for geocasting compared to T-SDF and beamforming, both limited to angular focusing only. However, just as T-SDF, OFDM-SDF suffers from a strong sensitivity to mulipaths, harshly decreasing its performance in scenarios other than free space. This TD re-evaluates the free space OFDM-SDF system model by exploring the additional challenges when applying SDF in multipath channels and proposes improvements to the OFDM-SDF scheme to increase its robustness in non free space environments., info:eu-repo/semantics/published

info:eu-repo/semantics/published

Spatial Data Focusing (SDF) is introduced as a novel technique that allows wireless broadcasting of information towards specific spatial locations only. It is shown that this approach allows one to target geographic areas more accurately than traditional power focusing methods, using limited equipment at the transmitter. This paper describes the SDF system model for linear arrays, based on simple modulation techniques and transmitter architectures, both in pure line-of-sight and multipath environments. In particular, the robustness of the scheme is proven for over-the-ground propagation environments. Theoretic results are illustrated by simulations, confirming the increased spatial selectivity of SDF and showing the influence of various design parameters of the scheme on the resulting beam., info:eu-repo/semantics/published