Spatial Data Focusing: An Alternative to Beamforming for Geocasting Scenarios

Abstract

An alternative scenario is introduced in order to overcome antenna array's beamwidth limitations due to finite aperture size. The proposed approach aims to focus the transmitted data rather than the transmitted power. This scheme enables wireless broadcast of information to specific spatial locations, using fewer antenna elements compared to classical beamforming techniques. It is shown indeed with numerical examples that focusing the data is spatially more selective than focusing the power. In particular, we show that a linear 2-antenna array using spatial data focusing can exhibit similar beamwidths to a linear 7-antenna array using power focusing.

OFDM-Based Spatial Data Focusing for Wireless Physical Layer Geocasting in Multipath Channels

“…In contrast to beamforming and DM, spatial data focusing (SDF) attempts to address the geocasting issue directly, aiming for increased precision, reduced array size, and minimal complexity [24]. It abandons DM's and beamforming's power focusing approach, no longer basing signal distortion on array radiation pattern manipulation and the resulting spatial SNR distribution.…”

“…At the receiver, differences in propagation conditions between each data substream are exploited upon equalization to induce a location-dependent symbol distortion that restricts the spatial availability of the transmitted data, regardless of received power and SNR. Time-based spatial data focusing (T-SDF), introduced in [24] and [25], exploits the temporal dimension for signal orthogonality. Despite the considerable increase in spatial selectivity over beamforming in the angular domain, T-SDF fails to achieve range-based focusing.…”

“…Preliminary results on OFDM-SDF have been presented in [27]. However, just like [24] and [25], it is limited by omitting a multipath channel analysis and does not provide any performance guarantee in those scenarios. On the other hand, this paper presents an expanded OFDM-SDF scheme that allows for the dual exploitation of OFDM multi-frequency transmission for high-precision uncoupled range-angle-dependent and multipath robust geocasting.…”

OFDM-based Spatial Data Focusing for High Resolution 2-Dimensional Wireless Geocasting

“…In [8] and [9], SDF was first introduced by exploiting the temporal dimension to ensure signal orthogonality. This Time-based Spatial Data Focusing (T-SDF) implementation modulates the different data substreams onto time-shifted waveforms and transmits them sequentially in orthogonal time slots.…”

Spatial Data Focusing Using Time and IQ Resources for Wireless Geocasting

“…Preliminary work [10] has introduced the idea of using time resources to achieve SDF. However, additional degrees of freedom, leading to increased spatial selectivity, can be introduced by using quadrature amplitude modulated time signals, as discussed in this paper.…”