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

Abstract

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

“…While the proposed scheme remains fully functional in the latter scenario, its geocastwidth differs from the theoretical values by a factor of 2 approximately, while the former succeeds in approximating Geocast-width and outlier-inclusive geocast-width (normalized) for decreasing Rice factor K. Shading shows uncertainty (±2∆d sim , ±2∆θ sim ) due to discretized simulation grid. the theoretical values more closely, as anticipated in Section II-E. Additionally, in contrast to [25] and [27], that suffer from noise-caused narrowing and undershoot the theoretical geocast-widths, the proposed scheme remains above and in better approximation of these reference values. The discontinuous decrease of the radial geocast-width in Fig.…”

“…9 for a Rice factor of K = 2.5 dB. At the investigated Rice factors, the SDF techniques in [25] and [27] are unable to create any low BER region, making a formal comparison impossible, however emphasizing the improved robustness provided by the proposed scheme. Similarly, [18] does not consider a multipath scenario.…”

“…5 and 6 analyze, respectively, the radial and angular precision of the proposed OFDM-SDF scheme in free space, as a function of the number of antennas N . These results are compared to the theoretical SDF geocast-widths (25a) and (25b), random-subcarrier-selection-based OFDM directional modulation (RSCS-OFDM-DM) [18], and, where applicable, preliminary SDF implementations [25] and [27]. First, it is shown that the proposed semi-inverted Gray code symbol mapping (s-i Gr.)…”

“…Only the phase shift due to LOS propagation in (3) has a tractable positional dependency that can be leveraged for spatial focusing. However, this behavior is disturbed by the multipath character of the channels H n [q], prohibiting the direct exploitation of the LOS phase shift as in [25] and [27]. As a result, a twofold channel equalization is proposed for OFDM-SDF.…”

“…Similarly to [26], OFDM-SDF range focusing thus remains time-invariant. 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.…”