Point cloud semantic segmentation is fundamentally challenged by spatial sparsity, non-uniform sampling, and the intricate coupling between local geometric structures and global semantic context. Existing approaches often fail to simultaneously preserve fine-grained geometry, maintain cross-scale contextual coherence, and suppress noise in structurally complex regions. To address these limitations, we propose a novel feature enhancement module, termed the Foveated Selective Geometry Aggregator (FSGA), which explicitly models local–global dependencies through a hierarchical perceptual process inspired by human visual cognition, including foveation, encoding, association, and inhibition. FSGA enhances geometric–semantic interaction while selectively emphasizing informative regions and suppressing ambiguous responses. Designed as a plug-and-play component, FSGA can be seamlessly integrated into a wide range of mainstream point cloud segmentation networks with negligible architectural modification. Extensive experiments on multiple standard benchmarks demonstrate that FSGA consistently improves segmentation accuracy with minimal computational overhead.

The minimalist and ultra-low-power natures of ambient backscatter communications (AmBC) make it a compelling wireless paradigm for Internet of Things (IoT), which in turn puts AmBC at great risk of being monitored. Recently, covert backscatter systems have been explored to secure transmission without detection, but they mainly introduce artificial noise and beamforming, consuming additional energy. In this paper, we propose a spatial modulation (SM)-enabled multi-antenna covert AmBC system that guarantees covertness and raises the covert capacity without requiring additional energy consumption. Specifically, the multiple-antenna backscatter tag transmits covert information by adopting SM, while its remaining antennas superimpose overt messages to shelter the covert transmission. We derive the closed-form expression of the minimum detection error probability (DEP) to capture the covertness, that represents the worst-case for the tag. Furthermore, we formulate a covert capacity maximization problem by optimizing the power reflection coefficient under the constraints of the covertness requirement. By exploiting the objective function's monotonic properties and the constraints, we derive the optimal power reflection coefficient and the corresponding covert capacity. Due to the target expression is very complex and lacks a closed-form solution, we introduce a Taylor expansion to simplify it. Finally, numerical results demonstrate the performance and effectiveness of the proposed multi-antenna covert backscatter communication system. As a result, it shown that the covert capacity can be significantly improved compared with the benchmark scheme.

Recently, the coherent optic wireless communication (OWC) has received extensive attention due to its superiority over traditional intensity modulated direct detection (IMDD) systems. Yet, the Doppler effect could be a showstopper for coherent OWC which is sensitive to the frequency offset and spread. Thus we introduce a new modulation scheme, which called orthogonal time frequency space (OTFS) modulation, into the coherent OWC to solve the Doppler problem. OTFS transforms traditional time-varying channel into delay-Doppler (DD) domain, which ensures all transmit symbols experience an almost identical and slowly varying sparse channel. Thus full channel diversity in time and frequency can be obtained when a suitable receiver is used. In addition, most of the research on Doppler effect only consider the random Doppler spread and average frequency shift to the signal, while ignoring the spectral spread caused by the frequency-dependent Doppler shift of a wideband signal such as radar signals and terahertz signals. To accurately model the Doppler effect, it is necessary to calculate the Doppler frequency shift according to the frequency bin of each sub-carrier, thereby the overall frequency offset and spectral spread are included. This manuscript proposes a Doppler channel model based on frequency-domain subband partition (FDSP), and for the first time, this wideband Doppler channel model is applied into wideband OTFS and orthogonal frequency division multiplexing (OFDM) systems. We carried out simulation for OTFS and OFDM under different velocities. Simulation results show that the OTFS can resist high Doppler frequency shift in high mobility scenarios, and in the case of large subcarrier spacing, OTFS is less affected by the Doppler frequency shift of each subcarrier than OFDM.

The resolution of the integer phase ambiguity among a group of spatially separated sensors is considered, where the smallest inter-sensor spacing exceeds half wavelength (λ/2) of a single-frequency signal. The sufficient condition that the integer phase ambiguities can be unambiguously determined is derived and verified numerically. The traditional receiver of a triplet is identified as a particular example of this general framework. An efficient strategy for averaging redundant virtual observations is outlined. The performance in terms of the success rate of ambiguity resolution is significantly improved due to the averaging process.