AbstractBeamforming network with the Doppler suppression scheme reducing the channel time‐varying effects has attracted much research interests in high‐mobility massive MIMO communications. However, the current time‐varying beamforming network still suffers from high volatility peak‐to‐average power ratio (PAPR) fluctuations. For this reason, a time invariant compensation optimized beamformer is proposed to mitigate the peak‐to‐average power ratio high volatility and the channel time variation in the high‐mobility uplink transmission. To attain the Doppler spread and implement the Doppler spread suppression scheme, a time‐varying spectrum (TVS) is proposed and its statistical properties of time‐varying spectrum is analyzed. The simulation results are provided to verify the proposed studies.

AbstractIn this letter, a design of virtual guarded SiPMs fabricated in a standard 0.35μm standard complementary metal oxide semiconductor (CMOS) process is introduced. The performance of these virtual guarded cells (VGC) is compared to that of conventional cells with real guard rings, referred to as physical guarded cells (PGC). Specifically, the photon detection efficiency (PDE) of both types of SiPMs is evaluated. For this, PDE calculations are conducted at different overvoltages (OVs) and the PDE is compared depending on the wavelength before conducting measurements. The results demonstrate that the VGC SiPM outperforms the PGC SiPM, exhibiting a true PDE of (22.5 ± 0.5)%, which is significantly higher than the PDE of (10.9 ± 0.3)% obtained for the PGC SiPM. The superior PDE of the VGC SiPM is attributed to a larger active or photosensitive area due to the virtual guard rings and a thinner n‐layer in the photosensitive region.

AbstractAudio zero‐watermarking is a promising technology for audio copyright protection. It does not modify the content of the original carrier and has good imperceptibility. Considering that i‐vector model can map audio signals of different lengths into a vector space of fixed length, which has good robustness against desynchronization attacks, a robust audio zero‐watermarking technique based on i‐vector model is proposed here. The proposed scheme extracts the i‐vector of the input signal to identify its inherent stability features and then generates a key by XOR operation on the watermark and encoded feature sequences. Experimental results show that this scheme can effectively resist common attacks and desynchronization attacks.

AbstractThe article shows that transient chaos phenomena can be observed in a generalized memristor Chua's circuit where a nonlinear resistor is introduced to better model the real memristor behaviour. The flux‐charge analysis method is used to explain the origin of transient chaos, that is attributed to the drift of the index of the memristor circuit invariant manifolds caused by the charge flowing into the nonlinear resistor.

AbstractGeometric partitioning mode (GPM) was newly adopted in Versatile Video Coding (VVC) to increase the partitioning precision of the arbitrary boundaries of actual objects. Note that the blending process of the GPM is not suitable for screen content with various sharp and strong edges. To alleviate this drawback, three new GPM matrices are introduced, and an efficient GPM is proposed to utilize four different GPM matrices and implicitly determine one of them depending on the discontinuity and gradients of the two predictors. The proposed method achieves an average BD‐rate reduction of 1.2% and 1.6% without additional computational complexity for random access and low‐delay B configurations, respectively, over the VVC test model (VTM18.0).

AbstractIn this letter, the authors present a novel expression for the probability of line‐of‐sight (LoS) between a UAV and ground users situated on a gridded street within urban and dense urban environments. Firstly, this study conducts extensive ray‐tracing simulations, encompassing over 50,000 receivers positioned along streets in Brooklyn and Manhattan, respectively. Moreover, the impact of street width on the probability of LoS is investigated, considering three different average widths. By fitting the LoS probability data corresponding to the UAV's elevation angle in two urban environments obtained by simulations, a unified expression representing the relationship between the LoS probability and the UAV's elevation angle is obtained. This obtained LoS probability expression is compared with three existing expressions. The findings presented in this letter can provide some valuable insights for analytical studies on channel modelling between UAVs and ground‐based street users including vehicles.

AbstractPower system inertia is receiving increasing attention because the inclusion of renewable energy generation equipment weakens the inertia of the regional equivalent system and affects the transient stability of the system. In this paper, the influence of variation of inertia constant on the transient stability of the system is studied analytically by adding short‐circuit faults, Equal Area Criterion, and derivation of equations. On the basis of theoretical analysis, multi‐machine system is established to simulate and verify the correctness of the analysis results.

AbstractCsiNet, a deep neural network framework, utilizes an autoencoder to efficiently transmit downlink channel state information (CSI) in the feedback link, which reduces the cost of feedback, and significantly improves the quality of the reconstruction. However, the model with massive parameters incurs a lot of storage space and high computational complexity, which is impractical for low‐cost and low‐power edge devices. In this work, a lightweight CsiNet based SNIP (Single‐shot Network Pruning) is implemented, which prunes the model using the gradient information of the first training epoch, eliminating both pretraining and the complex pruning schedule. Numerical simulation results show that, under the same compression rates, the method can achieve a similar or even better reconstruction effect and more effectively reduce computational complexity, compared to traditional lightweight methods.

AbstractThe Society of Automotive Engineers (SAE) J2945/1 standard for Dedicated Short Range Communication (DSRC) environmentutilizes transmit (Tx) power control and rate control elements for the periodic BSM transmissions, which are intended to work in a complementary manner. An equivalent standard for the cellular vehicle‐to‐everything (C‐V2X) communication environment is J3161/1, but it eliminates Tx power control and uses only rate control. However, the consequence is the degraded update delay of neighbouring vehicles’ kinematics, potentially undermineing driving safety. In this Letter, the authors propose to retain the dual‐mode control in the C‐V2X environment and find a policy through reinforcement learning (RL) to adjust the rate control function to maintain synergy. Moreover, the authors can extract the RL‐created policy from the neural network so that it can be explicitly specified in the standard, and downloaded and used more conveniently by vehicles. Finally, the RL‐generated policy achieves a better packet delivery frequency than J2945/1 or J3161/1.

AbstractSingle‐mode distributed feedback GaSb‐based interband cascade lasers with record emission beyond 6.1 µm are presented. The results are based on an epitaxial design with reduced resonant intersubband absorption in the valence band and rebalanced internally generated carriers. The epi‐down mounted 8 µm wide and 1 mm long laser chip is operated in continuous wave mode at room temperature and covers a bandwidth of over 20 nm with temperature and current tuning. At 25°C more than 4 mW of optical output power was measured.