Iterative Signal Processing for Integrated Sensing and Communication Systems

Integrated sensing and communication (ISAC), with sensing and communication sharing the same wireless resources and hardware, has the advantages of high spectrum efficiency and low hardware cost, which is regarded as one of the key technologies of the fifth generation advanced (5G-A) and sixth generation (6G) mobile communication systems. ISAC has the potential to be applied in the intelligent applications requiring both communication and high accurate sensing capabilities. The fundamental challenges of ISAC system are the ISAC signal design and ISAC signal processing. However, the existing ISAC signal has low anti-noise capability. And the existing ISAC signal processing algorithms have the disadvantages of quantization errors and high complexity, resulting in large energy consumption. In this paper, phase coding is applied in ISAC signal design to improve the anti-noise performance of ISAC signal. Then, the effect of phase coding method on improving the sensing accuracy is analyzed. In order to improve the sensing accuracy with low-complexity algorithm, the iterative ISAC signal processing methods are proposed. The proposed methods improve the sensing accuracy with low computational complexity, realizing energy efficient ISAC signal processing. Taking the scenarios of short distance and long distance sensing into account, the iterative two-dimensional (2D) fast Fourier transform (FFT) and iterative cyclic cross-correlation (CC) methods are proposed, respectively, realizing high sensing accuracy and low computational complexity. Finally, the feasibility of the proposed ISAC signal processing methods are verified by simulation results

Oxidative removal of quinclorac by permanganate through a rate-limiting [3+2] cycloaddition reaction

Quinclorac, a widely used herbicide in agriculture, has been recognized as an emerging environmental pollutant owing to its long persistence and potential risk to humans. However, no related information is available on the degradation of quinclorac by employing oxidants. Herein, the reactivity of quinclorac with permanganate was systematically investigated in water by combining experimental and computational approaches. The reaction followed overall second-order kinetics pointing to a bimolecular rate-limiting step. The second-order rate constant was found to be 3.47 10 3 M 1 s 1 at 25 C, which was independent of pH over the range from 5 to 9 and was dependent on temperature over the range from 19 to 35 C. The initial product was identified by UPLC-Q-TOF-MS to be monohydroxylated quinclorac, which was more susceptible to further oxidation. The result could be supported by the complete simulation of the reaction process in DFT calculations, indicating the [3 + 2] cycloaddition oxidation of the benzene ring in the rate-limiting step. The plausible mechanism was then proposed, accompanied by the analysis of the HOMO indicating the hydroxylation position and of the ESP suggesting a more electron-rich moiety. Considering the high effectiveness and low toxicity, permanganate oxidation was considered to be a very promising technique for removing quinclorac from aquatic environments

Enhanced Oxidation of Tetracycline by Permanganate via the Alkali-Induced Alteration of the Highest Occupied Molecular Orbital and the Electrostatic Potential

The reaction between tetracycline and alkaline permanganate was investigated by combining experimental and computational methods. The kinetics was initially studied using a stopped-flow technique and was found to be first-order in tetracycline and permanganate. The second-order rate constant was positive linearly dependent on the concentration of hydroxyl ion (0.01–0.10 M), indicating the presence of base catalysis. By construction of the Eyring plots in the range of 293–308 K, a lower activation barrier ((14.89 ± 0.44) kcal mol^–1) was obtained at 298 K for the base-catalyzed pathway compared with that ((17.72 ± 1.84) kcal mol^–1) for the uncatalyzed pathway. The effect of ionic strength further suggested the existence of a complex with higher charge and reactivity. It is confirmed by the theoretical analysis that the hydroxyl ion could attract the proton of tetracycline toward itself to form a complex-like structure with a highly reactive phenolate-type moiety. The highest occupied molecular orbital of tetracycline was then transformed from double bond to aromatic ring. The result is supported by the product analysis that the initial oxidation of tetracycline by permanganate occurred predominantly at phenolic group in an alkaline aqueous solution. The base-catalyzed effect was finally explained by electrostatic potential that hydroxyl ion was able to increase the negative charge of tetracycline, making its phenolic group a more electron-rich moiety for electrophilic attack