摘要：In this paper, we introduce a new concept, namely ε-arithmetics, for real vectors of any fixed dimension. The basic idea is to use vectors of rational values (called rational vectors) to approximate vectors of real values of the same dimension within ε range. For rational vectors of a fixed dimension m, they can form a field that is an mth order extension Q(α) of the rational field Q where α has its minimal polynomial of degree m over Q. Then, the arithmetics, such as addition, subtraction, multiplication, and division, of real vectors can be defined by using that of their approximated rational vectors within ε range. We also define complex conjugate of a real vector and then inner product and convolutions of two real vectors and two real vector sequences (signals) of finite length. With these newly defined concepts for real vectors, linear processing, such as linear filtering, ARMA modeling, and least squares fitting, can be implemented to real vector-valued signals with real vector-valued coefficients, which will broaden the existing linear processing to scalar-valued signals.
关键词：Arithmetics;Rational vectors;Real vectors;Rational field;Algebraic number field;Field extension;Algebraic number;Inner product;Linear processing of real vector-valued signals
摘要：novel broadband metasurface (MTS) antenna array with high front-to-back ratio (FBR) is proposed for 28 GHz millimeter-wave applications. With slot pairs loaded on patch cells, an aperture-coupled slotted-mushroom MTS antenna is designed to obtain broadband radiation characteristics with a compact size. To suppress the backward radiation of this antenna, the printed ridge gap waveguide (PRGW) technology with a perfect magnetic conductor (PMC) shielding made of mushroom unit-cells underneath the microstrip feeding line is applied. On this basis, a 4 × 4 MTS antenna array with the PRGW feed network is developed. Simulated results show that the FBR can be highly improved by over 16 dB within the entire bandwidth. To validate the design, a prototype of the proposed antenna is fabricated. Measured results show that an FBR greater than 28 dB can be obtained over a 24% impedance bandwidth (from 24.9 GHz to 31.7 GHz) with the reflection coefficient less than −10 dB. The measured antenna gain ranges from 17 dBi to 19.2 dBi and the corresponding measured aperture efficiencies are 35% and 45.6%. The measured results also suggest that the proposed MTS antenna possesses −35 dB cross-polarization level and stable radiation patterns. In addition, the proposed antenna remains a very low profile of 1.7 mm (0.17λ_{0} at 28 GHz). All the achieved features indicate that the proposed MTS antenna is an important candidate for B5G and 6G wireless communication.
关键词：Broadband;Metasurface antenna;Front-to-back ratio (FBR);Printed ridge gap waveguide technology (PRGW);Low profile
摘要：Vehicles have been majorly used for transportation in the last century. With the proliferation of onboard computing and communication capabilities, we envision that future connected vehicles (CVs) will be serving as a mobile computing platform in addition to their conventional transportation role for the next century. In this article, we present the vision of Vehicle Computing, i.e., CVs are the perfect computation platforms, and connected devices/things with limited computation capacities can rely on surrounding CVs to perform complex computational tasks. We also discuss Vehicle Computing from several aspects, including several case studies, key enabling technologies, a potential business model, a general computing framework, and open challenges.
摘要：In this paper, we propose a new class of nonbinary polar codes, where the symbol-level polarization is achieved by using a 2 × 2 q-ary matrix 10β1 as the kernel. Under bit-level code construction, some partially-frozen symbols exist, where the frozen bits in these symbols can be used as active-check bits to facilitate the decoder. The encoder/decoder of the proposed codes has a similar structure to the original binary polar codes, admitting an easily configurable and flexible implementation, which is an obvious advantage over the existing nonbinary polar codes based on Reed-Solomon (RS) codes. A low-complexity decoding method is also introduced, in which only more competitive symbols are considered rather than the whole q symbols in the finite field. To support high spectral efficiency, we also present, in addition to the single level coded modulation scheme with field-matched modulation order, a mixed multilevel coded modulation scheme with arbitrary modulation in order to trade off the latency against complexity. Simulation results show that our proposed nonbinary polar codes exhibit comparable performance with the RS4-based polar codes and outperform binary polar codes with low decoding latency, suggesting a potential application for future ultra-reliable and low-latency communications (URLLC).
Chengjun Jiang,Chensi Zhang,Leilei Mu,Zhe Zhang,Jianhua Ge
2023, 1(1) DOI: 10.1016/j.jiixd.2022.11.001
摘要：Satellite communications and reconfigurable intelligent surface (RIS) are considered as two promising technologies that can significantly improve the coverage and energy efficiency of future wireless communication networks. The satellite communications security is often threatened due to its broadcasting nature. To enhance the physical layer security (PLS) of satellite communications with channel similarity, an aerial RIS-aided dual full-duplex (DFD-ARIS) cooperative jamming method is presented in this paper. Specifically, unlike the existing works that relied on channel difference, DFD-ARIS utilizes the channel similarity against the eavesdroppers with the help of ARIS. In addition, the power allocation is further studied in conjunction with the phase design of RIS to minimize the total power under the constraints of data rate, satellite power limitation and secrecy rate. Then, the closed-form solutions are achieved. Simulation results show that the performance of the proposed scheme is superior to the traditional method.
摘要：In this paper, we present a soil methane emissions suppression approach using swarms of unmanned aerial vehicles (UAVs), by spreading biochar mulch on top of the detected methane emissions area/source. Soil microorganisms can produce methane and release it into the atmosphere causing climate change such as global warming. However, people lack methods to manage soil methane emissions, especially quantification of methane emissions from the soil. Current measurement and suppression of methane methods are often limited due to the maintenance, installation, and calibration requirements of these sensing systems. To overcome these drawbacks, we present a new method called FADE-MAS2D (Fractional Advection Diffusion Mobile Actuator and Sensor) in which swarming UAVs are applied as optimal coverage control actuators to various methane release scenarios (from single to multi-source disturbances) utilizing an anomalous diffusion model with different time, and space fractional orders subject to wind fields. This strategy is based on the premise that methane diffusion can be modeled as an anomalous diffusion equation, and swarming UAVs can be applied to tackle the optimal coverage control issue. To simulate methane diffusion under the wind, we utilize the fractional calculus to solve the anomalous diffusion equation and define wind force with the drag equation. In addition, we integrated emissions control, UAV control efforts, and UAV location error in our cost function. Finally, we evaluated our approach using simulation experiments with methane diffusion and multiple methane emission sources in the time and space domain, respectively. The results show that when α = 0.8 and β = 1.8, the shape and emissions of methane perform well. Furthermore, our approach resulted in great control performance with multiple methane emission sources and different wind velocities and directions.
关键词：Fractional calculus;Diffusion;CVT;DIFF-MAS-2D;FADE-MAS-2D;Coverage control