In this paper,the covert age of information(CAoI),which characterizes the timeliness and covertness performance of communication,is first investigated in the short-packet covert communication with time modulated retro...In this paper,the covert age of information(CAoI),which characterizes the timeliness and covertness performance of communication,is first investigated in the short-packet covert communication with time modulated retrodirective array(TMRDA).Specifically,the TMRDA is designed to maximize the antenna gain in the target direction while the side lobe is sufficiently suppressed.On this basis,the covertness constraint and CAoI are derived in closed form.To facilitate the covert transmission design,the transmit power and block-length are jointly optimized to minimize the CAoI,which demonstrates the trade-off between covertness and timelessness.Our results illustrate that there exists an optimal block-length that yields the minimum CAoI,and the presented optimization results can achieve enhanced performance compared with the fixed block-length case.Additionally,we observe that smaller beam pointing error at Bob leads to improvements in CAoI.展开更多
This article proposes and demonstrates a retrodirective array(RDA)for two-way wireless communication with automatic beam tracking.The proposed RDA is enabled by specifically designed chips made using a domestic comple...This article proposes and demonstrates a retrodirective array(RDA)for two-way wireless communication with automatic beam tracking.The proposed RDA is enabled by specifically designed chips made using a domestic complementary metal-oxide semiconductor(CMOS)process.The highly integrated CMOS chip includes a receiving(Rx)chain,a transmitting(Tx)chain,and a unique tracking phaselocked loop(PLL)for the crucial conjugated phase recovery in the RDA.This article also proposes a method to reduce the beam pointing error(BPE)in a conventional RDA.To validate the above ideas simply yet without loss of generality,a 2.4 GHz RDA is demonstrated through two-way communication links between the Rx and Tx chains,and an on-chip quadrature coupler is designed to achieve a nonretrodirective signal suppression of 23 dBc.The experimental results demonstrate that the proposed RDA,which incorporates domestically manufactured low-cost 0.18 lm CMOS chips,is capable of automatically tracking beams covering±40with a reduced BPE.Each CMOS chip in the RDA has a compact size of 4.62 mm^(2) and a low power consumption of 0.15 W.To the best of the authors’knowledge,this is the first research to demonstrate an RDA with a fully customized CMOS chip for wireless communication with automatic beam tracking。展开更多
An improved adaptive genetic algorithm is presented in this paper. It primarily includes two modified methods： one is novel adaptive probabilities of crossover and mutation, the other is truncated selection approach....An improved adaptive genetic algorithm is presented in this paper. It primarily includes two modified methods： one is novel adaptive probabilities of crossover and mutation, the other is truncated selection approach. This algorithm has been validated to be superior to the simple genetic algorithm （SGA） by a complicated binary testing function. Then the proposed algorithm is applied to optimizing the planar retrodirective array to reduce the cost of the hardware. The fitness function is discussed in the optimization example. After optimization, the sparse planar retrodirective antenna array keeps excellent retrodirectivity, while the array architecture has been simplified by 34%. The optimized antenna array can replace uniform full array effectively. Results show that this work will gain more engineering benefits in practice.展开更多
The retrodirective antenna array is considered as a mechanism to enable target tracking of a power receiver for long range wireless power transfer(WPT)due to its simplicity in implementation using only analog circuits...The retrodirective antenna array is considered as a mechanism to enable target tracking of a power receiver for long range wireless power transfer(WPT)due to its simplicity in implementation using only analog circuits.By installing the retrodirective capability on both the generator and rectenna arrays,a feedback loop that produces a high efficiency WPT channel is created.In this paper,we characterize the dynamics of this phenomenon using a discrete-time state-space model based on S-parameters and show that the system can naturally achieve maximum theoretical WPT efficiency.We further confirmed the theoretical analysis through a hardware experiment using a 12-port circuit board with measurable S-parameters mimicking a static wireless channel.The results collected from the hardware experiment show agreement with the proposed theoretical framework by comparing the theoretical efficiency with the measured efficiency and by showing that the collected data points follow the predicted condition to achieve maximum efficiency.展开更多
Future communications will provide higher transmission rates and higher operating frequencies.In addition,agile beam tracking will be an inevitable trend in technology development.The terahertz retrodirective antenna ...Future communications will provide higher transmission rates and higher operating frequencies.In addition,agile beam tracking will be an inevitable trend in technology development.The terahertz retrodirective antenna array proposed and discussed in this paper can be a better solution for agile beam tracking.The array receives a 40-GHz navigation signal and accurately retransmits a 120-GHz beam in the direction of the arrival wave.Simulation results indicate that the proposed array with a stacked sandwich structure has realized the tracking of the received wave.The scanning radiation pattern shows that the array gain is 23.87 d B at 19.9°when the incident angle is 20°with a relative error of only 0.5%,meaning that there is a lateral error of only 8.7 m at a transmission distance of 5 km.展开更多
文摘In this paper,the covert age of information(CAoI),which characterizes the timeliness and covertness performance of communication,is first investigated in the short-packet covert communication with time modulated retrodirective array(TMRDA).Specifically,the TMRDA is designed to maximize the antenna gain in the target direction while the side lobe is sufficiently suppressed.On this basis,the covertness constraint and CAoI are derived in closed form.To facilitate the covert transmission design,the transmit power and block-length are jointly optimized to minimize the CAoI,which demonstrates the trade-off between covertness and timelessness.Our results illustrate that there exists an optimal block-length that yields the minimum CAoI,and the presented optimization results can achieve enhanced performance compared with the fixed block-length case.Additionally,we observe that smaller beam pointing error at Bob leads to improvements in CAoI.
基金supported in part by the National Key Research and Development Program of China(2019YFB2204701)in part by the National Natural Science Foundation of China(61831006,62022023,and 62250610223)in part by the Big Data Computing Center at Southeast University for numerical calculation.
文摘This article proposes and demonstrates a retrodirective array(RDA)for two-way wireless communication with automatic beam tracking.The proposed RDA is enabled by specifically designed chips made using a domestic complementary metal-oxide semiconductor(CMOS)process.The highly integrated CMOS chip includes a receiving(Rx)chain,a transmitting(Tx)chain,and a unique tracking phaselocked loop(PLL)for the crucial conjugated phase recovery in the RDA.This article also proposes a method to reduce the beam pointing error(BPE)in a conventional RDA.To validate the above ideas simply yet without loss of generality,a 2.4 GHz RDA is demonstrated through two-way communication links between the Rx and Tx chains,and an on-chip quadrature coupler is designed to achieve a nonretrodirective signal suppression of 23 dBc.The experimental results demonstrate that the proposed RDA,which incorporates domestically manufactured low-cost 0.18 lm CMOS chips,is capable of automatically tracking beams covering±40with a reduced BPE.Each CMOS chip in the RDA has a compact size of 4.62 mm^(2) and a low power consumption of 0.15 W.To the best of the authors’knowledge,this is the first research to demonstrate an RDA with a fully customized CMOS chip for wireless communication with automatic beam tracking。
文摘An improved adaptive genetic algorithm is presented in this paper. It primarily includes two modified methods： one is novel adaptive probabilities of crossover and mutation, the other is truncated selection approach. This algorithm has been validated to be superior to the simple genetic algorithm （SGA） by a complicated binary testing function. Then the proposed algorithm is applied to optimizing the planar retrodirective array to reduce the cost of the hardware. The fitness function is discussed in the optimization example. After optimization, the sparse planar retrodirective antenna array keeps excellent retrodirectivity, while the array architecture has been simplified by 34%. The optimized antenna array can replace uniform full array effectively. Results show that this work will gain more engineering benefits in practice.
文摘The retrodirective antenna array is considered as a mechanism to enable target tracking of a power receiver for long range wireless power transfer(WPT)due to its simplicity in implementation using only analog circuits.By installing the retrodirective capability on both the generator and rectenna arrays,a feedback loop that produces a high efficiency WPT channel is created.In this paper,we characterize the dynamics of this phenomenon using a discrete-time state-space model based on S-parameters and show that the system can naturally achieve maximum theoretical WPT efficiency.We further confirmed the theoretical analysis through a hardware experiment using a 12-port circuit board with measurable S-parameters mimicking a static wireless channel.The results collected from the hardware experiment show agreement with the proposed theoretical framework by comparing the theoretical efficiency with the measured efficiency and by showing that the collected data points follow the predicted condition to achieve maximum efficiency.
基金Project supported by the National Key R&D Program of China(No.2018YFB1801505)the National Natural Science Foundation of China(Nos.61527805 and 61731001).
文摘Future communications will provide higher transmission rates and higher operating frequencies.In addition,agile beam tracking will be an inevitable trend in technology development.The terahertz retrodirective antenna array proposed and discussed in this paper can be a better solution for agile beam tracking.The array receives a 40-GHz navigation signal and accurately retransmits a 120-GHz beam in the direction of the arrival wave.Simulation results indicate that the proposed array with a stacked sandwich structure has realized the tracking of the received wave.The scanning radiation pattern shows that the array gain is 23.87 d B at 19.9°when the incident angle is 20°with a relative error of only 0.5%,meaning that there is a lateral error of only 8.7 m at a transmission distance of 5 km.
