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| 1 | Energy-efficient design for mmW ave-enabled NOMA-UAV networks显示文摘Owing to the recent advances of non-orthogonal multiple access(NOMA)and millimeter-wave(mmWave),these two technologies are combined in unmanned aerial vehicle(UAV)networks in this paper.However,energy efficiency has become a significant metric for UAVs owning to their limited energy.Thus,we aim to maximize the energy efficiency for mmWave-enabled NOMA-UAV networks by optimizing the UAV placement,hybrid precoding and power allocation.However,the optimization problem is complicated and intractable,which is decomposed into several sub-problems.First,we solve the UAV placement problem by approximating it into a convex one.Then,the hybrid precoding with user clustering is performed to better reap the multi-antenna gain.Particularly,three schemes are proposed,where the cluster head selection algorithm is adopted while considering different equivalent channels of users.Finally,the power allocation is optimized to maximize the energy efficiency,which is converted to convex and solved via an iterative algorithm.Simulation results are provided to evaluate the performance of the proposed schemes. | Xiaowei PANG Jie TANG Nan ZHAO Xiuyin ZHANG Yi QIAN | 2021 | Science China(Information Sciences)2021，64，4： | 5 |
| 2 | Joint frequency-phase estimation for pilot-limited communication systems: a novel method based on length-variable auto-correlation operator显示文摘Dear editor,Wireless communication systems,such as the fifth-generation(5G),unmanned aircraft vehicle,have widespread applications in our modern society[1–4].This case will significantly decline available spectrum resources,thereby requiring us to provide some solutions.This study proposes a novel method for providing joint frequency-phase estimation for pilot-limited communication systems. | Hengzhou XU Wenjing WEI Bo ZHANG Mengmeng XU Hai ZHU | 2020 | Science China(Information Sciences)2020，63，6： | 1 |
| 3 | Ergodic rate analysis for full-duplex NOMA networks with energy harvesting显示文摘Dear editor,Non-orthogonal multiple access(NOMA),regarded as a promising technique for substantially increasing the spectral efficiency of wireless networks that comprise massive devices,has exhibited a number of significant performance advantages,including the reduced latency,improved reliability,and the capability of offering a higher sum throughput.Furthermore,a device operating in full-duplex(FD)mode only needs half of the time of a half-duplex(HD)device to complete the same amount of data transmission and reception,because a single channel can be reused to enable a simultaneous transmission and reception[1–3].Both FD and NOMA technologies have been widely acknowledged as efficient ways for improving the spectrum efficiency of wireless networks[4–6]. | Bin ZHONG Long CHEN Zhijun TANG | 2021 | Science China(Information Sciences)2021，64，8： | 1 |
| 4 | Directional modulation with distributed receiver selection for secure wireless communications显示文摘In this paper, a novel directional modulation with distributed receiver selection(DM-DRS)scheme is proposed for secure wireless communications. In DM-DRS, a particular subset of receivers is activated and part of the information bits are modulated by the index of the activation pattern, in addition to traditional digital modulation. Especially, the scrambling matrix is introduced for the sake of preventing the eavesdropping. Moreover, the performances of bit error rate(BER) in terms of the union bound for both the legitimate user and eavesdropper are respectively derived in the context of an optimal joint maximum likelihood(ML) detector, and the theoretical BER upper bounds are demonstrated to be tight by the numerical results. In the context of the discrete-input and continuous-output system, the ergodic secrecy rates of the legitimate user and the eavesdropper are obtained, the secrecy rate is also quantified. Furthermore,our numerical results exhibit that DM-DRS can achieve an increased transmission rate compared to its traditional directional modulation with cooperative receivers(DM-CR) and spatial and direction modulation(SDM) counterparts, while guaranteeing an improved BER performance. | Hongyan ZHANG Yue XIAO Wanbin TANG Gang WU Hong NIU Xiaotian ZHOU | 2021 | Science China(Information Sciences)2021，64，12： | 0 |
| 5 | Synthesis-free directional modulation for retrodirective frequency diverse array显示文摘Combination of directional modulation(DM)and frequency diverse array(FDA)provides a novel opportunity for enabling physical layer security because of the enhanced ability of distance resolution.However,in the existing studies,the time-varying nature of the FDA pattern is usually ignored.In this paper,a modified model of FDA-DM is proposed,in which the ignored time factor in the previous studies is taken into consideration for providing a new and more accurate perspective on evaluating the security of FDA-DM.Furthermore,we reveal that FDA-DM can achieve angle-dependent and directional-time-coupleddependent security.After that,based on the retrodirective FDA(RFDA)with a new structure,a novel synthesis-free FDA-DM scheme is proposed for both overcoming the limitations of the FDA-DM scheme and allowing self-tracking the position of the pilot signal without any prior knowledge.Meanwhile,a new set of nonlinear frequency offsets,defined as rearranged linear frequency offsets(RLFOs),is also proposed for both combining the advantages of the linear/nonlinear frequency offsets and bringing conveniences to practical implementation.In addition,the closed-form expression of the average signal-to-artificial-noise-ratio(SANR)is given out for evaluating the security performance of the proposed scheme.Finally,numerical results are presented to verify both the accuracy of the proposed theoretical analysis and the superiority of the RFDADM scheme. | Sheng KE Jianping AN Shuai WANG | 2020 | Science China(Information Sciences)2020，63，10： | 0 |
| 6 | Full-duplex two-way AF relaying systems with imperfect interference cancellation in Nakagami-m fading channels显示文摘Full-duplex(FD)two-way relaying has the potential to substantially improve the spectral efficiency of the system,and is regarded as an enabling technology for the next generation wireless communication systems.Nevertheless,the joint effect of residual interference and channel fading condition on the fundamental performance of FD two-way relaying systems remains unclear.Motivated by this,this study considers a general FD two-way amplify-and-forward(AF)relaying system with imperfect interference cancellation in the versatile Nakagami-m fading channels,and presents a detailed analytical investigation on the outage performance of the system.The findings of the paper suggest that the performance of the FD two-way AF relaying system depends heavily on the residual interference strength,fading condition parameter m,and signal-to-noise ratio(SNR).The FD scheme outperforms the half-duplex(HD)two-way relaying counterpart in the low and moderate SNR regime,while becomes inferior in the high SNR regime,owing to strong residual interference.Also,compared to the channel fading condition of the information transmission channels,the impact of the channel fading condition of the interference channel on the system performance is relatively insignificant.Moreover,it is desirable to deploy the FD scheme when the channel fading condition of the information transmission channels is good,since it can effectively alleviate the detrimental effect of residual interference. | Jianping TONG Caijun ZHONG | 2021 | Science China(Information Sciences)2021，64，8： | 0 |
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