学　术

　　为搭建我校博士后之间的学术交流平台，促进学术水平提升，学校博士后管理办公室组织开展博士后学术沙龙活动。本次沙龙由我校博士后王宏伟和王健全分享其研究成果，诚挚邀请感兴趣的师生参加。

　　一、时　间：2021年4月29日（周四）14：00

　　二、地　点：清水河校区经管楼宾诺咖啡

　　三、主办单位：电子科技大学博士后管理办公室

　　四、承办单位：通信抗干扰技术国家级重点实验室

　　五、活动安排：

　　报告一：

　　（1）主题：Compressive Wideband Spectrum Sensing and Carrier Frequency Estimation with Unknown MIMO Channels

　　（2）主讲人： 王宏伟  通信抗干扰技术国家级重点实验室博士后

　　（3）交流内容：

　　Wide band spectrum sensing (WSS), which is aimed to identify the spectral occupancy over a wide frequency band, arises in many applications, e.g., cognitive radio communications and spectrum surveillance. A conventional receiver operating at a Nyquist sampling rate in accordance with the well-known Shannon sampling theorem is generally costly or infeasible for the WSS since sensing a wide frequency band entails a very high sampling rate and leads to a heavy burden on subsequent storage and processing. Recently, various sub-Nyquist sampling based schemes were proposed for the WSS. Nevertheless, most existing methods assume that the far-field source signal impinges on receivers via a line-of-sight (LOS) path, which may not be true in practice due to multipath propagation.

　　In this talk, we discuss the problem of joint wide band spectrum sensing and carrier frequency estimation in a sub-Nyquist sampling framework. Specifically, a multi-antenna receiver is devised to jointly estimate the carrier frequencies and power spectra of multiple narrowband transmissions that spread over a wide frequency band. Unlike existing works that assume the source signals impinge on the receiver via a line-of-sight (LOS) path, we consider a more practical multiple-input multiple-output (MIMO) channel characterized by multipath propagation. A new sub-Nyquist sampling architecture is proposed, where each antenna output passes through two channels, namely, a direct path and a delayed path with a pre-determined time delay. The signal at each channel is then sampled by a synchronized low-rate analog-to-digital converter (ADC). We utilize the collected data samples to build a set of cross-correlation matrices with different time lags and develop a CANDECOMP/PARAFAC (CP) decomposition-based method to recover the carrier frequencies and power spectra of the source signals. Simulation results show that our proposed method achieves an estimation accuracy close to the associated Cramér-Rao bounds using only a small number of data samples.

　　（4）主讲人简介：

　　Hongwei Wang received the Bachelor degree and Ph.D. degree both from the Northwestern Polytechincal University, in 2013 and 2019, respectively. He currently works as a Postdoctoral Researcher in the National Key Laboratory of Science and Technology on Communications of UESTC. His main research interests include wide band spectrum sensing, cell-free massive MIMO and statistical signal processing.

　　报告二：

　　（1）主题：Optimal Strategy in Covert Communication based on Game Theory

　　（2）主讲人：王健全  通信抗干扰技术国家级重点实验室博士后

　　（3）交流内容：

　　Covert communication provides the security for wireless communications via hiding the existence of the transmissions. In this talk, we first briefly introduce the concept of covert communication. Then, we consider a scenario that the transmitter and the warden do not know the state information of each other. We formulate a power threshold game and a Bayesian game to model the scenario. The optimal strategies are given by the game theory concept solutions, i.e. the Nash equilibrium (NE) and the Bayesian Nash equilibrium (BNE). For the power threshold game, we prove the existence of the NE and give a numerical method to calculate it. We prove that the BNE can be calculated by solving another optimal problem. The method to solve the optimal problem is also proposed. Numerical results are shown to illustrate the stability of the equilibrium and the performances of the optimal strategies.

　　（4）主讲人简介：

　　Jianquan Wang received the Bachelor degree and Ph.D. degree from UESTC, in 2013 and 2019, respectively. He currently works as a Postdoctoral Fellow in the National Key Lab of Communication Science of UESTC. His research interests include covert communication, anti-jamming communication and information security.

　　　　　　　　　　　　　　　　　　　电子科技大学博士后管理办公室

　　　　　　　　　　　　　　　　　　　　　　　2021年4月25日