Noise in wireless systems from solar radio bursts

Solar radio bursts were first discovered as result of their interference in early defensive radar systems during the Second World War (1942). Such bursts can still affect radar systems, as well as new wireless technologies. We have investigated a forty-year record of solar radio burst data (1960–1999) as well as several individual radio events in the 23rd solar cycle. This paper reviews the results of a portion of this research. Statistically, for frequencies f  1 GHz (near current wireless bands), there can be a burst with amplitudes >10³ solar flux units (SFU; 1 SFU = 10⁻²² W/m²) every few days during solar maximum conditions, and such burst levels can produce problems in contemporary wireless systems.     

便携式三坐标测量系统中可调光笔的设计

为提高光笔式三坐标测量系统的精度,设计了一个无线控制系统,用于控制光笔上LED的亮度值,点亮个数以及点亮时间。硬件部分主要由无线通信模块,单片机以及LED驱动器组成,而软件主要包括无线通信,串行通信以及LED控制程序三个模块。实验结果表明,相对于传统系统,该系统线性度好,灵敏度高,响应速度快,满足测量系统对实时性、稳定性、灵活性的要求。     

通信导航融合定位技术发展综述

详细分析了蓝牙、Wi-Fi、超宽带、移动通信网络等多种无线网络通信导航融合定位技术的发展现状,并阐述了其面临的挑战,提出了多网融合方法可以提升室内无缝高精度位置服务的可靠性。利用5G移动通信网络,与北斗/GNSS卫星导航系统结合,可以实现相互增强。最后,从天地一体定位导航与授时体系和仿生通信定位导航两方面介绍了通信导航融合定位技术的未来发展趋势。     

重组杂交桥函数的性质研究

在杂交桥函教研究的基础上,用重组杂交的方法,得到一种新型三值函数,并命名为重组杂交桥函数,其函数对应矩阵的列向量即为重组杂交桥函数的函数序列.该函数序列具有分组正交性和良好的自相关特性,并且序列中零的个数可调,可以得到更多具有零相关窗或低相关窗的序列族,这不仅丰富了函数序列的生成方法,而且进一步完善了杂交桥函数理论体系...     

常规兵器远程箭弹遥测的数据传输与处理

论述了在常规兵器远程箭弹遥测系统中进行多站接力串行无线数据传输、建立ＧＰＳ遥测时统以及遥测数据处理等问题     

Relay selection in cooperative communication systems over continuous time-varying fading channel

In this paper, we study relay selection under outdated channel state information (CSI) in a decode-and-forward (DF) cooperative system. Unlike previous researches on cooperative commu-nication under outdated CSI, we consider that the channel varies continuously over time, i.e., the channel not only changes between relay selection and data transmission but also changes during data transmission. Thus the level of accuracy of the CSI used in relay selection degrades with data transmission. We first evaluate the packet error rate (PER) of the cooperative system under contin-uous time-varying fading channel, and find that the PER performance deteriorates more seriously under continuous time-varying fading channel than when the channel is assumed to be constant during data transmission. Then, we propose a repeated relay selection (RRS) strategy to improve the PER performance, in which the forwarded data is divided into multiple segments and relay is reselected before the transmission of each segment based on the updated CSI. Finally, we propose a combined relay selection (CRS) strategy which takes advantage of three different relay selection strategies to further mitigate the impact of outdated CSI.     

国际空间太阳能电站的技术进展

综述了当前国际空间太阳能电站技术的研究进展与发展趋势。重点介绍了空间太阳能电站系统方案新构思“太阳塔”和“太阳盘”的特点；介绍了空间太阳能电站的主要相关技术———无线电能传输技术、太阳能转换技术和空间运输技术等的发展趋势；最后简要介绍了月球电站的进展情况。     

Optimization of beamforming and path planning for UAV-assisted wireless relay networks

Recently, unmanned aerial vehicles （UAVs） acting as relay platforms have attracted considerable attention due to the advantages of extending coverage and improving connectivity for long-range communications. Specifically, in the scenario where the access point （AP） is mobile, a UAV needs to find an efficient path to guarantee the connectivity of the relay link. Motivated by this fact, this paper proposes an optimal design for beamforming （BF） and UAV path planning. First of all, we study a dual-hop amplify-and-forward （AF） wireless relay network, in which a UAV is used as relay between a mobile AP and a fixed base station （BS）. In the network, both of the AP and the BS are equipped with multiple antennas, whereas the UAV has a single antenna. Then, we obtain the output signal~to-noise ratio （SNR） of the dual-hop relay network. Based on the criterion of maximizing the output SNR, we develop an optimal design to obtain the solution of the optimal BF weight vector and the UAV heading angle. Next, we derive the closed-form outage probability （OP） expression to investigate the performance of the dual-hop relay network conveniently. Finally, computer simulations show that the proposed approach can obtain nearly optimal flying path and OP performance, indicating the effectiveness of the proposed algorithm. Furthermore, we find that increasing the antenna number at the BS or the maximal heading angle can significantly improve the performance of the considered relay network.     

Relay selection based on MAP estimation for cooperative communication with outdated channel state information

In this paper, we consider an amplify-and-forward (AF) cooperative communication system when the channel state information (CSI) used in relay selection differs from that during data transmission, i.e., the CSI used in relay selection is outdated. The selected relay may not be actually the best for data transmission and the outage performance of the cooperative system will deteriorate. To improve its performance, we propose a relay selection strategy based on maximum a posteriori (MAP) estimation, where relay is selected based on predicted signal-to-noise ratio (SNR). To reduce the computation complexity, we approximate the a posteriori probability density of SNR and obtain a closed-form predicted SNR, and a relay selection strategy based on the approximate MAP estimation (RS-AMAP) is proposed. The simulation results show that this approximation leads to trivial performance loss from the perspective of outage probability. Compared with relay selection strategies given in the literature, the outage probability is reduced largely through RS-AMAP for medium-to-large transmitting powers and medium-to-high channel correlation coefficients.     

Concept of wireless sensor network for future in-situ exploration of lunar ice using wireless impedance sensor

It is known that a wireless sensor network uses some sort of sensors to detect a physical quantity of interest, in general. The wireless sensor network is a potential tool for exploring the difficult-to-access area on the earth and the concept may be extended to space applications in future. Recently, lunar water has been detected by a few lunar missions using remote sensing techniques. The lunar water is expected to be in the form of ice at very low temperatures of permanently dark regions on the moon. To support the remote observations and also to find out potential ice bearing sites on the moon, in-situ measurement of the lunar ice is essential. However, a rover may not be able to reach the permanently shadowed regions due to terrain irregularity. One possibility to access such areas is to use a wireless sensor network on the lunar surface.