2020/3
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- ItemPassive Presence Detection Algorithm for Wi-Fi Sensing(Společnost pro radioelektronické inženýrství, 2020-09) Lomayev, Artyom; Da Silva, Claudio R. C. M.; Maltsev, Alexander; Cordeiro, Carlos; Sadri, Ali S.In this paper, we derive a signal processing algorithm that enables a Wi-Fi station to passively detect the presence of a potential user in its vicinity. It is assumed that the potential user either doesn’t carry a Wi-Fi device or, if it does, that its device does not participate in the detection procedure. Passive presence detection is performed by the station by means of tracking over time channel estimates obtained with packets transmitted by one or more stations in the Wi-Fi network, and determining when the user presence impacts the received signals. The proposed algorithm performs binary hypothesis testing and decides if a potential user is in the vicinity of the Wi-Fi station. It uses an estimate of the dynamic channel component power as the test statistic and compares it to a predefined threshold. As formulated in the paper, to increase the detection reliability, the power of the dynamic channel component is maximized by using an optimization procedure. Experimental results obtained with off-the-shelf Wi-Fi devices and with the proposed algorithm are presented which demonstrate the validity of the analytical formulation, as well as the feasibility of performing passive presence detection using a Wi-Fi network. In controlled residential and enterprise settings, the proposed algorithm provided a detection rate of 99.7% for a false alarm rate of less than 1%.
- ItemA Covert Communication System Using Non-Zero Mean Normal Distributions(Společnost pro radioelektronické inženýrství, 2020-09) Xu, Zhijiang; Lu, Weidang; Gong, Yi; Hua, Jingyu; Jin, WenbingA covert communication system is proposed in this study, in which a~ non-zero mean Gaussian sequence is used as a~ random carrier and its mean is modulated by a~ covert binary bit. The aperiodic transmitted signal exhibits the same statistical characteristics as the ambient noise to confuse an~ eavesdropper. The received signal is multiplied with the pseudo-random sequence synchronized with the transmitter to recover these positive and negative mean Gaussian sequence. The sample mean estimator and hard decision are used to determine the covert message, and accordingly, theoretical bit error rate in additive white Gaussian noise channel is also derived. Simulation results are very consistent with the theoretical derivation. The proposed system works in the physical layer with the advantages of simple structure, strong concealment, good BER performance and very suitable for low-cost, resource-limited and low-rate transmission devices.
- ItemDual HE11δ Mode CDRA for Polarization Diversity Applications in K Band Point-to-Point Communications(Společnost pro radioelektronické inženýrství, 2020-09) Faiz, Alam M.; Shafique, M. Farhan; Gososh, Nayab; Khan, Shahid A.; Khan, Mahmood A.A dual port Cylindrical Dielectric Resonator Antenna (CDRA) has been demonstrated for K band (22 GHz) applications in this work. The antenna offers polarization diversity which is introduced by degenerating HE11δ modes in a single CDRA. Orthogonal feed lines produce two modes which are perpendicular so they don’t interfere with each other and offer excellent linear polarization diversity in orthogonal planes. Since the CDRA size is compact, the feed lines have been modified to assure the generation of desired modes. A detailed investigation into the generation of resonant modes along with parametric analysis is presented. Measured results show fractional bandwidth of 9.5% and 18.18% for both port 1 and port 2 respectively. Isolation of better than 32 dB has been measured between the two ports through transmission coefficient. Difference of about 20 dB between co-polarization and cross polarization in both planes for broadside direction has been measured which endorses the polarization diversity performance of the antenna. Different MIMO performance parameters including envelope correlation coefficient, total active reflection coefficient, channel capacity loss and mean effective gain have been measured to assess the performance of the design.
- ItemEvolution of Low-Profile Ultra-Wideband Frequency Selective Surface with a Stable Response and Sharp Roll-Off at Lower Band for C, X and Ku Band Applications(Společnost pro radioelektronické inženýrství, 2020-09) Biswas, Anik Naha; Ballav, Suparna; Chatterjee, Ayan; Parui, Susanta KumarThis paper focuses on two different design flows of how an ultra-wideband FSS can be achieved from a narrow band structure. By amalgamating a capacitive patch with a corrugated square slot structure, as the first approach while the second approach involved designing a dual layer FSS by etching the corrugated square slot at both top and the bottom layer of the substrate. A 98% bandwidth extending from 5.5 GHz to 16 GHz was achieved using the first approach while the modified structure yields about 107% bandwidth covering up the entire range from 5 GHz to 16.5 GHz, hence improving the performance in terms of bandwidth. The final modified FSS structure manifests the polarization insensitive nature as well as angle insensitivity up to 60 degree angle of incidence in terms of the entire range of the wide reflection band, and covering all the three bands (C, X and Ku band). The transmission coefficient manifests a stable response below 20 dB almost throughout the entire band without significant variation. The measured result shows good agreement with the experimented result validating the fabricated prototype and measurement. The bandwidth can be tuned by varying different parameters like corrugation dimension, dielectric permittivity, substrate height which have been explained in this paper.
- ItemA Compact Circular Loop Inspired Frequency and Bandwidth Reconfigurable Antenna for 4G, 5G, and X- Band Applications(Společnost pro radioelektronické inženýrství, 2020-09) Rasool, Maryam; Khan, Aabia; Bhatti, Farooq; Ijaz, Bilal; Iftikhar, AdnanThis paper presents a printed patch antenna design to achieve frequency and bandwidth reconfigurability. Two RF PIN diodes are simultaneously operated to achieve the multi-reconfigurability operation. The patch is inspired from a circular loop design. The basic structure of loop is altered, and PIN diodes are integrated into the patch. The antenna operates in dual band configuration at 3.42 and 8.02 GHz in the diodes ‘OFF’ state, whereas the antenna switches to triple band operation at 2.21, 4.85, and 10.19 GHz in the diodes ‘ON’ state. Moreover, the antenna also exhibits an increased bandwidth from 7.54 to 12 GHz in the diodes ‘ON’ state, as compared to a narrow bandwidth from 7.71 to 8.48 GHz in the diodes ‘OFF’ state. The proposed antenna structure is implemented and fabricated using FR4 epoxy substrate of relative permittivity 4.4, and thickness 1.6 mm. Implemented design exhibits measured gains of 3.06 dBi, 2.81 dBi, and 2.92 dBi at 2.21, 4.85, and 10.19 GHz in the PIN diodes ‘ON’ state, respectively, while in the PIN diodes ‘OFF’ state, at 3.42 GHz the gain is 3.03 dBi and at 8.02 GHz the gain is 3.37 dBi. Overall, simulation results agree well with the measured results.