Novel Physical Layer Authentication Techniques for Secure Wireless Communications

Due to the open nature of radio propagation, information security in wireless communications has been facing more challenges compared to its counterpart in wired networks. Authentication, defined as an important aspect of information security, is the process of verifying the identity of transmitters to prevent against spoofing attacks. Traditionally, secure wireless communications is achieved by relying solely upon higher layer cryptographic mechanisms. However, cryptographic approaches based on complex mathematical calculations are inefficient and vulnerable to various types of attacks. Recently, researchers have shown that the unique properties of wireless channels can be exploited for authentication enhancement by providing additional security protection against spoofing attacks. Motivated by the vulnerability of existing higher-layer security techniques and the security advantages provided by exploring the physical link properties, five novel physical layer authentication techniques to enhance the security performance of wireless systems are proposed. The first technique exploits the inherent properties of CIR to achieve robust channel-based authentication. The second and third techniques utilize a long-range channel predictor and additional multipath delay characteristics, respectively, to enhance the CIR-based authentication. The fourth technique exploits the advantages of AF cooperative relaying to improve traditional channel-based authentication. The last technique employs an embedded confidential signaling link to secure the legitimate transmissions in OFDM systems

How Does Fundraiser-claimed Product Innovation Influence Crowdfunding Outcomes

The crowdfunding platforms have always been dedicated to supporting and inspiring innovative, and creative campaigns. However, limited research has been done to examine the fundraiser-claimed product innovation in campaign descriptions and its relation to fundraising performance. In this paper, we aim to tackle this important yet understudied problem. More specifically, we adopt a deep learning-based approach to extract sentences that contain innovation claims from project descriptions. We then conduct an empirical analysis to study the relation between fundraiser-claimed product innovation and crowdfunding performance by using a large sample consisting of 11,521 projects collected from Kickstarter across 4 project categories. Findings show a statistically significant association between fundraiser-claimed product innovation and crowdfunding performance. Additionally, the number of focal project innovation claims has a curvilinear relationship (inverted ‘U’ shape) with crowdfunding performance. Our study contributes to both product innovation detection and crowdfunding literature by demonstrating the association between product innovation presentation and crowdfunding performance

Enzymatic preparation and facile purification of medium-chain, and medium- and long-chain fatty acid diacylglycerols

High purity diacylglycerols (DAG) rich in medium-chain fatty acid diacylglycerols (MCD) and medium- and long-chain fatty acid diacylglycerols (MLCD) were prepared via the enzymatic esterification of monoacylglycerols (MAG) with caprylic acid followed by molecular distillation (MD), solvent fraction and low-temperature centrifugation. The content of DAG in the crude product was 44.8 ± 0.1%, under the selected esterification conditions, which were MAGs/caprylic acid mole ratio of 1:3, reaction temperature of 65 °C, reaction time of 30 min and enzyme load of 5 wt%. Subsequently, the one-step MD and solvent fraction in methanol/ethanol increased the DAG content to 61.3 ± 0.8%. Eventually, the product containing 86.6 ± 0.6% of DAG with 39.3 ± 1.3% of MCD and 47.3 ± 0.6% of MLCD was obtained by the methanol crystallization at 0 °C with a water content of 9 wt% and a 1:3 ratio of glycerides/methanol (v/v) followed by the centrifugation separation at 0 °C.The financial support from the National Natural Science Foundationof China under grants 31671781, 31371785 and 31501443, theNational Key Research and Development Program of China under grant2017YFD0400200, the Department of Science and Technology ofGuangdong Province under grants 2017B090907018 and2014A010107014, and the Bureau of Science and Information ofQingyuan under grant 2016D008 are gratefully acknowledged

Physical Layer Authentication Enhancement Using Maximum SNR Ratio Based Cooperative AF Relaying

Physical layer authentication techniques developed in conventional macrocell wireless networks face challenges when applied in the future fifth-generation (5G) wireless communications, due to the deployment of dense small cells in a hierarchical network architecture. In this paper, we propose a novel physical layer authentication scheme by exploiting the advantages of amplify-and-forward (AF) cooperative relaying, which can increase the coverage and convergence of the heterogeneous networks. The essence of the proposed scheme is to select the best relay among multiple AF relays for cooperation between legitimate transmitter and intended receiver in the presence of a spoofer. To achieve this goal, two best relay selection schemes are developed by maximizing the signal-to-noise ratio (SNR) of the legitimate link to the spoofing link at the destination and relays, respectively. In the sequel, we derive closed-form expressions for the outage probabilities of the effective SNR ratios at the destination. With the help of the best relay, a new test statistic is developed for making an authentication decision, based on normalized channel difference between adjacent end-to-end channel estimates at the destination. The performance of the proposed authentication scheme is compared with that in a direct transmission in terms of outage and spoofing detection

Strain Distribution Evaluation of Rat Tibia under Axial Compressive Load by Combining Strain Gauge Measurement and Finite Element Analysis

This study is aimed at providing an effective method for determining strain-load relationship and at quantifying the strain distribution within the whole tibia under axial compressive load on rats. Rat tibial models with axial compressive load were designed. Strains in three directions (0°, 45°, and 90°) at the proximal shaft of the tibia were measured by using a strain gauge rosette, which was used to calculate the maximum and minimum principal strains. Moreover, the strain at the midshaft of the tibia was measured by a single-element strain gauge. The slopes of the strain-load curves with different peak loads were calculated to assess the stability of the strain gauge measurement. Mechanical environment in the whole tibia by the axial compressive load was quantified using finite element analysis (FEA) based on microcomputed tomography images. The von Mises elastic strain distributions of the whole tibiae were evaluated. Slopes of the strain-load curves showed no significant differences among different peak loads (ANOVA; P>0.05), indicating that the strain-load relationship obtained from the strain gauge measurement was reasonable and stable. The FEA results corresponded to the experimental results with an error smaller than 15% (paired Student’s t-test, P>0.05), signifying that the FEA can simulate the experiment reasonably. FEA results showed that the von Mises elastic strain was the lowest in the middle and gradually increased to both sides along the lateral direction, with the maximal von Mises elastic strain being observed on the posterior side under the distal tibiofibular synostosis. The method of strain gauge measurements and FEA used in this study can provide a feasible way to obtain the mechanical environment of the tibiae under axial compressive load on the rats and serve as a reference for further exploring the mechanical response of the bone by axial compressive load