A compact μ45° dual-polarized broadband antenna array is proposed in this letter for base stations. For the sake of structural simplicity, low profile and easy of mass production, printed dipoles are adopted as the dual-polarized antenna element. To achieve the broadband performance, radiators are designed to be spline-edged bowties, and they are fed by tapered transmission lines. Moreover, to improve the symmetry and stability of the radiation pattern, Pawsey stub baluns are used to balance the antenna structure. Finally, an 8-element antenna array prototype backed by a folded reflector is fabricated and measured. The compact antenna array has a broad bandwidth of 68% (1.427-2.9 GHz) with a voltage standing wave ratio less than 1.5 and stable radiation properties to provide international mobile telecommunication services over 2G/3G/LTE systems and L and S bands released recently.

Cyber security has always been an important issue in the Internet of Everything topic. In the physical layer of the Internet, specific emitter identification (SEI) technology is widely researched as a simple and effective intrusion prevention technology. Existing SEI research only focused on radio frequency (RF) signals from a single receiver. However, in real scenes such as the Industrial Internet of Things (IIoT), vehicle-to-everything applications, and intelligent sensing systems, etc., RF signals are received from different types of sensors deployed at different locations. Therefore, this paper proposes a multisource heterogeneous SEI (MH-SEI) method and proposes a multi-source heterogeneous attention-based feature fusion network (MHAFFN) to achieve excellent identification performance. The proposed MHAFFN utilizes a multi-channel convolutional network as the RF fingerprinting (RFF) extraction module for multisource heterogeneous RF signals and equips an attention-based RFF fusion module to obtain mixed RFF for the automatic classifier. The experimental results show that the identification accuracy of MHAFFN is 99.196% in a perfect environment. Furthermore, robustness verification has proved that MHAFFN keeps advantages in noisy environments. Through fault tolerance mechanism verification experiment, it is proved that MHAFFN is able to work stably in real-world complex scenarios.

In this communication, a low-profile ultra-wide band (UWB) antenna is designed, fabricated and measured for TV white space devices (TVWSDs). Starting from a simple annular ring, the proposed design procedure is guided by the characteristic mode analysis (CMA). Firstly, a closed-form estimation to the resonant frequencies of the first two characteristic modes for the annular ring structure are provided. Then the annular ring is modified to introduce more characteristic modes resonating within the interested spectrum. To excite these modes and to achieve a wideband antenna covering the whole ultra-high frequency (UHF) TV spectrum, the feeding structure is also carefully designed and refined. Finally, a prototype is fabricated and measured to verify its UWB performance, and radiation patterns at different frequencies are presented to prove the switching of dominating resonating modes. The analyses and performance evaluation show that the proposed antenna is a strong contender to be used for TVWSDs. Furthermore, thanks to the simplicity of tuning and controlling modal resonant frequencies, this procedure can be flexibly applied to various antenna designs.

ADS-B has been widely deployed on aircraft to facilitate aviation information exchange and improve air traffic safety. However, its broadcast nature and lack of security considerations like encryption and authentication have caused the counterfeit of automatic-dependent surveillance-broadcast (ADS-B) messages to be straightforward. Flooding forged messages to legitimate aircraft, Denial-of-Service (DoS) attacks threaten flight security severely. In this article, we propose a practical security solution against DoS attacks on ADS-B based on high-precision timestamp and position information. The solution achieves high feasibility and reliability by accommodating measurement errors of physical quantities. Besides, it preserves ADS-B frame size and ensures efficient computation in frame generation and verification. Comprehensive security analyses demonstrate robust filtrations of the proposed solution on malicious messages from DoS adversaries with different capabilities. Further simulations on real-world aviation data exhibit significant defensive performance realized by the DoS-immune ADS-B security solution. Whether adversaries can only intercept ciphertext, or they have opportunities to acquire decrypted messages, all DoS attacks on ADS-B are successfully thwarted by the solution. Even for adversaries with victim aircraft location estimation capacity, the solution resists all DoS attacks transmitting less than 50 forged messages per second.