Search Results (15)

Traditional over-the-air (OTA) testing typically requires the device under test (DUT) to be positioned at the geometric center of the anechoic chamber, which limits the flexible evaluation of modern wireless terminals. Although the spherical vector wave (SVW) method provides a rigorous electromagnetic mode expansion, its direct use in eccentric testing scenarios is prone to coefficient-domain overfitting. In the conventional coefficient-domain formulation, the increased involvement of high-order evanescent modes can lead to overfitting of physically insignificant coefficients, resulting in unstable and oscillatory reconstruction. To explain this behavior, an analytical periodicity model is developed and validated by numerical simulations, showing good agreement across all tested configurations. To overcome this limitation, this paper develops a unified 3D eccentric spatial–spectral composite operator for eccentric field synthesis by directly incorporating the three-dimensional offset into the field evaluation process. The proposed operator maps probe excitation weights to the translated 3D local test-zone field samples, thereby reformulating the synthesis problem from coefficient-domain fitting to field-domain matching. This field-domain formulation naturally downweights high-order modal components with negligible local-field contributions, thereby improving numerical stability. Numerical simulations in a 3D multi-probe anechoic chamber (MPAC) demonstrate that, under significant eccentric conditions, the conventional SVW method essentially fails, while the plane wave synthesis (PWS) method achieves less accurate reconstruction than the proposed scheme. In contrast, the proposed scheme maintains stable, oscillation-free reconstruction and consistently outperforms PWS by 5 to 15 dB across all evaluated scenarios. This work provides a promising solution for flexible 3D OTA evaluation of large-scale wireless terminals. Full article

In the current context, classic software licensing and protection mechanisms based exclusively on host application checks can be circumvented by patching, emulation and replay attacks in user-controlled environments. This paper presents an adaptive hardware key implemented on the ESP32-S3 platform, which externalizes sensitive decisions and cryptographic operations from the host application to a dedicated device. The solution combines a device-anchored root of trust (secure boot and flash memory encryption), a PKI-verifiable identity (Public Key Infrastructure X.509 certificate and digital signatures as proof of ownership), hierarchical key derivation to avoid static secrets and the establishment of an authenticated encrypted session for all essential data exchanges. User access is conditioned by three-factor authentication (PIN—Personal Identification Number, TOTP—Time based One Time Password and USB physical presence) and a “code-in-dongle” mechanism, in which the important logic runs on the device and the application receives tokens with limited duration. Experimental validation demonstrates correct provisioning, secure session establishment, negative brute-force testing, as well as lifecycle support via signed OTA (Over-The-Air) with anti-rollback and encrypted backup/recovery. Build reports indicate a balanced flash distribution and available DIRAM (Data/Instruction RAM) margin, while IRAM (Instruction RAM) saturation (99.99%) reflects a normal architectural behavior of the ESP32-S3 unified memory model rather than a capacity constraint. Full article

The Internet of Things (IoT) technology has grown rapidly over the past decade, resulting in deployments of thousands of IoT devices around the world. Then, managing firmware updates for these numerous devices poses significant challenges. Firmware updates face issues such as version rollback, modified firmware files, and potential man-in-the-middle (MITM) attacks, highlighting the need for a secure over-the-air (OTA) firmware update mechanism. In this paper, we propose an automated OTA firmware update mechanism, integrated with continuous integration (CI) and continuous delivery (CD) to ensure trusted sources for firmware origins. It offers security, error handling during firmware updates, and monitoring of the update process. For evaluations, we implemented the proposal with the SEMAR IoT application server that has been implemented in our previous studies. Then, we verified the integrity and authentication, measured the performance and resource utilization, and performed benchmarking tests to assess the efficiency. The results demonstrate that the proposal is sufficiently reliable and efficient. Full article

Managing firmware updates in large-scale IoT deployments presents significant challenges regarding security, reliability, and operational cost. This paper presents the design and implementation of “IOTAfy”, a new, open-source, comprehensive, Over-The-Air (OTA) firmware management platform tailored for ESP32-based IoT devices. “IOTAfy” distinguishes itself through its efficient database design and asynchronous update mechanism, enabling scalable deployments. The proposed system comprises a device-side solution for ESP32 microcontrollers, incorporating a custom bootloader, an application firmware boilerplate code, and an OTA library, alongside a web-based management interface developed using PHP, SQLite3, and Bootstrap. This integrated approach facilitates secure and reliable OTA application firmware updates. The platform enables centralized monitoring of device status, scheduled firmware updates, and robust version control for multiple IoT devices. OTA updates are implemented directly on the ESP32, eliminating the need for physical access or intervention. The web interface provides administrators with features for group upgrades, rollback capabilities, real-time update status monitoring and alerts. The system was tested in a controlled environment with 50 ESP32 devices, achieving a 98% success rate for OTA updates. The results demonstrate the potential for significant cost savings and reduced maintenance time compared to manual update processes. The architecture of the “IOTAfy” platform, leveraging an efficient database design and asynchronous update mechanism, facilitates scalability to hundreds or thousands of devices. This work offers a practical and scalable solution for managing firmware in large-scale IoT deployments, contributing to enhanced device security, improved reliability, and reduced operational expenditures. Full article

The Advanced Encryption Standard (AES) symmetric encryption algorithm plays a crucial role in data encryption. To address the limitations of the fixed Substitution-box (S-box) and static key expansion strategy in AES. This paper proposes an improved AES scheme that integrates a dynamic S-box structure with a key expansion mechanism based on dynamic perturbations. The dynamic S-box is generated by selecting affine transformation pairs and irreducible polynomials, and its cryptographic properties are tested in SageMath9.3 to obtain a set of S-boxes superior to the standard AES. In the key expansion process, the perturbation values generated by the hash function will be incorporated into the round key generation process to reduce the correlation between round keys. The improved AES algorithm, when applied to Over-the-Air (OTA) systems, not only achieves significant savings in storage resources of in-vehicle Electronic Control Units (ECUs) but also enhances the security of OTA communications. Furthermore, it consumes only a small amount of ECU computational resources, thereby effectively meeting the lightweight requirements of in-vehicle electronic control units. Full article

Over-the-air (OTA) testing is crucial for optimizing wireless performance of 5G smart watches and improving their user experience. However, the current required test time is so long that it is almost impossible to complete the entire OTA testing without recharging and repositioning, which is unacceptable for the industry. Therefore, test-time reduction is significant. The objective of this work is to optimize measurement grids for OTA testing of 5G smart watches, which balance accuracy with efficiency. In this research, passive patterns from a typical 5G commercial smart watch are measured at different bands as reference patterns, which represent general radiation properties of 5G commercial smart watches. The effect of various coarse grids on OTA testing precision is characterized quantitatively by analyzing their accuracy in reconstructing reference patterns. The related measurement uncertainty (MU) terms are then evaluated and determined quantitatively based on statistical analysis. According to the derived MU limits for grid configurations, reducing grid points from currently required 62 (30/30) to 26 (45/45), and from 266 (15/15) to 62 (30/30) could save roughly 60% and 75% of the test time, respectively, with an uncertainty increase of 0.1 dB for both Total Isotropic Sensitivity (TIS) and Total Radiated Power (TRP) testing, which is considered acceptable. Furthermore, the feasibility of the proposed MU analysis and recommended grids have been experimentally verified. Full article

Although the U.S. makes up only 5% of the global population, it accounts for approximately 31% of public mass shootings. Gun violence and mass shootings not only result in loss of life and injury but also inflict lasting psychological trauma, cause property damage, and lead to significant economic losses. We recently developed and published an embedded system prototype for detecting gunshots in an indoor environment. The proposed device can be attached to the walls or ceilings of schools, offices, clubs, places of worship, etc., similar to smoke detectors or night lights, and they can notify the first responders as soon as a gunshot is fired. The proposed system will help to stop the shooter early and the injured people can be taken to the hospital quickly, thus more lives can be saved. In this project, a new custom dataset of blank gunshot sounds is recorded, and a deep learning model using both time and frequency domain features is trained to classify gunshot and non-gunshot sounds with 99% accuracy. The previously developed system suffered from several security and privacy vulnerabilities. In this research, those vulnerabilities are addressed by implementing secure Message Queuing Telemetry Transport (MQTT) communication protocols for IoT systems, better authentication methods, Wi-Fi provisioning without Bluetooth, and over-the-air (OTA) firmware update features. The prototype is implemented in a Raspberry Pi Zero 2W embedded system platform and successfully tested with blank gunshots and possible false alarms. Full article

An end-to-end testbed for In-phase and Quadrature (I/Q) Imbalance (IQI) communication systems based on Software-Defined Radio (SDR) is presented. The scenario under consideration is a Single-Input–Single-Output (SISO) single-carrier communication where the transmitter is heavily affected by IQI, whose effects are mitigated through digital signal processing at the receiver. The presented testbed is highly configurable, enabling the testing of different communication and IQI parameters. Crucial insights into the practical implementation of IQI mitigation techniques, specifically through the use of asymmetric signaling at the receiver, are provided. Initially, a detailed description of the mathematical framework is given. This framework serves as the foundation for the subsequent discussion on system implementation, effectively bridging the gap between research on IQI mitigation and its practical application in single-carrier architectures. Over-The-Air (OTA) Symbol Error Rate (SER) measurements for different constellations validate the receiver design and implementation. The source code of the presented testbed is publicly available. Full article

To ensure high-reliability communication in healthcare networks, this paper presents a smart gateway system that includes an angle-of-arrival (AOA) estimation and a beam steering function for a small circular antenna array. To form a beam toward healthcare sensors, the proposed antenna estimates the direction of the sensors utilizing the radio-frequency-based interferometric monopulse technique. The fabricated antenna was assessed based on the measurements of complex directivity and the over-the-air (OTA) testing in Rice propagation environments using a two-dimensional fading emulator. The measurement results reveal that the accuracy of the AOA estimation agrees well with that of the analytical data obtained through the Monte Carlo simulation. This antenna is embedded with a beam steering function employing phased array technology, which can form a beam spaced at 45° intervals. The ability of full-azimuth beam steering with regard to the proposed antenna was evaluated by beam propagation experiments using a human phantom in an indoor environment. The received signal of the proposed antenna with beam steering increases more than that of a conventional dipole antenna, confirming that the developed antenna has great potential of achieving high-reliability communication in a healthcare network. Full article

Communication reliability is a challenging requirement, which implies the need for over-the-air (OTA) testing. Reverberation chambers (RCs) are widely used for OTA tests in various fields. Due to their properties, such as inherent radio channel emulation or the arbitrary orientation of the equipment under test (EUT) in the test volume, they can be used as advantageous test environments for wireless products in the field of industrial manufacturing automation, such as for the IO-Link Wireless (IOLW) standard. In this paper, the different OTA sensitivity test procedures total isotropic sensitivity (TIS), average fading sensitivity (AFS) and mean channel packet error (MCPE) method, which is based on the fundamental channel model of the wireless standard, are described and evaluated in various variants. A core aspect of the proposal is the impact of the possible use of frequency hopping of the wireless equipment under test. The respective advantages and disadvantages are shown. Overall, TIS proves to be a suitable alternative for IOLW OTA sensitivity testing. Full article

For Multiple-input, multiple-output (MIMO) user equipment (UE), over-the-air (OTA) testing of radiated multi-antenna reception performance is crucial to guarantee actual network performance and is mandatory in North America, Europe and China. For 5G MIMO OTA, 3GPP has specified the clustered delay line (CDL) channel models as the reference channel models, which present higher order and directivity than those of 4G. Therefore, which kinds of performance metrics and environmental conditions are feasible and necessary to better characterize the MIMO performance should be studied. In this paper, MIMO OTA measurement results of different figures of merits (FoMs) under both UE noise-limited and interference-limited environmental conditions have been compared and discussed, respectively. In addition, the impact of different channel models on MIMO OTA throughput performance as well as the variance per azimuth are compared. Based on the analysis, Peak-Null can better reflect the difference between the 12 azimuth positions than Variance. Total Radiated Multi-antenna Sensitivity (TRMS) under both channel models presents nearly the same performance trends at different thresholds. On the contrary, MIMO Average Radiated SIR Sensitivity (MARSS) exhibits a high dependence on channel models. The MARSS under UMi channel model shows a much smaller performance variation between UEs than UMa channel model. TRMS under 3GPP UE noise-limited environmental condition exhibits a stronger ability to distinguish between good and bad performing devices than that of MARSS under CTIA interference-limited environmental condition. The discrepancy can reach 4 dB at most. This discrepancy does not come from different average manners between TRMS and MARSS, but originates from environmental condition itself. Therefore, it is proposed to adopt TRMS under UE noise-limited environmental condition as the unique or baseline test condition in 5G FR1 MIMO OTA. Peak-Null can be considered as a secondary FoM to characterize the variance per azimuth. Full article

This paper presents an over-the-air testing method in which a full-rank channel matrix is created for a massive multiple-input multiple-output (MIMO) antenna system utilizing a fading emulator with a small number of scatterers. In the proposed method, in order to mimic a fading emulator with a large number of scatterers, the scatterers are virtually positioned by rotating the massive MIMO antenna. The performance of a 64-element quasi-half-wavelength dipole circular array antenna was evaluated using a two-dimensional fading emulator. The experimental results reveal that a large number of available eigenvalues are obtained from the channel response matrix, confirming that the proposed method, which utilizes a full-rank channel matrix, can be used to assess a massive MIMO antenna system. Full article

This paper presents a multiple-input, multiple-output (MIMO) antenna system with the ability to perform full-azimuth beam steering, and with the aim of realizing greater than 20 Gbps vehicular communications. The MIMO antenna described in this paper comprises 64 elements arranged in a daisy chain array structure, where 32 subarrays are formed by pairing elements in each subarray; the antenna yields 32 independent subchannels for MIMO transmission, and covers all communication targets regardless of their position relative to the array. Analytical results reveal that the proposed antenna system can provide a channel capacity of more than 200 bits/s/Hz at a signal-to-noise power ratio (SNR) of 30 dB over the whole azimuth, which is equivalent to 20 Gbps for a bandwidth of 100 MHz. This remarkably high channel capacity is shown to be due to two significant factors; the improved directivity created by the optimum in-phase excitation and the low correlation between the subarrays due to the orthogonal alignment of the array with respect to the incident waves. Over-the-air (OTA) experiments confirm the increase in channel capacity; the proposed antenna can maintain a constant transmission rate over all azimuth angles. Full article

A high channel consistency subarray of plane-wave generators (PWG) is described for fifth-generation (5G) base station (BS) over-the-air (OTA) testing. Firstly, the variation of the near field radiation characteristics of the subarray based on the feed amplitude and phase errors of the traditional power divider network is analyzed. The recommended amplitude and phase errors between channels are given. After that, a novel subarray which combines four pyramidal horn antennas and a compact 1:4 waveguide power divider is designed. The optimized perfectly symmetrical zigzag waveguide transmission lines are used to realize consistent power allocation among antenna elements. No intermediate pins are employed, which avoids the significant deterioration of channel consistency caused by assembly errors. The size of the subarray is 4.89 λ₀ × 4.97 λ₀ × 1.23 λ₀ (λ₀ is the working wavelength corresponding to the subarray center frequency at 3.5 GHz). The VSWR < 1.5 impedance bandwidth covers 3.4 GHz to 3.6 GHz. The amplitude difference between the four elements of the subarray is less than 0.5 dB, and the phase difference is less than 3°. The simulated and measured results agree well in this design. Full article

The last decade has witnessed a significant reduction in prices and an increased performance of electronic components, coupled with the influence of the shift towards the generation of open resources, both in terms of knowledge (open access), programs (open-source software), and components (open hardware). This situation has produced different effects in today’s society, among which is the empowerment of citizens, called makers, who are themselves able to generate citizen science or build assembly developments. Situated in the context described above, the current study follows a Do-It-Yourself (DIY) approach. In this way, it attempts to define a conceptual design of an Internet of Things (IoT) node, which is reproducible at both physical and behavioral levels, to build IoT nodes which can cover any scenario. To test this conceptual design, this study proposes a sensorization node to monitor meteorological phenomena. The node is called SEnviro (node) and features different improvements such as: the possibility of remote updates using Over-the-Air (OTA) updates; autonomy, using 3G connectivity, a solar panel, and applied energy strategies to prolong its life; and replicability, because it is made up of open hardware and other elements such as 3D-printed pieces. The node is validated in the field of smart agriculture, with the aim of monitoring different meteorological phenomena, which will be used as input to disease detection models to detect possible diseases within vineyards. Full article