This paper is intended to help provide an introduction for EMC analysis, design and signal integrity assurance for wearable wireless biosignal sensors. First, a mechanism by which external electromagnetic field couple to the biosignal sensor circuit is explained in terms of common-mode to differential-mode conversion. Based on this, some noise quantification and suppression techniques for biosignal sensors are introduced. Next, focusing on reducing inter-symbol interference in wideband communications from the surface to the inside of the human body, a pre-emphasis technique which guarantee a balance between signal integrity improvement and signal-to-noise power degradation is proposed and proved useful.

This study proposes a numerical analysis method suitable for EMC evaluations of aircraft. By employing a detailed numerical model that replicates both the external shape and internal structures of an aircraft, combined with large-scale parallel FDTD analysis, the far-field radiation characteristics of a radio altimeter frequency band antenna mounted on the aircraft’s underside were evaluated. The results demonstrate that this approach achieves higher accuracy in EMI evaluations compared to conventional methods. Criteria for determining the appropriate cell size for EMC evaluations in the radio altimeter and 5G Sub-6 GHz frequency bands were also established. Additionally, the study highlights the effectiveness of large-scale FDTD analysis in accurately assessing unwanted radiation and EMI characteristics, such as cross-polarization and upward emissions, providing practical insights for advancing EMC evaluation techniques and aircraft system design.

This paper examines the generation of electromagnetic noise caused by coupling between normal mode (NM) and antenna mode (AM) in a two-conductor transmission line (TL). We employ telegraph equations based on electromagnetic potentials to analyze NM and AM. Through experimental observations and numerical simulations, we quantify the coupling effects that occur when transmission lines with differing mode impedances are connected. For detailed analysis of coupling noise mechanisms, three-dimensional electromagnetic potential simulations are conducted to observe the voltage and current distributions of NM and AM within the TLs. This study demonstrates that impedance matching of TLs requires the consideration of not only NM impedance but also coupling impedance.

The oblique-incidence characteristics of an electromagnetic wave absorber at 28 GHz, consisting of a conductive layer and a dielectric layer, were evaluated both analytically and experimentally. By optimizing the design of the conductive layer, it was confirmed that the reflection characteristics at oblique incidence were almost the same with and without metal backing. The reflection coefficient with increasing incident angle differed between TE- and TM-incident waves. Matching conditions (reflection coefficient -20 dB or less) were obtained in the angle range up to approximately 60° for the TE incident waves. An electromagnetic wave absorber without metal backing using this structure has advantages in terms of cost, weight, and flexibility in the millimeter-wave band.

Electrostatic discharge (ESD) damage evaluation methods for common mode choke (CMC) and ESD suppression devices are standardized in IEC 62228-5 Annex E and Annex F, respectively. The significant challenge associated with these tests is the difficulty in measuring the current waveform flowing through the input section of a device under test (DUT) and predicting the current in advance. In this study, we investigated an equivalent circuit model that enables prediction of the discharge current waveform flowing through the DUT in advance using SPICE without measurements. Specifically, we developed an equivalent circuit model consisting of a test board and an ESD gun for LTspice, and subsequently confirmed the validity of the model by comparing the measured output voltage waveforms of the test board with simulated ones. As a result, the simulation circuit model predicts the discharge current through the DUTs and their connected circuit within about 10-30% difference in the first peak voltage and rise time. While there is room for improvement in simulation accuracy from various perspectives, such as the test board and the ESD gun model, this suggests that the simulation circuit model is effective and that the approximate current waveform flowing through the CMC and ESD suppression devices can be predicted by circuit simulation without measurement.

In order to efficiently perform a redundant design that can simultaneously satisfy conflicting performance requirements and cover a wider range of design parameters, we investigated the relationship between the amount of ANN training data and the magnitude and accuracy of the interval solution range in multi-objective optimal design using an artificial neural network (ANN) model, with the target being the design of an electromagnetic interference (EMI) filter for a brush motor drive system. In this study, it was found that when the design parameters are at 2 levels, the maximum and minimum values, the amount of training data is very small but a range solution is still obtained though it is insufficient. Increasing the amount of training data increases the training time for the ANN and the number of false positives (FPs). However, since the possibility of FP occurring in the range solution is low, increasing the amount of training data to obtain a wide range solution is effective. Furthermore, since the training time increase significantly when the amount of training data is increased, this study concludes that 3 to 5 levels are effective.

ISO11451-5 was published in May 2023 as a vehicle immunity test standard limited to reverberation chambers. In this study, we have designed a new parallel-plate Transverse Electromagnetic (TEM) antenna compliant with a Transmission Line System (TLS) described in Annex E as an immunity test method from 10 kHz to Lowest Useable Frequency (LUF), a fabricated 1/4 scale reverberation chamber, evaluated electric field uniformity, and ascertained its effectiveness. Further, using a 1/4 vehicle scale model, we have compared this immunity test method using a parallel-plate TEM antenna with the conventional immunity test methods using a TLS and a biconical antenna at an Absorber Lined Shielded Enclosure (ALSE) to ascertain its effectiveness.

High-performance throughput is a critical issue in the hardware implementation of elliptic curve cryptography (ECC). This paper presents the construction of a high-speed ECC processor based on Mersenne-like prime fields. The subtractive form of the Radix-4 Karatsuba algorithm is introduced, along with a 2-level Karatsuba multiplier that eliminates the impact of bit-width expansion during iterations through pre-preprocessing. An improved Montgomery scalar multiplication algorithm is employed, allowing for the parallel execution of point addition and point doubling operations, effectively resisting SPA attacks. Computational steps are arranged rationally, and a scheduling scheme is proposed to maximize the efficiency of the computational units, thereby reducing the execution cycle of scalar multiplication operations. By adopting the aforementioned Karatsuba multiplier and improved Montgomery scalar multiplication scheduling scheme, the ECC processor for SM2 P256 field is implemented on the Virtex-7 FPGA platform, performing a scalar multiplication operation every 47us, utilizing 35.5k LUTs and 200 DSPs.

The eigenvalues in the Zakharov-Shabat problem for the nonlinear Schrödinger equation are invariant quantities with respect to the transmission distance. Therefore, optical eigenvalue modulation is expected to be a novel transmission scheme to overcome the Kerr nonlinearity limit in fiber optic communications. However, there is a concern that optical eigenvalues vary under dispersion fluctuations arising in the manufacturing process of the optical fiber. In this study, we investigate the effects of the dispersion fluctuation on the eigenvalue transmission, including that of multi-eigenvalues, through numerical simulations. For the modeling, we experimentally measure the dispersion distribution of a non-zero dispersion-shifted fiber (NZ-DSF) using the bidirectional optical time domain reflectometer (OTDR) method. The measurement result indicates that the count of dispersion fluctuation could be approximated by the Gaussian distribution. Hence, we investigate the three dependencies of eigenvalue variation: the number of eigenvalues, the standard deviation of dispersion fluctuation, transmission distance, and reference time. The simulation results indicate that multi-eigenvalue transmission was more sensitive to dispersion fluctuation than 1-soliton transmission. Moreover, the direction of the eigenvalue variation depends on the eigenvalue configurations. Nevertheless, the results show that the eigenvalue shift is sufficiently small even for the transmission of the 2-soliton solution in the dispersion fluctuation of practical fibers. However, in the case of the 4-soliton solution, dispersion fluctuations affect eigenvalue transmission under certain conditions.

As the IoT market expands, the use of multiple IoT devices and personal devices is rapidly increasing. With the increase in devices, WLAN technology to improve throughput is essential. IEEE 802.11be EHT is being standardized in Wi-Fi 7 with the goal of improving throughput. In particular, MLA is being proposed as a method to accommodate more devices and improve throughput at the MAC layer of IEEE 802.111be EHT. However, there is also a problem that one device can have multiple links, which leads to inter-link interference problem. In this paper, we propose a DCF operation method using MLA called a Data Division Transmission (DDT) method to mitigate the inter-link interference problem of MLD and improve throughput, which is the ultimate goal of IEEE 802.11be EHT. This method mitigates the inter-link interference problem by activating only one link in the adjacent frequency bands of 5 GHz and 6 GHz, and effectively utilizes the characteristics of multi-link and tri-band to improve throughput by dividing and transmitting data. A Markov chain model is presented to analyze the performance of the proposed DDT method, and the performance analysis is conducted considering the coexistence with legacy devices as MLD is introduced. The performance analysis shows that the proposed DDT method improves the throughput by up to 26 Mbps over the existing FT method and demonstrates stable coexistence with legacy devices.

Recently, the demand for data transfer with low loss and within permissible delays in wireless sensor networks that must be operated at low costs, e.g., for system control in smart factories, has increased. For such low-cost operations, it is essential to use the IEEE 802.11 standard; however, its random channel access makes it difficult to reduce frame transfer delays to permissible values. Orthogonal frequency-division multiple access (OFDMA) transmission, introduced by IEEE 802.11ax, enhances the feasibility of satisfying the demand because OFDMA transmission is performed by a sink in a centralized manner, and multiple frames are transferred simultaneously without collision. However, no OFDMA transmission methods have been proposed to suppress the transfer delays of aperiodically generated delay-bounded frames from source nodes to their sinks within permissible values, following the 802.11ax specification that OFDMA transmission is triggered when the sink obtains a transmission opportunity based on CSMA/CA. In this paper, we propose a delay-bounded frame transmission method with OFDMA to suppress frame transfer delays within permissible values while reducing frame loss. In this method, the start time of OFDMA transmission of delay-bounded frames is deferred within their permissible delays. This expects that new delay-bounded frames are generated during the deferral period, and more delay-bounded frames including the newly generated ones are transmitted without collision via OFDMA. Extensive simulation evaluations demonstrate that the proposed method transfers delay-bounded frames within their permissible values, where no samples exceed the deadlines among 10⁷ transfer trials. In addition, data frame loss is reduced compared with a representative related delay-aware OFDMA transmission method, which aims to minimize the average data upload time, and another benchmark that transfers delay-bounded frames with maximum prioritization and efficiency.

In terminal cooperative communication, the existing relay selection schemes with relay buffer do not consider the source data size and the transmit sequence of source packets, and are not suitable for parallel multi relay selection scenarios. Therefore, this paper proposes a parallel multi relay selection method based on deep reinforcement learning (DRL), which comprehensively considers the throughput of source-relay link and relay-destination link, and the buffer status of all optional relays, uses LSTM to predict the source data size of the next moment and divides the source data into appropriately sized packets, then uses DRL to perform parallel multi relay selection. In addition, in the process of relay selection, the sequence of source data packets, the complete process of packet forwarding, and the delay of packet forwarding are also considered. Therefore, the proposed parallel multi relay selection method based on DRL can achieve dynamic selection of multiple relays based on the number of divided data packets. Simulation results show that, compared with Max-Ratio method, proposed method can achieve higher throughput under the constraints of forwarding times and packet transmitting delay.

In this paper, we propose an asynchronous non-orthogonal multiple access (ANOMA) downlink scheme with transmit equalization in frequency-selective channels. In the proposed ANOMA scheme, an intentional symbol timing offset between multiplexed symbols is introduced to reduce inter-user interference (IUI). In addition, finite impulse response filters are employed at the transmitter to reduce inter-symbol interference, thereby simplifying the receiver configuration. We present a filter design method based on signal-to-interference-plus-noise ratio maximization. We show that the IUI of the proposed ANOMA scheme is smaller than that of a conventional synchronous NOMA. Simulation results show that the proposed ANOMA scheme achieves a higher achievable rate region than a conventional synchronous NOMA. Moreover, we demonstrate that the proposed ANOMA scheme achieves a lower peak-to-average-power ratio and greater resilience for the carrier frequency offset than orthogonal frequency-division multiplexing based NOMA.

Efficient acquisition of direct sequence spread spectrum (DSSS) signal is crucial under high dynamics and low signal-to-noise ratio (SNR). The current non-search acquisition method based on keystone transform avoids the problem of a sharp increase in computational complexity of the frequency search assisted methods at high dynamic correction accuracy, yet the computational complexity remains high. This paper proposes a low-complexity non-searching first-order dynamic DSSS signal acquisition method, which avoids the calculation of invalid dynamic correction range while ensuring that the frequency offset acquisition range remains unchanged. Specifically, by assuming that the relative delay caused by dynamics remains constant in each data symbol period, and converting the dynamic correction problem into a delay correction problem, the frequency offset acquisition range and the dynamic correction range are decoupled. Then, we analyze the connection between the proposed method and the existing non-search acquisition method Keystone DBZP. Finally, the computational complexity of the proposed method is derived and compared with other methods. Simulation results are provided to illustrate the effectiveness of the proposed method.

The spatial diversity has long been recognized as a powerful technique to mitigate the multipath fading effect and to improve the signal transmission quality (and hence the capacity of wireless systems). Joint transmit-receive diversity (JTRD), which utilizes transmit diversity and receive diversity jointly at both transmitter and receiver, is expected to further enhance the capacity of wireless systems. This paper provides a comprehensive analysis and evaluation of single/multi-user JTRD. Firstly assuming single-user transmission, the principle of JTRD is presented. The relationship between suboptimal JTRD and optimal JTRD is given. Optimal JTRD is shown to be equivalent to maximum eigenmode transmission. A recursive solution method is developed for determining optimal JTRD weight vectors. Received signal-to-noise ratio (SNR) analysis of optimal/suboptimal JTRD is also presented to show that the fading correlation is not always a negative factor in a strongly asymmetric MIMO channel. Then, an incorporation of JTRD into multi-user MIMO communications is presented. Zero-forcing-based precoder is designed to remove multi-user interference. Expressions for the received SNR of uplink and downlink transmissions are presented. Two types of multi-user JTRD are shown to be equivalent to hybrid beamforming and full digital beamforming. Also in this paper, user and sum capacities achievable by single/multi-user JTRD in Rayleigh faded MIMO channels are evaluated using Monte-Carlo numerical computation method to confirm the theoretical findings.

This paper proposes a scheme to model the energy consumption of a long range wide area network (LoRaWAN) node based on the results of outdoor field experiments by considering regional smart agriculture as a use case for IoT. In particular, we derive an experimental approximation formula to estimate the battery lifetime of a LoRaWAN node by introducing parameters such as the spread factor and payload length. The validity of the proposed scheme is demonstrated by confirming that the results obtained using the approximate formula Concur with the experimental and theoretical results, regardless of the node state and spread factor. Furthermore, we demonstrate that the proposed approximate formula can be used to identify the current consumption value in the sleep state that must be achieved to achieve the desired battery lifetime. Finally, we evaluate energy efficiency performance using the proposed approximate formula and show the validity of the results.

Carrier loops using non-linear Kalman filters are effective for high-dynamic Global Navigation Satellite System (GNSS) tracking but are sensitive to data modulation and typically require navigation data (NavData) assistance. We propose a NavData-tolerant Extended Kalman Filter (NavEKF) carrier loop that accommodates data modulation and is applicable to various user dynamics, including high-dynamic scenarios. Simulation results indicate that the NavEKF outperforms the Kalman filter (KF)-based carrier loop with the Costas phase discriminator, enhancing tracking thresholds by 5 dB in high-dynamic and 1.5 dB in static conditions. Its independence from data aid broadens its application range compared to EKF.