Earticle

최근, 무선 통신 기술을 활용하여 스마트팜 환경을 개선하고자 하는 연구가 지속되고 있다. 본 논문에서는 노지 스마트팜 환경에서 발생하는 문제점에 대해 소개하고, 이들을 해결하기 위한 통신 기술적 고려사항을 다루고 자 했다. 노지 스마트팜 환경에 적용하기 위한 후보 기술로 LoRa, Sigfox, NB-IoT, WiFi를 선정했고, 현재 사용되 고 있는 국내 스마트팜 기술의 문제점 및 방향성을 기반으로 설치 비용, 통신 범위, 데이터 전송 속도, 배터리 수명, 가격 등을 고려하여 각각의 후보 기술을 분석하여, 최종적으로 LoRa 기술이 가장 적합한 것으로 판단했다. 자세한 기술적 분석을 위해 본 논문에서는 LoRa의 물리 계층과 Medium Access Control (MAC) 계층 기술, 그리고 보 안에 대해 소개하였고, 특히 물리 계층의 변조기법, MAC 계층에서의 Class (Class A, B, C) 기반 프로토콜 동작 방법, 그리고 LoRa 버전별 보안 아키텍처에 대해 기술했다.

Recently, there have been increasing interests in researches to apply wireless communication technologies for smart farm. This paper introduces the problems in the smart farm for the outdoor culture and technical considerations to solve the problems. As candidate technologies, this paper selects LoRa, Sigfox, NB-IoT, and Wi-Fi and then determines that LoRa is a suitable technology based on the CAPEX, coverage, transmission rate, battery, and the price. To provide technical analysis, this paper introduces technologies related to the physical and medium access control (MAC) layers as well as the security. Specifically, this paper includes the modulation technology in the physical layer, Class (Class A, B, and C) based protocol operations in MAC layer, and security architecture based on the LoRa version.

In this study, we investigate the physical layer secrecy performance of RF energy harvesting (EH) networks over Rayleigh fading channels. The RF-EH system considered here consists of one power transfer station, one source, one destination, and multiple passive eavesdroppers. The source harvests energy from the power transfer station and transmits the information to the destination by using a time switching-based relaying protocol. The eavesdroppers try to extract the transmitted information without an active attack. By using the statistical characteristics of the signal-to-noise ratio (SNR), the exact closed-form expressions of the existence probability of the secrecy capacity and the secrecy outage probability are derived. Further, we analyze the secrecy performance of the system with respect to various system parameters, such as the location of the system elements and the number of eavesdroppers. Finally, the equivalent Monte Carlo simulation results are provided to confirm the correctness of our calculations.

OFDM-based cognitive radio networks suffer from high sidelobe emissions, leading to adjacent interference and potential security vulnerabilities. This paper introduces a Whale Optimization Algorithm (WOA)-based cancellation carrier (CC) approach for sidelobe suppression. Unlike conventional fixed-amplitude methods, the proposed framework adaptively optimizes CC amplitudes under power constraints to minimize total sidelobe energy (TSE). Simulation results show significant improvements: Peak Sidelobe Level (PSL) reduces from -41.48 dB to -57.1 dB, TSE drops from -57.60 dB to -80 dB, and Adjacent Channel Leakage Ratio (ACLR) approaches zero, while maintaining stable Bit Error Rate (BER) and improved Peak-to-Average Power Ratio (PAPR). These improvements enhance spectral efficiency and improve physical-layer robustness by reducing spectral leakage, which may limit susceptibility to eavesdropping, jamming, and spoofing.

In this article, we introduce physical-layer security enhancement technique based on artificial noise for secure device-to-device (D2D) communications within a platoon in vehicular platooning networks. In particular, we consider a scenario that two D2D-enabled platoons are on the same way. All the vehicles in one platoon are used to generate artificial noise to enhance the secrecy of D2D communications within the other platoon against information leakage to a potential eavesdropping vehicle. We propose artificial noise generation strategies by the platoon according to the assumption on channel state information (CSI): full-CSI and partial CSI assumptions. We further analyze the effect of artificial noise depending on the relationship between the number of vehicles in two platoons. We finally evaluate the performance of our proposed schemes in terms of secrecy rate through extensive simulations and provide useful intuitions for secure platooning.

In this paper, we discuss physical layer security techniques in downlink networks, including eavesdroppers. The main objective of using physical layer security is delivering a perfectly secure message from a transmitter to an intended receiver in the presence of passive or active eavesdroppers who are trying to wiretap the information or disturb the network stability. In downlink networks, based on the random feature of channels to terminals, opportunistic user scheduling can be exploited as an additional tool for enhancing physical layer security. We introduce user scheduling strategies and discuss the corresponding performances according to different levels of channel state information (CSI) at the base station (BS). We show that the availability of CSI of eavesdroppers significantly affects not only the beamforming strategy but also the user scheduling. Eventually, we provide intuitive information on the effect of CSI on the secrecy performance by considering three scenarios: perfect, imperfect, and absence of eavesdropper's CSI at the BS.

In this paper, we mathematically analyze bit-error rate (BER) and diversity order of physical-layer network coding (PNC) scheme in the two-way relay channel (TWRC) under the assumption of multiple antennas at relay node. We assume the quadrature phase shift keying (QPSK) modulation for simple data transmission in IoT applications, and max?min transmit antenna selection (TAS) scheme in the broadcast (BC) phase for achieving full diversity gain. In particular, we obtain the upper bound of BER at the multiple access (MA) phase, while deriving the exact BER performance at the BC phase. To the best our knowledge, the mathematical analysis in this paper is the first analytical results in the literature. Through computer simulations, the analytical results are validated.

Deep learning (DL) has exhibited great potential in communication systems. Recent advances in DL-based physical-layer techniques have shown that the communication system can be modeled as an autoencoder (AE), which performs end-to-end learning tasks. In this article, we investigate an AE-based deep learning framework for physical-layer security where multiple transmitters send their own data to a common receiver under an eavesdropping scenario (i.e., Gaussian multiple access wiretap channel). We have newly designed an integrated loss function with respect to secrecy performance in terms of symbol error rate among multiple users. Further, we verify that our training approach based on the proposed loss function can achieve better secrecy performance compared with the conventional training one.

Background Osteoporosis (OP) is a bone disease caused by a decrease in bone mineral density (BMD). OP is common in women because BMD gradually decreases after age 35. OP due to decreased BMD is highly likely to cause fatal traumatic injuries such as hip fracture. Purpose The purpose of this study was developed and evaluated a multi-layer perceptron neural network model that predicts OP using physical characteristics and activity factors of adult women over the age of 35 whose BMD begins to decline. Study design Cross-sectional study. Methods Data from KNHANES were used to develop a multi-layer perceptron model for predicting OP. Data preprocessing included variable selection and sample balancing, and LASSO was used for feature selection. The model used 5 hidden layers, dropout and batch normalization and was evaluated using evaluation scores such as accuracy and recall score calculated from a confusion matrix. Results Models were trained and evaluated to predict OP using selected features including age, quality of life index, weight, grip strength and average working hours per week. The model achieved 76.8% accuracy, 74.5% precision, 80.5% recall, 77.4% F1 score, and 74.8% ROC AUC. Conclusions A multi-layer perceptron neural network for predicting OP diagnosis using physical characteristics and activity factors in women aged 35 years or older showed relatively good performance. Since the selected variables can be easily measured through surveys, assessment tool, and digital hand dynamometer, this model will be useful for screening elderly women with OP or not in areas with poor medical facilities or difficult access.

The inner surface of a steel pipe could be lined with ceramics by means of a SHS reaction under centrifugal force. Some physical characteristics of the ceramic layer were investigated with the change of filling ratio (thermit mixture, Fe2O3 and Al) and the addition of silica. Two compositions, -Al2O3 and FeAl2O4, were detected in the dispersed phase. The size of alumina grains became larger towards the pipe innermost side at high mixture filling ratios. Additionally, it was found that amorphous silicate materials formed by the addition of silica makes the layer dense significantly. The apparent density and hardness of the ceramic layer were improved from 2.9 g/cm3 and 1,430 Hv to 3.7 g/cm3 and 1,700 Hv with the effect of additive, silica.

Normally, the single wall(SW) corrugated board has more advantages than double wall (DW) corrugated board in terms of the cost of the materials and logistics. For instance, the SW corrugated board has 3 layer papers whereas the DW corrugated board has 5 layer papers. The thickness of the SW is about 5mm, but that of the DW is 8mm. Accordingly, the SW corrugated board is quite more used in the developed countries than the DW corrugated board. But in Korea, the DW corrugated board is quite more used. The reason why more DW corrugated board are used than the SW corrugated in Korea is that in order that the SW corrugated board has the same box compression strength as DW corrugated board, the cost of the SW corrugated board is higher than that of the DW corrugated board because the virgin kraft liners are all imported from overseas. In this study, the physical properties such as flat crush strength and column crush strength of typical SW corrugated board and single wall dual-layer medium corrugated board and their costs were analyzed. The analysis resulted in that single wall dual-layer medium corrugated board has the same thickness as the SW corrugated board but the more flat crush strength and column crush strength and the less cost than the SW corrugated board.

This paper introduces a new paradigm of physical layer security through channel coding for wireless networks. The well known spread spectrum based physical layer security in wireless network is applicable when code division multiple access (CDMA) is used as wireless air link interface. In our proposal, we incorporate the proposed security protocol within channel coding as channel coding is an essential part of all kind of wireless communications. Channel coding has a built-in security in the sense of encoding and decoding algorithm. Decoding of a particular codeword is possible only when the encoding procedure is exactly known. This point is the key of our proposed security protocol. The common parameter that required for both encoder and decoder is generally a generator matrix. We proposed a random selection of generators according to a security key to ensure the secrecy of the networks against unauthorized access. Therefore, the conventional channel coding technique is used as a security controller of the network along with its error correcting purpose.

본 논문은 센서 네트워크에서 데이터의 신뢰도를 높이고, 전력 효율적인 프로토콜을 제안한다. 그러기 위하여 최대비 결합(MRC)과 순환 부호를 적용한 협력통신 프로토콜을 제안한다. 하나의 소스노드와 하나의 중계노드는 각각의 시간 슬롯에 목적지로 동일한 데이터를 전송하고, 목적지 노드는 각각의 신호를 수신함으로써 다이버시티 효과를 획득할 수 있다. 제안한 프로토콜은 순환부호를 사용함으로써 3-비트의 오류정정능력을 가지며, 많이 사용되는 콘볼루션 코드에 비하여 복호 시 낮은 복잡도를 가진다. 본 논문의 모의실험 결과를 통하여 BER이 일 때, 단일 홉 전송의 경우에 비하여 6dB의 전력을 절약 할 수 있다는 것을 증명하였다.

In this paper, our goal is to find a power-effective protocol that improves the accuracy of transmission in sensor networks. Therefore we propose a cooperative communication protocol based on MRC(Maximal Ratio Combining) and cyclic code. In our proposal, one sensor node assists two others to communicate with a clusterhead that can get diversity effect and MRC can improve diversity effect also. The proposed protocol with cyclic code can correct error up to 3-bit and reduce decoding complexity compared with convolutional code. Simulation results reveal proposed protocol can save the network energy up to 6dB over single-hop protocol at BER(Bit Error Rate) of 10-2.

Network security with encryption and decryption technology to complete the application layer, but this technology will bring computing resources and a waste of energy, particularly in these two resources are limited wireless communication system for this problem, we use a large-scale multi-antenna technology, using beamforming algorithm in power and spectrum limited conditions, to maximize the mutual information system security, the simulation results demonstrate the ability to secure transmission algorithms can effectively improve the system.

In this paper, we study physical layer security (PLS) of wireless networks in presence of one eavesdropper. Assume that the channel state information (CSI) of the eavesdropper cannot be obtained at the transmitter, such as CSI can be then estimated through the CSI of a torch node. In addition, a practical issue of wireless nodes, i.e., hardware impairment (HI), is considered at the source node of the network. System performances in terms of secrecy outage probability, probability of non-zero secrecy capacity and ergodic secrecy capacity are then investigated over Rayleigh fading channels. In particular, the closed-form expressions of the secrecy outage probability and probability of non-zero secrecy capacity are provided. Analytical results are then validated by Monte-Carlo simulation. Numerical results reveal the effects of the HI and the advantages of the use of the torch node in PLS of wireless communications.

본 논문에서는 다수의 중계기가 존재하는 복호 후 재전송 기반의 협력 통신 시스템에서 부분적인 중계기 선택 기법 을 사용 했을 때의 보안 불능 확률을 연구한다. 수신 노드와 도청 노드는 각각 송신 노드와 중계 노드 모두에서 신호를 수신 한다고 가정한다. 수신된 두 신호는 MRC 기법을 사용하여 다이버시티 이득을 얻는데 이용된다. 본 논문에서는 다수의 중계 기가 존재하는 시스템의 보안 불능 확률 식을 계산하고, 그 식이 타당한지 증명하기 위해서 이론값과 모의실험 결과값을 비교한다. 중계기의 수에 따라 보안 불능 확률이 어떻게 변하는지를 모의실험 결과를 통해 도출한다.

In this paper, we investigate the secrecy outage probability when using a partial relay selection scheme in cooperative communication systems based on decode-and-forward with multi-relay. It is assumed that both the receiving node and the eavesdropping node receive signals at both the transmitting node and the relaying node. The two received signals are used to obtain the diversity gain using the MRC scheme. In this paper, we compute the theoretical formula of secrecy outage probability and compare the theoretical value with the simulation value to prove that equation is valid. The simulation results show how the secrecy outage probability varies with the number of relays.