Minimum Error Detection Research Articles

Covert throughput maximization for NOMA based visible light covert communication networks

Covert throughput maximization for a non-orthogonal multiple access (NOMA)-based visible light covert communication (VLCC) network is investigated. The network consists of a light emitting diode (LED) transmitter, two NOMA users (one public, one covert), and a monitor tasked with detecting any covert transmissions between the LED and the covert user. The transmitter leverages its interaction with the public user to mask the covert communication with the covert user, adopting a random power transmission scheme. This strategy serves to amplify the monitor’s detection uncertainty and significantly enhance the covertness of the VLCC network. Two VLCC scenarios are covered: For the indoor static VLCC scenario where the LED is fixed, subject to the minimum detection error probability of the monitor (covertness constraint) and the outage probability of NOMA users (reliability constraint), the covert throughput is maximized by optimizing the ratio of the LED’s power allocation factor (PAF). For the mobile VLCC scenario where the LED is mounted on an unmanned aerial vehicle (UAV), subject to the constraints of the covertness, reliability and UAV’s flight region, the optimal LED’s PAF ratio and UAV’s location are jointly obtained via a graphical approach. Finally, simulations are carried out to analyze the influence of VLCC parameters on the maximum covert throughput, and results show that compared with benchmark schemes, the proposed scheme can greatly improve the covert throughput.

Study on covert rate in the D2D networks with multiple non-colluding wardens

This paper investigates the covert communication of cellular link in the device-to-device (D2D)-enabled underlaying cellular network, including a base station, a cellular user, a D2D pair, and multiple non-colluding wardens. To conduct covert communication between the base station and the cellular user without being detected by the wardens, the underlaid D2D pair transmits with a random power to add uncertainty to wardens. We first model the detection of multiple non-colluding wardens, and the average minimum detection error probability of the worst case is derived. To measure the covert performance of the cellular link, the average covert rate of the cellular link and the outage probability of the D2D link are explored. Then, we formulate an optimization problem of maximizing the average covert rate under the constraint of the average minimum detection error probability, and an optimization algorithm is designed to solve the optimization problem to identify the optimal transmit power of the D2D pair. Last, the extensive numerical results are presented to show the impacts of network parameters on the covert performance, which indicates that although D2D communication causes interference to the cellular link, it can also help achieve covert communication by carefully designing its maximum transmit power.

Performance Comparison of Relay-Based Covert Communications: DF, CF and AF.

In this paper, we investigate the performance of covert communications in different types of a relay system: decode-and-forward (DF), compress-and-forward (CF) and amplify-and-forward (AF). We consider a source node that attempts to send both public and covert messages to a destination node through a relay on which a covert message detector is embedded. By taking the minimum detection error probability (DEP) at the relay into account, we optimize the power distribution between the public and covert messages to achieve the maximum covert rate. We further make a delay-aware comparison among DF, CF and AF relay systems with the obtained closed-form covert rates and conduct an extensive examination on the asymptotic behaviors in different limits. Our analyses reveal that CF or AF tend to outperform DF for high source transmit power or low relay transmit power, while various system parameters such as the processing delay, minimum required quality of service for public messages and DEP threshold lead to different performance relationships among DF, CF and AF for high relay transmit power. Numerical results verify our investigation into the performance comparison in various channel models.

On Joint Optimization of Trajectory and Phase Shift for IRS-UAV Assisted Covert Communication Systems

In this paper, we propose an unmanned aerial vehicle carrying intelligent reflecting surface (IRS-UAV) as a relaying node to assist covert communication system (CCS). To ensure the security of the covert messages, we derive the minimum error detection probability for the eavesdropper when the locations of the UAV and BS are known. Under the assumption that the eavesdropper can minimize the detection error probability, we then formulate the maximization of the average rate of the proposed IRS-UAV assisted CCS as an optimization problem with respect to the UAVs trajectory and the IRSs phase shift. Furthermore, we use the Taylor's extension to approximate the optimization problem to be convex, and propose an iterative algorithm to solve the convex problem. Numerical results demonstrate that the developed optimization method significantly improves the data rate for IRS-UAV assisted covert communication in comparison with existing algorithms.

Egzersiz için Hedef İçeriği Anketi’nin Türkçe versiyonunun kültürler arası adaptasyonu, güvenilirliği ve geçerliliği

Aim: The aim of the study was to demonstrate the cross-cultural adaptation, reliability and validity of the Turkish version of the Goal Content for Exercise Questionnaire (GCEQ).
 Materials and Methods: A prospective and cross-sectional study was carried out with 100 healthy young individuals. Participants were assessed with GCEQ. One week later, 39 individuals refilled the GCEQ. Reliability was evaluated with the Intraclass correlation coefficient (ICC) and Cronbach's α coefficient. Construct validity was determined by correlational and explanatory factor analysis. The cut-off value of GCEQ was discriminated with the Receiver Operating Characteristic (ROC) curve. On the other hand, the minimum detectable change (MDC95) and Standard error of measurement (SEM95) values of the GCEQ were calculated.
 Results: A total of 100 individuals (21.1±2.9 years, 72% female) were included in the study. The alpha coefficient was >0.80 for the total and sub scores (except for the image sub score). On the other hand, all scores were scored above 0.80 in ICC analysis. The SEM95 and MDC95 values of the GCEQ were 4.83 and 13.3, respectively. The GCEQ total score had a correlation coefficient of >0.50 with all other sub scores (r=0.55 to 0.80, p

Covert communications in a compress-and-forward relay system

In this paper, we study covert communications strategies in a compress-and-forward (CF) relay system. Along with a public message to a destination node via a CF relay, a source node attempts to transmit a covert message while evading the surveillance of the CF relay. We identify the optimal power distribution between the public and covert messages and the optimal amount of compression that maximize the covert rate subject to the minimum detection error probability requirement. Our provided solutions also reveal that both the power distribution and the achievable covert rate are identical to that of an equivalent amplify-and-forward (AF) relay system if an adequate quantization codebook with the optimal compression is employed. The numerical results verify the effectiveness of the optimal solutions and confirm our analyses.

An Efficient Fault Detection and Exclusion Method for Ephemeris Monitoring

The ephemeris fault needs to be detected and mitigated in the ground-based augmentation system to provide precision approach for the aircraft. In the current fault detection and exclusion (FDE) method, the double-differenced carrier phase (DDCP) observation is used as a test statistic to detect a faulty satellite caused by an ephemeris fault, taking advantage of the residual spatial gradient. However, the current FDE method cannot distinguish whether the fault comes from a reference satellite (RS) or a non-reference satellite (NRS) in DDCP. One way to address this issue is to pre-validate the RS before it can be used to form a DDCP test statistic for detecting ephemeris fault on the NRS. The RS is pre-validated using the previous ephemeris for any newly acquired and re-acquired satellite. This method is developed in detail to present the shortcomings. A more efficient FDE method using multiple hypothesis testing to detect ephemeris fault on both the RS and NRS simultaneously in real time is proposed. Moreover, to facilitate the application in integrity monitoring, the test risks and minimum detectable error are analyzed. The numerical results of the proposed FDE method show an improved performance in detecting ephemeris fault on the RS and a comparable performance on the NRS compared with the current FDE method.

Reliability of the Wii Balance Board for measurement of steady state balance in children aged 6-9 years.

The Wii Balance Board (WBB) can be used for assessment of steady state balance (SSB), but its reliability has not been studied in children aged 6-9 years. This study aimed to determine the test-retest reliability of the WBB for measuring SSB in this population. A secondary aim was to determine the minimum detectable change (MDC) and standard error of measurement (SEM) of the WBB in children aged 6-9 years. 52 children between 6-9 years of age participated. "One leg stand balance" was used to assess center of pressure velocity (COPV) and center of pressure area (COPA) on three occasions by the same tester. Two tests were conducted on the same day (Day 1) and the third test was performed on another day (Day 2), with a period of 5-13 days between the two test days. Intraclass correlation coefficient (ICC 3,1), SEMs, and MDC were calculated. Intra-day test-retest reliability of COPA was found to be good (ICC3,1 =0.86; 95% confidence interval [CI]: 0.75, 0.92) and that of COPV was also found to be good (ICC3,1 =0.87; 95% CI: 0.77, 0.92). Inter-day test-retest reliability was found to be good for COPA (ICC3,1 = 0.87; 95% CI: 0.75, 0.93) and COPV (ICC3,1 = 0.89; 95% CI: 0.81, 0.94). SEM for COPA in intra-day testing was 18.90 mm2 (15.78%), and in inter-day testing it was 16.44 mm2 (13.61%). SEM for COPV in intra-day testing was 1.12 mm/s (7.6%), and in inter-day testing it was 1.01 mm/s (6.9%). MDC for COPA in intra-day testing was 52.41mm2 (42.75%), and in inter-day testing was 45.58 mm2 (35.75%). MDC for COPV in intra-day testing was 3.11 mm/s (21.2%), and in inter-day testing it was 2.80 mm/s (18.9%). The WBB has good test-retest reliability for assessing SSB of children between 6-9 years. COPA measurements appear to be less sensitive to clinical changes in SSB when compared to COPV. Assessment of validity of the WBB in this age group is recommended before it can be considered as a potential balance assessment tool in children.

Multi-antenna Jammer assisted covert communications in data collected IoT with NOMA

In this paper, we investigate covert communications in data collected IoT with NOMA, where the paired sensor nodes S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> and S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> transmit covert messages to a legitimate receiver (Bob) in the presence of a Warden (Willie). To confuse the detection at Willie, an extra multi-antenna friendly jammer (Jammer) has been employed to transmit artificial noise (AN) with random power. Based on the CSI of Willie is available or not at Jammer, three AN transmission schemes, including null-space artificial noise (NAN), transmit antenna selection (TAS), and zero-forcing beamforming (ZFB), are proposed. Furthermore, the closed-form expressions of expected minimum detection error probability (EMDEP) and joint connection outage probability (JCOP) are derived to measure covertness and reliability, respectively. Finally, the maximum effective covert rate (ECR) is obtained with a given covertness constraint. The numerical results show that ZFB scheme has the best maximum ECR in the case of the number of antennas satisfies N > 2, and the same maximum ECR can be achieved in ZFB and NAN schemes with N =3D 2. Moreover, TAS scheme also can improve the maximum ECR compared with the benchmark scheme (i.e., signal-antenna jammer). In addition, a proper NOMA node pairing can further improve the maximum ECR.

Dynamic analysis of muscles and the internal structure of the peripheral nerve as biomarkers of amyotrophic lateral sclerosis: A pilot study with ultrasound imaging

IntroductionThe aim of this study was to determine the behaviour of ultrasound biomarkers of fascicle density and muscle strength in patients with amyotrophic lateral sclerosis (ALS). MethodsWe conducted an observational, cross-sectional pilot study of 14 patients with ALS (28.6% women) and 14 controls. Bilateral cross-sectional ultrasound scans were performed in the abductor pollicis brevis (APB) and tibialis anterior (TA) muscles, with recording of muscle thickness (MT) at rest and in contraction, and the difference in thickness. In the median, sciatic, and common peroneal nerves, we analysed the cross-sectional area (CSA), number of fascicles (NF) and fascicle density (FD). Analyses were nested by laterality. ResultsIntra- and interrater agreement regarding NF was very good, with a minimum detectable error of < 0.7%. In patients with ALS, MT was lower in the APB both at rest (P = .003; g-Hedges = 1.03) and in contraction (P = .017; g-Hedges = 0.78) and in TA at rest (P = .002; g-Hedges = 0.15) and in contraction (P = .001; g-Hedges = 0.46), with lower thickening capacity. In the nerves, patients displayed lower CSA, with lower NF and higher FD. Significant correlations were found between MT of the ABP and Medical Research Council (MRC) scores for muscle strength (r = 0.34; r2 = 12%; P = .011) and with revised ALS Functional Rating Scale scores (r = 0.44; r2 = 19%; P < .001). The difference in TA thickening correlated with MRC scores (r = 0.30; r2 = 15%; P = .003) and with revised ALS Functional Rating Scale scores (r = 0.26; r2 = 7%; P = .049). NF in the sciatic nerve showed a significant correlation with MRC scores (r = 0.35; r2 = 12%; P = .008). ConclusionMT measurements derived from dynamic testing together with NF and FD may be useful biomarkers for monitoring patients with ALS and establishing a prognosis.

Joint Trajectory and Resource Optimization for Covert Communication in UAV-Enabled Relaying Systems

A novel covert communication framework is proposed to enhance the privacy of the unmanned aerial vehicle (UAV)-enabled relaying systems. Specifically, the full-duplex (FD) UAV covertly relays data from each ground sensor to remote base station (BS) against a warden (Willie). Considering a noise uncertainty model, the minimum detection error probability (DEP) of Willie is first derived. Under the constraint of the derived DEP, the minimum average covert transmission rate (ACTR) is then maximized by jointly designing the sensor association, the UAV transmit power, and the UAV trajectory. A low-complexity algorithm based on the penalty successive convex approximation (P-SCA) is further invoked to achieve the locally optimal solution. Finally, numerical results show the effectiveness of the proposed framework and reveal some insights, i.e., increasing uncertainty at Willie can improve the covertness performance.

Optimal Position and Target Rate for Covert Communication in UAV-Assisted Uplink RSMA Systems

With the explosive increase in demand for wireless communication, the issue of wireless communication security has also become a growing concern. In this paper, we investigate a novel covert communication for unmanned aerial vehicle (UAV)-assisted uplink rate-splitting multiple access (RSMA) systems, where a UAV adopts the rate-splitting (RS) strategy to increase the total transmission rate while avoiding deteriorating the covert transmission of a ground user. In the proposed system, a ground user and a UAV adopt the RSMA scheme to simultaneously communicate with a base station surveilled by an evil monitor. The UAV acts as both the transmitter and the friendly jammer to cover the ground user’s transmission with random power. To maximize the expected sum rate (ESR), we first study the RS strategy and obtain the optimal power allocation factor. Then, the closed-form of minimum detection error probability (DEP), ESR, and optimal target rate of the UAV are derived. Constrained by the minimum DEP and expected covert rate (ECR), we maximize the ESR by optimizing the position and target rate of the UAV. Numerical results show that the proposed scheme outperforms the traditional NOMA systems in terms of ESR with the same DEP and ECR.

Multi-feature detection of in-field grain lodging for adaptive low-loss control of combine harvesters

The phenomenon of grain lodging significantly affects the low-loss harvesting performance of automatic drive harvesters, and it has become an objective trend to simultaneously detect multi-feature grain lodging information with machines in the field. In order to solve the problem of high harvest loss in grain lodging areas, we propose a new method for synchronous detection of grain lodging multi-feature information based on 3D point cloud data of a depth camera, in order to realize adaptive regulation of unmanned and low-loss harvesting. The multi-feature information of lodging grain is composed of lodging position, degree and direction, which can provide effective support information for the adaptive regulation of automatic driving harvesters. For the scene of grain harvesting operation with low contrast characteristics, we make full use of the environmental characteristics of the lodging areas that are located in the non-lodged area, and construct a synchronous airborne extraction strategy for grain lodging multi-feature information. The test results show that the maximum detection error of the lodging degree is less than 9.0 cm, and the minimum detection error is better than 1.0 cm; the maximum detection error of the lodging direction is not more than 9.0°, the minimum detection error is less than 1.0°, the maximum harvesting height error is less than 5.0 cm, and the minimum harvesting height error is less than 5.0 cm. Better than 2.0 cm. Our method provides an effective solution for synchronous airborne detection of multi-feature grain lodging information, which can significantly reduce harvest loss in grain lodging areas, and is expected to accelerate the development of truly unmanned harvesting operations.

Mathematical modeling of underwater signal anomaly perception based on multi-sensor data fusion

There is a lot of interference in underwater environment, which can affect underwater signal transmission. For this reason, an abnormal perception model of underwater signals based on multi-sensor data fusion is proposed. The underwater frequency hopping communication method is used to select the channel and construct the mathematical model of underwater communication signal. A signal modulation and recognition system for multi-sensor reception is established, and the multi-sensor data fusion model is obtained by calculating the support margin. The energy spectrum distribution is obtained by decomposition of abnormal features with wavelet detector in time domain. The deep learning algorithm is used to reorganize the signal with the minimum detection error, and the mathematical model of underwater signal anomaly perception is obtained. The experimental results show that the average accuracy of the method for locating abnormal underwater communication signals is 95.5%, the misrecognition rate of abnormal underwater signals is less than 2%, and the time-consuming for sensing abnormal signals of 420 MB underwater communication is less than 3 s.

A comprehensive retrieval method of social media information based on fuzzy mathematics

In order to solve the problems of low retrieval accuracy and long retrieval time of traditional information comprehensive retrieval methods, a social media information comprehensive retrieval method based on fuzzy mathematics is proposed in this paper. Firstly, the social media information data is collected by hash function; Then, the cross filter is used to remove similar social media data. Finally, according to the fuzzy triangle number in the fuzzy mathematics method, the keyword weight in social media information is calculated. The comprehensive retrieval of social media information is completed by determining the attribute of social media information and reducing the word frequency range of social media information. The experimental results show that the minimum detection error of this method is about 0.15%, and the shortest information retrieval time is about 1.0 s. The retrieval effect of the proposed method is good.

Zero-forcing Beamforming for Jamming Aided Covert Communication in MIMO Systems

This paper investigates covert wireless communication in a multi-input multi-output (MIMO) system, where a multi-antenna transmitter transmits covert signal to a multi-antenna receiver with the assistance of a multi-antenna jammer employing zero-forcing (ZF) beamforming to avoid detection by a warden equipped with single antenna. For the given scenario, we first provide theoretical modeling for the minimum detection error probability at warden and covert rate from transmitter to receiver. We then explore the optimal beamformer design of the jammer to maximize the covert rate, subjecting to the constraints of covertness, upper bounds of transmitter and jammer transmit power, and beamformer on jammer. We further devise an iterative algorithm to determine the related optimal precoding matrix for covert rate maximization. Finally, we provide extensive numerical results to illustrate the impact of system parameters on covert performance.

Covertness and Secrecy Study in Untrusted Relay-Assisted D2D Networks

This article investigates the covertness and secrecy of wireless communications in an untrusted relay-assisted device-to-device (D2D) network consisting of a full-duplex base station (BS), a user equipment (UE), and an untrusted relay <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}$ </tex-math></inline-formula> . For the covertness, we attempt to prevent Willie from detecting the very existence of communications via a D2D link from UE to R and cellular link from R to BS, while for the secrecy, we aim to prevent the untrusted relay from eavesdropping the UE message. To explore the fundamental covertness and secrecy in such a network, we first provide theoretical modelings for the average minimum detection error rate of Willie, and the average covert/secrecy rate from UE to BS under the underlay and overlay modes, respectively. Based on these models, th we further explore the optimal power control at UE, R, and BS to achieve the average covert rate maximization (MCR) for UE with the constraints of covertness and security requirements under the underlay mode. We also identify the optimal transmit powers and the optimal spectrum partition factor for MCR under the overlay mode. Finally, the exhaust searching method is adopted to solve the MCR problems, and extensive numerical and simulation results are presented to validate our theoretical analysis and to illustrate the average covert rate and secrecy rate of UE under various scenarios.

Probabilistic Accumulate-Then-Transmit in Wireless-Powered Covert Communications

In this paper, we investigate the optimal design of a wireless-powered covert communication (WP-CC) system, where a full-duplex (FD) receiver transmits artificial noise (AN) to simultaneously charge an energy-constrained transmitter and to confuse a warden’s detection on the transmitter’s communication activity. In order to achieve a higher level of covertness, we propose a probabilistic accumulate-then-transmit (ATT) protocol, where the transmitter is able to adjust the prior probability conditioned on the available energy being sufficient, i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$ </tex-math></inline-formula> , rather than setting <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p=1$ </tex-math></inline-formula> as in the traditional ATT protocol to maximize the system throughput. Then, we derive the warden’s minimum detection error probability and characterize the effective covert rate from the transmitter to the receiver to quantify the communication covertness and quality, respectively. The derived analytical results facilitate the joint optimization of the probability <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$ </tex-math></inline-formula> and the information transmit power to maximize the communication covertness subject to a quality-of-service (QoS) requirement on communication. We further present the optimal design of a cable-powered covert communication (CP-CC) system as a benchmark for comparison. Our simulation shows that the proposed probabilistic ATT protocol (with a varying <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$ </tex-math></inline-formula> ) can achieve the covertness upper bound determined by the CP-CC system, while the traditional ATT protocol (with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p=1$ </tex-math></inline-formula> ) cannot, which confirms the benefits brought by the proposed probabilistic ATT protocol in covert communications.

Covert communication for cooperative NOMA with two phases detection

This paper investigates the covert communication of cooperative non-orthogonal multiple access (NOMA) systems, where the near user serves as a decode-and-forward (DF) relay and the far user receives the covert information from both the source and the near user. To improve the covertness performance, cooperative jamming and power randomness are adopted. Specifically, we derive detection error probability (DEP) of Willie and the minimum detection error probability (MDEP) at the optimal decision threshold for each phase. In addition, the reliability of the proposed system is investigated by deriving closed-form expressions for the outage probability (OP) of the two users. Under the covertness and reliability constraints, an optimization algorithm to maximize the effective covert rate is designed. Simulation results have confirmed the correctness of the theoretical analysis, and the proposed scheme can achieve a better covert communication.

Covert Communication in Downlink NOMA Systems With Channel Uncertainty

With the gradual promotion of the fifth generation (5G) mobile communication and Internet of Things (IoT) applications, wireless communication transmission will be more vulnerable to illegal interceptions and/or attacks. To ensure communication security, we study covert communication of downlink nonorthogonal multiple access (NOMA) systems, where the channel knowledge of users is uncertain. A multiantenna transmitter tries to covertly transmit information to a covert user (strong user) through the shield of a public communication link (weak user), while the warden tries to detect the communication behavior between the transmitter and the covert user. To improve security and energy efficiency, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> th best antenna of the transmitter is selected, since the optimal antenna may be not available due to some schedule and/or other reasons. Aiming to evaluate the proposed framework performance, we start by deriving exact expressions for the minimum detection error probability and the optimal detection threshold of the warden, followed by a calculation analysis of the expected minimum detection error probability (EMDEP) and the outage probability of NOMA users. The asymptotic behavior for the outage probability is investigated at high signal-to-noise ratio (SNR) to acquire greater useful insights. With the goal of improving the system covertness performance, we propose that a scheme is optimized to enhance the covert throughput of the system to the maximum. Simulation results show that the following hold: 1) channel estimation errors have a significant effect on system performance; 2) reliability performance tends to build up, as the total number of antennas grows large; and 3) as the transmitting power and number of antennas increases, there is an upper bound for maximizing the covert throughput.