Mobile Receiver Research Articles

Secure Efficiency Map-Enabled UAV Trajectory Planning

This letter investigates the dynamic changes of security and efficiency in an unmanned aerial vehicle (UAV)-to-ground network with a mobile UAV transmitter, a mobile ground receiver, and a fixed eavesdropper, respectively. To provide communication services with high security, spectrum efficiency, and energy efficiency, a concept of secure efficiency map (SEM) is devised and proposed to plan the UAV trajectory. Specifically, the security-efficiency index of each subarea in a certain area for a certain time slot is firstly calculated. Then, given that the security-efficiency index is time-varying, and CNN-LSTM network can effectively extract data features and accurately reflect time correlation, we take multiple SEMs drawn from the observed security-efficiency indices as the input of the CNN-LSTM network, and output future SEMs. Thirdly, based on predicted future SEMs, an SEM-enabled UAV trajectory planning scheme is further presented to jointly improve security and efficiency of the considered communication network. Finally, simulation results confirm the proposed SEM-enabled UAV trajectory planning scheme achieves a superior joint optimization of security, spectrum efficiency, and energy efficiency to other UAV trajectory planning schemes.

Cooperative jamming aided securing wireless communications without CSI of eavesdroppers

Physical layer security was designed as an effective solution to provide the security and confidentiality of information transmission in wireless networks, and secrecy transmission capacity (STC) played a key role in analyzing the impact of system parameters on physical layer security. Different from the previous works, which exploited cooperative jamming to improve the security with the assumption of perfect channel state information (CSI) of eavesdroppers (Eves), in this paper, without considering Eves’ CSI, we designed two secrecy improvement strategies aided by cooperative jamming with transmit power allocation scheme, i.e., connection guard zone (CGZ) and improved interferer protected zone (IIPZ). Specifically, we established an analytical framework of the STC by applying the tools of stochastic geometry and derived conditions that achieved a positive STC. In addition, we consider the impact of Random WayPoint (RWP) mobile receiver and active eavesdroppers on physical layer security. Simulations showed that IIPZ achieves the best reliability performance and CGZ makes the best secrecy performance than existing popular protections, and RWP mobile destination can achieve a higher level of reliability and STC than these achievable in static scenarios.

Contextual factors affecting the implementation of an anemia focused virtual counseling intervention for pregnant women in plains Nepal: a mixed methods process evaluation

BackgroundAnemia is estimated to cause 115,000 maternal deaths each year. In Nepal, 46% of pregnant women have anemia. As part of an integrated anemia-prevention strategy, family engagement and counseling of pregnant women can increase compliance to iron folic acid tablets, but marginalized women often have lower access to these interventions. We implemented the VALID (Virtual antenatal intervention for improved diet and iron intake) randomized controlled trial to test a family-focused virtual counseling mHealth intervention designed to inclusively increase iron folic acid compliance in rural Nepal; here we report findings from our process evaluation research.MethodsWe conducted semi structured interviews with 20 pregnant women who had received the intervention, eight husbands, seven mothers-in-laws and four health workers. We did four focus groups discussions with intervention implementers, 39 observations of counseling, and used routine monitoring data in our evaluation. We used inductive and deductive analysis of qualitative data, and descriptive statistics of monitoring data.ResultsWe were able to implement the intervention largely as planned and all participants liked the dialogical counseling approach and use of story-telling to trigger conversation. However, an unreliable and inaccessible mobile network impeded training families about how to use the mobile device, arrange the counseling time, and conduct the counseling. Women were not equally confident using mobile devices, and the need to frequently visit households to troubleshoot negated the virtual nature of the intervention for some. Women’s lack of agency restricted both their ability to speak freely and their mobility, which meant that some women were unable to move to areas with better mobile reception. It was difficult for some women to schedule the counseling, as there were competing demands on their time. Family members were difficult to engage because they were often working outside the home; the small screen made it difficult to interact, and some women were uncomfortable speaking in front of family members.ConclusionsIt is important to understand gender norms, mobile access, and mobile literacy before implementing an mHealth intervention. The contextual barriers to implementation meant that we were not able to engage family members as much as we had hoped, and we were not able to minimize in-person contact with families. We recommend a flexible approach to mHealth interventions which can be responsive to local context and the situation of participants. Home visits may be more effective for those women who are most marginalized, lack confidence in using a mobile device, and where internet access is poor.

Performance Analysis of Slow Fluid Antenna Multiple Access in Noisy Channels Using Gauss-Laguerre and Gauss-Hermite Quadratures

Fluid antenna system (FAS) facilitating a position-switchable antenna, enables a mobile receiver to exploit the deep fade opportunity of its interference for multiple access. Slow fluid antenna multiple access ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> -FAMA) is such an emerging proposal that lets multiple users share the same time-frequency channel while each user adopts a fluid antenna to resolve the interference. Previous performance analysis is limited to the case when noise is neglected. In this letter, we remove this limitation and derive new closed-form expressions for the outage probability of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> -FAMA by using Gauss-Laguerre and Gauss-Hermite Quadratures. The analysis reveals the impact of noise on the outage probability for different numbers of users and ports in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> -FAMA networks.

Towards a Dynamic Fresnel Zone Model to WiFi-based Human Activity Recognition

The passive WiFi sensing research has largely centered on activity sensing using fixed-location WiFi transceivers, leading to the development of several theoretical models that aim to map received WiFi signals to human activity. Of these models, the Fresnel zone model has shown to be particularly noteworthy. However, the growing popularity of mobile WiFi receivers has not been matched by corresponding research on mobile receiver-based theoretical models. This paper fills this gap by presenting the first theoretical model to quantify the impact of moving a moving receiver for WiFi sensing. We propose a novel dynamic Fresnel zone model in the free space of an indoor environment, which takes the form of a cluster of concentric hyperbolas centered on the transmitter and reflection subject. We examine three properties of this model, i.e., relating the variation in RF signals received by the receiver to the position and orientation of the human, the movement of the receiver, and the presence of other objects in the environment. To validate this model, we develop a prototype system and conduct extensive experiments. The results are consistent with our theoretical analysis, and the system is able to detect the direction of the transmitter with an accuracy of 10° or better, measure the receiver's relative motion displacement within 1 cm a millimeter-level accuracy, and classify five receiver-side activities with an accuracy of 98%. Our work moves a significant step forward in WiFi sensing and may potentially open up new avenues for future research.

Design and performance analysis of a rectenna system for charging a mobile phone from ambient EM waves

Advances in information technology have dramatically enhanced mobile phones. Power capacity is one of the most significant limitations of a mobile phone. As a result, efficient energy management in such devices is critical everywhere. The goal of this research is to find a way to charge electronic devices wirelessly using radio frequency (RF) electromagnetic (EM) waves (Rectenna using energy detection-based spectrum sensing). Mechanical deformations cause frequency detuning, which lowers the effectiveness of antennas and rectennas that would otherwise allow wireless communication and RF energy harvesting in the far field. A rectenna based on a stretchable multiband antenna is designed as a self-powered system to perform reliably and integrate RF power received across its multiband despite mechanical deformations. Depending on what the battery needs, the proposed multiband antenna will work at 900 MHz, 1800 MHz, 2100 MHz, and 2.45 GHz as both an RF transducer and an RF energy harvester. Depending on the received RF power density (high), the receiving RF wave will be utilized for both communication and RF energy harvesting (RF-EH) when the battery's current voltage is less than 20% (referred to as “low voltage”). Otherwise, the received RF wave will be used only for RF-EH. The installed multiband rectifiers function perfectly in terms of efficiency and bandwidth. This proposed technique would reduce the charging crisis by 60–90% depending on the location of the mobile phone or receiver of ambient EM signals. This paper could help researchers in the field of RF energy-based wireless charging systems.

Антенная система для FM радиовещания с круговой поляризацией и возможностью одновременной работы двумя группами передатчиков

In large radio centers with a large number of broadcasting transmitters of the VHF band operating in the range of 87.5-108 MHz the most common type of antennas are panel antennas. The advantage of these antennas is a large capacity – up to hundreds of kilowatts, the ability to form radiation patterns of various shapes based on the characteristics of the service area, the distribution of population density in this zone and sanitary requirements for residential areas. To meet these requirements, in some cases, the use of antennas that occupy a significant place on masts is required. The implementation of these requirements often interferes with the absence of sufficient free space on masts. In addition, at large radio centers there is a serious problem of placing a large number of powerful FM broadcasting transmitters on one antenna. One of the reasons for the limitation of the number of transmitters is large losses in inseries included combiners. One of the ways to increase the number of transmitters working on one antenna is the use of panel antennas with a doubled number of dipole in each panel having different polarization – vertical and horizontal. Such antennas allow you to work simultaneously with two groups of transmitters with different polarizations on two feeders. The disadvantage of such a solution is that different radio stations operating on the same antenna with different linear polarizations in different conditions of propagation of radio waves at the same power can create different field levels at reception points, which puts them in unequal conditions. Such an antenna can also work with circular polarization but has the only input for only one group of transmitters. An antenna supply scheme is proposed which allows two independent groups of transmitters to work simultaneously on one antenna with circular polarization and use all the advantages of the propagation of circular polarization radio waves in urban conditions and with mobile reception.

Usability and Teachability of Continuous Glucose Monitoring Devices in Older Adults and Diabetes Educators: Task Analysis and Ease-of-Use Survey.

Continuous glucose monitoring (CGM) devices continuously sense and relay glucose concentration data from the interstitial fluid to a mobile phone or receiver. Older adults benefit from this continuous monitoring of glucose levels. Proper deployment of the sensing wire is facilitated by a specialized applicator. Our aim was to assess a new seventh-generation (G7) CGM device (Dexcom, Inc) for use by adults 65 years of age or older and certified diabetes care and education specialists (CDCESs). Ease of use related to intradermal insertion and mobile app setup will be assessed and compared to the fifth- and sixth-generation systems. Formal task analysis was conducted to enumerate the number and complexity of tasks associated with CGM deployment. We recruited 10 older adults with no prior CGM experience and 10 CDCESs to assess ease of use through hands-on insertion and initiation of a G7 system followed by a survey and, for older adults, a system usability scale survey. About half as many tasks are needed to deploy G7 compared to G6. Older adults and CDCESs reported overall high usability of the G7 CGM device. CDCESs noted G7's easier setup compared to previous generations. The system usability scale score for the CGM system was 92.8, which reflects excellent usability. For CDCESs and for older adults using the G7 CGM system, cognitive burden is relatively low and reduced compared to previous CGM systems. Easing of this burden and simplification of the glucose monitoring aspect of proper diabetes management will likely contribute to improved outcomes in this population.

On Zone-Differentiated Time-Constrained Flow Capacity Intelligent Monitoring for Large-Scale Urban Pipeline Systems by Mobile Sensors

Large-scale urban pipeline systems (LSUPSs) are complex pipeline networks of flows (e.g., water, oil, or gas). Flow capacity intelligent monitoring, e.g., automatically monitor the sum of flows in an LSUPS, is an important task in smart cities. Recently, mobile sensors and static receiver nodes are used to perform the task. Mobile sensors are released into the network at selected entrances to collect data, and upload the data to receiver nodes deployed at selected locations of the network for further analysis. Due to cost constraints, the numbers of mobile sensors and receiver nodes are limited, which cause the problem that some pipelines may not be monitored. However, applications normally require that some Zones of Interest (ZoIs) in the network have to be monitored. Therefore, how to select optimal entrances and locations for given numbers of mobile sensors and receiver nodes, so that the capacity of monitored flow is maximized within a given time under the constraint that all ZoIs are also monitored with expected probabilities, is a challenging problem. First, we prove the problem is NP-complete. Then, we design two algorithms based on submodular set function optimization to solve it. The first algorithm can obtain an approximate optimal solution with high time complexity, while the second algorithm can obtain a suboptimal solution with much lower time complexity. Finally, we analyze time complexity and approximate ratio of the two algorithms. Theoretical analyses and simulation results show that the proposed algorithms outperform the state-of-the-art algorithms.

An Indoor Environment Sensing and Localization System via mmWave Phased Array

In this paper, an indoor layout sensing and localization system with testbed in the 60-GHz millimeter wave (mmWave) band, named mmReality, is elaborated. The mmReality system consists of one transmitter and one mobile receiver, both with a phased array and a single radio frequency (RF) chain. To reconstruct the room layout, the pilot signal is delivered from the transmitter to the receiver via different pairs of transmission and receiving beams, so that multipath signals in all directions can be captured. Then spatial smoothing and the two-dimensional multiple signal classification (MUSIC) algorithm are applied to detect the angle-of-departures (AoDs) and angle-of-arrivals (AoAs) of propagation paths. Moreover, the technique of multi-carrier ranging is adopted to measure the path lengths. Therefore, with the measurements of the receiver in different locations of the room, the receiver and virtual transmitters can be pinpointed to reconstruct the room layout. Experiments show that the reconstructed room layout can be utilized to localize a mobile device via the AoA spectrum.

GNSS RTK/UWB/DBA Fusion Positioning Method and Its Performance Evaluation

As a significant space–time infrastructure, the Global Navigation Satellite System (GNSS) provides high-precision positioning, navigation, and timing (PNT) information to users all over the world. However, GNSS real-time kinematic (RTK) mobile receiver signal attenuation is obvious in complex environments such as under trees, urban canyons, and indoors, among others, and it is incapable of meeting the demand of multi-level mass users for indoor and outdoor seamless positioning applications. The goal of this study was to address the limitations and vulnerabilities of the GNSS RTK positioning above-mentioned. First, we propose a GNSS RTK/UWB/DBA fusion positioning model and provide detailed algorithm steps for various types of observations. The performance of the GNSS RTK/UWB/DBA fusion positioning under various occlusion environments is then thoroughly evaluated using static and dynamic cart experiments. The experiment results show that as the elevation mask angle increases, the number of available GNSS satellites decreases and the ambiguity resolution success rate decreases; in comparison to GNSS RTK, the proposed GNSS RTK/UWB/DBA fusion positioning model can significantly improve the spatial geometry distribution of observations, reduce the position dilution of precision (PDOP) value, and improve the ambiguity resolution success rate. At an elevation mask angle of 50 degrees, GNSS RTK/UWB/DBA combination positioning can improve the ambiguity resolution success rate by 20% to 60%, and a positioning error less than 5 cm by 20% to 50%. It also indicates that the GNSS RTK/UWB/DBA fusion positioning model has higher positioning accuracy and can effectively improve the availability and reliability of GNSS RTK in a local harsh environment.

Low-Complexity Visible Light Positioning and Rotation Estimation Based on Eigenvalue Decomposition

Most existing visible light positioning (VLP) systems assume vertically placed receivers, or estimate the receiver rotations through gyroscopes. Although several recent VLP systems can deal with the arbitrary tilting of the receiver without the additional sensors, the positioning frequency, algorithm efficiency and stability are still to be improved. In this work, we propose a novel positioning and rotation estimation algorithm based on the eigenvalue decomposition of the covariance matrix of light direction vectors. Four or more light-emitting diodes (LEDs) serve as the anchors and three or more tilted photodiodes are equipped on the mobile receiver. The new algorithm's computational complexity only grows linearly with the number of LEDs, and it can distinguish and bypass the local optima by verifying if the objective function reaches its theoretical maximum. We use simulations to reveal the error patterns of the algorithm and build a low-cost prototype to verify its real performance. The measured average positioning error is 1.83 cm and the orientation estimation error is 0.04 rad. The proposed scheme can be used for positioning and navigation that require fast response, low power consumption, low cost, high accuracy and small device size.

A geometry-based stochastic scattering channel model for V2V communications in dense urban street environments

In this paper, we propose a stochastic channel model in three-dimensional (3D) space for multiple input multiple output (MIMO) vehicle-to-vehicle (V2V) communications in dense urban environments. The movement of the mobile transmitter and mobile receiver results in the V2V channel model behave temporal non-stationarity. Therefore, the time-varying parameters of the propagation paths and angles are derived to characterize such property. Using this channel model, we investigate the propagation characteristics of V2V channels in terms of the road section and moving time/directions/speeds of the transmitter and receiver. Numerical results show that the theoretical results of the propagation characteristics of the V2V channel model are very close to those of the simulation ones, which show that the proposed channel model is suitable for depicting the V2V communications in dense urban scenarios.

Automatic Gbps Receiver for Mobile Device in Beam-Steered Infrared Light Communication System

This work presents a beam-steered infrared light communication (BS-ILC) system that enables high data rate wireless optical transmission to individual mobile users. The BS-ILC system comprises arrayed waveguide grating router-based optical antennas, camera-based user localization, and optical receivers (each integrated with an infrared tag). A high-speed photodetector has typically a small active area to minimize its junction capacitance, but this small size will result in a very limited field of view (FoV), which is detrimental to an optical wireless system aimed to provide some degree of mobility to users. Thus, the desired BS-ILC system requires precise and automatic alignment to establish a high-performance optical link between users and optical antennas. In this work, we propose an optical wireless receiver that can automatically align its orientation with respect to the optical antenna to ensure the light angle of incidence within the receiver’s FoV. The automatic receiver consists of a motorized actuator and an optimization control algorithm. The actuator controls the orientation of the receiver, and the optimization algorithm is developed to accelerate the searching process of the actuator. In an indoor laboratory system setup, the amount of less than 200 ms has been demonstrated to establish gigabit-per-second optical link, and seamless transmission has also been realized for the mobile receiver while on the move with the FoV of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm 0.6^{\circ }$</tex-math></inline-formula> .

A Visibility Matching Technique for Efficient Millimeter-Wave Vehicular Channel Modeling

Site-specific propagation models for highly dynamic vehicle-to-vehicle (V2V) scenarios become time consuming as the identification of visible surfaces must be performed independently for each transmitter location. Moreover, the validation of higher order of ray interactions presents a significant computational overhead. This communication presents an efficient ray-tracing algorithm for V2V propagation prediction. The model presented in this communication extends a previous model that uses a precomputed database of intra-visibility of walls and edges in the environment. The model computes the list of faces and edges that are directly visible to the mobile receiver. This visibility information is then used to reduce the image-tree thereby accelerating the ray validation. The communication also presents an efficient technique to compute diffuse scattered rays in a timely manner. The validation results show considerable time saving over previous models.

A novel method for identifying coded tags recorded on aquatic acoustic monitoring systems

Aquatic biotelemetry increasingly relies on using acoustic transmitters (‘tags’) that enable passive detection of tagged animals using fixed or mobile receivers. Both tracking methods are resource-limited, restricting the spatial area in which movements of highly mobile animals can be measured using proprietary detection systems. Transmissions from tags are recorded by underwater noise monitoring systems designed for other purposes, such as cetacean monitoring devices, which have been widely deployed in the marine environment; however, no tools currently exist to decode these detections, and thus valuable additional information on animal movements may be missed. Here, we describe simple hybrid methods, with potentially wide application, for obtaining information from otherwise unused data sources. The methods were developed using data from moored, acoustic cetacean detectors (C-PODs) and towed passive receiver arrays, often deployed to monitor the vocalisations of cetaceans, but any similarly formatted data source could be used. The method was applied to decode tag detections that were found to have come from two highly mobile fish species, bass (Dicentrarchus labrax) and Twaite shad (Alosa fallax), that had been tagged in other studies. Decoding results were validated using test tags; range testing data were used to demonstrate the relative efficiency of these receiver methods in detecting tags. This approach broadens the range of equipment from which acoustic tag detections can be decoded. Novel detections derived from the method could add significant value to past and present tracking studies at little additional cost, by providing new insights into the movement of mobile animals at sea.

UTC and GNSS system time access using PPP with broadcast ephemerides

The application of precise point positioning with broadcast ephemerides (PPP-BCE) is discussed as an alternative to the established all-in-view technique for multi-GNSS time transfer. It combines the use of broadcast ephemerides with low-noise carrier-phase observations for accessing GNSS system time scales and Coordinated Universal Time (UTC) with improved precision, and can be employed on stationary as well as mobile receivers in offline or real-time analyses. Using calibrated timing receivers, the method is shown to provide estimates of the GNSS-to-GNSS time offsets (XYTOs) with an accuracy at the 2 ns level. In the absence of prior calibrations, 0.5 ns consistency across different stations is achieved for GPS, Galileo, and BeiDou-3 after adjustment of systematic biases in comparison with calibrated reference stations or broadcast XYTO values. Furthermore, access to GNSS-specific UTC realizations can be obtained through predictions of the UTC offset from GNSS system time as provided in the broadcast ephemerides of individual constellations. The overall quality of the PPP-BCE-derived receiver clock offsets from UTC is assessed using calibrated receivers at various timing laboratories along with BIPM-provided UTC-UTC(k) measurements. Over the 1.5 years covered in the study, an accuracy of 1.8 ns for GPS and 2.5 ns for Galileo is demonstrated. For BeiDou, a slightly worse accuracy of 3 ns is obtained for a single timing laboratory over 9 months.

In-Vehicle Visible Light Communications Data Transmission System Using Optical Fiber Distributed Light: Implementation and Experimental Evaluation.

Visible light communications emerges as a promising wireless communication technology that has been found suitable for numerous indoor and outdoor applications. In this article, a new in-vehicle VLC system is designed, implemented, and experimentally evaluated. The purpose of this new system is to provide car passengers with optical wireless communications. The proposed system consists of a VLC emitter integrated into the vehicle’s ambient lighting system and a mobile VLC receiver. Unlike any previous works, this article proposes a VLC emitter in which the light from a 3 W LED is distributed on a 2 square meter surface using 500 optical fibers whose main purpose is a decorative one. The proposed prototype has been implemented on a car and evaluated in relevant working conditions. The experimental evaluation of the proposed system has demonstrated the viability of the proposed concept and showed a data rate of 250 kb/s while providing a BER lower than 10−7. As far as we know, the proposed concept is totally new in the VLC literature, opening a new area of utilization for VLC technology: using VLC with optical fiber distributed light.

An Experimental Implementation of China Digital Radio (CDR) Broadcasting in Hubei

This paper presents the research and implementation of a China Digital Radio (CDR) experimental network in Hubei, China with two FM-CDR transmitting stations and four FM-band channels. To study the coverage discontinuity problem in a large service area, the experimental network employs an intelligent networking solution that incorporates multiple service channels carrying Broadcast and Data Services (BADS) and a Common-Regional-Information Channel (CRIC) carrying both service data and system information. The electronic service guide (ESG) carried by CRIC can inform the receivers about the available contents from current and adjacent stations, which can significantly improve the service quality in the overlapping areas, especially under mobile reception environment. Two RF tuners are used in the receiving terminals to access the CRIC, and the BADS channel, respectively. This paper first presents the frequency analysis and coverage tests of the experimental network, and then summarizes the coverage performances with different transmission parameter combinations. The goal is to gain experience in frequency planning, coverage prediction, as well as supportable services of CDR digital audio broadcasting.

Novel AoD Estimation Algorithms for WSSUS and Non-WSSUS V2V Channel Modeling

In this paper, we propose efficient computational solutions for estimating the statistical properties of wide-sense stationary un-correlative scattering (WSSUS) and non-WSSUS multiple-input multiple-output (MIMO) vehicle-to-vehicle (V2V) channel models. Specifically, in the WSSUS channel models, we first estimate the angle of departure (AoD) for the non-line of sight (NLoS) propagation components. In this manner, the complex channel impulse response (CIR), which are widely used in the existing literature to characterize the wireless channel physical properties, can be estimated on the basis of the estimated AoD and defined model parameters. Conversely, in the non-WSSUS channel models, by estimating the AoD in the initial stage, the real-time complex CIR of the V2V channel model can be estimated on the basis of the estimated AoD and the moving time/velocities/directions of the mobile transmitter (MT) and mobile receiver (MR). In the estimation process of the aforementioned cases, we introduce different solutions to convert the CIRs from the complex domain to the real-value domain, thereby optimizing the computational efficiency for investigating channel characteristics as compared to existing methods. Numerical results of the WSSUS and non-WSSUS MIMO V2V channel characteristics, such as the spatial-temporal (ST) cross-correlation functions (CCFs) and auto-correlation functions (ACFs), are estimated on the basis of the estimated complex CIRs. These results are in agreements with theoretical ones, indicating that the proposed algorithms are practical for estimating the WSSUS and non-WSSUS MIMO V2V channel characteristics.