Mobile Access Points Research Articles

Reconfigurable Liquid Metal-Based SIW Phase Shifter

This article presents the first substrate integrated waveguide (SIW) phase shifter that can be reconfigured using liquid metal (LM). This digital phase shifter exhibits low insertion loss and is reciprocal and bidirectional. It incorporates a series of holes which can be filled or emptied of liquid metal, enabling us to add or remove via connections dynamically, on-the-fly. Using a collection of such holes, it is possible to create a wall along the E-plane or H-plane of the waveguide. When the wall is in place, it blocks the passage of energy. When the wall is absent, energy is able to flow. In this way, it is possible to guide the electromagnetic (EM) waves through one of three paths, having different electrical lengths. The result is a digital switched-line phase shifter that achieves coarse steps of phase change, from 0° up to 180°, in steps of 60°. By filling or emptying individual holes, it is possible to introduce reactive loading into each path. In this way, it is possible to achieve fine phase control in steps of 10°. Using both forms of reconfiguration in unison, the proposed phase shifter is able to deliver a phase shift of up to 180°, in steps of 10°. The proposed phase shifter operates at 10 GHz and exhibits an insertion loss of less than 2.3 dB over its entire operating band. Furthermore, the underlying concept of the proposed phase shifter can be readily scaled for operation in the millimeter-wave (mm-wave) band. The existing phase shifters operating in that band exhibit significant insertion losses. MM-wave phase shifters are expected to find application in 5G mobile access points.

Algorithms for addressing line-of-sight issues in mmWave WiFi networks using access point mobility

Line-of-sight (LOS) is a critical requirement for mmWave wireless communications. In this work, we explore the use of access point (AP) infrastructure mobility to optimize indoor mmWave WiFi network performance based on the discovery of LOS connectivity to stations (STAs). We consider a ceiling-mounted mobile (CMM) AP as the infrastructure mobility framework. Within this framework, we propose two heuristic algorithms (basic and weighted) derived from Hamming distance computation and a machine learning (ML) solution fully exploiting available network state information to address the LOS discovery problem. Based on the ML solution, we then propose a systematic solution WiMove, which can decide if and where the AP should move to for optimizing network performance. Using both ns-3 based simulation and experimental prototype implementation, we show that the throughput and fairness performance of WiMove is up to 119% and 15% better compared with single static AP and brute force search.

The library QR-projects in digital space

Abstract: The technological solutions in culture and arts increase accessibility of cultural goods and intensity of cultural environment. QR-technologies designed by Denso Wave Incorporated have become digitalization component increasingly popular in library and information services. The mobile access points call for new ways of library and information services. The concept, characteristics and advantages of QR technology are examined; options for QR code application in libraries are suggested. As the majority of library users owns mobile phones, QR technologies provide unique opportunities. MTS (Mobile Telecommunications System) was the first company to initiate the project of using mobile phones to expand library information space: QR-code linking to books were placed in the city public places. Library applications for QR-codes are outlined, e. g. library information advertisement, user services, social events to promote reading, monitoring in the pandemic situation, etc. The opportunities and prospects for this resource are investigated by the examples of RNPLS&T, Belgorod State Universal Scientific Library, V. G. Korolenko Public Scientific Library (Glazov, Udmurt Republic), Centralized Library System (Georgievsk, Stavropol Territory). The author also suggests that QR codes may solve the problem of access to full and reliable information.

Direct position determination with phase error compensation for multiple targets using spatial sparsity

Measuring the positions of multiple targets is key in many positioning applications. Utilizing compressed sensing theory, measurements using the sparse direct position determination (DPD) methods are more accurate than the two-step methods and the traditional DPD methods. Position measurement with mobile access points (APs) expands the network coverage, increases information throughput and reduces implementation costs, which motivates us to extend sparse DPD (SDPD) to the mobility-assisted positioning system. However, one of the most critical problems in mobility-assisted positioning is the model errors coming from the AP position and velocity uncertainty. The paper proposes a phase error compensation algorithm for the SDPD algorithm based on mobile APs. The algorithm makes two key technical contributions. First, a double iteration for -norm optimization is designed to compensate phase errors and recover target distribution maps simultaneously. Second, when the data collection is incomplete or irregular, the algorithm jointly integrates the global information of target distribution maps at different APs to improve the measurement accuracy. Experimental results indicate the effectiveness of the algorithm.

On how to model and investigate the interaction of mobile network nodes with a limited number of mobile access points

This paper investigates a new way to position unmanned aerial vehicles, that act as routers, to allow subscribers to access a communication network. In my model, the subscribers move along known trajectories in sparsely populated areas. To solve this problem, I developed a software to simulate how the subscribers move. I also developed an optimization algorithm that maximizes my custom objective function, where the function sums the probabilities for the subscribers to access the network.

LEDGE: Leveraging Edge Computing for Resilient Access Management of Mobile IoT

Due to the blooming of Internet of Things (IoT), heterogeneous IoT mobile devices emerge to connect the network infrastructure. Traditional mobile access system faces several challenges arising from these IoT devices: 1) centralized controllers are distant from the end devices, 2) inefficient access control of heterogeneous IoT devices, and 3) insufficient authentication and monitoring for IoT devices. In order to tackle the challenges from IoT devices on mobile access control and scalable access monitoring, we present LEDGE, an agile and secured software-defined edge computing system for resilient access management of mobile IoT. In a nutshell, our LEDGE is a synergy of an efficient location authentication method to secure communication between each IoT mobile device and access point (AP) pair, an optimal AP assignment scheme to satisfy IoT flow requests, a Personal AP protocol for scalable access, and a deep learning model for anomaly detection. We prototype our system, and realistic testbed experiments demonstrate that LEDGE could achieve promising results in mobile IoT.

Throughput Maximization of Wireless-Powered Communication Networks: An Energy Threshold Approach

In this paper, we consider a wireless-powered communication network (WPCN) where one mobile hybrid access point (HAP) coordinates the wireless energy transfer to sensor nodes and receives data from sensor nodes, which are powered exclusively by the harvested wireless energy. As the harvest-then-transmit protocol is employed by sensor nodes, a major challenge lies on the tradeoff between achievable throughput and energy harvesting opportunity of sensor nodes. Confronting this challenge, we develop an energy threshold approach by jointly considering geographic locations and energy states of sensor nodes, where wireless energy transfer occurs when none of the sensor nodes in the range of data transmission has more energy than the threshold, otherwise data transmission from one randomly chosen qualified sensor node to the HAP occurs. By comparing the range of energy harvesting and that of data transmission, we divide the network topology into two cases for throughput analysis, and formulate the energy states of sensor nodes as Markov chain processes with different energy state spaces in the two cases. Through monotonicity analysis of achievable throughput and probability distribution of energy states, we prove the existence of the optimal energy threshold that maximizes the achievable throughput, and find that the achievable throughput under infinite battery size could be viewed as the upper bound of that under the limited battery size. Finally, simulation results validate theoretical results of the optimal energy threshold, and show the impacts of system parameters on the achievable throughput.

Defeating Jamming Using Outage Performance Aware Joint Power Allocation and Access Point Placement in Uplink Pairwise NOMA

In this paper, an uplink pairwise Non-Orthogonal Multiple Access (NOMA) scenario using a mobile access point (AP) or an unmanned aerial vehicle in the presence of a jamming attack is considered. To mitigate the influence of the jamming attack, a joint power allocation and AP placement design is proposed. Accordingly, closed-form expressions of the overall outage probability (OOP) and the individual outage probability (IOP) considering imperfect channel state information for each of the source nodes the AP serves, are derived over Nakagami- $m$ fading channels using dynamic decoding order and fixed pairwise power allocation. We conduct an investigation of the effect of different parameters such as power allocation, source node placements, AP placement, target rates, and jammer location on the OOP and the IOP performance. By adapting the power allocation and the AP placement to the jamming attack, the communication reliability can be increased significantly compared to neglecting the presence of the jammer or treating the jammer as noise. Since the malicious jammer and the AP have conflicting interests in terms of communication reliability, we formulate a non-cooperative game for the two players considering their positions and the power allocation of the NOMA nodes as their strategies and the OOP as utility function. We propose using hybrid simulated annealing - greedy algorithms to address the joint power allocation and AP placement problem for the cases of both a fixed and a mobile jammer. Finally, the Nash equilibrium points are obtained and then the UAV goes directly to this position and keeps staying there to save power consumption.

Deployment of Clustered‐Based Small Cells in Interference‐Limited Dense Scenarios: Analysis, Design, and Trade‐Offs

Network densification is one of the most promising solutions to address the high data rate demands in 5G and beyond (B5G) wireless networks while ensuring an overall adequate quality of service. In this scenario, most users experience significant interference levels from neighbouring mobile stations (MSs) and access points (APs) making the use of advanced interference management techniques mandatory. Clustered interference alignment (IA) has been widely proposed to manage the interference in densely deployed scenarios with a large number of users. Nonetheless, the setups considered in previous works are still far from the densification levels envisaged for 5G/B5G networks that are considered in this paper. Moreover, prior designs of clustered‐IA systems relied on oversimplified channel models and/or enforced single‐stream transmission. In this paper, we explore an ultradense deployment of small cells (SCs) to provide coverage in 5G/B5G wireless networks. A novel cluster design based on a size‐restricted k‐means algorithm to divide the SCs into different clusters is proposed taking into account path loss and shadowing effects, thus providing a more realistic solution than those available in the current literature. Unlike previous works, this clustering method can also cater for spatial multiplexing scenarios. Also, several design parameters such as the number of transmit antennas, multiplexed data streams, and deployed APs are analyzed in order to identify trade‐offs between performance and complexity. The relationship between density of network elements per area unit and performance is investigated, thus allowing to illustrate that there is an optimal coverage area value over which the network resources should be distributed. Moreover, it is shown that the spectral‐efficiency degradation due to the intercluster interference in ultradense networks (UDNs) points to the need of designing an interference management algorithm that accounts for both intracluster and intercluster interferences. Simulation results provide key insights for the deployment of small cells in interference‐limited dense scenarios.

A patient's temperature remote control system based on NODEMCU ESP8266

With the prompt development in wireless communication, in addition to the evolution of wireless patient monitoring system, and to reduce the death of a big number of patients who endear as a result of heart failure or sudden high temperature in children. This paper proposed a sophisticated method of observation human body parameters like temperature measurements with employ at NodeMcu ESP8266 unit in the Internet of Things (IoT). This prototype is based on NodeMcu module (a static access point that provides the WIFI network, a server, a client and a mobile access point attached to the remote surveillance object) programmed under Arduino IDE and communicating between them via the HTTP protocol.

Design Guidelines for Blockchain-Assisted 5G-UAV Networks

Fifth generation (5G) wireless networks are designed to meet various end-user quality of service (QoS) requirements through high data rates (typically of gigabits per second) and low latencies. Coupled with fog and mobile edge computing, 5G can achieve high data rates, enabling complex autonomous smart city services such as the large deployment of self-driving vehicles and large-scale artificial-intelligence-enabled industrial manufacturing. However, to meet the exponentially growing number of connected IoT devices and irregular data and service requests in both low- and high-density locations, the process of enacting traditional cells supported through fixed and costly base stations requires rethought to enable on-demand mobile access points in the form of unmanned aerial vehicles (UAV) for diversified smart city scenarios. This article envisions a 5G network environment that is supported by blockchain-enabled UAVs to meet dynamic user demands with network access supply. The solution enables decentralized service delivery (drones as a service) and routing to and from end users in a reliable and secure manner. Both public and private blockchains are deployed within the UAVs, supported by fog and cloud computing devices and data centers to provide a wide range of complex authenticated service and data availability. Particular attention is paid to comparing data delivery success rates and message exchange in the proposed solution against traditional UAV-supported cellular networks. Challenges and future research are also discussed with highlights on emerging technologies such as federated learning.

A novel communication framework between MANET and WSN in IoT based smart environment

Internet of Things (IoT) has become an emerging platform for connecting real-world objects for desired service provisioning via the Internet. The real-world devices or objects in IoT enable a smart environment with the help of Mobile Ad hoc Networks (MANETs) and Wireless Sensor Networks (WSNs). However, the integration of MANET and WSN in the IoT environment requires a flexible and unified framework for efficient and secure communication between intelligent objects or devices. The state-of-art works in this direction lack standard communication framework for effective implementation of MANET with WSN. In this paper, an efficient and secure communication framework for interconnecting MANET and WSN devices is presented. The proposed communication framework comprises different phases such as collecting data using sensors, sending the data to data processing centers via the mobile access points and finally forwarding the data to data centers for analysis, decision making and reporting purposes. The proposed integration solution is discussed in detail and is evaluated with a case study on data harvesting in rural areas. The efficacy of the proposed framework is reported which will significantly drive the integration of MANET and WSN in future internet using smart objects.

SmartDR:A device-to-device communication for post-disaster recovery

Natural disasters, such as earthquakes, can cause severe destruction and create havoc in the society. Buildings and other structures may collapse during disaster incidents causing injuries and deaths to victims trapped under debris and rubble. Immediately after a natural disaster incident, it becomes extremely difficult for first responders and rescuers to find and save trapped victims. Often searches are carried out blindly in random locations, which delay the rescue of the victims. This paper introduces a Smartphone Assisted Disaster Recovery (SmartDR) method for post-disaster communication using Smartphones. SmartDR utilizes the device-to-device (D2D) communication technology in Fifth Generation (5G) networks, which enables direct communication between proximate devices without the need of relaying through a network infrastructure, such as mobile access points or mobile base stations. We examine a scenario of multi-hop D2D communication where smartphones carried by trapped victims and other people in disaster affected areas can self-detect the occurrence of a disaster incident by monitoring the radio environment and then can self-switch to a disaster mode to transmit emergency help messages with their location coordinates to other nearby smartphones. To locate other nearby smartphones also operating in the disaster mode and in the same channel, each smartphone runs a rendezvous process. The emergency messages are thus relayed to the functional base station or rescue centre. To facilitate routing of the emergency messages, we propose a path selection algorithm, which considers both delay and the leftover energy of a device (a smartphone in this case). Thus, the SmartDR method includes: (i) a multi-channel channel hopping rendezvous protocol to improve the victim localization or neighbour discovery, and (ii) an energy-aware multi-path routing (Energy-aware ad-hoc on-demand distance vector or E-AODV) protocol to overcome the higher energy depletion rate at devices associated with single shortest path routing. The SmartDR method can guide search and rescue operations and increase the possibility of saving lives immediately aftermath a disaster incident. A simulation-based performance study is conducted to evaluate the protocol performance in post-disaster scenario. Simulation results show that a significant performance gain is achievable when a device utilizes the channel information for the rendezvous process and the leftover energy for routing path selection. Our results show that peer discovery in multi-channel D2D environment can be significantly improved when channel quality information is considered in CH sequence design. Moreover, selecting a routing path based on LoE of a device and the standard deviation of residual energy of a path, can not only enhance the network lifetime, but also reduce the chance of network being partitioned.

A New Paradigm for Outpatient Diagnosis and Treatment of Lower Urinary Tract Symptoms Utilizing a Mobile App/Software Platform and Remote and In-Office Visits: A Feasibility Study.

This pilot/feasibility study evaluated a new diagnostic and treatment paradigm for patients with lower urinary tract symptoms using a software platform comprised of a mobile app, validated patient reported outcome questionnaires, bladder diaries and remote patient monitoring. New urology referrals for lower urinary tract symptoms completed validated lower urinary tract symptoms questionnaires and 24-hour bladder diaries on a mobile app. Patients were triaged based on symptom severity into an urgent or routine office visit or a remote visit. Outcome metrics assessed include acceptability, practicality, implementation and integration. Of 500 urology consults there were 226 (45%) patients with new lower urinary tract symptoms referrals of whom 201 (89%) had email addresses. In all there were 182 men and 19 women, aged 18 to 87 years (mean 59, SD 17), of whom 71/201 (35%) registered, 57/71 (80%) completed the app and 41/57 (72%) elected remote visits. Mean time from urology referral to initiation of a remote or in-office diagnostic and treatment plan was 7.4 days (SD 5.9) and 7.7 days (SD 7.6), respectively. Of patients who completed the app 72% were triaged to a remote visit. Time from urology referral to initiation of remote or in-office diagnostic and treatment plan averaged 1 week. This paradigm for management of lower urinary tract symptoms has potential to optimize the clinical workflow, improve health care outcomes and reduce costs.

Throughput Optimization for Cognitive UAV Networks: A Three-Dimensional-Location-Aware Approach

An effective throughput optimization problem is studied in cognitive unmanned aerial vehicle networks (CUAVNs), where a leading unmanned aerial vehicle (LUAV) serving as an aerial mobile access point and sensing node receives data from a group of following unmanned aerial vehicles (FUAVs). For the case of single FUAV, the joint optimizing of three-dimensional location and spectrum sensing duration of LUAV is formulated to maximize FUAV’s throughput. The original non-convex problem is tackled by iteratively optimizing two convex sub-problems. For the case of multiple FUAVs, the preferable LUAV location of each FUAV can be individually calculated by using the algorithm developed for the single FUAV case, and then the final LUAV location is obtained by solving a well-formulated weighted sum problem. Numerical results show that our proposed single FUAV algorithm and throughput weighted sum based on multiple FUAVs algorithm can approach the optimal one with only 2% performance loss. Moreover, compared to the only time-dimension spectrum sensing scheme, the effective throughput of FUAV rises about 500% with the proposed schemes.

Remote monitoring of an object using a wireless sensor network based on NODEMCU ESP8266

<p>In recent years, wireless sensors networks (WSNs) have been imposed as an effective means of interconnection with simultaneous communication and information processing. They allow operating with sensors at low cost and low power consumption in various application areas such as ecosystem monitoring, detection and monitoring of objects and smart cities, etc.This paper describes the development of a system to detect the presence of an object and monitor it. This prototype is based on four NodeMcu modules (a static access point that provides the WIFI network, a server, a client and a mobile access point attached to the remote surveillance object) programmed under Arduino IDE and communicating between them via the HTTP protocol. The remote monitoring of the object for a linear disposition of the nodes used is based on the existence of the mobile access point in the HTTP client field.</p>

역사적 유물을 모티브로 한 모바일 AP 디자인 개발에 관한 연구-중국 산서성 지역 출토 유물 중심으로-

역사적 유물을 모티브로 한 모바일 AP 디자인 개발에 관한 연구-중국 산서성 지역 출토 유물 중심으로-

Analysis and Improvement of a NTRU-Based Handover Authentication Scheme

Recently, Chen and Peng proposed a NTRU-based handover authentication scheme for wireless networks, aiming to provide a quantum-resistant solution with low complexity. Unfortunately, we find that there may exist an inside attack against their scheme. Specifically, in their scheme any mobile node or access point can recover the authentication server’s long-term secret. Since this secret plays a vital role in Chen and Peng’s scheme, any one with this secret can impersonate the authentication server. Fortunately, we have come up with a simple and efficient solution to thwart the proposed attack, which can maintain all the features of the original protocol while incurring little additional communication and computational costs.

RSS-Fingerprint Dimensionality Reduction for Multiple Service Set Identifier-Based Indoor Positioning Systems

Indoor positioning systems (IPS) have been recently adopted by many researchers for their broad applications in various Internet of Things (IoT) fields such as logistics, health, construction industries, and security. Received Signal Strength (RSS)-based fingerprinting approaches have been widely used for positioning inside buildings because they have a distinct advantage of low cost over other indoor positioning techniques. The signal power RSS is a function of the distance between the Mobile System (MS) and Access Point (AP), which varies due to the multipath propagation phenomenon and human body blockage. Furthermore, fingerprinting approaches have several disadvantages such as labor cost, diversity (in signals and environment), and computational cost. Eliminating redundancy by ruling out non-informative APs not only reduces the computation time, but also improves the performance of IPS. In this article, we propose a dimensionality reduction technique in a multiple service set identifier-based indoor positioning system with Multiple Service Set Identifiers (MSSIDs), which means that each AP can be configured to transmit N signals instead of one signal, to serve different kinds of clients simultaneously. Therefore, we investigated various kinds of approaches for the selection of informative APs such as spatial variance, strongest APs, and random selection. These approaches were tested using two clustering techniques including K-means and Fuzzy C-means. Performance evaluation was focused on two elements, the number of informative APs versus the accuracy of the proposed system. To assess the proposed system, real data was acquired from within the College of Engineering and Applied Sciences (CEAS) at the Western Michigan University (WMU) building. The results exhibit the superiority of fused Multiple Service Set Identifiers (MSSID) performance over the single SSID. Moreover, the results report that the proposed system achieves a positioning accuracy <0.85 m over 3000 m2, with an accumulative density function (CDF) of 88% with a distance error of 2 m.

Sustainable e-learning for theologians in hard-to-reach areas: The Bible Online Learner App

Madagascar is ranked at 154 on the human development index. During the dry period, it is hit by daily blackouts. Internet connections are poor. This makes e-learning difficult. My paper will present a possible solution to this problem: I will present a technical solution of how to realize e-learning systems for theologians in hard-to-reach areas by using Raspberry Pi mini-computers as servers and explain why so-called progressive web apps, which are single page-apps are now suitable for this approach; rather I will show how a client-server solution with a Raspberry Pi Server hosting an Emdros database of the Hebrew Bible and a native Android App, written in Java can provide Bible Online Learner Network Kits. The Raspberry Pis are set up as servers in independent computer networks, which do not rely on an internet connection and which are mobile access points. These servers handle the backend code, have the logic to create random exercises for the Bible OL App and send this information via a JSON string to the client app, realized as an Android app written in Java. For this client-side development I paid special attention to the challenges of computer illiterate students. I solved these challenges by using picture-based logins. As a result I developed the design für the Bible Online Learner App and the Bible Online Network Kit, which works with power banks as uninterruptable power supplies as well as a solar power kit, which enables e-learning in hard-to-reach areas in Africa even during the dry season.