Connectivity In Wireless Networks Research Articles

Performance analysis of LoRa in the 2.4 GHz ISM band: coexistence issues with Wi-Fi

Within realization of the visions of the Internet-of-Things (IoT), Low Power Wide Area Networks (LPWANs) are undoubtedly one of the fields that attract high interest from both academic and industrial fields. To ensure reliable data exchange between low power and low data rate devices across long distances, which are the main aims of LPWAs, it is necessary to utilize advanced wireless communication technologies. Emerging LPWA technologies, for instance Long-Range (LoRa) and SigFox, offer many benefits for IoT. These technologies have been primarily developed for sub-GHz frequency bands, but, in the future, their deployment is also considered in the 2.4 GHz industrial, scientific and medical (ISM) bands. However, these unlicensed ISM bands are also used by other technologies for Wireless Local Area Network (WLAN also denoted as Wi-Fi) connectivity and other services, and therefore, coexistence issues can occur here in the future. The main aim of this paper is to perform a performance analysis of the LoRa radio signals interfered by Wi-Fi, using interferers confirming to different IEEE 802.11 family standards, in the 2.4 GHz ISM band. For this purpose, an automated measurement setup and methodology on Physical (PHY) layer are proposed and used. In general, the evaluated results confirm theoretical assumptions on high robustness of LoRa against interferences. However, our results reveal that this robustness of LoRa is highly depending not only on the used LoRa system parameters, but also on the interferer properties and the assumed coexistence scenarios (co-channel, in-band and adjacent channel interferences).

830 Voice Activated Tool: A Successful Assistance for Patients with Limited Hand Function

Abstract Introduction Burn survivors require significant assistance in physical functions and independence during their recovery and rehabilitation phase. Amputation, splints, bulky dressings, and pain attribute to limited or lack of hand mobility. Voice activated tools (VAT) have rapidly grown in popularity including in healthcare. Prior to the implementation of this project, patients mostly depended on soft touch call lights which were suboptimal for most patients. We piloted VAT to assist in hand functions of patients with limited or lack of hand mobility. Methods The project was piloted in collaboration with IT, Occupational Therapy, Nursing, and patients’ family. IT enabled with uninterrupted source of wireless network connection in the patients’ room. Voice assistance was incorporated both through mobile phone and an added virtual assistant tool. Patients’ personal devices were used to promote utilization of stored information in the device. Occupational therapist assisted in mounting the device through a spring clamp and gooseneck cell phone holder to visualize the device screen. Speech therapists, nurses, and patient family helped in training the patient to voice appropriate commands. The patient utilized VAT for a wide variety of purposes including calling nurses, ordering hospital meals, phone calls, music, web browsing, and more. A survey was done to evaluate health care team’s opinion on VAT usage. Results Of the total burn team members, 34 (77%) staff responded to the survey including physicians, nurses, therapists, and nursing assistants. All survey responders reported VAT as a useful tool to be offered to all future patients with limited hand mobility. Majority (74%) of responders witnessed or participated in the successful use of VAT during the pilot period. Survey participants reported three reasons for the current soft touch call light system to be suboptimal: 1.Too sensitive, 2. Not all patients can use it 3. Conclusions Voice activated tool can be successfully utilized for assisting patients with limited hand mobility considering the current available tool is suboptimal. Adoption of a simple and popular technology of VAT can be easily incorporated in hospitals through collaboration of health care team. Applicability of Research to Practice Use of VAT could be successfully implemented for other hospital units including paralyzed patients, blind, and patients with orthopedic conditions or trauma to hands. Additionally, VAT could be incorporated in to rehabilitation and home training of patients with limited hand mobility. Further, VAT could be considered in the designing and planning of hospitals.

Design and analysis of a hybrid mobility management scheme for wireless mesh network to handle highly mobile mesh clients

Nowadays, the importance of continuous connectivity of wireless network has increased because of increase in the number of applications in handheld devices. For offering continuous connectivity, seamless mobility management is very much necessary. Many mobility management schemes have been proposed. The techniques can broadly classified as, tunnel based scheme and routing based scheme. The tunnel based techniques has the advantage of limited route management packet transmission. But disadvantage is that besides source and destination addresses each of the data packets carry an extra header for routing. In case of routing based scheme, advantage is that the data packets do not carry any extra header for routing. But the disadvantage is that during handoff lots of route management packets are transmitted. As the mesh client speed increases, these problems further increase. Hybrid mobility management technique has been proposed in this paper for minimizing the problems of both tunnel based scheme and routing based scheme. It has been designed to handle highly mobile mesh clients. The proposed scheme routes internet packets using routing table entries. On the other hand, it uses tunneling to route the intranet packets to the destination. The hybrid scheme and some of the existing schemes have been analyzed and compared. Performance comparison shows that the hybrid scheme outperforms these techniques.

A Hybrid Energy Harvesting Design for On-Body Internet-of-Things (IoT) Networks

The Internet-of-things (IoT) has been gradually paving the way for the pervasive connectivity of wireless networks. Due to the ability to connect a number of devices to the Internet, many applications of IoT networks have recently been proposed. Though these applications range from industrial automation to smart homes, healthcare applications are the most critical. Providing reliable connectivity among wearables and other monitoring devices is one of the major tasks of such healthcare networks. The main source of power for such low-powered IoT devices is the batteries, which have a limited lifetime and need to be replaced or recharged periodically. In order to improve their lifecycle, one of the most promising proposals is to harvest energy from the ambient resources in the environment. For this purpose, we designed an energy harvesting protocol that harvests energy from two ambient energy sources, namely radio frequency (RF) at 2.4 GHz and thermal energy. A rectenna is used to harvest RF energy, while the thermoelectric generator (TEG) is employed to harvest human thermal energy. To verify the proposed design, extensive simulations are performed in Green Castalia, which is a framework that is used with the Castalia simulator in OMNeT++. The results show significant improvements in terms of the harvested energy and lifecycle improvement of IoT devices.

A low-cost smartphone controlled sensor based on image analysis for estimating whole-plant tissue nitrogen (N) content in floriculture crops

Monitoring and maintaining plant tissue nitrogen (N) content in the optimal range is crucial for proper growth and quality of floriculture crops. Direct laboratory measurements of tissue N content is destructive, time-consuming and expensive. The equipment costs for indirect measurement of tissue N content are high. Currently, there are no low-cost, reliable and non-destructive techniques for measuring whole-plant tissue N content in floriculture crops. The objective of this study is to develop a low-cost sensor that can instantaneously and non-destructively estimate whole-plant tissue N content in floriculture crops. The technique involves a sensor, smartphone and local computer. The low-cost sensor was built using Raspberry Pis, camera modules and light filters. A smartphone interacts with both the sensor and the local computer using wireless network connection. Using a web-interface, smartphone was connected to the sensor for capturing and transferring plant images to a cloud storage. Subsequently, the smartphone was remotely connected to the local computer with image-processing software. Images were processed to calculate a reflectance ratio (Rratio). Results indicated linear and positive relationships between the laboratory measured whole-plant N content and Rratio (r2 = 0.70) and chlorophyll concentration and Rratio (r2 = 0.71). Further, a model based on stepwise selection (N = 125) indicated that tissue N mostly affected Rratio (partial R2 = 0.66), while other elements in the plant tissue had minimal effect on the ratio. Based on these results, the developed algorithm can be used to instantaneously compute whole-plant tissue N content using the low-cost sensor.

Data security over wireless transmission for enterprise multimedia security with fountain codes

With the explosive growth of multimedia data, Enterprise Multimedia Security (EMS) is a serious matter to maintain enterprise information security. As the rise of social media applications triggers higher bandwidth demand and shorter end-to-end delay requirements, edge computing has emerged as a promising technique to reduce delay. Edge servers are often deployed around mobile devices via a one-hop wireless network connection. However, migrating multimedia data over wireless networks to edge servers for edge computing is vulnerable to eavesdroppers. Ensuring the security of enterprise multimedia data in the edge computing is a top priority. To cater for the data security over wireless transmisson for edge computing, window-based fountain codes, is treated as a feasible technology to compensate this gap. Based on the characteristics of the fountain codes, data security over wireless transmisson is implemented only when the target receiver accumulates enough coding packets in advance of the eavesdropper. In the general wireless transmission, the eavesdropper receives data packets or not depends on whether the wireless channel lose packets. To ensure data security, we introduce the constellation-rotation technique and interfering noise into wireless signal which can disturb the eavesdropper’s signal quality and increase the packet loss in the eavesdropper. Specifically, we study how to partition the video streaming into windows, which takes the end-to-end delay into consideration while guaranteeing lower intercept probability which indicates the probability video data is leaked to the eavesdropper.

Embedded Software Optimization for Computation - Intensive Applications

Optimization metrics for compiled code are not always measured in execution clock cycles on the target architecture. Modern cellular telephone or wireless devices, which may download executables over a wireless network connection or backhaul infrastructure, it is often advantageous for the compiler to reduce the size of the compiled code that must be downloaded to the wireless device. By reducing the size of the code, savings are achieved in terms of bandwidth required for each wireless point of download. These are metrics correlated to the dynamic run-time behaviour of not only the compiled code on the target processor, but also the underlying memory system, caches, DRAM, and buses, etc. Despite new generation of embedded systems are getting innovative and computationally powerful with upcoming embedded processors, the market demands more computational-intensive embedded software to be developed on embedded systems. It is very essential to implement efficient embedded software to meet the market demand of embedded systems. These embedded systems are special-purpose computing systems and built to perform very specific embedded applications. And, these embedded applications mainly use three key resources of embedded systems: (1) CPU (2) Run-time memory (3) Persistent memory i.e. NAND/NOR flash memory. This paper summarizes several effective embedded software optimization techniques to optimize CPU usage, Run-time memory, and Persistent memory.

Utilizing ICT in Sustainning National Development Using Digital Economy and IOT

The pervasive utilization of information Technology devices is in crescendo and taking dynamic shift as the day goes by. This started from using computer system for storing of data, communication and transfer of data and now to the use of computer for online marketing and transaction and remote monitoring of device. With computer and mobile devices now people and sell and promote their services at ease on just a click over the internet. And in recent times the availability of strong wired and wireless network connectivity has led to the idea of internet of things. This idea makes possible for human to machine interaction and machine to machine interaction. This development has promised better and easy life even though with some consequences. It provides smart education allowing student learn from anywhere at any time, smart city, smart homes and e-health. This research focuses on exploring the diverse opportunity provided by the IOT and Digital economy for national development. Considering the present outright and outbreak of Covid-19 pandemic, the effective utilization of these techniques can lead to a boost in economy and un- interruptive and smooth running of government, industries educational institution in the face of natural disaster, compared to the gross damaged in economy, industry and educational institution caused by the Covid-19 pandemic.

Joint Subcarrier and Power Allocation in NOMA: Optimal and Approximate Algorithms

Non-orthogonal multiple access (NOMA) is a promising technology to increase the spectral efficiency and enable massive connectivity in 5G and future wireless networks. In contrast to orthogonal schemes, such as OFDMA, NOMA multiplexes several users on the same frequency and time resource. Joint subcarrier and power allocation problems (JSPA) in NOMA are NP-hard to solve in general. In this family of problems, we consider the weighted sum-rate (WSR) objective function as it can achieve various tradeoffs between sum-rate performance and user fairness. Because of JSPA's intractability, a common approach in the literature is to solve separately the power control and subcarrier allocation (also known as user selection) problems, therefore achieving sub-optimal result. In this work, we first improve the computational complexity of existing single-carrier power control and user selection schemes. These improved procedures are then used as basic building blocks to design new algorithms, namely Opt-JSPA, $\varepsilon$-JSPA and Grad-JSPA. Opt-JSPA computes an optimal solution with lower complexity than current optimal schemes in the literature. It can be used as a benchmark for optimal WSR performance in simulations. However, its pseudo-polynomial time complexity remains impractical for real-world systems with low latency requirements. To further reduce the complexity, we propose a fully polynomial-time approximation scheme called $\varepsilon$-JSPA. Since, no approximation has been studied in the literature, $\varepsilon$-JSPA stands out by allowing to control a tight trade-off between performance guarantee and complexity. Finally, Grad-JSPA is a heuristic based on gradient descent. Numerical results show that it achieves near-optimal WSR with much lower complexity than existing optimal methods.

The complexity of symmetric connectivity in directional wireless sensor networks

In this paper, we investigate the Antenna Orientation (AO) and Antenna Orientation and Power Assignment (AOPA) problems concerning symmetric connectivity in Directional Wireless Sensor Networks (DWSNs) where each sensor node is equipped with $$ 2 \le k \le 5$$ directional antennas having beam-width $$\theta \ge 0$$. The AO problem for DWSNs is closely related with the well-known Euclidean Degree-Bounded Minimum Bottleneck Spanning Tree (EBMBST) problem where different cases for the degree bound have been studied. While current works on DWSNs focus on solving each case of k ($$=2,3,4$$) separately, we propose a uniform approach for the AO problem that yields constant-factor approximation algorithms for the AO as well as the EBMBST problem where the degree bound is between 2 and 4. Our method achieves the same constant factors. For the AOPA problem, to the best of our knowledge, our paper provides the first results concerning this problem. We show that the problem is NP-hard when $$2 \le k \le 4$$. We also establish the first constant-factor approximation algorithms for the problem. Finally, we perform some simulations to understand the practical performance of our algorithms.

Automatic detection advantage of problematic Internet users for Wi-Fi signal cues and the moderating effect of negative affect: An event-related potential study

Cognitive bias toward Internet-related cues is an important factor of the formation and maintenance of the addictive behavior of problematic Internet users (PIUs). The development of fiber-optic communication and smartphones has ushered human society into the era of wireless networks. The Wi-Fi signal, the symbol of wireless network connection, represents not only network access but also a channel for communication with others anywhere at any time. Therefore, the Wi-Fi signal cues should be an effective inducer of the addictive behaviors of PIUs. We used images of Wi-Fi signal as Internet-related cues to explore the automatic detection advantage of PIUs for these cues and to determine whether negative affect, another predisposing factor for addiction, can enhance this advantage. We utilized an intergroup design in this study. The PIU and control groups each comprised 30 participants and were randomly assigned to negative or neutral affect priming group. Mismatch negativity (MMN) was induced through the deviant–standard reverse oddball paradigm. Wi-Fi signal cues and neutral cues were used as standard and deviant stimuli, respectively. Results show that the MMN induced by Wi-Fi signal cues in the PIU group was larger than that in the control group. Meanwhile, the MMN induced by Wi-Fi signal cues was considerably enhanced in the PIU group under negative affect priming relative to that in the PIU group under neutral affect priming. Overall, PIUs have an automatic detection advantage for Wi-Fi signal cues, and negative affect can enhance this advantage. Our results suggest that the MMN elicited by Wi-Fi signal cues function as a sensitive neurobiological marker tracing the change of addiction motivation for PIUs.

PCN534 BARRIERS AND FACILITATORS TO IMPLEMENTING ELECTRONIC PATIENT-REPORTED OUTCOMES (PROS) IN CANCER CLINICAL TRIALS: INTERVIEW RESULTS FROM CLINICAL RESEARCH STAFF AND PATIENTS

Collection of patient-reported outcomes (PROs) is common in cancer trials. Implementation approaches and PRO survey completion rates vary. Little is known about research staff and patient impressions of barriers and facilitators to PRO data collection. Thirty-four clinical research associates (CRAs) at sites administering two multicenter cancer trials in the U.S. National Cancer Trial Network that included PROs (NCT01262560 in lung cancer; NCT01515787 in rectal cancer) were randomly selected for semi-structured interviews (N=16) and group discussion (N=18) focused on barriers and facilitators to PRO data collection including technology, training, workflow, effort, and communication. Patients in two trials (NCT01262560; NCT00578006 in multiple cancer types) underwent semi-structured interviews (N=81) on similar topics. Interviews were recorded, transcribed, and de-identified. Coding and thematic analysis employed Dedoose and ATLAS.ti software. CRAs noted challenges training patients with low computer avidity, but found patients gained comfort and facility with experience. Simplifying user interfaces and passwords was suggested. Wireless network connectivity was an early problem for ePROs (before 2015), but subsequently resolved. Balancing PRO tasks with other CRA roles required effort, although the time required for PROs was minute compared to other duties. CRAs reported patient enthusiasm about PROs. Thorough patient training and buy-in from site clinicians were seen as key facilitators of patient compliance. Patients noted that completing PROs became more challenging as they became sicker, but staff reminders and availability of technology assistance helped address this. Technology problems (lost passwords, connectivity) were frustrations. Staff engagement was highly valued. CRAs and patients emphasize the importance of simple ePRO interfaces, minimal password requirements, reliable technology connectivity, thorough initial training, staff reminders to report if a survey is late, and ongoing support and engagement by research staff and clinicians. These elements should be considered in future design and implementation of PRO data collection in clinical trials.

User-Centric Joint Access-Backhaul Design for Full-Duplex Self-Backhauled Wireless Networks

Full-duplex self-backhauling is promising to provide cost-effective and flexible backhaul connectivity for ultra-dense wireless networks, but also poses a great challenge to resource management between the access and backhaul links. In this paper, we propose a user-centric joint access-backhaul transmission framework for full-duplex self-backhauled wireless networks. In the access link, user-centric clustering is adopted so that each user is cooperatively served by multiple small base stations (SBSs). In the backhaul link, user-centric multicast transmission is proposed so that each user’s message is treated as a common message and multicast to its serving SBS cluster. We first formulate an optimization problem to maximize the network weighted sum rate through joint access-backhaul beamforming and SBS clustering when global channel state information (CSI) is available. This problem is efficiently solved via the successive lower-bound maximization approach with a novel approximate objective function and the iterative link removal technique. We then extend the study to the stochastic joint access-backhaul beamforming optimization with partial CSI. Simulation results demonstrate the effectiveness of the proposed algorithms for both full CSI and partial CSI scenarios. They also show that the transmission design with partial CSI can greatly reduce the CSI overhead with little performance degradation.

Challenges With Continuous Pulse Oximetry Monitoring and Wireless Clinician Notification Systems After Surgery: Reactive Analysis of a Randomized Controlled Trial.

BackgroundResearch has shown that introducing electronic Health (eHealth) patient monitoring interventions can improve healthcare efficiency and clinical outcomes. The VIGILANCE (VItal siGns monItoring with continuous puLse oximetry And wireless cliNiCian notification aftEr surgery) study was a randomized controlled trial (n=2049) designed to assess the impact of continuous vital sign monitoring with alerts sent to nursing staff when respiratory resuscitations with naloxone, code blues, and intensive care unit transfers occurred in a cohort of postsurgical patients in a ward setting. This report identifies and evaluates key issues and challenges associated with introducing wireless monitoring systems into complex hospital infrastructure during the VIGILANCE eHealth intervention implementation. Potential solutions and suggestions for future implementation research are presented.ObjectiveThe goals of this study were to: (1) identify issues related to the deployment of the eHealth intervention system of the VIGILANCE study; and (2) evaluate the influence of these issues on intervention adoption.MethodsDuring the VIGILANCE study, issues affecting the implementation of the eHealth intervention were documented on case report forms, alarm event forms, and a nursing user feedback questionnaire. These data were collated by the research and nursing personnel and submitted to the research coordinator. In this evaluation report, the clinical adoption framework was used as a guide to organize the identified issues and evaluate their impact.ResultsUsing the clinical adoption framework, we identified issues within the framework dimensions of people, organization, and implementation at the meso level, as well as standards and funding issues at the macro level. Key issues included: nursing workflow changes with blank alarm forms (24/1030, 2.33%) and missing alarm forms (236/1030, 22.91%), patient withdrawal (110/1030, 10.68%), wireless network connectivity, false alarms (318/1030, 30.87%), monitor malfunction (36/1030, 3.49%), probe issues (16/1030, 1.55%), and wireless network standards. At the micro level, these issues affected the quality of the service in terms of support provided, the quality of the information yielded by the monitors, and the functionality, reliability, and performance of the monitoring system. As a result, these issues impacted access through the decreased ability of nurses to make complete use of the monitors, impacted care quality of the trial intervention through decreased effectiveness, and impacted productivity through interference in the coordination of care, thus decreasing clinical adoption of the monitoring system.ConclusionsPatient monitoring with eHealth technology in surgical wards has the potential to improve patient outcomes. However, proper planning that includes engagement of front-line nurses, installation of appropriate wireless network infrastructure, and use of comfortable cableless devices is required to maximize the potential of eHealth monitoring.Trial RegistrationClinicalTrials.gov NCT02907255; https://clinicaltrials.gov/ct2/show/NCT02907255

Sensor network connectivity models

Introduction: One of the key areas in the research of wireless sensor networks is studying the ways to increase the battery lifeby saving energy in individual devices. The article introduces and discusses a new energy-efficient stochastic measure of the qualityparameter for a wireless sensor network – connectivity, which reflects the ability of a network to establish connections betweenits elements within the boundaries of the sensor field in real time, at a certain level of the sensor device battery charge. Purpose:Identifying the interdependence between the probability-time and probability-energy characteristics, as well as the influence, on thesecharacteristics, of such parameters as geometric dimensions, distribution model of sensor devices within the sensor field, networktopology and message routing algorithms. Results: A new stochastic characteristic of wireless sensor network functioning quality isproposed, called connectivity. It encompasses the spatial, temporal and energy characteristics of the network, making it possible todescribe, from a general point of view, a wide range of problems which arise when you study the functioning of wireless networksat the stages of data collecting, distributing and processing by the sensors. Stochastic connectivity indicators are introduced forwireless sensor networks, describing a network as a whole and allowing you to investigate the delay and blocking of the informationexchange, taking into account the size of the sensor field and the power consumed by individual devices. Models are built for assessingthe probability of wireless sensor network connectivity, message delivery time and delivery time quantile, improving the accuracyof network quality assessments. Practical relevance: The obtained models and methods are supposed to be used in digitalization ofagricultural organizations and in the educational process at Knyagininsky University.

Endüstri 4.0’da Nesnelerin Kablosuz Etki Alanlarına Yapılan Saldırı Metodolojisi

Bu çalışmada Endüstri 4.0 içerisinde yer alan nesnelerin iletişim kurdukları kablosuz ağ bağlantılarının sızma, kırma ve taklit etme teknikleri uygulanarak zafiyet testleri yapılmıştır. Sızma tekniği ile tespit edilen ağdaki tüm cihazların MAC adreslerine erişim sağlanmaktadır. MAC adresi üzerinden de-auth atakları ile cihazlar ağdan düşürülmektedir. Bunun sonucunda Endüstri 4.0 sistemlerinin çalışmasının kesintiye uğradığı veya belirli bir süre durduğu görülmektedir. Kırma teknikleri ile WPS özelliği açık olan dağıtıcıların standart şifreleri tahmin edilerek kablosuz ağa sızmanın veya ağı devre dışı bırakmanın gerçekleştiği görülmektedir. Son olarak kablosuz ağda, oturum taklit etme tekniği ile sisteme yeni bir cihaz ekleyip var olan verilerin silinebileceği veya toplanabileceği görülmektedir. Elde edilen sonuçlar ile kablosuz ağda kullanılan WEP, WPA ve WPA2 güvenliklerinin kendi başlarına yeterli olmadığı görülmüştür. Yapılan sızma metodolojisi ile Endüstri 4.0 sistemlerinde veri güvenliğinin üst düzey olacağı bağlantılarda kablosuz ağ kullanımının çözüm olmayacağı tespit edilmiştir.

Strip-based deployment with cooperative communication to achieve connectivity and information coverage in wireless sensor networks

Coverage and connectivity in wireless sensor network have been studied extensively in existing research works with physical and information coverage. The optimal deployment to achieve both information coverage and connectivity, on arbitrary values of the ratio of rc and rs, has been studied in previous work; meanwhile, the extended strip-based deployment based on information coverage is also studied. Either information coverage or cooperative communication could exploit collaboration of sensor nodes to improve the efficiency of deployment, while how good is strip-based deployment with both information coverage and cooperative communication is worth to be measured when the value of rc/ rs is varied. In this article, the relationship between the density of sensors needed to achieve physical or information coverage and connectivity and the variety of rc/ rs is derived in closed form for strip-based deployment of wireless sensor networks with cooperative communication. Then, a summary of different combinations of coverage and connectivity is provided, that physical or information coverage with or without cooperative communication could be employed to achieve full coverage and connectivity for strip-based deployment. Finally, some new strategy could be proposed based on the fusion of physical and information coverage to improve strip-based deployment. Some numerical results are provided to show the efficiency of all schemes to help researchers design more effective deployment schemes.

Automatic detection advantage of problematic Internet users for Wi-Fi signal cues and the moderating effect of negative affect: An event-related potential study

Cognitive bias toward Internet-related cues is an important factor of the formation and maintenance of the addictive behavior of problematic Internet users (PIUs). The development of fiber-optic communication and smartphones has ushered human society into the era of wireless networks. The Wi-Fi signal, the symbol of wireless network connection, represents not only network access but also a channel for communication with others anywhere at any time. Therefore, the Wi-Fi signal cues should be an effective inducer of the addictive behaviors of PIUs. We used images of Wi-Fi signal as Internet-related cues to explore the automatic detection advantage of PIUs for these cues and to determine whether negative affect, another predisposing factor for addiction, can enhance this advantage. We utilized an intergroup design in this study. The PIU and control groups each comprised 30 participants and were randomly assigned to negative or neutral affect priming group. Mismatch negativity (MMN) was induced through the deviant-standard reverse oddball paradigm. Wi-Fi signal cues and neutral cues were used as standard and deviant stimuli, respectively. Results show that the MMN induced by Wi-Fi signal cues in the PIU group was larger than that in the control group. Meanwhile, the MMN induced by Wi-Fi signal cues was considerably enhanced in the PIU group under negative affect priming relative to that in the PIU group under neutral affect priming. Overall, PIUs have an automatic detection advantage for Wi-Fi signal cues, and negative affect can enhance this advantage. Our results suggest that the MMN elicited by Wi-Fi signal cues function as a sensitive neurobiological marker tracing the change of addiction motivation for PIUs.

Approximation Theory for Connectivity of Ad Hoc Wireless Networks With Node Faults

In this letter, we propose an approximation theory for connectivity of general random geometric graphs (RGGs) with stochastic node faults, which is regarded as an abstract model of ad hoc wireless sensor networks (WSNs) with unreliable nodes. In the model, each node in an RGG is independently at fault and the disconnection probability of a resulting survival network is evaluated. The proposed approximation formula for the probability is asymptotically correct and reveals the phase transition phenomena of connectivity in the model. In addition, we obtain phase transition thresholds of a practical Rayleigh single-input single-output (SISO) model and Rayleigh multiple-input multiple-output (MIMO) model, which shows the effectiveness of the MIMO system against attenuation and random node faults. The numerical results in Rayleigh MIMO model show that the approximation formula well estimates the connection probability even for finite graphs and that it provides useful information for design of WSN immune to node faults.

Distribution of Cell Area in Bounded Poisson Voronoi Tessellations with Application to Secure Local Connectivity

Poisson Voronoi tessellations have been used in modeling many types of systems across different sciences, from geography and astronomy to telecommunications. The existing literature on the statistical properties of Poisson Voronoi cells is vast, however, little is known about the properties of Voronoi cells located close to the boundaries of a compact domain. In a domain with boundaries, some Voronoi cells would be naturally clipped by the boundary, and the cell area falling inside the deployment domain would have different statistical properties as compared to those of non-clipped Voronoi cells located in the bulk of the domain. In this paper, we consider the planar Voronoi tessellation induced by a homogeneous Poisson point process of intensity $\lambda\!>\!0$ in a quadrant, where the two half-axes represent boundaries. We show that the mean cell area is less than $\lambda^{-1}$ when the seed is located exactly at the boundary, and it can be larger than $\lambda^{-1}$ when the seed lies close to the boundary. In addition, we calculate the second moment of cell area at two locations for the seed: (i) at the corner of a quadrant, and (ii) at the boundary of the half-plane. We illustrate that the two-parameter Gamma distribution, with location-dependent parameters calculated using the method of moments, can be of use in approximating the distribution of cell area. As a potential application, we use the Gamma approximations to study the degree distribution for secure connectivity in wireless sensor networks deployed over a domain with boundaries.