Signal Strength Fluctuations Research Articles

SP-Loc: A crowdsourcing fingerprint based shop-level indoor localization algorithm integrating shop popularity without the indoor map

With the development of indoor localization technology, the location-based services such as product advertising recommendation in the shopping mall attract widespread attention, as precise user location significantly improves the efficiency of advertising push and brings broader profits. However, most of the Wi-Fi-based indoor localization approaches requiring professionals to deploy expensive beacon devices and intensively collect fingerprints in each location grid, which severely limits its extensive promotion. We introduce a zero-cost indoor localization algorithm utilizing crowdsourcing fingerprints to obtain the shop recognition where the user is located. Naturally utilizing the Wi-Fi, GPS, and time-stamp fingerprints collected from the smartphone when user paid as the crowdsourcing fingerprint, we avoid the requirement for indoor map and get rid of both devices cost and manual signal collecting process. Moreover, a shop-level hierarchical indoor localization framework is proposed, and high robustness features based on Wi-Fi sequences variation pattern in the same shop analysis are designed to avoid the received signal strength fluctuations. Besides, we also pay more attention to mine the popularity properties of shops and explore GPS features to improve localization accuracy in the Wi-Fi absence situation effectively. Massive experiments indicate that SP-Loc achieves more than 93% localization accuracy.

The Modelling of Tropical Weather Effects on Ultra-High Frequency (UHF) Radio Signals Using SmartPLS

The interference occurs in radio signals transmission in many communication technologies are attributed to weather variations as well as other environmental factors. This work evaluates some atmospheric variables that have a dominating impact on temporal signal strength fluctuations. The Received Power Level (RPL) of Ultra High Frequency (UHF) communication signals (1800 MHz and 2160 MHz) and three tropical weather predictors (humidity, temperature and wind) were collected using spectrum analyser (KEYSIGHT N9915A) and weather station (Vantage Pro 2) respectively for 24 hours in rainy days. SmartPLS 3.2.6 was used to determine the strongest predictors influence the RPL for UHF frequency. It has been found that changes in weather conditions have affected the signal in which all weather predictors provide a significant relationship to the signal where R2 (coefficient of determination) value is 0.314 for frequency 1800 MHz and 0.254 for frequency 2160 MHz. The findings also show that humidity, temperature and wind are anticorrelations to RPL. However, humidity is found to be the strongest predictor influences the RPL of communication signals for frequency 1800 MHz (β = −0.449, p = 0.000). This model may benefit many sectors such as telecommunication service provider, radio and TV transmission, radio astronomy study, Electromagnetic (EM) researcher and satellite broadcasting.

A joint indoor positioning scheme exploiting pedestrian dead reckoning and radio frequency tomography

ABSTRACTThe pedestrian dead reckoning (PDR) is a popular technique for recognizing a pedestrian’s trajectory. However, its inherent disadvantage of susceptibility to error accumulation limits its performance as the travelled distance is increased. Various techniques are combined with PDR to mitigate the error accumulation by regular position resetting. The radio frequency (RF) Tomography is an emerging technology for localization by sensing the received signal strength (RSS) fluctuation on a line-of-sight wireless link (LOSL). Conventional RF Tomography based schemes need specific large-scale networks and face with the problem of harsh environments and high hardware costs. Thus in this paper, we proposed the flexible and practical GF operators for PDR resetting work, in which we introduce the displacement estimation by PDR technique and the LOSL triggering sequence to build a PDR geometrical formulation (PDR-GF) model, and then this model is optimized by Particle Swarm Optimization (PSO) algorithm for crossing point (CP) estimation on the LOSLs. Finally, the estimated CP is in turn used for regular position resetting. Practical experiments are performed to evaluate the proposed positioning scheme. According to the results, the proposed scheme can achieve a finer accuracy of less than 1 m, outperforming the existing RSS-PDR positioning scheme.

Masquerading Attacks Detection in Mobile Ad Hoc Networks

Due to the lack of centralized identity management and the broadcast nature, wireless ad hoc networks are always a palatable target for masquerading attacks. The attackers can spoof identities of privileged legitimate users for various malicious reasons, such as to launch DoS or DDoS attacks, to access unauthorized information, and to evade the detection and accountability. In the current and limited literature, masquerading attacks are mostly counteracted by signal-strength-based detection systems. However, these schemes are mostly proposed to work for infrastructure-based IEEE 802.11 wireless networks using fixed access points, air monitors, or fixed anchor nodes, which are not suitable for the ad hoc architecture. In this paper, we propose a detection system for masquerading attacks without using fixed anchor nodes or air monitors. We develop an anomaly detection model based on the statistical significant testing for our masquerading detection system that takes into consideration the signal strength fluctuation. We conduct a test bed of Samsung Galaxy-based smartphones in order to analyze the real-world signal strength variation. We also plug the real-world signal strength variation in our model for the evaluation of the detection accuracy. We propose the received signal-strength-based masquerading attack detection scheme, which is carried out first by each node in its one-hop vicinity and then extended to five-hop proximity for broader detection scope and improved accuracy. The proposed scheme is evaluated using an NS-2 network simulator for detection accuracy in different environments. The results obtained indicate that our proposed scheme produces more than 90% true positives.

Performance analysis of an 80 (8 × 10) Gbps RZ-DPSK based WDM-FSO system under combined effects of various weather conditions and atmospheric turbulence induced fading employing Gamma–Gamma fading model

Free space optics (FSO) has the capacity to be a vital element for the design of ubiquitous and reliable systems for next-generation networks owing to its large bandwidth and high data rate support. The last-mile issue finds an efficient solution in FSO in scenarios where fiber deployment is not feasible. However the FSO link is prone to fluctuations in optical signal strength due to various weather conditions and atmospheric turbulence. In this paper, an 80 (8 × 10) Gbps RZ-DPSK based WDM-FSO system is analyzed based on its performance on weather conditions viz. very clear, drizzle, haze, thin fog, moderate fog and thick fog. Link-margin analysis is also done. The turbulence model employed is the Gamma–Gamma fading model. The system is simulated on OptiSystem 14.0.

Pedagogy of wireless fading channels: A MATLAB® demo

Courses in wireless communication systems are offered at undergraduate level electrical engineering programs. One of the topics of study in this course is the signal strength fluctuations in wireless channels referred to as fading arising from the existence of multiple paths between the transmitter and receiver. MATLAB® which is extensively used in engineering courses is an ideal tool to significantly enhance the pedagogy of fading. A demo based on MATLAB® has been developed offering a comprehensive tutorial view of fading. It takes into account several models frequently used to describe fading, such as the Rayleigh, Rician, Nakagami and Gaussian ones. Distributing the p-coded MATLAB® script to the students and allowing them to explore the various aspects of fading and refining the script to include additional elements based on their responses, the demo was simplified, expanded and thus, made more demonstrative of the concepts. The final version of MATLAB® demo allows the users to understand and appreciate the relationship of the number of paths and the strength of the line of sight component (LOS) to the various models based on the statistical validation providing a holistic picture of the short-term fading seen in wireless systems.

ZigBee-based Sensor Network for Indoor Location and Tracking Applications

Practical asset and people tracking in indoor scenarios using Received Signal Strength (RSS) ZigBee-based sensor network is presented. The Indoor Location System (ILS) is based on a novel algorithm that uses relative field levels gathered by a set of transmitter nodes. These levels are introduced into a cost function which minimum gives the asset location estimation. The use of relative field levels-based algorithm avoids the need of system calibration due to signal strength fluctuation. The method is tested in two real indoor scenarios: the first example is devoted to evaluate the influence of the number of transmitting nodes on the position estimation accuracy as well as the number of samples to be averaged aiming to reduce uncertainty. The second example shows a realistic case of asset tracking, also studying the influence of sample averaging and number of transmitting nodes.

Sensor Network and Inertial Positioning Hybridization for Indoor Location and Tracking Applications

An indoor location system (ILS) for practical asset and people tracking in indoor scenarios using received signal strength (RSS) ZigBee-based sensor network and inertial sensors is presented. A novel algorithm that uses differential signal levels gathered from a set of transmitter nodes is developed for processing RSS data. These levels are introduced into a cost function whose minimum gives the asset location estimation. The use of differential field levels-based algorithm avoids the need of system calibration due to signal strength fluctuation. Moreover, position accuracy is improved by adding inertial sensor information. The method is tested in a real scenario, demonstrating practical indoor positioning when combining ZigBee-based sensor network and inertial sensors information. The influence of the number of ZigBee nodes on the position estimation accuracy has been analysed.

Extend Your Journey: Considering Signal Strength and Fluctuation in Location-Based Applications

Reducing the communication energy is essential to facilitate the growth of emerging mobile applications. In this paper, we introduce signal strength into location-based applications to reduce the energy consumption of mobile devices for data reception. First, we model the problem of data fetch scheduling, with the objective of minimizing the energy required to fetch location-based information without impacting the application's semantics adversely. To solve the fundamental problem, we propose a dynamic-programming algorithm and prove its optimality in terms of energy savings. Then, we perform postoptimal analysis to explore the tolerance of the algorithm to signal strength fluctuations. Finally, based on the algorithm, we consider implementation issues. We have also developed a virtual tour system integrated with existing Web applications to validate the practicability of the proposed concept. The results of experiments conducted based on real-world case studies are very encouraging and demonstrate the applicability of the proposed algorithm toward signal strength fluctuations .

Analysis of failure mechanisms in fatigue test of reinforced concrete beam utilizing acoustic emission

The acoustic emission technique is used for monitoring the fatigue failure mechanisms in reinforced concrete beam under three point bending. The analysis was conducted by using the bathtub curve method plotted from acoustic emission data. In this study, the fatigue behavior was divided into three stages. The first stage is involved with the decreasing failure rate, known as early life failure or burn-in phase, the second stage is characterized by constant failure rate and the third stage is called the burn-out phase which is an increase of failure rate. The three parameters used in analyzing is the fatigue behavior for each stage of failure which are severity, signal strength and the cumulative signal strength. From severity analysis, the range of each stage of failure had been determined while from signal strength analysis, the initiation of distribution of crack had been detected through the fluctuation of signal strength. Cumulative signal strength parameter provides a clearer view of the initiation an...

신호 세기 변동에 강인한 WPS용 라디오 맵 구축 기법

신호 세기 변동에 강인한 WPS용 라디오 맵 구축 기법

A Signal Strength Fluctuation Prediction Model Based on the Random Forest Algorithm

This article describes the effect of the weather on radio wave propagation in a mobile telecommunication network. The research is focused on urban and countryside environments where a correlation between the received signal power level and weather conditions is found using the Random Forest algorithm as a signal level approximator. The results achieved in this paper clearly indicate that it is possible to predict the behaviour of the received power level in relationship to atmospheric phenomena. DOI: http://dx.doi.org/10.5755/j01.eee.20.5.7112

Three-Dimensional Node Localization Algorithm for WSN Based on Differential RSS Irregular Transmission Model

The localization accuracy of the conventional three- dimensional (3D) node localization algorithm based on received signal strength (RSS) is restricted by the random signal strength fluctuation caused by the irregular propagation environments. In this paper, we propose an improved localization algorithm based on a differential RSS distance estimation algorithm to minimize the influence of the path loss exponent error. Furthermore, considering the influence of degree of irregularity (DOI), we propose a new radio model and obtain numerically the relation between DOI and the variation of signal transmission ranges. A spherical shell with certain finite thickness is then used to characterize the transmission range irregularity. The simulation results show the path loss exponent has no effect on localization error in the proposed algorithm. The localization errors for various DOIs are significantly lower than the conventional 3D algorithm for different densities of anchor nodes.

A Pedagogic Approach to Cascaded Fading Channels and Diversity in Wireless Systems

College programs in electrical engineering offer courses in wireless communications. One of the complex topics of instruction in these courses is fading which deals with signal strength fluctuations. While many simple fading models exist, a cascaded approach to fading provides a general means to describe these fluctuations in wireless channels including keyhole and multi-hop relay channels. In this approach, the signal strength is expressed as the product of several random components. Such a methodology is complicated by the fact that the probability density functions of the signal-to-noise ratio cannot be expressed in simple forms. Furthermore, the study of diversity to mitigate fading is made difficult by the absence of analytical expressions for the densities, error rates and outages. To overcome these difficulties, a MATLAB-based simulation techniques is proposed and demonstrated. The beneficial effects of diversity in mitigating fading are established through density and distribution functions as well as quantitative measures of performance such as the error rates and outage probabilities. It is suggested that the MATLAB-based approach can provide a didactic means to facilitate the understanding of fading and fading mitigation.

A cyber-physical approach to secret key generation in smart environments

Encrypted communication in wireless sensor networks oftentimes requires additional randomness and frequent re-keying in order to avoid known-plain text attacks. Conventional approaches for shared secret generation suffer however from various disadvantages, such as necessity of a trusted third party, protocol scalability, and especially, the computational resources needed for performance-demanding public-key protocols. To appropriately respond to the increasing disproportions between a computationally powerful adversary and lightweight wireless devices, a cyber-physical approach has recently attracted much attention. The general idea is to leverage the properties of the physical world and include them in a design of lightweight security protocols. Especially valuable physical property is the erratic and unpredictable nature of multi-path signal propagation which has already shown itself as a rich source of randomness. This work presents a new cyber-physical approach in order to make secure wireless sensor communications and proposes a secret key extraction algorithm that leverages signal strength fluctuations resulting from dynamic physical environments, e.g. environments experiencing human movements. In particular, this work presents a systematic experimental evaluation by using a real-world sensor network, and analyzes the impact of different moving patterns on legitimate devices and an eavesdropper. Finally, this work quantifies the main factors that influence the key establishment algorithm and propose a protocol which allows secret sharing in an effective and efficient way.

A Scrambling Method for Fingerprint Positioning Based on Temporal Diversity and Spatial Dependency

Signal strength fluctuation is one of the major problems in a fingerprint-based localization system. To alleviate this problem, we propose a scrambling method to exploit temporal diversity and spatial dependency of collected signal samples. We present methods on how these properties can be applied to enhance the positioning accuracy of several existing schemes. Simulation studies and experimental results show that the scrambling method can greatly improve positioning accuracy, especially when the tracked object has some degree of mobility.

Exploring GSM data in pervasive environments

PurposeA cell phone that behaves in a manner reflective of the current context has been a goal for the pervasive and ubiquitous research communities for a long time. This paper aims to demonstrate how two aspects of context – location and activity – can be inferred using GSM data present on standard cell phones.Design/methodology/approachA background knowledge of GSM networks is provided, followed by an assessment of the stability of signal strength levels in order to establish their usefulness in inferring aspects of context. A qualitative location system using GSM signals is presented and how to infer the current activity of the cell phone carrier is demonstrated.FindingsThe paper shows that by using the patterns of signal strength fluctuations and changes to the current serving cell and monitored neighbouring cells it is possible to distinguish between various states of movement such as walking, driving a car and remaining stationary.Originality/valueThe paper focuses on the practical aspects of deploying and managing location based services in dynamic outdoor environments.

Adaptive and Fuzzy Approaches for Nodes Affinity Management in Wireless Ad‐Hoc Networks

In most of the ad‐hoc routing protocols, a static link lifetime (LL) is used for a newly discovered neighbors. Though this works well for networks with fixed infrastructures, it is inadequate for ad‐hoc networks due to nodes mobility and frequent breaks of links. To overcome this problem, routing protocols with estimated LL using nodes affinity were introduced. However, these protocols also used the static estimated LL during the connection time. In contrast to that, in this paper two methods are presented to estimate LL based on nodes affinity and then continually update those values depending on changes of the affinity. In the first method, linear function is used to map the relationship between the signal strength fluctuation and LL. In the second method, fuzzy logic system is used to map this relationship in a nonlinear fashion. Significance of the proposed methods is validated using simulation. Results indicate that fuzzy method provides the most efficient and robust LL values for routing protocols.

Adaptive vertical handoff algorithm in heterogeneous networks

The integration of cellular network (CM) and wireless local area network (WLAN) is the trend of the next generation mobile communication systems, and nodes will handoff between the two kinds of networks. The received signal strength (RSS) is the dominant factor considered when handoff occurs. In order to improve the handoff efficiency, this study proposes an adaptive decision algorithm for vertical handoff on the basis of fast Fourier transform (FFT). The algorithm makes handoff decision after analyzing the signal strength fluctuation which is caused by slow fading through FFT. Simulations show that the algorithm reduces the number of handoff by 35%, shortens the areas influenced by slow fading, and enables the nodes to make full use of WLAN in communication compared with traditional algorithms.

Anomalous sea surface reverberation scale model experiments

Low frequency sea surface sound backscattering from ∼100 Hz to a few kHz observed from the 1960s broadband measurements using explosive charges to the Critical Sea Test measurements conducted in the 1990s is substantially higher than explained by rough sea surface scattering theory. Alternative theories for explaining this difference range from scattering by bubble plumes/clouds formed by breaking waves to stochastic scattering from fluctuating bubble layers near the sea surface. In each case, theories focus on reverberation in the absence of the large-scale surface wave height fluctuations that are characteristic of a sea that produces bubble clouds and plumes. At shallow grazing angles, shadowing of bubble plumes and clouds caused by surface wave height fluctuations may induce first order changes in the backscattered signal strength. To understand the magnitude of shadowing effects under controlled and repeatable conditions, scale model experiments were performed in a 3 m × 1.5 m × 1.5 m tank at the Technical University of Denmark. The experiments used a 1 MHz transducer as the source and receiver, a computer controlled data acquisition system, a scale model target, and a surface wave generator. The scattered signal strength fluctuations observed at shallow angles are characteristic of the predicted ocean environment. These experiments demonstrate that shadowing has a first order impact on bubble plume and cloud scattering strength and emphasize the usefulness of model scale experiments for studying underwater acoustic events under controlled conditions.