Characterization of off-body area network channels during walking

In this work, the off-body area network channel characteristics during walking were investigated using finite-difference time-domain. The channels were investigated in terms of fade variation and the correlation between different channels. Larger fade variations were experienced by the channel with the absence of line-of-sight, due to constructive and destructive interference as the distance between the end nodes changes. The channels showed significant correlation and hence a multivariate normal distribution was considered. The distribution has the capability of modeling channels jointly which make it easier for network analysis. The resulting estimated multivariate distributions fit well with the simulated data

Characterization of dynamic wireless body area network channels during walking

In this work, finite-difference time-domain was used for the investigation of dynamic wireless body area network channel characteristics during walking, thus accounting for dynamic aspects and body postures. This involves the study of on-body, off-body, and body-to-body communication in an empty environment, at the center frequency of 2.45 GHz. The channels were investigated in terms of fade variation and their corresponding amplitude distributions. For on-body channels, the fade variation was found to be periodic, with larger fade variations for the channels involving the nodes at the hand and thigh. For off-body and body-to-body channels, channels with the absence of line of sight experienced constructive and destructive interference as the distance between the end nodes changes, resulting in larger fade variations. For the amplitude distribution of the channels, a multivariate normal distribution was considered. The distribution has the capability of modeling channels jointly which makes it easier for network analysis and was considered because of the significant correlation between the channels. The resulting estimated multivariate distributions fit well with the simulated data, for on-body, off-body, and body-to-body channels

A Comparative Study of Wireless Channel Propagation Characteristics in Industrial and Offce Environments

This paper presents the comparative results of channel measurements in an industrial facility and an indoor office. The frequency domain channel measurements have been carried out in the frequency band of 0.8.2.7 GHz. Results on channel characteristic parameters such as large-scale path loss, shadowing, power delay profile (PDP), root-mean-square (rms) delay spread, Ricean K-factor and the multiple-input and multiple-output (MIMO) channel capacity measurements for indoor office and industrial scenario are presented and compared. The results indicate some different channel propagation characteristics of the industrial wireless channel from the indoor office channel owing to its different physical characteristics, which should take into consideration when designing robust industrial wireless communication system.acceptedVersio

Performance Analysis of Hybrid-ARQ with Chase Combining over Cooperative Relay Network with Asymmetric Fading Channels

This paper investigates the performance of cooperative relay networks in the presence of hybrid automatic repeat request (ARQ) with delay constraint. It analyzes the scenarios where the relay channels are asymmetric (i.e., the links of the wireless relay network follow different fading distributions) due to relaying position and/or due to time varying channel fading. The analytical expressions for the outage probability and throughput are derived for different asymmetric fading channels. The benefit of combined implementation of relaying and hybrid-ARQ is illustrated. Our results show that the performance in terms of outage probability and delay-limited throughput is better when the relay node is in line-of-sight (LoS) with respect to the source node compared to being close to the destination node. This performance difference is quantified and can be as large as several dB depending on the specific configuration. This difference in performance narrows when the maximum hybrid-ARQ transmission rounds increase or when the information transmission rate decreases.acceptedVersion© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Exploiting Dispersive Power Gain and Delay Spread for Sybil Detection in Industrial WSNs: A Multi-Kernel Approach

Industrial wireless sensor networks (IWSNs) promote innovations in the industry such as structural status mapping, instrument fault diagnosing, and oriented automation system associating. However, due to the shared nature of the wireless propagation environment, the emerging sensor nodes (SNs) with wireless properties are vulnerable to external malicious attacks. The security threats, especially Sybil attacks, impose great difficulties in fulfilling quality requirements of industrial applications. What is more complicated is that the harsh industrial environment brings about new challenges which can degrade the accuracy of detecting Sybil threats. In this paper, we focus on how to detect the malicious packets transmitted from Sybil attackers without adding extra authentication overhead into the transmission frame. We develop a multi-Kernel-based expectation maximization (MKEM) scheme to detect Sybil attacks in IWSNs. Instead of directly investigating the radio resource of SNs, we produce channel-vectors which are extracted from the power gain and delay spread of the channel impulse response obtained from the received packets to represent each SN. Specifically, a kernel-oriented method is designed to discriminate the malicious packets from benign ones without establishing a pre-defined database of channel features of all SNs. Meanwhile, we allocate different kernel weights to the proposed kernels and combine them to improve the discrimination ability of the scheme. Moreover, a kernel parameter optimization method is developed to regulate each kernel weight and parameter to reduce the effects of transmission impairments in IWSNs. To avoid poor detection accuracy when the number of Sybil attackers increases, we use the gap statistical analysis method to verify and EM method to summarize the detection results. The simulation results show that the proposed MKEM scheme can achieve high accuracy on detecting malicious packets transmitted from Sybil attackers from benign on...acceptedVersion© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Capacity Analysis of PLC Systems over Rayleigh Fading Channels with Nakagami- Additive Noise

Power line communication (PLC) is an emerging technology for the realization of smart grid and home automation. It utilizes existing power line infrastructure for data communication in addition to the transmission of power. The PLC channel behaves significantly different from the wireless channel; and it is characterized by signal attenuation as well as by additive noise and multiplicative noise effects. The additive noise consists of background noise and impulsive noise; while the multiplicative noise results in fading of the received signal power. This paper investigates the impact of the channel characteristics on the capacity performance of a PLC system over Rayleigh fading channel with frequency-distance dependent attenuation and colored Nakagami-m distributed additive noise. We derive the exact closed-form expressions for the distribution of the instantaneous signal-to-noise ratio (SNR). Since closed-form expression of the capacity for channels with non-Gaussian noise is extremely difficult to obtain, we choose to use the lower limit of the PLC capacity to facilitate our analysis. Monte Carlo simulation results are used to verify the derived analytical expressions.acceptedVersion© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Survey of Millimeter-Wave Propagation Measurements and Models in Indoor Environments

The millimeter-wave (mmWave) is expected to deliver a huge bandwidth to address the future demands for higher data rate transmissions. However, one of the major challenges in the mmWave band is the increase in signal loss as the operating frequency increases. This has attracted several research interests both from academia and the industry for indoor and outdoor mmWave operations. This paper focuses on the works that have been carried out in the study of the mmWave channel measurement in indoor environments. A survey of the measurement techniques, prominent path loss models, analysis of path loss and delay spread for mmWave in different indoor environments is presented. This covers the mmWave frequencies from 28 GHz to 100 GHz that have been considered in the last two decades. In addition, the possible future trends for the mmWave indoor propagation studies and measurements have been discussed. These include the critical indoor environment, the roles of artificial intelligence, channel characterization for indoor devices, reconfigurable intelligent surfaces, and mmWave for 6G systems. This survey can help engineers and researchers to plan, design, and optimize reliable 5G wireless indoor networks. It will also motivate the researchers and engineering communities towards finding a better outcome in the future trends of the mmWave indoor wireless network for 6G systems and beyond.publishedVersio

Time dynamic channel model for broadband fixed wireless access systems

Abstract Broadband fixed wireless access (BFWA) systems have been recognized as an effective first kilometer solution for broadband services to residential and business customers. The large bandwidth available in frequency bands above 20 GHz makes radio systems with very high capacities possible. Users can be offered bit rates in the order of several hundred Mbit/s, making (in terms of capacity) such radio links an alternative to optical fibre in many cases. High capacities BFWA links can be used to serve individual users directly or function as a backbone for lower capacity systems (both wire line and wireless) for local distribution of data. In addition, wireless always offers the freedom of broadband being away from the fixed access point. At mm-wavelengths the signals are sensitive to time dynamic propagation degradation caused by precipitation, vegetation and reflections/multipath from e.g. building surfaces. BFWA need to cope with location and time dependent interference and employ techniques such as interference cancellation and adaptive modulation and coding to optimise throughput during varying traffic load conditions. Multiple input multiple output (MIMO) and space-time coding, as well as adaptive (smart) antennas require knowledge of the channel dynamics as well. The objective of this master thesis is to develop a realistic time dynamic channel model for BFWA operating above 20 GHz utilising adaptive physical layer techniques. The channel model developed represents the time varying wideband channel impulse response including degradations due to multipath propagation, rain attenuation and vegetation fading. The channel model is suitable for simulating mitigation techniques for interference between base stations as well as adaptive modulation and coding techniques. The Maseng-Bakken statistical dynamic model of rain attenuation was adapted to model the rain attenuation. The dynamic vegetation effect was modelled as Nakagami-Rice distribution with K-factor depending on wind speed. A generic tapped delay line model was developed, in which the number of taps depend on maximum tap delay. This thesis is based on work in the project BROADWAN (www.broadwan.org), partly funded under the Information Society Technologies (IST) priority of the European Commission Sixth Framework Program.

Received Signal Strength Based Gait Authentication

Expansion of wireless body area networks applications, such as health-care, m-banking, and others has lead to vulnerability of privacy and personal data. An effective and unobtrusive natural method of authentication is therefore a necessity in such applications. Accelerometer-based gait recognition has become an attractive solution, however, continuous sampling of accelerometer data reduces the battery life of wearables. This paper investigates the usage of received signal strength indicator (RSSI) as a source of gait recognition. Unlike the accelerometer-based method, the RSSI approach does not require additional sensors (hardware) or sampling of them, but uses the RSSI values already available in all radio devices. Three radio channel features namely, the time series, auto-correlation function, and level crossing rate were extracted from unique signature of the RSSI in relation to the corresponding subject. The extracted features were then used together with four different classification learners, namely decision tree, support vector machine, k-nearest neighbors, and artificial neural network, to evaluate the method. The best performance was achieved utilizing artificial neural network with 95% accuracy when the features were extracted from one on-body radio channel (right wrist to waist), and 98% when the features were extracted from two on-body radio channels (right wrist to waist, and left wrist to waist). The developed RSSI-based gait authentication approach can complement high-level authentication methods for increased privacy and security, without additional hardware, or high energy consumption existing in accelerometer-based solutions.Received Signal Strength Based Gait AuthenticationacceptedVersion© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Nanosilver Inkjet-Printed CPW-Fed Flexible Antenna Sensor for Contactless Liquid Acetone/Water Detection

acceptedVersio