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.

Communication Technologies for Smart Grid: A Comprehensive Survey

With the ongoing trends in the energy sector such as vehicular electrification and renewable energy, smart grid is clearly playing a more and more important role in the electric power system industry. One essential feature of the smart grid is the information flow over the high-speed, reliable and secure data communication network in order to manage the complex power systems effectively and intelligently. Smart grids utilize bidirectional communication to function where traditional power grids mainly only use one-way communication. The communication requirements and suitable technique differ depending on the specific environment and scenario. In this paper, we provide a comprehensive and up-to-date survey on the communication technologies used in the smart grid, including the communication requirements, physical layer technologies, network architectures, and research challenges. This survey aims to help the readers identify the potential research problems in the continued research on the topic of smart grid communications

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

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

On Performance Characterization of Cascaded Multiwire-PLC/MIMO-RF Communication System

The flexibility of radio frequency (RF) systems and the omnipresence of power cables potentially make the cascaded power line communication (PLC)/RF system an efficient and cost-effective solution in terms of wide coverage and high-speed transmission. This letter proposes an opportunistic decode-and-forward (DF)-based multi-wire/RF relaying system to exploit the advantages of both techniques. The outage probability, bit error rate, and system channel capacity are correspondingly chosen to analyze the properties of the proposed system, which are derived in closed-form expressions and validated via Monte-Carlo simulations. One can observe that our proposed system outperforms the wireless-only system in terms of coverage and data rate, especially when there exists a non-line-of-sight (NLoS) connection between the transmitter and receiver pair.Comment: 5 pages, 4 figure

Geometry-Based Modeling of Wideband Industrial Indoor Radio Propagation Channels

In this paper, we present a geometrical scattering model for a typical class of industrial indoor environments. The proposed industrial reference model takes into account scattering components arising from metallic structures and the surrounding walls of the investigated environment. Starting from the geometrical scattering model, we derive the analytical expressions of the probability density function (PDF) of the angle of arrival (AoA), PDF of the time of arrival (ToA), and the autocorrelation function (ACF) in the frequency domain. The obtained results reveal a large difference between industrial channels and other home and office environments. The theoretical results of the reference model are validated by simulation results of a channel simulator designed by employing the sum-of-cisoids (SOC) principle. The proposed channel model is useful for the design and performance evaluation of wireless communication systems operating in industrial environments.acceptedVersionnivå

Effect of weather condition on LoRa IoT communication technology in a tropical region: Malaysia

An experimental study on the effect of weather conditions such as solar radiation, humidity, temperature, and rain on the Long Range (LoRa) communication in a tropical region (Malaysia) via a campus environment has been carried out and analyzed. The weather parameters were obtained from an online meteorological weather station (Meteoblue) and the use of a local automatic weather station. A temperature sensor was attached to the LoRa node to measure the onboard temperature. We analyze the diurnal variation and the effects of the weather condition based on the LoRa link in a LoRaWAN setup. A regular pattern of RSSI was observed with stronger RSSI values having a positive correlation with the atmospheric temperature, onboard temperature, and solar radiation during the day but degrades in late evenings. The positive correlation and pattern observed can be attributed to the prevailing metrological conditions and opens room for further research needed for propagation modeling. The RSSI signals and relative humidity, on the other hand, showed no correlation. Furthermore, strong RSSI signals were obtained when the atmospheric temperature was between 30 - 40 °C, and the onboard temperature between 40 - 50 °C. No significant impact was observed on the RSSI signals when the rainfall rates vary from 12 mm/h to 180 mm/h. The study presents useful information to be considered on the effects of weather conditions in the propagation model and deployment of LoRa for IoT communication

Industrial wireless sensor networks: channel modeling and performance evaluation

A complete dynamic wideband channel model for industrial wireless sensor network (WSN) is presented. The model takes into account the noise, interferences, strong vibrations and heavy multipath propagation effects present in harsh industrial environments. The noise is modeled as first-order two state Markov process describing the typical bursty nature of the impulsive noise usually present in industrial environments. The interference effects are modeled as multiple narrowband signals operating on the same frequency band as the desired signal. The multipath propagation is described by assuming the scatterers to be uniformly distributed in space within an elliptical region where the transmitting and receiving nodes are located at the foci of the ellipse. A single degree of freedom vibration model is used to describe the signal path-length variations caused by vibrating scatterers. Furthermore, performance evaluations of IEEE 802.15.4 in terms of bit-error-rate (BER) using the developed channel model are presented. The results show that in addition to spread spectrum techniques, link diversity can further improve the link quality in harsh industrial environments