Assessment of multipath and shadowing effects on UHF band in built-up environments

Ultra-high frequency (UHF) bands are radio frequencies in the range of 300 MHz and 3 GHz. These bands are used for television broadcasting, mobile cellular systems, Wi-Fi, satellite communications and many others. Effective communication link in the UHF band requires direct line of sight between the transmitters and receivers. However, this is not always the case in built-up areas where diverse obstacles such as large buildings, trees, moving objects and hills are present along the communication path. These obstacles result in signal degradation as a result of shadowing (blockages) and multi-path, which are two major causes of signal losses. Path loss models are used in predicting signal losses but, the accuracy of these models depend on the fitness between the model's predictions and measured loses. In this work, the multi-path and shadowing effects on signal impairment were investigated through the use of empirical and semi-empirical path loss models analysis in built-up environments. Electromagnetic field strength measurements were conducted using four television transmitters at UHF bands along four major routes of Osun State, Nigeria. Experimental and simulation results indicated that the empirical models provide a better fit than the semi-empirical models. It was also found that the poor performance of the Knife Edge Model which is a semi-empirical model was traced to the bases of its formulation, which assumed point like knife edge for all obstacles on the path of radio propagation. The work therefore recommends that network planners employ empirical models found suitable for their kind of terrain when faced with coverage planning and optimization.Keywords: Path loss models, Radio propagation,  Terrain feature

Modelling impact of topography gradient on signal path loss along the road way for 5G

Prediction of outdoor path loss, PL, model is crucial for the design and planning of fifth generation (5G) wireless communication systems. Different propagation models have been proposed to approximate cellular network’s coverage for diverse surroundings including for along the road way setting. In Malaysia, Road ways are not entirely on flat terrain with several segments of the roads commonly experience topography elevation. This paper presents simulation studies on the impact of topography gradient towards PL for different millimeter wave frequency bands based on available outdoor PL models. Three outdoor PL models were compared, namely close-in (CI) free space reference distance model, floating intercept model (FI), as well as alpha-beta-gamma (ABG) model. Five millimeter frequency bands at 28, 32, 38, 46 and 73 GHz with different gradients and line-of-sight (LOS) scenarios were investigated in the simulation. PL computation using the selected models indicated that topography elevation along roadways may contribute to deviation of no more than 2 dB relative to computation for flat terrain. However, selection of model used may results in different precision in PL modeling

Performance evaluation of broadband fixed wireless system based on IEEE 802.16

Fixed Wireless Access systems operating below 11 GHz have the potential to provide broadband wireless access for non line-of-sight operation. In this paper the performance of a typical broadband fixed wireless system based on the IEEE 802.16-2004 specifications is determined. A scenario for business applications with outdoor customer premises equipment is investigated in the 3.5 GHz frequency band. Different path loss models and terrain types are considered. Coverage and throughput in a sector are determined for this business scenario

Design of Cognitive Radio Database using Terrain Maps and Validated Propagation Models

Cognitive Radio (CR) encompasses a number of technologies which enable adaptive self-programing of systems at different levels to provide more effective use of the increasingly congested radio spectrum. CRs have potential to use spectrum allocated to TV services, which is not used by the primary user (TV), without causing disruptive interference to licensed users by using appropriate propagation modelling in TV White Spaces (TVWS). In this paper we address two related aspects of channel occupancy prediction for cognitive radio. Firstly, we continue to investigate the best propagation model among three propagation models (Extended-Hata, Davidson-Hata and Egli) for use in the TV band, whilst also finding the optimum terrain data resolution to use (1000, 100 or 30 m). We compare modelled results with measurements taken in randomly-selected locations around Hull UK, using the two comparison criteria of implementation time and accuracy, when used for predicting TVWS system performance. Secondly, we describe how such models can be integrated into a database-driven tool for CR channel selection within the TVWS environment by creating a flexible simulation system for creating a TVWS database

Performance of a TV white space database with different terrain resolutions and propagation models

Cognitive Radio has now become a realistic option for the solution of the spectrum scarcity problem in wireless communication. TV channels (the primary user) can be protected from secondary-user interference by accurate prediction of TV White Spaces (TVWS) by using appropriate propagation modelling. In this paper we address two related aspects of channel occupancy prediction for cognitive radio. Firstly we investigate the best combination of empirical propagation model and spatial resolution of terrain data for predicting TVWS by examining the performance of three propagation models (Extended-Hata, Davidson-Hata and Egli) in the TV band 470 to 790 MHz along with terrain data resolutions of 1000, 100 and 30 m, when compared with a comprehensive set of propagation measurements taken in randomly-selected locations around Hull, UK. Secondly we describe how such models can be integrated into a database-driven tool for cognitive radio channel selection within the TVWS environment

A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles

In recent years, there has been a dramatic increase in the use of unmanned aerial vehicles (UAVs), particularly for small UAVs, due to their affordable prices, ease of availability, and ease of operability. Existing and future applications of UAVs include remote surveillance and monitoring, relief operations, package delivery, and communication backhaul infrastructure. Additionally, UAVs are envisioned as an important component of 5G wireless technology and beyond. The unique application scenarios for UAVs necessitate accurate air-to-ground (AG) propagation channel models for designing and evaluating UAV communication links for control/non-payload as well as payload data transmissions. These AG propagation models have not been investigated in detail when compared to terrestrial propagation models. In this paper, a comprehensive survey is provided on available AG channel measurement campaigns, large and small scale fading channel models, their limitations, and future research directions for UAV communication scenarios

Performance Evaluation of IPTV over WiMAX Networks Under Different Terrain Environments

Deployment Video on Demand (VoD) over the next generation (WiMAX) has become one of the intense interest subjects in the research these days, and is expected to be the main revenue generators in the near future. In this paper, the performance of Quilty of Service of video streaming (IPTV) over fixed mobile WiMax network is investigated under different terrain environments, namely Free Space, Outdoor to Indoor and Pedestrian. OPNET is used to investigate the performance of VoD over WiMAX. Our findings analyzing different network statistics such as packet lost, path loss, delay, network throughput.Comment: arXiv admin note: substantial text overlap with arXiv:1302.1409, and substantial text overlap with other internet sources by other author

Deterministic diffraction loss modelling for novel broadband communication in rural environments

This paper presents a deterministic modelling approach to predict diffraction loss for an innovative Multi-User-Single-Antenna (MUSA) MIMO technology, proposed for rural Australian environments. In order to calculate diffraction loss, six receivers have been considered around an access point in a selected rural environment. Generated terrain profiles for six receivers are presented in this paper. Simulation results using classical diffraction models and diffraction theory are also presented by accounting the rural Australian terrain data. Results show that in an area of 900 m by 900 m surrounding the receivers, path loss due to diffraction can range between 5 dB and 35 dB. Diffraction loss maps can contribute to determine the optimal location for receivers of MUSA-MIMO systems in rural areas