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Sensor Systems for Indoor Position Computation
Published in Krzysztof W. Kolodziej, Johan Hjelm, Local Positioning Systems, 2017
Krzysztof W. Kolodziej, Johan Hjelm
Radio wave propagation is defined as the transfer of energy by electromagnetic radiation at radio frequencies (SMI, 1998). Radio propagation studies look at how radio waves travel through a given medium such as air. Radio waves encounter various outdoor objects ranging from buildings and plants, and indoor objects, such as walls and furniture. These objects obstruct radio wave propagation and affect the amount of time it takes for the wave to reach the receiver from the transmitter. In addition to the interference caused by obstructions, other factors, such as terrain, wave frequency, and velocity of the transmitter and receiver, all impact radio propagation. Since 802.11 works over the 2.4-GHz frequency, there is interference from microwaves, Bluetooth devices, cordless phones, and other similar devices. Multi-path fading, where a signal reaches the receiver through different paths, each having its own phase and amplitude, is another common problem faced by radio waves. Even environmental changes such as humidity and temperature affect the signal strength. At a fixed location, the signal strength received from an access point varies with time and its physical surroundings.
Microwave Transmission
Published in Stephen Horan, Introduction to PCM Telemetering Systems, 2017
The ionosphere influences radio propagation by causing disturbances that are functions of solar activity, time of day, frequency, and the angle at which the radio waves enter. The link designer is concerned with effects such asGroup delay or propagation delay in the carrierAngle of arrival variationsMultipath interference effectsSignal absorptionIonospheric scintillation (rapid amplitude, phase, and polarization changes)Carrier fading carrier (slow changes in amplitude)
Satellite systems
Published in Geoff Lewis, Communications Technology Handbook, 2013
Radio propagation is such that frequencies below about 30 MHz are trapped within the ionosphere by reflection and refraction, a critical frequency that varies during the 11-year sun-spot cycle and with atmospheric conditions. For this reason, only frequencies above about 100 MHz are used for space communications.
Optimal model for path loss predictions using feed-forward neural networks
Published in Cogent Engineering, 2018
Segun I. Popoola, Emmanuel Adetiba, Aderemi A. Atayero, Nasir Faruk, Carlos T. Calafate
In this study, the propagation environments are described in terms of their respective terrain profile. Table 1 presents the terrain profile characteristics of the survey routes (R1-R11). It can be seen that the average values of latitude, longitude, elevation, altitude, clutter height, and distance from the serving base station transmitter differ essentially from one route to another. Also, the corresponding mean path loss varies across the eleven routes. This occurs because the radio propagation mechanism in wireless channels depends on the terrain profile characteristics along the path of the radio wave transmission (Rappaport, 1996). Figure 2(a)–(n) show the boxplots of latitude, longitude, elevation, altitude, clutter height, and distance in the training and testing datasets, respectively. The statistical distribution of the terrain profile data, and their corresponding path loss data, further proved the differences between the routes under investigation.