Channel Characterization and WirelessCommunication Performance in Industrial Environments.

The demand for wireless communication systems in industry has grown in recent years. Industrial wireless communications open up a number of new possibilities for highly flexible and efficient automation solutions. However, a good part of the industry refuses to deploy wireless solutions products due to the high reliability requirements in industrial communications that are not achieved by actual wireless systems. Industrial environments have particular characteristics that differ from typical indoor environments such as office or residential environments. The metallic structure and building dimensions result in time dispersion in the received signal. Moreover, electrical motors, vehicles and repair work are sources of electromagnetic interference (EMI) that have direct implications on the performance of wireless communication links. These degradations can reduce the reliability of communications, increasing the risk of material and personal incidents. Characterizing the sources of degradations in different industrial environments and improving the performance of wireless communication systems by implementing spatial diversity and EMI mitigation techniques are the main goals of this thesis work. Industrial environments are generally considered to be environments with a significant number of metallic elements and EMI sources. However, with the penetration of wireless communication in industrial environments, we realize that not all industrial environments follow this rule of thumb. In fact, we find a wide range of industrial environments with diverse propagation characteristics and degradation sources. To improve the reliability of wireless communication systems in industrial environments, proper radio channel characterization is needed for each environment. This thesis explores a variety of industrial environments and attempts to characterize the sources of degradation by extracting representative channel parameters such as time dispersion, path loss and electromagnetic interference. The result of this characterization provides an industrial environment classification with respect to time dispersion and EMI levels, showing the diverse behavior of propagation channels in industry. The performance of wireless systems in industrial environments can be improved by introducing diversity in the received signal. This can be accomplished by exploiting the spatial diversity offered when multiple antennas are employed at the transmitter with the possibility of using one or more antennas at the receiver. For maximum diversity gain, a proper separation between the different antennas is needed. However, this separation could be a limiting factor in industrial environments with confined spaces. This thesis investigates the implication of antenna separation on system performance and discusses the benefits of spatial diversity in industrial environments with high time dispersion conditions where multiple antennas with short antenna separations can be employed. To ensure reliable wireless communication in industrial environments, all types of electromagnetic interference should be mitigated. The mitigation