M.Sc.

Abstract: Large antennas, such as required for radio astronomy or interplanetary probes, or ground stations of satellites, are engineering structures subject to gravity, wind, and thermal strains. The conditions especially the temperature gradient can cause undesired shape deformation, twists, and strain concentration in the structure, which can adversely affect the performance of antenna systems for both pointing and accuracy. In this thesis the thermal effects on the electrical characteristics of the reflector parabolic antenna are studied.

Abstract: Routers are intelligent devices that make connection between different networks possible. In addition, routers can perform several functions, including filtration and selection of the best path of packets movement. Routers must be configured efficiently in order to perform the above functions. In literature, two approaches have been distinguished for the configuration, namely; text mode and graphical mode approach. The present work is analyzing these two approaches and defines precisely their advantages and limitations.

Abstract: The orthogonal frequency division multiple access (OFDMA) scheme adopts orthogonal frequency division multiplexing (OFDM) subcarriers, which are particularly suited for transmition over broadband frequency selection channels, to support multiusers. The scheme considered usually assigns a subset of subcarriers to each user and adopted adaptive techniques for the allocation of available resources/subcarriers according to the channel state information (CSI) estimated at the transmitter using a reverse link.