Content Delivery Optimization for Hybrid Satellite Networks

The thesis aims to investigate a hybrid network in which a Satellite overlay cooperates with a pre-existing CDN terrestial network. A new method of popularity generation along with a hybrid placement algorithm are presented in order to optimize QoE perceived by users ans bandwidth consumption. Performance is evaluated in terms of hit ratio and time placement. The hybrid approach shows significant improvements compared to the single terrestrial or satellite network

Cache-Assisted Hybrid Satellite-Terrestrial Backhauling for 5G Cellular Networks

Fast growth of Internet content and availability of electronic devices such as smart phones and laptops has created an explosive content demand. As one of the 5G technology enablers, caching is a promising technique to off-load the network backhaul and reduce the content delivery delay. Satellite communications provides immense area coverage and high data rate, hence, it can be used for large-scale content placement in the caches. In this work, we propose using hybrid mono/multi-beam satellite-terrestrial backhaul network for off-line edge caching of cellular base stations in order to reduce the traffic of terrestrial network. The off-line caching approach is comprised of content placement and content delivery phases. The content placement phase is performed based on local and global content popularities assuming that the content popularity follows Zipf-like distribution. In addition, we propose an approach to generate local content popularities based on a reference Zipf-like distribution to keep the correlation of content popularity. Simulation results show that the hybrid satellite-terrestrial architecture considerably reduces the content placement time while sustaining the cache hit ratio quite close to the upper-bound compared to the satellite-only method

Tuning silicon nitride refractive index through radio-frequency sputtering power

Fabrication of thin-film multilayer structures by sputtering typically requires a multi-cathode deposition machine. This study proposes a simpler approach based on the radio-frequency power modulation; thin silicon nitride (SiN) thin films were prepared by radio-frequency reactive sputtering in an (Ar + N) atmosphere at room temperature. The samples were analyzed to highlight the effects of different deposition conditions on the morphological and optical properties of the films in the visible and near/mid-infrared (IR) regions. The refractive index of the films was varied from 1.5 - 2.5 (at =800 nm) by tuning the sputtering power. IR reflectance measurements indicated the absence of spurious (oxygen- or hydrogen-based) phases; atomic force microscopy and scanning electron microscopy indicated flat and homogeneous sample surfaces