127 publications from this institution
The utility companies and the researchers have been developing new applications and communication protocols for the Smart Grid Advanced Metering Infrastructure (AMI) network. Since the AMI network consists of thousands of smart meters, it is built as a wireless mesh network (WMN) because it requires far less cabling work, thereby lowering the infrastructure, deployment and maintenance costs. However, WMNs suffer from scalability issues as the network grows. Therefore, in this paper, we present a scalable protocol stack for the IEEE 802.11s-based AMI applications. We propose several modifications and parameter adjustments at different layers of the protocol stack. Specifically, several parameters at the MAC layer are adjusted. Furthermore, we integrate a modified Address Resolution Protocol to take advantage of Hybrid Wireless Mesh Protocol's proactive route requests/replies, which is IEEE 802.11s standards default routing protocol. Moreover, we propose five novel retransmission timeout (RTO) calculation functions for the application layer protocol, CoAP, in order to increase the reliability. We assessed the performance of the proposed protocol stack under the widely used ns-3 simulator. The simulation results have shown that the proposed stack can reliably scale to thousands of nodes.
Magnesium oxide (MgO) thin films were deposited on silicon and glass substrates by the radio frequency (RF) sputtering method. The MgO films were annealed at 400 ⁰C for 4h. The effect of working pressure on the structure and optical properties of MgO films was investigated. Structural characterization of thin films was determined using the X-ray diffraction (XRD) method. XRD results showed the presence of dominant peaks corresponding to the (200) and (220) lattice planes of MgO. However, peaks corresponding to (111), (311) and (222) lattice planes of the MgO also appeared in the films deposited at low pressure. It was determined that the average crystal size decreased as the working pressure reduced, while the deposition rate increased. SEM analysis showed that the microstructure of the nano-spherical MgO film transformed into a coarse-grained nano-pyramidal shape after annealing. The optical properties of MgO films were investigated by UV-Vis spectroscopy. Accordingly, it was determined that the absorption threshold of the films was around 310 nm wavelength and the optical band gap of the films varied between 4.07 and 4.14 eV. As a result, MgO films with high transmittance reaching an average of 95% in the visible region were obtained.