With the advances of telecommunications, more and more devices are connected to the Internet and getting smart. As a promising application scenario of carrier networks, vehicular communication has enabled many traffic related applications. However, the heterogeneity of wireless infrastructures and the inflexibility in protocol deployment hinder the real world application of vehicular communications. Software defined network (SDN) is promising to bridge the gaps through unified network abstraction and programmability. In this research, we propose an SDN based architecture to enable rapid network innovation for vehicular communications. Under this architecture, heterogeneous wireless devices, including vehicles and roadside units are abstracted as SDN switches with unified interface. In addition, network resources, such as bandwidth, spectrum can also be allocated and assigned by the logically centralized control plane, which provides a far more agile configuration capability. Besides, we also study several cases to highlight the advantage of the architecture, such as adaptive protocol deployment, and multiple tenants isolation. Finally, the feasibility and effectiveness of the proposed architecture and cases are validated through traffic trace based simulation.

No abstract

The microstructure, phase structure, ferroelectric, and dielectric properties of (1 -x)Bi 0.5 Na 0.5 TiO 3 -xNaNbO 3 [(1 -x)BNTxNN] ceramics conventionally sintered in the temperature range of 1080°C-1120°C were investigated as a candidate for capacitor dielectrics with wide temperature stability. Perovskite phase with no secondary impurity was observed by XRD measurement. With increasing NN content, (1 -x)BNT-xNN was found to gradually transform from ferroelectric (x = 0-0.05) to relaxor (x = 0.10-0.20) and then to paraelectric state (x = 0.25-0.35) at room temperature, indicated by P-I-E loops analysis, associated with greatly enhanced dielectric temperature stability. For the samples with x = 0.25-0.35, the temperature coefficient of capacitance (TCC) was found <11% in an ultra-wide temperature range of -60°C-400°C with moderate dielectric constant and low dielectric loss, promising for temperature stable capacitor applications.

No abstract