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In this paper, a new relay system that uses the UAV as a relay station between the tethered UAV and ground user (TU2U2G) is proposed. The TU2U2G system uses a TUAV as a viable alternative to replace BS and provide seamless service over a cable that simultaneously supplies stable power and a reliable wired data-link connection from a ground control station. Compared to the BS, TUAV improves system coverage due to its high altitude. Also, it overcomes the antenna down-tilting, which increases the path loss between BS and UAV in the cellular system. In addition, it overcomes the UAV drawback of the batteries’ limited capacity. Therefore, TUAV can achieve the main requirements of a reliable cellular BS in terms of endurance, backhaul link quality, and the advantage of the UAV’s high altitude. After that, the optimization problem is formulated to maximize UAV relay station coverage under the power budget and maximum UAV height constraints. For simplicity, the 3D placement of the UAV is decoupled to the vertical and horizontal placement. Then, a 3D placement algorithm for the system is proposed. The UAV placement in the TU2U2G system compared to the cellular system shows better results in terms of optimum UAV height, maximum coverage radius, and maximum relaying distance.

This paper develops a comprehensive simulation model for Avionics Full-duplex switched Ethernet (AFDX) network based on OPNET platform. Accordingly, the performance of AFDX networks is analyzed. The effect of frame size, switching delay and changing frames transmission order on the AFDX network performance are investigated. [t is found that using faster switches and small frame size reduces the fixed part of the end to end delay. Also, it affects the variable part of end to end delay due to changing of delay in switches' buffers and frames transmission order.

This paper presents the evolution of Aircraft Data Networks (ADN)'s. It describes various Avionics data network protocols based on the Avionics systems architecture. The paper describes the evolution from a simple point-to-point protocol presented in ARINC 429 to a shared data bus protocol presented in ARINC 629. Finally, the new Data network based on AFDX (Avionics Full-duplex Ethernet) is discussed. AFDX is a new standard based on Ethernet technology and able to handle today's requirements. A brief comparison between the three different protocols is presented. The comparison shows that AFDX provides better performance and flexibility without losing the compliance with safety, redundancy and reliability of Avionics requirements General TermsAvionics Data Buses, protocols.

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