SUMMARYWiMAX-the Worldwide Interoperability for Microwave Access is a promising technology for offering high-speed data, video and multimedia services over mobile platform evolving toward all IP networks. The increasing demand of WiMAX for VoIP and high-speed multimedia is due to the simplicity of installation and cost reduction compared with the traditional wired DSL cable. The challenges to service providers lie with the Quality of Service (QoS) under varying fading environment while at the same time maximizing for resource utilization. In this paper, a rigorous and comprehensive performance study of mobile WiMAX has been made with respect to adaptive modulation and coding techniques considering the variation in the speed of the mobile, path-loss, scheduling services and application type for comparing with the fixed type of modulations. The OPNET 14.5.A modeler for WiMAX platform has been used as simulator for adaptation at the physical layer of the transmission in WiMAX OFDMA structure. Observation reveals that dynamic adaptation of modulation and coding schemes based on channel condition enables better QoS while consuming low overall bandwidth of the system.

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UAV networks are envisioned to play a crucial role in the future generations of wireless networks. The mechanical degrees of freedom in the movement of UAVs provides various advantages for tactical and civilian applications. Due to the high cost of failures in system-based tests, initial analysis and refinement of designs and algorithms for UAV applications are performed through rigorous simulations. Current trend of UAV specific simulators is mainly biased towards the mechanical properties of flying. For network-centric simulations, the intended measurements on the performance of protocols in mobile scenarios are conventionally captured from general-purpose network simulators, which are not natively equipped with comprehensive models for 3D movements of UAVs. To facilitate such simulations for UAV systems, this paper presents different mobility models for emulation of the movement of a UAV. Detailed description of three mobility models (random walk, random direction, and Gauss-Markov) are presented, and their associated movement patterns are characterized. This characterization is further extended by considering the effect of large obstacles on movement patterns of nodes following the three models. The mobility models are prepared as open-source add-ons for ns-3 network simulator.

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