Hybrid free-space optical (FSO)/radio-frequency (RF) systems have emerged as a promising solution for high-data-rate wireless backhaul. We present and analyze a switching-based transmission scheme for the hybrid FSO/RF system. Specifically, either the FSO or RF link will be active at a certain time instance, with the FSO link enjoying a higher priority. We considered both a single-threshold case and a dual-threshold case for FSO link operation. Analytical expressions have been obtained for the outage probability, average bit error rate, and ergodic capacity for the resulting system. Numerical examples are presented to compare the performance of the hybrid scheme with the FSO-only scenario.

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Cognitive radio transceiver can opportunistically access the underutilized spectrum resource of primary systems for new wireless services. With interweave cognitive implementation, secondary transmission may be interrupted by primary transmission. To facilitate the packet delay analysis of such secondary transmission, we study the extended delivery time of secondary packet transmission. In particular, we derive the exact distribution function of extended delivery time of a fixed-size secondary packet with non-work-preserving strategy, where interrupted packets must be repeated. We also analyze the effect of imperfect periodic sensing i.e. the secondary user periodically senses the spectrum for availability, with a chance of missing an available channel on a certain sensing attempt. These results complement previous work on work-preserving strategy with perfect sensing. Selected numerical and simulation results are presented for verifying the mathematical formulation.

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Airline sector runs on very high operational costs, strict protocols and complex scheduling process. One of the critical aspect influencing these factors is aircraft maintenance routing. In order to get maintenance at regular intervals as per the FAA regulations, an aircraft is required to be routed towards a feasible maintenance station. Aircraft maintenance routing is one of the major factor that influences the decisions throughout the airline operations. This paper proposes a maintenance feasible route generation technique, based on Breadth first search and Dijkstra's Algorithms. The proposed technique is able to produce the maintenance feasible routes while ensuring that the overall maintenance cost is minimized. 

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