Unmanned aerial vehicles (UAVs) have found numerous applications in wireless communication, as either aerial user or mobile access point (AP). Compared to conventional terrestrial wireless systems, UAVs' communications face new challenges due to their high altitude above the ground and great flexibility of movement, bringing several crucial issues such as how to exploit line-of-sight (LoS) dominant UAV-ground channels while mitigating resulted strong interference, meet distinct UAV communication requirements on critical control messages versus high-rate payload data, cater for the stringent constraints imposed by the size, weight, and power (SWAP) limitations of UAVs, as well as leveraging the new degree of freedom via controlling the UAV trajectory for communication performance enhancement. In this talk, we will provide an overview of the above challenges and practical issues in UAV communications, their state-of-the-art solutions (with an emphasis on promising signal processing and optimization techniques used for them), as well as important directions for future research.

The insatiable demand for media rich content and the increasing availability of advanced devices such as smart phones, tablets, etc., has forced the mobile communications eco system to consider the next generation solutions to address these needs. 5G, already in early commercial deployment, is responding to these needs with options such as Small Cells, HetNets, Carrier Aggregation, Machine-to-Machine, Internet-of-Things, Relays, Device-to-Device, massive MIMO and operation in the vast spectrum available in the millimeter wave range, among others. In this talk, I will review some of the opportunities and challenges inherent to these higher bands, and how they can be best addressed to deliver practical solutions to the challenges outlined above in 5G and beyond.