Fundamental trade-offs in communication and trajectory design for UAV-enabled wireless network

The use of unmanned aerial vehicles (UAVs) as aerial communication platforms is of high practical value to future wireless systems such as 5G, especially for swift and on-demand deployment in temporary events and emergency situations. Compared to the static terrestrial base stations (BSs) in cellular networks, UAV-mounted aerial BSs possess stronger line-of-sight links with the ground users due to their high altitude as well as high and flexible mobility in 3D space, which can be exploited to enhance the communication performance. On the other hand, unlike terrestrial BSs that have reliable power supply, aerial BSs in practice have limited onboard energy, but require high propulsion power to stay airborne and support high mobility. Motivated by the above new considerations, this article aims to revisit some fundamental trade-offs in UAV-enabled communication and trajectory design. Specifically, it is shown that the communication throughput, delay, and (propulsion) energy consumption can be traded off among each other by adopting different UAV trajectory designs, which sheds new light on their existing trade-offs in terrestrial communication. The main design challenges and promising directions for future research are also discussed.