  Mobile cloud computing relieves the tension between compute-intensive mobile
applications and battery-constrained mobile devices by enabling the offloading
of computing tasks from mobiles to a remote processors. This paper considers a
mobile cloud computing scenario in which the "cloudlet" processor that provides
offloading opportunities to mobile devices is mounted on unmanned aerial
vehicles (UAVs) to enhance coverage. Focusing on a slotted communication system
with frequency division multiplexing between mobile and UAV, the joint
optimization of the number of input bits transmitted in the uplink by the
mobile to the UAV, the number of input bits processed by the cloudlet at the
UAV, and the number of output bits returned by the cloudlet to the mobile in
the downlink in each slot is carried out by means of dual decomposition under
maximum latency constraints with the aim of minimizing the mobile energy
consumption. Numerical results reveal the critical importance of an optimized
bit allocation in order to enable significant energy savings as compared to
local mobile execution for stringent latency constraints.
