Variables used in this study.

This paper considers message delivery through direct communication between drones in an epidemic manner. One method of increasing communication opportunities is to enlarge the communication range. However, this approach is not always possible due to power consumption or equipment limitations. As a novel alternative to this method, we consider setting a virtually deployed road network (VDRN) for drones. By making drones move in a distributed manner along a VDRN, they pass close to each other more frequently, increasing communication opportunities. Through theoretical analysis, we clarify how much a VDRN can improve contact performance. We also investigate how much the use of a VDRN can increase travel time, since moving along such a network can cause detours. By comparing the numerical results for the above two methods of increasing communication opportunities, we examine the required duration of detours for VDRNs to achieve the same level of contact performance as enlarging the communication range.