Is Hop-by-Hop Always Better Than Store-Carry-Forward for UAV Network?

As energy supply on Unmanned Aerial Vehicle (UAV) is limited, energy efficient data transmission in UAV networks would be of great concern to the researchers. Nevertheless, UAV networks exhibit strong dynamic nature compared to ordinary Mobile Ad hoc Network (MANET), it is not rare that some nodes will be disjoint from other nodes from time to time. Under such circumstance, ordinary hop-by-hop routing schemes can not be used anymore, for there is no route existed from source to destination. Some solutions use store-carry-forward (SCF) routing to facilitate end to end data transmission. However, when should we use SCF routing, when we should use hop-by-hop routing if we taking energy into consideration? Is hop-by-hop routing always better than SCF? If it is good or not when the hop-by-hop routing is combined with the SCF routing? All these questions need to be answered. In this paper, we answered above questions by proposing three types of minimum energy consumption models of hop-by-hop routing, and two SCF routing models. We compared all these models and considered four tactics of combination modes for the transmissions in a rotary-wing UAV network. The researches show that two tactics have better performance than other modes in energy saving capabilities by reducing 70% at most with the hop-by-hop routing, and the transmission time of combination modes are in same scale compared with hop-by-hop routing. The two tactics are appropriate for different UAV networks respectively, in which the source UAV can or cannot get the GPS information of relay UAVs in the route. The research conclusion can also be used for the transmissions in a fixed-wing UAV network by modifying the energy consumption models of fixed wing UAV, which is different from rotary wing UAVs.