# Research on Multi-Strategy Routing Protocol in Flying Ad Hoc Networks
## 4 Forwarding Strategy Design
### Reactive Mechanism Design Based on Joint Measurement Optimization
According to Equation (6), there will be a relatively stable link between the next-hop node selected by greedy forwarding and the current node. The node's load is low, and the remaining energy is also relatively sufficient, so it can ensure the reliability of packet transmission, reduce the delay of intermediate forwarding, and eliminate the nodes with low power consumption to achieve a multi-objective joint optimization. The specific algorithm is as follows:

### Design of Projection Face Forwarding Strategy Based on Multi-Path

When greedy forwarding encounters a local minimum, and no available reactive path needs to be re-routed, the RGF protocol will use projection face as a temporary forwarding strategy to transmit the received packets during reactive path establishment. Because projection face forwarding only needs to use the information within the local scope, it will not bring additional overhead, and it is relatively flat or has node density in the network. When it is high, projection face forwarding can show a better performance. However, in the FANET, because of the strong mobility of nodes, the rapid change in topology, and the low density of nodes, the direct use of traditional projection face forwarding based on a single path will still bring higher path expansion and increase the delay of packet delivery. Therefore, the RGF protocol improves the traditional projection face forwarding in three aspects to improve its performance. #### 4.3.1 Selection of Projection Nodes

In the projection face forwarding of the RGF protocol, only the 3 DRNG or 3 DGG neighbor node of the current forwarding node is used for projection. That is to say, the network topology is simplified by constructing a 3 DRNG graph or 3 DGG graph. Then, the one-hop neighbor node after topology simplification is projected vertically onto the projection plane so that a local clear projection face can be obtained after projection, and there is no cross. Since the next-hop forwarding node must be selected from the 3 DRNG or 3 DGG neighbor nodes, the forwarding rules can still be executed normally. #### 4.3.2 Construction and Forwarding of Multi-Projection Plane

To improve the projection face forwarding out of the routing hole, the projection face forwarding of the RGF protocol adopts a multi-path strategy: constructing multiple projection planes simultaneously and transmitting a corresponding copy of the data packet on different projection planes. As shown in Figure 10, the minimum local node needs to encapsulate its current location in the local minimum location field of the packet header and then broadcast the packet to all its 3 DRNG or 3 DGG neighbor nodes. These nodes construct the corresponding projection plane according to their position, the position of the destination node, and the position of the local minimum value recorded in the packet header, save the information of the plane in the projection face parameter field of the packet header, and then forward the received copy of the packet on the projection plane. Because of the projection of multiple planes, and the same group of nodes in different projection planes, the next-hop node selected may be different, so the occurrence of the loop can be avoided to some extent. Because multiple copies of packets are transmitted at the same time, the probability of packets jumping out of the routing hole can be increased, and the path expansion can be reduced. #### 4.3.3 Direction-Adaptive Forwarding Rules

The projection face of the RGF protocol adopts a rule called direction-adaptive forwarding (DAF). The DAF rule enables the node \(n_{3}\) in Figure 11 to rotate the link with the node \(m\) in a clockwise direction so that the forwarding node of the next hop is \(n_{4}\), while the node selection \(n_{1}\) remains unchanged. The DAF rule combines the right-hand rule and left-hand rule.