## 1 Introduction
Notably, owing to the rapid topology change in the network, geo-routing protocols require broadcasting the proactive beacon packets (hello packets) periodically or non-periodically to discover neighboring nodes and maintain the correctness of routing selection. However, a high beacon rate (i.e., frequency of beacons) means excessive beacon overhead, which will raise the packets' collisions and transmission delay in the network [14]. Beacons are very small messages; they include parameters such as the position, velocity,  
Figure 1: Examples of wireless ad hoc networks (WANETs) communication applications. and direction of mobility of the nodes. Such key information is utilized to build the routing decisions by estimating various network measures such as geographical distance, expected transmission count (ETX), defined as the neighbor link reliability, signal strength, stability, and link lifetime (link duration) [8; 15; 17; 18; 19]. In sparse networks, for example, broadcasting beacons with high transmission power is essential to expand the awareness area or communicate with distant nodes in mobile wireless environments. Nevertheless, the increase in the beacon transmission power or the frequency of beacons (beacon rate) may negatively affect the routing performance due to the limitations of the wireless link's bandwidth and network resources. Therefore, the trade-off between the beacon rate overhead and the accuracy of routing information (precision) is still an open challenge in ad hoc networks [20; 21]. On the other hand, the other challenges that affect the routing performance in MANETs are invoked in the following aspects [6; 22]:  
1. High and rapid node mobility issues have substantial effects on the efficiency of routing algorithms; thus, the mobility increases the changes in the network topology, causing connection failure and increasing the re-initiation of the route-discovery operation. 2. Medium Access Control (MAC) issues are responsible for node access to the shared medium and related to node mobility, Quality of Service (QoS), bandwidth, synchronization, hidden terminals, and exposed terminal problems. 3. Scalability refers to the capacity of the routing protocol to expand the network with a large node density without causing any disruption or failure in data transmission or traffic loading. 4. Energy consumption is another significant challenge when the devices are equipped with a limited-lifetime battery. Therefore, energy management for transferring information has to be minimized in ad hoc networks. 5. Security is a critical issue in data forwarding for randomly distributed nodes, where the data packets are more vulnerable to attacks due to the absence of centralized control. 6. Furthermore, packet collision, resource constraints, interference, and packet loss are other significant challenges that MANET routing has faced. In this study, therefore, we suggest an effective strategy to improve the performance of the most commonly used geographic-based routing protocol, called Greedy Perimeter Stateless Routing (GPSR), designed by [PERSON] and [PERSON] [23]. To do this, an adaptive beaconing strategy is proposed to mitigate the drawback of broadcasting beacons integrated with the greedy forwarding mechanism of this protocol, in addition to lessening the problem of inaccurate routing to the appropriate neighbor. In fact, traditional GPSR is an efficient routing protocol where the nodes' positions and destination addresses are used to make routing decisions based on (Beacon) hello packet data. Every node sends out hello packets (beacons) periodically at regular intervals of time. The beacons include the nodes' addresses (IDs) and positions, as well as information concerning its one-hop neighbors. However, the beaconing process in this traditional GPSR exhibits a few drawbacks that make it somehow unreliable for high-mobility nodes. Once the nodes' topologies change rapidly, the nodes may need to increase their beaconing frequency to obtain more accurate information on neighbors.