# Position-Monitoring-Based Hybrid Routing Protocol for 3D UAV-Based Networks
## 5 Conclusions  
UAV-based wireless networks require scalable routing, which is a challenging and complex task due to the 3D environment. Due to UAVs' dynamic nature, topology-based routing suffers as UAVs change their position quickly, whereas position-based routing suffers due to a lack of global routing information. In this regard, this paper proposes the Position-Monitor-based Hybrid Routing Protocol (PMHRP) for 3D UAVs. In addition, three novel methods to select the position-head coordinator under PMHRP are introduced. The three techniques are compared with well-known routing protocols in a 3D UAV network environment. Different mobility scenarios are developed with multiple connection loads to evaluate the efficiency of the proposed scheme. Our simulation analysis shows that the proposed PMHRP with centroid PHC performed better than the GEOC, GEOD, GEOMF, and AODV routing schemes. Even the static variant of the proposed PMHRP has a higher network delay than the proposed random and centroid variants of the PMHRP. The detailed results from a number of experimentations clearly justify that the proposed routing strategies out-perform in terms of delay, packet delivery ratio, throughput, and normalized routing load. The proposed protocol is intended to support UAV architectures' network coverage and enables air-base stations to connect multiple UAVs. Future research can focus on its applications in this area. For future work, the impact of each UAV's weight and size on the performance of the proposed scheme can be considered. Moreover, implementing different clustering schemes can bring more improvements. Since PHC has its drawbacks, this work may be extended to include the use of an alternative method (such as the Election Protocol) for choosing the PHC-UAV node before and during simulation.  
Conceptualization, S.U., Z.R. and M.A.K.; methodology, S.U., M.A.K. and Z.R.; software, S.U., Z.R. and K.H.M.; validation, M.A.K., Z.R. and K.H.M.; formal analysis, S.U. and M.A.K.; investigation, Z.R. and M.A.K.; resources, M.A.K., Z.R. and K.H.M.; data curation, R.A., A.M., M.A.K. and Z.R.; writing--original draft preparation, S.U., U.T. and Z.R.; writing--review and editing, S.U., A.M. and K.H.M.; visualization, S.U., U.T, R.A. and K.H.M.; supervision, Z.R. All authors have read and agreed to the published version of the manuscript.  
[PERSON] Abdulrahman University Researchers Supporting Project number (PNURSP2022R323); [PERSON] Nourah bint Abdulrahman University, Riyadh, Saudi Arabia. The studies at St. Petersburg State University of Telecommunications. prof. [PERSON] were supported by the Ministry of Science and High Education of the Russian Federation by the grant 075-12-2022-1137.  
Not applicable.  
The authors are thankful to the Chongqing Key Laboratory of Mobile Communications Technology School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, China for providing the research guidance of this study, and the authors express their gratitude to [PERSON] [PERSON] Abdulrahman University Researchers Supporting Project number (PNURSP2022R323), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.  
The authors declare no conflict of interest.