# Void Avoidance Opportunistic Routing Protocol for Underwater Wireless Sensor Networks
## Appendix A  
```
1:Hop-count request procedure:
2:node (n\({}_{i}\)) has a packet to transmit
3:n\({}_{i}\) generates HCREQ message //Node n\({}_{i}\) HCREQ (IDn\({}_{i}\), sequence#)
4:n\({}_{i}\) broadcasts HCREQ
5:node n\({}_{i}\) receives the HCREQ
6:\({}_{i}\)\({}_{j}\) is not a sink
7:\({}_{j}\) updates its neighboring table
8:\({}_{j}\)\({}_{j}\)\({}_{j}\) received the HCREQ for the first time
9:\({}_{j}\) replaces its ID in the HCREQ //Node n\({}_{j}\) HCREQ (IDn\({}_{j}\), sequence#)
10:\({}_{j}\) rebroadcasts the HCREQ
11:\({}_{j}\)\({}_{j}\) ignores the HCREQ
12:\({}_{j}\)ENDIF
13:



## References

* (1) [PERSON]; [PERSON] Design of a Node for an Underwater Sensor Network. _Inter. J. Comput. Apps._**2014**, _91_, 36-39. [CrossRef]
* (2) [PERSON]; [PERSON] Parametric Comparative Analysis of Underwater Wireless Sensor Networks Routing Protocols. _Inter. J. Comput. Apps._**2015**, _116_, 29-35. [CrossRef]
* (3) [PERSON]; [PERSON]; [PERSON] Underwater acoustic sensor networks: Research challenges. _Ad. Hoc. Netw._**2005**, \(3\), 257-279. [CrossRef]
* (4) [PERSON] _Wireless Sensor Networks_; Series in communications and networking; John Wiley & Sons Ltd.: Hoboken, NJ, USA, 2010. * (5) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]. Geographic multipath routing based on geospatial division in duty-cycled underwater wireless sensor networks. _J. Netw. Comput. Apps._**2016**, _59_, 4-13. [CrossRef]
* (6) [PERSON]; [PERSON] Performance and Trade-off of Opportunistic Routing in Underwater Networks. In Proceedings of the 2012 IEEE Wireless Communications and Networking Conference (WCNC), Paris, France, 1-4 April 2012. * (7) [PERSON]; [PERSON]; [PERSON] Underwater sensor networks: Applications, advances and challenges. _Philos. Trans. R. Soc._**2012**, _370_, 158-175. [CrossRef]
* (8) [PERSON]; [PERSON] Routing Protocols in Wireless Sensor Networks: A Survey. In Proceedings of the 2012 Second International Conference on Advanced Computing & Communication Technologies, Rohtak, India, 7-8 January 2012. [CrossRef]
* (9) [PERSON]; [PERSON] A comprehensive survey of secure and energy efficient routing protocols and data collection approaches in wireless sensor networks. In Proceedings of the 2017 International Conference on Signal Processing and Communication (ICSPC), Coimbatore, India, 28-29 July 2017. * (10) [PERSON]; [PERSON]; [PERSON]; [PERSON] Survey on Routing Techniques in Underwater Wireless Sensor Networks. _J. Netw. Comput. Appl._**2011**, _34_, 1908-1927. [CrossRef]
* (11) [PERSON]; [PERSON]; [PERSON]; [PERSON] Next forwarding node selection in underwater wireless sensor networks (UWSNs): Techniques and Challenges. _Information_**2017**, \(8\), 3. [CrossRef]
* (12) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Efficient Data Gathering in 3D Linear Underwater Wireless Sensor Networks Using Sink Mobility. _Sensor_**2016**, \(3\), 404. [CrossRef] [PubMed]
* (13) [PERSON]; [PERSON] Dynamic Source Routing in Ad Hoc Wireless Networks. In _Mobile Computing_; [PERSON], [PERSON], Eds. ; Kluwer Academic Publishers: Norwell, MA, USA, 1996. * (14) [PERSON]; [PERSON]; [PERSON]; [PERSON]. Design Guidelines for Opportunistic Routing in Underwater Networks. _IEEE Commun. Mag._**2016**, _54_, 40-48. [CrossRef]
* (15) [PERSON]; [PERSON]; [PERSON]; [PERSON] EEODR: An Energy Efficient Depth-Based Opportunistic Routing Protocol for UWSNs. In Proceedings of the 2020 IEEE Canadian Conference on Electrical and Computer Engineering (CCECE), London, ON, Canada, 30 August-2 September 2020. * (16) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] VAPR: Void-aware pressure routing for underwater sensor networks. _IEEE Trans. Mob. Comput._**2013**, _12_, 895-908. [CrossRef]
* (17) [PERSON]; [PERSON]; [PERSON]; [PERSON]. Geographic and Opportunistic Routing for Underwater Sensor Networks. _IEEE Trans. Comput._**2016**, _65_, 548-561. [CrossRef]
* (18) [PERSON], [PERSON] Void handling using Geo-Opportunistic Routing in underwater wireless sensor networks. _Comput. Electr. Eng._**2017**, _64_, 365-379.