A survey on opportunistic routing protocols in the Internet of Underwater Things

Abstract

Compared with traditional ocean monitoring technologies, such as cable seabed observation networks, the Internet of Underwater Things (IoUT) can provide real-time underwater environment monitoring and improve efficiency of data collection. Data collection is one of the most essential functions of IoUT, while it is very challenging to achieve efficient data transmission in IoUT. Opportunistic routing is considered to have great advantages and potential in mitigating the drawbacks of underwater communication and improving the performance of data transmission. Therefore, in this paper, the opportunistic routing protocols for IoUT are reviewed and summarized. Taking advantage of the broadcast characteristic of wireless underwater communication, opportunistic routing selects a group of suitable neighbors as potential forwarders instead of selecting only one or a few specific next-hop nodes as in conventional routing, thus improving the success rate of data packet delivery. Critical to routing performance is which nodes participate in data forwarding as forwarders. The nodes act as forwarders are determined by user-defined routing parameters, which are referred to as route metrics in this paper. First, route metrics of opportunistic routing are analyzed and a comprehensive classification of opportunistic routing protocols is discussed based on the route metrics. Then, opportunistic routing protocols for IoUT are further investigated and compared in terms of the adopted communication technique, data delivery ratio, transmission delay efficiency, energy efficiency, buffer efficiency, reliability, etc. Based on the comprehensive classification and comparison, existing problems and future research issues regarding opportunistic routing in IoUT are finally presented.