# An Efficient Opportunistic Routing Based on Prediction for Nautical Wireless Ad Hoc Networks
## 2 Related Work  
In OppNets, there is no direct route between the source node and destination node, since nodes are moving randomly at any time. Packets are transferred by intermediate nodes adopted by the \"store-carry-forward\" (SCF) mechanism. In SCF routing, a carrier node buffers the information until the carrier node has a chance to forward the information, and it must be able to buffer the information for a considerable time period, since there may not be an immediately available opportunity for the current carrier node to forward the information [3]. Currently, opportunistic networks are mainly applied in various fields such as wildlife tracking [4], disaster rescue [5] and vehicle-mounted monitoring networks [6]. The maritime opportunistic network introduces the opportunistic network into the marine environment. It has characteristics of both the opportunistic network and the marine environment [7]. In the maritime opportunistic network, vessels are regarded as mobile networking nodes, and packet transmission is dependent on the opportunistic contacts between vessels. Some schemes previously adopted in opportunistic networks are as follows. In [8], to control the high overhead caused by unnecessary message transmission or redundant duplication, the authors proposed a message delivery algorithm for opportunistic networks that consists of two routing strategies: cooperative forwarding and store-carry-forward (SCF) forwarding. In the algorithm, communication nodes proactively detect and exploit possible contact opportunities to cooperatively forward messages. When information has never been cooperatively forwarded, SCF forwarding to control the resulting large number of messages is reactive. The adaptive switching of the two routing strategies solves the problem of message duplication. However, it leads to long delivery latency, specifically for messages that remain undelivered. Considering the dynamic mobility and the characteristics of non-cooperative forwarding of nodes, the authors in [9] studied the influence of social selfish nodes on routing and forwarding. The proposed algorithm takes advantage of the social connection, historical encounter information and cache management to facilitate cooperative forwarding of messages between nodes and ensures the integrity of multimedia communication in partitioned opportunistic networks with social selfish nodes. The results showed that reliable transmission and effective routing communication of intermittently connected opportunistic networks was achieved, compared to other schemes. However, this method ignores the impact of environmental factors on the social relationships between nodes. A novel opportunistic routing scheme based weight prediction that determines the routing decision of the relay nodes using a forwarding metric was proposed for unpredictable maritime wireless networks in [10]. The proposed method handles the high transmission overhead by collecting the latest-neighbor routing values between nodes and reducing the resource consumption when keeping these messages. The method achieved higher packet delivery ratios and efficiency compared to other routing schemes. In [11], the authors proposed an efficient routing algorithm based on node attributes for partitioned opportunistic networks in oceans that exploits the impact of node behaviors on encountering opportunities and the prediction of further relaying nodes. The results improved network performance compared to other schemes. However, the probability related to whether further relay nodes can be used for packet relaying is unknown and should be studied. In [12], a reliable topology control was proposed, based on an opportunistic routing scheme that takes the message delivery ratio between a carrier node and its candidate relay set into account. In order to improve routing efficiency, the study introduced multi-metric considerations into the variable topologies.