# Cognitive Routing in Software-Defined Underwater Acoustic Networks
## 3 Proposed Cognitive Acoustic Software-Defined Underwater Network  
We propose a cognitive routing protocol for software-defined underwater acoustic networks. The objective of this novel routing protocol is to overcome major issues in existing underwater communications that lead to network deterioration. This work combines a cognitive capability with a routing technique in underwater networks by using SDN as a new candidate to improve network performance and communications reliability. Taking advantage of SDN, we propose that the sensor nodes within the considered network be used for various services in the same area. This means that the sensor nodes working for one application collect information from their surroundings and send the gathered data to the controller. This logically centralized controller then performs data scheduling and network management to collect information of interest for any other application in order to take full advantage of the whole network. Our aim is to find a stable route between source and destination by jointly selecting the channel and relay node in an efficient and reliable manner. A cognitive acoustic software-defined underwater network is shown in Figure 1, where a source node in the deep ocean is looking for a stable route to a destination far away from it at a different depth in the ocean. The CA-SDUN considers \(C\) different communicating nodes. A surface buoy serving as a main controller keeps global updated information on the network. The mobile AUVs (i.e., LCs) improve network reliability by sharing the burden of the single main controller. LCs move on fixed trajectories where the track is maintained by the MC. The sensor nodes, \(G\), within transmission range of the LCs' track, serve as gateways between conventional sensor nodes, \(N\), and the AUVs, and send information to all neighboring nodes as an extended beacon message. The nodes receiving \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Protocols**} & **Proposed** & **Proposed** & **Proposed** & **Routing** & **Cognitive Routing** & **Cognitive Routing** \\  & **for UAVs?** & **for UCANs?** & **for SDUN?** & **in UANs?** & **in UANs?** & **in SDUN?** \\ \hline DBR [7] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\
[8] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ VAPR [9] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\
[10] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ CARP [11] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ AURP [12] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ LASR [13] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ DVPR [14] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ GEDAR [15] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ AEDG [16] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\
[17] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ AA-RP [18] & ✓ & ✗ & ✗ & ✓ & ✗ & ✗ \\ DCC-MAC [19] & ✗ & ✓ & ✗ & ✗ & ✗ & ✗ \\ RISM [20] & ✗ & ✓ & ✗ & ✗ & ✗ & ✗ \\
[21] & ✗ & ✓ & ✗ & ✗ & ✗ & ✗ \\ OSAR [22] & ✗ & ✓ & ✗ & ✗ & ✓ & ✗ \\ SoftWater [23] & ✓ & ✗ & ✓ & ✗ & ✗ & ✗ \\
[4] & ✓ & ✗ & ✓ & ✗ & ✗ & ✗ \\ SEANet G2 [24] & ✓ & ✗ & ✓ & ✗ & ✗ & ✗ \\
[25] & ✓ & ✓ & ✓ & ✗ & ✗ & ✗ \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of related schemes. SDUN: software-defined underwater network; UAN: underwater acoustic network; UCAN: underwater cognitive acoustic network; DBR: depth-based routing; VAPR: void-aware pressure routing; CARP: channel-aware routing protocol; AURP: AUV-aided underwater routing protocol; LASR: location-aware source routing;DVRP: diagonal and vertical routing protocol; GEDAR: geographic and opportunistic routing protocol with depth adjustment-based topology control for communication recovery; AEDG: AUV-aided efficient data-gathering; AA-RP: AUV-aided routing method integrated path planning; DCC-MAC: dynamic control channel medium access control; RISM: receiver-initiated spectrum management; OSAR: orthogonal frequency division multiplexing (OFDM)-based spectrum-aware routing; AUV: autonomous underwater vehicle. the messages keep a record of these gateways in their flow tables.