# On Reliable and Efficient Data Gathering Based Routing in Underwater Wireless Sensor Networks
## 6 RE-AEDG: The Proposed Scheme  
With the help of heterogeneous nodes' deployment and a central AUV, AEDG proved its improved network performance in terms of network energy consumption and E2E delay. However, factor of reliability has not been considered much while network designing. Therefore, in this paper we propose \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Attributes** & **MNs** & **GWs** & **AUV** \\ \hline Modem & Acoustics & Acoustics & Acoustics, Radio \\ Power & Less & High & Not a constraint \\ Quantity & Larger & Smaller & One \\ Interacts with & MNs, GWs & MNs, GWs, AUV & GWs, Sink \\ Info. sensing & Yes & Yes & No \\ Device mobility & No & No & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Attributes of types of deployed nodes. Figure 3: Network architecture. RE-AEDG which is the improved version of AEDG in terms of data reliability. RE-AEDG takes the advantage of that conserved energy and better utilizes it for secured data transmission at the destination node. Underwater networks are generally harsh environments consisting of larger area networks. While considering the limited energy of nodes, data transmission in this sort of network could be challenging. Therefore, underneath is the proposed scheme for RE-AEDG that shows how nodes are deployed and grouped together to create network layers for relatively convenient data collection and transmission process. Let \(N\) denotes the set of sensor nodes; \(N=n\) whereas, deployed network nodes are fairly portioned into \(N_{U}\)_and_\(N_{L}\). For further elaboration consider a deployed node \(i\) that may belong to \(N_{U}\) or \(N_{L}\) depending upon the following conditions:  
\[i\;\epsilon \begin{cases}N_{U}&if\quad d(i)\leq\frac{1}{2}(D_{e})\\ N_{L}&if\quad d(i)>\frac{1}{2}(D_{e})\end{cases}  \tag{9}\]  
where, \(d(i)\) be the depth of considered node and \(D(e)\) be the depth of the network under examination. Furthermore, the above written equation states that a node \(i\) belongs to the set of upper nodes if its depth is lesser or equals to half of the network's depth and belongs the set of lower nodes otherwise. Right after the completion of the deployment phase, the hand shaking process begins among nodes. Nodes broadcast a control packet in their surroundings that includes its ID, residual energy and depth information. Surrounding in-range nodes of the source node receive the packet and check for eligible neighborhood criterion which is as follows:  
**Rule 2:**  
\[j\;\epsilon \begin{cases}\widehat{N_{i}}&if\quad i\;\epsilon\;N_{U}\;and\;d(i) \leq d(j)\qquad or\qquad if\quad i\;\epsilon\;N_{L}\;and\;d(i)>d(j)\end{cases}  \tag{10}\]  
This rule states that \(j\) belongs to the neighboring list of \(i\) if the following conditions are fulfilled. Stated as:  
* \(i\) belongs to the upper node's list and depth of \(i\) is less than the depth of \(j\). * \(i\) belongs to the lower node's list and depth of \(i\) is higher than the depth of \(j\). For convenient data transmission process and energy conservation, transmission range of the source node is divided into three slices such that the first slice contains source node itself and possible cooperating nodes \(\eta_{c}\), the second slice also contains possible cooperating nodes \(\eta_{c}\) (see Figure 4 whereas, the third slice contains \(\eta_{d}\) only. It is stated that neighboring node of a source node consists of possible cooperating and destination nodes \(\widehat{N_{i}}=\eta_{c}+\eta_{d}\). This rule qualifies source node to transmit data such that only eligible cooperating nodes receive and compute that packet whereas eligible destination nodes discard it immediately and thus conserves energy. In the reference of \(i\) as a source node now consider a node \(j\) that may belong to \(\eta_{c}\) or \(\eta_{d}\) depending upon the conditions written as follows:  
\[j\;\epsilon