# A _uv_-Cellular Network: Design, Implementation and Experiments
## 3 Design of _uw_-Cellular Network
### Protocol Design
#### 3.3.3 Routing Layer Protocol Design  
We design a method called CLA to aware the communication link status by analyzing the characteristics of the underwater acoustic channel. And ultimately select a relatively reliable route to deliver the information and help improve the success rate of communication between two nodes. **Related Parameters:** As mentioned earlier, underwater acoustic communication is affected by several important characteristics, and we will use the following characteristics to evaluate the state of the underwater acoustic communication channel. * _SNR (Signal-to-Noise Ratio):_ In this work, we consider the _SNR_ together with the communication interval. In a given time period, greater weighting comes from more communications, higher \(SNR\) and shorter communication intervals. We set the parameter \(m\) to the maximum number of historical values used to calculate the average, and parameter \(a\) to the number of successful communications between two nodes in time \(T\) which is the maximum length of time that can be retraced before current communication requests. \(t_{i}\) is used to represent the \(i^{th}\) interval between two adjacent communications. The weight of the _SNR_ can be calculated as \[SNR_{w}=\left\{ \begin{array}{ll}m\times\sum_{i=1}^{m-1}\frac{SNR_{i}}{t_{i} }&a\geq m\\ a\times\sum_{i=1}^{a-1}\frac{SNR_{i}}{t_{i}}&a<m\end{array} \right.\] (1)
* _Distance:_ The propagation attenuation and absorption attenuation, which is a function of communication range \(d\) and signal frequency \(f\), can be expressed as [38] \[A(d,f)=d^{n}\times(10^{\frac{a(f)}{10}})^{d}\] (2) In a given application scenario, the frequency of the communication signal is fixed and the attenuation is only related to the communication distance. As the communication distance increases, the attenuation becomes greater and the possibility of successful communication decreases. Therefore, in this work, the weight of distance can be described as \[D_{w}=\frac{1}  
ing its suitability. This means that the node with more power remaining is more likely to be selected as a forwarding node. In particular, when the power level of a node is below a preset threshold, it is no longer selected as a forwarding node in order to guarantee the smooth operation of the other functions of the node. We set that \(p_{current}\) is the current power of the candidate node, \(p_{total}\) is the battery full charge capacity and \(p_{THR}\) is the preset threshold. The weight of power can be described as \[P_{w}=\left\{ \begin{aligned} & 100\%\times\frac{p_{current}}{P_{total}}& p_{current} \geq p_{THR}\\ & 0& p_{current}<p_{THR}\end{aligned} \right.\] (4)
* _Number of hops_: The number of times a packet is forwarded between the source and destination nodes, which is the number of hops, has a significant impact on the entire underwater network system. On the one hand, more forwarding times means a higher probability of packet loss. On the other hand, the fewer times a packet is forwarded between the source and destination nodes, the less system energy is consumed. We need to consider the number of hops for each possible path from the source to the destination node. And the fewer the number of hops, the more weight will be given to. **Estimation Function:** In the real environment, the underwater acoustic channel is time-varying and the UWSNs can be considered as the uncertain system. The prediction of whether two nodes will be able to communicate successfully requires a combination of parameters. In this paper, we use _Estimated Score_ (\(\gamma\)) as the result of the communication link awareness. A high score for a communication link means that the link has a high transmission success rate, while the opposite means that the communication link is in a poor state and does not easily communicate successfully. As we mentioned above, the \(\gamma\) can be influenced by the \(SNR_{w}\), distance between nodes \(D_{w}\), energy \(P_{w}\) and number of forwarding times \(n\).