# An AUV-Aided Cross-Layer Mobile Data Gathering Protocol for Underwater Sensor Networks +
## 4 Description of Our Proposed Cross-Layer Mobile Data-Gathering Protocol
### AUV Discovery Phase
The simulation parameters to evaluate our model are summarized in Table 1.

The neighbor discovery phase is set to 60 s and the distributed clustering phase interval is set to 80 s while \(T_{d}\) and \(G_{t}\) are considered as 0.067 s each. The AUV discovery phase interval depends on the network dimensions, the predefined path and the AUV speed (during the discovery phase). In our simulation set-up, the AUV discovery time is 600 s. The normal operational phase is set to 7200 s. At the end of each operational phase, all phases are repeated to reschedule the sensors and increase network efficiency. Thus, the number of repetitions depends on the total simulation time and each phase interval. The energy of each phase is captured by the simulator considering the number of transmissions and receptions. The simulation time is set to 12 h while all the presented results are averaged over 50 runs for randomly generated topologies. The network lifetime is calculated by letting the simulation continues until the first sensor runs out of the energy. ### Performance Metrics

We use and define the most important metrics for the performance evaluation of our proposed cross-layer protocol. Packet Delivery Ratio (PDR) is defined as the ratio of the number of packets successfully received to the total number of packets generated across the network. Goodput is referred to the total amount of data packets successfully transmitted by sensors in the network within a given period of time (simulation time). Probability of collision is given by the following equation,

\[P_{col}=1-\prod_{i=1}^{N-1}\frac{T_{s}-i(T_{d}+G_{t})}{T_{s}}. \tag{18}\]

where \(N\) denotes the number of sensor nodes deployed in the network and \(T_{s}\) indicates the scheduling interval. \(T_{d}\) is the delivery time of each packet and \(G_{t}\) is the guard time which is used to ensure that a packet is entirely received at the destination before starting of data transmission by another sensor. In our simulation set-up, we consider both \(T_{d}\) and \(G_{t}\) as 0.067 s each. This value is exactly equal to the maximum propagation delay of a transmitted packet. Energy consumption shows the average energy consumed per packet successfully delivered. Network lifetime defines as the time when the first sensor runs out of energy. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Acoustic propagation speed & 1500 m/s \\ \hline Transmission power & 105 dB re \(\mu\) Pa \\ \hline Receiving power threshold & 10 dB re \(\mu\) Pa \\ \hline Sending power & 50 W \\ \hline Receiving power & 0.158 W \\ \hline Idle power & 0.008 W \\ \hline Transmission range & 100 m \\ \hline Packet generation rate & Every 100 s \\ \hline Bit rate & 10 kbps \\ \hline Node number & 100–500 \\ \hline Deployment region & 1000 * 1000 * 300 \\ \hline AUV speed & 4 m/s \\ \hline AUV movement depth & 250 m \\ \hline Sink coordinate & (0, 500, 0) \\ \hline Data packet size & 1024 bits \\ \hline Neighbour discovery interval & 60 s \\ \hline Distributed clustering interval & 80 s \\ \hline AUV discovery interval & 600 s \\ \hline Normal operational interval & 7200 s \\ \hline Initial energy of each node & 40,000 J \\ \hline \(T_{d}\) & 0.067 s \\ \hline \(G_{t}\) & 0.067 s \\ \hline Simulation time for each run & 12 h \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters. ### Simulation Evaluation

In this section, we first evaluate the impact of routing layer on our propose cross-layer protocol. We also assess the impact of MAC layer on the cross-layer protocol. #### 5.3.1 the Impact of Routing Layer on the Cross-Layer Protocol

The impact of the routing layer on the CLMD, CMDG, AEERP, and AUV_PN is evaluated in this section. Simulation parameters are fixed while the number of acoustic sensors varies from 100 to 500. Figures 4-6 shows the simulation results for the packet delivery ratio, energy per packet, and network lifetime, respectively.