# Design of Multi-Modal Ship Mobile Ad Hoc Network under the Guidance of an Autonomous Ship
## 5 Analysis of Node Transmission Capacity  
Modern wireless communication systems basically include the comprehensive application of two basic theories. One is the Frills Free Space Propagation Model mentioned above, and the other is Shannon Formula. According to Shannon Formula, as follow Formula (19), the maximum information transmission rate \(C\) (bit/s) of a specific channel:  
\[C=B\text{log}_{2}\bigg{(}1+\frac{S}{N}\bigg{)} \tag{18}\]  
Figure 8: Link calculation in leaving scenario.  
where \(B(\mathrm{Hz})\) is the channel bandwidth, \(S(\mathrm{W})\) is the average power of the signal transmitted in the channel, and \(N(\mathrm{W})\) is the Gaussian noise power within the channel (unit: W).  
Generally, the maximum amount of information that a channel can reliably transmit per unit of time is also called channel capacity. According to Formula (19), we can see that the channel capacity is proportional to the bandwidth and is affected by the signal-to-noise ratio. From the perspective of wireless communication technology, and shipborne communication equipment, our ship MANET is a complex system that can be transmitted and received at multiple points. This means that the signal transmitted by one node is noise interference to some other receiving points. An increase in noise signal power means a decrease in channel capacity. Other transmission nodes will increase their transmission power to ensure their own channel capacity. Therefore, if this situation is not limited, all nodes will be submerged by noise and the system will be crashed. Therefore, the selection of signal transmission distance, power, and channel of each node is the result of a balance of various factors.  
In this chapter, we test the connectivity of ship MANET through the parameters such as node coverage distance, channel capacity, and transmission power. Combined with the construction of ship MANET, it needs to be changed. As mentioned above, each node is both a transmission node and a receiving node. First of all, in a continuous communication process, such as the communication task of a collision avoidance maneuvering in the network, multiple ships in the network will receive and transmit signals many times during this period, but only the signals of their interaction objects are useful to them, and the rest can be defined as interference for the time being. Therefore, in addition to noise, signal interference is the accumulation of signal interference of non-interactive objects. Secondly, according to the Frills Formula mentioned above, the attenuation of the signal is related to the distance, so we can use the Formula (19) to express the capacity of a node:  
\[C=B*\log_{2}\left(1+\frac{\frac{P_{t}}{d_{r}^{2}}}{N_{0}+\sum_{i=0}^{k}\frac{P_ {t}}{d_{r}^{2}}}\right) \tag{19}\]  
where, \(P_{t}\) is the transmission power of the node, \(d_{r}\) is the distance from the transmission node to the destination node, \(N_{0}\) is noise, \(P_{t}\) is the power of the signal transmitted by the unexpected node of the target node, \(d_{i}\) is the distance from them to this node. Using formula 19, we perform the analysis of node transmission capacity, including calculation of capacity of nodes at different values of power, calculation of the capacity of nodes for fixed capacity, and calculation of capacity of nodes for different values of capacity.