## 4 Systematic Performances Analysis of UWSNs  
### The Systematic Performance Items Analysis  
UWSNs are composed of master nodes, sensor nodes and mobile nodes, performing functions such as ocean exploration and underwater monitoring. Firstly, UWSNs can be seen as an \"extension tentacle\" of underwater detection, which requires monitoring a wide area where the sensor nodes are distributed. Secondly, to collect and process data effectively, UWSNs are required to have high data transmission capability, including lower delay, higher bandwidth and good QoS. In addition, underwater monitoring needs a long time for information collection and processing, therefore the energy of the sensor nodes must be managed effectively for longer lifetime. Moreover, because of harsh underwater environment, sensor nodes may fail or recover frequently, so the network must have a high dynamic adaptability and fault tolerance. Therefore, from a systematic view, the systematic performance of an UWSN can be divided into the following items:  
1. _Coverage._ This is the effective monitoring scope as a network system, including the precision of detection within the monitored space. The stronger the coverage, the wider the network's coverage, and any place within the range will have more nodes working simultaneously within the underwater space. 2. _Connectivity._ This includes the degree of connection and data transmission capacity provided by the network. Stronger connectivity provides more end-to-end transmission paths and higher data transmission bandwidth and reliability. 3. _Durability._ This is the run time duration of the network. Stronger durability ensures that the network can provide a longer exploration and monitoring service. 4. _Rapid-reactivity._ This refers to the capacity to recover to normal network mode when a node is added to the network, fails in the network or the network mode is switched. Stronger rapid-reactivity represents a stronger ability to cope with dynamic changes when one node is added or exits, and when there is need to change the working mode. The systematic performance of UWSNs depends not only on the physical performance parameters of the nodes, but also on the constraints of the underwater monitoring mission and the network structure. Hence, the relationship between systematic performance items and the influencing factors of UWSNs should be established. From the above analysis, the factors influencing the performance of UWSNs can be divided into three categories: constraint parameters, device performance parameters and networking parameters. The expectation performance of UWSN in the monitoring mission determines the constraint parameters, which include the UUVs' and sensor nodes' contribution rate to systematic performance items, the adjustment coefficients for different systematic performance items, and so forth. Constraint parameters only relate to the evaluation standards, but not on the actual devices and their physical performance. Therefore, once the evaluation standards are made certain, the constraint parameters are determined. The velocity of mobile nodes, the detected radius and precision of sensor nodes, etc., are the device performance parameters. The communication radii of sensor nodes and the number of working nodes will affect the network topology, and then lead to the change of network routers and data transmission capability, and such parameters are called networking parameters. The parameters and their labels are listed in Table 1.  
In Table 1, \(p_{b}\) mainly includes the communication energy consumption and the detected energy consumption. The \(k_{b}\) represents the number of different active nodes recorded by a node over a certain interval after its neighbor nodes receive the message and is regarded as the number of its neighbor nodes. This node takes the minimum of neighbor nodes as \(k_{b}\). In UWSN, \(c_{b}\) is influenced by \(d_{b}\) and \(n_{b}\), \(k_{b}\) is influenced by \(r_{b}\) and \(n_{b}\), \(p_{b}\) is determined by \(r_{b}\) and \(d_{b}\).