# A Method for Energy Balance and Data Transmission Optimal Routing in Wireless Sensor Networks
## 1 Introduction  
Wireless sensor networks (WSNs) are widely used in industrial control [1; 2; 3], urban management, environmental monitoring and other fields [4; 5; 6]. In a wireless sensor network (WSN), a large number of sensor nodes collaboratively perceive, collect and process the information of the sensing object, and transmit the acquired information to the user terminal through wireless communication. Figure 1 shows a typical wireless sensor network. Sensor systems operating in the field are usually powered by batteries. Limited battery power limits the working hours of wireless sensor networks. Moreover, the power consumption of the nodes in the WSN is different, and some nodes exhaust energy in advance. In systems where data is required to be reliable and complete, or where as many nodes as possible are required to operate simultaneously, the node running out of energy in advance means that the system fails.  
Structural health monitoring (SHM) systems are widely adopted to monitor the behavior of structures during forced vibration testing or natural excitation (e.g., earthquakes, winds, live loading). SHM aims at providing reliable data concerning the integrity of different kind of structures, in order to permit their further operational utilization or to impose their repair or retirement [7]. The data of multiple nodes in SHM is related. It is necessary to comprehensively analyze the data of each point to get the status information of the building. For example, monitoring of dams, bridges, railways, and coal mines, wireless sensor nodes are used for real-time monitoring and security alerts. Data anomalies in any area may indicate that danger is imminent, and security is guaranteed only when all monitoring nodes are working properly. In order to ensure that any small structural health hazards canbe discovered during long-term monitoring, it is necessary to ensure that there are enough sensor nodes alive. If many nodes are exhausted, the system becomes unreliable. In a typical wireless sensor system, multiple sensors are used to repeatedly cover key locations. Redundant monitoring can increase system reliability, which means more nodes and higher maintenance costs. In the case of a certain number of nodes, it is necessary to make full use of the limited energy to improve the overall lifetime of the system and reduce the failure rate of the sensor nodes.  
In the target tracking application of wireless sensor networks, a basic problem is target coverage. That is, given a set of targets and a WSN with some sensor nodes deployed over the monitoring field, target coverage problem is defined such that all the targets are continuously monitored or covered by at least one sensor node at any time [8; 9]. When there are many nodes in the network running out of energy, the target is easily lost. To ensure that the target's motion is captured, it is necessary to have as many nodes as possible to be alive. This also requires the full use of energy to extend the overall effective working time.  
The most direct way to solve the shortage of power supply is to increase the capacity of batteries by forming batteries in parallel or in series. However, in the test, we found that the common lithium-ion batteries often have circuit break or short circuit fault. A battery pack consists of multiple batteries, and the failure of any one of the batteries will cause the failure of the battery pack, so the probability of failure of the battery pack is much higher than that of a single battery. For the system working in the field, it is inconvenient to replace batteries frequently, and the interruption of data acquisition caused by battery failure is intolerable. Balancing energy and prolonging system lifetime are hot issues in wireless sensor networks. This paper studies a scheme which can guarantee the system to work for a long time. Firstly, the energy waste problem in wireless sensor networks is analyzed, and then the principle of this scheme is given.