# Temperature State Awareness-Based Energy-Saving Routing Protocol for Wireless Body Area Network
## 2 Related Work  
In the past decade, many scholars have proposed corresponding routing protocols for WBANs to solve the problems of energy consumption and hot nodes. In improving energy efficiency, energy-saving routing protocols use multi-hop transmission to reduce energy consumption. [PERSON] et al. [13] proposed a routing protocol (SIMPLE) to improve throughput and energy efficiency, which considered parameters such as the remaining node energy and the distance to sink, used the cost function constructed by these parameters to select the forwarding node in the path to transmit data, and finally reduced the energy consumption of the network. The iM-SIMPLE protocol proposed by [PERSON] et al. [14] is an extension of SIMPLE. The protocol also uses the cost function to select forwarding nodes, but the difference between iM-SIMPLE and SIMPLE is that iM-SIMPLE takes into account the dynamic characteristics of the WBAN, and the mobility of nodes may lead to reduced throughput and high path loss. Therefore, iM-SIMPLE attributed the problem of minimizing energy consumption and maximizing throughput to an integer linear program for analysis, and finally, the protocol extended the network lifetime and increased throughput. The sentence was amended to read:  
[PERSON] et al [15] proposed an energy-aware link efficient routing protocol (ELR-W), which integrates the residual energy of the node, link efficiency, distance to the coordinator, and number of hops in order to construct a path cost model. Using the path cost model to select the appropriate forwarding node to forward data, this protocol can effectively extend the lifetime of the network, but it is not suitable for different types of data transmission and multiple QoS requirements. In controlling the formation of hot nodes [16], the thermal-sensing routing protocol aims to minimize the temperature rise in sensor nodes, the methods of sensing node temperature and setting temperature thresholds are often used to control the generation of hot nodes. TARA [17], proposed by [PERSON] et al., is the first heat-aware routing protocol. The protocol mainly focuses on research on the temperature rise in sensors implanted in the human body. TARA uses the specific absorption rate (SAR) to calculate the temperature rise in the node and selects the lowest temperature node to transmit data during the transmission process. If a node receives data with a temperature above a threshold, it does not forward the data to the next hop node, but returns the data to the previous node. Using this backoff hot node strategy can effectively control the generation of hot nodes in the network. The hot spot prevention routing (HPR) proposed by [PERSON] et al. [18] also solves the problem of data transmission delay. The protocol adopts the shortest route method and selects the next hop node to transmit data in the shortest path according to the temperature (equal to or less than the threshold). [PERSON] et al. [19] proposed a multi-criteriadecision-making enhanced mobility and temperature-aware routing protocol. The protocol uses Analytic Hierarchy Process (AHP) to logically determine the weights of parameters such as temperature, link quality, and number of hops; based on these parameter values and their weights, a simple weighting method is used to compute the cost of each node value, and the node with the smallest cost value is selected as the best oriented node to transmit data. The protocol uses the storage and carrying mechanism of mobile nodes to effectively reduce the number of hot nodes, but this mechanism will increase the end-to-end delay. The temperature rise in the nodes in the network will not only consume a lot of energy but also cause damage to human tissues when the temperature is too high. Therefore, some scholars have optimized the design of routes related to energy saving and controlling the formation of hot nodes, so that network performance can be fully utilized [20; 21; 22; 23; 24].