# Adaptive Thermal-Aware Routing Protocol for Wireless Body Area Network
## 1 Introduction
For collection of vital signs of patients, healthcare applications with emergence of biomedical sensor devices turned the technology into WBAN [18; 22]. WBAN is an extended form of Wireless Sensor Networks (WSN) that is implemented for specific medical purposes by incorporating various networks and wireless tools that ensure distant healthcare monitoring. Hence, the implementation of WBAN results in better quality of life through timely detection and by taking proactive measures. Due to the hustle of daily lives, many people do not prefer to stay in hospitals for continuous monitoring. Monitoring of multiple patients in a real-time environment is one of the significant applications of WBAN [23]. The fundamental objective of WBAN is to get human physiological or vital sign data (i.e., temperature, glucose level, heart rate, etc.) from patient(s) for continuous monitoring [22] that ultimately demands an efficient routing mechanism. The designing of efficient and reliable routing protocols is a challenging job for WBAN due to its distinct features and limitations including overheating and energy depletion of embedded sensor nodes. The energy consumption and heat-rise affect the stability of a network and, hence, WBAN data is transmitted through various paths. The study is aimed to improving the network lifetime and WBAN network performance through efficient routing while managing temperature rise and decreasing the energy consumption. Over the years, various WBAN routing protocols have been proposed in the literature. These protocols could be segregated into six categories, i.e., Thermal-aware routing protocols, Energy-Aware based routing protocols, QoS-aware based routing protocols, Postural-movement-based routing protocols, Cluster-based routing protocols and Cross-layered routing protocols [24]. This study focuses on the thermal-aware scheme because the prime focus of the proposed study is associated towards the introduction of novice WBAN routing protocol which is thermal-aware routing protocol. The contemporary thermal-aware routing protocols include TARA [25], LTR [26], ALTR [26], LTRT [27], HPR [28], RAIN [29], TSHR [30], M-ATTEMPT [31], TMQoS [32], RE-Attempt [33], \(M_{2}E_{2}\)[34], TLQoS [35], DRC [36], TTRP [37], TRPL [38] etc. The \"Thermal-Aware Routing Algorithm (TARA)\", is proposed to decrease the chances of temperature of the implanted bio-medical sensor in the body of a human. The TARA algorithm ensures the equal temperature diffusion between all the nodes via contemplating temperature. However there are some limitations of TARA, such as network lifetime, packet drop and reliable transmission. The Adaptive Least Temperature Routing (ALTR) protocol is presented to overcome the problem faced in TARA. In ALTR instead of discarding the packet after it exceeds the threshold value, it works as Shortest Hop Routing (SHR) to transfer the packet to the destination. However, it only considers average temperature metrics and less Network lifetime and high end-to-end delay. Several mechanisms discussed above [25; 26; 27; 28; 39; 40] have been adopted to handle the problem of temperature rise when data is transmitted among the nodes as well as a sink node in an IoT-based WBAN system. To the best of our knowledge, these techniques do not focus on the overall rise of temperature in the entire network and temperature rise in the forwarding node. The reliable and quick transmission of data consuming low-temperature rise is highly important in WBAN. This study presents a thermal-aware routing protocol for WBANs, which aims at the uniform diffusion of load among sensors nodes in term of temperature rise. The proposed thermal-aware WBAN routing protocol known as Adaptive Thermal-Aware Routing (ATAR). The ATAR addresses the problem of temperature rise and decreased data transmission while increasing network life.