## 4 Comparative Discussion
### Major Features
When the hop count of the packet received by a node exceeds this threshold, the packet is forwarded to the destination node using the shortest hop algorithm. By means of these mechanisms, LTR and ALTR achieves a better performance than TARA in terms of packet delivery delay and average temperature rise in the network. In addition, while LTR still introduces packet drop, due to the packet discarding mechanism, ALTR achieves a comparable performance with SHR in terms of the percentage of packet drop during the simulation. Another disadvantage of LTR and ALTR is that there is no guarantee that during the transmission from sender to destination, the packet will always be transmitted toward the direction of the destination node. A packet may be sent to a wrong direction away from the destination node, because LTR and ALTR only are concerned about the nodes' temperature. Moreover, in ALTR, the packets might be transmitted through the hotspots after exceeding MAX HOPS ADAPTIVE, which will result in temperature rise. These disadvantages are trying to be mitigated by the next protocol, LTRT. Looking at the end-to-end connection perspective, LTRT transmits the packet through the path or route with the lowest temperature level. Therefore, the packet will be always transmitted toward the destination node, not sending the packet back to the previous node. Using this algorithm, LTRT achieves a lower average temperature rise and lower packet delay compared to LTR and ALTR. Nevertheless, the average temperature rise metric that is used by LTR, ALTR and LTRT is not appropriate for WBSNs applications. The reason is that the average temperature rise does not reflect the individual node's temperature. The average temperature level may appear to be low, while, actually, there are nodes that already exceed the safe temperature level. These nodes that are already above the safe temperature level are hazardous for human health. Therefore, the metric maximum temperature rise, which is used by TARA, is more appropriate to be used in WBSNs, because it shows the maximum temperature rise that exists in the network. The HPR protocol provides a better approach in dealing with temperature rise in the network. It considers the maximum temperature rise as the metric, not average temperature rise, and also, it uses a dynamic threshold based on the node's own temperature and its neighbors. HPR achieves a better performance compared to TARA and SHR in terms of maximum temperature rise, average delay and packet drop, especially in a high packet arrival rate environment. Unlike TARA, which tries to withdraw the packet back to the previous node, HPR tries to bypass the hotspot nodes by sending the packet to the coolest next hop node. The TSHR protocol made some modifications on the HPR protocol. Besides the dynamic threshold that is used by HPR, TSHR added one more temperature threshold, called a fixed threshold, which is applied to every node before it transmits the packet. This threshold defines the maximum temperature allowed for a node to participate in the routing process. Different from HPR, in TSHR, there is no packet discarding mechanism. If the next hop node is a hotspot, the packet will be buffered, until the temperature drops below threshold. While this provides a low packet drop rate, it suffers from higher network delay compared to HPR. As for the last protocol, the RAIN protocol offers a unique characteristic. In contrast with the previous protocols, RAIN does not use global ID for each node; it uses the local ID instead, which is generated randomly. This approach is developed to deal with the possibility of and ID-less network deployment in the future. This is a clear advantage of RAIN compared to the other protocols.