## 7 Conclusions and Future Work  
_In situ_ pervasive environmental monitoring for wildfires has important advantages, but the relatively high area cost may limit its use. We have shown in this paper several domain-specific platform optimizations that reduce the cost and increase its economic viability. Sensor node hardware and a communication protocol optimized for application requirements can exceed 10 years of life time using a small, low-cost primary cell. Long node life significantly reduces the cost of the scheduled maintenance of the network, which can be important for large networks. The nodes and the communication protocol also speed up field deployment. The deployment procedure prevents most human errors, significantly reducing the cost, especially for networks with a large number of nodes. Field experiment preparation and unfolding highlighted several aspects that can improve the cost and reliability of the network components, their deployment, operation and maintenance. Long-term direct node exposure to climatic conditions increases the failure probability. Additionally, large networks are more likely to experience node failures. As we have seen during the field experiment, failed nodes may adversely affect network operation or strain the resources of the gateways in range, increasing maintenance cost. Thus, it is important to increase node and network robustness during design, production testing, functional and self-test specifications and run-time monitoring. As we have shown, node hardware design and production testing were not adequate for the field experiment and led to several node failures. Accumulation of mechanical stress should be reduced by design and during production, since it compounds, e.g., with the stress from daily and seasonal temperature variations or unforeseen mechanical interaction with wild animals. Manual soldering should be avoided, since it can inadvertently create strains in solder joints in the interaction with component leads. Faulty nodes should be detected as soon as possible to reduce production costs, e.g., by running specific self-test programs at the end of the production line. Lithium primary batteries have shelf lives in excess of 10 years. Compared to ambient energy harvesting techniques suitable for open nature, primary cells can reduce node cost, increase reliability and reduce node deployment complexity. These cells can supply very low power nodes cost effectively and maintenance free for more than 10 years, a life time suitable for many WSN applications. Brown-out detectors may consume too much energy and should not be needed for long lifetime nodes with soldered batteries. However, it is important to reset the nodes right after the battery is soldered to avoid leaving them in abnormal states that may excessively drain the battery. Sensor node functions and a communication protocol carefully tailored to the application requirements can bring important cost reductions. For instance, transmit-only nodes in star topologies can reduce the protocol stack and relax the accuracy requirements for on-node timing. In turn, these reduce microcontroller resources and energy consumption, significantly lowering the cost of components, battery and node maintenance. However, without a receiver, the nodes cannot create mesh topologies to improve network robustness and to reduce transmit power. Thus, the cost and benefits of such optimizations should be evaluated in the context of the specific application or application class. Periodic node self-testing and automatic error recovery increase the reliability and the QoS of the monitoring platform, reducing maintenance requirements and cost. In case of critical failures (e.g., failingcontact with the NTC), the nodes may disable themselves after reporting the fault to avoid reporting false events or impairing the operation of the network or the gateway nodes, as we have witnessed during the field experiment. Small sensor node physical dimensions and protection from environmental conditions may reduce the RF efficiency in several ways.