## 3 Proposed Fires Monitoring and Detection Framework
### The Proposed Sensor Deployment Scheme
The proposed inter-cluster protocol consists of three phases: (1) initialization phase, (2) non-fire phase, and (3) fire threat phase. In the initialization phase, cluster heads first determine the paths to the sink station. After that, a message forwarding time is recorded in a schedule table by using these paths. The table provides the time when each cluster head sends its data to the upstream cluster head. It is possible that in a given time, multiple cluster heads transmit their data to their upstream cluster head. In this way, we have concurrency in the network to carry data towards the sink station, which can reduce the overall collection time. After the initialization phase completes, the network enters a non-fire phase. In the non-fire phase, the cluster head receives data from its common node and the other cluster head and forwards the data to the upstream cluster head on the way to the sink station. However, when a cluster head receives a warming message from one of its common nodes, it will go to the fire threat phase. In the fire threat phase, the cluster head tries to deliver this warming message to the sink station as soon as possible. If the cluster head is the node that first detects the fires occurring, it will inform all the cluster heads about the fire threat by network-wide broadcasting. ## 4 Simulation Setting and Results Analysis

### Simulation Model

In this study, a simulation of a wireless sensor network for forest fire monitoring and detection was carried out using modified ns-2 (version 2.31). For performance evaluation, we measured the energy consumption and fire reaction delay affected by our proposed framework from three perspectives: the proposed sensor deployment scheme, the proposed clustered hierarchy network architecture, and the proposed intra-cluster and inter-cluster protocols. Additionally, there are two main modifications that have been made in ns-2.31: fire-sim-lib and ctrl-center are added to ns-2.31. The function of fire-sim-lib is to use and process the output of a fire simulation library called FireLib [32] in our simulation. FireLib is an open source and it is used to estimate and model the spread behavior of forest fires. Our added fire-sim-lib processes the output data of FireLib to certain information which only contains ignition time and location. Additionally, fire-sim-lib is used to calculate the temperature information by using another two parameters: initial temperature of fires and temperature increment with a fixed time interval. In this way, the temperature value of each area in our scenario is dependent on time. Ctrl-center is used to manage the sensor nodes and exchangeable messages. Its basic role is to distribute some necessary messages or values between each component. Table 2 gives the network parameters that were used to configure the wireless sensor node and network topology in ns-2. In all simulations, a many-to-one traffic pattern was used, and the simulation topology consists of 121 sensor nodes which are randomly distributed and follow Gaussian distribution, and the value of standard variation is set to 1. The network and topology parameters are summarized in Figure 1.