## 4 Simulation and Analysis  
As illustrated in the previous section, the proposed framework is not a concrete routing approach, but rather a framework used to enhance existing routing approaches. Therefore, to assess the performance of the proposed framework, three existing routing approaches are selected, and each routing approach belongs to one of the three categories described in Section 2. Specifically, the selected routing approaches are gossiping [11] (a flat routing approach), LEACH-revised (a hierarchical routing approach) and GEAR [26] (a location-based routing approach). The reason for choosing the three routing approaches is that they are classical and easy to implement. Certainly, other routing approaches can also be employed in our simulation, but using the three classical approaches is sufficient to demonstrate the effectiveness of the proposed framework. Another of our future studies will take other more complex routing approaches into simulation. The three selected approaches are described in detail as follows.  
1. Gossiping: In gossiping, a sensor node sends the packet to a randomly selected neighbour, which picks another random neighbour to forward the packet to, and so on, until the expiry time of the packet or the destination is reached, whichever comes first.
2. LEACH-revised: LEACH [19] randomly selects a pre-determined number of sensor nodes as cluster heads and rotates this role to evenly distribute the energy load among the sensors in the network. The role rotation is depicted as below. A sensor node chooses a random number, \(r\), between zero and one. If this random number is less than a threshold value, \(T(n)\), the node becomes a cluster head for the current round. The threshold value is calculated based on an equation that incorporates the desired percentage, \(p\), to become a cluster head in the current round and the set of nodes that have not been selected as a cluster head in the last \(\frac{1}{p}\) rounds. Then, all elected cluster heads broadcast an advertisement message to the rest of the nodes in the network that they are the new cluster heads. The problem with LEACH, however, is that it assumes that the cluster heads can directly send packets to the sink node, which is infeasible in large-scale WSNs. Thus, we introduce [PERSON] _et al._'s multi-hop routing algorithm [PERSON] et al. (2015) used by cluster heads to transfer packets to the sink node. [PERSON] _et al._'s algorithm is based on the cost of each wireless link, which is evaluated by using the remaining power of each node.
3. GEAR: There are two phases in GEAR. First, forwarding packets toward the target region: upon receiving a packet, a node relays the packet to the neighbour which is closer to the target region than itself. If there is more than one neighbour, the nearest neighbour to the target region is selected. However, if all of the neighbours are further from the destination region than the node itself, one of the neighbours is picked based on their evaluated cost to the destination region. Second, forwarding packets within the region: if the packet has arrived at the target region, it is diffused in the region by either recursive geographic forwarding or restricted flooding, until the packet reaches the sink node.