# Efficient Bloom Filter-Based Routing Protocol for Scalable Mobile Networks +
## 2 Methodology
### Functional Description  
The HRAN routing protocol comprises three distinct stages of execution: building the heat layer, searching for the hottest paths, and keeping the routes in place. Each of these stages will be discussed in further depth below.  
* Construction of the heat layer: During the heat layer's initial setup, each node proactively shares its network topology data with its neighbours. Each node maintains an N-by-1 vector of TAB filters containing all of its knowledge about the network's topology. There is a corresponding level of the heat gradient at each of these coordinates [18; 19; 20].  
The thermal layer for node D with a 6-bit filter size is seen in Figure 3. The shown HRAN configuration used a total of three gradients (N = 3). Nodes in dark grey layers suggest that their D-nodes are in warmer scale locations than nodes in light grey regions. There is no information about the location of the D node in the TAB filter vector for any nodes that do not include it.  
Each node contributes to the formation of the thermal layer by regularly broadcasting HELLO messages. Each HELLO signal has a vector of length N = 1 BFs, where the strongest colour gradient (N) is suppressed. In the HELLO message, you will find a BF that is an exact replica of the standard sender node filter, only with a temperature gradient of one to N = 1. In order to minimise data transfer during topological information propagation, regular filters are sent.  
The temperature gradient of a node is ORed with the BF sent in the HELLO message using a binary OR operation. Figure 5 illustrates that the beginning of the filter copy in the message occurs at position 2, whereas the beginning of the position in the node structure occurs at position 1. This method operates on the premise that elemental information weakens with increasing distance.  
Figure 3: Heat layer of a node.  
Route maintenance: Route maintenance is divided into three tasks: (1) Establish a hot tunnel. (2) Route is selected to transmit packets and restore direction as shown in Figure 3(a). (3) The path optimization process iteratively optimizes the path to reduce the impact of navigation and randomness in the path discovery process as shown in Figure 3(b).  
Heat tunnels are created by entering the identification into the TAB filter located at position 1 in the heat gradient of the intermediate node, a heat tunnel is produced when the packet is sent. As the TAB filters are normally updated, the \"heat\" information for unused routes is progressively lost, but this procedure maintains it current for the routes that are really being utilised. Heat travels via a tunnel from node A to node D, as shown in Figure 5(a). Again, nodes in darker grey zones have lower (warmer) gradient information about node D than nodes in lighter grey zones.  
Figure 4: Route discovery.  
Figure 5: Exchange of HELLO messages between neighboring nodes.  
Figure 6: Route discovery and respective heattunnel creation.  
The construction of heat tunnels in frequently used corridors has a dual purpose. As can be seen in Figure 6b, the primary goal is to facilitate future route searches by other nodes. The second goal is to facilitate route repairs on a local level with little communication. Figure 6c depicts the construction of a new heat tunnel after the identification of the other path.  
Route repair: When a route fails as shown in Figure 7a, repair signals (REPAIR) are repeatedly sent to different regions with increasing temperature. When the final destination is reached or no more hotspots are located, the procedure concludes. To perform repair process, a REPAIR message is sent to all nodes in broadcast node. The destination node on the hottest gradient (gradient 1) is the route that failed, the first repair area starts off as gradient 2. The repair area is progressively incremented until it reaches the N gradient. At this stage, the route is considered irrepairable and a new route discovery process is started which is demonstrated as in Figure 7b.