# Bat Optimized Link State Routing Protocol for Energy-Aware Mobile Ad-Hoc Networks
## 3 Research Methods and Materials
### Optimized Link State Routing (OLSR)  
The OLSR is proposed by [PERSON] et al. [37] as a proactive routing protocol for ad hoc networks and is built based on the link-state (LS) protocol with reduced signaling packets and control traffic flooding [37]. Accordingly, the OLSR protocol broadcasts messages transmitted in the network by using MPRs, nodes that are specifically designed to broadcast only such messages [38; 31]. The mechanisms of the OLSR protocol and MPR selection are shown in Figures 2 and 3, respectively.  
The OLSR protocol functions in a fully distributed manner and does not rely on any kind of central entity. When transmitting control messages, this protocol does not require reliable transmission because the messages are occasionally transmitted and are exemplified by the sequence number which rearranges them. The OLSR is also known to support node mobility. As mentioned earlier, MPRs aim to reduce the duplicity in the retransmission within the same area [39]. Every node existing within the network selects a certain group of nodes in their neighborhood and marks them as the MPRs, thereby retransmitting the broadcast packets [40]. Therefore, the neighbors of the nodes, which do not exist in the MPR set, can read and process the data packets obtained from the specified node but cannot retransmit them [41].  
The MPR set is selected by one-hop neighbors that are characterized by bidirectional links [37]. For this process, the neighboring nodes with direct links must be identified by every node. All the links must be examined in both directions to validate these nodes. In this regard, a period broadcast of the hello message, which contains data about the neighbors and their link statuses, must be created in every node. Through these messages, every node can obtain information about their neighbors until two hops and to subsequently select the MPR set. A node starts constructing the MPR selector table, a 1-hop neighbor table, and the 2-hop neighbor table as soon as it obtains a hello message [37; 38; 39].  
Figure 3: The mechanism of the Optimized Link State Routing (OLSR) routing process.  
Figure 2: Flooding mechanism with/without Multipoint Relay (MPR) [39]. (**a**) Flooding a packet in a wireless multi-hop network; (**b**) flooding a packet in a wireless multi-hop network from using MPRs (marker in black).  
A different hello message will not further be transmitted to the entire network. This phenomenon indicates that various nodes that receive the messages do not transmit them [40]. A periodic broadcast of specified control messages known as Topology Control (TC) is performed by every node to build and maintain the data for a network topology that is needed for data packet routing. The TCs are forwarded by general broadcast data packets within the entire network [39]. Data obtained by the TC packets are then stored in an appropriate topology table. Every node maintains its routing table that helps the former to route the data packets to other destinations in a network. The TC messages received by the nodes are analyzed, and parts of these connected pairs are stored in a form (last hop and node), in which the node denotes the addresses that are detected in a TC message list [36]. The routing table is created from this database by following the linked pairs in descending order.  
A group of connected pairs must be detected until the last hop node present in the source neighbor set is reached to discover an optimal route from the source to the destination [40]. The connected pairs, which are present on a minimal power usage route, are selected by the different forwarding nodes. If the bidirectional link is changed in the topology table or in the neighborhood, then the routing table must be recalculated [41].