# AODV-EOCW: An Energy-Optimized Combined Weighting AODV Protocol for Mobile Ad Hoc Networks
## 1 Introduction  
The biggest difference between mobile ad hoc networks (MANETs) and other networks is that MANETs have no infrastructure, and the nodes in the network may have limited resources. Due to decentralization, a characteristic of MANETs, each node is required to constantly sense surrounding nodes and maintain routing information to communicate. The limitation of resources directly limits the communication radius and energy. With the growth in the communication time, the energy of the nodes will be exhausted, and the death of nodes will also cause changes in the network topology and the overall performance of the network.  
MANET routing protocols can be categorized into table-driven methods, reactive and on-demand routing protocols, and hybrid methods.  
DSDV (destination-sequenced distance vector routing) [1] and WRP (wireless routing protocol) [2] are two typical table-driven routing protocols. The characteristic of table-driven routing protocols is that the node maintains the routing table by itself and may send partial update packets to preserve resources when a change in the network topology is identified. However, the table-driven routing protocol does not scale well with an increase in nodes in the network. Additionally, the periodic broadcasting of messages by this type of routing protocol leads to more energy consumption and a rapid decline in the lifetime of the entire network. Reactive and on-demand routing protocols, such as AODV [3, 4] and DSR (dynamic source routing) [5], do not periodically broadcast update messages.  
Thus, they have reduced overheads and consume less energy to find routes. ZRP (zone routing protocol) [6; 7] is a typical hybrid method that combines the characteristics of a priori routing and reactive routing and uses an a priori method locally to reduce the propagation range. ZRP eliminates the long-route request delays and flooding broadcast mechanism by recording only local neighborhood nodes in the table-driven discovery method. For nodes that are not in the local zone, on-demand routing protocol features are used in ZRP. However, the routing protocols presented above are not suitable for mobile and ad hoc wireless environments. Experiment results [8] indicate that networks using the AODV routing protocol have longer lifetimes than those using the other two routing protocols, which is why authors have focused on AODV.  
The main contributions of this paper are listed below:  
1. The study introduces a multimetric mechanism for AODV to solve the problems of a short lifetime and poor link communication caused by node congestion. Furthermore, the study uses the analytic hierarchy process (AHP) [9] in operations research to carry out link selection according to the metrics.
2. As for the problem of the subjectivity of AHP, the study uses the entropy weight method (EWM) [10] to constrain the objectiveness of the routing weight. Finally, the weights of the metrics are constrained by both AHP and EWM, which is why the method uses combined weighting. Additionally, considering that the combined weights may not reflect the importance of the residual energy of the node, the study introduces a method to choose different weights derived from different comparison matrices, according the level of residual energy in the node. That is why the proposed protocol is known as AODV-EOCW (AODV with Energy-Optimized Combined Weights).
3. In this study, simulation experiments were conducted to compare the routing protocols again, and the experiment results indicate that the new routing algorithm can improve the network's lifetime and reduce the average end-to-end delay.