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Multi-Aware Cluster Head Maintenance for Mobile Ad Hoc Networks with Power Consumption Constraints



1. Introduction:
Mobile Ad Hoc Network (MANET) is a self-configuring infrastructure-less network of mobile devices that communicate over a wireless links. The network nodes have the ability of free movement around but each node has to act as a router in order to keep the network operating. MANETs can be used in military scenarios, rescue operations, conferences, any application that needs mobility and areas where it is hard to build a wired network.

MANETs have many design and implementation challenges like the frequent change of network’s topology, the limited bandwidth and the limited battery power resources. Since the power efficiency is a key point in MANET that enables it to operate as long as it can, we adopt the merging of Wireless Power Transfer (WPT) technique in such a network.

WPT is the transmission of electrical energy from a power source to an electrical load without a conductive physical connection. Wireless transmission is useful in cases where interconnecting wires are inconvenient, hazardous, or impossible.

2. Cluster-Based Routing:
Routing is the problem of delivering a packet from a source to a destination (Unicast) or destinations (Multicast) even when this destination is multi-hop away from the source. In order to achieve scalability, hierarchical solutions were adopted. One possible solution is to use the ideas of clustering as a hierarchical routing approach. The main idea is to group the nearby nodes into logical groups known as clusters, then assigning nodes different functionalities inside and outside a group (cluster).

Each group contains a special node that acts as a leader based on some criteria (ex. Highest ID, Lowest ID, Connectivity, Power Level, Randomly, etc.) to label the cluster and to communicate to other nodes on behalf of the cluster. Other terms used to express the leader are: cluster head (CH), coordinator, core member of dominating set, and backbone network.

Electing the cluster heads and maintaining them throughout the progress of the ad hoc networks are vital and critical functions. In cluster-based routing protocols, cluster heads consume more power than other nodes because they have special roles. Therefore, it is useful to consider the power consumption metric in the process of cluster head election and maintain it through the network life time. Not all the nodes will participate in the cluster head election, the decision of participating or not will depend on the initial node's battery power value.

3. Wireless Power Transfer:
Wireless power transfer was established with the pioneering work on electromagnetism by the 19th century physicists, who showed that an alternating current produces a magnetic field and vice versa. Nikola Tesla made a significant and well ahead of the time contributions to wireless power transfer in the late 19th century and at the early 20th century. He has demonstrated a successful WPT system that powered electronic devices.

WPT systems employ no direct electrical connection between the transmitter (power source) and receiver (load). ). An electric transformer, operating under the principle of inductive coupling, is the simplest, most efficient and prevalent form of WPT system.

The efficiency of an inductive coupling decreases exponentially with an increase in distance between the transmitter and the receiver coils due to high wastage of transmitted power through radiation. A resonant inductive coupling, where both the transmitter and the receiver coils resonate at the same frequency, is an improvement over the inductive coupling. The improvement comes from the fact that two same-frequency resonant objects tend to couple and exchange power efficiently while interacting weakly with other off-resonant sources.

4. Problem Statement:
As stated before node's resources are limited and valuable in MANETs, most importantly is the battery power. Our aim is to find an appropriate approach that will reduce the value of consumed battery power for the cluster heads. In this work we try to merge and take advantages of two technologies Mobile Ad Hoc Networks (MANETs) and Wireless Power Transfer (WPT). The goal is to build a kind of wireless communication network that is: self-organized, stable, scalable to high number of nodes, power-efficient and extended life time.

5. Proposed Solution:
We have proposed a multi-aware cluster head maintenance approach that will involve in: cluster head election, clusters formation, cluster head re-election and wireless power transfer to cluster heads. The following factors will be considered: the ideal number of nodes that a cluster can handle (Load Balancing Consideration), the distance between the node and its neighbors (Geographical Consideration), the speed of nodes (Mobility Consideration) and the node's battery power (Energy Consideration).

The OPNET software used to create the new routing protocol named Multi-Aware Cluster Head Maintenance (MACHM)and simulate it is behaviour for different scenarios.