# A Novel Cross-Layering Power Control Mechanism for AODV +
## 2 Background  
Due to the mobility of the nodes in a MANET, the links between them can be formed and terminated very frequently. This fact demands that the network be able to self-organize and self-configure [3]. The path between source and destination can be modified suddenly, and when this happens, the network must be able to find a new route in the shortest time and all participating nodes must cooperate. To achieve such communication, a routing protocol with appropriate algorithms that consider the dynamic characteristics of the nodes is necessary [4]. Before the interest in wireless networks grew, wired networks used two main approaches for routing: Vector distance and Link status; however, these traditional algorithms are not useful in MANETs [5], since periodic updates of the network can consume a significant part of the available bandwidth, increase the contention on channels, and require each node to recharge its power supply frequently. For these drawbacks, a series of routing protocols for MANETs have been proposed, which can be classified according to how the routing information was obtained and maintained by the nodes. They can be divided into three different groups:  
* Proactive protocols: they are a variation of the link status protocols. They determine their routes to all destinations at the beginning and keep the address information updated through a periodic process of exchange of packets. This allows a great availability of addressing requests, but it generates more signaling traffic, as well as an overload of the network. Each node has an individual routing table, for example, OLSR (Optimized Link State Routing) and DSDV (Destination-Sequenced Distance-Vector Routing) [6].
* Reactive protocols: Derived from protocols by distance-vector, they act on demand [7]. A route discovery process determines the correct route only when it is required by the source node [5]. In this way, it reduces unnecessary signaling traffic. AODV [8] and DSR (Dynamic Source Routing) [9] are part of this group.
* Hybrid protocols: Combine the basic characteristics of the preceding types of protocols into one. At the beginning of the routing, the route is determined proactively, and along with the network changes, the reactive type protocols are used. An example of this type is the TORA (Temporally Ordered Routing Algorithm) protocol [10].  
This work uses the AODV protocol, defined in RFC 3561. It is a reactive protocol that considers an adaptation of the vector-distance algorithm adapted for mobile environments. It determines the route to the destination only in case a node wants to transmit a packet; in this way, signaling traffic is reduced and delivery time decreases [8]. The routes are maintained as long as is required by the source, provided there is connectivity between the nodes of the route. Each node has a routing table, one record per destination. Each record contains destination address, next hop to the destination, sequence number generated by the destination, and time of life. AODV manages two processes for its operation; first, make a route discovery, and then, work to maintain it.  
We have chosen AODV because of its great behavior, reported in other studies [11; 12].