*4.1.2. Reactive routing protocol (On-demand)*

In the reactive protocols, the nodes discover the on-demand destinations, i.e. they do not require a route to the destinations where they have to send data, and seek the efficient use of resources like energy and bandwidth. Examples of reactive protocols are : AODV (Ad-Hoc On-Demand Distance Vector), DSR (Dynamic Source Routing) and TORA (Temporally Ordered Routing Algorithm). An examination of he AODV protocol, which is the representa‐ tive of the reactive protocols used for testing, follows in this chapter.

The AODV routing protocol is a reactive protocol, i.e. the route to a destination node is discovered only when it wants to send a packet (data) to this node., This protocol enables dynamic routing, where the route of the packet can be changed in accordance with the route that the data is following, if the route used is unavailable. This discovery quickly results in new destinations [20] [23].

The AODV protocol is a protocol based on the Destination-Sequenced DistanceVector (DSDV) [19], and is created primarily to eliminate errors in DSDV, on account of the constant changes of topology and the large number of control messages between the network components. During the route discovery, the AODV protocol uses a traditional routing table as a storage mechanism. This only stores one entry, i.e. it only stores the next hop to the destination, unlike the DSR that stores multiple routes to the same destination and also stores the entire route from the source to a destination. The AODV is designed to be used in ad-hoc networks which have provided small numbers of nodes (up to thousands). The main purpose of the protocol is to adapt quickly and dynamically to the changing conditions of the network links, and find routes which can allow it to provide a desirable QoS. In this way it, avoids wasting bandwidth, minimizing memory usage and processing the nodes that act as routers.

especially the quality over quantity link for users and the quality of wireless communications,

A Mobile WiMAX Mesh Network with Routing Techniques and Quality of Service Mechanisms

http://dx.doi.org/10.5772/55863

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The Simulations experiments were carried out with the aid of Network Simulator version 2 [25] to show the performance of some routing protocols with QoS as network measure in WiMAX Mesh Network. For the WiMAX Mesh simulations it was used a module developed by the Network and Distributed System Laboratory [26] with extensions to use on PMP and mesh mode. The results compare four routing protocols: AODV, OLSR, HWMP Proactive and

The simulation scenario chosen for the experiments were formed in a randomly generated with sixteen nodes, but that could easily represent a pre-existing base stations in a city, a rural area or a group of cities in proximity.The base stations act as routers through which network traffic will be routed through them choosing the best path according to its algorithms so that

The scenario (Figure 8) aims to test the choices of the best routes according to the algorithms / routing protocols and verify the flow and the delay due to these choices. The results are found

in the simulations are evaluated along with the following analysis of these.

HWMP Reactive. Figure tal show the topology used for the tests, a random topology.

while taking into account attenuation, signal quality and interference.

**5. Evaluation and results**

**Figure 8.** Simulated Topology

traffic is routed between source and destination.
