Performance evaluation of ETX metric on OLSR in heterogeneous networks

In mobile ad hoc networks, each node behaves like a router and is responsible to deliver data and control traffic to the other nodes by using specific routing protocol. However, nodes in these networks can arbitrarily move with various speeds and possibly cause the frequent link breaks. Furthermore, they are wireless nodes and inherently have limited bandwidth compared to the wired networks which usually results in the network congestion. These situations lead to more number of packet drop and ineffectiveness in data delivery. Hence, the specific ad hoc routing protocols are required to improve the quality of data transmission by selecting the high throughput path for forwarding traffic. This routing process can be achieved by using one or more effective routing metrics. Expected Transmission Count (ETX) is one of these metrics introduced to improve throughput in ad hoc networks by incorporating the link loss ratio. This loss can be possibly caused by buffer overflow in network congestion situation, link break in highly dynamic topology or unidirectional link in heterogeneous networks. In this work, various simulation scenarios are constructed to study the effect of ETX metric in load- and speed-varying conditions in heterogeneous networks.