Mobile Ad-Hoc Networks (MANETs) are self-forming, self-healing new generation infrastructure less wireless networks. Principal behind these networks is multi hop radio relaying. MANETs are very useful at locations where networking infrastructure is not available. Major applications of these networks can be accessed at military and emergency rescue operations. MANETs may contain small or large set of network nodes; each and every node requires acting as host and the router. Due to random movements of the nodes, MANETs obtain dynamic network topologies. Routing protocols in MANETs are accountable for establishing efficient and error free communication paths between network nodes. Dynamic network topologies make routing challenging. In order to meet requirement of present day applications and to overcome from routing challenges, routing protocols in mobile ad hoc networks need to perform better in terms of certain QoS (Quality of Service) parameters such as; good throughput, sustained communication links and least delay in establishing a link. In this paper, we have discussed QoS in MANETs and analyzed the OLSR (Optimized Link State Routing), a well-known routing protocol in MANETs for possible improvements in its performance. Here, we have revised attributes of core parameters of the standard OLSR routing model in order to obtain a new OLSR design. Performances of the standard and revised OLSR models have been tested and compared under different network scenarios using network simulator-3 (NS-3). Different QoS and performance evaluating metrics such as; the throughput, packet delivery ratio, end to end delay, packet loss and normalized routing load have been considered for measuring performances of either OLSR routing models. Based on the analysis, it is concluded that the revised OLSR model has shown better performances as compared to standard OLSR routing model.

Networks which function without having any centralized fixed infrastructure or central administration are called MANETs (Mobile Ad hoc Networks). These networks are formed by small or large set of mobile nodes and communicate through the wireless links. Such Networks requires best routing protocols to establish error-free and efficient communication links. MANETs has the property of dynamically changing topology due to their mobile nodes, which move from one place to another. Overall performance of MANET routing protocols depends upon various network and protocol parameters. Mobile ad hoc networks have the characteristics of self-forming and self-healing. The routing algorithms of the routing protocols ensure selection of routes and connectivity between the mobile nodes. This paper presents analysis of three well known routing protocols of MANETs, namely; AODV (Ad hoc On Demand Distance Vector), DSDV (Destination Sequenced Distance Vector) and OLSR (Optimized Link State Routing). Analyses of these routing protocols have been carried out using NS-3 (Network Simulator-3) by varying node density and node pause time. Different performance metrics such as throughput, packet delivery ratio, end to end delay, packet loss and normalized routing load have been considered for this analysis. This analysis concludes better performance of the OLSR routing protocol.