Performance Analysis of OLSR and QoS Constraint OLSR in MANET

Recent developments in the field of wireless networks lead to the development of short-lived networks known as Mobile Ad hoc Networks (MANET). The Routing protocols in MANET are classified into three categories viz. table driven, on-demand and hybrid protocols. OLSR is one example of table driven routing protocol, which is best suited for dense networks which aims at reducing routing overhead. It uses link state routing as its basis and minimum hop count as a metric to find shortest paths. But in dense networks, there may exists number of different paths to reach a destination with different cost metrics therefore some quality of service (QoS) constraints can help to choose better route to a destination. QoS guarantee is very much essential for successful communication of nodes in the network. The different QoS metrics includes throughput, packet loss, jitter, delay, error rate etc. Basic OLSR protocol has certain drawbacks like number of retransmissions, route instability, packet losses, delay etc. In basic OLSR and Qos constraint OLSR, the metric used for calculating shortest path is different. In OLSR, QoS constraint is hop count where as in OLSR-ETX, its expected transmission count which is sum of inverse of probability of successful transmission. In OLSR-ML, QoS constraint is the product of probability of successful Transmission along the path by calculating packet delivery ratios and in OLSR-MD, metric used for QoS consideration is delay. In this paper, OLSR and its Qos Constraint (OLSR-MD, OLSR-ML, OLSR-ETX) are analyzed in terms of various parameters viz. Throughput, Normalized Routing Load, End-to-end delay. These parameters have been simulated on NS-2 simulator and compared by varying the simulation time.