Mobile Ad-hoc Network (MANET) consists of self-organizing, self-configuring low power mobile devices. Due to mobility link failures and route failures take place in the wireless network. So, Routing is one of the not easy tasks in MANETs. Link failures and route failures depends on Hello Interval Time (HIT). Optimization of HIT minimizes the link failures and route failures. As per IETF draft, de-facto value of HIT is not suitable for real time environment. Therefore, HIT place a vital role in energy consumption of LAR protocol in MANETs. Energy consumption is one of the challenging tasks in MANETs and it mainly effects on the lifetime of the network. An effort is made to fine tune configuration parameter HIT of LAR protocol by using Fuzzy Logic. In this paper, we proposed a Fuzzy Based inference system for analyzing the performance of LAR routing protocol (FBPSLAR) by varying network size in MANETs. The performance is evaluated by using different QoS metrics such as throughput, end-to-end delay and total energy consumption etc. Our simulation results show that total energy consumption is reduced by FBPSLAR in small, medium and large networks in comparison with PSLAR. The Total energy consumption reduced by 27.16% in small network, 38.23% in medium network and 35.13% in large network.

Keywords : MANET, Routing protocols, LAR, Fuzzy Logic, FBPSLAR.