International Journal of Wireless & Mobile Networks (IJWMN) Vol. 4, No. 1, February 2012 DOI : 10.5121/ijwmn.2012.4116 215                     Kaushik Ghosh [1] , Partha Pratim Bhattacharya [2] and Pradip K Das [3] Faculty of Engineering & Technology, Mody Institute of Technology & Science (Deemed University), Lakshmangarh, Dist. Sikar, Rajasthan – 332311, India 1 kghosh.et@mitsuniversity.ac.in, 2 ppbhattacharya.et@mitsuniversity.ac.in, 3 pkdas@ieee.org ABSTRACT Energy efficiency is a much talked about thing in the domain of geocast routing protocols for Wireless Ad Hoc and Sensor Networks (WASNs). Fermat point based protocols are capable of reducing the energy consumption of a WASN by reducing the total transmission distance in a multi hop-multi sink scenario. Presently, there are quite a handful of them but many of them have not considered the effect of changing propagation environment around the considered network while measuring the performance of the protocol. Congested environment around a WASN increases the chance of multipath propagation and it in turn introduces multipath fading. In this paper, the effects of both of these factors are considered on the performance of I-Min routing protocol designed for WASNs. KEYWORDS WASN, Geocasting, Energy efficiency, Multi path fading, Propagation environment. 1. INTRODUCTION Geocast routing protocols have become an integral part in the domain of routing for Wireless Ad Hoc and Sensor Networks (WASNs). It is well known that these kind of networks demand special attention towards energy consumption due to their inherent nature and places of their deployment. Energy is in fact a function of the inter nodal distances (d n ), where n is called path loss exponent. Quite a few protocols of said type have been proposed over the years by numerous authors but the radio models used in most of them have undermined the effect of changing propagation environment around the network while determining its energy expenditure. A hullabaloo around a WASN is sure to introduce multipath fading, which again demands some modification in the radio model proposed for a free space condition. In this paper we have considered both these parameters to find out the degree of variation on the performance of a protocol that doesn’t consider either of these two parameters. Here, the geocast routing protocol under consideration is the I-MIN protocol [1]. In [1] the radio model used considered data size and distance between the nodes as the functions of energy consumed by a node while transmitting. Energy consumed by a node while receiving was however a function of the received data volume only. Not only this, the network was assumed to be operating in a free space only (n=2), as was considered by many other protocols [2], [3], [4],