In this paper, a new transport layer method is proposed utilizing a diversity scheme to make an end to end communication reliable and consequently reduce power consumption in large scale sensor networks. Sensor networks are composed of large number of battery powered nodes. Energy consumption is the most important design objective in sensor networks while delay and throughput are taken less into account. Wireless transmission is the other important characteristic of these networks. Small-scale fading decreases wireless communication performance. In a fading channel higher SNRs is needed and consequently more energy is consumed. In addition to error occurred because of poor communication node-to-node links are unreliable because of the insatiability of nodes and therefore the corresponding end-to-end links are unreliable. In order to overcome the first issue which is poor communication, transport layer methods proposed. For the second problem sensor network routing protocols propose path redundancy in order to guarantee a reliable packet delivery. Path redundancy makes some copies of a packet to receive to destination. This is a type of diversity. We combine these two methods and propose Simple Transport Protocol for Wireless sensor network (STPW) which is a transport layer method to make the end to end communication reliable.