In this paper, we study the use of intra-session random linear network coding (RLNC) in wireless sensor networks. In RLNC, intermediate nodes buffer the packets received from upstream nodes. Using intra-session RLNC, intermediate nodes transmit coded packets by performing coding on the packets of various flows. The main challenge in using intra-session RLNC is to determine how many coded packets each node requires to transmit for each flow such that the sink can decode the packets of all the flows. We analytically find the time at which a node can stop transmission of packets for a particular flow without interrupting the decoding process at the sink. Using this analysis, we design a link-by-link feedback mechanism to acknowledge the packets of a particular flow. An intermediate node generates feedback packets for its upstream nodes. The upstream node stops transmission of a flow when it receives an acknowledgment for that flow. Simulation results show that the link-by-link feedback mechanism with intra-session RLNC achieves lower power consumption compared to RLNC without intra-session coding and also the CCACK algorithm .