Abstract: The mixed integer programming-based optimization for network lifetime scheme is proposed in this paper. We present a realistic WSN lifetime optimization framework, and a complete link-layer handshaking cycle is modeled to select transmission power levels for both data and ACK packets. Log-normal shadowing path loss model is employed to take into account the effects of path losses. We utilized the developed Mixed Integer Programming (MIP) based on optimization framework to investigate the impact of data packet length on WSN lifetime. Simulation results show that the optimal data packet length is the maximum allowed length.