Wireless networks that operate on batteries are imposed with energy constraints and long distance communications between nodes are not desirable. Implementing Relay Nodes (RNs) can improve network capacity and save communication energy. A two-hop relay routing scheme is considered, in which the RNs are temporarily placed and have energy constraints. This paper investigates a joint optimization problem on Relay Node Placement (RNP) and route assignment for two-tiered wireless networks. A recursive Weighted Clustering Binary Integer Programming (WCBIP) algorithm is proposed to maximize the total number of information packets received at the Base Station (BS) during the network lifetime. We first present an optimization algorithm based on Binary Integer Programming (BIP) for Relay Node Assignment (RNA) with the current node locations. Subsequently, a weighted clustering algorithm is applied to move the RNs to the best locations to best serve their respectively associated Edge Nodes (ENs). The algorithm has the complexity of O(2 ⁿ ). The simulation results show that the proposed algorithm has significantly better performance than the other two relay placement schemes. Both theoretical analysis and practical design procedures are also presented with details.