This document proposes a delay-constrained network structure with in-network data fusion to reduce delays in data aggregation for wireless sensor networks. The proposed structure organizes sensor nodes into multiple single-layered clusters of different sizes to allow clusters to communicate with the fusion center interleavedly. Simulation results show the proposed structure can reduce delays and energy consumption compared to other structures when data is partially fusible. The structure selects cluster heads based on residual energy, degree, and distance to balance energy load.