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In this paper, we will study floorplanning in 3-D integrated circuits (3D-ICs). Although literature is abundant on 3D-IC floorplanning, none of them consider the areas and positions of signal through-silicon vias (TSVs). In previous research, signal TSVs are viewed as points during the floorplanning stage. Ignoring the areas, positions and connections of signal TSVs, previous research estimates wirelength by measuring the half-perimeter wirelength of pins in a net only. Experimental results reveal that 29.7% of nets possess signal TSVs that cannot be put into the white space within the bounding boxes of pins. Moreover, the total wirelength is underestimated by 26.8% without considering the positions of signal TSVs. The considerable error in wirelength estimation severely degrades the optimality of the floorplan result. Therefore, in this paper, we will propose a two-stage 3-D fixed-outline floorplaning algorithm. Stage one simultaneously plans hard macros and TSV-blocks for wirelength reduction. Stage two improves the wirelength by reassigning signal TSVs. Experimental results show that stage one outperforms a post-processing TSV planning algorithm in successful rate by 57%. Compared to the post-processing TSV planning algorithm, the average wirelength of our result is shorter by 22.3%. In addition, stage two further reduces the wirelength by 3.45% without any area overhead.