Heterogeneous wireless systems such as a combination of mobile broadband wireless access (MBWA) and wireless local area network (WLAN) are candidates to attain the large capacity in the next generation mobile communication systems. For capacity expansion, small cells of multIPle wireless network are deployed densely in these systems. Because a number of the cells overlap, users must discover lots of cells at once for cell selection. As a result, radio resources are much used for cell selection and cell selection errors occur in dense small cell environment. In this paper, we propose the cell selection scheme for data traffic optimization in such an environment. The proposed scheme uses positioning information and the average of signal strength for cell selection. Using positioning information, users can select the cell which has a better channel quality fast and easily. It is considered that the proposed scheme is useful to optimize data traffic offloading in the heterogeneous wireless network. We study the 50 % user throughput and the system throughput of the proposed scheme by comparing with the conventional scheme which uses measured instantaneous signal strength. The simulation results show that the proposed scheme can improve the 50 % user throughput by 68% in comparison with the conventional scheme. Also, the system throughput is enhanced by 10 % compared with the conventional scheme. These performances can be achieved by feasible positioning accuracy.