Positioning is a crucial technology for ubiquitous computing. A directional propagation model - the Ellipse Propagation Model (EPM) is proposed by our research group for locating a mobile station (MS) within a radio cellular network with an accuracy that can enable a number of location based services to realize ubiquitous computing. By using a Geometric Algorithm, the location of the mobile station can be estimated. However, since one parameter in our Geometric Algorithm is fixed, errors may be induced as the surrounding environment changes. In view of this, we would like to propose a new algorithm - the Iterative Algorithm to provide the positioning based on EPM. With the technical support of two local mobile phone operators, we have conducted a series of experiments using real data and experiment results showed that the proposed Iterative Algorithm outperforms the Geometric Algorithm by a good margin of 18% in terms of average error.