Nowadays, the users' authentication is a main aspect of any security system in which network access should be completed by only accepted users. For this purpose, the EPS network uses EPS-AKA procedure to authenticate the mobile users. In this paper, we present and analyze this procedure and we propose a new solution in order to manage its weaknesses and vulnerabilities. This solution, called Improved EPS-AKA, is a combination between the simplicity of deployment, the full mutual authentication and the secured communication between all network entities. Finally, our solution is checked and validated by the AVISPA model.