IMS (IP Multimedia Subsystem) [1] specified originally by 3GPP to support IP multimedia services for mobile users, has become the foundation for future wireless and wireline convergence. IMS aims at allowing service providers to easily deploy rich IP-based multimedia services. However, to deploy a new IMS-based service, both the network and the terminal need to evolve to implement the associated service logic, which makes difficult for the service providers to offer new services as this requires the user equipment (UE) to evolve to be compatible with this service. In this paper, we address this compatibility issue resorting on two approaches: IMS application download and usage of HTML5/WebSocket technology.