This paper shows how to implement mobility functions within the ATM switching system for ATM mobile services. It is possible for the current fixed network to be evolved into an integrated service and an integrated network as the mobile mobility functions are added within the ATM network. Our target is to develop an ATM mobile switching controller. We propose a new basic functional model and a mapping of this model onto the physical entities. This paper also presents the modular signaling protocol stack and signaling procedures for the separation of call and control. Finally, we describe our project's state of development. We mainly investigate the mobile call and connection function within the ATM mobile switching controller: an air interface is not considered in this paper.