Wireless ATM networks can be implemented by adding mobility support functions to fixed ATM switches. This paper first describes a possible wireless ATM network and protocol architecture relying on "modular addition" of mobility support functions. This architecture sets a broad context where future WATM research can be conducted to elaborate on its various components. Within this context, this paper presents a holistic solution for one of the most important mobility support functions: the handover protocol for intra-switch handovers.