COMMUNITY is a formal approach to software architecture. Its main characteristics are: a precise, yet intuitive mathematical semantics based on categorical diagrams; a clear separation between computation, coordination, and distribution (including mobility); and a simple state-based language, inspired by Unity, to describe behaviour. This paper discusses the applicability of this approach to locationaware systems through the modelling of the GSM handover protocol, namely the way communication with a moving cellular phone passes from one station to another. The case study was developed with the COMMUNITY Workbench, a tool that animates distributed and mobile architectural models.