As most application modes of ubiquitous learning need support of Intranet servers or Internet connections and using handheld devices as movable terminal. However, not all learning environments have sufficient information and communication technology (ICT) infrastructure and the equipments needed might be too expensive. These factors result some learning activities hard to be supported by ICT and also reduce learners¡¦ motivations on using ICT for ubiquitous learning in daily life. This research proposed the concept, architecture, and operational logic of GroupNet to construct a more flexible ubiquitous learning environment. GroupNet is aiming to support small-group face-to-face learning activities anywhere and anytime without sticking in traditional classroom settings and additional infrastructures. The GroupNet architecture consists of four different layers including Network, GroupNet Kernel, GroupNet application and GroupNet application user interface. GroupNet is based on a peer-to-peer wireless ad hoc network and coordinated by GroupNet Kernel which is able to embed in various kinds of mobile devices. GroupNet Kernel consists of connection controller, message manager, online status manager, file sharing manager, and activity controller; these five components serve as the core for supporting upper layer GroupNet applications. We have also implemented the application programming interface (API) for accessing the core functions supported by GroupNet Kernel such that developers can develop GroupNet applications with fewer efforts. A GroupNet application has been developed using the APIs for conducting an experiment on how to reduce groupthink phenomenon using mobile devices in collaborative learning to evaluate the feasibility of GroupNet Kernel and illustrate the effectiveness of GroupNet applications.