<div>In recent years positioning and navigation capabilities in mobile devices have become essential to the evergrowing number of position-related smart applications. Global Navigation Satellite System (GNSS) constitutes the provider for geo-localization, therefore consumer-grade, embedded GNSS receivers have become ubiquitous in mobile smart devices. Among these, smartphones play a dominant role in enabling such modern services based on position information. However, GNSS positioning shows several weaknesses in urban contexts where mobile smart devices are massively diffused. Indeed, the limited sky visibility and multipath scattering induced by buildings severely threat the quality of the final solution. Two main ingredients can enable innovative collaborative strategies capable to increase the robustness of GNSS navigation: The availability of raw GNSS measurements which have been recently disclosed in ultra-low cost smartphone chipsets and the ubiquitous connectivity provided by modern low-latency, network infrastructures allowing for near-real-time exchange of data. This work presents the architecture of a Proof Of Concept designed to demonstrate the feasibility of a GNSS-only Cooperative Positioning among networked smartphones equipped with GNSS receivers. The test campaign presented in this work assessed the feasibility of the approach over 4G/LTE network connectivity and an average accuracy improvement over the 40%.</div>