The promise of a truly mobile experience is to have the freedom to roam around anywhere and not be bound to a single location. However, the energy required to keep mobile devices connected to the network over extended periods of time quickly dissipates. In fact, the operational time, has been identified as the number one criteria by the majority of the consumers purchasing a mobile device. Moreover, concern about exhausting battery lifetime is also one of the main reasons why users do not opt to use advanced multimedia services on their mobiles more frequently.The perspective for the future does not look encouraging in this aspect, as one could easily expect a rise of power demand for 4G devices while the progress of battery technology is very slow. Therefore, without any new approaches for energy saving, 4G mobile users will relentlessly be searching for power outlets rather than network access, and becoming once again bound to a single location. In addition, high power dissipation means that the temperature of the small handheld devices would rise to unpleasant values for the user, and make active cooling necessary.To avoid the foreseen 4G "energy trap" C2POWER project will investigate, develop and demonstrate how cognition and cooperative strategies can be extended to decrease the overall energy consumption of mobile devices while still enabling the required performance in terms of QoS. In particular, C2POWER will investigate two complementary techniques to increase power efficiency at the wireless interface of handsets:•Cooperative power saving strategies between neighbouring nodes using low power short range communications;•Cognitive handover mechanisms to select the Radio Access Technology which has the lowest energy demand in heterogeneous environments.As a consequence C2POWER should have impact on emerging standardization groups and will provide sufficient evidence on the technology and economics viability and its deployment.