The Software Defined Radio (SDR) paradigm aims at replacing most of analog functions of radio transceivers by digital processing blocks. This approach enables to tend to more flexible and reconfigurable terminals. But up to now, actual SDR systems are mostly applicable for basestations or access points, while it’s still problematic to implement small form factor solutions for mobile terminals.The INRIA Socrate team aims at addressing the challenges of SDR in practical devices, considering technical issues from the viewpoint of flexible radio front-ends, agile resource allocation and efficient programming of such devices.This presentation will focus on the main challenges of designing an SDR system depending on the application scenario and the kind of wireless standards available in the environment. These techniques, currently developed for classical long range wireless systems, could find some new constraints in the field of RFID, from the reader side for example.