Characterization of Software-Defined and Cognitive Radio Front-Ends for Multimode Operation
Software-defined radios (SDRs)  are now being accepted as the most probable solution for resolving the need for integration between actual and future wireless communication standards. SDRs take advantage of the processing power of modern digital processor technology to replicate the behavior of a radio circuit. Such a solution allows inexpensive, efficient interoperability between the available standards and frequency bands, because these devices can be improved, updated and their operation changed by a simple change in software algorithms.
The ultimate goal for an SDR architecture is to push the digitization closest to the antenna as much as possible, thus providing an increased adaptation and reconfigurability in the digital domain by the use of current digital signal processors (DSP, FPGA, etc.) capable of treating the incoming signals correctly. A common implementation for the SDR concept as proposed in Reference  is shown in Figure 4.1.
This SDR concept is also the basis for cognitive radio (CR) approaches  in which ...