Cognitive Radio (CR) and Software Defined Radio (SDR), concepts which were mere proposals to solve the population of services over the past two decades, are now enabled by novel materials and components to offer fully reconfigurable devices. Thus, a convergence of services can be attained within a reduced, or even single RF (Radio Frequency) signal path in the device. A solid design of reconfigurable frontends, from the RF part to the digital baseband, should consider different criteria to better exploit the available spectrum. Examples of such criteria are scattering parameters and phase linearity of components at a defined carrier frequency, RF signal bandwidth, and signal quality in terms of Error Vector Magnitude and Bit Error Rate. In this chapter, a general perspective to achieve smarter air interfaces is studied and discussed by setting out strategies based on CR and SDR techniques for the implementation and integration of future reconfigurable RF-Frontends.
ETSI reconfigurable radio systems: status and future directions on software defined radio and cognitive radio standards