An Agile Digital Radio System for UHF White Spaces

In recent years, we have experienced an impressive spread of mobile communications as well as the emergence of new communication protocols. This lead to an overutilization of some spectrum bands, while the utilization of other bands is sometimes minimal or insignificant. The exploration of the white spaces concept, which represents the unused portions of the spectrum, mainly due to the shutdown of analog TV transmissions, has arisen as a solution for spectrum reuse. Currently, the electromagnetic spectrum is statically allocated, associating each technology to a particular frequency band, which leads to an inefficient use of the spectrum. Thus, it would be advantageous to change the way the electromagnetic spectrum is accessed, adopting a dynamic access paradigm-dynamic spectrum access (DSA). However, for this to be possible, in addition to regulatory changes, it is necessary that the radio physical layer becomes flexible and adaptable, enabling the efficient configuration of various parameters such as transmit frequency and power, modulation, and bandwidth, among others. The well-known concepts or paradigms of software defined radio (SDR) and cognitive radio (CR) are precisely the key to meeting these requirements. Based on these concepts, it will be possible to build a smart, adaptable, efficient, self-aware, and self-learning radio that could easily implement the DSA paradigm [1].