Multicarrier communication methods such as Orthogonal Frequency Division Multiplexing (OFDM) and Filter Bank Multicarrier (FBMC) permit the implementation of dynamic spectrum access thanks to their ability to finely control signal transmission over specific frequency subbands. Therefore, multicarrier methods are strong candidates for the physical layer of spectrum sharing applications and cognitive radios. This dissertation explores methods for spectrum awareness and opportunistic access of multicarrier radios based on the allocation of subcarriers in blank spectral spaces. Following a theoretical description, a physical layer hardware design based on FPGA is presented, including the description of a working prototype with solutions to the tasks of spectrum sensing, frame detection, synchronization, channel estimation, demodulation, and mutual interference mitigation.