Cognitive radio techniques will be developed that enable rapid, wideband spectrum sensing in the presence of strong interference. Cognitive radios must detect available spectrum quickly in real time with high-probability of success, which requires extremely high dynamic range in the presence of powerful interference signals. Furthermore, future cognitive radio will operate over multiple frequency bands spread out over a wide frequency range. This compounds the challenges to the receiver design since all filtering must be capable of tuning over wide frequency ranges. Finally, the radio must agilely hop among frequency bands. The time required to detect the power in any channel is an overhead that limits the network throughput.
Most prior cognitive radio research applies digital baseband algorithms to conventional RF and analog radio circuitry, which is not designed to address the spectrum sensing application. This limits the achievable spectrum sensing bandwidth and agility and results in high power consumption for the RF, analog, and digital signal processing blocks. This work is fundamentally different in that it will customize the entire receive chain from the RF circuitry through the digital signal processing (DSP) to incorporate new techniques specifically targeted to address spectrum sensing. The techniques involve the injection of pseudonoise-modulated RF signals into the receiver to identify the blockers via correlation algorithms in the DSP as well as to calibrate and cancel the nonlinear characteristics of the receiver. We will develop and refine the proposed algorithms and demonstrate their utility in a 28-nm CMOS receiver integrated circuit.
