Multirate Systems in Cognitive Radio

Abstract

Recent developments in wireless communication services have led to an increase in demand for spectrum resources. Moreover, most of the existing wireless networks follow a fixed spectrum assignment policy. A recent report by Federal Communications Commission (FCC) reveals that most of the spectrum is underutilized. Cognitive radios (CR) have proven to be a solution to alleviate the problem of spectrum scarcity by utilizing different spectrum sensing techniques. The detection of spectral holes (unused spectrum) and allocating the available spectrum to secondary users are the challenges in CR. Spectrum sensing can be broadly classified into narrowband and wideband spectrum sensing. In wideband the available bandwidth has to be subdivided into multiple frequency bands. In such scenarios the multirate signal processing using filter banks becomes a possible solution for efficient and reliable spectrum detection. Filter bank-based physical layer design for CR systems was introduced to perform simultaneous spectrum sensing and transmission. The simultaneous spectrum access improves the network throughput as more spectral opportunities are utilized. Multirate filter bank techniques can reduce computational complexity and improve spectral analysis in cognitive radio applications. For fractional utilization of spectrum, the center frequency and spectral edges of the primary user can also be estimated using filter banks. In this chapter we discuss different filter banks for spectrum sensing in CR systems.