Behrouz Farhang-Boroujeny ] [ Development of broadband communication systems ]s of today, orthogonal frequency division multiplexing (OFDM) has been the dominant technology for broadband multicarrier com munications. However, in certain applications such as cognitive radios and uplink of multiuser multicarrier systems, where a subset of subcarriers is allocated to each user, OFDM may be an undesirable solution. In this article, we address the shortcomings of OFDM in these and other applications and show that filter bank multicarrier (FBMC) could be a more effective solution. Although FBMC methods have been studied by a number of researchers, and some even before the invention of OFDM, only recently has FBMC been seriously considered by a few standard committees. The goal of this article is to bring this upcoming trend to the attention of the signal processing and communications communities and to motivate more research in this important area.

The primary task in any cognitive radio (CR) network is to dynamically explore the radio spectrum and reliably determine portion(s) of the frequency band that may be used for the communication link(s). Accordingly, each CR node in the network has to be equipped with a spectrum analyzer. In this paper, we propose filter banks as a tool for spectrum sensing in CR systems. Various choices of filter banks are suggested and their performance are evaluated theoretically and through numerical examples. Moreover, the proposed spectrum analyzer is contrasted with the Thomson's multitaper (MT) method-a method that in the recent literature has been recognized as the best choice for spectrum sensing in CR systems. A novel derivation of the MT method that facilitates our comparisons as well as reveals an important aspect of the MT method that has been less emphasized in the recent literature is also presented.Index Terms-Radio spectrum management, spectral analysis.

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In this tutorial article, we review different multicarrier communication methods for cognitive radio (CR) systems. There, the secondary users (SUs) need to (a) dynamically and reliably determine spectral holes and (b) transmit data in these resources without interfering with other parts of the frequency band. To satisfy (a), each SU has to be equipped with a spectrum analyzer. To satisfy (b), it is widely accepted that a multicarrier modulation technique should be adopted. Moreover, to maximize efficiency, it has been recognized that the side-lobes of each subcarrier band must be minimized. Much of the attention in the present literature emphasizes on the use of conventional orthogonal frequency division multiplexing (OFDM) -exploiting the fact that the fast Fourier transform (FFT) as part of the OFDM modulator can also be used for channel sensing. Herein, we discuss the performance of OFDM and also introduce filterbanks for multicarrier communication and spectral analysis in a CR setting. Moreover, the multitaper method (MTM) has been proposed as an effective method for spectrum analysis. Our article provides an insight into the pros and cons of these technologies.

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