Cosine Modulated and Offset QAM Filter Bank Multicarrier Techniques: A Continuous-Time Prospect
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Research Article Cosine Modulated and Offset QAM Filter Bank Multicarrier Techniques: A Continuous-Time Prospect Behrouz Farhang-Boroujeny and Chung Him (George) Yuen ECE Department, University of Utah, UT 84112, USA Correspondence should be addressed to Behrouz Farhang-Boroujeny, [email protected] Received 11 May 2009; Revised 23 September 2009; Accepted 14 December 2009 Academic Editor: Pierre Siohan Copyright © 2010 B. Farhang-Boroujeny and C. H. (George) Yuen. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Prior to the discovery of the celebrated orthogonal frequency division multiplexing (OFDM), multicarrier techniques that use analog filter banks were introduced in the 1960s. Moreover, advancements in the design of perfect reconstruction filter banks have led to a number developments in the design of prototype digital filters and polyphase structures for efficient implementations of the filter bank multicarrier (FBMC) systems. The main thrust of this paper is to present a tutorial review of the classical works on FBMC systems and show that some of the more recent developments are, in fact, reinventions of multicarrier techniques that have been developed prior of the era of OFDM. We also review the recent novel developments in the design of FBMC systems that are tuned to cope with fast fading wireless channels.
1. Introduction Orthogonal frequency division multiplexing (OFDM) is the most dominant technology that has been researched and has been deployed for broadband wireless communications. OFDM is attractive because of a number of advantages that it offers. First, orthogonality of subcarrier channels allows trivial equalization; one scalar gain per subcarrier. Second, closely spaced orthogonal subcarriers partition the available bandwidth into a collection of narrow subbands. Adaptive modulation schemes are then applied to sub-bands to maximize bandwidth efficiency/transmission rate. Third, the very special structure of OFDM symbols simplifies the tasks of carrier and symbol synchronizations. These points are well understood and documented in the literature [1, 2]. More recent works propose extending the use of OFDM to multiple access applications. Multiple access OFDM, or orthogonal frequency division multiple access (OFDMA), has recently been proposed in a number of standards and proprietary waveforms (e.g., [3]). Some particular forms of OFDMA have also been proposed for cognitive radio systems [4]. In OFDMA, a subset of the subcarriers is allocated to each user node in a network. These users signals must be
synchronized at the receiver input to prevent intercarrier interference. OFDMA works well in the network downlink of a base station, since all of the subcarriers are transmitted from the same base station and, thus, can easily be synchronized. However, synchronization is not trivial in the network uplink where a number of nodes are tran
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