Low Complexity FFT Schemes for Multicarrier Demodulation in OFDMA Systems

Youngok KIM  Jaekwon KIM  

IEICE TRANSACTIONS on Communications   Vol.E90-B   No.11   pp.3290-3293
Publication Date: 2007/11/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.11.3290
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
OFDM,  FFT,  multicarrier demodulation,  

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In OFDMA systems, various subcarrier allocation (SA) algorithms have been developed and adopted to realize the low-cost implementation or the optimized usage of resources, such as bandwidth and total transmit power, at the cost of increased complexity. Regardless of SA algorithms, however, it is computationally inefficient for a user who uses only a small number of subcarriers to use a full fast Fourier transform (FFT) for multicarrier demodulation at a conventional receiver in a downlink environment. In response, this letter proposes a novel low complexity FFT scheme that demodulates a set of desired multicarriers with smaller-size FFTs is proposed for computationally efficient and/or low hardware-cost receiver in OFDMA systems. Furthermore, a decision rule for the optimum size of FFT in the known transform decomposition methods is provided.