A Low Complexity Architecture for OFCDM Downlink Transmitter Using Joint Time-Frequency Spreading and IFFT

Lilin DAN  Yue XIAO  Wei NI  Shaoqian LI  

IEICE TRANSACTIONS on Communications   Vol.E92-B    No.10    pp.3071-3074
Publication Date: 2009/10/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.3071
Print ISSN: 0916-8516
Type of Manuscript: Special Section LETTER (Special Section on Advanced Information and Communication Technologies and Services in Conjunction with Main Topics of APCC/COIN 2008)
OFCDM,  MC-CDMA,  two dimensional spreading,  IFFT,  

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In this letter, a low complexity transmitter is proposed for the downlinks of orthogonal frequency code division multiplexing (OFCDM) systems. The principle is based on a joint time-frequency spreading and inverse fast Fourier transform (TFS-IFFT), which combines the frequency spreading with partial stages of IFFT, so as to simplify the real-time processing. Compared with the conventional one, the proposed OFCDM transmitter is of lower real-time computational complexity, especially for those with large spreading factor or low modulation level. Furthermore, the proposed TFS-IFFT can also be applied to other frequency spreading systems, such as MC-CDMA, for complexity reduction.