Channel Optimized Predistortion in Self-Heterodyne Direct Conversion Architecture for OFDM Systems

Jun-Seok YANG  Jong-Ho LEE  Seong-Cheol KIM  

Publication
IEICE TRANSACTIONS on Communications   Vol.E90-B   No.6   pp.1400-1406
Publication Date: 2007/06/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.6.1400
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
Keyword: 
channel estimation,  predistortion,  self-heterodyne,  direct conversion,  OFDM,  DCT,  

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Summary: 
This paper presents a novel technique to compensate intermodulation distortion of a self-heterodyne direct conversion OFDM system in multipath propagation environments. A self-heterodyne direct conversion system has an advantage that simple receivers can be built that are completely immune to any phase noise or frequency offset. This system, however, has a disadvantage that the nonlinear square-law detector at the receiver of the self-heterodyne direct conversion system gives rise to second order intermodulation distortion. In this study, channel estimation is performed using a training sequence and then the predistortion coefficients with regard to estimated channel parameters are derived to compensate the receiver nonlinearity. Transmit power distribution is employed to overcome multipath fading channels as well. Computer simulation demonstrates that the proposed approach improves the BER performance of the self-heterodyne direct conversion OFDM system in a multipath fading channel. This scheme gives advantage to multi-carrier systems that are much more sensitive to frequency and phase error than single-carrier systems.