A Computational Cost Reduction Scheme for a Post-Distortion Type Nonlinear Distortion Compensator of OFDM Signals


IEICE TRANSACTIONS on Communications   Vol.E81-B    No.12    pp.2334-2342
Publication Date: 1998/12/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on the Latest Development of Telecommunication Research)
Category: Wireless Communication Systems
OFDM,  nonlinear distortion,  post-distortion type nonlinear distortion compensator,  maximum likelihood detection,  

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A computational cost reduction scheme for a post-distortion type nonlinear distortion compensator of OFDM signals is proposed, and compared with the conventional sub-optimum detection scheme. The proposed scheme utilizes the principle that a complex OFDM signal can be demodulated with not only both I-phase (real part) and Q-phase (imaginary part) components, but also either of them. Usually each phase of an OFDM signal exhibits different signal envelope and they are distorted differently by the nonlinearity of a power amplifier. Consequently, three output sequence patterns can be obtained at the receiver. By comparing these outputs, we can know the erroneous positions of these sequences to some extent. By the aid of this comparison, we need to evaluate only a limited number of replicas for the compensation process of the post-distortion type nonlinear distortion compensator, which results in the computational cost reduction. We have proposed four new compensation schemes based on this idea and derived their performance in terms of the bit error rate and the average number of calculations.