On the Convolutionally Encoded OFDM System with Symbol Time Offset

Yung-Yi WANG  

IEICE TRANSACTIONS on Communications   Vol.E95-B   No.9   pp.2931-2935
Publication Date: 2012/09/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E95.B.2931
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Transmission Systems and Transmission Equipment for Communications
per-survivor-processing,  OFDM,  Viterbi algorithm,  symbol time offset,  

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This study proposes an improved per-survivor-processing (PSP) scheme to tackle the phase error issue in the convolutionally coded OFDM systems. The proposed approach takes advantage of the trellis structure of the convolutional codes to compensate the symbol-time-offset (STO) caused phase error in frequency domain. Unlike the traditional PSP scheme which simply estimates the phase error by using a state-based horizontal process, the proposed approach develops an extra state-wise vertical process which selects the most likely phase estimate as the survival phase in each trellis stage and then accordingly align the phase of all states to this survival phase before moving to next trellis stage of the PSP scheme. With the vertical process, the resultant phase estimate is more reliable than that of the conventional PSP scheme and hence improve the accuracy in data decoding. Computer simulations confirm the validity of the proposed approach.