Analysis of Time and Frequency Domain Pace Algorithms for OFDM with Virtual Subcarriers
Résumé
This paper studies common linear frequency direction pilot- symbol aided channel estimation algorithms for orthogonal fre- quency division multiplexing in a UTRA long term evolution context. Three deterministic algorithms are analyzed: the max- imum likelihood (ML) approach, the noise reduction algorithm (NRA) and the robust Wiener (RW) filter. A closed form mean squared error is provided for these three algorithms. Analyti- cal and simulation results show that, in the presence of virtual subcarriers, the ML can suffer large performance degradation due to ill-conditioned matrix issues. A solution to this problem is to use the Tikhonov regularization method giving the NRA. The equivalence between the NRA and the RW is proved an- alytically. A practical implementation of the NRA and RW is proposed based on partial-input partial-output FFT, leading to 6 to 8 times lower complexity than the reference implementa- tion.
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