Comparison of ML carrier estimation schemes based on APSSB and preamble for OFDMA in fading channel

The paper proposes a novel estimation scheme of carrier frequency offset (CFO) based on Added Preamble Sequence Semi-Blind (APSSB) scheme. The proposed maximum-likelihood (ML) CFO estimator is based on APSSB OFDMA model in which Gold sequence is added to the output of IFFT modulator and exploited for CFO estimation at the receiver. CFO estimators based on APSSB scheme and preamble are compared by both SINR analysis and simulation. We propose that the APPSB scheme should be employed for fine frequency synchronization in OFDMA especially in delay-insensitive service. In this paper, we propose the APSSB OFDMA model in which APSSB sequence is added to the output of IFFT modulator. The APSSB sequence is exploited for CFO estimation by correlation detection with the local APSSB sequence at the receiver. Comparison of SINR is made between CFO estimation schemes based on APSSB and preamble. The APSSB scheme suffers no data rate loss, and is more accurate than preamble scheme when APSSB symbol number for CFO estimation is large enough to excess the threshold. Compared with preamble scheme, the APPSB scheme has the property of better accuracy as well as larger delay. We propose the APPSB scheme should be employed for fine frequency synchronization in delay-insensitive service. The rest sections of the paper are organized as follows. In Section 2, the proposed APSSB OFDMA system model is described. Based on this model, section 3 presents the ML CFO estimation scheme based on APSSB. A comparison is made in section 4 in terms of SINR of the two schemes in fading channel. Simulation and analysis are presented in section 5. Finally, section 6 concludes the paper.