Channel Estimation and CFO Compensation in OFDM System Using Adaptive Filters in Wavelet Transform Domain

Abstarct In this paper, combination of channel, receiver frequency-dependent IQ imbalance and carrier frequency offset estimation under short cyclic prefix (CP) length are considered in OFDM system. An adaptive algorithm based on the set-membership filtering (SMF) algorithm is used to compensate for these impairments. In short CP length, per-tone equalization (PTEQ) structure is used to avoid inter-symbol interference. Due to CFO impairment and IQ imbalance in the receiver, we will expand the PTEQ structure to a two-branch structure. This structure has high computational complexity, so using the set-membership filtering idea with variable step size while reducing the average computation of the system can also increase the convergence speed of the estimates. On the other hand, applying wavelet transform on each branch of this structure before applying adaptive filters will increase the estimation speed. The proposed algorithm will be named SMF-WP-NLMS-PTEQ. The results of the simulations show better performance than the usual adaptive algorithms. In addition, estimation and compensation of channel effects, receiver IQ imbalance and carrier frequency offset under short CP can be easily accomplished by this algorithm.