Channel Effect Compensation in OFDM System under Short CP Length Using Adaptive Filter in Wavelet Transform Domain

Channel estimation in communication systems is one of the most important issues that can reduce the error rate of sending and receiving information as much as possible. In this regard, estimation of OFDM-based wireless channels using known sub-carriers as pilot is of particular importance in frequency domain. In this paper, channel estimation under short cyclic prefix (CP) in OFDM system is considered. An adaptive algorithm based on the set-membership filtering algorithm is used to compensate for this problem. In short CP length, the per-tone equalization (PTEQ) structure is used to prevent inter-symbol interference (ISI). 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, utilizing the wavelet transform on the branch of this structure in each sub-carrier before applying adaptive filters will in turn increase the estimation speed. The simulation results show better performance than conventional adaptive algorithms. In addition, the estimation and compensation of the channel effect under short CP can be easily accomplished by this algorithm.

Keywords:

Channel estimation , PTEQ structure , Set-membership filtering , Short CP , Wavelet packet transform