An Enhanced Channel Estimation Technique with Adaptive Cyclic Prefix Length for LTE Downlink Systems

In this paper, we propose a channel estimation algorithm robust to the channel length effect with an adaptive cyclic prefix technique for LTE Downlink systems. As LTE Downlink system is based on a MIMO-OFDMA technology, a Cyclic Prefix (CP) is inserted at the beginning of each transmitted OFDM in order to mitigate both inter-carrier interference (ICI) and inter-symbol interference (ISI) caused by the multi-path propagation. Usually, the length of the inserted CP is defined to be equal to or longer than the channel length. However, and due to some unforeseen channel behavior, the CP can be shorter than the channel length. Therefore, we have proposed a hybrid channel estimation technique able to resist to the length effect. However, the proposed algorithm suffers from the presence of ISI. Therefore, in this paper, we propose a hybrid channel estimation technique with an Adaptive Cyclic Prefix Length (ACPL) in order to enhance the performance of the system. MATLAB Monte-Carlo simulations are used to evaluate the performance of the proposed estimator in terms of Bit Error Rate (BER) for 2x2 LTE Downlink system.