Channel Estimation in OFDM System over Wireless Channels

In this paper, we investigate channel estimation techniques for wireless receivers. Channel estimation is important for wireless applications because a wireless channel has fading characteristics and time varying impulse response. OFDM is a multi-carrier modulation technique wherein we use a set of orthogonal sub-carriers. OFDM divides the entire frequency band into several sub bands. The sub-carriers that are sent with known power are called as pilots. Estimation is based on pilot arrangement. In this paper, we analyze the channel estimation techniques such as LS, MMSE at pilot frequencies for different modulation techniques. A simplified Kalman filter is given which reduces the noise effects of the LS estimation. Also the estimation error in the existing methods is investigated. Here the performance of the techniques is based on the bit error rate and complexity.