Ofdm System Channel Estimation Algorithm

In this essay, we investigate channel estimation technology in OFDM system. When we use differential modulation, such as DAB system, we do differential demodulation at the receiver, avoiding channel estimation. However this technology is usually adopted in the system with low data rate. Usually OFDM system adopts coherent demodulation. So when we demodulate the symbols at the receiver, we must correct the random phase offset and amplitude offset caused by frequency selective fading and sub carrier frequency offset. And we know that it can only be down only by channel estimation, or the system will be hard to achieve satisfying performance.In this dissertation, we analyze the channel attributes in wireless communication system, and various channel models. Introduce the basic principles of OFDM and his particular mechanism used to counteract frequency-selective fading. We mainly investigate the channel estimation technology in OFDM system. We analyze the LS, MMSE, their simplified algorithm-SVD algorithm, and various interpolation algorithms based on pilots. Introduce the Wiener filter algorithm base on MMSE, and time domain channel estimation algorithms. Give performance evaluation of each algorithm. The simulation results introduce that we need channel tracking to correct the offset. We also analyze the effects of ICI on the system performance. We know that we can model ICI as a Gaussian random process, so a specific method should be used in order to mitigate ICI. In the last chapter a fast fading channel is researched. Analyze the channel estimation for this channel condition, simulate and analyze its performance.