Multi-User Channel Estimation in a 4G OFDM System

In this paper, we address the topic of pilot aided multi-user channel estimation for a proposed 4G wireless system that uses OFDM in a synchronous SDMA environment, which can also be regarded as a Multiple-Input Multiple-Output (MIMO) environment. An Iterative Low Complexity (ILC) estimation technique for Time-Invariant (TI) channels that utilizes extrapolation and specially designed pilot sequences is presented. Unlike most multi-user channel estimation methods in the literature, the ILC method does not assume that the number of utilized subcarriers is equal to the OFDM FFT size. Then, a channel interpolation method is described for Time-Varying (TV) channels: Windowed DFT Interpolation. Simulation results show that performance of our methods equal that of current technologies, but the computational complexity is significantly reduced.