Extrapolation and Interpolation for Simplified Multi-User Channel Estimation Techniques in a 4G OFDM System

摘要

In this paper, we address the topic of pilot aided multi user channel estimation for a proposed 4G wireless system that uses Orthogonal Frequency Division Multiplexing (OFDM) in a synchronous SDMA environment, which can also be regarded as a Multiple Input Multiple-Output (MIMO) environment. Two estimation techniques for Time-Invariant (TI) channels that utilize extrapolation and specially designed pilot sequences are presented: the Iterative Low Complexity (ILC) and the Extrapolated Matched Filter (EMF) techniques. Unlike most multi-user channel estimation methods in the literature, the ILC and EMF methods do not assume that the number of utilized subcarriers is equal to the OFDM FFT size. Then, two channel interpolation methods are described for Time-Varying (TV) channels: Windowed DFT Interpolation and Parameterizing by TI Doppler channels. We compare our methods to current techniques for TI and TV channels. Simulation results show that performance of our methods equal that of current technologies, but the computational complexity is significantly reduced.