Frequency Domain Estimation of Multiple Access OFDM Channels

OFDM modulation combines the advantages of high achievable rates and relatively easy implementation. However, for proper recovery of the input, the OFDM receiver needs accurate channel information. Most algorithms proposed in literature perform channel estimation in the time domain which increases the computational complexity in multiaccess situations where the user is only interested in part of the spectrum. In this paper, we propose a frequency domain algorithm for channel estimation in OFDM. The algorithm performs eigenvalue decomposition of the channel autocorrelation matrix and approximates the channel frequency response seen by each user by the first few dominant eigenvectors. This reduces the parameter estimation space and allows estimation using a few number of pilots.