Channel Estimation in the Presence of Timing Offsets for MC-CDMA Uplink Transmissions with Combined Equalization

In this paper we consider the uplink of a multi-carrier code-division multiple-access (MC-CDMA) system employing combined equalization and we address the problem of channel estimation in the presence of residual timing offsets. In particular, we propose a method based on the maximum-likelihood (ML) principle that jointly estimates the pre-equalized channel response and timing offset of each user. The resulting scheme operates in the frequency-domain and exploits some training blocks (carrying known symbols) placed at the beginning of the uplink time-slot. Numerical results are given to highlight the effectiveness of the proposed method and to make comparisons with other existing solutions.