Low Complexity Adaptive Turbo Frequency-Domain Channel Estimation for Single-Carrier Multi-User Detection with Unknown Co-Channel Interference

Adaptive Turbo frequency-domain channel estimation is investigated for single-carrier (SC) multi-user detection in the presence of unknown co-channel interference (CCI). We propose a modified Turbo recursive least square (RLS) channel estimation algorithm which provides very close performance to Turbo RLS channel estimation, with a huge complexity reduction. It also significantly outperforms the Turbo least mean square (LMS) channel estimation in terms of performance and convergence speed, and requires a similar complexity to the LMS channel estimation in the scenario of phase shift keying (PSK) modulation. Beside, we incorporate adaptive Turbo channel estimation with low complexity block wise Turbo Space-frequency equalization and CCI suppression (TSFE-CCIS), which also operates in the frequency domain.