Near-Optimal Pilot Design for Multi-User Channel Estimation in Comb-Like Systems

Due to the aliasing, traditional comb like periodic pilot patterns don't allow to increase the number of estimated users' channels without strong degradation of channel estimation quality. Irregular sampling allows to overcome these limitation and reduce the number of pilot subcarriers used by one user, but it has one problem. Methods of finding irregular sampling for one user often can't be applied to multi-user case. If we send pilots of several users on the same subcarrier we will deal with multi-user interference. We propose deterministic multi-user pilot pattern and sequence design. We compared our design with traditional comb-like solutions with several times less users per one OFDM symbol or one comb-like pilot subcarriers arrangement. It shows better or slightly worse result in the comparison with them.