Joint Channel Estimation across Multiple Cells in Coordinated Multi-Point

Coordinated multi-point transmission (CoMP) allows to deal with interference limitation in cellular systems by acting as a distributed antenna system across cell boundaries. In order to successfully enable CoMP, accurate channel knowledge is required. In our work we are focusing on the joint reception in the uplink, using linear MMSE combining, suppressing interference. We are using LTE-Advanced signal formats together with realistic time-varying frequency-selective channel models. We investigate the performance of different channel estimators in conjunction with several types of Zadoff-Chu-based pilot sequence assignments and different operation points for interference-over thermal (IoT) and SIR. The estimators are estimating the channels either jointly or separately for all users within the coordinated cell set. We show for Zadoff-Chu sequences where users are separated by different roots, the necessity for joint estimation is much higher than in case of separation by different shifts. We also show increasing joint estimation gains for both increasing IoT and SIR.