Multi-Stage Channel Estimation across Multiple Cells in Uplink Joint Reception

The interference limitation of cellular systems can be addressed by coordinated multi-point (CoMP) transmission and reception, where different base stations act together as a distributed antenna system, sharing data. CoMP has been shown to be sensitive to accuracy of channel knowledge. This work deals with practical channel estimation in an uplink joint reception scenario for multiple users across multiple cells. In most academic work, the parameter knowledge, like second order statistics of the channel and noise, is assumed to be perfectly known. In contrast to that, in this paper, we fully estimate all parameters using pilots. Practical algorithms are designed here to achieve fast convergence of parameter estimation, avoiding the need for too many samples, with manageable complexity. This is done in a multi-stage way, where the outputs of simpler estimators provide the parameters for the more advanced stages. Even for large coordination set sizes, like 7 cells, we show that our multi-stage approach is roughly just 1 dB below perfect channel knowledge in terms of post-combining SINR.