On Feedback Requirements for CoMP Joint Transmission in the Quasi-Static User Regime

In this work we focus on the downlink direction of cellular multi-user MIMO systems based on OFDM waveforms. Our target system is operated in the frequency division duplex (FDD) mode, while all base stations (BSs) use the same frequency spectrum for downlink transmission. State- of-the-art literature proved that the system performance is mainly limited by the existing co-channel interference. Hence, mitigating these effects would improve the achievable system throughput beyond current benchmarks of cellular systems. Therefore, coordinated multi-point (CoMP) joint transmission (JT) is currently studied in Third Generation Partnership Project (3GPP). However, feedback demands due to massive channel state information (CSI) feedback cause a significant problem. By combining sub-clustering concepts for cooperative BSs with linear channel prediction methods in a thorough time-variant system-level analysis, we show that CSI feedback rates can be scaled down to less than 200 kBit/s per user.