A Study of Precoding for LTE TDD Using Cell Specific Reference Signals

We investigate non-codebook-based multiple-input multiple-output (MIMO) precoding schemes for the time division duplex (TDD) mode of LTE where channel reciprocity could be exploited. Previously proposed non-codebook-based precoding schemes typically use UE specific reference signals for demodulation. Cell specific reference signals are however still transmitted for the transmission of common control signaling, mobility measurements and downlink channel quality measurements. In order to save the resources occupied by UE specific reference signals, and to simplify UE implementation, a non-codebook-based precoding scheme using cell-specific reference signals is considered. Link throughput simulations indicate that such scheme outperforms the scheme using UE specific reference signals in the scenario with high transmit antenna correlation and low UE velocity.