ICD reciprocity calibration for distributed large-scale MIMO systems with BD precoding

摘要

Time division duplexing (TDD) operation is usually used for distributed large-scale multiple-input multiple-output (MIMO) systems to perform the downlink precoding by the uplink channel estimation due to the channel reciprocity. However, the channel reciprocity is often disabled by the non-symmetric transceiver radio frequency (RF) circuits at both sides of the link. This paper is focused on the reciprocity calibration for the distributed large-scale MIMO systems where both access points (APs) and user equipments (UEs) have multiple antennas. Theoretical analysis show that RF mismatches at the UEs still bring the inter-stream interference (ISI) and lead to a significant performance loss, although with the perfect partial calibration. Then, to avoid eigenvalue decomposition (EVD) operation of the total least squares (TLS) method, an iterative algorithm named as iterative coordinate descent (ICD) method is proposed to perform the full calibration, which significantly reduces the complexity and essentially achieves the performance of the TLS method.