Effects of Downlink Channel Quantization on the Performance of Relative Calibration in OFDM Systems
The application of calibration techniques mitigating the front-end impairments in adaptive multi-antenna TDD systems designed for very high data rates is of paramount importance. Excellent calibration purely based on signal processing can be achieved by means of relative calibration. There, additional estimated DL channel state information is required at the transmitter, which must be sent back in reverse direction during a special calibration phase. This paper deals with the implementation of UL feedback of DL channel state information for online calibration. The fed back DL channel needs to be quantized before retransmission, which results in an inherent quantization error.