Multicell MIMO Calibration via Joint Sounding Sequences

The patent merges calibration operations across multiple base stations by having mobile stations transmit sounding signals that are received by multiple base stations simultaneously. This allows joint calibration where all base stations in a cooperative group calibrate their RF chains together using common reference signals, ensuring consistent calibration constants across the cooperative MIMO system while maintaining implementation simplicity.

The patent replaces traditional feedback-based channel state information acquisition with a sounding-based reciprocity exploitation approach. Instead of mobile stations measuring and feeding back downlink channel information, the system uses uplink sounding signals transmitted by mobile stations, which are received by base stations. Due to channel reciprocity in TDD systems, the uplink channel characteristics reflect the downlink channel characteristics, eliminating the need for large-capacity feedback while maintaining accurate channel knowledge for cooperative MIMO.

The patent makes the sounding signal serve multiple functions simultaneously: it acts as both a channel estimation reference signal and a calibration reference signal. By designing the sounding signal structure to be observable by multiple base stations and incorporating it into the joint calibration process, the system achieves both channel state acquisition and RF chain calibration without requiring separate signaling resources, thereby reducing overall system complexity despite involving multiple base stations.