TECHNICAL FIELD

The subject application is related to wireless communication systems, and, for example, to channel state information (CSI) feedback from mobile communication devices to base station devices.

BACKGROUND

Channel state information (CSI) includes information sent from a mobile device, such as a cellular telephone, to a transmitter such as a base station. CSI provides information about the quality of radio frequency signals received at the mobile device. CSI can be used for any number of purposes, including but not limited to adjusting signal transmission, by the base station, as needed to improve signal quality at the mobile device.

Time-division duplex (TDD) communications use a same radio frequency for uplink communications from the mobile device to the base station, and downlink communications from the base station to the mobile device. The procurement of CSI for TDD communications benefits from channel reciprocity, because, for example, a base station receiver can estimate CSI in the uplink from the mobile device to the base station, and the base station can apply the estimated CSI in the downlink from the base station to the mobile device. This is because in TDD, the base station transmitter operates in the same spectrum as the base station receiver.

This is in contrast to frequency-division duplex (FDD) communications, where the base station transmitter and receiver operate simultaneously in different parts of the frequency spectrum and hence, the mobile device estimates CSI in one part of the spectrum (the downlink from the base station transmitter) and provides CSI feedback in the uplink to the base station receiver in a different part of the spectrum. Such CSI feedback incurs overhead and additional complexity at the mobile device, especially for so-called Type II CSI feedback schemes in the Third Generation Partnership Project (3GPP) New Radio (NR) fifth generation (5G) mobile communications standard.

Technologies which efficiently collect and send CSI for FDD communications in wireless communication networks are therefore desired.

