Today’s Patent – RF Calibration via Channel Reciprocity in Distributed Wireless Systems

The said invention (US12224819B2) was invented by Antonio Forenza Fadi, Saibi Timothy A. Pitman. Stephen G. Perlman and patented by USPTO on July 15^th, 2024. Currently, it stands assigned to the Rearden LLC.

This invention relates to systems and methods for radio frequency (RF) calibration in multi-user, multiple-antenna systems (MU-MAS) that exploit uplink/downlink channel reciprocity. In these systems, a large array of antennas—typically more than eight—is used within a radio access network (RAN) to transmit training signals between antennas, enabling estimation of RF calibration coefficients. These coefficients allow the system to convert uplink channel state information (UL CSI) into downlink CSI (DL CSI), avoiding traditional feedback-heavy closed-loop approaches. The resulting DL CSI is then used for open-loop precoding, enabling multiple radio signals to be transmitted simultaneously without inter-user interference.

The disclosed methods and systems support distributed antenna architectures and can operate in cell-free RAN configurations. By leveraging uplink data received from user equipment (UE) devices and applying RF calibration, the system can precode downlink transmissions such that deliberate interference between signals results in spatial separation at each UE. This increases spectral efficiency and system capacity. The antennas and processing units may be interconnected to a centralized processor for coordination, enabling efficient and scalable wireless communication in dense, high-demand environments.