Methods for channel estimation in OFDMA based hybrid beamforming (HBF) systems

A method of operating an Orthogonal Frequency Division Multiple Access (OFDMA) Hybrid BeamForming (HBF) system wherein a transmitter and receiver communicate over a channel and each include a plurality of Radio Frequency (RF) chains and an antenna array of antenna elements corresponding to each RF chain, and wherein the transmitter includes an analog beamformer and the receiver includes an analog combiner, the method comprising:

• generating a set of orthogonal Tx training beams for the transmitter based upon a number of antenna elements in the transmitter antenna array;
• generating a set of orthogonal Rx training beams for the receiver based upon a number of antenna elements in the receiver antenna array;
• probing the channel by simultaneously transmitting OFDMA preambles with each RF chain using a different one of the orthogonal Tx training beams and receiving the OFDMA preambles with each of the orthogonal Rx training beams in a scheduling sequence that includes a pairing of each orthogonal Tx training beam with each orthogonal Rx training beam;
• performing channel estimation based upon probing feedback results including a channel response between different pairs of the orthogonal Tx training beams and the orthogonal Rx training beams;
• and
• adjusting transmit beams in the analog beamformer of the transmitter and receive beams in the analog combiner of the receiver based upon the channel estimation.

A wireless communications device for operation in an Orthogonal Frequency Division Multiple Access (OFDMA) Hybrid BeamForming (HBF) system, the wireless communications device comprising:

• a transmitter including a digital precoder, a plurality of Radio Frequency (RF) chains, an analog beamformer and an array of antenna elements corresponding to each RF chain, and configured to communicate over a channel with a receiver that includes a plurality of RF chains, an antenna array of antenna elements corresponding to each RF chain, an analog combiner and a digital decoder;
• and
• a controller including one or more integrated circuit devices configured to
• generate a set of orthogonal Tx training beams for the transmitter based upon a number of antenna elements in the transmitter antenna array for reception at the receiver via a set of orthogonal Rx training beams that are based upon a number of antenna elements in the receiver antenna array,
• probe the channel by controlling the transmitter to simultaneously transmit OFDMA preambles with each RF chain using a different one of the orthogonal Tx training beams for reception of the OFDMA preambles with each of the orthogonal Rx training beams in a scheduling sequence that includes a pairing of each orthogonal Tx training beam with each orthogonal Rx training beam, and
• adjust transmit beams in the analog beamformer of the transmitter in view of channel estimation information from the receiver based upon probing feedback results including a channel response between different pairs of the orthogonal Tx training beams and the orthogonal Rx training beams.