# US 10,321,460 B1 · Orthogonal frequency division multiplexing (OFDM) transmit protocol selection based on a feedback loop lag condition > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,321,460 B1 - Document ID: US10321460B1 - Status: Granted - Kind: B1 - Application number: 14/795,604 - Filed: 2015-07-09 - Granted: 2019-06-11 - Earliest claimed: 2015-07-09 - Assignees: Sprint Communications Company L.P. - Applicants: Sprint Communications Company L.P. - Inventors: Nagi A. Mansour; Marouane Balmakhtar; Aaron J. Pawlowski; Kaushik Goswami - Web page: https://patentgrep.com/patent/US10321460B1 ## CPC - H04B 7/0413: MIMO systems - H04B 1/40: Circuits - H04B 7/0617: {for beam forming} - H04B 7/0689: {using different transmission schemes, at least one of them being a diversity transmission scheme} - H04L 27/2646: {using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length} - H04L 27/2634: {Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation} - H04W 88/08: Access point devices - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract An Orthogonal Frequency Division Multiplexing (OFDM) access point receives and processes beamforming feedback data from User Equipment (UE) to form a beamforming feedback loop, transmits a beamformed radio signal to the UE, and determines if the beamforming feedback loop is experiencing a beamforming lag condition, and if so, switches to a closed-loop spatial multiplexing transmit protocol. The OFDM access point receives and processes closed-loop spatial multiplexing feedback data from the UE to form a closed-loop spatial multiplexing feedback loop, transmits a closed-loop spatial multiplexed radio signal to the UE, and determines if the closed-loop spatial multiplexing feedback loop is experiencing a spatial multiplexing lag condition, and if so, switches to an open-loop spatial multiplexing transmit protocol. An OFDM access point receives and processes open-loop spatial multiplexing feedback data from the UE to form an open-loop spatial multiplexing feedback loop and transmits an open-loop spatial multiplexed radio signal to the UE. ## Claims ### Claim 1 A method of operating an Orthogonal Frequency Division Multiplexing (OFDM) access point comprising: receiving and processing beamforming feedback data from User Equipment (UE) to form a beamforming feedback loop and responsively transmitting a beamformed radio signal to the UE; determining that the beamforming feedback data is randomly changing in response to adjustments, and responsively switching to a closed-loop spatial multiplexing transmit protocol; receiving and processing closed-loop spatial multiplexing feedback data from the UE to form a closed-loop spatial multiplexing feedback loop and responsively transmitting a closed-loop spatial multiplexed radio signal to the UE; determining that the closed-loop spatial multiplexing feedback data is randomly changing in response to adjustments, and responsively switching to an open-loop spatial multiplexing transmit protocol; and receiving and processing open-loop spatial multiplexing feedback data from the UE to form an open-loop spatial multiplexing feedback loop and responsively transmitting an open-loop spatial multiplexed radio signal to the UE. ### Claim 2 (depends on 1) The method of claim 1 wherein the beamforming feedback data and the beamforming feedback loop comprise Long Term Evolution (LTE) Transmission Mode 8 (TM8). ### Claim 3 (depends on 1) The method of claim 1 wherein the beamforming feedback data and the beamforming feedback loop comprise Long Term Evolution (LTE) Transmission Mode 9 (TM9). ### Claim 4 (depends on 1) The method of claim 1 wherein the closed-loop spatial multiplexing feedback data and the closed-loop spatial multiplexing feedback loop comprise Long Term Evolution (LTE) Transmission Mode 4 (TM4). ### Claim 5 (depends on 1) The method of claim 1 wherein the open-loop spatial multiplexing feedback data and the open-loop spatial multiplexing feedback loop comprise Long Term Evolution (LTE) Transmission Mode 3 (TM3). ### Claim 6 (depends on 1) The method of claim 1 wherein the beamforming feedback data and the beamforming feedback loop comprise dual-layer beamforming feedback data and a dual-layer beamforming feedback loop and further comprising: receiving and processing multi-layer beamforming feedback data from the UE to form a multi-layer beamforming feedback loop and responsively transmitting a multi-layer beamformed radio signal to the UE; determining that the multi-layer beamforming feedback data is randomly changing in response to adjustments, and responsively switching to a dual-layer beamforming transmit protocol; and transmitting a dual-layer beamformed radio signal to the UE. ### Claim 7 (depends on 6) The method of claim 6 wherein the dual-layer beamforming feedback data and the dual-layer beamforming feedback loop comprise Long Term Evolution (LTE) Transmission Mode 8 (TM8). ### Claim 8 (depends on 6) The method of claim 6 wherein the multi-layer beamforming feedback data and the multi-layer beamforming feedback loop comprise Long Term Evolution (LTE) Transmission Mode 9 (TM9). ### Claim 9 (depends on 6) The method of claim 6 wherein: the multi-layer beamforming feedback data comprises first multi-layer beamforming feedback data for a first set of data layers and second multi-layer beamforming feedback data for a second set of data layers; the multi-layer beamforming feedback loop comprises first multi-layer beamforming feedback loop for the first set of the data layers and a second multi-layer beamforming feedback loop for the second set of the data layers; determining that the first and the second multi-layer beamforming feedback data is randomly changing in response to adjustments, and responsively switching to the dual-layer beamforming transmit protocol; and transmitting a dual-layer beamformed radio signal to the UE. ### Claim 10 (depends on 1) The method of claim 1 wherein the OFDM access point comprises a Long Term Evolution (LTE) network. ### Claim 11 An Orthogonal Frequency Division Multiplexing (OFDM) access point comprising: a data processing system configured to process beamforming feedback data received by a wireless communication transceiver from User Equipment (UE) to form a beamforming feedback loop, and the wireless communication transceiver configured to responsively transmit a beamformed radio signal to the UE; the data processing system configured to determine that the beamforming feedback data is randomly changing in response to adjustments, and responsively switch to a closed-loop spatial multiplexing transmit protocol; the data processing system configured to process closed-loop spatial multiplexing feedback data received by the wireless communication transceiver from the UE to form a closed-loop spatial multiplexing feedback loop, and the wireless communication transceiver configured to responsively transmit a closed-loop spatial multiplexed radio signal to the UE; the data processing system configured to determine that the closed-loop spatial multiplexing feedback data is randomly changing in response to adjustments, and responsively switch to an open-loop spatial multiplexing transmit protocol; and the data processing system configured to process open-loop spatial multiplexing feedback data received by the wireless communication transceiver from the UE to form an open-loop spatial multiplexing feedback loop, and the wireless communication transceiver configured to responsively transmit an open-loop spatial multiplexed radio signal to the UE. ### Claim 12 (depends on 11) The OFDM access point of claim 11 wherein the beamforming feedback data and the beamforming feedback loop comprise Long Term Evolution (LTE) Transmission Mode 8 (TM8). ### Claim 13 (depends on 11) The OFDM access point of claim 11 wherein the beamforming feedback data and the beamforming feedback loop comprise Long Term Evolution (LTE) Transmission Mode 9 (TM9). ### Claim 14 (depends on 11) The OFDM access point of claim 11 wherein the closed-loop spatial multiplexing feedback data and the closed-loop spatial multiplexing feedback loop comprise Long Term Evolution (LTE) Transmission Mode 4 (TM4). ### Claim 15 (depends on 11) The OFDM access point of claim 11 wherein the open-loop spatial multiplexing feedback data and the open-loop spatial multiplexing feedback loop comprise Long Term Evolution (LTE) Transmission Mode 3 (TM3). ### Claim 16 (depends on 11) The OFDM access point of claim 11 wherein the beamforming feedback data and the beamforming feedback loop comprise dual-layer beamforming feedback data and a dual-layer beamforming feedback loop and further comprising: the data processing system configured to process multi-layer beamforming feedback data received by the wireless communication transceiver from the UE to form a multi-layer beamforming feedback loop, and the wireless communication transceiver configured to responsively transmit a multi-layer beamformed radio signal to the UE; the data processing system configured to determine that the multi-layer beamforming feedback data is randomly changing in response to adjustments, and responsively switch to a dual-layer beamforming transmit protocol; and the wireless communication transceiver configured to transmit a dual-layer beamformed radio signal to the UE. ### Claim 17 (depends on 16) The OFDM access point of claim 16 wherein the dual-layer beamforming feedback data and the dual-layer beamforming feedback loop comprise Long Term Evolution (LTE) Transmission Mode 8 (TM8). ### Claim 18 (depends on 16) The OFDM access point of claim 16 wherein the multi-layer beamforming feedback data and the multi-layer beamforming feedback loop comprise Long Term Evolution (LTE) Transmission Mode 9 (TM9). ### Claim 19 (depends on 16) The OFDM access point of claim 16 wherein: the multi-layer beamforming feedback data comprises first multi-layer beamforming feedback data for a first set of data layers and second multi-layer beamforming feedback data for a second set of data layers; the multi-layer beamforming feedback loop comprises first multi-layer beamforming feedback loop for the first set of the data layers and a second multi-layer beamforming feedback loop for the second set of the data layers; the data processing system configured to determine that the multi-layer beamforming feedback data is randomly changing in response to adjustments, and responsively switch to the dual-layer beamforming transmit protocol; and the wireless communication transceiver configured to transmit a dual-layer beamformed radio signal to the UE. ### Claim 20 (depends on 11) The OFDM access point of claim 11 wherein the OFDM access point comprises a Long Term Evolution (LTE) network.