RF Beamforming Basis Function Feedback for mmWave Channel Estimation
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Solution Overview
Problem
The challenge in millimeter wave (mmWave) beamforming is obtaining full channel knowledge due to high power consumption by analog to digital (A-D) and digital to analog (D-A) converters, making traditional baseband array processing impractical, and the need for a more efficient method to determine channel gain and phase between transmit and receive antennas.
Innovation Solution
The method involves transmitting sounding waveforms from orthogonal basis functions using a transmit array and receiving feedback messages with gain and phase values for the best basis functions, allowing for efficient channel estimation without the need for full baseband transceivers behind each antenna, utilizing a Kronecker product of DFT matrix columns for basis function creation and reducing the number of sounding waveforms needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional baseband array processing is used to obtain full channel knowledge, then channel estimation accuracy is improved, but power consumption increases due to A-D and D-A converters
Solution Approach 1:
The patent segments the channel estimation process into two parts: (1) transmitting sounding waveforms from a reduced set of B orthogonal basis functions instead of all Q transmit antennas, and (2) using feedback from the receiver to identify the MB best basis functions. This segmentation allows the transmitter to obtain channel knowledge for the most important spatial directions without processing all antenna signals through power-consuming baseband converters.
Solution Approach 2:
The patent applies partial action by transmitting sounding waveforms from only B basis functions (where B < Q) rather than all Q transmit antennas. The receiver identifies the MB best basis functions (where MB < Q) that capture the dominant channel characteristics. This partial processing approach achieves sufficient channel estimation accuracy for beamforming while avoiding the power consumption of processing all antenna signals through baseband converters.
2Loss of information
If sounding waveforms are transmitted from all Q transmit antennas, then full channel knowledge is obtained, but system overhead and processing complexity increase
Solution Approach 1:
The patent extracts only the essential channel information by having the receiver identify and feed back the indices of the MB best basis functions along with their gain and phase values. This extraction approach captures the dominant spatial characteristics of the channel without requiring the transmitter to process or store channel state information for all Q transmit antennas, thereby reducing processing complexity and system overhead.
Solution Approach 2:
The patent uses orthogonal basis functions (such as DFT beams) as simplified representations or copies of the actual antenna radiation patterns. Instead of measuring and processing the complete channel response from all Q antennas, the system uses these pre-defined basis functions to probe the channel and captures the essential spatial information through the feedback of the best MB basis function indices and their corresponding channel parameters.
3Measurement precision
If feedback messages include all channel state information, then channel knowledge accuracy is improved, but feedback overhead increases
Solution Approach 1:
The patent extracts only the critical channel state information needed for beamforming by having the receiver feed back (1) the indices of the MB best basis functions and (2) the corresponding gain and phase values for each selected basis function. This extracted feedback set captures the essential spatial channel characteristics while avoiding transmission of redundant information, thereby achieving accurate channel knowledge with reduced feedback overhead.
Data Source
AI summary
Methods, apparatuses, systems, and computer program products for obtaining full channel knowledge between each transmitter and each receiver when using radio frequency (RF) beamforming are provided. One method described herein includes a method of obtaining channel knowledge at a transmitter with Q transmit antennas for use in beamforming where the transmitter transmits sounding waveforms from B orthogonal basis functions from a transmit array comprised of the Q transmit antennas. In response to the transmitted sounding waveforms the transmitter receives at least one feedback message from a receiver. The feedback message(s) may include an indication of the best MB basis functions plus a gain and phase value for each of the MB basis functions.