Wireless Channel Calibration Using Acknowledgement Frames
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Solution Overview
Problem
Existing beamforming calibration techniques in wireless communication systems are ineffective for devices that cannot transmit null data packets (NDPs), such as single space-time stream devices, as they are not configured to support NDPs, preventing implicit beamforming and channel calibration.
Innovation Solution
The proposed solution involves using an acknowledgement frame as a sounding frame instead of an NDP for calibration, allowing the beamforming device to estimate the channel and determine correction matrices, enabling effective beamforming calibration between a beamforming device and a single space-time stream device by transmitting a calibration initiation frame, receiving an acknowledgement frame, and subsequently sending a null data packet to determine channel state information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If null data packets (NDPs) are used as sounding frames for beamforming calibration, then channel calibration accuracy is improved, but single space-time stream devices cannot participate in calibration
Solution Approach 1:
The patent uses an acknowledgement frame as an intermediary substitute for NDPs. Single space-time stream devices send acknowledgement frames containing channel state information instead of NDPs, allowing the beamforming device to perform calibration using this alternative sounding frame without requiring NDP transmission capability from the single stream device.
Solution Approach 2:
The patent changes the type of sounding frame used for calibration from NDP to acknowledgement frame. By modifying the frame type and its content structure (including channel state information in the acknowledgement), the system enables calibration participation for single space-time stream devices while maintaining calibration functionality.
2Productivity
If beamforming calibration is performed using traditional NDP-based methods, then MIMO channel performance is improved, but single space-time stream devices are excluded from implicit beamforming
Solution Approach 1:
The patent makes the acknowledgement frame serve multiple functions: it acts as both an acknowledgment of receipt and as a sounding frame for channel calibration. This multi-functionality allows single space-time stream devices to participate in beamforming calibration without requiring separate NDP transmission capability, thereby expanding device support coverage while maintaining throughput improvement benefits.
3Reliability
If correction matrices are determined using NDPs, then transmit and receive chain impairments are corrected, but devices unable to transmit NDPs cannot benefit from impairment correction
Solution Approach 1:
The acknowledgement frame serves as an intermediary that carries channel state information sufficient for the beamforming device to determine correction matrices. This allows single space-time stream devices to benefit from impairment correction through the acknowledgement frame mechanism without needing to transmit NDPs, thereby maintaining reliability improvement while expanding device compatibility.
Data Source
AI summary
This document describes, among other things, a method that includes transmitting a calibration initiation frame from a first wireless communication device to a second wireless communication device that comprises a single space-time stream transmitter via a wireless communication medium. The method also includes receiving at the first wireless communication device an acknowledgement frame sent from the second wireless communication device after the second wireless communication device receives the calibration initiation frame. The method further includes transmitting a null data packet (NDP) frame from the first wireless communication device to the second wireless communication device after receiving the acknowledgement frame. In some implementations, the method also includes performing beamforming calibration of a wireless communication channel between the first wireless communication device and the second wireless communication device based on the acknowledgement frame.