NDP Implicit Sounding for WLAN Channel Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless local area network (WLAN) systems face inefficiencies in channel sounding procedures, particularly due to significant signaling overhead and delays in updating channel information, which degrade multi-user multiple-input multiple-output (MU-MIMO) performance.
Innovation Solution
Implementing a null data packet (NDP) based implicit sounding procedure that allows access points (APs) to perform channel estimation and precoding for both uplink and downlink transmissions without explicit channel sounding, using NDP announcement frames to prompt stations (STAs) to transmit NDPs, and calibrating channel responses to compensate for hardware differences between transmit and receive chains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If explicit channel sounding procedure is used, then channel information can be obtained, but signaling overhead increases and updates are delayed
Solution Approach 1:
Instead of the traditional explicit sounding where the AP transmits sounding packets and STAs send feedback, this patent inverts the approach by having STAs transmit NDPs spontaneously and the AP performs implicit sounding by measuring the uplink NDPs to derive downlink channel information through reciprocity
Solution Approach 2:
The STAs perform self-sounding by transmitting their own NDPs without requiring explicit AP initiation or coordination, allowing the AP to automatically capture channel state information through the uplink transmissions
2Measurement precision
If explicit channel sounding procedure is used, then channel information can be obtained, but signaling overhead increases
Solution Approach 1:
The patent extracts only the essential channel estimation function from the complex explicit sounding protocol, eliminating unnecessary signaling exchanges by using the uplink NDP transmissions alone to derive downlink channel information through reciprocity
Solution Approach 2:
The patent inverts the traditional sounding architecture where the AP initiates and controls the sounding process, instead allowing STAs to spontaneously transmit NDPs and having the AP passively capture the necessary channel information
3Measurement precision
If explicit channel sounding procedure is used, then channel information can be obtained, but processing complexity increases
Solution Approach 1:
The patent extracts the core channel estimation function and eliminates the complex coordination, feedback processing, and multi-step exchange procedures of explicit sounding, reducing processing complexity while maintaining measurement accuracy
Data Source
AI summary
This disclosure provides systems, devices, apparatus and methods, including computer programs encoded on storage media, for null data packet (NDP) based implicit sounding and calibration for a wireless local area network (WLAN). An AP may perform a calibration procedure with one or more stations (STAs) that involves NDP transmissions. The AP may calibrate an effective downlink channel response to an effective uplink channel to compensate for transmit and receive chain differences. The AP may initiate implicit sounding by transmitting a downlink message that includes an uplink NDP announcement frame to the one or more STAs, prompting uplink multi-user (MU) NDP transmission. The AP may estimate the uplink channel based on measuring the received NDPs and mirror the estimated uplink channel for reciprocal downlink channel estimation and precoding generation. The AP may perform MU multiple input multiple output (MIMO) downlink transmission that is precoded based on the channel estimation.