ELR WLAN Preamble Detection and Power Measurement at Low SNR
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Solution Overview
Problem
The enhanced long range (ELR) mode in IEEE 802.11bn amendment introduces challenges in preamble detection and power level measurement due to differences in physical layer protocol data units (PPDUs), leading to unreadable portions for non-ELR devices and lower signal-to-noise ratios, complicating network allocation vector (NAV) updates and clear channel assessment.
Innovation Solution
Techniques for updating a device's NAV based on ELR PPDU receipt, determining power levels for spatial reuse, and improving preamble detection through autocorrelation and power boosting of specific fields in the ELR PPDU, such as the ELR-C and ELR-STF, to enhance channel assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ELR mode is implemented with different PPDU structure, then long-range connection reliability is improved, but compatibility with legacy devices deteriorates and power level measurement becomes complicated
Solution Approach 1:
The PPDU is divided into legacy preamble portion (L-STF, L-LTF, L-SIG, RL-SIG, U-SIG) and ELR preamble portion (ELR-C, ELR-STF, ELR-LTF, ELR-SIG), allowing legacy devices to process the first portion while ELR devices process the entire structure. This segmentation enables backward compatibility while supporting enhanced long-range functionality.
Solution Approach 2:
The legacy preamble portion acts as an intermediary that enables legacy devices to detect and process the beginning of the transmission, while the ELR preamble portion provides additional information for ELR devices. This intermediary structure allows coexistence of different device types in the same network.
2Difficulty of detecting and measuring
If ELR PPDU uses power boosted fields, then preamble detection capability is improved, but power level measurement accuracy for spatial reuse deteriorates
Solution Approach 1:
Different fields within the PPDU have different power characteristics - the L-STF and L-LTF are power boosted to enhance preamble detection, while the L-SIG and subsequent fields maintain normal power levels for accurate power measurement. This local differentiation of power quality allows both detection and measurement functions to coexist.
Solution Approach 2:
The PPDU is segmented into fields with different power characteristics, allowing the receiver to apply different processing methods to different segments - power boosted processing for detection fields and normal power processing for measurement fields.
3Length of moving object
If ELR mode operates at lower SNR, then transmission range is extended, but preamble detection becomes more challenging
Solution Approach 1:
The L-STF and L-LTF fields are power boosted before transmission to create a stronger initial signal that facilitates preamble detection even at lower SNR conditions. This preliminary action of boosting power in critical detection fields enables extended range operation without sacrificing detection capability.
Solution Approach 2:
The transmission parameters are changed by applying power boosting to specific fields (L-STF, L-LTF) while maintaining other parameters unchanged, creating an optimized signal structure for low SNR operation that enhances detection probability.
Data Source
AI summary
A wireless device configured for communication in a wireless local area network (WLAN) may determine whether a detected physical layer protocol data unit (PPDU) is an enhanced long range (ELR) PPDU or a non-ELR PPDU and may estimate a power level for a data field of the detected PPDU. The device may use the estimated power level for determining a PHY-CCA indication primitive. The estimated power level for an ELR data field may be determined based on predetermined power boost levels of one or more fields in the ELR PPDU. For a spatial reuse transmission, a transmit power level may be determined based on the estimated power level for the ELR data field. A ELR PPDU may comprise a legacy preamble followed by a ELR preamble and an ELR data field. The ELR preamble may comprise an ELR classification field followed by an ELR-STF, an ELR-LTF and an ELR-SIG.