HE-LTF Cyclic Prefix for WLAN AGC Estimation With Lower Preamble Overhead
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Solution Overview
Problem
Current automatic gain control methods in wireless local area networks (WLANs) require large system overheads due to the use of legacy short training fields (L-STF) and high throughput short training fields (HT-STF) for AGC estimation, which can be reduced by utilizing a high efficiency long training field with a cyclic prefix (CP) that allows for both AGC estimation and intersymbol interference prevention.
Innovation Solution
A physical layer packet with a high efficiency long training field containing N symbols, where the CP of the first symbol is set to a minimum length required for AGC estimation, enabling reduced preamble length and system overheads, while also preventing intersymbol interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If L-STF and HT-STF are used for AGC estimation, then AGC estimation can be performed, but system overheads are relatively large
Solution Approach 1:
The patent merges the AGC estimation function with the HE-LTF field by configuring its CP length to be greater than or equal to the minimum required for AGC estimation. This combines two previously separate functions (AGC estimation using L-STF/HT-STF and intersymbol interference prevention using HE-LTF CP) into a single integrated solution, eliminating the need for separate AGC training fields and reducing overall preamble overhead.
Solution Approach 2:
The HE-LTF field is given multi-functionality by enabling it to serve both as an intersymbol interference prevention mechanism (through its CP) and as an AGC estimation field. This universal approach allows the same field to perform multiple tasks, reducing the total number of dedicated fields needed and lowering system overheads.
2Measurement precision
If L-STF and HT-STF are used for AGC estimation, then AGC estimation can be performed, but preamble length increases
Solution Approach 1:
The patent merges the AGC estimation function with the HE-LTF field by configuring its CP length to be greater than or equal to the minimum required for AGC estimation. This combines two previously separate functions (AGC estimation using L-STF/HT-STF and intersymbol interference prevention using HE-LTF CP) into a single integrated solution, eliminating the need for separate AGC training fields and reducing overall preamble overhead.
Solution Approach 2:
The patent extracts the AGC estimation function from the traditional L-STF/HT-STF sequence and relocates it to the HE-LTF field. By taking out the AGC estimation requirement from the preamble structure and embedding it within the HE-LTF CP, the patent eliminates redundant fields and shortens the overall preamble length.
3Measurement precision
If CP length is increased for AGC estimation, then AGC accuracy improves, but intersymbol interference prevention capability is reduced
Solution Approach 1:
The patent applies parameter changes by specifically configuring the CP length of the first HE-LTF symbol to be greater than or equal to the minimum required for AGC estimation, while maintaining appropriate CP lengths for subsequent symbols to ensure intersymbol interference prevention. This selective parameter adjustment allows the system to optimize for both AGC estimation accuracy and reliability without compromising either function.
Data Source
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AI summary
The present invention discloses an automatic gain control method and a communications device in a wireless local area network. The method includes: generating a physical layer packet, where the physical layer packet includes a high efficiency long training field, the high efficiency long training field includes N symbols, a length of a cyclic prefix CP of a first symbol in the N symbols is greater than or equal to a minimum length required by a receiver device to perform automatic gain control AGC estimation, and N is a positive integer; and sending the physical layer packet to the receiver device. System overheads can be reduced according to embodiments of the present invention.