HE-LTF Sequence Generation for Multi-User CFO Measurement
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Solution Overview
Problem
In next-generation WLAN systems, there is a limitation in measuring different carrier frequency offsets (CFO) for each user using existing channel estimation and pilot methods, particularly in multi-user multiple input multiple output (MIMO) transmission scenarios.
Innovation Solution
A method is proposed to generate a high efficiency-long training field (HE-LTF) sequence in the frequency domain for multi-user transmission, which involves multiplying a predefined sequence by one row of a P matrix, allowing for efficient carrier frequency offset and channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing channel estimation and pilot methods are used in multi-user MIMO transmission, then system compatibility is maintained, but carrier frequency offset measurement precision deteriorates
Solution Approach 1:
The patent segments the training field into distinct components: legacy training fields for backward compatibility and HE-LTF sequences dedicated to multi-user transmission. This segmentation allows separate optimization of CFO measurement for each user without interfering with existing single-user mechanisms, thereby improving measurement precision while maintaining system compatibility.
Solution Approach 2:
The patent introduces HE-LTF sequences as an intermediary element between the legacy training fields and the multi-user data transmission. These intermediary sequences carry user-specific information including CFO measurements, enabling accurate frequency offset estimation for multiple users without requiring modification of the existing legacy training field structure.
2Productivity
If multi-user MIMO transmission is implemented, then spectrum efficiency is improved, but measurement of different carrier frequency offsets for each user becomes difficult
Solution Approach 1:
The patent applies local quality by assigning user-specific HE-LTF sequences with distinct properties to different users in the multi-user MIMO system. Each user's training sequence is locally optimized to carry that user's specific CFO information, allowing individualized frequency offset measurement for each user while maintaining overall system spectral efficiency.
3Measurement precision
If HE-LTF sequences are generated by multiplying predefined sequence by P matrix rows, then CFO measurement accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-defining the P matrix structure and its relationship with the predefined sequences before actual transmission. This pre-computation allows the receiving end to efficiently generate expected HE-LTF sequences for comparison, reducing real-time computational power requirements while maintaining CFO measurement accuracy.
Data Source
AI summary
Disclosed are a method for multi-user transmission and reception in a wireless communication system and a device for same. More particularly, a method for performing multi-user (MU) transmission by a station (STA) device in a wireless communication system comprises the steps of: generating a high efficiency-long training field (HE-LTF) sequence in a frequency domain in accordance with an MU transmission bandwidth; and transmitting a physical protocol data unit (PPDU) which comprises one or more symbols to which the HE-LTF sequence is mapped, wherein the HE-LTF sequence can be generated by multiplying one row of a P matrix to a length unit of a row of the P matrix in a predetermined sequence.