HE-LTF Alignment in 802.11ax MU-OFDMA Transmissions
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Solution Overview
Problem
In IEEE 802.11ax wireless communication systems, the non-alignment of Long Training Fields (LTFs) for different users during Multiple User (MU) or Orthogonal Frequency Division Multiple Access (OFDMA) transmissions can cause interference due to varying symbol lengths, leading to misalignment of HE-LTFs.
Innovation Solution
A method and apparatus for transmitting frames with aligned LTFs by extending the first LTF to match the symbol length of the second LTF, ensuring all LTFs have the same number of symbols, which can be achieved by using a processor to prepare frames with extended LTFs and a transceiver to transmit these frames, utilizing a P matrix to generate sequences for each LTF, and informing the symbol extension through signaling fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different number of LTF symbols are used for different users to support different spatial streams, then adaptability to various user requirements is improved, but interference among users occurs due to time domain misalignment
Solution Approach 1:
The patent changes the parameter of LTF symbol count from user-specific values to a unified maximum value for all users. By setting all users' LTF symbols to the same maximum count (Nmax), the system maintains adaptability through the signaling of different spatial stream configurations while eliminating interference caused by misaligned symbol durations in the time domain.
2Adaptability or versatility
If extra LTF symbols are inserted for users with more streams, then support for higher spatial streams is improved, but device complexity increases due to alignment requirements
Solution Approach 1:
The patent applies universality by establishing a common LTF symbol framework (Nmax) that serves all users regardless of their specific spatial stream requirements. This universal structure simplifies device complexity by providing a standardized alignment mechanism, while still accommodating different user needs through the signaling of individual spatial stream configurations within the unified framework.
Data Source
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AI summary
A method and apparatus for transmitting frames having a long training field (LTF) for a second type of station (STA) in a wireless communication system are provided. For this, STA prepares a frame having a first part for a first type of STA and a second part for the second type of STA; wherein the second part includes multiple LTFs, when the frame is used for MU (Multiple User) transmission scheme or OFDMA (Orthogonal Frequency Divisional Multiple Access) scheme. In case a first LTF having a first number of symbols length and a second LTF having a second number of symbols length, which is greater than the first number of symbols length, are used for the multiple LTFs, the first LTF is extended such that the first LTF and the second LTF have a same number of symbols length. The STA transmits the prepared frame to one or more STAs.