LTF Sequence Layout for Low-PAPR Wideband PPDU Transmission
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Solution Overview
Problem
The existing IEEE 802.11ax standard struggles to meet the increasing demands for high throughput, low jitter, and low latency in wireless communication, particularly with the introduction of wider bandwidths like 240 MHz and 320 MHz, due to high Peak to Average Power Ratio (PAPR) issues in the Long Training Field (LTF) sequences.
Innovation Solution
The method and apparatus provide LTF sequences with low PAPR for various bandwidths, including operations such as negating elements, reversing sequences, and multiplying by -1, to ensure low PAPR on single and combined resource units and entire bandwidths, especially in multi-stream scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wider bandwidths (240 MHz, 320 MHz) are used to increase throughput, then system throughput is improved, but PAPR of LTF sequences increases
Solution Approach 1:
The patent divides the wide bandwidth into multiple sub-bandwidths (e.g., two 120 MHz bandwidths for 240 MHz, four 80 MHz bandwidths for 320 MHz) and generates LTF sequences independently for each sub-bandwidth. This segmentation allows the system to maintain low PAPR in each sub-band while achieving high throughput across the entire wide bandwidth, directly resolving the contradiction between throughput and PAPR.
Solution Approach 2:
The patent applies multiple parameter transformation operations (negating elements, reversing sequences, multiplying by -1) to the LTF sequences. These parameter changes create multiple versions of LTF sequences with different PAPR characteristics, allowing the system to select or combine sequences that achieve both high throughput and low PAPR, thereby resolving the contradiction.
2Object-affected harmful factors
If LTF sequences are designed for low PAPR on single resource unit, then PAPR is reduced, but channel estimation accuracy may be compromised
Solution Approach 1:
The patent combines multiple LTF sequences generated through different operations (negation, reversal, multiplication) to form a complete LTF sequence for the entire bandwidth. This merging process ensures that while individual sub-sequences maintain low PAPR, the combined sequence provides sufficient energy and diversity for accurate channel estimation across all resource units, resolving the contradiction between PAPR reduction and estimation accuracy.
Solution Approach 2:
The patent designs LTF sequences that simultaneously serve multiple functions: they maintain low PAPR to avoid amplifier distortion while also providing adequate correlation properties for channel estimation. The multiple transformed versions of the sequences ensure that at least one version achieves both low PAPR and good estimation performance, making the solution universally applicable across different bandwidths and scenarios.
3Adaptability or versatility
If existing 802.11ax standard is used, then compatibility is maintained, but throughput and latency requirements are not met
Solution Approach 1:
The patent extends the LTF sequence design to be dynamic and adaptable to different bandwidth configurations (80 MHz, 160 MHz, 240 MHz, 320 MHz). By implementing a flexible LTF generation framework that can operate across multiple bandwidths, the system maintains compatibility with existing 802.11ax standards while enabling future-proof performance for higher throughput and lower latency requirements, thus resolving the contradiction between compatibility and productivity.
Data Source
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AI summary
This application relates to the field of wireless communication technologies, and in particular, to a method and an apparatus for transmitting a physical layer protocol data unit, and for example, is applied to a wireless local area network. The method includes: A first communications device generates a PPDU and may send the PPDU, where the PPDU includes an LTF sequence; and correspondingly, a second communications device receives the PPDU, and parses the PPDU to obtain the LTF sequence included in the PPDU. Embodiments of this application can be used to design an LTF sequence that has a relatively low PAPR on entire bandwidth, on a single resource unit, on a combined resource unit, and in a considered multi-stream scenario.