EHT PPDU LTF Sequence Mapping for WLAN Overhead Reduction
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Solution Overview
Problem
In wireless local area networks (WLANs), the increase in spatial streams for high throughput (HT) transmission leads to an increased overhead due to the number of long training field (LTF) symbols, which affects data rate and efficiency.
Innovation Solution
The proposal involves generating and transmitting compressed, orthogonal, or cyclic-shifted LTF sequences for the first to fourth spatial streams, allowing for efficient mapping onto tones in the frequency domain, thereby reducing overhead and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of spatial streams is increased to 16 for high throughput transmission, then data rate is improved, but overhead due to the number of long training field (LTF) symbols is increased
Solution Approach 1:
The patent combines LTF sequences for multiple spatial streams (first to fourth streams) into a single LTF symbol by mapping them onto different tones in the frequency domain. Specifically, LTF sequences for four spatial streams are mapped onto subcarriers with 4-tone spacing, allowing multiple streams to share the same time-frequency resource and reducing the number of LTF symbols required from 16 to 4, thereby reducing overhead while maintaining support for 16 spatial streams
Solution Approach 2:
The patent transitions from time-domain separation of LTF sequences to frequency-domain multiplexing. Instead of transmitting separate LTF symbols for each spatial stream in the time domain, the invention maps LTF sequences for multiple spatial streams onto different frequency tones (subcarriers) within a single LTF symbol, utilizing the frequency dimension to accommodate multiple streams simultaneously
Data Source
AI summary
Proposed are a method and device for transmitting EHT PPDU in a wireless LAN system. Particularly, a transmission STA generates first and second LTF symbols. The transmission STA transmits EHT PPDU comprising the first and second LTF symbols to a reception STA. The first and second LTF symbols are generated on the basis of an LTF sequence for first to fourth spatial streams. In the first LTF symbol, the LTF sequence for the first to fourth spatial streams is mapped to tones in four tone units in a frequency domain. In the second LTF symbol, the LTF sequence for the first to fourth spatial streams is mapped to tones in four tone units in a frequency domain. The LTF sequence, for the first to fourth spatial streams, mapped to the frequency domain of the second LTF symbol is mapped to a tone by means of cyclic shifting, by two tones, the LTF sequence, for the first to fourth spatial streams, mapped to the frequency domain of the first LTF symbol.