HE-LTF Sequence Mapping for Low-PAPR WLAN Transmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing WLAN standards lack a defined 1x HE-LTF sequence, leading to high peak-to-average power ratio (PAPR) values in OFDM communication scenarios, which affect system performance.
Innovation Solution
A method is introduced to determine and generate a 1x HE-LTF sequence in frequency domain based on transmission bandwidth and mode, using orthogonal mapping matrices and cyclic shift delays to reduce PAPR, applicable to both SU and DL-MU-MIMO data packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing WLAN standards are used without defined 1x HE-LTF sequence, then OFDM communication can be maintained, but PAPR values become excessively high affecting system performance
Solution Approach 1:
The patent applies parameter changes by modifying the HE-LTF sequence generation parameters, specifically introducing a 1x mode with different cyclic shift delays and orthogonal mapping matrices. This changes the fundamental parameters of the training sequence to achieve lower PAPR values while maintaining OFDM communication functionality.
Solution Approach 2:
The patent implements dynamics by making the HE-LTF sequence generation adaptive to different transmission modes (1x, 2x, 4x modes). The system dynamically selects appropriate cyclic shift delays and orthogonal mapping matrices based on the transmission bandwidth and mode, allowing optimal PAPR performance for each scenario.
2Productivity
If HE-LTF sequence is optimized for low PAPR, then system throughput improves, but sequence generation complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple orthogonal mapping matrices and cyclic shift delay values that are optimized for different transmission modes. These pre-computed parameters are stored and directly applied during transmission, avoiding complex real-time calculations and reducing generation complexity while maintaining low PAPR performance.
Solution Approach 2:
The patent segments the HE-LTF sequence generation into distinct modes (1x, 2x, 4x modes) with mode-specific parameters. Each mode has its own optimized cyclic shift delays and orthogonal mapping matrices, allowing the system to select the appropriate segment based on transmission requirements without needing to handle all cases uniformly.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An HE-LTF transmission method is provided, including: determining, based on a total number NSTS of space-time streams, a number NHELTF of OFDM symbols included in an HE-LTF field; determining a HE-LTF sequence in frequency domain according to a transmission bandwidth and a mode of the HE-LTF field, where the HE-LTF sequence in frequency domain includes but is not limited to a mode of the HE-LTF field sequence that is in a 1x mode and that is mentioned in implementations; and sending a time-domain signal according to the number NHELTF of OFDM symbols and the determined HE-LTF sequence in frequency domain. In the foregoing solution, a PAPR value is relatively low.