Expanded Long Training Sequence for Wireless Networks
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Solution Overview
Problem
Legacy wireless communication devices compliant with older 802.11 standards face challenges in maintaining backward compatibility and efficient channel estimation due to limitations in the peak-to-average power ratio of existing long training sequences, which restrict their use in systems with higher throughput and newer standards.
Innovation Solution
The development of an expanded long training sequence with a minimal peak-to-average power ratio, processed using an Inverse Fourier Transform, that operates on more than 52 sub-carriers, allowing for channel impulse response and carrier frequency offset estimation without interfering with adjacent channels, and is compatible with 802.11a and 802.11g systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the long training sequence is expanded to use more than 52 sub-carriers, then the peak-to-average power ratio is reduced, but the device complexity increases
Solution Approach 1:
The training sequence is segmented across multiple sub-carriers (56 or 63 sub-carriers instead of 52), distributing the signal energy across more frequency components. This segmentation reduces the peak power on any single sub-carrier while maintaining total energy, thereby reducing the peak-to-average power ratio without requiring a complete redesign of the communication system.
Solution Approach 2:
The patent changes the parameter of sub-carrier utilization from 52 to 56 or 63 sub-carriers, expanding the frequency spectrum usage. This parameter change allows the system to maintain backward compatibility while reducing peak power density, as the same training sequence pattern is distributed across additional sub-carriers.
2Reliability
If legacy devices use the existing long training sequence, then backward compatibility is maintained, but channel estimation precision is insufficient for higher throughput systems
Solution Approach 1:
The expanded long training sequence serves multiple functions simultaneously: it maintains backward compatibility with legacy 802.11a/g devices while also enabling improved channel estimation for higher throughput systems. The same training sequence structure works across both legacy and new systems, providing universal applicability.
Solution Approach 2:
The patent adds another dimension to the training sequence by utilizing additional sub-carriers (56 or 63 instead of 52). This dimensional expansion provides more data points for channel estimation while maintaining the same time-domain sequence structure, thereby improving precision without breaking compatibility.
3Productivity
If the training sequence uses more sub-carriers, then throughput capability is improved, but interference with adjacent channels increases
Solution Approach 1:
The patent applies local quality by carefully selecting which sub-carriers to use (56 or 63 specific sub-carriers) and assigning appropriate symbols to each. The training sequence is designed with specific local characteristics at different sub-carrier positions to minimize spectral leakage and interference with adjacent channels while maximizing throughput capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The expanded long training sequence reduces power back-off and maintains orthogonality, enabling efficient communication and backward compatibility by utilizing additional sub-carriers while maintaining the same BPSK encoding, thus supporting higher throughput and compatibility with newer standards.
Implementation Method 1
an Inverse Fourier Transform for processing the expanded long training sequence from the signal generating circuit and producing an optimal expanded long training sequence with a minimal peak-to-average power ratio
Data Source
AI summary
A network device for generating an expanded long training sequence with a minimal peak-to-average ratio. The network device includes a signal generating circuit for generating the expanded long training sequence. The network device also includes an Inverse Fourier Transform for processing the expanded long training sequence from the signal generating circuit and producing an optimal expanded long training sequence with a minimal peak-to-average ratio. The expanded long training sequence and the optimal expanded long training sequence are stored on more than 52 sub-carriers.