WLAN Cyclic Postfix for Outdoor ISI Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In outdoor wireless local area network (WLAN) scenarios, severe inter-symbol interference (ISI) due to longer delay spreads hinders robust packet transmission, and existing methods fail to meet the required packet error rate (PER) even with robust modulation techniques like BPSK, necessitating a solution that ensures both robustness and backward compatibility.
Innovation Solution
A cyclic postfix is added to the information bearing section of symbols in WLAN packets, specifically in outdoor scenarios, to reduce ISI impact and ensure backward compatibility, allowing for robust packet transmission by matching the postfix length to the channel delay spread and ensuring compatibility with legacy systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a longer cyclic prefix is used to reduce inter-symbol interference in outdoor scenarios, then transmission robustness is improved, but transmission overhead increases and compatibility with legacy systems deteriorates
Solution Approach 1:
The patent segments the cyclic prefix into two parts: a legacy CP portion that maintains compatibility with existing 802.11a/g/n/ac systems, and an extended CP portion that provides additional ISI protection for outdoor scenarios. This segmentation allows different portions of the CP to serve different functions, resolving the contradiction between robustness and compatibility.
Solution Approach 2:
The patent applies preliminary action by pre-extending the cyclic prefix before signal transmission to anticipate and mitigate the expected ISI effects in outdoor scenarios. The extended CP is designed in advance based on predicted delay spread characteristics, providing proactive protection against interference before it degrades signal quality.
2Reliability
If a longer cyclic prefix is used to reduce inter-symbol interference, then packet error rate performance is improved, but backward compatibility with legacy systems deteriorates
Solution Approach 1:
The patent applies local quality by making different portions of the cyclic prefix serve different quality requirements: the legacy CP portion maintains the exact characteristics required by 802.11a/g/n/ac systems for backward compatibility, while the extended CP portion provides enhanced protection qualities for outdoor transmission. This local differentiation resolves the contradiction between improved PER performance and maintained compatibility.
Solution Approach 2:
The extended cyclic prefix structure serves multiple functions simultaneously: it maintains compatibility with legacy systems through the legacy CP portion while providing enhanced ISI protection for outdoor scenarios through the extended portion. This multi-functionality allows a single CP structure to satisfy both compatibility requirements and performance enhancement goals.
3Adaptability or versatility
If robust modulation methods like BPSK and existing CP lengths are used in outdoor scenarios, then backward compatibility is maintained, but the packet error rate requirement still cannot be met due to severe inter-symbol interference
Solution Approach 1:
The patent applies parameter changes by modifying the cyclic prefix length parameter from the standard values to an extended value specifically for outdoor scenarios. By changing the CP length parameter while maintaining the legacy portion structure, the system achieves both backward compatibility (through preserved legacy parameters) and improved PER performance (through the extended parameter).
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Embodiments of the present invention provide a wireless local area network transmission method and device, where the method includes: generating a packet, where first L time domain sequence bits of a second symbol in the packet are the same as first L time domain sequence bits of an information bearing section in a time domain sequence of a first symbol in the packet, the first symbol includes a cyclic prefix CP and the information bearing section, the second symbol is a symbol following the first symbol, a length of the CP is 16 bits, and a length of the information bearing section is 64 bits, where 1≤L≤64; and sending the packet to a receive end, so that the receive end receives and parses the packet. According to the method and the device in the embodiments of the present invention, not only backward compatibility can be ensured, but also robustness of transmission in an outdoor scenario can be strengthened to an extent.