VHT WLAN PLCP Header Layout for Legacy and HT STA Coexistence
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Solution Overview
Problem
Current WLAN systems face challenges in supporting high throughput and ensuring coexistence of legacy, HT, and VHT STAs, particularly in reducing preamble overhead and preventing malfunction of HT STAs in VHT WLAN systems.
Innovation Solution
A method for configuring a PLCP frame that includes generating a PPDU with an L-SIG field for legacy STAs and a VHT-SIG field for VHT STAs, using different CRC polynomials and constellations to ensure correct decoding and reduce preamble overhead, while preventing HT STA malfunction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a unified PLCP frame format is used for all STA types, then device complexity is reduced, but HT STAs may malfunction when receiving VHT frames
Solution Approach 1:
The patent applies local quality by making the PLCP header structure adaptable to different STA types. VHT STAs can interpret the full PLCP header including VHT-specific fields, while HT STAs can process only the legacy portion. This allows each STA type to process only the relevant portion of the frame header, preventing HT STA malfunction while maintaining a unified transmission format.
Solution Approach 2:
The PLCP header is segmented into legacy fields and VHT-specific fields. The legacy fields (L-SIG) maintain compatibility with HT STAs, while VHT-specific fields (VHT-SIG) provide enhanced functionality for VHT STAs. This segmentation allows HT STAs to process the legacy portion without being affected by VHT-specific extensions.
2Productivity
If legacy STAs use BPSK constellation and VHT STAs use rotated constellation, then VHT performance is improved, but legacy STA compatibility may be affected
Solution Approach 1:
Different constellation schemes are applied to different field portions based on the target STA type. Legacy fields use conventional BPSK that legacy STAs can decode, while VHT-specific fields use rotated constellations optimized for VHT performance. Each STA type can correctly interpret the fields intended for its category.
Solution Approach 2:
The constellation rotation parameter is changed specifically for VHT-SIG fields to achieve higher data rates for VHT STAs, while L-SIG fields maintain the original BPSK constellation. This parameter change is localized to specific fields and does not affect legacy STA compatibility.
Data Source
AI summary
A method of transmitting a Physical Layer Convergence Procedure (PLCP) frame in a Very High Throughput (VHT) Wireless Local Area Network (WLAN) system includes generating a MAC Protocol Data Unit (MPDU) to be transmitted to a destination station (STA), generating a PLCP Protocol Data Unit (PPDU) by adding a PLCP header, including an L-SIG field containing control information for a legacy STA and a VHT-SIG field containing control information for a VHT STA, to the MPDU, and transmitting the PPDU to the destination STA. A constellation applied to some of Orthogonal Frequency Division Multiplex (OFDM) symbols of the VHT-SIG field is obtained by rotating a constellation applied to an OFDM symbol of the L-SIG field.