WLAN PLCP Frame Signaling for Legacy and VHT STA Coexistence

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Solution Overview

Problem

Current WLAN systems face challenges in supporting high-throughput data processing speeds, particularly in environments where legacy, HT, and VHT STAs coexist, leading to increased preamble overhead and potential malfunction of HT STAs.

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 rotated constellations and distinct CRC polynomials to ensure compatibility and reduce preamble overhead, thereby supporting SU-MIMO and MU-MIMO modes while preventing HT STA malfunction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a PLCP frame is configured to support high-throughput data processing in IEEE 802.11n WLAN systems, then data processing speed and network reliability are improved, but preamble overhead increases and HT STAs may malfunction due to coexistence with legacy STAs

Engineering Contradiction:

Improvedata processing speedVSAvoidpreamble overhead

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The PLCP frame is segmented into distinct fields: a legacy SIG field for backward compatibility and an HT-SIG field for high-throughput functionality. This segmentation allows legacy STAs to process only the legacy SIG field while HT STAs can access both fields, thereby supporting high data processing speeds without forcing all STAs to handle the complete frame structure, thus reducing effective preamble overhead.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the PLCP frame are designed with different qualities and functions. The legacy SIG field uses conventional modulation and structure for compatibility, while the HT-SIG field employs advanced modulation schemes and compressed format for high throughput. This local differentiation enables each STA type to optimize its processing according to its capabilities, improving overall system productivity without universal overhead increase.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If a PLCP frame format is designed to support both legacy and HT STAs in a coexistence environment, then adaptability is improved, but HT STAs may malfunction due to ambiguous frame identification

Engineering Contradiction:

Improvecoexistence supportVSAvoidHT STA operation

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The PLCP frame introduces asymmetric identification mechanisms: legacy STAs recognize frames through conventional SIG field structures, while HT STAs identify frames through specific patterns in the HT-SIG field such as compressed format indicators and reserved bit configurations. This asymmetric design allows HT STAs to reliably distinguish HT-formatted frames from legacy frames, preventing malfunction while maintaining coexistence adaptability.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The HT-SIG field acts as an intermediary layer between legacy and high-throughput operations. It contains specific identification patterns and control information that enable HT STAs to recognize and process frames correctly without interfering with legacy STA operations. This intermediary structure resolves the ambiguity problem by providing clear differentiation signals.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If conventional PLCP frame structures are used in IEEE 802.11n systems, then legacy STA compatibility is maintained, but system throughput is limited and cannot achieve high-speed data processing

Engineering Contradiction:

Improvelegacy compatibilityVSAvoidsystem throughput

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The PLCP frame merges conventional legacy SIG field structures with new HT-SIG field elements into a unified frame format. Legacy STAs continue to process the familiar legacy SIG portion maintaining compatibility, while HT STAs access additional HT-SIG fields that enable high-throughput operations including MIMO and advanced modulation. This merging allows the system to achieve high productivity without sacrificing legacy adaptability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The PLCP frame is designed with universal structure that serves multiple functions: the legacy SIG field ensures backward compatibility with all existing STAs, while the HT-SIG field provides enhanced functionality for HT STAs. This multi-functional design allows a single frame format to support both legacy compatibility and high-speed throughput requirements simultaneously.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11902068B2Method and apparatus for transmitting PLCP frame in wireless local area network system

Publication Date: 2024.02.13 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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.