Dual Subcarrier Modulation for HE WLAN Interference
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Solution Overview
Problem
High Efficiency Wireless Local Area Network (HE WLAN) systems face challenges with narrow band interferences and require a more robust modulation scheme to enhance reliability and extend range, especially in outdoor scenarios, as existing modulation schemes are inefficient under high-density deployments and suffer from poor performance in Multi-User transmissions.
Innovation Solution
Dual Subcarrier Modulation (DCM) is introduced, which transmits the same information on two subcarriers separated in frequency, providing frequency diversity and a simple indication scheme to handle narrow band interferences, and is implemented in HE WLAN systems to improve reliability and data transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If narrow band uplink OFDMA signal is used to enhance user experience by assigning subsets of subcarriers to different users, then data transmission efficiency is improved, but the signal becomes hard to be detected by CCA and experiences higher interferences on subcarriers
Solution Approach 1:
The patent segments the uplink OFDMA signal into multiple subcarriers and applies different processing to each subcarrier. Specifically, it divides the subcarriers into reference signal subcarriers and data subcarriers, and further segments data subcarriers into those affected by narrowband interference and those that are not, allowing selective handling of interference-affected portions while maintaining overall transmission efficiency.
Solution Approach 2:
The patent applies local quality by using different estimation and cancellation strategies for different subcarriers based on their interference conditions. Reference signal subcarriers use one estimation approach while data subcarriers use another, and within data subcarriers, those with narrowband interference receive specialized interference cancellation processing while others use standard processing.
2Speed
If HE-SIG-B is encoded using 1x symbol duration to maintain timing synchronization, then synchronization is maintained, but its performance is worse than data symbol with 4x symbol duration
Solution Approach 1:
The patent merges the advantages of different symbol durations by combining the timing synchronization benefits of 1x symbol duration with the improved reliability of longer symbol durations. It achieves this by using 1x symbol duration for HE-SIG-B encoding to maintain synchronization while introducing mechanisms to enhance reliability through improved modulation and coding schemes, and by using reference signals with extended processing to compensate for the shorter duration.
3Adaptability or versatility
If existing modulation schemes are used in HE WLAN to maintain compatibility with IEEE 802.11 standards, then standard compatibility is maintained, but performance is poor under narrow band interferences and in outdoor scenarios
Solution Approach 1:
The patent creates a composite modulation scheme that combines existing IEEE 802.11 standardized modulation techniques with new interference mitigation methods. It composite standard-compliant modulation (QPSK, 16-QAM, 64-QAM) with advanced interference cancellation algorithms and adaptive resource allocation, maintaining compatibility while significantly improving performance under narrowband interference and outdoor conditions.
4Reliability
If dual subcarrier modulation is applied to transmit the same information on two subcarriers separated in frequency, then frequency diversity is introduced and reliability is enhanced, but device complexity increases
Solution Approach 1:
The patent extracts the essential function of dual subcarrier modulation (frequency diversity) and separates it from the full complexity of implementing complete DCM for all signals. It selectively applies dual subcarrier techniques only where needed - specifically for reference signals and in portions of data affected by narrowband interference - while using standard single-carrier processing elsewhere, thus achieving reliability enhancement with minimal added complexity.
Data Source
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AI summary
Modulation schemes that use dual sub-carrier to reliably transmit physical layer related signaling information and/or data in high efficiency (HE) wireless local area network (WLAN) are proposed. The proposed schemes can be implemented with low complexity and provide better performance than existing modulation schemes used in WLAN that are based on IEEE 802.11/a/b/g/n/ac standards. The proposed schemes enhance the reliability of transmissions, especially under narrow band interferences. In accordance with a novel aspect, dual subcarrier modulation (DCM) is introduced in HE WLAN. DCM can introduce frequency diversity into OFDM systems by transmitting the same information on two subcarriers separated in frequency. A DCM indication scheme is used such that both encoding and decoding of DCM is really simple.