Resource Unit Null Subcarriers Mitigate Interference in WLANs
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Solution Overview
Problem
Next-generation wireless local area networks (WLANs) face challenges in improving spectrum efficiency and area throughput, especially in dense environments with multiple access points and stations, and outdoor settings, where interference and high user loads are prevalent, limiting the effectiveness of existing resource unit allocation methods.
Innovation Solution
The proposed method involves allocating resource units with adequately positioned null subcarriers and varying resource unit sizes to mitigate interference, allowing for efficient use of bandwidth across multiple stations, using techniques like OFDMA and MU-MIMO, and dynamically allocating resource units and leftover tones to optimize communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple resource units are allocated to multiple receiving stations in dense environments, then spectrum efficiency and area throughput are improved, but interference between resource units increases
Solution Approach 1:
The patent introduces null subcarriers as intermediary elements between resource units. These null subcarriers act as mediators that reduce interference between adjacent resource units while allowing multiple resource units to be allocated to multiple receiving stations, thereby maintaining improved spectrum efficiency and area throughput in dense environments.
Solution Approach 2:
The patent applies local quality by strategically positioning null subcarriers at specific locations between resource units rather than uniformly across the spectrum. This localized approach reduces interference precisely where it occurs between resource units while preserving the overall spectrum efficiency gains from multi-user allocation.
2Productivity
If multiple resource units are allocated to multiple receiving stations, then area throughput is improved, but interference mitigation becomes more difficult
Solution Approach 1:
Null subcarriers serve as intermediary elements that facilitate interference mitigation in multi-resource unit allocations. By inserting these null subcarriers between resource units allocated to different receiving stations, the system maintains improved area throughput while reliably reducing interference through the mediating presence of these null subcarriers.
Solution Approach 2:
The patent segments the frequency spectrum into distinct resource units separated by null subcarriers. This segmentation allows multiple resource units to be allocated to multiple receiving stations for improved area throughput, while the null subcarriers create clear boundaries that simplify interference mitigation between the segmented resource units.
3Object-affected harmful factors
If resource units are adequately positioned with null subcarriers, then interference is reduced, but resource utilization efficiency may decrease
Solution Approach 1:
The patent applies local quality by positioning null subcarriers only at specific critical locations between resource units where interference occurs, rather than inserting null subcarriers throughout the entire spectrum. This localized approach reduces interference effectively while minimizing the impact on resource utilization efficiency by preserving contiguous resource unit allocations where possible.
Solution Approach 2:
The patent employs partial action by selectively inserting null subcarriers only where necessary to mitigate interference between specific resource units, rather than uniformly inserting null subcarriers across all resource unit boundaries. This partial approach reduces interference in critical areas while maintaining higher resource utilization efficiency in areas where interference is less severe.
Data Source
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AI summary
The present specification presents a technique for transmitting a PPDU by using a resource unit including carriers of different sizes. For example, a PPDU is transmitted by using five frequency bands, a left guard band, and a right guard band. Null subcarriers can be included in the five frequency bands according to the type of included resource unit. The null subcarriers can be the leftmost side or the rightmost side of each frequency band, and the number of included null subcarriers can be determined according to the size of the carrier included in each resource unit or the type of resource unit. A frequency band including DC carriers can include only one resource unit having a discontinuous carrier, and null subcarriers can be further included around the DC carriers.