Variable FFT Size PPDU for Wireless LAN Spectrum Efficiency
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Solution Overview
Problem
Current wireless LAN technologies, such as IEEE 802.11n and 802.11ac, face limitations in spectrum efficiency and channel tracking, especially in high user load and interference environments, due to their fixed FFT sizes and pilot allocation methods.
Innovation Solution
The proposed method involves generating a Physical layer Protocol Data Unit (PPDU) with varying FFT sizes, where the second FFT size increases as bandwidth size increases, and the number of pilots is incremented accordingly, while maintaining pilot subcarrier spacing, to enable fair channel tracking among multiple users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed FFT size is used in legacy IEEE 802.11 specifications, then the system structure is simple and easy to implement, but spectrum efficiency and channel tracking performance deteriorate in high user load and interference environments
Solution Approach 1:
The patent applies dynamics by making the FFT size variable rather than fixed. The system dynamically selects different FFT sizes (first FFT size for legacy compatibility, second FFT size for enhanced performance) based on bandwidth conditions and user requirements, allowing the system to adapt to different operating scenarios and optimize spectrum efficiency while maintaining manageable complexity through structured selection rules
Solution Approach 2:
The patent changes the FFT size parameter from a fixed value to a variable that can take different values (first FFT size or second FFT size) depending on bandwidth and system conditions. This parameter change enables the system to achieve better spectrum efficiency in high user load environments while maintaining compatibility with legacy systems through controlled parameter variation
2Productivity
If the FFT size increases to match bandwidth size increases, then spectrum efficiency improves, but the number of pilots must be incremented which increases system complexity
Solution Approach 1:
The patent changes the FFT size parameter in relation to bandwidth size, establishing a proportional relationship where the second FFT size increases as bandwidth increases. This parameter change is coupled with corresponding adjustments to the number of pilots, creating a coordinated scaling mechanism that maintains spectrum efficiency while managing pilot allocation complexity through defined relationships
Solution Approach 2:
The patent applies local quality by differentiating pilot allocation based on specific bandwidth conditions and FFT size selections. Rather than using a uniform pilot allocation strategy, the system adjusts the number of pilots locally according to the specific operating conditions (bandwidth size, FFT size selection), optimizing performance for each local scenario while maintaining overall system coherence
3Quantity of substance
If multiple users are served in high user load environments, then system capacity increases, but channel tracking accuracy deteriorates without adaptive FFT sizes
Solution Approach 1:
The patent applies dynamics by enabling the system to dynamically adjust FFT sizes based on user load conditions and channel characteristics. This dynamic adaptation allows the system to maintain accurate channel tracking even when serving multiple users in high user load environments, as the FFT size can be optimized for each specific operational context rather than remaining fixed
Solution Approach 2:
The patent changes the FFT size parameter adaptively to maintain channel tracking accuracy across different user load conditions. By varying the FFT size according to bandwidth and system state, the system preserves measurement precision for channel estimation and tracking even when serving a larger quantity of users, preventing the deterioration that would occur with fixed parameters
Data Source
AI summary
Provided are method for transmitting a data block in a wireless LAN and an apparatus using the same. A transmitter transmits a physical layer protocol data unit (PPDU) in a transmission bandwidth. The PPDU includes a first part to which a first fast Fourier transform (FFT) size is applied and a second part to which a second FFT size is applied. The second FFT size increases by integer times as the size of the transmission bandwidth increases.