Low Latency Preemption via Null Tones in Wi-Fi
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Solution Overview
Problem
Current IEEE 802.11 networks face challenges in supporting low-latency applications during high throughput transmissions, as they struggle to reconcile long TXOPs for high throughput traffic with the need to reduce latency, leading to reduced channel efficiency and performance impact on low-latency applications.
Innovation Solution
The implementation of a low latency preemption system using null tones or dedicated resource units for suspend request feedback, allowing for early termination of long DL PPDU transmissions and enabling low-latency packet transmission by establishing time gaps and using predefined null tones for resource requests, thereby minimizing latency without significantly impacting high throughput traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If long TXOPs are used for high throughput traffic, then channel efficiency is improved, but latency for low-latency applications increases
Solution Approach 1:
The patent segments the transmission medium by introducing dedicated resource units (RUs) within the OFDMA framework specifically for low-latency traffic. This allows the channel to be divided into different functional segments: regular RUs for high throughput traffic and dedicated RUs for low-latency traffic, enabling simultaneous operation of both traffic types without mutual interference
Solution Approach 2:
The patent implements dynamic preemption mechanisms where access points can dynamically allocate and reassign resource units based on real-time traffic conditions. The system dynamically adjusts the allocation of dedicated RUs to low-latency applications when needed, allowing flexible adaptation between maximizing throughput and minimizing latency based on current network conditions
2Loss of time
If TXOP limit is reduced to reduce latency, then low-latency performance is improved, but overall throughput decreases
Solution Approach 1:
The patent merges the advantages of both long TXOPs and short TXOPs by combining regular resource units for high throughput transmissions with dedicated resource units for low-latency transmissions within the same OFDMA frame structure. This merging allows the system to maintain long TXOPs for throughput traffic while providing short transmission opportunities for latency-sensitive traffic
Solution Approach 2:
The dedicated resource units act as an intermediary mechanism that mediates between the conflicting requirements of high throughput and low latency. These dedicated RUs provide a specialized pathway for low-latency traffic that does not interfere with the regular throughput-oriented transmissions, effectively decoupling the two performance metrics
3Loss of time
If preemption is implemented for low-latency traffic, then latency is reduced, but complexity of the system increases
Solution Approach 1:
The patent extracts the preemption functionality from the general MAC layer operations and implements it as a dedicated resource allocation mechanism at the physical layer through specific resource unit assignments. By taking out the preemption function and implementing it through dedicated RUs with specific signaling, the system reduces the complexity burden on the MAC layer while maintaining the preemption capability
Data Source
AI summary
This disclosure describes systems, methods, and devices related to low latency preemption. A device may establish time gaps between consecutive physical layer (PHY) convergence protocol data units (PPDUs) to facilitate preemption opportunity for low latency (LL) transmission. The device may detect a suspend/resource request (SR) transmitted over predefined null tones, wherein the SR is received from a station device (STA). The device may determine if a current transmit opportunity (TXOP) is preemptable and communicate this status through a control frame. The device may set a suspend request (SR) feedback report support subfield within an ultra high reliability (UHR) capabilities element based on a capability to support the SR feedback report.