TXOP Preemption for Latency-Sensitive WLAN Traffic
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Solution Overview
Problem
In wireless local area networks (WLANs), latency-sensitive traffic often experiences delays due to the need for non-latency-sensitive traffic to complete its transmission before allowing latency-sensitive traffic to access the channel, leading to inefficiencies and increased latency.
Innovation Solution
Implementing a method where an access point (AP) can preempt the transmission opportunity (TXOP) to transmit latency-sensitive frames by sending preemption information frames, such as BlockAck or QoS Null frames with HE-Control subfields, allowing for immediate transmission of latency-sensitive data within the ongoing TXOP, and subsequently releasing the TXOP to resume non-latency-sensitive traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If non-latency-sensitive traffic is allowed to complete transmission before latency-sensitive traffic accesses the channel, then transmission completeness is ensured, but latency increases
Solution Approach 1:
The patent implements dynamic TXOP preemption by allowing the AP to interrupt an ongoing TXOP allocation to a first STA when latency-sensitive traffic is detected. The AP sends a preemption indication frame to the first STA, which then suspends its transmission. This dynamic adjustment enables the system to adapt transmission opportunities in real-time based on traffic priority, resolving the contradiction between ensuring transmission completeness and reducing latency.
Solution Approach 2:
The patent uses preliminary action by having the AP send a preemption indication frame before the first STA completes its TXOP. This advance notification allows the second STA to prepare for immediate transmission of latency-sensitive traffic. The preemption indication frame includes necessary control information that enables the second STA to start transmission without waiting for the first STA to finish, thus reducing latency while maintaining system coordination.
2Speed
If TXOP preemption is implemented to reduce latency, then latency-sensitive traffic transmission speed improves, but system complexity increases
Solution Approach 1:
The patent employs universality by using existing WLAN frame structures and mechanisms for TXOP preemption. The preemption indication is conveyed through standard frame types (such as CTS or other control frames) that are already part of the WLAN protocol suite. This approach allows the system to achieve latency reduction without requiring entirely new frame formats or protocols, thereby limiting the increase in system complexity while still enabling fast preemption functionality.
3Loss of time
If the AP sends preemption information frames to suspend ongoing transmissions, then latency-sensitive traffic can be transmitted immediately, but communication overhead increases
Solution Approach 1:
The patent applies local quality by sending preemption indication frames only when and where needed - specifically, only when latency-sensitive traffic is detected and only to the STA currently holding the TXOP. This targeted approach means that preemption frames are not transmitted continuously or broadcast to all STAs, but only locally to the specific STA that needs to be preempted. This reduces unnecessary communication overhead while still achieving immediate transmission of latency-sensitive traffic when required.
Data Source
AI summary
One example discloses a method of preemption for latency-sensitive traffic for communications between WLAN (wireless local area network) devices, including: receiving, by an access point (AP), a first frame from a first non-access point station (non-AP STA); transmitting, by the AP, a second frame indicating Transmission Opportunity (TXOP) pre-emption information to the first non-AP STA; and transmitting, to a second non-AP STA, a third frame; wherein the third frame includes latency-sensitive frame.