Predictable-Latency Access Category for Wireless Medium Contention

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Solution Overview

Problem

Current wireless communication systems face challenges in predicting latency and throughput, particularly in Ultra High Reliability (UHR) scenarios, due to limitations in existing Enhanced Distributed Channel Access (EDCA) mechanisms, which can lead to long latency tails and collisions, especially when dealing with high-priority traffic.

Innovation Solution

A high-priority contention mechanism is introduced, which includes a Predictable-Latency Access Category (AC_PL) with aggressive parameters, allowing STAs to transmit a reservation signal and contend the wireless medium based on a predefined time duration after the start of a contention period, using a shorter contention slot and specific MAC frame formats to prioritize high-priority traffic and reduce collisions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If EDCA mechanisms are used for wireless medium access, then devices can obtain Transmit Opportunity for data transmission, but latency becomes unpredictable and collisions increase especially for high-priority traffic

Engineering Contradiction:

Improvepredictability of latencyVSAvoidlatency tail

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the wireless medium access into two distinct mechanisms: standard EDCA for general traffic and the new Predictable Latency Access (PLA) mechanism for high-priority time-sensitive traffic. This segmentation allows high-priority packets to use a dedicated access method with predictable latency characteristics, while other traffic continues to use EDCA, thus resolving the contradiction between maintaining overall system compatibility and achieving predictable latency for critical traffic.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by creating a specialized access mechanism (PLA) with specific parameters optimized for high-priority traffic, rather than applying a uniform EDCA mechanism to all traffic types. The PLA mechanism uses different contention parameters, including a predefined time duration from contention period start, specifically tailored for time-sensitive packets, thereby achieving predictable latency where needed without affecting other traffic.

Inventive Principle:

Principle #3Local quality

2Productivity

If standard EDCA parameters are used, then general wireless communication is maintained, but high-priority traffic experiences long latency tails and collisions

Engineering Contradiction:

Improvethroughput for high-priority trafficVSAvoidlatency for high-priority packets

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent implements preliminary action by having high-priority STAs transmit a reservation signal at a predefined time duration after the start of the contention period, before the actual data transmission. This reservation signal reserves the wireless medium in advance for high-priority traffic, preventing collisions and reducing latency by securing channel access beforehand, thus improving both throughput and latency for high-priority packets.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies preliminary anti-action by using the reservation signal to preemptively prevent other STAs from accessing the channel during the high-priority transmission window. This counteracts the potential harmful effect of collisions before they can occur, ensuring that high-priority traffic achieves predictable throughput and latency by blocking competing traffic in advance.

Inventive Principle:

Principle #9Preliminary anti-action

3Productivity

If multiple STAs use high-priority AC simultaneously, then channel utilization increases, but collisions increase without proper coordination

Engineering Contradiction:

Improvechannel utilizationVSAvoidcollision avoidance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements periodic action by organizing channel access around contention periods with a structured timeline: a predefined time duration after the start of the contention period for reservation signals, followed by a PLA contention window for high-priority data transmission. This periodic structure with defined phases allows multiple STAs to coordinate their access systematically, increasing channel utilization while maintaining reliability through predictable access patterns that reduce random collisions.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS20230328790A1Apparatus, system, and method of contending a wireless medium

Publication Date: 2023.10.12 INTEL CORP

AI summary

For example, a wireless communication station (STA) may be configured toto transmit a reservation signal over a wireless medium at a reservation signal transmission time, for example, based on a determination that high-priority data of a high-priority Access Category (AC) is queued at the STA. For example, the reservation signal transmission time may be based on an end of a predefined time duration from a start of a contention period. For example, the reservation signal may be configured to indicate a busy Clear Channel Assessment (CCA) to a receiving STA. For example, the STA may be configured to contend the wireless medium according to a high-priority contention policy, for example, after transmission of the reservation signal, to obtain a Transmit Opportunity (TxOP) for transmission of the high-priority data.