MU-MIMO Collision Detection and Dynamic Backoff Window Adaptation

Solution Overview

Problem

In wireless communications, especially in MU-MIMO transmissions, existing systems face challenges in detecting collisions and adapting the backoff window size effectively, leading to inefficiencies in data transmission and potential network congestion.

Innovation Solution

The method involves simultaneously transmitting packets to multiple apparatuses, determining missing acknowledgments, and increasing the contention window for a backoff counter based on the detection of collisions, allowing for adaptive adjustment of the backoff window to prevent subsequent collisions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the backoff window size is kept small to maintain high transmission opportunities, then transmission efficiency is improved, but collision probability increases

Engineering Contradiction:

Improvetransmission efficiencyVSAvoidcollision probability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The backoff window size is made dynamic rather than fixed. The contention window (CW) is adapted based on collision detection results from MU-MIMO transmissions. When collisions are detected through missing acknowledgments, the CW is increased to reduce collision probability; when no collisions occur, the CW can be decreased to improve transmission efficiency. This dynamic adjustment resolves the contradiction between maintaining high transmission opportunities and reducing collision probability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system implements feedback mechanisms by monitoring acknowledgment messages from receiving apparatuses. When acknowledgments are missing or indicate collision, this feedback triggers an increase in the backoff window size. This feedback loop enables the system to learn from past transmission outcomes and adjust the backoff window accordingly, balancing transmission efficiency and collision avoidance.

Inventive Principle:

Principle #23Feedback

2Reliability

If the backoff window size is increased to reduce collision probability, then transmission reliability is improved, but transmission efficiency deteriorates

Engineering Contradiction:

Improvecollision avoidanceVSAvoidtransmission efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The backoff window size is made dynamic rather than fixed. The contention window (CW) is adapted based on collision detection results from MU-MIMO transmissions. When collisions are detected through missing acknowledgments, the CW is increased to reduce collision probability; when no collisions occur, the CW can be decreased to improve transmission efficiency. This dynamic adjustment resolves the contradiction between maintaining high transmission opportunities and reducing collision probability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system implements feedback mechanisms by monitoring acknowledgment messages from receiving apparatuses. When acknowledgments are missing or indicate collision, this feedback triggers an increase in the backoff window size. This feedback loop enables the system to learn from past transmission outcomes and adjust the backoff window accordingly, balancing transmission efficiency and collision avoidance.

Inventive Principle:

Principle #23Feedback

3Reliability

If collision detection mechanisms are enhanced to accurately identify collisions, then transmission reliability is improved, but system complexity increases

Engineering Contradiction:

Improvecollision detection accuracyVSAvoiddetection mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The receiving apparatuses themselves provide collision detection information by sending back acknowledgment messages. The transmitting apparatus detects collisions by monitoring the presence or absence of these acknowledgments, rather than implementing a separate complex detection system. This self-service approach improves collision detection accuracy while avoiding additional system complexity.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Acknowledgment messages serve as an intermediary mechanism for collision detection. Instead of directly detecting collisions through complex signal analysis, the system uses acknowledgment messages as a mediator to convey transmission status. This intermediary approach simplifies the detection mechanism while maintaining high reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP2747509B1Collision detection and backoff window adaptation for multiuser mimo transmission

Publication Date: 2019.05.01 QUALCOMM INC

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AI summary

Certain aspects of the present disclosure generally apply to a wireless local area network (WLAN) where an access point (AP) has data to send to multiple stations (STAs). By using the Downlink Spatial Division Multiple Access (DL-SDMA) technique, the AP may send data at the same time towards multiple STAs. Certain aspects of the present disclosure provide techniques and apparatuses for detecting that a multiuser multiple-input multiple-output (MU-MIMO) transmission has suffered a collision and to adapting a contention window (CW) size for a backoff counter applied to a subsequent MU-MIMO transmission.