Adaptive Contention Window Size for LAA Wi-Fi Coexistence

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Solution Overview

Problem

Existing License Assisted Access (LAA) systems face challenges in coexisting with Wi-Fi in unlicensed 5 GHz spectrum due to limitations in random backoff contention window size protocols, which are not suitable for handling multiple HARQ feedbacks and large numbers of contending devices, leading to potential collisions and interference.

Innovation Solution

A method and device for determining and adapting the random backoff contention window size based on one or more HARQ feedback values, allowing fair coexistence between LAA and Wi-Fi by modifying the contention window size using HARQ feedbacks and accounting for potential delays in HARQ feedback availability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a fixed random backoff contention window size protocol is used, then the system is simple to implement, but it leads to collisions and interference when multiple devices contend for channel access in unlicensed spectrum

Engineering Contradiction:

Improvesimplicity of implementationVSAvoidcollision avoidance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies dynamics by making the contention window size adaptive rather than fixed. The system dynamically adjusts the contention window size based on channel conditions and HARQ feedback, allowing the protocol to respond to changing network environments while maintaining manageable complexity through structured adaptation rules

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements feedback mechanisms by using HARQ (Hybrid Automatic Repeat Request) feedback to adjust the contention window size. The system monitors channel access outcomes and uses this feedback information to adaptively modify the backoff parameters, improving collision avoidance while maintaining implementation feasibility through standardized feedback processing

Inventive Principle:

Principle #23Feedback

2Reliability

If the contention window size is increased to reduce collisions, then collision avoidance improves, but the channel access delay increases

Engineering Contradiction:

Improvecollision avoidanceVSAvoidchannel access delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system dynamically adjusts the contention window size based on real-time channel conditions and HARQ feedback rather than using a consistently large window. This allows the system to achieve collision avoidance when needed while minimizing access delay during favorable conditions, resolving the trade-off between reliability and time loss

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the contention window parameter adaptively based on system state. By modifying the window size parameter in response to HARQ feedback and channel conditions, the system achieves collision avoidance when necessary while reducing the parameter value to minimize delay when the channel is favorable

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the system adapts contention window size based on multiple HARQ feedbacks, then coexistence with Wi-Fi improves, but the device complexity increases

Engineering Contradiction:

Improvecoexistence capabilityVSAvoidprotocol complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent manages complexity by systematically changing parameters (contention window size) based on HARQ feedback. The adaptation follows structured rules that process multiple feedbacks in an organized manner, achieving improved coexistence with Wi-Fi while keeping implementation complexity manageable through standardized procedures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system achieves multi-functionality by using the same HARQ feedback mechanism for both error correction and contention window adaptation. This universal approach to feedback processing improves coexistence capability while avoiding the need for separate complex protocols, thereby managing device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Adaptability or versatility

If LAA operates in unlicensed spectrum with Listen-Before-Talk, then spectrum sharing is enabled, but throughput is reduced due to channel access delays

Engineering Contradiction:

Improvespectrum sharing capabilityVSAvoidthroughput

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The system dynamically optimizes the contention window size to balance spectrum sharing requirements with throughput performance. By adapting the backoff parameters based on channel conditions and HARQ feedback, the system enables fair spectrum sharing while minimizing access delays that would otherwise reduce throughput

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12041666B2Communication device and a method therein for determining a contention window size in a communication network

Publication Date: 2024.07.16 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The disclosed embodiments relate to a method performed by an apparatus and also relate to an apparatus. The method includes transmitting to a communication device a burst including a subframe; receiving from the communication device a HARQ values associated with the subframe; and determining a random backoff contention window size based on the received HARQ values and also based on previously unused HARQ feedbacks. The apparatus is configured to perform the method steps described above.