MAC PHY Layer Feedback for Unlicensed Spectrum Access

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Solution Overview

Problem

LTE devices face performance issues in unlicensed spectra due to centralized coordination and listen-before-talk (LBT) regulations, leading to hampered uplink transmission performance compared to Wi-Fi devices, which can asynchronously access the medium.

Innovation Solution

The solution involves interaction between the MAC and PHY layers of wireless devices to determine the success of transmissions and retransmissions, allowing the MAC layer to reschedule transmissions immediately and reduce power consumption by only rescheduling when necessary, while also enabling autonomous operation in unlicensed spectra.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LTE devices use centralized coordination and LBT regulations in unlicensed spectrum, then channel access control is improved, but uplink transmission performance deteriorates

Engineering Contradiction:

Improvechannel access controlVSAvoiduplink transmission performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent segments the transmission failure handling into two distinct layers: PHY layer handles LBT failure detection and indication, while MAC layer handles retransmission scheduling decisions. This segmentation allows each layer to specialize in its function, improving overall system efficiency and resolving the contradiction between centralized control and transmission performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements a feedback mechanism where the PHY layer provides LBT failure indications to the MAC layer, which then makes informed retransmission scheduling decisions. This feedback loop enables the system to adapt to channel conditions dynamically, improving uplink performance while maintaining reliable channel access control.

Inventive Principle:

Principle #23Feedback

2Productivity

If MAC layer reschedules transmissions immediately, then throughput is improved, but power consumption increases

Engineering Contradiction:

ImprovethroughputVSAvoidpower consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The MAC layer uses feedback from the PHY layer regarding LBT success/failure to make intelligent rescheduling decisions. Instead of always rescheduling immediately, the MAC layer only initiates retransmissions when LBT failures are detected, thereby improving throughput only when necessary and reducing unnecessary power consumption.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system implements self-service by having the MAC layer autonomously decide whether to reschedule transmissions based on PHY layer feedback. This autonomous decision-making eliminates unnecessary retransmissions and associated power consumption while maintaining high throughput when channel conditions warrant it.

Inventive Principle:

Principle #25Self-service

3Productivity

If PHY layer attempts autonomous transmission in unlicensed spectrum, then access efficiency is improved, but coordination with MAC layer becomes complex

Engineering Contradiction:

Improveaccess efficiencyVSAvoidlayer coordination complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent clearly segments responsibilities: PHY layer performs autonomous LBT and transmission attempts, while MAC layer handles higher-layer scheduling and retransmission logic. This segmentation improves access efficiency while managing coordination complexity through well-defined interface protocols between layers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary feedback mechanism between PHY and MAC layers that simplifies coordination. The PHY layer provides structured LBT status indications to the MAC layer, which then makes scheduling decisions. This intermediary interface manages the complexity of autonomous transmission coordination while maintaining access efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11252783B2Systems and methods of communicating between a MAC layer and a PHY layer for transmissions

Publication Date: 2022.02.15 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A wireless device (300, 400), e.g., a wireless communication device (e.g., a UE) or a network node (e.g., an eNB) having a Medium Access Control (MAC) layer (410) and a physical (PHY) layer (430) configured to send/resend transmissions is presented herein. The MAC layer (410) sends transmissions to the PHY layer (430) for transmitting, by the PHY layer (430), to a remote wireless device (300, 400). The PHY layer (430) receives the transmission from the MAC layer (410), and attempts to send the transmission. The PHY layer (430) further indicates to the MAC layer (410) whether the attempt to send the transmission, by the PHY layer (430), was successful. Responsive to the indication, the MAC layer (410) determines whether the attempt, by the PHY layer (430), to send the transmission was successful. The MAC layer (410) then selectively indicates to the PHY layer (430) whether to attempt to resend the transmission responsive to the determination. In so doing, the solution presented herein addresses problems caused by conflicting requirements for unlicensed and licensed spectrums, thus increasing throughput and saving power.