Partial Subframe (E)PDCCH Transmission in LAA

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Solution Overview

Problem

In Licensed Assisted Access (LAA) technology, the conventional Pcell-aligned transmission restriction leads to wasted time intervals in downlink burst transmissions, as the existing Release-12 LTE mechanism assumes Pcell-aligned transmission on the Scell, limiting the utilization of the interval between the end of Listen-Before-Talk (LBT) and the Pcell subframe boundary.

Innovation Solution

The implementation of partial subframes within the LAA DL burst transmission allows for flexible starting positions of (E)PDCCH transmission, enabling immediate reservation of the channel after LBT completion, thereby optimizing data transmission by utilizing partial subframes that are not necessarily aligned with the Pcell boundary, and remapping PDCCH or EPDCCH messages to available resource elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If Pcell-aligned transmission restriction is enforced, then timing relationship for DL burst transmission is maintained, but time interval between end of LBT and Pcell subframe boundary is wasted

Engineering Contradiction:

Improvetime interval between end of LBT and Pcell subframe boundaryVSAvoidflexibility in starting position of (E)PDCCH transmission

Core Design Contradiction:

Loss of timeVSAdaptability or versatility

Solution Approach 1:

The subframe is segmented into a partial subframe containing only the necessary OFDM symbols for (E)PDCCH transmission. This allows the transmission to start at any position within the subframe rather than being constrained to Pcell alignment, thereby utilizing the time interval between LBT completion and the next Pcell boundary without requiring full subframe alignment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The starting position of (E)PDCCH transmission is made dynamic rather than fixed to Pcell boundaries. The system can adaptively determine the optimal starting position based on LBT completion time, enabling flexible utilization of available time resources while maintaining proper timing relationships through dynamic adjustment of partial subframe parameters.

Inventive Principle:

Principle #15Dynamics

2Device complexity

If starting positions are limited to certain OFDM symbol positions, then UE blind detection complexity is reduced, but eNB scheduling flexibility is constrained

Engineering Contradiction:

ImproveUE blind detection complexityVSAvoideNB scheduling flexibility

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

Different parts of the system have different requirements satisfied: UE benefits from limited blind detection positions (first 1-4 symbols) while eNB maintains scheduling flexibility through dynamic partial subframe configuration. The local quality of control channel placement is optimized for UE simplicity while the overall system maintains adaptability through flexible partial subframe management.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The partial subframe structure acts as an intermediary that reconciles the conflicting requirements. It provides a standardized format with defined starting positions for UE detection while allowing eNB to dynamically select which partial subframe configuration to use based on scheduling needs, thus mediating between UE complexity reduction and eNB flexibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If partial subframes are used for immediate transmission after LBT, then channel utilization is improved, but Pcell timing alignment is compromised

Engineering Contradiction:

Improvechannel utilizationVSAvoidPcell timing alignment

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

Instead of requiring full subframe alignment with Pcell, the system uses partial subframes containing only the necessary portion (1-14 OFDM symbols) for immediate transmission after LBT. This partial action approach allows channel utilization improvement while maintaining sufficient timing relationship through the preserved Pcell alignment reference for the partial subframe structure.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11140712B2Transmission of (E)PDCCH within partial subframe in licensed assisted access (LAA)

Publication Date: 2021.10.05 APPLE INC

AI summary

Techniques for transmission of a physical downlink control channel (PDCCH) or enhanced PDCCH (EPDCCH) within a partial subframe of a license assisted access (LAA) burst are discussed. One example apparatus comprises a processor configured to generate a LAA burst; generate one or more downlink control channel messages that comprise at least one of PDCCH messages or EPDCCH messages; generate a physical layer encoding of the LAA burst comprising a first partial subframe, wherein the first partial subframe comprises a physical layer encoding of the one or more downlink control channel messages; and output the first partial subframe comprising the physical layer encoding of the one or more control channel messages to transmitter circuitry for subsequent transmission via an unlicensed carrier.