ePDCCH Search Space Segmentation for Wide Coverage IoT

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Solution Overview

Problem

Current LTE systems face challenges in providing wideband coverage enhancement (WCE) for IoT devices operating in unlicensed spectrum, particularly in deep indoor environments, where existing solutions struggle with blind detection and link quality issues.

Innovation Solution

The proposed solution involves enhancing the ePDCCH configuration for IoT devices, including UE-specific search space design, candidate search spaces, and DCI format optimization to support UESS and CSS, which involves configuring parameters such as subframe patterns, resource block assignments, and repetition levels to ensure reliable data transmission and coverage enhancement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If blind detection is increased to improve coverage for deep indoor UEs, then coverage enhancement is improved, but UE complexity increases

Engineering Contradiction:

Improvecoverage enhancementVSAvoidUE complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The search space is segmented into two distinct types: common search space (CSS) for system information and control commands, and UE-specific search space (USS) for dedicated control information. This segmentation allows the UE to limit blind detection in CSS while focusing efforts in USS, reducing overall complexity while maintaining coverage enhancement capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent configures search space parameters (aggregation levels, candidate positions, DCI formats) in advance through RRC signaling before the UE needs to perform blind detection. This preliminary configuration reduces the real-time computational burden on the UE by pre-establishing the search patterns and parameters, thereby reducing complexity while ensuring reliable detection.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If ePDCCH performance is enhanced to serve edge of coverage UEs, then link quality is improved, but blind detection overhead increases

Engineering Contradiction:

Improvelink qualityVSAvoidblind detection overhead

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Different aggregation levels (L=1, 2, 4, 8, 16) are assigned to different search space candidates based on their specific link quality requirements. Edge of coverage UEs receive higher aggregation levels with more redundant bits for better error protection, while UEs with better link quality use lower aggregation levels, optimizing the balance between link quality and detection overhead.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs repetition of ePDCCH across multiple subframes with different aggregation levels. Instead of using maximum repetition for all UEs, the system applies partial repetition based on UE-specific path loss and channel conditions, reducing overall blind detection overhead while maintaining sufficient link quality for edge UEs.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11026215B2UE specific search space and a common search space in a wide coverage enhancement

Publication Date: 2021.06.01 APPLE INC

AI summary

This disclosure relates to implementations to support UE-specific search space (UESS) for wide coverage enhancement (WCE). One implementation relates to an apparatus of a user equipment (UE) comprising: an interface configured to receive configuration information of a UE specific Search Space (UESS) and a common search space (CSS) for enhanced Physical Downlink Control Channel (ePDCCH) from a radio-frequency (RF) circuitry; and a processor configured to monitor the UESS and the CSS for ePDCCH transmission; wherein the interface and/or the processor is adaptable to support a wideband coverage enhancement (WCE).