sPDCCH Resource Mapping for Short TTI Latency and Frequency Diversity

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Solution Overview

Problem

Existing LTE systems face challenges in efficiently mapping short physical downlink control channels (sPDCCH) for short TTI operations, leading to increased packet data latency and resource inefficiencies due to overlapping search spaces and limited resource utilization.

Innovation Solution

A method for mapping the sPDCCH to resource elements of a time-frequency grid, utilizing short resource element groups (sREGs) and short control channel elements (sCCEs) with localized or distributed configurations, supporting both CRS and DMRS-based transmissions, to achieve high frequency diversity and efficient resource allocation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If sPDCCH is mapped using traditional PDCCH methods in LTE, then legacy compatibility is maintained, but packet data latency increases and resource efficiency deteriorates

Engineering Contradiction:

Improvepacket data latencyVSAvoidresource efficiency

Core Design Contradiction:

Loss of timeVSProductivity

Solution Approach 1:

The patent segments the control channel mapping by introducing sREG (short resource element group) and sCCE (short control channel element) structures that are specifically designed for short TTI operations. This segmentation allows independent optimization of sPDCCH mapping without affecting legacy PDCCH functionality, thereby reducing packet data latency while maintaining resource efficiency through dedicated short-TTI-optimized structures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic search space configuration where the network can flexibly adjust sPDCCH candidate locations and quantities based on traffic conditions and channel state. This dynamic adaptation enables the system to optimize resource utilization in real-time, improving both latency performance and resource efficiency by allocating control channel resources only where and when needed.

Inventive Principle:

Principle #15Dynamics

2Loss of time

If sPDCCH search spaces are configured to reduce latency, then packet data latency decreases, but overlapping search spaces cause resource conflicts and efficiency loss

Engineering Contradiction:

Improvepacket data latencyVSAvoidresource efficiency

Core Design Contradiction:

Loss of timeVSLoss of energy

Solution Approach 1:

The patent applies local quality by configuring different search space parameters (such as candidate quantities, aggregation levels, and resource element group assignments) for different wireless devices or different time-frequency regions based on their specific requirements. This localized optimization prevents universal over-provisioning, reducing resource conflicts while maintaining low latency for each device according to its individual needs.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements preliminary search space configuration through RRC signaling that pre-establishes non-overlapping or minimally overlapping search spaces for multiple devices. By proactively planning and coordinating search space allocations before potential conflicts arise, the system prevents resource conflicts and efficiency loss while maintaining optimized latency performance for all configured devices.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If sPDCCH uses condensed frequency allocation, then resource utilization improves, but frequency diversity gain is reduced

Engineering Contradiction:

Improveresource utilizationVSAvoidfrequency diversity gain

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent employs a nested structure where sREGs (short resource element groups) are organized within PRBs (physical resource blocks), and multiple sREGs can be grouped to form sCCEs (short control channel elements). This nesting allows the system to achieve condensed frequency allocation at the sREG level while maintaining frequency diversity through the distributed arrangement of nested sCCEs across different PRBs, thus simultaneously improving resource utilization and preserving reliability.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent transitions from traditional two-dimensional (time-frequency) resource allocation to a three-dimensional structure by introducing the sREG-sCCE-sPDCCH hierarchy with explicit mapping relationships. This dimensional expansion allows independent optimization of frequency allocation (through sREG condensation) while maintaining frequency diversity (through distributed sCCE placement across multiple PRBs in the frequency dimension), thereby resolving the contradiction between resource utilization and reliability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS12531692B2Short physical downlink control channel (SPDCCH) mapping design

Publication Date: 2026.01.20 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method, network node and wireless device for receiving and/or mapping a physical downlink control channel, PDCCH, to resource elements of a time-frequency grid are provided in which the PDCCH is mapped to resource elements of the time-frequency grid by configuring resource element groups, REGs, each REG spanning one orthogonal frequency division multiplex, OFDM, symbol, and the PDCCH being at least two OFDM symbols. In accordance with one embodiment, the method includes receiving the PDCCH from the network node on one of a plurality of sets of physical resource blocks, PRBs.