Contention-Based Scheduling Request Using DM-RS for Low Latency

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Solution Overview

Problem

Current methods for scheduling requests in 3GPP LTE systems, such as using the physical uplink control channel (PUCCH) or physical random access channel (PRACH), result in relatively large delays, increasing latency in communication systems, which is a challenge for mission-critical Machine Type Communication (MTC) and 5G wireless technology.

Innovation Solution

Implementing a contention-based scheduling request (SR) transmission mechanism that utilizes DeModulation Reference Signals (DM-RS) randomly selected from configured sequences, allowing user equipment (UE) to transmit SR messages with buffer status reports and UE identification information on dedicated resources, reducing latency by simplifying the SR transmission process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If scheduling request is transmitted using PUCCH or PRACH, then the SR can be transmitted through established channels, but the transmission delay increases and latency is reduced

Engineering Contradiction:

ImproveSR transmission reliabilityVSAvoidSR transmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The SR transmission is segmented into two parts: a DM-RS sequence for resource indication and a separate SR message for data. This allows the eNB to quickly identify the SR through DM-RS detection and then process the full message, reducing overall latency while maintaining reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The DM-RS sequence is transmitted first as a preliminary action to indicate resource allocation before the full SR message is sent. This preliminary indication allows the eNB to prepare for incoming SR data, reducing processing delay and improving response time

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If traditional SR transmission methods are used, then channel protocols are followed, but the number of messages increases and latency increases

Engineering Contradiction:

Improveprotocol complianceVSAvoidSR transmission efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The DM-RS sequence and SR resource indication are merged into a single transmission element. The DM-RS serves dual purposes as both a reference signal for channel estimation and an indicator of SR resource allocation, reducing the number of separate messages needed

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The DM-RS sequence is designed to serve multiple functions: channel estimation, resource indication, and SR triggering. This multi-functionality reduces the overhead of separate signaling messages while maintaining protocol compatibility

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10555322B2Low latency contention based scheduling request

Publication Date: 2020.02.04 APPLE INC

AI summary

Technology for decreasing latency for contention based scheduling request (SR) transmission is disclosed. A user equipment (UE) can process, for transmission to an enhanced node B (eNB), a DeModulation Reference Signal (DM-RS) that is randomly selected from a set of configured DM-RS sequences or configured by the eNB. The UE can select an SR transmission resource as a function of a DM-RS sequence index or cell identification (ID) based on a predefined mapping rule. The UE can process, for transmission to the eNB, a SR message having a buffer status report (BSR) and UE identification (UE-ID) information on the selected SR transmission resource.