Early Data Retransmission of Message 3 in LTE Random Access

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Solution Overview

Problem

Current LTE systems are unable to send uplink or downlink data before the contention-based random access procedure is completed, which limits early data transmission capabilities and increases power consumption and latency.

Innovation Solution

The introduction of dual UL grants in the random access response allows UEs to send early data during the random access procedure, with the eNB providing two UL grants for UEs capable of this feature, enabling the selection of a larger grant for early data transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If data transmission is allowed only after RRC connection setup is completed, then connection reliability is improved, but latency and power consumption increase

Engineering Contradiction:

Improveconnection reliabilityVSAvoidlatency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent enables preliminary data transmission during the random access procedure before RRC connection setup is fully completed. The eNB provides UL grants in the random access response (message 2) that allow the UE to transmit data early (message 3) without waiting for complete connection establishment, thereby reducing latency while maintaining connection reliability through proper grant management and retransmission mechanisms

Inventive Principle:

Principle #10Preliminary action

2Reliability

If data transmission is allowed only after RRC connection setup is completed, then connection reliability is improved, but power consumption increases

Engineering Contradiction:

Improveconnection reliabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If a single UL grant is provided in random access response, then device complexity is reduced, but early data transmission capability is limited

Engineering Contradiction:

Improvegrant management complexityVSAvoidearly data transmission capability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent segments the UL grant provision into multiple grants: a first UL grant for legacy LTE operation and a second UL grant for early data transmission with larger TBS. This segmentation allows the eNB to provide specialized grants for different transmission scenarios, enabling flexible early data transmission while maintaining backward compatibility and managing complexity through structured grant types

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent makes the random access response mechanism universal by enabling it to serve multiple purposes: traditional connection setup and early data transmission. The eNB can provide dual UL grants (first and second) in the same random access response, allowing the UE to perform both legacy operations and early data transmission, thereby enhancing the versatility of the existing protocol without requiring separate procedures

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Adaptability or versatility

If dual UL grants are provided for early data transmission, then early data transmission capability is improved, but retransmission complexity increases

Engineering Contradiction:

Improveearly data transmission capabilityVSAvoidretransmission management complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the retransmission management by associating separate DCIs with each UL grant. The first DCI (scrambled by TC-RNTI) manages retransmissions for the first UL grant, while the second DCI (scrambled by C-RNTI) manages retransmissions for the second UL grant. This segmentation simplifies retransmission tracking by maintaining independent control channels for each grant type, avoiding the complexity of managing mixed retransmissions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces DCI (Downlink Control Information) as an intermediary mechanism to manage retransmissions. The DCI acts as a mediator between the eNB and UE, providing controlled retransmission opportunities. By using DCI scrambled with appropriate RNTIs (TC-RNTI for first grant, C-RNTI for second grant), the system manages retransmission complexity through standardized control signaling rather than direct complex coordination

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP3665818B1Early data retransmission of message 3

Publication Date: 2025.04.09 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

According to certain embodiments, a method performed by a wireless device includes transmitting, to a base station, a first transmission of a message 3, which includes user data and information to setup or resume a connection between the wireless device and the base station. DCI comprising an uplink grant indicating a plurality of transport block sizes is received from the base station. The DCI is interpreted based on previous information received in a message 2 from the base station. One of the transport block sizes is selected for retransmission of the message 3. The message 3 is retransmitted using the selected transport block size and includes either only the information to setup or resume the connection or the information to setup or resume the connection and user data. The message 3 is retransmitted using the selected transport block size.