Msg3 Repetition Control for Wireless Random Access Latency

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Solution Overview

Problem

The four-step random access channel (RACH) procedure in wireless communication systems faces inefficiencies due to bottlenecks in message 3 (msg3) communication, leading to increased latency and PDCCH overhead, especially when multiple retransmissions of msg3 are needed for successful delivery.

Innovation Solution

Implementing msg3 repetition by determining and transmitting multiple repetitions of the msg3 communication based on channel quality, transmission power, and aggregation levels, allowing the UE to implicitly indicate the number of repetitions to the base station, thereby improving msg3 communication performance and reducing initial access latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple retransmissions of msg3 are performed to ensure successful delivery, then reliability of msg3 communication is improved, but latency and PDCCH overhead increase

Engineering Contradiction:

Improvemsg3 communication reliabilityVSAvoidinitial access latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by having the UE determine and indicate the number of msg3 repetitions in advance, before the actual repetitions are transmitted. The UE calculates the required repetitions based on parameters like aggregation level of PDCCH carrying msg2, and communicates this information to the base station beforehand, allowing the base station to prepare appropriate reception resources and avoid latency caused by iterative retransmission negotiations

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by having the UE implicitly indicate the number of msg3 repetitions to the base station through parameters such as the aggregation level of the PDCCH carrying msg2. This feedback mechanism allows the base station to understand the UE's channel conditions and adjust its reception strategy accordingly, enabling reliable communication without requiring multiple rounds of retransmission requests and acknowledgments

Inventive Principle:

Principle #23Feedback

2Reliability

If multiple retransmissions of msg3 are performed to ensure successful delivery, then reliability of msg3 communication is improved, but PDCCH overhead increases

Engineering Contradiction:

Improvemsg3 communication reliabilityVSAvoidPDCCH overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The base station determines the number of msg3 repetitions in advance based on the aggregation level of the PDCCH carrying msg2 and other parameters, and configures the appropriate number of repetitions before msg3 transmission begins. This preliminary configuration eliminates the need for multiple PDCCH transmissions to coordinate retransmissions, thereby reducing PDCCH overhead while ensuring reliable msg3 delivery

Inventive Principle:

Principle #10Preliminary action

3Reliability

If msg3 repetition is implemented with implicit indication of repetition number, then msg3 communication performance is improved, but device complexity increases

Engineering Contradiction:

Improvemsg3 communication performanceVSAvoidUE and base station processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The UE autonomously determines the number of msg3 repetitions based on parameters it can observe, such as the aggregation level of the PDCCH carrying msg2. The UE uses its own measurements and calculations to self-determine the repetition count and indicates this to the base station, eliminating the need for complex centralized scheduling and reducing overall system complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent changes the parameter used for repetition indication from explicit higher-layer signaling to implicit physical-layer parameters such as the aggregation level of PDCCH. By mapping the repetition number to an existing parameter (aggregation level) that already varies based on channel conditions, the patent avoids adding new complex signaling mechanisms while still conveying the necessary repetition information

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11678380B2Repetition of a message 3 communication of a four-step random access channel procedure

Publication Date: 2023.06.13 QUALCOMM INC

AI summary

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may determine a number of repetitions of a message 3 (msg3) communication of a four-step random access channel (RACH) procedure that are to be transmitted to a base station. The UE may transmit, to the base station, the repetitions of the msg3 communication based at least in part on determining the number of the repetitions of the msg3 communication. Numerous other aspects are provided.