Extended Random Access Response Window in 5G NR

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Solution Overview

Problem

The existing RA-RNTI calculation formula in 5G NR is limited to a duration of 10ms, making it challenging to extend the random access response window beyond this duration without exhausting the RNTI space, especially in scenarios requiring extended contention resolution timers.

Innovation Solution

The proposed solution involves indicating the applicable random access channel occasion within a span of one or multiple radio frames using the least significant bits of the system frame number or an index offset in the DCI or RAR/MsgB, allowing the same RA-RNTI to be used across multiple frames without extending the RA-RNTI space.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of moving object

If the random access response window is extended beyond 10ms, then the contention resolution capability is improved, but the RA-RNTI space is exhausted

Engineering Contradiction:

Improverandom access response window durationVSAvoidRA-RNTI space

Core Design Contradiction:

Duration of action of moving objectVSQuantity of substance

Solution Approach 1:

The random access response window is segmented into multiple 10ms intervals, each identified by an interval index. The RA-RNTI calculation is segmented to include this interval index, allowing the same base RA-RNTI to be reused across different intervals while maintaining uniqueness through the interval differentiation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The RA-RNTI calculation parameters are changed to include the interval index as an additional dimension. This transforms the RA-RNTI from a simple identifier into a composite identifier that incorporates temporal information, enabling extended window duration without exhausting the identifier space.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the contention resolution timer is extended, then the reliability of random access is improved, but the system complexity increases

Engineering Contradiction:

Improverandom access contention resolution reliabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system dynamically adapts the contention resolution timer duration based on network conditions and configuration. The extended timer allows for flexible adjustment of the random access response window, enabling the system to optimize reliability without permanent structural complexity increases.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP3759993B1Receiving random access response with extended response window

Publication Date: 2026.01.28 NOKIA TECHNOLOGIES OY

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AI summary

Method, apparatuses, and computer program product for addressing random access responses with extended response windows. One method may include accessing, by a user equipment, a network by sending a random access channel preamble to a network element. The method may also include receiving, in response to the random access channel preamble, a random access response from the network element. The random access response provides an indication of which random access channel occasion in time within a span of one or a plurality of radio frames the random access response applies.