SSB-Preamble Mapping for Contention-Free Random Access

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Solution Overview

Problem

In New Radio (NR) wireless communication systems, the existing random access procedures face challenges due to the complexity of managing multiple synchronization signal blocks (SSBs) and PRACH resources, which can lead to increased overhead in PDCCH orders and potential collisions during contention-free random access.

Innovation Solution

The solution involves signaling a set of dedicated preambles and PRACH resources mapped to different SSBs, allowing user equipment (UE) to select the appropriate preamble sequence based on the received PDCCH order or RRC message, enabling contention-free random access by associating each SSB with unique PRACH resources and minimizing the size of the PDCCH order.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple SSBs are supported with dedicated preambles, then contention-free random access reliability is improved, but PDCCH order size and signaling overhead increase

Engineering Contradiction:

Improvecontention-free random access reliabilityVSAvoidPDCCH order overhead

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent segments the preamble selection process by dividing preambles into multiple groups, where each group is associated with a specific SSB. The PDCCH order only needs to indicate which group to use rather than specifying a single preamble, reducing signaling overhead while maintaining the ability to support multiple SSBs for contention-free random access

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary association between preamble groups and SSBs through RRC configuration before the random access procedure. This pre-establishes the mapping relationships, allowing the PDCCH order to simply trigger the appropriate group without needing to convey detailed SSB-preamble mapping information, thereby reducing overhead

Inventive Principle:

Principle #10Preliminary action

2Reliability

If multiple SSBs are supported with unique PRACH resources, then collision prevention is improved, but device complexity and resource management complexity increase

Engineering Contradiction:

Improvecollision preventionVSAvoidresource management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments PRACH resources into multiple groups, with each group associated with a specific SSB. This segmentation allows UEs to automatically select the appropriate PRACH group based on the SSB they measured, preventing collisions without requiring complex centralized resource management, as the mapping is pre-configured and distributed

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by associating specific PRACH resources with specific SSBs based on local measurement conditions. Each UE selects PRACH resources locally based on which SSB it measured best, rather than using a single centralized resource pool, thereby preventing collisions while maintaining simplicity

Inventive Principle:

Principle #3Local quality

3Productivity

If dedicated preambles are allocated for each SSB, then random access efficiency is improved, but signaling overhead and configuration complexity increase

Engineering Contradiction:

Improverandom access efficiencyVSAvoidsignaling overhead

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent merges the functions of SSB indication and preamble selection by using SSB indices to implicitly indicate which preamble group should be used. This combining approach maintains random access efficiency through dedicated preambles while reducing signaling overhead, as the same SSB index that identifies the beam also identifies the preamble group

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent makes the SSB index serve multiple functions: it identifies the downlink beam/SSB being measured and simultaneously indicates the corresponding preamble group for uplink random access. This multi-functionality eliminates the need for separate signaling to indicate preamble group selection, reducing overhead while maintaining efficiency

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11272534B2Contention-free random access with multiple SSB

Publication Date: 2022.03.08 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

According to some embodiments, a method in a wireless device of performing random access comprises receiving a random access configuration. The random access configuration comprises one or more associations of a synchronization signal block (SSB), a preamble sequence, and physical random access channel (PRACH) configuration resources. The PRACH resources comprise time domain resources and frequency domain resources. The method further comprises receiving one or more SSBs; selecting one of the one or more received SSBs; and selecting a preamble sequence. The preamble sequence is associated with the selected SSB in the random access configuration. The method further comprises transmitting the selected preamble sequence on PRACH resources associated with the selected SSB in the random access configuration. In particular embodiments, more than one SSB is associated with identical PRACH resources, and the preamble sequence associated with each of the more than one SSBs identifies the SSB with respect to the PRACH resources.