SBFD Synchronization Signal Blocks for CLI-Aware RACH Mapping

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Solution Overview

Problem

In subband full duplex (SBFD) communication, user equipment (UE) transmitting an uplink communication can cause severe UE-to-UE cross-link interference (CLI) to another UE receiving a downlink communication, particularly in densely populated areas, due to the transmission of random access channel (RACH) messages in symbols configured for SBFD.

Innovation Solution

Implementing an indication mechanism for UE and network node to manage synchronization signal block (SSB) to random access channel (RACH) occasion (RO) mapping, allowing or restricting the use of specific beams for RACH transmission based on actual SSB transmission, using bitmaps to reduce CLI.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If RACH messages are transmitted in SBFD symbols, then random access communication is enabled, but severe UE-to-UE cross-link interference occurs

Engineering Contradiction:

Improverandom access communication capabilityVSAvoidUE-to-UE cross-link interference

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by differentiating the treatment of different SSBs through the first and second bitmaps. The first bitmap indicates whether each SSB is transmitted in SBFD symbols, while the second bitmap selectively indicates SSBs that can be used for RACH occasion mapping. This allows the system to enable random access communication for specific SSBs while restricting it for others, thereby reducing UE-to-UE cross-link interference in densely populated areas where SSBs are transmitted in SBFD symbols.

Inventive Principle:

Principle #3Local quality

2Area of stationary object

If SSBs are transmitted in multiple beams for coverage, then communication coverage is improved, but UE-to-UE CLI increases in densely populated areas

Engineering Contradiction:

Improvecommunication coverage areaVSAvoidUE-to-UE cross-link interference

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent implements local quality by applying different RACH occasion mapping rules to different SSBs based on their transmission characteristics. Through the first and second bitmaps, the system identifies which SSBs are transmitted in SBFD symbols and restricts RACH mapping for those SSBs. This allows the network to maintain multi-beam coverage while preventing UE-to-UE CLI in densely populated areas where SSBs are transmitted in SBFD symbols.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces bitmaps as intermediary structures to mediate between the SSB transmission configuration and the RACH occasion mapping. The first bitmap serves as an intermediary indicator of SSB transmission in SBFD symbols, while the second bitmap serves as an intermediary for selective RACH mapping. These intermediary structures enable the system to manage the conflict between providing wide coverage through multiple beams and preventing UE-to-UE interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If RACH occasion mapping is configured for all SSBs, then random access accessibility is improved, but interference management becomes difficult

Engineering Contradiction:

Improverandom access accessibilityVSAvoidinterference management complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the SSB list into two groups based on transmission characteristics: SSBs transmitted in SBFD symbols and SSBs transmitted in non-SBFD symbols. The first and second bitmaps segment the RACH mapping configuration accordingly, allowing the system to enable random access for SSBs transmitted in non-SBFD symbols while restricting it for SSBs transmitted in SBFD symbols. This segmentation simplifies interference management by clearly delineating which SSBs can and cannot be used for RACH mapping.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses bitmaps as intermediary structures to simplify the complex task of managing RACH occasion mapping across multiple SSBs with different transmission characteristics. The first and second bitmaps serve as intermediary indicators that convey transmission information and mapping restrictions in a compact, easily processable format. This intermediary approach reduces the complexity of interference management while maintaining random access accessibility for appropriate SSBs.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250338315A1Synchronization signal blocks for subband full duplex random access channel

Publication Date: 2025.10.30 QUALCOMM INC

AI summary

Various aspects of the present disclosure generally relate to wireless communication. Some aspects more specifically relate to an indication of whether a user equipment (UE) is allowed to use a beam corresponding to a transmitted synchronization signal block (SSB) for subband full duplex (SBFD) random access channel (RACH). For example, the indication may indicate whether the UE is allowed to transmit a RACH message in a RACH occasion (RO) mapped to a transmitted SSB. In some aspects, a network node may also transmit, and the UE may also receive, an indication of which SSBs were actually transmitted in a synchronization signal (SS) burst.