Multi-Slot RACH Transmission for Subband Full-Duplex Access
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Solution Overview
Problem
In wireless communications systems, particularly in subband full duplex (SBFD) mode, user equipment (UEs) face challenges in transmitting random access channel (RACH) messages due to limited uplink frequency resources, leading to potential collisions and reduced initial access accuracy and coverage.
Innovation Solution
UEs are configured to transmit RACH messages in uplink subbands of SBFD slots based on network-provided configurations, allowing for repeated transmissions across multiple slots and mapping synchronization signal blocks (SSBs) to RACH occasions, thereby optimizing resource utilization and enhancing accuracy and coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If UEs transmit RACH messages in SBFD slots using limited uplink frequency resources, then the system supports full duplex operation, but message collisions increase and initial access accuracy deteriorates
Solution Approach 1:
The patent extends RACH message transmission from single-slot to multi-slot dimension, allowing UEs to transmit RACH messages across multiple SBFD slots. This temporal dimension expansion increases available transmission opportunities and resources, thereby improving initial access accuracy while maintaining full duplex operation.
Solution Approach 2:
The patent enables UEs to perform preliminary RACH message transmissions in earlier SBFD slots before attempting access in subsequent slots. This preliminary action allows the system to establish initial contact and resolve collisions before final access completion, improving overall reliability.
2Reliability
If UEs repeat RACH messages across multiple slots, then initial access accuracy improves, but transmission time increases
Solution Approach 1:
The patent implements periodic RACH message transmission across multiple SBFD slots, where UEs repeat transmissions at regular interval slots. This periodic action maintains signal presence over time, improving detection accuracy while controlling overall transmission time through structured repetition patterns.
3Device complexity
If fewer SSBs are mapped to SBFD slots due to limited uplink resources, then resource allocation simplifies, but initial access coverage reduces
Solution Approach 1:
The patent segments the SSB-to-RACH occasion mapping across multiple SBFD slots rather than concentrating all mappings in single slots. This segmentation distributes the mapping load, maintaining manageable complexity while extending coverage through multi-slot transmission opportunities.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may receive control signaling that indicates a configuration for subband full duplex (SBFD) slots and a random access channel (RACH) configuration for SBFD slots. The UE may transmit at least one instance of a RACH message in an uplink subband of an SBFD slot in accordance with the RACH configuration. The RACH configuration may enable a UE to repeat a RACH message or transmit a multi-slot RACH message across an SBFD slot and an uplink slot. The RACH configuration may map synchronization signal blocks (SSB)s to RACH occasions in the uplink subband of the SBFD slot. In some examples, the SSBs may be mapped across multiple (e.g., consecutive) SBFD slots. In some cases, the RACH configuration may enable a UE to repeat a RACH message or transmit a multi-slot RACH message across multiple SBFD slots.