SSB Selection for RACH Access Under Partial Beam Transmission
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Solution Overview
Problem
Configured reference signals (RSs) such as SSBs and CSI-RSs may not all be transmitted by a network, leading to challenges in beam estimation and random access channel (RACH) occasion configurations for wireless transmit/receive units (WTRUs).
Innovation Solution
A WTRU receives configuration information including indications of estimation SSBs, allowed SSBs, and RACH occasions, determines RSRP values, and uses an AI machine learning (AIML) model to select the best SSB for RACH transmission based on RSRP, periodicity, and priority.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the network transmits only a subset of configured SSBs (Set B beams) to reduce transmission overhead, then transmission efficiency is improved, but beam estimation accuracy deteriorates because not all configured RSs are available for measurement
Solution Approach 1:
The network pre-configures the WTRU with a complete set of SSBs (Set A beams) before actual transmission. The WTRU performs beam estimation using these pre-configured SSBs even though not all are transmitted, allowing accurate beam selection before the random access procedure begins. This preliminary estimation enables the WTRU to identify the best beam from the full set, compensating for the fact that only a subset will be transmitted.
Solution Approach 2:
The patent introduces an intermediary mechanism where the WTRU uses RSRP measurements of transmitted SSBs (Set B) to infer and estimate the quality of non-transmitted SSBs (Set A). The WTRU determines an estimated RSRP for Set A beams based on the received Set B measurements, acting as an intermediary to bridge the gap between transmitted and non-transmitted beams for accurate beam estimation.
2Measurement precision
If the WTRU estimates beams using non-transmitted SSBs (Set A beams) to improve beam selection accuracy, then beam estimation capability is improved, but system complexity increases due to additional RSRP determination and mapping procedures
Solution Approach 1:
The network provides pre-configuration information including the complete set of SSBs (Set A) and their associated RACH occasions before the WTRU needs to perform random access. This preliminary provision of configuration data reduces the computational complexity during actual beam estimation, as the WTRU already has the mapping information ready and does not need to dynamically determine relationships between beams and RACH occasions.
Solution Approach 2:
The WTRU creates a virtual representation or copy of the non-transmitted SSBs (Set A) by estimating their RSRP values based on transmitted SSB measurements. This copying approach allows the WTRU to work with estimated beam qualities without actually receiving all physical SSB transmissions, reducing the need for complex hardware processing while maintaining estimation accuracy.
3Reliability
If the WTRU determines RSRP for all configured SSBs including non-transmitted ones to improve random access performance, then RACH transmission accuracy is improved, but processing time increases due to additional estimation and comparison operations
Solution Approach 1:
The network pre-configures the WTRU with SSB sets and their associations with RACH occasions before the WTRU needs to perform measurements. This preliminary configuration allows the WTRU to quickly map measured SSBs to appropriate RACH occasions without performing complex real-time analysis, reducing processing time while maintaining accurate beam-RACH mapping for reliable random access transmission.
Data Source
AI summary
A wireless transmit/receive unit (WTRU) may receive configuration information. The configuration information may include one or more of an indication of a set of estimation synchronization signal blocks (SSBs), a set of random access channel (RACH) occasions (ROs) configurations associated with the set of estimation SSBs, an indication of a set of actually transmitted SSBs, and/or a set of ROs configurations associated with the set of actually transmitted SSBs. The WTRU may receive an indication of allowed estimation SSBs including a subset of the set of estimation SSBs that are allowed to be used for a RACH transmission. The WTRU may determine a reference signal received power (RSRP) value for each estimation SSB and/or for each actually transmitted SSB. The WTRU may determine a (e.g., selected) SSB out of the set of estimation SSBs or the set of actually transmitted SSBs, for example for a RACH transmission.