SSB-Based Random Access Mapping for Multiplexed NR UE Transmissions
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Solution Overview
Problem
The 2-step random access procedure in NR wireless communication systems faces challenges in determining the appropriate synchronization signal block (SSB) selection, beam usage, radio network temporary identifier (RNTI), and modulation coding scheme (MCS) for combined message transmissions, particularly when multiple UEs are multiplexed in a single Physical Downlink Shared Channel (PDSCH) message.
Innovation Solution
A method for UE and base station operations that involve selecting synchronization signals and physical broadcast channel blocks based on signal measured metrics, determining appropriate beams, RNTIs, and MCSs to facilitate effective multiplexing and response messaging in the 2-step random access procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple UEs are multiplexed in a single PDSCH message for 2-step random access, then resource utilization efficiency is improved, but determining appropriate beams, RNTIs, and MCS for combined transmissions becomes complex
Solution Approach 1:
The patent segments the determination process for beams, RNTIs, and MCS by associating them with specific SSBs. Each SSB serves as an independent reference for these parameters, allowing the system to handle multiple UEs through separate SSB associations rather than requiring complex coordinated determination for all UEs simultaneously.
Solution Approach 2:
The patent performs preliminary determination of beams, RNTIs, and MCS during the SSB selection and association phase, before the actual multiplexed transmission occurs. This advance preparation eliminates the need for complex real-time determination during the random access procedure.
2Reliability
If SSB-based association is used for PRACH occasions and preambles, then beam alignment and resource allocation are improved, but the complexity of SSB selection and reporting increases
Solution Approach 1:
The patent makes the SSB serve multiple functions simultaneously: it acts as a reference for beam alignment, as an identifier for PRACH occasion association, as a basis for preamble selection, and as a reference for determining transmission parameters. This multi-functionality reduces the need for separate mechanisms for each purpose.
Solution Approach 2:
The patent applies different association rules and reporting requirements for different SSBs based on their specific characteristics and the corresponding PRACH occasions. Each SSB-PRACH pair can have customized association parameters, allowing optimized local configurations rather than uniform system-wide rules.
3Loss of time
If 2-step random access procedure is implemented, then access latency is reduced, but challenges arise in handling timing advance and uplink synchronization
Solution Approach 1:
The patent performs timing advance determination and uplink synchronization setup during the initial msgA transmission phase, using the associated SSB as a reference. This preliminary synchronization preparation ensures that subsequent msgB transmissions and uplink communications can proceed without additional synchronization delays.
Data Source
AI summary
Embodiments of the present disclosure provide methods and apparatuses for random access procedure. A method at a user equipment (UE) comprises selecting a synchronization signal and physical broadcast channel block (SSB) with a signal measured metric satisfying a criterion. The method further comprises transmitting a first message including a random access channel (RACH) preamble on a RACH occasion and data on an uplink shared channel (USCH) to a base station. The RACH preamble and the RACH occasion are selected based on a mapping of the SSB to the RACH preamble and the RACH occasion. The method further comprises receiving a second message from the base station as a response to the first message.