SSB-to-RACH Occasion Mapping for Low-Tier UE Access Latency
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Solution Overview
Problem
Conventional techniques for identifying random access occasions and performing random access procedures in wireless communications systems have limitations for devices with reduced capabilities, such as low-tier UEs, leading to challenges in coverage and increased latency.
Innovation Solution
A RACH configuration that allocates resources for RACH transmissions with different time-domain and frequency-domain multiplexing for low-tier UEs, allowing for non-overlapping or overlapping resource configurations to support power savings and reduce latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional random access procedures are used for low-tier UEs, then device complexity is reduced, but coverage is insufficient and latency increases
Solution Approach 1:
The patent segments the random access procedure into multiple occasions (first RACH occasion and second RACH occasion) with different SSB associations. Low-tier UEs can attempt access in the first occasion, and if unsuccessful, retry in the second occasion without causing full-buffer latency, thus improving coverage while managing time loss.
Solution Approach 2:
The patent introduces dynamic SSB association where different RACH occasions are associated with different SSBs (synchronization signal blocks). This dynamic association allows the system to adapt to varying channel conditions and UE capabilities, improving coverage for low-tier UEs by providing multiple access opportunities with different beam configurations.
2Reliability
If multiple RACH configurations are provided for low-tier UEs, then coverage and power savings are improved, but device complexity increases
Solution Approach 1:
The patent provides multiple RACH configurations specifically for low-tier UEs that may not need all configurations. By offering partial action (multiple configurations) only to devices that require them, the system improves coverage for vulnerable devices without unnecessarily increasing complexity for all UEs.
3Use of energy by moving object
If random access resources are allocated for low-tier UEs, then power savings are maintained, but spectrum utilization may be affected
Solution Approach 1:
The patent implements periodic random access occasions with different SSB associations. Low-tier UEs can perform access attempts periodically without continuous transmission, maintaining power savings while still achieving successful access. The periodic structure allows spectrum resources to be efficiently reused across different time instances.
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AI summary
Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for a user equipment (UE) receiving, from a base station, one or more random access channel (RACH) configurations. The RACH configurations may allocate resources for a contention-based RACH procedure for accessing a wireless network. Based on the RACH configurations, the UE may determine a set of random access occasions for an association period. From the set of random access occasions, the UE may map one or more indices of a plurality of synchronization signal blocks to one or more random access occasions. Using the one or more random access occasions, the UE may transmit a random access sequence, including one or more repetitions of the random access sequence to the base station to access the wireless network.