SSB to PRACH Resource Mapping in 5G NR Unlicensed
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Solution Overview
Problem
In 5G new radio unlicensed (NRU) systems, the limited availability of frequency domain resources on licensed spectra leads to inefficient utilization of PRACH time-frequency-code resources due to channel sensing failures, resulting in wasted resources and reduced synchronization signal sending occasions.
Innovation Solution
Mapping two candidate SSB occasions to a single PRACH time-frequency-code resource allows for efficient channel sensing and resource utilization, ensuring that even if one occasion fails, the other can still be used for sending synchronization signals, thereby avoiding resource wastage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one-to-one mapping between candidate SSB occasions and PRACH time-frequency-code resources is used, then terminal devices can reliably determine PRACH resources after detecting SSBs, but PRACH resources are wasted when channel sensing fails on certain occasions
Solution Approach 1:
The patent merges multiple candidate SSB occasions into a single PRACH time-frequency-code resource through one-to-many mapping. Specifically, multiple candidate SSB occasions are mapped to the same PRACH resource, allowing terminal devices to use any successfully detected SSB to access the corresponding PRACH resource. This resolves the contradiction by ensuring PRACH resources are not wasted when channel sensing fails on certain occasions, while maintaining reliable determination of PRACH resources through the mapping relationship.
2Area of stationary object
If multiple candidate SSB occasions are supported in SSB time window, then coverage of terminal devices is extended, but channel sensing failures cause waste of PRACH resources
Solution Approach 1:
The patent combines multiple candidate SSB occasions that map to the same PRACH resource, enabling the network to send SSBs on multiple occasions for extended coverage while ensuring that if channel sensing fails on any occasion, the PRACH resource remains available for terminal devices that successfully detected SSBs on other occasions. This resolves the contradiction between extended coverage and PRACH resource utilization efficiency.
3Adaptability or versatility
If listen-before-talk mechanism is used on unlicensed spectrum, then spectrum sharing with other systems is enabled, but SSB sending occasions are reduced due to channel sensing failures
Solution Approach 1:
The patent merges multiple candidate SSB occasions into a single PRACH time-frequency-code resource through one-to-many mapping. This allows the network to send SSBs on multiple occasions for extended coverage while ensuring that if channel sensing fails on any occasion, the PRACH resource remains available for terminal devices that successfully detected SSBs on other occasions. This resolves the contradiction between spectrum sharing capability and SSB sending occasion quantity.
Data Source
AI summary
A random access method, a communications apparatus, a chip, and a storage medium are described. A terminal device receives a first synchronization signal/PBCH block (SSB) on a first candidate SSB occasion. The first candidate SSB occasion is associated with a first random access channel time-frequency-code resource, and the terminal device sends random access information on the first random access channel time-frequency-code resource. The first candidate SSB occasion is included in L candidate SSB occasions. The L candidate SSB occasions are periodically and sequentially associated with random access channel time-frequency-code resources. By using M adjacent candidate SSB occasions as a mapping periodicity, M is less than L.