5G-NR PRACH Format Configuration for Diverse UE Capabilities
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Solution Overview
Problem
Existing wireless communication technologies, particularly in 5G-NR, face challenges in improving coverage, supporting higher user densities, reducing latency, and optimizing PRACH processes to accommodate diverse use cases and device capabilities.
Innovation Solution
Enhancements to the Physical Random Access Channel (PRACH) include configuring PRACH formats, frequency hopping, beam sweeping, and power level adjustments, along with PRACH repetition and synchronization signal block mappings to optimize random access procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If PRACH repetition is implemented to improve coverage, then coverage area is improved, but latency increases due to multiple transmissions
Solution Approach 1:
The system performs preliminary actions by transmitting multiple PRACH preambles in advance across different beams and occasions. The UE prepares and sends redundant preamble transmissions before the network can respond, ensuring that at least one transmission will be successfully received even in challenging coverage conditions. This preliminary repetition strategy improves coverage while the network's efficient recognition of repeated preambles helps mitigate the latency penalty.
2Adaptability or versatility
If multiple PRACH formats are configured to support diverse UE capabilities, then adaptability is improved, but device complexity increases
Solution Approach 1:
The system implements dynamic adaptability where the network configures multiple PRACH formats (a0-a3, b0-b3) with different time-frequency structures, cyclic prefix lengths, and preamble lengths. The UE dynamically selects and uses the appropriate format based on its capabilities and the configured parameters. This dynamic configuration allows the system to adapt to diverse UE capabilities without requiring every device to be hard-coded with support for all possible formats, thereby managing complexity while maintaining versatility.
Solution Approach 2:
The patent employs parameter changes by defining multiple PRACH formats with varying characteristics including subcarrier spacing (15, 30, 60, 120 kHz), cyclic prefix lengths (160, 256, 512, 768 samples), and preamble lengths (839, 139). The network configures specific formats based on deployment scenarios and UE capabilities, allowing the system to optimize performance for different use cases while keeping the implementation complexity manageable through standardized parameter sets.
3Reliability
If PRACH frequency hopping is implemented to improve reliability, then reliability is improved, but device complexity increases due to additional frequency management
Solution Approach 1:
The system implements periodic frequency hopping where the PRACH preamble transmission frequency is changed at regular intervals according to a predetermined pattern. The frequency hops between different resource blocks or resource block groups in a systematic manner, providing diversity against frequency-selective fading and interference. This periodic frequency change improves reliability by ensuring that not all transmissions occur on the same potentially degraded frequency resource, while the regular pattern keeps the implementation complexity manageable through predictable behavior.
4Area of stationary object
If beam sweeping is implemented to improve coverage in mmWave, then coverage is improved, but latency increases due to multiple beam transmissions
Solution Approach 1:
The system segments the beam sweeping process into multiple independent PRACH occasions, each associated with a specific beam direction. Instead of transmitting all beams sequentially in a single continuous sweep, the patent divides the coverage area into multiple beam sectors and allocates dedicated PRACH resources to each beam. This segmentation allows the network to process and respond to transmissions from different beams more efficiently, reducing the overall latency while maintaining comprehensive coverage through the distributed beam structure.
Data Source
AI summary
A UE may transmit a message comprising information regarding one or more physical random access channel (PRACH) capabilities of the UE to a base station (BS). The UE may then receive, from the BS, signaling comprising an indication of one or more configured PRACH formats supporting the one or more PRACH capabilities. Next, the UE may transmit, using the one or more configured PRACH formats, one or more preambles to the BS in a random access (RACH) procedure. Accordingly, the UE may receive a random access response (RAR) from the base station and further, in response to receiving the RAR, establish a connection with the BS.