RACH Subband Allocation for Low-Bandwidth UE Random Access
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Solution Overview
Problem
User equipment (UE) operating on lower frequency bands, such as eRedcap UEs, face challenges in defining frequency domain resource allocation for random access channel (RACH) transmissions, leading to increased latency and inefficient communications due to limited frequency range.
Innovation Solution
The UE maps RACH occasions (ROs) to a set of subbands based on frequency resource allocation, determining subbands for physical RACH and PUSCH transmissions, and network entities can provide mappings to facilitate efficient communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If UEs operate on lower frequency bands with limited frequency range, then device complexity is reduced and power consumption is lowered, but frequency resource allocation capability deteriorates and communication efficiency decreases
Solution Approach 1:
The patent divides the frequency domain resources into multiple subbands and segments RACH occasions into different groups. Each UE can be allocated to specific subbands and RO groups based on its capabilities, allowing limited-frequency UEs to operate efficiently within their constraints while maintaining overall system productivity through structured resource division.
Solution Approach 2:
The patent enables different frequency resource allocation strategies for different UEs based on their specific capabilities. UEs with limited frequency ranges are allocated appropriate subbands and RO groups tailored to their constraints, while other UEs can utilize broader frequency resources, optimizing communication efficiency for each device type locally.
2Device complexity
If traditional frequency domain resource allocation is used, then resource management is simplified, but latency increases and communication efficiency deteriorates for UEs with limited frequency ranges
Solution Approach 1:
The patent performs preliminary grouping of RACH occasions and pre-allocates subbands to UE groups before actual random access occurs. This advance organization allows UEs with limited frequency ranges to quickly find suitable resources without complex real-time allocation decisions, reducing latency while maintaining manageable resource allocation complexity through pre-computed mappings.
3Productivity
If frequency resource allocation is optimized for lower frequency bands, then communication efficiency improves and latency reduces, but device complexity and configuration complexity increase
Solution Approach 1:
The patent introduces configurable parameters such as subband sizes, RO group configurations, and UE capability thresholds that can be adjusted to balance communication efficiency and configuration complexity. By making these parameters configurable rather than fixed, the system can be optimized for different deployment scenarios while providing a standardized framework that manages overall complexity.
Data Source
AI summary
Methods, systems, and devices for method for wireless communication are described. A user equipment (UE) may receive, from a network entity, an indication of an uplink bandwidth part associated with a random access procedure, and the uplink bandwidth part may include a plurality of subbands corresponding to a set of random access occasions. The UE may select a random access occasion from the set of random access occasions based on an offset parameter, and the UE may transmit an uplink random access channel message at the random access occasion of the set of random access occasions.