2-Step RACH Preamble-to-PUSCH Mapping for Low-Latency Access
Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing the mapping between Physical Random Access Channel (PRACH) preambles and Physical Uplink Shared Channel (PUSCH) resource units, particularly in the context of 2-step Random Access Channel (RACH) procedures in 5G new radio (NR) networks.
Innovation Solution
The proposed solution involves configuring a specific number of PRACH occasions associated with PUSCH occasions, and mapping PRACH preambles to PUSCH resource units based on various ordering rules, such as increasing order of preamble indexes, frequency resource indexes, or time resource indexes, to optimize resource allocation and reduce latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple PRACH occasions are configured with multiple preambles each, then system capacity and resource utilization are improved, but mapping complexity and latency increase
Solution Approach 1:
The patent segments the mapping process into distinct phases: first determining the total number of preambles across all PRACH occasions, then sequentially assigning preamble indices to PUSCH resource units based on ordered configurations. This segmentation breaks down the complex many-to-many mapping into manageable sequential steps, reducing implementation complexity while maintaining support for multiple PRACH occasions and high system capacity.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the number of preambles per PRACH occasion and pre-establishing the ordering rules (frequency, time, or code domain) before the actual random access procedure begins. This pre-configuration allows the gNB and UE to quickly execute the mapping without real-time complex calculations, thereby reducing latency while supporting multiple PRACH occasions for enhanced system capacity.
2Adaptability or versatility
If preamble indexing follows multiple ordering rules (frequency, time, code), then resource allocation flexibility is improved, but processing complexity increases
Solution Approach 1:
The patent implements dynamics by allowing the network to dynamically select different ordering rules (frequency domain, time domain, or code domain) based on current radio conditions and traffic patterns. The gNB can adaptively choose the most appropriate ordering rule for specific scenarios, providing resource allocation flexibility while keeping the actual processing relatively simple through standardized indexing procedures for each rule type.
Solution Approach 2:
The patent applies parameter changes by modifying the ordering parameter (frequency index, time index, or code index) according to different operational requirements. Each ordering rule changes the primary parameter used for preamble indexing, allowing flexible resource allocation across different domains while maintaining a consistent and manageable processing approach for each specific parameter type.
3Loss of time
If PRACH and PUSCH occasions are tightly coupled, then access latency is reduced, but resource allocation complexity increases
Solution Approach 1:
The patent merges the PRACH and PUSCH occasion configurations by establishing a direct one-to-one correspondence between PRACH occasions and associated PUSCH occasions. Each PRACH occasion is tightly coupled with a specific PUSCH occasion, allowing UEs to complete random access procedures within a single uplink slot. This merging reduces access latency by eliminating separate scheduling steps while managing resource allocation complexity through standardized association rules.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the association between PRACH occasions and PUSCH occasions before the random access procedure begins. The gNB provides UE with information about which PUSCH occasion corresponds to which PRACH occasion in advance, allowing tight coupling without real-time complex resource allocation decisions, thereby reducing access latency while keeping resource management tractable.
Data Source
AI summary
This disclosure describes improving a 4-step RACH procedure by using a 2-step RACH procedure. A UE transmits a PRACH preamble and associated MsgA physical uplink shared channel (PUSCH) on a configured time and frequency resource. After successful detection of the PRACH preamble, and decoding of the MsgA PUSCH, the gNB transmits MsgB in the second step. Generally, a mapping is used between the PRACH preamble and the PUSCH resource unit for 2-step RACH. This disclosure describes the mapping for 2-step RACH.