Two-Step RACH Resource Mapping and Timing Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless communication systems, particularly 5G NR systems, face implementation challenges with 2-step RACH processes, including efficient transmission of MAC PDUs with varying sizes and QoS requirements, reliable MsgA PUSCH reception for unsynchronized UEs, high BFR latency and radio resource inefficiency, large variations in RTT for Non-Terrestrial Networks, and the impact of LBT failures on 2-step RACH for NR-U.
Innovation Solution
The proposed solution involves a series of mechanisms and methods to address the identified challenges, including RACH type selection based on network configuration, DL radio quality, MsgA payload size, logical channel, and timeAlignmentTimer; efficient MsgA resource selection using one-to-one, many-to-one, and one-to-many mappings between preambles and PUSCH Resource Units; improved timing alignment for unsynchronized UEs; optimized BFR procedures using 2-step RACH; and enhanced channel access procedures to mitigate LBT failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If 2-step RACH procedure is implemented to reduce access latency, then random access latency is reduced, but implementation complexity increases due to multiple mapping configurations and resource selection mechanisms
Solution Approach 1:
The patent segments the MsgA transmission into two distinct components: preamble transmission on PRACH and payload transmission on PUSCH. This segmentation allows independent optimization of each component's transmission parameters and enables flexible resource allocation strategies, thereby reducing overall access latency while managing implementation complexity through modular design
Solution Approach 2:
The patent implements dynamic RACH type selection where the UE can choose between 2-step RACH and 4-step RACH procedures based on current network conditions and requirements. The network can also dynamically configure different mapping types (one-to-one, many-to-one, one-to-many) between preambles and PUSCH resources, allowing the system to adapt to varying latency and resource allocation needs
2Productivity
If multiple mapping types between preambles and PUSCH resources are implemented to improve resource allocation efficiency, then resource allocation efficiency is improved, but device complexity increases due to multiple configuration parameters
Solution Approach 1:
The patent defines a universal framework that supports multiple mapping types (one-to-one, many-to-one, one-to-many) between preambles and PUSCH resources using a common configuration mechanism. The network can select different mapping types based on system conditions, and the UE executes corresponding procedures within the same overall framework, achieving flexible resource allocation without proportionally increasing implementation complexity
Solution Approach 2:
The patent manages configuration complexity by changing key parameters such as the mapping type indicator and resource allocation patterns rather than requiring completely different procedural implementations. The network configures mapping types through standardized parameters, and the UE adapts its behavior by adjusting resource selection based on these parameter changes, maintaining procedural simplicity while achieving diverse resource allocation strategies
3Reliability
If timing alignment mechanisms are improved for unsynchronized UEs to ensure reliable MsgA reception, then reception reliability is improved, but procedure complexity increases
Solution Approach 1:
The patent applies preliminary timing alignment actions before the actual MsgA transmission. The network performs downlink timing alignment procedures in advance, and the UE uses these pre-established timing information to configure its uplink transmission. This preliminary alignment ensures that when unsynchronized UEs transmit MsgA, their timing is already optimized for reliable reception, avoiding the need for complex real-time alignment procedures
4Loss of time
If BFR procedure is optimized using 2-step RACH to reduce beam failure recovery latency, then recovery latency is reduced, but radio resource efficiency deteriorates due to dedicated RACH resources for each candidate beam
Solution Approach 1:
The patent merges the BFR procedure with the 2-step RACH procedure, allowing beam failure recovery to utilize the same MsgA transmission mechanism as normal random access. Instead of having separate dedicated RACH resources for each candidate beam, the system combines BFR signaling with the existing preamble and payload transmission framework, thereby reducing recovery latency while improving radio resource efficiency through resource sharing
Data Source
AI summary
A first apparatus in a wireless communication system, the first apparatus including circuitry configured to trigger a Random Access Channel (RACH) procedure; select a two-step RACH procedure from among a plurality of RACH procedures as a RACH type to be performed; select a MsgA transmission resource; transmit a MsgA; and monitor for a network response from a second apparatus.