Two-Step RACH Configuration for NTN Coverage
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Solution Overview
Problem
Two-step random access procedures in wireless communication systems, particularly in non-terrestrial networks, face inefficiencies due to high overhead from re-transmissions and limited flexibility in repetition schemes, leading to increased latency and reduced coverage.
Innovation Solution
The implementation of a two-step random access channel configuration that decouples preamble repetitions from PUSCH repetitions, allowing for more flexible repetition schemes and supporting demodulation reference signal bundling or frequency hopping, based on a preamble-to-PO mapping, which includes jumbo POs spanning greater than one slot and orthogonal or non-orthogonal DMRS patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional four-step random access procedure is used, then coverage is improved, but latency is increased
Solution Approach 1:
The patent segments the random access procedure into two steps (message A and message B) instead of four steps, by combining the preamble and payload into a single uplink transmission. This segmentation reduces the number of round-trip exchanges while maintaining coverage through repetition schemes, thereby reducing latency without sacrificing reliability
Solution Approach 2:
The patent implements preliminary action by transmitting both preamble and payload data in advance within message A, rather than waiting for separate acknowledgment and response exchanges. This allows the network to process both components simultaneously and reduce overall access latency while maintaining coverage through configured repetitions
2Loss of time
If two-step random access is implemented, then latency is reduced, but overhead from re-transmissions increases
Solution Approach 1:
The patent applies dynamics by making the repetition scheme configurable and adaptable - the network can dynamically adjust the number of repetitions and their distribution across slots based on channel conditions and traffic requirements. This allows optimization of overhead while maintaining low latency performance
Solution Approach 2:
The patent changes parameters by introducing configurable repetition factors, slot offsets, and resource allocation parameters for the two-step RACH procedure. These parameter adjustments allow the system to optimize the balance between overhead and latency based on specific deployment scenarios and channel conditions
3Device complexity
If fixed repetition schemes are used, then device complexity is reduced, but adaptability to different channel conditions decreases
Solution Approach 1:
The patent implements universality by creating a multi-functional repetition framework that can adapt to different channel conditions, device capabilities, and service requirements through configured parameters. The same basic two-step procedure structure serves multiple functions across diverse scenarios, maintaining simplicity while providing flexibility
4Reliability
If PO spans multiple slots, then coverage is improved, but resource allocation complexity increases
Solution Approach 1:
The patent segments the multi-slot PO into manageable units with defined slot offsets and repetition patterns, allowing independent configuration of each slot's resource allocation while maintaining overall coverage enhancement. This segmentation simplifies the complexity of managing resources across multiple slots
Data Source
AI summary
Aspects are provided which allow coverage enhancement and support in NTNs for repetition, frequency hopping, and antenna switching during msgA transmissions based on a preamble-to-PO mapping. In one aspect, the base station provides and the UE obtains a RACH configuration associating a preamble with at least one PO for two-step random access, where the PO spans a time interval greater than one slot. In another aspect, the base station provides and the UE obtains a RACH configuration associating a preamble with a plurality of POs for two-step random access. In a further aspect, the base station provides the UE a plurality of configurations each indicating a PO for two-step random access. In an additional aspect, the base station provides the UE a configuration indicating a guard band for a PO for two-step random access, where the guard band is indicated in units of subcarriers spanning less than one PRB.