RACH Occasion Overlap Indication for Lower 5G NR Access Latency
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Solution Overview
Problem
Current 5G NR systems restrict random access channel (RACH) occasions to non-overlapping with downlink transmissions, leading to increased latency and inefficient use of resources.
Innovation Solution
Allowing full-duplex (FD) RACH occasions to overlap with downlink transmissions, enabling UEs to select between HD and FD ROs based on latency or reliability criteria, with BS providing indications of overlap through RMSI signals or RSRP thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If downlink transmission indication is not provided for RACH occasions, then UE power consumption is reduced, but uplink access latency increases and random access efficiency deteriorates
Solution Approach 1:
The network pre-configures multiple RACH occasions and their corresponding downlink transmission indications during system initialization. This preliminary configuration allows UEs to know in advance which RACH occasions will have downlink transmissions, enabling them to wake up only at those specific times to monitor PDCCH, thereby reducing power consumption while maintaining timely access capability.
Solution Approach 2:
The random access procedure is segmented into multiple pre-configured RACH occasions rather than using a single unified occasion. Each RACH occasion is associated with specific downlink transmission indications, allowing UEs to selectively monitor only relevant occasions based on their access needs, thus balancing power savings with access latency requirements.
2Productivity
If multiple RACH occasions are configured with downlink transmission indications, then random access efficiency is improved, but signaling overhead and system complexity increase
Solution Approach 1:
A unified RACH configuration framework is established that can accommodate multiple RACH occasions with different downlink transmission indications. This universal configuration approach allows the system to flexibly support various access scenarios (e.g., beam failure recovery, initial access, scheduling request) without requiring separate dedicated configurations for each scenario, thereby improving access efficiency while controlling system complexity.
Data Source
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AI summary
Certain aspects of the present disclosure provide techniques for indicating an overlap of downlink transmissions with one or more random access channel occasions (ROs). A method that may be performed by a user equipment (UE) includes receiving signaling from a base station (BS) including an indication of whether one or more ROs will overlap with downlink transmissions in one or more periods of time, transmitting, to the BS based on the indication, a random access channel (RACH) preamble in an RO of the one or more ROs during the one or more periods of time, and performing a RACH procedure with the BS based on the transmitted RACH preamble.