Dynamic RACH Configuration in NR Unlicensed Spectrum
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently configuring random access channel (RACH) occasions in NR unlicensed spectrum, leading to increased random access delay and reduced resource utilization due to non-deterministic channel access and limited PRACH resource availability.
Innovation Solution
A user equipment (UE) in a wireless communication system is configured to receive downlink control information (DCI) from a base station, determining time and frequency domain resource allocation for RACH occasions and performing channel sensing to identify the status of the uplink channel, allowing for optimized transmission of a physical random access channel (PRACH) preamble.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional RACH configuration is used in NR unlicensed spectrum, then device compatibility is maintained, but random access delay increases and resource utilization decreases
Solution Approach 1:
The patent implements dynamic RACH occasion configuration where the base station determines time domain resource allocation information and channel sensing information based on current channel conditions, then signals this configuration to UEs via DCI. This allows the RACH configuration to adapt dynamically to changing unlicensed spectrum conditions, reducing access delay while optimizing resource utilization compared to static traditional configurations.
Solution Approach 2:
The patent changes key parameters including time domain resource allocation information, channel sensing information, and association between discovery reference signals and RACH occasions. By dynamically adjusting these parameters based on channel sensing results and traffic conditions, the system achieves lower random access delay and improved resource utilization while maintaining compatibility with existing UE implementations.
2Productivity
If dynamic channel sensing and allocation is implemented, then resource utilization improves and access delay reduces, but system complexity increases
Solution Approach 1:
The patent introduces downlink control information (DCI) as an intermediary mechanism that carries time domain resource allocation information and channel sensing information from the base station to UEs. This intermediary structure simplifies the implementation complexity by providing a standardized interface for dynamic configuration, allowing UEs to adapt to changing conditions without requiring complex internal decision-making logic.
Solution Approach 2:
The patent implements a feedback mechanism where the base station performs channel sensing, determines optimal RACH configuration parameters, and signals these to UEs via DCI. This closed-loop feedback approach enables the system to adapt to changing channel conditions while maintaining manageable complexity through centralized control at the base station rather than distributed decision-making at each UE.
3Object-affected harmful factors
If PRACH resource availability is limited, then interference is reduced, but random access delay increases
Solution Approach 1:
The patent introduces discovery reference signals as an additional dimension for associating with RACH occasions, creating a two-dimensional resource allocation structure (time domain resources plus discovery reference signal associations). This allows the system to manage interference by spreading RACH opportunities across multiple dimensions while maintaining controlled resource usage, thereby reducing both interference and access delay simultaneously.
Data Source
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AI summary
A method and apparatus of user equipment (UE) in a wireless communication system supporting a shared spectrum channel access is provided. The method and apparatus comprises: receiving, from a base station (BS), a physical downlink control channel (PDCCH) including downlink control information (DCI); determining, based on the received DCI, time domain resource allocation information of a random access channel (RACH) occasion and channel sensing information; performing channel sensing on an uplink (UL) channel based on the determined channel sensing information; identifying a status of the UL channel based on a result of the channel sensing on the UL channel; and transmitting, to the BS, a physical random access channel (PRACH) preamble over the UL channel based on the determined time domain resource allocation information and the identified status of the UL channel.