PRACH Repetition Timing in SBFD Uplink Random Access
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Solution Overview
Problem
The existing NR duplexing modes, particularly TDD, suffer from latency, reduced coverage, and capacity due to fixed slot structures, which are exacerbated by the separation of uplink and downlink phases in time, leading to inefficient use of resources.
Innovation Solution
Implementing sub-band non-overlapping full-duplex (SBFD) operation that allows simultaneous downlink and uplink transmissions on different physical resource blocks within an unpaired wideband NR cell, with UEs operating in half-duplex mode, and determining optimal PRACH occasions for preamble repetitions using configuration information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If TDD mode with fixed slot structure is used, then uplink and downlink phases are separated in time domain, but this creates unnecessary latency and reduces coverage and capacity
Solution Approach 1:
The patent introduces dynamic slot structure where the gNB can flexibly configure uplink and downlink slots based on traffic demand, transitioning from fixed TDD to dynamic TDD. This allows the system to adapt slot assignments in real-time, reducing latency by creating more uplink slots when needed and eliminating the rigid time separation constraint of traditional TDD.
Solution Approach 2:
The patent changes the parameter of slot structure from fixed to configurable, allowing dynamic adjustment of uplink-downlink slot ratios. By modifying this parameter based on traffic conditions, the system optimizes latency performance while maintaining TDD operation, directly addressing the contradiction between time loss and structural rigidity.
2Productivity
If uplink and downlink phases are separated in time domain, then scheduling is simplified, but this reduces the time duration available for uplink transmission in TDD
Solution Approach 1:
The patent implements dynamic slot configuration that allows the gNB to adjust the number and position of uplink slots based on real-time traffic demands. This dynamic approach increases uplink time duration when needed while maintaining scheduling control through gNB configuration, resolving the contradiction between productivity and ease of operation.
Solution Approach 2:
The patent introduces periodic reconfiguration of slot structures, where the gNB can update slot assignments at regular intervals or triggered by traffic conditions. This periodic adjustment mechanism allows the system to periodically increase uplink time duration while maintaining manageable scheduling complexity through structured reconfiguration cycles.
3Productivity
If SBFD operation is implemented allowing simultaneous DL and UL transmissions, then resource utilization improves, but UE must operate in half-duplex mode creating potential conflicts
Solution Approach 1:
The patent segments the frequency band into different sub-bands, with some sub-bands allocated for downlink and others for uplink during the same time period. This frequency division segmentation allows the gNB to achieve simultaneous DL and UL transmissions (improving resource utilization) while UEs only need to transmit or receive in their assigned sub-band at any given time (maintaining half-duplex operation without conflicts).
Solution Approach 2:
The patent applies different operational characteristics to different frequency sub-bands, where each sub-band is optimized for its specific direction (UL or DL). This local quality approach allows the system to achieve high resource utilization through simultaneous opposite-direction transmissions while accommodating half-duplex UEs by ensuring each UE operates in its designated sub-band mode.
4Reliability
If multiple PRACH occasions are configured for preamble repetitions, then coverage is improved, but determining the starting PRACH occasion becomes more complex
Solution Approach 1:
The patent enables the UE to autonomously determine the starting PRACH occasion by applying a formula that uses the UE's own identity (RA-RNTI) and the configured PRACH occasion parameters. This self-service mechanism eliminates the need for complex signaling from the gNB to indicate the starting occasion for each UE, reducing determination complexity while maintaining reliable coverage through multiple PRACH occasions.
Solution Approach 2:
The patent incorporates feedback mechanisms where the gNB configures PRACH occasion parameters including the number of repetitions and timing relationships, and UEs use this configured information to self-determine their starting occasions. This feedback loop provides UEs with the necessary information to calculate starting positions without increasing overall system complexity.
Data Source
AI summary
Example embodiments of the present disclosure relate to a solution for determining a set of physical random access channel (PRACH) occasions. In the solution, a first apparatus receives, from a second apparatus, configuration information indicating a first plurality of physical random access channel (PRACH) occasions and a second plurality of PRACH occasions, determines, based on the configuration information, and for each frequency resource index for frequency multiplexed PRACH occasions, a starting PRACH occasion of a set of PRACH occasions for a PRACH transmission with preamble repetitions from the PRACH occasions in uplink resource and the PRACH occasions in SBFD resource, and performs, to the second apparatus, the PRACH transmission based at least in part on the starting PRACH occasion of the set