PRACH Gap Configuration for High-SCS RACH Occasions
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Solution Overview
Problem
In high carrier frequency wireless communication systems like 5G NR, the increased channel bandwidth and higher subcarrier spacing lead to shorter RACH slot durations and cyclic prefixes, necessitating a novel approach to manage gaps between RACH occasions to support processes such as LBT and beam switching.
Innovation Solution
A wireless communication device determines the presence and length of gaps between RACH occasions based on subcarrier spacing, RO duration, number of ROs, or predefined values, using signaling like DCI or RRC, to ensure efficient configuration and avoid RO straddling across slots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If higher subcarrier spacing is used in high carrier frequency systems, then channel bandwidth and data transmission capability are improved, but RACH slot duration and cyclic prefix length become shorter, making it difficult to accommodate necessary processing gaps
Solution Approach 1:
The patent applies dynamics by making the gap configuration flexible and adaptive rather than fixed. The network device dynamically determines gap presence and length based on actual system conditions including subcarrier spacing, RO duration, and number of ROs. This allows the RACH configuration to adapt to different carrier frequencies and bandwidths, resolving the contradiction between high transmission speed and sufficient processing time.
Solution Approach 2:
The patent changes multiple parameters simultaneously to resolve the contradiction: subcarrier spacing (higher for speed), gap length (adjusted to provide necessary processing time), RO duration (modified based on subcarrier spacing), and number of ROs (adjusted to fit within available time). By coordinating changes across these parameters, the system achieves high data transmission capability while maintaining adequate RACH slot duration for processing.
2Quantity of substance
If multiple RACH occasions are configured in a PRACH slot, then random access capacity is improved, but the risk of RACH occasions straddling across slot boundaries increases, causing interference
Solution Approach 1:
The patent applies preliminary action by having the network device pre-determine and configure gap positions and lengths before RACH occasions are transmitted. The network device calculates the optimal number of ROs that can fit within the PRACH slot boundaries, considering the required gaps, and configures this information in advance through RRC signaling or DCI format 0_0. This prevents RO straddling by establishing proper boundaries before transmission occurs.
Solution Approach 2:
The patent uses feedback mechanisms where the network device monitors RACH occasion configurations and adjusts gap lengths and RO positions based on system performance. The network device can reconfigure RACH parameters through subsequent signaling if boundary alignment issues are detected, ensuring reliable operation while maintaining high random access capacity.
3Reliability
If gap length is increased to prevent RO straddling, then boundary alignment reliability is improved, but the available time for random access transmissions is reduced
Solution Approach 1:
The patent makes gap length dynamic rather than fixed, adjusting it based on the specific configuration needs. The network device determines the minimum necessary gap length to prevent RO straddling, rather than using a conservative fixed value. This dynamic adjustment optimizes the balance between boundary alignment reliability and available transmission time, allowing more ROs to be accommodated when possible.
Solution Approach 2:
The patent coordinates changes in multiple parameters: gap length is adjusted based on subcarrier spacing and RO duration, while the number of ROs is simultaneously optimized to maximize utilization of available time. By changing these parameters together rather than independently, the system achieves proper boundary alignment while minimizing time loss.
Data Source
AI summary
Presented are systems and methods for calculating and configuring a random access channel (RACH). A wireless communication device may determine whether a gap is to be present between a pair of adjacent random access channel (RACH) occasions (ROs), for a subcarrier spacing (SCS) of a physical RACH (PRACH) slot that is higher than 120 kiloHertz (KHz) or 60 KHz. The wireless communication device may determine a length of the gap, if the gap is to be present.