SBFD RACH Occasion Selection Between Full-Duplex and TDD Slots
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Solution Overview
Problem
In wireless communication systems, user equipment (UE) may receive multiple PRACH configurations for subband full-duplex (SBFD) and time division duplex (TDD) slots but is unsure which to use for transmitting the first message of a random access channel (RACH) procedure.
Innovation Solution
The network entity indicates the UE to use either the SBFD PRACH configuration or the TDD PRACH configuration through control signaling, such as a PDCCH order message with a bitfield, or the UE selects based on capability or earliest available occasions, allowing multiple transmissions to enhance reliability and coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE receives multiple PRACH configurations (SBFD and TDD), then the adaptability and coverage are improved, but the device complexity and difficulty of selecting the appropriate configuration increase
Solution Approach 1:
The UE autonomously determines which PRACH configuration to use by checking whether the current slot is configured as an SBFD slot. This self-service mechanism eliminates the need for explicit network indication in every RACH trigger, reducing signaling overhead while maintaining adaptability.
Solution Approach 2:
The network pre-configures the UE with multiple PRACH configurations (SBFD and TDD) and the UE stores them for later use. When a RACH procedure is triggered, the UE already has the configurations ready and only needs to select the appropriate one based on the current slot type, reducing real-time decision complexity.
2Productivity
If the UE uses SBFD PRACH configuration, then the spectral efficiency and throughput are improved, but the reliability may deteriorate due to potential interference in full-duplex slots
Solution Approach 1:
The system dynamically selects between SBFD and TDD PRACH configurations based on the current slot type. When an SBFD slot is available, the UE uses the SBFD configuration for higher spectral efficiency. When only TDD slots are available or SBFD slots are unsuitable, the UE falls back to TDD configuration, ensuring reliability through adaptive selection.
Solution Approach 2:
The UE changes the PRACH configuration parameters (such as time resources, frequency resources, and preamble formats) depending on whether the current slot is SBFD or TDD. This parameter adaptation allows the system to optimize for spectral efficiency in SBFD slots while maintaining reliability by using proven TDD configurations when needed.
3Ease of operation
If the network provides explicit indication for PRACH configuration selection, then the ease of operation is improved, but the signaling overhead and loss of information increase
Solution Approach 1:
The UE independently determines the appropriate PRACH configuration by checking the slot configuration stored during initial access. This self-service approach eliminates the need for continuous network indications, significantly reducing signaling overhead while maintaining ease of operation through automated UE-side decision-making.
Solution Approach 2:
The patent extracts the configuration selection logic from the network side and places it at the UE side. By taking out the decision-making responsibility from the network, the system reduces uplink/downlink signaling overhead while the UE uses its stored configuration knowledge to make autonomous selection decisions.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. The described techniques may allow for a network entity to indicate to a user equipment (UE) to use a subband full-duplex (SBFD) random access channel (RACH) configuration or a time division duplex (TDD) PRACH configuration. For example, a control message (e.g., a downlink control information (DCI) or radio resource control (RRC) message) may include a bitfield that indicates which PRACH configuration for the UE to use. Additionally, or alternatively, the UE may select a PRACH configuration based on a capability of the UE to perform the SBFD PRACH configuration, or based on a PRACH configuration indicating RACH occasions that are earliest in time. Additionally, or alternatively, the PDCCH order message may indicate for the UE to transmit the first message multiple times via one or both of the SBFD PRACH configuration or the TDD PRACH configuration.