Random Access Preamble Determination for Cell-Free Multi-AP Systems
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Solution Overview
Problem
The existing Random Access Channel (RACH) procedure is not applicable to cell-free communications systems, where the concept of a cell is obsolete, and User Equipment (UE) communicates with multiple Access Points (APs, leading to challenges in random access management without cell identifiers or inter-cell handovers.
Innovation Solution
A method for random access in cell-free communications systems, where a terminal device transmits first information with a preamble determined based on information from multiple target signals, and receives a random access response from a network device, allowing for efficient access across multiple APs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the existing RACH procedure is used in cell-free systems, then the procedure structure is maintained, but the system cannot properly handle multiple APs and lacks cell identifier management
Solution Approach 1:
The patent applies universality by making the random access procedure applicable to both traditional cellular systems and cell-free systems. The method uses multiple target signals (SSBs or CSI-RS) that can represent either cell identifiers in traditional systems or AP identifiers in cell-free systems, allowing the same RACH procedure to function in both contexts without requiring separate procedures.
Solution Approach 2:
The patent changes the parameter interpretation from cell-specific to AP-specific. By determining the preamble based on multiple target signals without relying on cell ID concepts, the system adapts the random access parameters to work in cell-free environments where multiple APs serve a UE simultaneously, resolving the contradiction between maintaining procedure structure and adapting to new system architecture.
2Productivity
If a single cell ID is used for preamble determination, then the RACH procedure is simple, but it cannot support multiple APs in cell-free systems
Solution Approach 1:
The patent merges the functions of multiple target signals into the preamble determination process. Instead of using a single cell ID, the method combines information from multiple SSBs or CSI-RS resources to determine the preamble, allowing the system to simultaneously support multiple APs while maintaining efficient random access procedures.
Solution Approach 2:
The preamble determination mechanism becomes universal by working with both single-cell and multi-AP scenarios. The method determines preambles based on multiple target signals that can represent different APs, enabling the same procedure to achieve both access efficiency and multi-AP support.
3Quantity of substance
If the UE communicates with multiple APs simultaneously, then the system capacity increases, but interference management becomes more difficult
Solution Approach 1:
The patent implements feedback through the random access response mechanism. The network device receives the preamble from the UE, determines which APs should serve the UE based on the preamble and target signal information, and provides feedback in the random access response to establish the serving AP set. This feedback mechanism enables dynamic interference management by allowing the network to optimize which APs serve each UE based on current channel conditions.
Data Source
AI summary
Random access methods, and a terminal device are provided. A random access method includes: transmitting first information used for random access. A preamble carried in the first information is determined based on information of a plurality of target signals. The random access method further includes receiving second information transmitted by a network device. The second information is a random access response for the first information.