Random Access Method Using LBT Priority Levels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing random access methods in Licensed Assisted Access (LAA) systems face challenges due to varying time advance values between primary and secondary cells, leading to increased access delays and insufficient preambles for multiple User Equipments (UEs) to perform simultaneous random access, especially with the introduction of the listen-before-talk (LBT) mechanism which complicates the use of traditional time and frequency domain resources.
Innovation Solution
The proposed solution involves determining listen-before-talk (LBT) priority levels for messages during the random access process and configuring time and frequency domain resources through high-layer RRC signaling and physical layer DCI signaling to optimize the random access procedure, including extending the time window for receiving responses and adjusting the number of preambles available for non-contention based random access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the listen-before-talk (LBT) mechanism is introduced to the LAA system, then the random access process can be supported on the SCell, but the time domain resources and frequency domain resources of the semi-static configured physical random access channel (PRACH) are no longer applicable, increasing access delay
Solution Approach 1:
The patent applies dynamics by making the PRACH resource configuration adaptive rather than semi-static. The base station dynamically indicates PRACH time domain resources and formats through DCI signaling, allowing the system to adapt to the LBT mechanism's variable channel access conditions. This dynamic configuration enables the random access process to function properly on SCell while minimizing access delay by selecting appropriate time-frequency resources based on current channel conditions.
Solution Approach 2:
The patent changes key parameters including the PRACH time domain resource configuration, PRACH format selection, and LBT priority level assignment. By dynamically adjusting these parameters based on LBT outcomes and traffic conditions, the system resolves the contradiction between supporting random access on SCell and maintaining acceptable access delay. The LBT priority levels (1-4) are assigned to different messages and PRACH formats to optimize resource utilization.
2Ease of operation
If the timing relationship n+k (k≥6) is used for PRACH transmission after PDCCH order triggers random access on subframe n, then the random access process can be initiated, but in the dynamic uplink and downlink subframe structure, the UE may fail to wait for the coming of available PRACH resources, increasing access delay
Solution Approach 1:
The patent replaces the fixed timing relationship n+k with a dynamic resource indication mechanism. The base station uses DCI signaling to dynamically indicate the specific time domain resources for PRACH transmission, allowing the UE to access available resources without being constrained by predetermined timing relationships. This dynamic approach ensures the UE can successfully transmit preambles even in the flexible uplink-downlink subframe structure of LAA.
Solution Approach 2:
The base station performs preliminary configuration of multiple candidate PRACH time domain resources and formats, then dynamically selects and indicates the appropriate resources through DCI signaling. This preliminary preparation ensures that suitable PRACH resources are already identified and ready, reducing the time the UE needs to wait for available resources while maintaining flexibility in the dynamic subframe structure.
3Device complexity
If the number of preambles is limited in the existing art, then the system complexity is reduced, but the number of preambles available for non-contention based random access hardly meets the need of a scenario where multiple UEs simultaneously need to randomly access
Solution Approach 1:
The patent segments the total preamble space by introducing LBT priority levels (1-4) that partition preambles into different groups. Each priority level can have dedicated preambles or share the preamble space with specific access rights. This segmentation allows multiple UEs with different service requirements to simultaneously perform random access with appropriate priority handling, increasing simultaneous access capability while maintaining manageable complexity through structured organization.
Solution Approach 2:
The patent makes the preamble resource configuration universal by allowing the same PRACH resources to serve multiple purposes through dynamic configuration. The base station can flexibly allocate preambles for different priority levels, contention-based and non-contention-based random access, and different service types using the same physical resources. This multi-functionality increases the system's capacity to handle simultaneous random access from multiple UEs without requiring proportionally more physical resources.
Data Source
AI summary
Provided are a random access method and device, a user equipment and a storage medium. The method includes: determining listen-before-talk (LBT) priority levels for performing an LBT mechanism corresponding to messages transmitted during a random access process, and/or LBT priority levels of an LBT mechanism corresponding to different physical random access channel (PRACH) formats; and transmitting the messages for random access by means of the determined LBT priority levels corresponding to the messages and/or LBT priority levels corresponding to different PRACH formats after successfully performing the LBT mechanism. In such a way, the problem of the need of optimizing random access for a user equipment in the related art is resolved, thereby optimizing random access and improving the random access success rate.