eLAA Uplink Channel Access via eNB-Assisted LBT Priority
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Solution Overview
Problem
In eLAA-based communication systems, the existing methods for uplink channel access lack clear mechanisms for determining channel access parameters and contention window size at the User Equipment (UE) side, leading to inefficiencies in spectrum usage and reliability issues due to the absence of explicit HARQ-ACK feedback and varying UE priorities.
Innovation Solution
The eNB determines and communicates channel access parameters and contention window sizes to the UE through Layer 1 signaling, considering factors like transmission duration, number of UEs, traffic types, and interference, allowing the UE to adjust LBT priorities and maximize channel occupancy, and dynamically updates contention window sizes based on PUSCH decoding results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the UE determines channel access parameters autonomously based on local conditions, then the response speed is improved, but the reliability of HARQ-ACK feedback deteriorates due to lack of explicit feedback
Solution Approach 1:
The eNB acts as an intermediary that provides reference signals (CSI-RS or PSSCH) to enable the UE to determine channel access parameters autonomously. This mediator approach allows the UE to make local decisions while the eNB maintains overall control and provides reliable feedback mechanisms through the scheduled reference signals.
2Productivity
If the eNB schedules a large number of continuous subframes for a UE with high priority parameters, then the spectrum efficiency is improved, but the system must handle the complexity of MCOT management and potential transmission interruptions
Solution Approach 1:
The eNB pre-configures the UE with channel access parameters, contention window sizes, and MCOT information before the actual transmission. This preliminary configuration allows the UE to autonomously manage the transmission burst without continuous eNB intervention, reducing signaling overhead and management complexity while maintaining high spectrum efficiency.
3Reliability
If the UE performs LBT with low priority parameters for short scheduled subframes, then the coexistence fairness is improved, but the spectrum efficiency deteriorates due to long competition time
Solution Approach 1:
The system dynamically adjusts the channel access parameters and contention window sizes based on the scheduled transmission characteristics. For short subframes, the eNB configures appropriate CWS values that balance coexistence fairness with acceptable access delay, while for longer transmissions, more aggressive parameters are allowed to improve spectrum efficiency. This dynamic adaptation resolves the contradiction between fairness and efficiency.
4Adaptability or versatility
If multiple UEs perform LBT procedures simultaneously in the LBT gap with different CWS values, then the system supports multi-user multiplexing, but the probability of successful multiplexing decreases
Solution Approach 1:
The eNB assigns different channel access parameters and contention window sizes to different UEs based on their specific transmission requirements, channel conditions, and priority levels. This localized parameter assignment allows the system to support diverse multi-user scenarios while optimizing the multiplexing success probability for each user group, resolving the contradiction between versatility and productivity.
Data Source
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AI summary
The disclosure provides a method for assisting a UE to implement a UL channel access in a base station of an eLAA-based communication system. The method comprises determining a listen-before-talk (LBT) priority for the UE; and transmitting a first signaling indicating the determined LBT priority to the UE. An enhanced UL channel access mechanism is proposed by the disclosure. In this mechanism, the eNB can provide some assistance to facilitate UL access. Chances of multiple user multiplexing and spectrum efficiency in LAA UL can be improved by this solution.