PUCCH Transmission on Unlicensed Carrier After CCA Failure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, especially in License Assisted Access (LAA), the failure of clear channel assessment (CCA) for unlicensed carriers can lead to issues such as suspended or terminated Hybrid Automatic Repeat Request (HARQ) processes, outdated Channel State Information (CSI) for scheduling, and increased contention window sizes, affecting the transmission of uplink control information (PUCCH) on unlicensed Secondary Component Carriers (SCC).
Innovation Solution
The solution enables the transmission of PUCCH on unlicensed SCC even when CCA fails, by reserving PUCCH resources in subframes of unlicensed carriers, allowing for fallback to licensed carriers, and dynamically adjusting payload distribution across multiple carriers to ensure continuous ACK/NACK feedback and prevent HARQ suspension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PUCCH transmission is performed on unlicensed carrier, then spectral efficiency and capacity are improved, but transmission reliability deteriorates due to CCA failure
Solution Approach 1:
The system dynamically changes the carrier parameter from unlicensed to licensed based on CCA status. When CCA fails on the unlicensed carrier, the PUCCH transmission parameter is switched to use the licensed carrier instead, maintaining transmission reliability while preserving the ability to use unlicensed carriers for capacity enhancement when conditions permit.
2Quantity of substance
If PUCCH transmission is performed on unlicensed carrier, then control information capacity is increased, but system stability deteriorates due to HARQ suspension
Solution Approach 1:
The system performs a CCA check as a preliminary action before attempting PUCCH transmission on the unlicensed carrier. This proactive channel assessment prevents transmission attempts that would fail, thereby avoiding HARQ suspension and maintaining system stability while still enabling high-capacity control information transmission when the channel is clear.
3Ease of operation
If CCA failure occurs on unlicensed carrier, then channel access is blocked, but this causes outdated CSI for scheduling
Solution Approach 1:
The licensed carrier acts as an intermediary for PUCCH transmission when the unlicensed carrier is inaccessible due to CCA failure. This intermediary path ensures that control information including CSI feedback continues to flow reliably, preventing information loss and maintaining accurate scheduling decisions at the eNB.
4Reliability
If PUCCH is always transmitted on licensed carriers, then transmission reliability is maintained, but overhead of licensed carrier increases
Solution Approach 1:
The system implements dynamic carrier selection for PUCCH transmission, switching between licensed and unlicensed carriers based on CCA outcomes and transmission needs. This dynamic approach allows the system to use unlicensed carriers for capacity-intensive transmissions when available, reducing licensed carrier overhead, while falling back to licensed carriers for reliability-critical transmissions when needed.
Data Source
Figure 1
Figure 2A~2D
Figure 3
AI summary
Uplink control information may not be transmitted if a CCA of the unlicensed SCC fails. Thus, the present disclosure provide a solution in which uplink control information for an unlicensed SCC may still be transmitted when a CCA of the unlicensed SCC fails. In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus generates uplink control information. The apparatus also attempts to perform a CCA of a carrier for an uplink burst. In addition, the apparatus determines a failure of the CCA. In addition, the apparatus performs one of the following when it is determined that the CCA has failed: transmitting the PUCCH transmission on the carrier in a later subframe of the uplink burst, transmitting the PUCCH transmission on the carrier in a different uplink burst, or transmitting the PUCCH transmission on a different carrier.