HARQ Feedback Transmission in Unlicensed Cellular Networks
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Solution Overview
Problem
Existing wireless communications systems face complexity in implementing HARQ feedback for downlink data in unlicensed cells, requiring terminal devices to perform a fallback-based channel access process.
Innovation Solution
A transmission method where a network device configures a downlink transmission resource using first DCI and sends second DCI to indicate an uplink transmission resource for HARQ feedback, allowing the terminal device to perform a simplified channel access process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a terminal device performs a fallback-based channel access process to transmit HARQ feedback, then the channel can be accessed on unlicensed frequency bands, but the implementation complexity increases
Solution Approach 1:
The network device performs the fallback-based channel access process in advance before transmitting downlink data, and shares the obtained channel occupancy time (COT) with the terminal device. This preliminary action allows the terminal device to transmit HARQ feedback without performing its own complex fallback-based channel access, thereby reducing implementation complexity while maintaining unlicensed band access capability
Solution Approach 2:
The network device acts as an intermediary by performing the complex channel access process on behalf of the terminal device and sharing the COT. The network device transmits indication information to the terminal device to grant access to the uplink transmission resource within the shared COT, eliminating the need for the terminal device to independently execute the complex fallback procedure
2Reliability
If a terminal device performs fallback-based channel access for HARQ feedback, then channel access is achieved, but the processing time increases
Solution Approach 1:
The network device performs the fallback-based channel access process in advance before downlink data transmission, obtaining the COT beforehand. This preliminary action eliminates the need for the terminal device to perform time-consuming channel access procedures later, thereby reducing overall processing time while ensuring reliable channel access through the network device's prior LBT
3Adaptability or versatility
If two pieces of DCI are used to allocate downlink and uplink resources, then resource allocation flexibility improves, but signaling overhead increases
Solution Approach 1:
The second DCI transmitted by the network device serves multiple functions simultaneously: it acts as both downlink control information for resource allocation and as grant information for uplink transmission. This multi-functionality allows flexible resource allocation while avoiding the need for separate grant DCI, thereby reducing signaling overhead despite using two DCI messages
Data Source
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AI summary
This application provides a transmission method and a communications apparatus, to simplify LBT behavior before a terminal device can transmit a HARQ feedback, and reduce implementation complexity. The method includes: receiving first DCI, where the first DCI is used to indicate or activate a downlink transmission resource; receiving downlink data on the downlink transmission resource; receiving second DCI, where the second DCI is used to indicate an uplink transmission resource, and the uplink transmission resource is used to transmit feedback information for the downlink data; and sending the feedback information on the uplink transmission resource.