Full-Duplex Listen-Before-Talk Channel Access in Unlicensed Spectrum
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Solution Overview
Problem
In wireless communication systems, especially in unlicensed radio frequency spectrum, full-duplex devices face challenges in performing channel access procedures due to interference from downlink transmissions, leading to inefficient resource utilization and increased latency.
Innovation Solution
Configuring user equipment (UE) with specific zero-power reference signal (ZP-RS) or reserved resources for channel access, allowing it to perform channel access procedures without expecting downlink transmissions, thereby avoiding interference and enabling efficient uplink transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full-duplex devices perform channel access procedures in shared spectrum, then uplink transmission capability is improved, but interference from downlink transmissions causes reliability degradation
Solution Approach 1:
The shared spectrum resources are segmented into dedicated channel access resources for uplink transmissions, separated from downlink transmission resources. This segmentation allows UEs to perform channel access procedures in protected resource portions where downlink transmissions are muted, eliminating interference while maintaining uplink productivity
Solution Approach 2:
ZP-RS resources serve as an intermediary mechanism between downlink and uplink transmissions. By introducing these zero-power reference signal resources, the system creates a protected intermediate zone where UEs can safely perform channel access without exposure to downlink interference, thereby improving both reliability and maintaining productivity
2Productivity
If channel access procedures are performed in shared spectrum, then resource utilization is improved, but latency increases due to interference and retransmissions
Solution Approach 1:
The system performs preliminary configuration of channel access resources through RRC signaling and dynamic activation through MAC-CE or DCI. This preliminary setup ensures that when UEs need to access the channel, the resources are already prepared and protected from downlink interference, eliminating delays caused by ad-hoc resource negotiation and reducing access latency
Solution Approach 2:
The channel access resources are dynamically activated and deactivated based on traffic conditions through MAC-CE or DCI signaling. This dynamic adaptation allows the system to optimize resource utilization in real-time while maintaining low latency by quickly activating resources when uplink traffic is detected, without waiting for static configuration cycles
Data Source
AI summary
Methods, systems, and devices for wireless communication are described. A communication device, which may be known as user equipment (UE), may determine a set of resources for a channel access procedure (e.g. a listen-before-talk (LBT) operation) in a shared radio frequency spectrum band. The set of resources may include one or more zero-power reference signal (ZP-RS) resources, one or more reserved channel access resources, or both. The UE may perform, while operating in a full duplex mode and during a duration in which the UE has not been scheduled to receive any downlink transmission, the channel access procedure on the set of resources for a channel in the shared radio frequency spectrum band. Based on the result of the channel access procedure, the UE may transmit an uplink transmission over the channel.