Channel Occupancy Sharing for Beam-Specific PUSCH Access
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Solution Overview
Problem
In wireless communication systems using directional LBT mechanisms, UEs lack information on whether their uplink transmission beams are within the spatial region of a channel occupancy (CO) initiated by a base station, leading to uncertainty about sharing the CO for uplink transmissions, which can cause transmission delays and reduce spatial multiplexing efficiency.
Innovation Solution
A method and apparatus for channel access that involves transmitting control information via group common-physical downlink control channels (GC-PDCCH) and medium access control-control elements (MAC-CE) to indicate whether a CO can be shared and specify the associated uplink transmission beam, allowing UEs to determine the appropriate beam for PUSCH transmissions based on this information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE performs LBT Cat4 with random back-off before uplink transmission, then the channel access reliability is improved, but the transmission delay increases
Solution Approach 1:
The patent changes the LBT category parameter from Cat4 (random back-off) to Cat2 (deterministic idle duration) by providing control information that indicates the CO can be shared. This parameter change allows the UE to switch from a probabilistic channel access method with variable delay to a deterministic method with fixed, shorter delay, thereby resolving the contradiction between reliability and delay.
Solution Approach 2:
The base station performs preliminary LBT action before initiating the channel occupancy and provides control information to the UE indicating that the CO can be shared. This preliminary action allows the UE to skip its own LBT procedure or use a simplified LBT Cat2, eliminating the need for the UE to perform time-consuming random back-off and thereby reducing transmission delay while maintaining reliable channel access.
2Reliability
If a UE performs full LBT procedure with random back-off, then the coexistence fairness on unlicensed spectrum is improved, but the spatial multiplexing efficiency deteriorates
Solution Approach 1:
The patent applies local quality by allowing different LBT behaviors in different spatial regions. The base station's downlink transmission occupies a certain spatial region, and the patent allows UEs in this region to share the CO with relaxed LBT requirements (LBT Cat2), while other regions maintain full LBT Cat4 procedures. This localized differentiation improves spatial multiplexing efficiency within the base station's spatial region while maintaining coexistence fairness in other areas.
Solution Approach 2:
The control information provided by the base station acts as an intermediary that coordinates between the base station's downlink transmission and the UE's uplink transmission. This intermediary mechanism allows the UE to determine whether it can share the CO based on the control information, enabling efficient spatial multiplexing when the UE's transmission beam is within the base station's spatial region while maintaining proper channel access control.
3Device complexity
If the CO sharing information is not provided to the UE, then the control signaling overhead is reduced, but the UE cannot determine the appropriate beam for uplink transmission
Solution Approach 1:
The patent makes the control information multi-functional by designing it to serve multiple purposes simultaneously: (1) indicating whether the CO can be shared, (2) providing the uplink transmission beam associated with the CO, and (3) enabling the UE to determine the appropriate beam for PUSCH transmission. This universal control information structure eliminates the need for separate signaling messages, thereby reducing control signaling overhead while providing complete beam determination capability.
Data Source
AI summary
Embodiments of the present application are directed to a method and apparatus for channel access. A method according to an embodiment of the present application may include: receiving control information associated with a channel occupancy (CO) initiated by a base station, determining whether the CO can be shared for a physical uplink shared channel (PUSCH) transmission and an uplink transmission beam associated with the CO in the case of being shared based on the control information, and transmitting the PUSCH transmission with the determined uplink transmission beam in the case that the CO can be shared.