Uplink Bandwidth Part Switching in NR-U
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Solution Overview
Problem
Current NR-U wideband operation faces challenges in efficient BWP switching times, which are longer than LBT procedures, leading to potential channel access loss and interference issues, especially in unlicensed bands like 5 GHz, where regulatory requirements demand sub-band LBT support and flexible channel access.
Innovation Solution
Implementing dynamic BWP switching mechanisms that allow gNB to adjust transmission bandwidth based on LBT results, with explicit or implicit indications for UE to perform BWP switching during DL bursts, ensuring minimal disruption and interference avoidance, and using RF chains for agile channel access and interference management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic BWP switching is implemented to enable flexible bandwidth adaptation, then channel access efficiency and adaptability are improved, but BWP switching time becomes longer than LBT procedure time, causing potential channel access loss
Solution Approach 1:
The gNB performs BWP switching preparation in advance by configuring multiple BWPs and pre-establishing switching parameters. The UE is pre-configured with BWP switching indicators and timing information, allowing rapid switching without lengthy procedures when channel access is needed.
Solution Approach 2:
The system implements dynamic BWP switching where the active bandwidth part can be changed based on real-time channel conditions and LBT results. The gNB can dynamically switch between different BWPs (e.g., from narrow to wide bandwidth) depending on available spectrum and interference conditions, making the system adaptable while controlling switching time.
2Productivity
If wideband operation is implemented to increase throughput capacity, then productivity is improved, but interference with other systems increases due to broader channel occupancy
Solution Approach 1:
The wide bandwidth is divided into multiple smaller bandwidth parts (BWPs). Instead of always occupying the full wide band, the system can segment the channel and activate only the necessary portions based on LBT results and interference conditions, reducing overall interference while maintaining high throughput when needed.
Solution Approach 2:
The system changes the operational bandwidth parameter dynamically. The gNB can adjust the active BWP width based on real-time measurements of channel conditions, interference levels, and regulatory requirements, allowing the system to operate at wide bandwidth for high throughput when interference is low, and narrow bandwidth when interference is high.
3Adaptability or versatility
If BWP switching is performed to adapt to changing channel conditions, then adaptability is improved, but device complexity increases due to multiple RF chains and configuration management
Solution Approach 1:
The RF chain is designed to be universal and can operate across multiple bandwidth parts without requiring separate dedicated RF chains for each BWP. The same RF chain can be reconfigured to handle different BWPs through software-controlled parameter changes, reducing hardware complexity while maintaining adaptability.
Solution Approach 2:
Instead of having separate RF chains for each BWP, the system uses a single RF chain that copies the functionality of multiple BWPs through software configuration. The gNB and UE maintain multiple BWP configurations in memory and switch between them by loading appropriate parameters, avoiding the need for physical duplicate RF hardware.
Data Source
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Figure 3
Figure 4A~4B
AI summary
In accordance with an example embodiment o f the invention there is at least a method and apparatus to perform determining, by a network node, that at least one of frequency tuning, bandwidth part switching, or bandwidth switching is to be performed by at least one user equipment; and based on the determining, sending, by the network node, to the at least one user equipment one or more downlink slots, wherein the one or more downlink slots provide an indication of a time to perform the at least one of frequency toning, bandwidth part switching, or bandwidth switching by the at least one user equipment. Further, in accordance with another example embodiment of the invention there is at least a method and apparatus to perform receiving from a network node, by a user equipment, one or more downlink slots, wherein the one or more downlink slots comprises at least one of an uplink grant, a downlink assignment, and wherein the one or more downlink slots provide an indication of a time to perform at least one of a frequency tuning, bandwidth part switching, and bandwidth switching by at least one user equipment; based on the one or more downlink slots, performing, by the user equipment, the at least one of frequency tuning, bandwidth part switching, or bandwidth switching, and transmitting, by the user equipment, at least one uplink channel or a signal via a radio frequency chain based on the at least one of frequency tuning, bandwidth part switching, or bandwidth switching.