Dual BWP Inactivity Timer for Unlicensed Spectrum Latency
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Solution Overview
Problem
In 3GPP new radio (NR) communication systems, bandwidth part (BWP) inactivity timers can lead to premature switching from wide to narrow BWP, causing undesirable latency and throughput degradation due to unreliable channel access indications, especially in unlicensed spectrum where base station inactivity is not a reliable indicator of no data transmission.
Innovation Solution
Implementing a dual countdown timer system, where a channel occupancy time (COT) timer and an inactivity timer are adjusted based on reception of group common physical downlink control channel (GC-PDCCH) signals, allowing for more accurate assessment of channel availability and reducing unnecessary BWP switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single BWP inactivity timer is used to switch from wide BWP to narrow BWP, then power consumption is reduced when no data is transmitted, but channel access reliability deteriorates in unlicensed spectrum due to premature switching
Solution Approach 1:
The patent divides the single BWP inactivity timer into two separate timers: a first BWP inactivity timer for monitoring data transmission activity and a second BWP inactivity timer for monitoring channel access status. This segmentation allows independent control of data transmission monitoring and channel access assessment, preventing premature BWP switching when channel is busy while still enabling power savings when channel is clear and no data is transmitted.
Solution Approach 2:
The patent introduces a channel occupancy time indicator as an intermediary signal that provides explicit information about channel access status. This indicator acts as a mediator between the base station's channel access state and the UE's BWP switching decision, allowing the UE to accurately determine whether the base station is contending for the channel without relying solely on timer expiration, thus preventing premature switching.
2Productivity
If BWP switching is triggered by inactivity timer expiration, then throughput is improved by using narrow BWP for power saving, but latency increases due to premature switching from wide BWP
Solution Approach 1:
By segmenting the inactivity timer into two separate timers with distinct functions, the patent enables more precise control over BWP switching timing. The first timer tracks data transmission activity while the second timer tracks channel access status, allowing the system to maintain wide BWP longer when channel contention is detected, thereby reducing premature switching latency while still achieving throughput optimization through timely switching when appropriate.
Solution Approach 2:
The patent implements preliminary assessment of channel access status using the second BWP inactivity timer and channel occupancy time indicator before triggering BWP switching. This preliminary action allows the system to determine in advance whether the base station is contending for the channel, preventing premature switching and the associated latency while still enabling timely switching when the channel is clear.
3Device complexity
If base station inactivity is used as indicator for BWP switching, then device complexity is reduced with simple timer mechanism, but measurement precision deteriorates due to unreliable channel access indication in unlicensed spectrum
Solution Approach 1:
The patent segments the timer mechanism into two specialized timers with distinct monitoring functions, improving measurement precision without significantly increasing overall complexity. Each timer has a specific role: one for data transmission monitoring and another for channel access status, allowing more accurate assessment of base station activity in unlicensed spectrum while maintaining manageable device complexity through modular timer management.
Solution Approach 2:
The channel occupancy time indicator serves as an intermediary that provides precise channel access status information to the UE. This indicator bridges the gap between the base station's channel access state and the UE's measurement capability, enabling accurate detection of base station channel contention without requiring complex measurement mechanisms at the UE side.
Data Source
AI summary
According to a first embodiment, a method may include initiating, by a user equipment, a first countdown timer associated with a first initial value and a first timer-interval, and a second countdown timer associated with a second initial value and a second timer-interval. The method may further include determining, by the user equipment, whether at least one first indication is detected during the first timer-interval. The method may further include adjusting, by the user equipment, at least one of the first countdown timer or the second countdown timer based on the determining.