Unlicensed Spectrum Switching After Persistent LBT Failures
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Solution Overview
Problem
Challenges exist in handling persistent failures in unlicensed frequency spectrum, particularly in managing consistent listen-before-talk failures and channel occupancy issues, which lead to increased latency and inefficiencies in wireless communication systems.
Innovation Solution
A wireless device detects consistent listen-before-talk failures through timers and counters, and upon detection, switches to a different channel or frequency band, either autonomously or with network node intervention, to mitigate these failures, employing mechanisms like carrier aggregation and supplementary uplink carriers to minimize the impact of LBT failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transmitter performs channel sensing and backoff in unlicensed frequency spectrum, then spectrum sharing and coexistence are improved, but latency increases due to persistent LBT failures
Solution Approach 1:
The system changes parameters such as switching from one unlicensed carrier to another unlicensed carrier, or from unlicensed to licensed spectrum, when LBT failure is detected. This parameter change enables the system to adapt to changing spectrum conditions and reduce latency caused by persistent backoff, while maintaining the benefits of unlicensed spectrum exploitation when conditions are favorable.
Solution Approach 2:
The patent implements dynamic spectrum access by enabling the transmitter to transition between different spectrum types (unlicensed to licensed or between unlicensed carriers) based on real-time channel conditions. This dynamic approach allows the system to optimize between spectrum sharing efficiency and latency performance by adapting to current spectrum availability.
2Productivity
If a transmitter continuously attempts to clear unlicensed spectrum through backoff, then spectrum utilization is improved, but system performance deteriorates due to persistent failures
Solution Approach 1:
The system performs preliminary actions by detecting LBT failures and triggering spectrum switching before communication reliability severely deteriorates. The method proactively monitors channel access success and initiates carrier or spectrum type changes when failure thresholds are reached, preventing complete communication breakdown while maintaining efficient spectrum utilization.
Solution Approach 2:
The patent introduces an intermediary mechanism (spectrum switching capability) that mediates between the need for continuous spectrum utilization and the need to maintain communication reliability. When unlicensed spectrum becomes unreliable, the system transitions to licensed spectrum or alternative unlicensed carriers, ensuring continuous operation without complete dependency on a single spectrum type.
3Loss of time
If the system switches between licensed and unlicensed spectrum, then latency is reduced, but device complexity increases
Solution Approach 1:
The patent segments the spectrum access function into distinct unlicensed and licensed spectrum operations, with clear criteria for when to switch between them. This segmentation allows the system to maintain simple, efficient operations within each spectrum type while enabling controlled transitions between them, reducing the overall complexity compared to managing a single complex unified spectrum access mechanism.
Data Source
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AI summary
A wireless device (12) detects a problem on a channel, subband, bandwidth part, carrier, cell, or frequency band (18) deployed within unlicensed frequency spectrum. The problem may, for example, be that a measure of channel occupancy within and/or clear channel assessment failure within the channel, subband, bandwidth part, carrier, cell, or frequency band (18) exceeds an occupancy or failure threshold. Responsive to detecting the problem, the wireless device (12) switches to, or requests a switch to, a different channel, subband, bandwidth part, carrier, cell, or frequency band (20). In some embodiments, the wireless device (12) requests the switch by transmitting, to a network node (16), a problem report that reports the detected problem. Based on the report, the network node (16) may switch the wireless device (12) to the different channel, subband, bandwidth part, carrier, cell, or frequency band (20).