Terminal Device LBT Switching for Shared Spectrum Access
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Solution Overview
Problem
LTE systems are not optimized for use in non-allocated or shared frequency bands, leading to inefficiencies in communication due to design assumptions based on allocated and non-shared frequency bands.
Innovation Solution
A terminal device equipped with a reception unit for receiving PDCCH, a transmission unit for transmitting PUSCH, and a CCA check unit that performs either first LBT for multiple CCA checks based on a random number or second LBT for a single CCA check, switching between these methods based on specific conditions to manage channel access efficiently in shared frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LTE systems use traditional channel access methods designed for allocated frequency bands, then system design is simplified, but transmission efficiency deteriorates in non-allocated or shared frequency bands
Solution Approach 1:
The patent implements dynamic channel access by switching between two LBT methods (first LBT with multiple CCA checks and second LBT with single CCA check) based on channel conditions and traffic requirements. This dynamic adaptation allows the system to optimize transmission efficiency in shared frequency bands while maintaining manageable complexity through structured decision-making
Solution Approach 2:
The patent changes the parameter of CCA check count from fixed to variable. By adjusting the number of CCA checks based on channel occupancy conditions, traffic priority, and QoS requirements, the system adapts to shared spectrum environments while maintaining design simplicity through parameterization rather than structural complexity
2Reliability
If multiple CCA checks are performed based on random number (first LBT), then channel access reliability is improved, but transmission delay increases
Solution Approach 1:
The patent applies partial action by performing only the necessary number of CCA checks rather than always performing maximum checks. Based on channel conditions and traffic priority, the system performs one CCA check for high-priority traffic or when channel is clear, reducing delay while maintaining reliability through selective application of multiple checks when needed
3Loss of time
If single CCA check is performed (second LBT), then transmission delay is reduced, but channel access reliability deteriorates
Solution Approach 1:
The patent changes the reliability parameter dynamically by adjusting the number of CCA checks based on traffic priority, QoS requirements, and channel conditions. For high-priority traffic or uncertain channel conditions, the system increases CCA check count to maintain reliability, while for low-priority traffic with clear channels, it reduces checks to minimize delay
4Device complexity
If LTE assumes non-shared frequency band usage, then channel access control is simplified, but spectrum utilization efficiency worsens in shared bands
Solution Approach 1:
The patent implements dynamic channel access control that adapts to shared spectrum conditions through LBT procedures. The system monitors channel occupancy and dynamically adjusts access behavior, maintaining manageable complexity through standardized LBT frameworks while significantly improving spectrum utilization efficiency in shared bands compared to static assumptions
Solution Approach 2:
The patent incorporates feedback mechanisms where the terminal device monitors channel conditions and adjusts its LBT behavior accordingly. The base station provides guidance on appropriate LBT methods based on observed channel conditions and traffic patterns, creating a feedback loop that optimizes spectrum utilization while maintaining control complexity at manageable levels
Data Source
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AI summary
To efficiently control a cell by using a non-allocated frequency band or a shared frequency band. The terminal device includes a reception unit configured to receive a PDCCH, a transmission unit configured to transmit a PUSCH in a serving cell, and a CCA check unit configured to perform either first LBT for performing a CCA check a number of times based on a random number before a subframe for which a transmission of the PUSCH is indicated or second LBT for performing a CCA check only once. The terminal device switches between the first LBT and the second LBT, based on a prescribed condition.